阅读说明：本技术 用于检查样本的方法和设备 (Method and apparatus for inspecting a sample ) 是由 库普雷特·辛格·维迪 伯纳德·G·穆勒 于 2018-04-18 设计创作，主要内容包括：描述一种检查样本(10)的方法,所述样本具有多层结构(15),所述多层结构具有布置于第二层(12)的上方的第一层(11)。所述方法包括：将所述样本布置于真空腔室中；将主电子束(20)导引到所述样本(10)上,使得所述主电子束的第一主电子由所述第一层(11)背向散射,以形成第一背向散射电子(21),并且所述主电子束的第二主电子由所述第二层(12)背向散射,以形成第二背向散射电子(22)；以及检测信号电子来用于取得关于所述第一层(11)和所述第二层(12)两者的空间信息,所述信号电子包括所述第一背向散射电子(21)和所述第二背向散射电子(22)。此外,描述一种包括一个或多个电子显微镜来检查样本(10)的设备,所述样本(10)包括多层结构(15)。(A method of inspecting a sample (10) is described, the sample having a multilayer structure (15) with a first layer (11) arranged above a second layer (12). The method comprises the following steps: arranging the sample in a vacuum chamber; directing primary electron beams (20) onto the sample (10) such that first primary electrons of the primary electron beams are backscattered by the first layer (11) to form first backscattered electrons (21) and second primary electrons of the primary electron beams are backscattered by the second layer (12) to form second backscattered electrons (22); and detecting signal electrons for deriving spatial information about both the first layer (11) and the second layer (12), the signal electrons comprising the first backscattered electrons (21) and the second backscattered electrons (22). Furthermore, an apparatus is described comprising one or more electron microscopes for examining a sample (10), the sample (10) comprising a multilayer structure (15).)

1. A method of inspecting a sample (10), the sample having a multilayer structure (15), the multilayer structure (15) having a first layer (11), the first layer (11) being arranged above a second layer (12), the method comprising:

arranging the sample in a vacuum chamber;

directing primary electron beams (20) onto the sample (10) such that first primary electrons of the primary electron beams are backscattered by the first layer (11) to form first backscattered electrons (21) and second primary electrons of the primary electron beams are backscattered by the second layer (12) to form second backscattered electrons (22); and

detecting signal electrons for deriving spatial information about both the first layer (11) and the second layer (12), the signal electrons comprising the first backscattered electrons (21) and the second backscattered electrons (22).

2. The method of claim 1, further comprising at least one of:

-generating an image of the multilayer structure (15) based on the detected signal electrons;

-inspecting said first layer (11) and said second layer (12);

-inspecting, analyzing or identifying defects of at least one of said first layer (11) and said second layer (12);

measuring a distance or dimension of at least one of the first layer (11) and the second layer (12); and

an overlay measurement is performed.

3. The method of claim 1 or 2, wherein the multilayer structure (15) has three or more layers arranged at least partially on top of each other, wherein the respective primary electrons of the primary electron beam (20) are scattered by each of the three or more layers and subsequently detected for deriving spatial information about each of the three or more layers.

4. The method of any of claims 1 to 3, wherein the sample (10) comprises a large area substrate for display manufacturing, in particular the large area substrate having at least 1m²The size of (c).

5. The method of any of claims 1 to 4, wherein the multilayer structure (15) comprises a plurality of multilayer electronic or optoelectronic devices.

6. The method of any of claims 1 to 5, wherein the multilayer structure (15) comprises a multilayer feature having a non-linear or curved edge, wherein the non-linear or curved edge is imaged or inspected.

7. The method according to any one of claims 1 to 6, wherein the multilayer structure (15) comprises a passivation layer, and wherein at least one of the first layer (11) and the second layer (12) is arranged below the passivation layer.

8. The method of any of claims 1 to 7, wherein the first layer (11) comprises a first material having a first atomic number, the first material having a first electron backscattering capability, and the second layer (12) comprises a second material having a second atomic number, the second material having a second electron backscattering capability, the method further comprising:

based on the detected signal electrons, an image is generated in which holes, openings, steps, grooves, overlapping portions, and/or undercuts of at least one of the first layer and the second layer are respectively displayed as areas of a certain brightness in the image.

9. The method of any of claims 1 to 8, wherein the primary electron beam (20) impinges the sample with a landing energy of 5keV or more, in particular 10keV or more.

10. The method of any of claims 1 to 9, wherein the first layer (11) comprises a first material having a first atomic number, and wherein a material residue arranged below the first layer is identified, the material residue comprising a second material having a second atomic number.

11. The method of any of claims 1 to 10, comprising scanning a region of the sample (10) with the primary electron beam (20) at a single time and generating an image of the region based on the signal electrons detected during the scanning.

12. The method of any of claims 1 to 11, further comprising suppressing electrons emitted from the sample (10), the electrons having an electron energy below an energy threshold.

13. The method according to any of claims 1 to 12, comprising detecting the first backscattered electrons (21) and the second backscattered electrons (22) with an in-column detector (136), the in-column detector (136) comprising a detection opening (137) for guiding the primary electron beam (20) through the detection opening (137).

14. An apparatus (100) for inspecting a sample (10), the sample having a multilayer structure with a first layer arranged above a second layer, the apparatus comprising:

a vacuum chamber (101);

a sample support (150) arranged in the vacuum chamber, wherein the sample support is configured to support the sample; and

an electron microscope (200) configured to direct a primary electron beam (20) towards the sample such that first primary electrons of the primary electron beam are backscattered by the first layer to form first backscattered electrons and second primary electrons of the primary electron beam are backscattered by the second layer to form second backscattered electrons;

wherein the electron microscope (200) comprises: a detection device (130) configured to detect signal electrons, the signal electrons comprising the first backscattered electrons and the second backscattered electrons; and a signal processing device (160) configured to generate an image containing information about both the first layer and the second layer.

15. The apparatus of claim 14, wherein the sample support (150) is configured to support a large area substrate for display manufacturing, in particular having 1m²Or more.

16. The apparatus of claim 14 or 15, further comprising a filter electrode (154) located between the sample support (150) and the detection device (130), wherein the filter electrode (154) is configured to suppress low energy electrons.

