阅读说明：本技术 可变分辨率光谱仪 (Variable resolution spectrometer ) 是由 M·尼尔 于 2019-01-03 设计创作，主要内容包括：本发明提供用于复原数字化光谱的系统、方法、设备及制品,且所述系统、方法、设备及制品可包括：光学系统,其经配置以变换射线,所述光学系统包含衍射光栅、转向镜、载台及经配置以根据移动机制移动所述载台、衍射光栅或转向镜中的一者以改变所述载台上的所述射线的入射的致动器；传感器阵列,其安置于所述载台上,所述传感器阵列经配置以在多个测量位置处接收从所述光学系统入射的所述射线以获得多个射线光谱；及处理器,其电连接到所述传感器阵列,所述处理器经配置以接收所述射线光谱、使所述射线光谱交错以产生交错光谱,且从所述交错光谱去卷积对应于所述光学系统的点散布函数以产生经复原数字化光谱。(Systems, methods, apparatus, and articles of manufacture for recovering digitized spectra are provided and may include: an optical system configured to transform a ray, the optical system including a diffraction grating, a turning mirror, a stage, and an actuator configured to move one of the stage, diffraction grating, or turning mirror according to a movement mechanism to change an incidence of the ray on the stage; a sensor array disposed on the stage, the sensor array configured to receive the radiation incident from the optical system at a plurality of measurement locations to obtain a plurality of radiation spectra; and a processor electrically connected to the sensor array, the processor configured to receive the ray spectra, interleave the ray spectra to generate an interleaved spectrum, and deconvolute a point spread function corresponding to the optical system from the interleaved spectrum to generate a recovered digitized spectrum.)

1. A variable resolution spectrometer, comprising:

an optical system configured to transform rays, the optical system comprising:

a diffraction grating is provided on the substrate,

a turning mirror is arranged on the upper portion of the frame,

a stage, and

an actuator configured to move one of the stage, diffraction grating, or turning mirror to change the incidence of the ray on the stage according to a movement mechanism, the movement mechanism having a start position and an end position; a sensor array disposed on the stage, the sensor array including a plurality of pixel columns, each pixel column having at least one pixel, wherein the sensor array is configured to receive the radiation incident from the optical system at a plurality of measurement locations to obtain a plurality of radiation spectra; and

a processor electrically connected to the sensor array, wherein the processor is configured to:

-receiving said spectrum of radiation,

interleaving the spectra of rays to produce interleaved spectra, an

Deconvolving a point spread function corresponding to the optical system from the interleaved spectrum to produce a recovered digitized spectrum.

2. The variable resolution spectrometer of claim 1, wherein the actuator is a piezoelectric actuator, a servo motor, or a stepper motor.

3. The variable resolution spectrometer of claim 1, wherein:

the stage is moved by the actuator; and is

The movement mechanism is an incremental translation, wherein:

the stage is translatably movable in one or more increments along a linear path from the starting position to the ending position, and

each of the increments has a start point and an end point separated by an incremental linear distance that is less than a total linear distance between the start position and the end position.

4. The variable resolution spectrometer of claim 1, wherein:

the stage is moved by the actuator; and is

The movement mechanism is a continuous translation, wherein the stage is substantially continuously translatably movable along a linear path from the start position to the end position.

5. The variable resolution spectrometer of claim 1, wherein:

the stage is moved by the actuator; and is

The movement mechanism is an incremental rotation, wherein:

the stage is rotatably moved in one or more increments along an arcuate path from the starting position to the ending position, and

each of the increments has a start point and an end point separated by an incremental arc length that is less than a total arc length between the start position and the end position.

6. The variable resolution spectrometer of claim 1, wherein:

the stage is moved by the actuator; and is

The movement mechanism is a continuous rotation, wherein the stage is substantially continuously rotatably moved along an arcuate path from the start position to the end position.

7. The variable resolution spectrometer of claim 1, wherein two measurement locations of the plurality of measurement locations are separated by a distance that is less than a pixel width.

8. The variable resolution spectrometer of claim 1, wherein the sensor array is a charge coupled device.

9. The variable resolution spectrometer of claim 1, wherein:

the diffraction grating is moved by the actuator; and is

The movement mechanism is an incremental translation, wherein:

the diffraction grating is translatably movable in one or more increments along a linear path from the starting position to the ending position, and

each of the increments has a start point and an end point separated by an incremental linear distance that is less than a total linear distance between the start position and the end position.

10. A method for recovering a digitized spectrum, comprising:

providing an optical system configured to transform rays, the optical system comprising:

a diffraction grating is provided on the substrate,

a turning mirror is arranged on the upper portion of the frame,

an actuator, and

a stage; and

performing a scan operation, the scan operation comprising:

moving one of the stage, diffraction grating, or turning mirror using the actuator according to a movement mechanism to change the incidence of the rays on the stage, the movement mechanism having a start position and an end position, and

sensing radiation incident on the sensor array from the optical system at a plurality of measurement locations using a sensor array comprising a plurality of pixel columns disposed on the stage to obtain a plurality of radiation spectra, wherein each of the pixel columns has at least one pixel; and

using a processor:

-receiving said spectrum of radiation,

interleaving the spectra of rays to produce interleaved spectra, an

Deconvolving a point spread function corresponding to the optical system from the interleaved spectrum to produce a recovered digitized spectrum.

