阅读说明：本技术 红外干涉仪的标准片的制备方法、标准片、以及全局校准方法 (Preparation method of standard plate of infrared interferometer, standard plate and global calibration method ) 是由 张硕 屠礼明 于 2021-01-18 设计创作，主要内容包括：本发明提供了一种红外干涉仪的标准片的制备方法、标准片、以及全局校准方法。所述标准片包括：一硅衬底；一隔离结构,所述隔离结构位于硅衬底表面；一金属反射结构,所述金属反射结构位于所述隔离结构内,为平行排列且尺寸连续变化的金属柱；以及一透明保护层,所述透明保护层覆盖在隔离结构和金属反射结构的上方。本发明通过采用不同反射频率的标准片以及红外干涉仪的全局校准方法,解决了光学测量机台测量程序偏移值处理困难的问题。(The invention provides a preparation method of a standard plate of an infrared interferometer, the standard plate and a global calibration method. The standard sheet includes: a silicon substrate; the isolation structure is positioned on the surface of the silicon substrate; the metal reflecting structure is positioned in the isolating structure and is a metal column which is arranged in parallel and continuously changes in size; and the transparent protective layer covers the isolation structure and the metal reflection structure. The invention solves the problem of difficult processing of the offset value of the measurement program of the optical measurement machine by adopting the standard sheets with different reflection frequencies and the global calibration method of the infrared interferometer.)

1. A preparation method of a standard plate of an infrared interferometer is characterized by comprising the following steps:

providing a silicon substrate;

forming an isolation layer on the surface of the silicon substrate;

etching the isolation layer to form isolation structures with trenches of different sizes;

filling a metal material in the isolation structure to form a metal material layer;

thinning the metal material layer to form a metal reflection structure which is flush with the isolation structure;

and depositing a transparent protective layer on the thinned surface.

2. The method of claim 1, wherein the isolation layer is a stacked structure formed by stacking silicon oxide and silicon nitride.

3. The method of claim 1, wherein the isolation layer is a pure silicon oxide layer.

4. The method of claim 1, wherein the channels are columnar, parallel and continuously variable in size.

5. The method of claim 1, wherein the etching method further comprises the steps of:

forming a graphical mask layer on the surface of the isolation layer;

etching the isolation layer to form isolation structures with trenches of different sizes;

and removing the mask layer.

6. The method of claim 1, wherein the metallic material layer is one of W, Al, Cu, and Ti.

7. The method of claim 1, wherein the thinning process is a chemical mechanical polishing or etching process.

8. The method of claim 1, wherein the transparent protective layer is a silicon oxide material.

9. A reticle for an infrared interferometer, the reticle comprising:

a silicon substrate;

the isolation structure is positioned on the surface of the silicon substrate;

the metal reflecting structure is positioned in the isolating structure and is a metal column which is arranged in parallel and continuously changes in size;

and

and the transparent protective layer covers the isolation structure and the metal reflection structure.

10. The reticle of claim 9 wherein the isolation structures are formed by trench etching a stack of silicon oxide and silicon nitride stacks.

11. The reticle of claim 9 wherein the isolation structure is made of pure silicon oxide.

12. The master plate of claim 9, wherein the material of the metallic reflective structure is selected from one of the metals W, Al, Cu, and Ti.

13. The master plate of claim 9, wherein the transparent protective layer is made of a silicon oxide material.

14. A global calibration method of an infrared interferometer is characterized by comprising the following steps:

providing a standard sheet, wherein the structure of the standard sheet comprises: a silicon substrate; the isolation structure is positioned on the surface of the silicon substrate; the metal reflecting structure is positioned in the isolating structure and is a metal column which is arranged in parallel and continuously changes in size; the transparent protective layer covers the isolation structure and the metal reflection structure;

calibrating the reflectivity of the standard sheet under different frequencies;

obtaining a linear calibration relationship at a single wave number according to a plurality of discrete reflectivity-intensity data points;

linearly arranging all different reflectivity-light intensity according to wave number to form a new calibration file;

and performing polynomial fitting and matching the interpolation to ensure that the wave number resolution of the new calibration file is matched with that of the machine calibration file.

15. The method of claim 14, wherein the calibration method uses measurements of metal volume fraction or absorption coefficient.

Technical Field

The invention relates to the field of semiconductors, in particular to a preparation method of a standard plate of an infrared interferometer, the standard plate and a global calibration method.

Background

In the prior art, the most important structure channel hole in the memory core area of the 3D NAND device requires extremely high process precision and aspect ratio, and the etching of the most important structure channel hole requires an amorphous carbon film using a diamond-like carbon material, which is called kodialk. The kodialk has a very high extinction coefficient in a wave band near visible light, and a traditional elliptical polarization optical machine using visible light and a near infrared wave band cannot directly measure the kodialk. In order to realize the online nondestructive monitoring of the kodialk thickness, a production line introduces an optical measuring machine based on the Michelson interference principle and using middle and far infrared waveband detection light with the wavelength of 900-.

