CN114280009A - A comprehensive defect detection device and method for silicon carbide wafers - Google Patents

Abstract

The invention discloses a comprehensive defect detection device and method for silicon carbide wafers, which simply adopts an optical detection method with an automatic focusing function, and can simultaneously detect various defects on the front, back and inside of a silicon carbide wafer through multi-photosynthesis; Algorithmic programs automatically identify and collect statistical information on various defects in SiC wafers. By adopting the invention, various defects of silicon carbide wafers can be quickly and accurately identified and counted automatically, and various defects can be accurately located, which is convenient for wafer quality analysis.

Description

A comprehensive defect detection device and method for silicon carbide wafers

technical field

The invention relates to the technical field of silicon carbide, in particular to a comprehensive defect detection device and method for silicon carbide wafers.

Background technique

Silicon carbide has a wide band gap, high thermal conductivity, and high breakdown voltage, making it widely used in devices that work under high frequency, high power, radiation resistance, and extreme conditions. It is a potential semiconductor material.

Defect-free silicon carbide wafers are critical to the fabrication of high-quality epitaxial wafers, which in turn determine the performance of semiconductor devices. Common silicon carbide wafer defects include micropipes, pits, scratches, edge chipping, miscellaneous crystals, and wrapping. Therefore, defect detection of the produced silicon carbide wafers is an important step to ensure the qualified quality of silicon carbide products.

In recent years, people have mastered a variety of methods for detecting defects of silicon carbide wafers. Generally, optical equipment is used to perform quality inspection on silicon carbide wafer products, so as to obtain defect information of silicon carbide wafers in time. However, most of the optical inspection equipment on the market has specificity in defect detection, that is, only one or several kinds of defects can be detected. If you want to inspect all defects of silicon carbide wafers, you need to send the wafers to different optical inspection equipment for inspection respectively, which will introduce additional time and capital cost, and easily cause scratches on the wafers when transferring the wafers, thereby reducing the quality of the wafers. And many optical inspection equipment are manual or semi-automatic, that is, after the wafer is placed in the optical instrument, it is necessary to manually find the defect position, and after the defect is found, it is necessary to manually record and process the data, which undoubtedly reduces the efficiency of wafer inspection.

SUMMARY OF THE INVENTION

In view of this, the present invention provides a comprehensive defect detection device and method for silicon carbide wafers, which can automatically detect various defects of silicon carbide wafers.

To achieve the above object, the present invention provides the following technical solutions:

A comprehensive defect detection device for silicon carbide wafers, comprising: a support mechanism and a sample stage, a light generation system and a light collection system arranged thereon;

the sample stage is used for placing wafers;

The light collection system is located on one side of the sample stage; the light collection system includes: a lens and a light source receiver;

The light generating system includes: multiple light generating mechanisms located on one side or both sides of the sample stage; the light source receiver can collect the detection light of the multiple light generating mechanisms through the lens.

Preferably, the light generating system comprises: a light reflection mechanism located on the first side of the sample stage;

The light reflection mechanism includes: a first light source and a first reflection mirror; the light of the first light source can be irradiated to the first side of the wafer through the first reflection mirror and reflected;

The light collection system is located on the first side of the sample stage, and the light source receiver can collect the reflected light of the light reflection mechanism through the lens.

Preferably, the light generating system includes: a light transmission mechanism located on the second side of the sample stage;

The transmission light mechanism includes: a second light source and a second reflection mirror; the light of the second light source can be transmitted from the second side of the wafer to the first side through the second reflection mirror;

The light collection system is located on the first side of the sample stage, and the light source receiver can collect the transmitted light of the light transmission mechanism through the lens.

Preferably, the light generating system further comprises: a light transmission polarization mechanism located on the second side of the sample stage; and the light transmission mechanism is located between the sample stage and the light transmission polarization mechanism;

The light transmission polarization mechanism includes: a polarizer, a third light source and a third mirror;

The light collection system further includes: a polarizer; the polarizer is located between the light reflection mechanism and the lens; the light source receiver can collect the transmission polarization of the light transmission polarization mechanism through the lens Light.

Preferably, the lens is an auto-focusing objective lens equipped with a ranging laser sensor and a control program, and the magnification is 1-20 times.

Preferably, the light collection system is located above the sample stage;

The lens can move up and down relative to the sample stage, and the moving speed is 0-50 mm/s, and the single acquisition field of view of the lens is 5-50 mm ² .

Preferably, the sample stage includes an automatic motion stage capable of moving within the wafer plane.

Preferably, the automatic motion platform is a magnetic drive linear motion platform, which can translate the wafer in two directions of the X axis and the Y axis.

Preferably, the moving speed of the automatic moving platform is 0-100 mm/s, and can move in a serpentine shape.

Preferably, the sample stage is provided with a hollow portion for placing the wafer, and/or the sample stage has a transparent portion for contacting the wafer.

Preferably, the edge of the hollow portion is notched.

Preferably, the transparent portion is a glass disc disposed at the four corners of the hollow portion.