11. The method of claim 10, wherein the actuator is a piezoelectric actuator, a servo motor, or a stepper motor.

12. The method of claim 10, wherein:

the stage is moved by the actuator; and is

The movement mechanism is an incremental translation, wherein:

the stage is translatably movable in one or more increments along a linear path from the starting position to the ending position, and

each of the increments has a start point and an end point separated by an incremental linear distance that is less than a total linear distance between the start position and the end position.

13. The method of claim 10, wherein:

the stage is moved by the actuator; and is

The movement mechanism is a continuous translation in which the stage is substantially continuously translatably movable along a linear path from the start position to the end position.

14. The method of claim 10, wherein:

the stage is moved by the actuator; and is

The movement mechanism is an incremental rotation, wherein:

the stage is rotatably moved in one or more increments along an arcuate path from the starting position to the ending position, and

each of the increments has a start point and an end point separated by an incremental arc length that is less than a total arc length between the start position and the end position.

15. The method of claim 10, wherein:

the stage is moved by the actuator; and is

The movement mechanism is a continuous rotation, wherein the stage is substantially continuously rotatably moved along an arcuate path from the start position to the end position.

16. The method of claim 10, wherein two of the plurality of measurement locations are separated by a distance less than a pixel width.

17. The method of claim 10, wherein the sensor array is a charge coupled device.

18. The method of claim 10, wherein:

the diffraction grating is moved by the actuator; and is

The movement mechanism is an incremental translation, wherein:

the diffraction grating is translatably movable in one or more increments along a linear path from the starting position to the ending position, and

each of the increments has a start point and an end point separated by an incremental linear distance that is less than a total linear distance between the start position and the end position.

19. The method of claim 10, wherein:

the diffraction grating is moved by the actuator; and is

The movement mechanism is a continuous translation, wherein the diffraction grating is substantially continuously translatably movable along a linear path from the starting position to the ending position.

20. A non-transitory computer-readable storage medium comprising one or more programs for performing the following steps on one or more computing devices:

receiving a spectrum of radiation obtained from radiation incident on a sensor array comprising a plurality of columns of pixels, each of the columns of pixels having at least one pixel, wherein the sensor array is disposed on a stage from an optical system comprising the stage, a diffraction grating, and a turning mirror, wherein the stage, diffraction grating, or turning mirror is moved using an actuator according to a movement mechanism to change the incidence of radiation on the stage, and wherein the movement mechanism has a start position and an end position;

interleaving the spectra of rays to produce interleaved spectra; and

deconvolving a point spread function corresponding to the optical system from the interleaved spectrum to produce a recovered digitized spectrum.

Technical Field

The present invention relates generally to improvements in semiconductor metrology. More particularly, the present invention relates generally to improvements in the measurement of thin films, grating structures, and critical dimension structures.

Background

The evolution of the semiconductor manufacturing industry places higher demands on yield management and, in particular, metrology and inspection systems. Critical dimensions continue to shrink, however, industry needs to reduce the time to achieve high yield, high value production. Minimizing the total time from detecting a yield problem to repairing it determines the return on investment by the semiconductor manufacturer.

Manufacturing semiconductor devices, such as logic and memory devices, typically includes processing a semiconductor wafer using a number of manufacturing processes to form various features and multiple levels of the semiconductor device. For example, photolithography is a semiconductor manufacturing process that involves transferring a pattern from a reticle to a photoresist disposed on a semiconductor wafer. Additional examples of semiconductor manufacturing processes include, but are not limited to, Chemical Mechanical Polishing (CMP), etching, deposition, and ion implantation. Multiple semiconductor devices may be fabricated in an arrangement on a single semiconductor wafer and then separated into individual semiconductor devices.

Metrology may be used during semiconductor manufacturing to make various measurements of, for example, a semiconductor wafer or reticle. Metrology tools may be used to measure structural and material properties associated with various semiconductor manufacturing processes. For example, the metrology tool may measure material composition or may measure the dimensional characteristics of the structure and film (e.g., film thickness, Critical Dimension (CD) or overlay of the structure). These measurements are used to facilitate process control and/or yield efficiency in the manufacture of semiconductor dies.

As semiconductor device pattern sizes continue to shrink, smaller metrology targets are often required. Furthermore, measurement accuracy and the requirement to match to actual device characteristics increases the need for device-like targets and in-die and even on-device measurements. Various metering implementations have been proposed to achieve this goal. For example, focused beam ellipsometry based on primary reflective optics has been proposed. The apodizer can be used to mitigate optical diffraction effects that cause the illumination spot to spread beyond a size defined by the geometry optics. The use of high numerical aperture tools in combination with simultaneous multiple angle of incidence illumination is another way to achieve small target capabilities.

Other examples of measurements may include measuring the composition of one or more layers of the semiconductor stack, measuring specific defects on (or within) the wafer, and measuring the amount of lithographic radiation exposed to the wafer. In some cases, metrology tools and algorithms may be configured for measuring non-periodic targets.