17. The apparatus of claim 16, wherein the filtering electrode (154) is configured to be set at a negative potential greater than 50V for suppressing secondary electrons.

18. The apparatus of any of claims 14 to 17, wherein the detection device (130) comprises an in-column detector (136) having an opening (137) for the primary electron beam (20).

19. The apparatus of any of claims 14 to 18, wherein the electron microscope (200) further comprises:

an electron source (112) configured to generate the primary electron beam; and

an objective lens (140) configured to focus the primary electron beam (20) onto the sample (10) with a landing energy of 10keV or more.

20. An apparatus (300) for inspecting a sample (10), the sample (10) having a multilayer structure with a first layer arranged above a second layer, the apparatus comprising:

a vacuum chamber (101);

a sample support (150) arranged in the vacuum chamber, wherein the sample support is configured to support the sample; and

a plurality of electron microscopes (310) for simultaneous inspection of multiple regions of the sample;

wherein each electron microscope is configured to direct a primary electron beam towards the sample such that first primary electrons of the primary electron beam are backscattered by the first layer to form first backscattered electrons and second primary electrons of the primary electron beam are backscattered by the second layer to form second backscattered electrons, and each electron microscope comprises a detection device (130) configured to detect signal electrons, the signal electrons comprising the first backscattered electrons and the second backscattered electrons,

the apparatus further comprises signal processing means (160) configured to generate an image containing information about both the first layer and the second layer.

Technical Field

The present disclosure relates to a method for inspecting a sample having a multilayer structure, in particular a large area substrate for display manufacturing. More particularly, embodiments described herein relate to methods and apparatus for inspecting a sample, particularly for at least one of imaging, inspection and inspection of defects of a sample, the sample having a multilayer structure with a first layer disposed at least partially over a second layer.

Background

In many applications, a thin layer is deposited on a substrate, for example on a glass substrate. Substrates are conventionally coated in a vacuum chamber of a coating apparatus. For some applications, the substrate is coated in a vacuum chamber using vapor deposition techniques. Over the past years, electronic devices and particularly optoelectronic devices have greatly decreased in price. In addition, pixel density in displays has increased. For Thin Film Transistor (TFT) displays, high density TFT integration is advantageous. Despite the increased number of thin-film transistors (TFTs) in the device, yield will still increase and manufacturing costs will still further decrease.

Generally, a plurality of layers are deposited on a substrate, such as a glass substrate, to form an array of electronic or optoelectronic devices, such as TFTs, on the substrate. A substrate having a multilayer structure such as a plurality of TFTs formed thereon is also referred to as a "sample" herein.

For the manufacture of TFT displays and other multi-layer structures, it is advantageous to inspect the deposited layers to monitor the quality of the sample, in particular the deposited multi-layer structure.

The inspection of the substrate may for example be performed by an optical system. However, the size of some features of the multilayer structure and the size of the defects to be identified may be below the optical resolution, leaving some defects unresolvable to the optical system (non-resolvable). Inspection of small portions of a sample has also been performed using charged particle beam devices (charged particle beam devices), such as electron microscopes. However, typically only the surface of the sample can be examined using a conventional electron microscope.

Therefore, in view of the increasing demand for improving the quality of displays on large area substrates, improved methods for rapidly and reliably inspecting samples having a multilayer structure are needed.

Disclosure of Invention

According to embodiments, a method of inspecting a sample having a multilayer structure and an apparatus for inspecting a sample having a multilayer structure are provided. Other aspects, advantages, and features of the present disclosure will become apparent from the claims, the description, and the accompanying drawings.

According to one embodiment, a method of inspecting a sample is provided, the sample having a multilayer structure with a first layer disposed above a second layer. The method comprises the following steps: arranging the sample in a vacuum chamber; directing the primary electron beam onto the sample such that first primary electrons of the primary electron beam are backscattered by the first layer to form first backscattered electrons and second primary electrons of the primary electron beam are backscattered by the second layer to form second backscattered electrons; and detecting signal electrons for deriving spatial information about both the first layer and the second layer, the signal electrons comprising first backscattered electrons and second backscattered electrons.

In some embodiments, an image is generated that provides spatial information about both the first layer and the second layer based on the detected signal electrons.

According to another embodiment, a device for examining a sample is proposed, the sample having a multilayer structure with a first layer arranged above a second layer. The apparatus comprises: a vacuum chamber; a sample support arranged in the vacuum chamber, wherein the sample support is configured to support a sample; and an electron microscope configured to direct the primary electron beam towards the sample such that first primary electrons of the primary electron beam are backscattered by the first layer to form first backscattered electrons and second primary electrons of the primary electron beam are backscattered by the second layer to form second backscattered electrons. The electron microscope includes: a detection device configured to detect signal electrons, the signal electrons including the first backscattered electrons and the second backscattered electrons; and a signal processing device configured to generate an image, the image providing information about both the first layer and the second layer.

According to a further aspect, a device for examining a sample is presented, the sample having a multilayer structure with a first layer arranged above a second layer. The apparatus comprises: a vacuum chamber; a sample support arranged in the vacuum chamber, wherein the sample support is configured to support a sample; and a plurality of electron microscopes for simultaneous inspection of multiple regions of the sample. Each electron microscope is configured to direct a primary electron beam towards the sample such that first primary electrons of the primary electron beam are backscattered by the first layer to form first backscattered electrons and second primary electrons of the primary electron beam are backscattered by the second layer to form second backscattered electrons. The electron microscope includes a detection device configured to detect signal electrons, the signal electrons including the first backscattered electrons and the second backscattered electrons, respectively. Furthermore, a signal processing device is provided, the signal processing device being configured to generate an image, the image containing information about both the first layer and the second layer.

Drawings

A full and enabling disclosure, including the remainder of the specification, directed to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures wherein:

fig. 1 shows a schematic cross-sectional view of an apparatus for inspecting a sample according to embodiments described herein;

FIG. 2 shows a schematic cross-sectional view of an apparatus for inspecting a sample according to embodiments described herein;

FIG. 3 shows a schematic cross-sectional view of an apparatus for inspecting a sample according to embodiments described herein;

FIG. 4A depicts an image of a sample produced according to the methods described herein;

FIG. 4B depicts an image of a sample generated according to a conventional method; and

FIG. 5 is a flow chart representing a method for inspecting a sample according to embodiments described herein.