When the current machine is used for calibrating the measured light intensity signal and the reflectivity, a simple linear hypothesis is used by taking a monocrystalline silicon or Ti metal film mark as a reference, and experience actually proves that the linear hypothesis is not completely consistent in a full wave band. This coarse calibration results in different offsets to the actual measurements of different films, which results in different offset values being added when the current tool measurement process is matched across tools. In a large-scale mass production with multiple stations and a large number of measurement programs, the processing method brings huge workload and multiple potential risks to practical management and control.

Disclosure of Invention

The invention aims to solve the technical problem that the offset value of a measuring program of an optical measuring machine is difficult to process, and provides a preparation method of a standard sheet of an infrared interferometer, the standard sheet and a global calibration method.

In order to solve the problems, the invention provides a preparation method of a standard plate of an infrared interferometer, which comprises the following steps: providing a silicon substrate; forming an isolation layer on the surface of the silicon substrate; etching the isolation layer to form isolation structures with trenches of different sizes; filling a metal material in the isolation structure to form a metal material layer; thinning the metal material layer to form a metal reflection structure which is flush with the isolation structure; and depositing a transparent protective layer on the thinned surface.

In order to solve the above problems, the present invention also provides a standard plate of an infrared interferometer, comprising: a silicon substrate; the isolation structure is positioned on the surface of the silicon substrate; the metal reflecting structure is positioned in the isolating structure and is a metal column which is arranged in parallel and continuously changes in size; and the transparent protective layer covers the isolation structure and the metal reflection structure.

In order to solve the above problem, the present invention further provides a global calibration method for an infrared interferometer, comprising the following steps: providing a standard sheet, wherein the structure of the standard sheet comprises: a silicon substrate; the isolation structure is positioned on the surface of the silicon substrate; the metal reflecting structure is positioned in the isolating structure and is a metal column which is arranged in parallel and continuously changes in size; and the transparent protective layer covers the isolation structure and the metal reflection structure. Calibrating the reflectivity of the standard sheet under different frequencies; obtaining a linear calibration relationship at a single wave number according to a plurality of discrete reflectivity-intensity data points; linearly arranging all different reflectivity-light intensity according to wave number to form a new calibration file; and performing polynomial fitting and matching the interpolation to ensure that the wave number resolution of the new calibration file is matched with that of the machine calibration file.

The invention solves the problem of difficult processing of the offset value of the measurement program of the optical measurement machine by adopting the standard sheets with different reflection frequencies and the global calibration method of the infrared interferometer.

Drawings

FIG. 1 is a schematic diagram illustrating the steps of one embodiment of the present invention.

FIGS. 2A-2F are schematic views of the process of steps S10-S15 shown in FIG. 1.

Fig. 3 is a schematic diagram illustrating steps of an etching method according to an embodiment of the invention.

FIGS. 4A-4C are schematic views of the process of steps S31-S33 shown in FIG. 3.

FIG. 5 is a scanning electron micrograph of a surface of a master wafer according to an embodiment of the present invention.

Fig. 6 is a schematic diagram illustrating steps of a global calibration method according to an embodiment of the present invention.

Detailed Description

The following describes in detail a specific embodiment of the standard sheet provided by the present invention with reference to the accompanying drawings.

FIG. 1 is a schematic diagram illustrating the steps of an embodiment of the present invention, including: step S10, providing a silicon substrate; step S11, forming an isolation layer on the surface of the silicon substrate; step S12, etching the isolation layer to form isolation structures with channels of different sizes; step S13, filling a metal material in the isolation structure to form a metal material layer; step S14, thinning the metal material layer to form a metal reflection structure flush with the isolation structure; step S15, depositing a transparent protection layer on the thinned surface.

Referring to step S10, shown in fig. 2A, a silicon substrate 20 is provided. In one embodiment, the silicon substrate 20 may be directly formed as a finished wafer, thereby reducing the manufacturing cost.

Referring to step S11, as shown in fig. 2B, an isolation layer 21 is formed on the surface of the silicon substrate 20. In a specific embodiment, the isolation layer 21 is a stacked structure formed by stacking a silicon oxide 201 and a silicon nitride 202. In yet another specific embodiment, the isolation layer 21 is a pure silicon oxide layer. In addition, other suitable dielectric film material layers may be used for the isolation layer 21.

Referring to step S12, as shown in fig. 2C, the isolation layer 21 is etched to form isolation structures 22 having trenches with different sizes. The channels are columnar, parallel and continuously variable in size. The range conveniently realized in the current process flow is that the diameter of the channel is continuously changed within the range of 50nm-120nm, but the size of the etching structure is not limited to 50nm-120 nm. The depth and diameter of the etch will collectively determine the dimensions of the subsequent metallic reflective structure 205. In one embodiment, the etching method uses an existing photolithography process and a photomask.