The measurement of the parameter of interest typically involves a number of algorithms. For example, the optical interaction of the incident beam with the sample is modeled using an Electromagnetic (EM) solver and using algorithms such as Rigorous Coupled Wave Analysis (RCWA), Finite Element Method (FEM), kinetic method, surface integration method, volume integration method, finite difference time domain method (FDTD), and others. The object of interest is typically modeled (parameterized) using a geometric engine or, in some cases, a process modeling engine, or a combination of both. In these cases a geometry engine is implemented.

The collected data may be analyzed by a number of data fitting and optimization techniques and technologies, including: a link library; a fast degradation model; regression; machine learning algorithms, such as neural networks, Support Vector Machines (SVMs); dimension reduction algorithms such as, for example, Principal Component Analysis (PCA), Independent Component Analysis (ICA), and Local Linear Embedding (LLE); sparse representation such as fourier transform or wavelet transform; a Kalman (Kalman) filter; algorithms that facilitate matching from the same or different tool types, and others.

The collected data may also be analyzed by algorithms that do not involve modeling, optimization, and/or fitting.

Computing algorithms are typically optimized for metrology applications in which one or more methods are used, such as design and implementation of computing hardware, parallelization, computing distribution, load balancing, multi-service support, dynamic load optimization, and the like. Different implementations of algorithms may be performed in firmware, software, Field Programmable Gate Arrays (FPGAs), programmable optical components, etc.

The data analysis and fitting steps generally pursue one or more of the following objectives: (1) measurements of CD, Side Wall Angle (SWA), shape, stress, composition, film, bandgap, electrical properties, focus/dose, overlay, generation process parameters (e.g., resist state, partial pressure, temperature, focus model), and/or any combination thereof; (2) modeling and/or design of metrology systems; and (3) modeling, design, and/or optimization of metrology targets.

In currently available film measurement systems, the illumination beam first passes through the film stack to be measured and then through a grating or prism. An image is generated on the sensor that includes the resulting spectrum digitized and passed to the pixel array of the compute engine. The calculation engine uses modeling techniques to determine properties of the film stack, such as thickness or material properties of each layer.

One problem that these systems present is that: its spectral resolution is limited by its optical Point Spread Function (PSF) and the sensor pixel size. The problem is exacerbated when measuring thick film stacks, such as High Aspect Ratio (HAR) devices, e.g., 3D flash, when the width of the PSF is greater than the period of the spectral signal. This signal is then further attenuated as it is quantized into individual pixels that also have a sequence similar to the period of the spectral signal.

These attenuation effects are typically deconvoluted from the signal before being solved for the film stack parameters, as modeling these effects is expensive in terms of computational resources. However, deconvolution cannot properly reconstruct the ideal spectrum with a thick film stack. This failure is most pronounced in shorter wavelengths such as ultraviolet light.

In addition, the thick film stack produces a high frequency response for shorter wavelengths. Conventional techniques fail to reconstruct an ideal spectrum for post-processing. A calculation engine using conventional techniques cannot correctly determine the base film stack properties. This greatly reduces the effectiveness of the inspection tool.

The present invention overcomes these and other limitations, thus improving the ability of inspection tools to measure new types of film stacks.

Disclosure of Invention

In an embodiment of the present invention, a variable resolution spectrometer is provided that includes an optical system configured to transform rays, a sensor on a stage, an actuator, and a processor. The optical system may include a diffraction grating, a turning mirror, a stage, and an actuator configured to move one of the stage, diffraction grating, or turning mirror according to a movement mechanism to change an incidence of the ray on the stage. The movement mechanism may include a start position and an end position. The variable resolution spectrometer may further include a sensor array disposed on the stage and including a plurality of columns of pixels. The sensor array may be configured to receive the radiation incident from the optical system at a plurality of measurement locations to obtain a plurality of radiation spectra. Each pixel column may have at least one pixel. The variable resolution spectrometer may further include a processor electrically connected to the sensor array. The processor may be further configured to receive the ray spectra, interleave the ray spectra to generate interleaved spectra, and deconvolve a point spread function corresponding to the optical system from the interleaved spectra to generate a recovered digitized spectrum.

In another embodiment, the invention may be embodied as a method for recovering a digitized spectrum. The method can comprise the following steps: providing an optical system configured to transform the radiation; executing a scanning operation; and processing the spectrum of radiation into a digitized spectrum using a processor. The optical system may include a diffraction grating, a turning mirror, an actuator, and a stage. The scan operation may include: moving one of the stage, diffraction grating, or turning mirror according to a movement mechanism using the actuator to change the incidence of the rays on the stage; and sensing radiation incident on the sensor array from the optical system at a plurality of measurement locations using a sensor array to obtain a plurality of radiation spectra, wherein each of the columns of pixels has at least one pixel. The movement mechanism may have a starting position and an ending position. The sensor array may be disposed on the stage and may include a plurality of pixel columns. At the processor, a ray spectrum may be received, the ray spectra may be interleaved to produce an interleaved spectrum, and a point spread function corresponding to the optical system may be deconvolved from the interleaved spectrum to produce a recovered digitized spectrum.