Detailed Description

The detailed description will now be completed in various example embodiments, one or more examples of which are illustrated in the various figures. The examples are provided by way of illustration and are not meant as limitations. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. This means that the present disclosure includes such modifications and variations.

In the following description of the drawings, like reference numerals refer to like parts. Only the differences with respect to the respective embodiments are explained. The structures shown in the drawings are not necessarily to scale, emphasis instead being placed upon providing a better understanding of the embodiments.

The term "sample" as used herein includes a substrate having a multilayer structure formed thereon. The substrate may be a non-flexible substrate or a flexible substrate. The non-flexible substrate is for example a glass substrate or a glass plate and the flexible substrate is for example a web or foil. The sample may be a coated substrate in which one or more thin layers of material are coated or deposited on the substrate, for example, by a Physical Vapor Deposition (PVD) process or a Chemical Vapor Deposition (CVD) process. In particular, the sample may be a substrate for display manufacturing, having a plurality of electronic or optoelectronic devices formed thereon. Electronic or optoelectronic devices formed on a substrate are typically thin film devices, comprising a stack of thin layers. For example, the sample may be a substrate having an array of Thin Film Transistors (TFTs) formed thereon, such as a thin film transistor-based substrate.

Embodiments described herein relate to inspection of a sample, wherein the sample includes a multilayer structure, which may be formed on a substrate. The multilayer structure may comprise an electronic or optoelectronic device, such as a transistor, in particular a thin film transistor. The substrate may be a large area substrate, in particular a large area substrate for display manufacturing.

According to some embodiments, the large area substrate may have at least 1m²The size of (c). The size may be from about 1.375m²(1100mm x 1250 mm-generation 5) to about 9m²More particularly from about 2m²To about 9m²Or even up to 12m². For example, the large area substrate may be generation 5, generation 7.5, generation 8.5, or even generation 10, generation 5 corresponding to about 1.375m²Substrate (1.1m x 1.25.25 m), generation 7.5 corresponds to about 4.39m²Substrate (1.95m x 2.25.25 m), generation 8.5 corresponds to about 5.7m²Base plate (2.2m x2.5m), generation 10 corresponding to about 9m²The substrate (2.88m × 3130 m). Even higher generations, such as 11 th and 12 th generations, and corresponding substrate areas may be applied in a similar manner.

Conventional (regular) process control may be advantageous in the manufacture of flat panels, displays, Organic Light Emitting Diode (OLED) devices, such as OLED screens, TFT-based substrates, and other samples including a plurality of electronic or optoelectronic devices formed thereon. Process control may include routine monitoring, imaging, and/or inspection of specific critical dimensions and defect inspection. The dimensions may relate to features below a top layer of the multilayer structure. In particular, it may be advantageous to inspect features underneath the passivation layer.

However, inspecting features of deep or buried layers can be difficult because most inspection techniques focus on inspecting the top surface of the sample. For example, it may not be feasible to inspect the buried layer using Secondary Electrons (SE), because the secondary electron signal typically originates from a sample depth of only a few nanometers (nm) from the top surface of the sample and thus cannot image features below this depth. In particular, electron microscopes that examine samples with secondary electrons are not generally usable to examine features at least partially in depths deeper than a few nanometers.

"secondary electrons" as used herein may be understood as low energy (<50eV) electrons generated and ejected by a sample when a beam of primary charged particles, such as a primary electron beam, hits the sample. The secondary electrons may provide information about the geometric and spatial characteristics of the sample surface, such that the secondary electron signal of a Scanning Electron Microscope (SEM) may be used to generate an image of the sample surface. Secondary electrons are typically ejected from the sample surface in a few nanometers, and most of the secondary electrons have energies in the range of several eV to about 10eV, particularly less than 50 eV. Secondary electrons may be generated when the primary electrons transfer energy to "free" (loosely bound) electrons of the sample material. Metal layers with a large number of free electrons typically emit a large number of secondary electrons.

As used herein, "backscattered electrons (BSEs)" may be understood to be based on electrons that impinge on the sample, scattered or reflected by atoms of the sample. In particular, the primary electrons of the primary electron beam may impinge on the sample and may be elastically or inelastically scattered back by atoms of the sample. Generally, the energy of the backscattered electrons is in the range of more than 1keV, for example, several keV to 10keV or more, depending on the energy of the primary electrons. In the case of an elastic scattering process, the energy of the backscattered electrons may essentially correspond to the energy of the incident primary electrons.

Backscattered electrons may be able to escape from deeper layers of the sample due to their high electron energy. Therefore, backscattered electrons are available for obtaining spatial information about deeper or buried layers of the substrate, e.g. layers from tens of nanometers to hundreds of nanometers or even more, below the sample surface. According to embodiments described herein, an image of the sample is generated based on the backscattered electron signals, such that the image may provide information not only of the top layer of the sample, but also of deeper layers.

The heavy elements backscatter electrons more strongly than the light elements. Therefore, the sample region including the heavy elements is brighter in the image than the region including the light elements. Therefore, backscattered electrons may be used to detect and distinguish regions of the sample comprising different chemical compositions.

According to embodiments described herein, backscattered electrons are utilized to examine layers of different chemical compositions, which are at least partially arranged on top of each other. In particular, backscattered electrons are used to understand a multilayer structure having a first layer and a second layer, wherein the first layer is arranged above the second layer. Specific samples and time-saving methods are described for inspecting and imaging samples having a multi-layer structure using an electron microscope configured to detect backscattered electrons.

Fig. 1 shows a schematic cross-sectional view of an apparatus 100 for inspecting a sample 10 according to embodiments described herein. The sample 10 has a multilayer structure 15, the multilayer structure 15 having a first layer 11 disposed over a second layer 12. In some embodiments, the multilayer structure 15 may have three, four, five, or more layers disposed at least partially on top of each other. For example, the multilayer structure 15 may be an array of electronic devices, such as thin film transistors, deposited on a substrate, such as a large area substrate for display manufacturing.