For embodiments in which the trench depth is greater than 5 μm, the etching method further comprises the steps of: step S31, forming a patterned mask layer on the surface of the isolation layer; step S32, etching the isolation layer to form isolation structures with channels of different sizes; step S33, removing the mask layer.

Referring to step S31, as shown in fig. 4A, a patterned mask layer 203 is formed on the surface of the isolation layer 21. In a specific embodiment, the mask layer 203 is made of an amorphous carbon material.

Referring to step S32, as shown in fig. 4B, the isolation layer 21 is etched to form isolation structures 22 having trenches with different sizes. The channels are columnar, parallel and continuously variable in size.

Referring to step S33, the mask layer 203 is removed as shown in fig. 4C.

After the above steps are completed, the structure shown in fig. 2C is obtained. On the basis, the following steps are carried out continuously.

For embodiments in which the trench depth is less than or equal to 5 μm, the above steps of forming and removing the mask layer may be omitted, i.e., the isolation layer 21 is directly etched followed by the following steps.

Referring to step S13, as shown in fig. 2D, a metal material is filled in the isolation structure 22 to form a metal material layer 204. The metal material layer 204 is made of one of metals W, Al, Cu, and Ti. In order to obtain the maximum reflectivity variation in the whole wavelength band, in a specific embodiment, the metal material layer 204 is made of metal W.

Referring to step S14, as shown in fig. 2E, the metal material layer 204 is thinned to form a metal reflective structure 205 flush with the isolation structure 22, where the metal reflective structure 205 is used for reflecting infrared light. In a specific embodiment, the thinning method adopts a chemical mechanical polishing or etching process. Since the size of the metal reflective structure 205 is continuously changed, that is, the volume of the W metal pillar is continuously changed, the continuous change of the full-band reflectivity can be realized.

Referring to step S15, a transparent protection layer 206 is deposited on the thinned surface as shown in fig. 2F. In one embodiment, the transparent protection layer 206 is made of silicon oxide material to improve the long-term stability of the standard sheet.

Next, a specific implementation of the standard plate of the infrared interferometer obtained after the above steps are performed is given with reference to the accompanying drawings, and the structure of the standard plate is shown in fig. 2F, and includes: a silicon substrate 20; an isolation structure 22, wherein the isolation structure 22 is located on the surface of the silicon substrate 20; a metal reflective structure 205, wherein the metal reflective structure 205 is located inside the isolation structure 22 and is a metal pillar with parallel arrangement and continuously variable size; and a transparent protection layer 206, wherein the transparent protection layer 206 covers the isolation structure 22 and the metal reflection structure 205.

In a specific embodiment, the isolation structure 22 is formed by performing a trench etching on a stacked structure formed by stacking a silicon oxide 201 and a silicon nitride 202. In a specific embodiment, the material of the isolation structure 22 is pure silicon oxide.

In a specific embodiment, the material of the metal reflective structure 205 is selected from one of W, Al, Cu, and Ti, and the transparent protection layer 206 is made of a silicon oxide material.

In order to better illustrate the structure of the standard plate, a scanning electron microscope image of the surface of the standard plate is given. FIG. 5 is a scanning electron micrograph of the surface of the master plate according to an embodiment of the present invention.

Fig. 6 is a schematic diagram illustrating steps of a global calibration method according to an embodiment of the present invention, including: step S60, providing a standard sheet, wherein the standard sheet has a structure including: a silicon substrate; the isolation structure is positioned on the surface of the silicon substrate; the metal reflecting structure is positioned in the isolating structure and is a metal column which is arranged in parallel and continuously changes in size; and the transparent protective layer covers the isolation structure and the metal reflection structure. Step S61, calibrating the reflectivity of the standard sheet under different frequencies; step S62, obtaining a linear calibration relation under a single wave number according to a plurality of discrete reflectivity-light intensity data points; step S63, linearly arranging all different reflectivity-light intensity according to wave number, and combining into a new calibration file; and step S64, performing polynomial fitting and matching interpolation to match the wave number resolution of the new calibration file and the machine calibration file.

In a specific embodiment, the calibration method uses measurements of metal volume fraction or absorption coefficient.

The technical scheme verifies the global error of the current calibration by using the single reflectivity standard slice; the method for using different linear calibrations for different wave numbers is proposed and preliminarily verified in the near infrared and middle infrared bands; a manufacturing method of standard pieces with different reflectivity is provided, and through simulation verification, the reflectivity of the standard pieces can be clearly changed from near infrared to far infrared full-wave bands so as to realize full-wave band calibration. The current on-line mature process and the photomask can be used, and no additional new process is needed; the continuous change of the full-wave-band reflectivity can be realized by using one wafer, and solid and rich data are provided for the overall calibration of the machine. A plurality of standard sheets are prepared according to the method, and are embedded on a wafer platform in a machine after being cut, so that the method can be applied to machine equipment to achieve the purpose of simplifying the measurement process.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.