In another embodiment, the invention may be embodied as a non-transitory computer readable storage medium comprising one or more programs for executing steps on one or more computing devices. The steps may include: receiving a spectrum of radiation obtained from radiation incident on the sensor array; interleaving the spectra of rays to produce interleaved spectra; and deconvolving a point spread function corresponding to the optical system from the interleaved spectrum to produce a recovered digitized spectrum. The sensor array may include a plurality of pixel columns, and each of the pixel columns may have at least one pixel. The sensor array may be disposed on a stage. The spectrum of radiation may be received from an optical system comprising a stage, a diffraction grating, and a turning mirror, wherein the stage, diffraction grating, or turning mirror may be moved using an actuator according to a movement mechanism to change the incidence of radiation on the stage. The moving mechanism may have a starting position and an ending position.

The actuator may be a piezoelectric actuator, a servo motor, a stepper motor, or another suitable actuator.

In an embodiment, the stage may be moved by an actuator according to an incremental translational movement mechanism. In an incremental translational movement mechanism, the stage may be translatably movable along a linear path from a start position to an end position in one or more increments, and each of the increments may have a start point and an end point separated by an incremental linear distance that is less than a total linear distance between the start position and the end position.

In an embodiment, the stage may be moved by an actuator according to a continuous translational movement mechanism. In a continuous translational movement mechanism, the stage may be substantially continuously translatably movable along a linear path from a start position to an end position.

In an embodiment, the stage may be moved by an actuator according to an incremental rotational movement mechanism. In an incremental translational movement mechanism, the stage may be rotatably moved along an arcuate path from a starting position to an ending position in one or more increments, and each of the increments may have a starting point and an ending point separated by an incremental arc length that is less than a total arc length between the starting position and the ending position.

In an embodiment, the stage may be moved by an actuator according to a continuous rotational movement mechanism. In the continuous rotation movement mechanism, the stage is rotatably movable substantially continuously along an arc-shaped path from the start position to the end position.

In an embodiment, the diffraction grating may be moved by an actuator according to an incremental translational movement mechanism. In an incremental translational movement mechanism, the diffraction grating may be translatably movable along a linear path from a start position to an end position in one or more increments, and each of the increments may have a start point and an end point separated by an incremental linear distance that is less than a total linear distance between the start position and the end position.

In an embodiment, the diffraction grating may be moved by an actuator according to a continuous translational movement mechanism. In the continuous translational movement mechanism, the diffraction grating may be substantially continuously translatably movable along a linear path from the start position to the end position.

In an embodiment, the diffraction grating may be moved by an actuator according to an incremental rotational movement mechanism. In an incremental translational movement mechanism, the diffraction grating may be rotatably movable in one or more increments along an arcuate path from a starting position to an ending position, and each of the increments may have a starting point and an ending point separated by an incremental arc length that is less than a total arc length between the starting position and the ending position.

In an embodiment, the diffraction grating may be moved by an actuator according to a continuous rotational movement mechanism. In the continuous rotational movement mechanism, the diffraction grating may be substantially continuously rotationally movable along an arcuate path from a start position to an end position.

In an embodiment, the steering mirror is movable by an actuator according to an incremental translational movement mechanism. In an incremental translational movement mechanism, the steering mirror may be translatably movable along a linear path from a start position to an end position in one or more increments, and each of the increments may have a start point and an end point separated by an incremental linear distance that is less than a total linear distance between the start position and the end position.

In an embodiment, the turning mirror is movable by an actuator according to a continuous translational movement mechanism. In the continuous translational movement mechanism, the steering mirror is substantially continuously translatably movable along a linear path from the start position to the end position.

In an embodiment, the steering mirror is movable by an actuator according to an incremental rotational movement mechanism. In an incremental translational movement mechanism, the steering mirror may be rotatably movable in one or more increments along an arcuate path from a starting position to an ending position, and each of the increments may have a starting point and an ending point separated by an incremental arc length that is less than a total arc length between the starting position and the ending position.

In an embodiment, the turning mirror is movable by an actuator according to a continuous rotational movement mechanism. In the continuous rotational movement mechanism, the steering mirror is substantially continuously rotatably movable along an arcuate path from the start position to the end position.

Two measurement locations within the plurality of measurement locations may be separated by a distance less than the width of a pixel.

The sensor array may be a Charge Coupled Device (CCD).

Drawings

For a fuller understanding of the nature and objects of the present invention, reference should be made to the following detailed description taken together with the accompanying figures in which:

FIG. 1 is an ideal reflectometer spectrum;

FIG. 2 is an optical point spread function;

FIG. 3 is an ideal reflectometer spectrum in which an optical point spread function is applied;

FIG. 4 is a digitized spectrum (200 to 300nm) resulting from digitizing an ideal reflectometer spectrum in which an optical point spread function is applied;

FIG. 5 is a reflectometer point spread function at pixel resolution;

FIG. 6 is a recovered digitized spectrum of a point spread function at deconvolution pixel resolution;

FIG. 7 is a spectrometer with a sensor mounted to a stage;

FIG. 8 is an actuatable stage;

FIG. 9 is an actuatable steering mirror;

FIG. 10 is an actuatable diffraction grating;

FIG. 11 is an embodiment method 1100 of acquiring a radiation spectrum;

FIG. 12 is an embodiment method 1200 of processing a radiation spectrum;

FIG. 13 is a 10 sample spectrum interleaved;

FIG. 14 is a 10x point spread function at 10x pixel resolution;

FIG. 15 is a 10x spectrum of a point spread function at 10x pixel resolution where deconvolution is performed;

FIG. 16 is a comparison of a 1x recovered spectrum and a 10x recovered spectrum;

FIG. 17 is a comparison of a 1x recovered spectrum and a 2x recovered spectrum;

FIG. 18 is a comparison of a 1x recovered spectrum and a 4x recovered spectrum;

FIG. 19 is a comparison of a 1x recovered spectrum and an 8x recovered spectrum;

FIG. 20 is a comparison of a 1x recovered spectrum and a 16x recovered spectrum; and

fig. 21 is a revised comparison of the 1x recovered spectrum and the 4x recovered spectrum.