The method according to an embodiment comprises arranging the sample 10 in a vacuum chamber (not shown in fig. 1) and directing the primary electron beam 20 towards the sample 10 such that the primary electron beam 20 impinges on the sample 10. For example, the primary electron beam 20 may be focused on the sample by an objective lens. The primary electron beam 20 is directed onto the sample 10 such that first primary electrons of the primary electron beam 20 are backscattered by the first layer 11 to form first backscattered electrons 21 and second primary electrons of the primary electron beam are backscattered by the second layer 12 to form second backscattered electrons 22. Typically, for example at small reflection angles of 30 ° or less, the first backscattered electrons 21 and the second backscattered electrons 22 are reflected back from the sample in a backward direction, which is essentially opposite to the direction of incidence of the primary electron beam 20.

Thus, the detection means 130 detect signal electrons comprising first backscattered electrons 21 and second backscattered electrons 22 for obtaining spatial information of both the first layer 11 and the second layer 12. The first backscattered electrons 21 and the second backscattered electrons 22 may be detected simultaneously by the detection means, i.e. in a one-stage acquisition process. In particular, the detection signal may be processed by the signal processing device 160, and the signal processing device 160 may be configured to generate an image of at least a region of the sample 10 based on the detection signal. The signal processing device 160 may alternatively or additionally be configured to identify defects, measure distances and dimensions, and/or inspect features, such as edges of both the first layer 11 and the second layer 12, based on the detection signals.

The signal electrons detected by the detection means 130 comprise both first backscattered electrons 21 reflected by the first layer 11 and second backscattered electrons 22 reflected by the second layer 12. In some embodiments, the signal electrons detected by detection device 130 may include other backscattered electrons scattered from one or more other layers. Thus, the detector signal provides spatial information about both the first layer 11 and the second layer 12, so that both the first layer 11 and the second layer 12 can be examined based on the detection signal.

According to the embodiments described herein, the parameters of the primary electron beam 20 are selected such that first backscattered electrons 21 and second backscattered electrons 22 are emitted from the sample 10. In particular, the electron energies of the primary electron beams are selected such that at least some of the primary electrons of the primary electron beams 20 penetrate the sample 10 to the second layer 12. For example, the landing energy (landing energy) of the primary electron beams 20 impinging on the sample may be set such that at least a portion of the primary electrons penetrate at least the first layer 11 and are scattered back by the second layer 12. In particular, the landing energy of the primary electron beam 20 on the sample may be 5keV or more, in particular 10keV or more, more in particular 30keV or more, or even 50 keV. In some embodiments, the landing energy of the primary electron beam 20 on the sample may be below 5keV, for example from 1keV to 5keV, for example about 3 keV. The landing energy may be selected according to the characteristics of the layer stack to be inspected, for example according to the number and thickness of the layers.

In some embodiments, the position of the sample and the size of the focal point of the primary electron beam 20 may be set such that the first backscattered electrons 21 and the second backscattered electrons 22 are emitted by the sample 10 and detected by the detection device 130 with high efficiency, while at the same time providing sufficient spatial resolution. Further, the brightness of the primary electron beam may be appropriately selected.

According to embodiments described herein, spatial insight in two or more layers of a multilayer structure, which are arranged on top of each other, is obtained using a single-stage acquisition process. In other words, a layer stack comprising two or more layers is examined with signal electrons simultaneously scattered by the sample upon impact of one primary electron beam. According to the method described herein, it may be unnecessary to collect information of a first layer by first detecting electrons of a first main beam scattered by the first layer and subsequently collecting information of a second layer by detecting electrons of a second main beam scattered by the first layer, wherein the subsequently collected information may be processed in one image. Upon impact of one main beam, information on both the first layer 11 and the second layer 12 is instead collected simultaneously. In particular, based on the information acquired in the single acquisition phase, an image of the sample may be generated. Information on the topology (topology) and geometry of the features below the second layer can be obtained without using any spectroscopy (e.g., Energy Dispersive Spectroscopy (EDS)). The material contrast between the first and second layers is instead directly visible from the image generated based on the electronic signal.

The methods described herein are based on the discovery that multilayer structures formed on substrates used in display manufacturing typically include a plurality of spatial features, such as edges, steps (steps), holes, openings, grooves, overlaps, and/or undercuts (undercuts) of the first and second layers 11, 12, where the overlap between the first and second layers 11, 12 varies locally. Further, the first layer 11 and the second layer 12 comprise different materials having different atomic numbers, having different backscattering capabilities. Thus, the area of the changed overlap between the first layer 11 and the second layer 12 will appear as an area of a particular change in brightness in the detection signal and the resulting image, respectively.

In a first example, the opening may be formed in the second layer at a specific position, but not in the first layer. The second layer may be made of a heavy material with a high electron backscattering capability. In an image generated based on signal electrons including the first backscattered electrons and the second backscattered electrons, the openings in the second layer may be displayed as areas of reduced brightness, such that the size of the openings may be measured.

In the second example, the first layer 11 and the second layer 12 should ideally have corresponding edges, forming the ends of both the first and second layers. However, there may be undercutting in the actual sample such that the second layer ends before the first layer. In an image generated based on signal electrons including first backscattered electrons and second backscattered electrons, the edge region may be regarded as at least three regions of different brightness, and the width of the undercut may be measured. In particular, the regions of the first and second layers arranged above each other may have a brightness in the resulting image that is different from the brightness of the regions where only the first layer is present.

The ideal geometry and topology of the multilayer structure is known in advance. Thus, by comparing the ideal geometry and the geometry in the image generated based on the detection signal, defect inspection, metrology (metrology) and inspection of the features of the first and second layers is possible based on the information collected in the single stage acquisition process.

According to some embodiments described herein, a region of the sample 10 is scanned with the primary electron beam 20 at a single time, and an image of the region is electronically generated based on the detected signal during the scan. The resulting image may provide spatial information for both the first layer 11 and the second layer 12. For example, features of the generated image may be compared to corresponding features of the ideal topology to identify defects of the sample.