Detailed Description

Although claimed subject matter will be described in terms of certain embodiments, other embodiments that include embodiments that do not provide all of the benefits and features set forth herein are also within the scope of this disclosure. Various structural, logical, process step, and electrical changes may be made without departing from the scope of the present invention. The scope of the invention is, therefore, defined only by reference to the appended claims.

Ranges of values are disclosed herein. The range defines a lower limit and an upper limit. Unless otherwise stated, the ranges include all values of the magnitude of the minimum value (lower or upper value) and ranges between the values of the ranges.

Embodiments disclosed herein address the challenges of thick film measurements, including measurements of three-dimensional flash (3D flash) film stacks. Improvements in the measurement of thin film, grating and CD structures may also be achieved using embodiments of the present invention. The techniques, methods, and apparatus disclosed herein may be implemented in both reflectometric and ellipsometer measurement systems, as well as in other suitable metrology systems.

Embodiments of the metrology tool may include: an illumination system that illuminates a target; a collection system that captures relevant information provided by (or lack of) interaction of the lighting system with a target, device, or feature; and a processing system that analyzes the collected information using one or more algorithms. Metrology tools may be used to measure structures and material characteristics associated with various semiconductor fabrication processes, such as material composition of structures and films, dimensional characteristics (e.g., film thickness and/or critical dimensions of structures, overlay, etc.). These measurements may be used to facilitate process control and/or yield efficiency in the manufacture of semiconductor dies.

A metrology tool in accordance with embodiments of the present disclosure may include one or more hardware configurations that may be used in conjunction with certain embodiments of the present disclosure, for example, to measure various aforementioned semiconductor structure and material characteristics. Examples of such hardware configurations include, among others: (1) spectroscopic Ellipsometer (SE); (2) SE with multiple illumination angles; (3) measuring SE of mueller matrix elements (e.g., using rotation compensator (s)); (4) a single wavelength ellipsometer; (5) beam profile ellipsometers (angle-resolved ellipsometers); (6) beam profile reflectometers (angle resolved reflectometers); (7) broadband reflectance spectrometers (spectral reflectometers); (8) a single wavelength reflectometer; (9) an angle-resolved reflectometer; (10) an imaging system; and (11) a scatterometer (e.g., a speckle analyzer).

The hardware configuration may be divided into discrete operating systems. Alternatively, one or more hardware configurations may be combined into a single tool. In addition, there may be numerous optical elements, including lenses, collimators, mirrors, quarter-wave plates, polarizers, detectors, cameras, apertures, and/or light sources. The wavelength may vary from about 120nm to 3 microns. For non-ellipsometer systems, the collected signals may be polarization resolved or unpolarized. In many cases, multiple metrology tools may be used for measurements of single or multiple metrology targets.

Illumination systems according to some embodiments of the present disclosure may include one or more light sources. Such a light source may produce light having only one wavelength (i.e., monochromatic light), light having many discrete wavelengths (i.e., polychromatic light), light having multiple wavelengths (i.e., broadband light), and/or light of swept wavelengths (either continuously swept or swept between wavelengths) (i.e., tunable light sources or swept-frequency light sources). Examples of suitable light sources are: a white light source, an Ultraviolet (UV) laser, an arc or electrodeless lamp, a Laser Sustained Plasma (LSP) source, a medium ultra-high source (e.g., a broadband laser source) or a shorter wavelength source (e.g., an x-ray source), an extreme UV source, or some combination thereof. The light source may also be configured to provide light having sufficient brightness, which in some cases may be a brightness greater than about 1W/(nm cm2 Sr). The metrology system may also include fast feedback to the light source for stabilizing the power and wavelength of the light source. The output of the light source may be delivered via free space propagation or, in some cases, via any type of optical fiber or light guide.

Metrology tools may be designed to perform many different types of measurements related to semiconductor manufacturing. Certain embodiments of the present invention may be applied to such measurements. For example, in some embodiments, the tool may measure characteristics of one or more targets, such as critical dimensions, overlay, sidewall angle, film thickness, process-related parameters (e.g., focus and/or dose). The target may include a particular region of interest that is periodic in nature (e.g., such as a raster in a memory die, for example). The target may comprise a plurality of layers or films whose thicknesses may be measured by the metrology tool. The target may comprise a target design placed on (or already existing) a semiconductor wafer for use, for example, using alignment and/or overlay registration operations. Specific targets may be positioned at various locations on a semiconductor wafer. For example, the target may be positioned within a scribe lane (e.g., between dies) and/or in the die itself. In some embodiments, multiple targets may be measured by the same or multiple metrology tools (at the same time or at different times). Data from such measurements may be combined. Data from the metrology tool may be used in a semiconductor manufacturing process, for example, for feed-forward, feed-back, and/or feed-side corrections to the process (e.g., lithography, etch), and thus a complete process control solution may be generated.