According to embodiments, which can be combined with other embodiments described herein, the method may comprise electronically generating an image of the multilayer structure 15 based on the detected signal, wherein the image comprises spatial information of both the first layer 11 and the second layer 12. A scanning deflector arrangement may be provided for scanning the primary electron beam 20 over the sample.

This method may alternatively or additionally comprise inspecting the first layer 11 and the second layer 12, in particular inspecting the quality of the edges of at least one or both of the first layer 11 and the second layer 12. In some embodiments, the first layer 11 and the second layer 12 may be automatically inspected, for example by automatically measuring the dimensions of specific features of the buried layer, or by automatically comparing the measured dimensions of the multilayer structure with the dimensions of the ideal topology.

The method may alternatively or additionally comprise inspecting, analyzing and/or identifying defects of at least one or both of the first layer 11 and the second layer 12.

This method may alternatively or additionally include measuring a distance or dimension of at least one or both of the first layer 11 and the second layer 12. For example, the size of features of buried or deep layers of a multilayer structure may be measured.

The method may alternatively or additionally comprise performing overlay metrology, for example comprising checking edge quality of the first layer and the second layer.

In some embodiments, which can be combined with other embodiments described herein, the multilayer structure 15 has three, four, five or more layers, which are at least partially arranged on top of each other. For example, the multilayer structure 15 may include an array of thin film electronic devices, each including three or more layers. The three or more layers may be at least partially made of different materials having different atomic numbers, i.e., different Z-numbers.

For example, one or more of the three or more layers may be a metal layer, such as a copper layer or a silver layer. At least one of the three or more layers may alternatively or additionally be a Transparent Conductive Oxide (TCO) layer, such as an Indium Tin Oxide (ITO) layer. At least one of the three or more layers may alternatively or additionally be a dielectric layer, such as an insulating dielectric layer. For example, a dielectric layer may be at least partially disposed between two conductive layers of a multilayer structure. In some embodiments, at least one semiconductor layer may be provided.

In some embodiments, the respective primary electrons of the primary electron beam 20 are scattered by each of the three or more layers of the multilayer structure 15 and detected by the detection device 130 for obtaining spatial information of each of the three or more layers, in particular in a single-stage acquisition process.

For example, in some embodiments, an image may be generated based on signal electrons including first backscattered electrons 21 backscattered by the first layer 11, second backscattered electrons 22 backscattered by the second layer 12, third backscattered electrons backscattered by a third layer disposed at least partially below the second layer, and selected fourth or other backscattered electrons backscattered by a fourth or other layer disposed at least partially below the third layer. The first, second, third, and other backscattered electrons may correspond to the scattered portion of a single primary electron beam impinging on the sample. Thus, by scanning the sample at a single time, for example, an image containing spatial information of multiple layers of a multi-layer substrate may be formed based on the detection signals during a single stage acquisition process.

In some embodiments, the inspected sample may include a large area substrate 13 for display manufacturing, wherein a multilayer structure 15 is formed on the sample, for example, by one or more deposition techniques. The substrate may have a thickness of 1m²Or more, in particular 5m²Or more. Accordingly, the methods described herein are performed in a vacuum chamber, which may include a substrate support configured to support a large area substrate 13, the large area substrate 13 having a thickness of 1m²Or more, in particular 5m²Or more. In particular, the vacuum chamber may be large enough to support and inspect a complete sample by detecting backscattered electrons.

The multilayer structure 15 may comprise a plurality of multilayer electronic or optoelectronic devices, such as transistors, in particular TFTs. In some embodiments, the sample may be or include at least one of a glass panel, a display panel, a Liquid Crystal Display (LCD) screen, a TFT screen, and an OLED display.

The apparatus 100 may comprise an in-line inspection apparatus comprising an electron microscope configured for in-line inspection of a sample during manufacturing, for example after forming a multilayer structure on a substrate. For example, the electron microscope 200 may be disposed in a vacuum system configured to deposit one or more layers on a substrate, the electron microscope 200 being, for example, disposed in an inspection chamber downstream of the deposition chamber.

The electron microscope may be a Scanning Electron Microscope (SEM) configured to scan the sample and generate an image of at least a region of the sample based on the detection signal.

In some embodiments, the multilayer structure 15 may include multilayer features having non-linear or curved edges, wherein the non-linear or curved edges are imaged or inspected. For example, the methods described herein may be applicable to imaging and inspecting curved features, irregular features, curved (round) features, and other non-linear features of a buried layer, which may be disposed below a top layer.

According to embodiments, which can be combined with other embodiments described herein, the multilayer structure 15 can comprise a passivation layer. The passivation layer may be an upper layer disposed over the one or more buried layers. For example, the passivation layer may be a protective layer or a shielding layer. At least the second layer 12 (or both the first and second layers) may be arranged below the passivation layer. Thus, the spatial characteristics of the layers arranged below the passivation layer can be understood. In particular, at least one of the first layer 11 and the second layer 12 may be arranged on any of the array, the back, or the front of the TFT-type display panel or on a substrate used in the manufacture of the TFT-type display panel. For example, in the case of an OLED display, at least one of the array (back) and the front can be inspected according to the methods described herein.

The first layer 11 may comprise a first material having a first atomic number with a first electron backscattering capability, and the second layer 12 may comprise a second material having a second atomic number with a second electron backscattering capability. For example, the Z-number of the first material and the Z-number of the second material may differ by more than 10, in particular by more than 20.

The method may further comprise generating an image based on the detected signal electrons, wherein the holes, openings, steps, grooves, covered portions and/or undercuts of at least one of the first and second layers respectively appear as areas of a particular brightness in the image.

In some embodiments, first layer 11 may comprise a first material having a first atomic number. A material residue made with a second material having a second atomic number different from the first atomic number may be disposed below the first layer. Such material residues may include residues of mask layers that are not completely removed, residues of layers that were not completely etched away in a previously applied etch process, particles that may have attached to the underlying layer after or during the deposition process, or other residues that may negatively affect the sample. Such material residue may be identified, for example, by inspection of the resulting image, according to embodiments described herein.

The primary electron beam 20 may have an average electron energy of 10keV or more, in particular 30keV or more. In particular, the primary electron beam 20 may have an electron energy between 10keV and 15 keV. The landing energy of the primary electron beam 20 on the sample may be 10keV or more, in particular 30keV or more. In particular, the landing energy may be between 10keV and 15 keV.

As schematically shown in fig. 1, a primary electron beam 20 is focused on the sample 10. The primary electron beam 20 may be generated by a beam source, shaped by electron optics arranged along the beam path, and focused by an objective lens (not shown in fig. 1). The beam source may be operated such that the primary electron beam has an electron energy of 5keV or more, in particular 10keV or more, and/or 50keV or less. The electron optical elements arranged along the beam path may be configured such that the primary electron beam impinges on the sample with a high electron energy of 5keV or more, in particular 10keV or more. In some embodiments, the beam source is operable such that the primary electron beam has an electron energy below 5keV, for example between 1 and 5 keV. Furthermore, in some embodiments, the primary electron beam may impinge on the sample at electron energies of up to 5 keV.

When the primary electron beam 20 hits the sample 10, a plurality of electrons are emitted from the sample, including secondary electrons 25 generated near the sample surface and backscattered electrons scattered back from various layers of the sample. Generally, the secondary electron signal is substantially stronger than the backscattered electron signal. However, high energy primary electrons may be backscattered from the sample with increased probability. More particularly, the ratio between backscattered electrons and secondary electrons emitted from the sample may be increased in the case of a primary electron beam having an increased energy.

According to some embodiments described herein, a filtering means may be arranged between the sample 10 and the detection means 130 for filtering the signal electrons to be detected by the detection means 130. In particular, low energy electrons, such as secondary electrons 25, may be suppressed by the filtering means, and higher energy electrons comprising only backscattered electrons may be allowed to proceed towards the detection means 130.

In particular, the filtering means may suppress electrons emitted from the sample 10 having an energy of electrons below an energy threshold, and the filtering means may be configured as a negatively biased filtering electrode 154 arranged between the sample 10 and the detection means 130.

As schematically shown in fig. 1, the filter electrode 154 may be disposed above the sample 10 and may be configured to supply a repulsive force on electrons emitted from the sample. The filter electrodes 154 may deflect low energy electrons, such as secondary electrons 25, back to the sample 10, while backscattered electrons having energies greater than an energy threshold may pass through the filter electrodes 154 towards the detection device 130. The filter electrode 154 may be configured as a sheet electrode with holes, or a filter grid.

The filter electrode 154 may be set to a negative potential magnitude of, for example, 50V or more, so that only electrons having an electron energy greater than 50eV may be transmitted toward the detection device 130. As schematically shown in fig. 1, the first backscattered electrons 21 and the second backscattered electrons 22 may pass through the filter electrode 154 towards the detection means 130, while the secondary electrons 25 are deflected back to the sample 10.

The filtering electrode 154 may be set to an adjustable variable potential and may be adapted to filter backscattered electrons reflected from a particular depth range of the multilayer structure 15. Two or more filtering electrodes may be provided in some embodiments.

In the secondary electron detection mode, the filter electrode 154 may be set to a potential that allows secondary electrons 25, such as electrons having an electron energy less than 50eV, to pass through toward the detection device. For example, in the secondary electron detection mode, the filter electrode 154 may be set to a ground potential or a positive potential. The secondary electrons may be detected by the detection device 130 or other detection device configured to detect the secondary electrons. In the secondary electron detection mode, the topography of the surface of the sample can be examined in detail. Thus, secondary electrons are selectively accumulated or suppressed.

In some embodiments, which can be combined with other embodiments described herein, the method described herein can include detecting the first backscattered electrons 21 and the second backscattered electrons 22 with an in-column detector 136. The in-column detector 136 may be understood as a detection device, arranged at least partially around the optical axis of the primary electron beam 20. The in-barrel detector 136 may include a detection opening 137 for allowing the primary electron beam 20 to propagate therethrough. One or more detection sections of the in-barrel detector may be arranged at least partially around the optical axis. For example, the in-tube detector may have a ring shape and extend partially or completely around the optical axis. The in-column detector 136 may detect electrons backscattered from the sample at small reflection angles, for example, between 1 ° and 30 °.

The in-tube detector 136 may include a central opening to allow the primary electron beam 20 to propagate through the in-tube detector 136. Further, the in-tube detector 136 may face (subsidiary) an azimuth angle of at least several degrees at the beam irradiation point. Using geometry to make the detection means subtend an azimuth angle large enough at the point of impact of the primary electron beam allows detection of a backscattered electron signal strong enough to image the underlying layer also quickly.

In other embodiments, other or additional forms of detection means may be provided.

The detection signal of the detection device 130 may be sent to a signal processing device 160, and the signal processing device 160 is configured to process the detection signal, for example, for generating an image of at least a region of the sample, or for performing defect recognition or critical dimension metrology.

The methods described herein provide in-line imaging of large area substrates for display manufacturing, where buried features that may span multiple layers (a few nanometers to 10nm or more, tens of nanometers, or even hundreds of nanometers) can be inspected. Such features are generally not detectable by detecting secondary electrons, which are generated in a few nanometers of the surface.

In some embodiments, the vacuum chamber of the apparatus 100 may be large enough to arrange and inspect the entire sample under vacuum conditions, such as downstream of the fabrication of the multilayer structure in the same vacuum system. Detection of backscattered electrons (BSEs) may be performed more quickly and more reliably under sub-atmospheric conditions, since BSEs are scattered by air molecules and may not reach the detection device at atmospheric pressure. For example, the methods described herein can be performed at a background pressure of less than 1mbar, in particular less than 0.1 mbar. The pressure in the column (column) of the electron microscope may be even less.

Imaging the sample 10 as described herein provides elemental contrast based on the atomic number of the materials of the layers of the multilayer structure. A distinction between different materials of the layer stack of the display device is possible. The different materials may have similar secondary electron emission coefficients, but have widely varying BSE emission coefficients due to the large difference in atomic numbers of the respective materials.

Fig. 2 is a schematic cross-sectional view of an apparatus 100 for inspecting a sample 10 according to embodiments described herein. The apparatus is configured to operate in accordance with the methods described herein and may be similar to the apparatus depicted in fig. 1, such that reference may be made to implementations that are described above without repetition.