Fig. 1-6 graphically show an exemplary process of signal reconstruction. Fig. 1 shows an ideal spectrum as a ray of light received from a wafer as by an exemplary reflectometer. FIG. 2 shows the optical PSF for the optics of the exemplary reflectometer. As the ray passes through the reflectron, the ideal spectrum shown in fig. 1 is convolved with the optical PSF shown in fig. 2, resulting in the convolved (blurred) spectrum shown in fig. 3. This blurred spectrum is a digitally blurred spectrum shown in fig. 4 that is digitized or quantized when the rays that have passed through the optics of the reflectometer are incident on the sensor pixels. A digital point spread function (shown in fig. 5) matching its resolution is deconvolved from the digital blurred spectrum of fig. 4 to recover a deconvolved digital spectrum compared to that shown for the original ideal spectrum in fig. 6.

As can be observed in the recovered spectrum depicted in fig. 6, this approach does not sufficiently recover the original spectrum.

One embodiment of the present invention addresses this problem by mounting the sensor array to a high precision motion stage. The motion stage may then translate or rotate the sensor array along the wavelength axis of the illuminating rays. In other embodiments of the invention, the sensor array is mounted to a fixed stage, and the turning mirror or diffraction grating is translated or rotated to modify the incidence of the illuminating radiation.

FIG. 7 depicts an exemplary embodiment of a variable resolution spectrometer 700 according to the present invention. The variable resolution spectrometer 700 may include an optical system that may include an aperture stop 701, a diffraction grating 702, a focusing lens 703, a turning mirror 704, an order-selecting filter 705, and a stage 707. The sensor array 706 may be mounted to a stage 707. The sensor array 706 may be in communication with a processor 708. Such communication may be via a communication link, which may be embodied as any suitable means, such as a digital signal carrier line or other suitable means, whether wired or wireless. This communication link may be digital or analog. In some embodiments, the communication link is a wired Ethernet link via TCP/IP. In some embodiments, an analog/digital signal converter is employed.

In the resting state, the aperture stop 701 may be positioned such that it receives rays 709 from the wafer. The aperture stop 701 may block a portion of the rays 709 and may allow a portion of the rays 709 to pass through to the diffraction grating 702. At the diffraction grating 702, the rays 709 may be decomposed into their respective component wavelengths and directed toward the focusing lens 703. At focusing lens 703, rays 709 may be focused at sensor array 706. After passing through the focusing lens 703, the ray 709 may pass through a turning mirror 704, then through an order selection filter 705. Ray 709, after having passed through the optical assembly, may be incident on a sensor 706 mounted to stage 707. At the sensor 706, the radiation may be sensed and converted to an electrical signal, which may then be sent to the processor 708.

The aperture stop 701 may be configured to allow only a portion of the rays 709 to pass therethrough into the rest of the optical system. The aperture stop 701 may be a fixed or variable aperture stop or diaphragm.

The diffraction grating 702 may be configured to diffract incident radiation 709 into its component wavelengths. The diffraction grating 702 can also be positioned such that the optical axis is directed toward the rest of the optical system (e.g., starting with the focusing lens 703). In one embodiment, the diffraction grating 702 is angled such that the diffraction grating rear optical axis is offset by ninety degrees relative to the diffraction grating front optical axis. In some embodiments, the diffraction grating rear optical axis is selected based on the desired packaging of the system 700.

Order selection filter 705 may be configured to selectively block diffraction orders greater than, for example, one. In some embodiments, for example, when a 200nm component of light incident on diffraction grating 702 produces multiple diffraction orders, order-selection filter 705 allows only the first diffraction order of the 200nm component of diffracted light to pass through to the pixel(s) of sensor array 706 that receive the 200nm light.

Stage 707 may be positioned such that the diffraction grating back optical axis is normal to stage 707 in the example. Alternatively, stage 707 may be positioned such that the diffraction grating rear optical axis is collinear with an axis passing therethrough.

In an embodiment, sensor array 706 includes a plurality of pixels. The pixels may include sub-pixels. The pixels may be elliptical or rectangular. In the case of an oval or circular pixel, the pixel width may be defined as a chord, which in the case of an oval may be the major or minor axis, or in the case of a circle may be the diameter. In the case of a rectangular or square pixel, the pixel width may be defined as a line segment that intersects two different edges of the rectangular or square pixel. In any case, the pixel width may be a line segment intersecting the outermost perimeter of the pixel at two distinct points: a starting point and an end point.

The pixels of sensor array 706 are arranged in a plurality of pixel columns, with each pixel column having at least one pixel. This arrangement may form columns of rows of pixels in sensor array 706. In the case where sensor array 706 is a one-dimensional sensor or a linear sensor, sensor array 706 may have n columns of rows, each row having one pixel, forming an n x 1 pixel array. In the case where sensor array 706 is a two-dimensional sensor, sensor array 706 may have n columns of m pixels, forming an n xm pixel array.

The sensor array 706 may be embodied as a Charge Coupled Device (CCD). Alternatively, sensor array 706 may be embodied as another type of image sensor, such as a Complementary Metal Oxide Semiconductor (CMOS) or N-type metal oxide semiconductor (NMOS) chip or an active pixel sensor in a flat panel detector.