The apparatus 100 comprises a vacuum chamber 101, wherein a sample support 150 configured to support a sample 10 is arranged in the vacuum chamber 101. Sample supportPiece 150 may be configured to support a large area substrate for display manufacturing, particularly with 1m²Or more, in particular 5m²Or more, more particularly 10m²Or larger sized large area substrates.

The apparatus 100 further comprises an electron microscope 200, the electron microscope 200 being configured to direct the primary electron beam 20 towards the sample 10 such that first primary electrons of the primary electron beam 20 are backscattered by a first layer of the sample to form first backscattered electrons and second primary electrons are backscattered by a second layer of the sample to form second backscattered electrons.

The sample support 150 may extend along the x-direction. The sample support 150 may be movable along the x-direction to displace the sample 10 relative to the electron microscope 200 in the vacuum chamber 101. Thus, a region of the sample 10 may be located under the electron microscope 200 for inspection. This region may comprise a multilayer structure, such as a multilayer electronic device to be inspected, having, for example, particles (grains) or defects contained in a layer on the sample. The sample support 150 may also optionally be movable along the y-direction so that the sample 10 may be moved along the y-direction, which may be perpendicular to the x-direction. By suitably displacing the sample support 150 supporting the sample 10 in the vacuum chamber 101, the entire extent of the sample 10 can be inspected inside the vacuum chamber 101.

The electron microscope 200 may include an electron source 112 configured to generate a primary electron beam 20. The electron source 112 may be an electron gun (electron gun) configured to generate a primary electron beam having an electron energy of up to 5keV, 5keV or more, particularly 10keV or more, more particularly 15keV or more. In the gun chamber 110, further beam shaping means may be provided, like suppressors, extractors (extractors) and/or anodes. The beam may be aligned with a beam limiting aperture (beam limiting aperture) that may be sized to shape the beam, i.e., block a portion of the beam. The electron beam source may comprise a Thermal Field Emission (TFE) emitter. The gun chamber 110 may be vented to 10^-8mbar to 10^-10A pressure of mbar.

The electron microscope 200 may further comprise a column 120, wherein the primary electron beam 20 propagates through the column 120 along the optical axis. The electron-optical element 126 may be arranged in the column 120 along the optical axis, wherein the electron-optical element 126 may be configured to collimate (collimate), shape (shape), deflect, and/or correct (correct) the primary electron beam 20. For example, a condenser lens (condenser lens) may be disposed in the cylinder 120. The condenser lens may include a pole piece and a coil 124. Other electron optical elements may be provided selected from the group consisting of an stigmator (stigmator) for chromatic and/or spherical aberration, a correction element for aligning the primary electron beam with the optical axis of the objective lens 140, and an alignment deflector (alignment deflectors).

The objective lens 140 may be arranged for focusing the primary electron beam 20 on the sample 10 with landing energies of up to 5keV or more, particularly 10keV or more, more particularly 15keV or more.

As shown in fig. 2, the objective lens 140 may have a magnetic lens component, have pole pieces 142 and 146, and have a coil 144. The upper electrode 152 may alternatively form an electrostatic lens component of the objective lens 140.

In addition, a scan deflector assembly 170 may be provided. The scan deflector assembly 170 may be, for example, magnetic, but also an electrostatic scan deflector assembly. The scan deflector assembly 170 may be a single stage assembly as shown in fig. 2. Alternatively, a secondary or even tertiary deflector assembly may be provided for scanning. The stages may be disposed at different positions along the optical axis.

The electron microscope 200 further comprises a detection device 130 configured to detect signal electrons comprising first backscattered electrons and second backscattered electrons. The detection signal may be supplied to a signal processing device 160, the signal processing device 160 being configured to generate an image comprising spatial information of both the first layer and the second layer based on the detection signal.

The electron microscope 200 may further comprise a filter electrode 154 arranged between the sample support 150 and the detection device 130, for example at a short distance above the sample support 150. The filtering electrode 154 may be configured to suppress low-energy electrons, particularly secondary electrons. For example, the filter electrode 154 may suppress electrons emitted from the sample 10 having an electron energy below an energy threshold of, for example, 50 eV. Further, the filtering electrode 154 may be configured to allow signal electrons having an electron energy above the energy threshold to pass towards the detection device 130.

In particular, signal electrons comprising first backscattered electrons and second backscattered electrons may pass through the filtering electrode 154 towards the detection means 130. In some embodiments, the filter electrode 154 is configured to be set at a negative potential, wherein the negative potential may be, for example, greater than 50V, to suppress secondary electrons and allow backscattered electrons to pass through.

In some embodiments, which can be combined with other embodiments described herein, the detection device can include an in-barrel detector 136 having an opening for the primary electron beam 20. The in-tube detector 136 may be adapted to detect signal electrons having an energy of 50eV or more. In particular, the in-column detector 136 may be adapted to detect backscattered electrons having energies of 1keV or more.

Fig. 3 is a schematic cross-sectional view of an apparatus 300 for inspecting a sample 10 according to embodiments described herein. The apparatus 300 comprises a vacuum chamber 101 and a sample support 150, the sample support 150 being arranged in the vacuum chamber 101 for supporting a sample 10. The vacuum chamber 101 may be similar to that depicted in fig. 2, such that the reference may be made as described above.

Further, the apparatus 300 comprises a plurality of electron microscopes 310 for inspecting a plurality of regions of the sample 10 simultaneously. Two electron microscopes 310 are exemplarily depicted in fig. 3, namely a first electron microscope 312 and a second electron microscope 314. In some embodiments, three or more electron microscopes can be provided for inspecting corresponding regions of the sample 10. The electron microscope may be similar to the electron microscope 200 of fig. 2, such that reference may be made to the above description without repetition.

In particular, each electron microscope of the plurality of electron microscopes 310 may be configured to direct a primary electron beam toward the sample 10 such that a first primary electron of the primary electron beam is backscattered by the first layer into a first backscattered electron and a second primary electron is backscattered by the second layer into a second backscattered electron. The electron microscope may comprise respective detection means configured to detect signal electrons comprising respective first and second backscattered electrons.