Each ray of rays 709 may impinge upon sensor array 706 at an incident point and at an incident angle by virtue of being incident. The incidence of each ray may be described by a location and an angle of incidence.

Fig. 8 depicts an embodiment of the invention in which actuator 801 is operably connected to stage 707 through drive linkage 802. In this embodiment, stage 707 is a driven component.

FIG. 9 depicts an embodiment of the invention in which an actuator 901 is operably connected to a steering mirror 704 through a drive linkage 902. In this embodiment, the steering mirror 704 is a driven component.

Fig. 10 depicts an embodiment of the invention in which an actuator 1001 is operably connected to a diffraction grating 702 through a drive linkage 1002. In this embodiment, the diffraction grating 702 is a driven component.

In the embodiments according to fig. 7 to 10, the driven component (stage 707, diffraction grating 702 or steering mirror 704) is driven in an incremental movement mechanism by an actuator 801, 901 or 1001, respectively. In these embodiments, the stage 707, the diffraction grating 702, or the turning mirror 704 are initially positioned at a nominal home position where the diffraction grating back optical axis intersects the sensor array 706 at a starting position. The sensor array 706 acquires data at the measurement location for a fixed exposure time in an acquisition step. The data is then transferred to processor 708 and stored in a storage step. Stage 707, diffraction grating 702, or steering mirror 704 may then be moved translationally or rotationally such that the rear optical axis of the diffraction grating that intersects sensor array 706 has changed by a fractional amount of the pixel width. The acquiring, storing, and moving steps are then repeated until a fixed number of repetitions have been achieved in some embodiments. In other embodiments, the acquiring, storing, and moving steps are then repeated until the intersection of sensor array 706 and the rear optical axis of the diffraction grating has moved to an end position (e.g., the entire pixel width relative to its original position). In some embodiments, the fractional amount of the pixel width is one tenth of the pixel and the number of repetitions is ten.

In other embodiments according to fig. 7 to 10, the driven component (stage 707, diffraction grating 702 or steering mirror 704) is driven by an actuator 801, 901 or 1001, respectively, in a continuous movement mechanism. In this embodiment, the stage 707, the diffraction grating 702, or the turning mirror 704 are initially positioned at a nominal home position. The sensor array 706 acquires data at the initial measurement position for a fixed exposure time in an initial acquisition step. The stage 707, the diffraction grating 702, or the turning mirror 704 are initially substantially continuously translationally or rotatably movable. The sensor array 706 acquires data at a defined fraction of the pixel width (each a measurement location) in a moving acquisition step for a fixed exposure time. The data is then transferred to processor 708 and stored in a storage step. The acquiring and storing steps in the motion are then repeated until a fixed number of iterations have been achieved in some embodiments. In other embodiments, the in-motion acquisition and storage steps are then repeated until the intersection of sensor array 706 and the diffraction grating rear optical axis has moved to an end position (e.g., the entire pixel width relative to its original position). In some embodiments, the number of repetitions is ten.

The number of measurements (Φ) is defined based on how many measurements are made between the start and end positions, e.g., the number of measurements made within a pixel. For example, a typical Φ can be 2, 4, 8, 10, 16, or another integer. The number of measurements, the starting position and the ending position may be used to determine the number of measurements in a plurality of measurement positions.

In some embodiments, the fractional amount of the pixel width is less than one pixel width (e.g., one tenth of the pixel width). In other embodiments, the fractional amount of the pixel width is greater than one pixel width.

Actuators 801, 901, and 1001 may be embodied as, among other things, piezoelectric actuators, servomotors, or stepper motors capable of sub-micron movement or positioning. The drive linkages 802, 902, and 1002 may be embodied as any means for transmitting an actuation force from an actuator to cause appropriate translation or rotation of a driven component. For example, a piezoelectric actuator may be used to actuate a driven component via a direct drive linkage to translate the driven component or to actuate the driven component via a cam drive linkage to rotate the driven component. In another example, a servo motor or stepper motor is operably connected to the driven component through a drive linkage embodied as a belt, rack and pinion, or cam to translate the driven component, or through a drive linkage embodied as a shaft that may be connected to a gearbox to rotate the driven component.

FIG. 11 shows an embodiment method 1100 of acquiring data in the form of a ray spectrum using optical system 700. In step 1101, providing an optical system comprising an aperture stop, a diffraction grating, a focusing lens, a turning mirror, an order selection filter; and an actuator, a stage, and a sensing array. At step 1102, a scan operation is performed to acquire scan data. The scan operation may include: moving one of the stage, the diffraction grating, or the turning mirror using an actuator according to a movement mechanism to change incidence of the rays on the stage, the movement mechanism having a start position and an end position; and sensing radiation incident on the sensor array from an optical system at a plurality of measurement locations using a sensor array comprising a plurality of pixel columns (each pixel column having at least one pixel) disposed on the stage to obtain a plurality of radiation spectra.

FIG. 12 shows an embodiment method 1200 of acquiring and processing data received in the form of a ray spectrum received by processor 708. At step 1201, a spectrum of radiation is acquired using an optical system and sensor array as described herein. In some embodiments of method 1200, a radiation spectrum is acquired according to method 1100. At step 1202, a radiation spectrum is received by processor 708. At step 1203, the radiation spectra are interleaved to produce an interleaved spectrum representing a resolution multiplier of the sensor array. This interleaved spectrum is shown, for example, for Φ ═ 10 in fig. 13. In fig. 13, a gap is shown for each measurement location in the interlace. The point spread function (also representing the resolution multiplier) corresponding to the optical system, which is exemplary for Φ -10 in fig. 14, is the deconvolved interleaved spectrum that produces the recovered digitized spectrum, step 1204. The recovered digitized spectrum is at a resolution higher than the actual resolution of the sensor array. For example, the recovered digitized spectrum at Φ -10 is shown compared to its original reflectometer ideal spectrum in fig. 15.

For example, interleaving based on Φ -4 may involve specifying fourMeasurement A₁To A₄Each of the above. Each measurement may have N pixels, so the individual pixels in the acquisition "X" may be labeled A_X,1To A_X,N. With these 4 acquisitions of N pixels, the interleaved spectrum may then have 4x N pixels, which include pixels: a. the_1,1、A_1,2、A_1,3、A_1,4、…、A_N,1、A_N,2、A_N,3、A_N,4。

In an embodiment of the invention, the radiation spectrum is acquired on the basis of ten measurement points per pixel or Φ — 10.

Processor 708 may be embodied as a computer subsystem including a processor and an electronic data storage unit. Processor 708 may include a microprocessor, microcontroller, or other device.

Processor 708 may be coupled to sensor array 706 in any suitable manner (e.g., via one or more transmission media, which may include wired and/or wireless transmission media) such that processor 708 may receive an output. Processor 708 may be configured to perform a number of functions using the output. System 700 may receive instructions or other information from processor 708. Processor 708 may optionally be in electronic communication with another wafer inspection tool, wafer metrology tool, or wafer inspection tool (not illustrated) to receive additional information or send instructions. For example, the processor 708 may be in electronic communication with a scanning electron microscope.

The processor 708, other system(s), or other subsystem(s) described herein may be part of various systems, including a personal computer system, image computer, mainframe computer system, workstation, network appliance, internet appliance, or other device. The subsystem or system may also include any suitable processor, such as a parallel processor. Additionally, the subsystem or system may include a platform with high speed processing and software as a stand-alone or networked tool.

Processor 708 may be disposed in or otherwise as part of system 700 or another device, respectively. In an example, the processor 708 may be part of a stand-alone control unit or in a centralized quality control unit. Multiple processors 708 may be used.

Processor 708 may be implemented by virtually any combination of hardware, software, and firmware. In addition, its functions as described herein may be performed by one unit, or distributed among different components (each of which may in turn be implemented by any combination of hardware, software, and firmware). Program code or instructions that cause the processor 708 to perform the various methods and functions may be stored in a readable storage medium, such as memory in an electronic data storage unit or other memory.

If system 700 includes more than one processor 708, the different subsystems may be coupled to each other so that images, data, information, instructions, etc., may be sent between the subsystems. For example, one subsystem may be coupled to additional subsystem(s) by any suitable transmission medium, which may include any suitable wired and/or wireless transmission medium. Two or more of such subsystems may also be operatively coupled by a shared computer-readable storage medium (not shown).

The processor 708 may be configured to perform a number of functions using the output of the system 700 or other outputs, respectively. For example, the processor 708 may be configured to send the output to an electronic data storage unit or another storage medium. The processor 708 may be further configured as described herein.

Processor 708 may be part of a defect inspection system, an inspection system, a metrology system, or some other type of system. Thus, embodiments disclosed herein describe some configurations that can be customized in many ways for systems with different capabilities that are more or less suited for different applications.

If a system includes more than one subsystem, the different subsystems may be coupled to each other so that images, data, information, instructions, etc., may be sent between the subsystems. For example, one subsystem may be coupled to additional subsystem(s) by any suitable transmission medium, which may include any suitable wired and/or wireless transmission medium. Two or more of such subsystems may also be operatively coupled by a shared computer-readable storage medium (not shown).

The processor 708 may be configured in accordance with any of the embodiments described herein. Processor 708 can also be configured to perform other functions or additional steps using the output of system 700 or using images or data from other sources, respectively.

Processor 708 may be communicatively coupled to any of the various components or subsystems of system 700, respectively, in any manner known in the art. Further, the processor 708 may be configured to receive and/or acquire data or information (e.g., inspection results from an inspection system such as an inspection tool, a remote database including design data, and the like) from other systems over a transmission medium that may include wired and/or wireless portions. In this manner, the transmission medium may serve as a data link between processor 708 and other subsystems of system 700, or processor 708 and systems external to system 700, respectively.

The processor 708 is in electronic communication with a metrology tool or an inspection tool (e.g., system 700). For example, the processor 708 may be configured to perform an embodiment of the method 1100.

Additional embodiments relate to a non-transitory computer-readable medium storing program instructions executable on a controller for performing a computer-implemented method as disclosed herein. In particular, as shown in fig. 7, processor 708 may include an electronic data storage unit or other storage medium that may contain a non-transitory computer-readable medium including program instructions that are executable on processor 708. The computer-implemented method may include any step(s) of any method(s) described herein, including method 1100.