The signal processing means may be arranged to generate an image comprising information of both the first layer and the second layer. In some embodiments, each electron microscope includes a respective signal processing device. In other embodiments, the detection signals of the plurality of electron microscopes 310 may be supplied to a common signal processing apparatus, which may be configured to generate images of multiple regions of the sample imaged by the plurality of electron microscopes 310. The image provides spatial information for both the first and second layers of the sample 10.

The first electron microscope 312 may be spaced a distance 335 along the x-axis from the second electron microscope 314. In the embodiment illustrated in fig. 3, the distance 335 is the distance between the first optical axis of the first electron microscope 312 and the second optical axis of the second electron microscope 314. As further shown in fig. 3, the vacuum chamber 101 has an internal width 321 along the x-direction. According to an embodiment, the distance 335 between the first electron microscope 312 and the second electron microscope 314 along the x-direction may be at least 30cm, for example at least 40 cm. According to further embodiments, which can be combined with other embodiments described herein, the inner width 321 of the vacuum chamber 101 can be in a range from 250% to 450% of the distance 335 between the first electron microscope 312 and the second electron microscope 314.

Embodiments described herein thus provide an apparatus for inspecting a sample, in particular comprising a large area substrate, with two or more electron microscopes separated from each other in a vacuum chamber 101. Because the sample can be examined by two or more electron microscopes in parallel, the throughput (throughput) can be increased compared to embodiments with single electron microscopes. For example, a first defect on the specimen may be inspected by the first electron microscope 312 and a second defect of the specimen may be inspected by the second microscope, wherein the inspection of the first defect and the second defect are performed in parallel.

According to some embodiments, which can be combined with other embodiments described herein, the electron microscope can be a scanning electron microscope, wherein depending on the measurement conditions, images with a very high resolution, for example of 1 to 20nm, are provided.

According to some applications, the apparatus for inspecting the sample may be an in-line apparatus, i.e., the apparatus may be arranged in-line with other manufacturing, testing or processing devices, which may include a load lock for loading and unloading the sample into the vacuum chamber for imaging. The vacuum chamber may include one or more valves that may connect the vacuum chamber to another chamber, particularly if the apparatus is an in-line apparatus. After the sample has been directed into the vacuum chamber, the one or more valves may be closed. Thus, for example, the atmosphere in the vacuum chamber may be controlled by generating a technical vacuum, using one or more vacuum pumps.

Fig. 4A shows an image of a sample 10 produced according to the methods described herein. Fig. 4B shows an image of the same sample generated according to a conventional method.

The sample 10 includes a multilayer structure 15, the multilayer structure 15 having a plurality of layers, the layers being at least partially arranged on top of each other. The layers may comprise materials having different atomic numbers such that the layers may differ in their ability to backscatter electrons. For example, the multilayer structure 15 may include a first layer 401, the first layer 401 including a first material that may be a top layer of the multilayer structure 15. The multilayer structure may further comprise a second layer 402, a third layer 403 and a fourth layer 404 arranged below the first layer 401, the second layer 402 comprising the second material, the third layer 403 comprising the third material and the fourth layer 404 comprising the fourth material.

In some embodiments, the multilayer structure 15 may constitute an electronic device, which is deposited on a substrate. At least one layer may be a metal layer providing a conductive path or via; at least one layer may be a conductive layer providing an electrode, for example a gate region, a source region or a drain region; at least one layer may be a dielectric layer; at least one layer may be a passivation layer; and/or at least one layer may be a semiconductor layer.

When a primary electron beam having predetermined beam properties impinges on the sample 10, first electrons of the primary electron beam are backscattered by the first layer 401 to form first backscattered electrons, second electrons of the primary electron beam are simultaneously backscattered by the second layer 402 to form second backscattered electrons, third electrons of the primary electron beam are backscattered by the third layer 403 to form third backscattered electrons, and fourth electrons of the primary electron beam are backscattered by the fourth layer 404 to form fourth backscattered electrons. The image depicted in fig. 4A may be generated based on the backscattered signal electrons.

As clearly seen in fig. 4A, spatial information for each of the first through fourth layers can be derived from the detected backscattered signal electrons. In particular, the layer edge region may be inspected to perform overlay measurements, the dimensions of the buried layer may be measured, material residues that may be hidden underneath the upper layer may be identified, and/or defects of the buried layer may be inspected or analyzed.

FIG. 4B illustrates a comparative example of an image generated according to a conventional method, including primary detection and processing of Secondary Electrons (SEs). As clearly shown in fig. 4B, essentially only the first layer 401 is visible from the resulting image, making it infeasible to inspect any buried layers of the sample 10. Furthermore, no information about the material form and in particular about the atomic number of atoms in the investigated sample can be identified in the comparative example of fig. 4B.

FIG. 5 is a flow chart illustrating a method of inspecting a sample according to embodiments described herein. The sample comprises a multilayer structure, having a stack of features arranged at least partially on top of each other, comprising a first layer 11 arranged above a second layer 12.

In block 510, a sample 10 is disposed in a vacuum chamber at sub-atmospheric pressure. For example, the sample is arranged on a sample support in the vacuum chamber such that a primary electron beam of the electron microscope can be directed towards a region of the substrate.

In block 520, the primary electron beam 20 is directed onto the sample such that first primary electrons of the primary electron beam are backscattered by the first layer 11 to form first backscattered electrons 21, and at the same time second primary electrons of the primary electron beam are backscattered by the second layer 12 to form second backscattered electrons 22.

In block 530, the signal electrons emitted from the sample and comprising the first backscattered electrons 21 and the second backscattered electrons 22 are detected by a detection device for obtaining spatial information of both the first layer 11 and the second layer 12, in particular in a single-stage acquisition process. The area of the sample may be scanned as the signal electrons are detected by the detection device.

In optional block 540, an image of at least a region of the sample is generated by the signal processing device based on the detection signal. The image provides spatial information of both the first and second layers, and optionally of other layers of the multilayer structure.

In some embodiments, defect inspection or measurement and dimensional inspection of the multilayer structure may be performed next. In particular, overlay measurements may be performed.

While the foregoing is directed to embodiments, other and further embodiments may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.