Preferably, the support mechanism includes: a base and a device casing;

The comprehensive defect detection device for silicon carbide wafers further includes: a light shield provided on the equipment casing.

Preferably, it also includes: a control unit;

The comprehensive defect detection device of the silicon carbide wafer can automatically test a variety of defects on the front and back and inside of the wafer through the control unit program setting, and the defects include: front and back scratches, front and back pits, micropipes, miscellaneous crystals and collapsing edges.

A comprehensive defect detection method for silicon carbide wafers, using the above-mentioned comprehensive defect detection device for silicon carbide wafers to detect the wafers placed on the sample stage, comprising the steps of:

Collecting a plurality of detection light rays of the light generating mechanisms by the light collection system;

Defects are analyzed and identified based on the collected inspection light data.

Preferably, the collection of a plurality of detection lights of the light generating mechanism includes:

Collect the reflected light of the light reflection mechanism, the transmitted light of the light transmission mechanism and the transmitted polarized light of the light transmission polarization mechanism;

The analysis and identification of defects according to the collected detection light data includes:

The reflected light is used to detect the front surface defects of the wafer including chipping, and the transmitted light is used to detect the internal defects of the wafer including miscellaneous crystals and packages, and the transmitted polarized light is used to detect the internal stress defects of the wafer including micropipes.

Preferably, the condition for identifying edge chipping is: chip edge notch defect;

The conditions for identifying miscellaneous crystals are: there are edge defects in the bulk in transmission mode;

The condition for identifying the package is: the area where point defects gather in transmission mode;

The conditions for identifying microtubules are: similarity with butterfly shape greater than 40%, brightness greater than 200cd/m ² , light transmittance greater than 30%, and area ratio of the brightest region greater than 25%.

Preferably, the analysis and identification of defects according to the collected detection light data further includes:

If the defect is detected in the reflected light and transmitted light inspection results at the same time, the defect is on the silicon surface;

If it is only detected in the transmitted light inspection results, but not in the reflected light inspection results, the defect is on the carbon surface.

Preferably, before the collection of a plurality of detection lights of the light generating mechanisms by the light collection system, the method further includes:

First identify the edge of the wafer, then fit an edge, and judge the edge chipping position by whether there is a black concave part at the edge;

The analysis and identification of defects according to the collected detection light data includes:

Use reflected light to detect the defects on the front surface of the wafer including chipping, and judge whether the size of the chipping exceeds the set value.

Preferably, after analyzing and identifying the defect according to the collected detection light data, the method further includes:

Identify and classify defects and locate each defect.

It can be seen from the above technical solutions that the present invention provides a comprehensive defect detection device and method for silicon carbide wafers based on optical detection, and cooperates with intelligent algorithm programs to automatically identify and collect statistical information on various defects of silicon carbide wafers. By adopting the invention, various defects of silicon carbide wafers can be quickly and accurately identified and counted automatically, and various defects can be accurately located, which is convenient for wafer quality analysis.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

1 is a schematic structural diagram of a silicon carbide wafer comprehensive defect detection device provided by an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a sample stage provided by an embodiment of the present invention.

Among them, 1. base, 2. equipment shell, 3. polarizer, 4. sample stage, 5. hood, 6. polarizer, 7. lens, 8. light source receiver, 9. first light source, 10. first reflector, 11, second light source, 12, second reflector, 13, third light source, 14, third reflector, 15, automatic motion platform, 16, notch, 17, glass wafer, 18, hollow part.

Detailed ways

The invention has the advantages of simple structure, high degree of automation and strong versatility, and can accurately and quickly detect various defects in silicon carbide wafers and automatically collect defect statistics.

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The present invention adopts following technical scheme:

The utility model relates to a comprehensive defect detection device for silicon carbide wafers, which simply adopts an optical detection method and has an automatic focusing function. From bottom to top, it includes a base 1, an equipment housing 2, a sample stage 4, three light sources, a lens, a light source receiver and a control unit. The optical system detects wafers using reflected light, transmitted light, and transmitted polarized light. The detection light source forms an image through a polarizer, a lens and a charge-coupled device. The resulting images are then analyzed using an intelligent algorithmic program to obtain statistical data on different types of defects.

The optical devices below the sample stage are the third light source 13 and the third reflecting mirror 14 , the polarizer 3 , the second light source 11 and the second reflecting mirror 12 in order from bottom to top. The optical devices above the sample stage are, from bottom to top, a first light source 9 and a first reflector 10 , a polarizer 6 , a lens 7 and a light source receiver 8 .

The base 1 and the equipment shell 2 are responsible for supporting the comprehensive defect detection equipment for silicon carbide wafers, and are equipped with a light shield 5, which is responsible for eliminating interference from external light sources when detecting wafers.

The sample stage is equipped with a magnetically driven linear automatic motion platform 15, which can translate the sample in both directions of the X-axis and the Y-axis. The movement speed is 0-60mm/s. The path is continuously serpentine and scans line by line, and the acquisition range covers the entire wafer, ensuring that every part of the wafer can be detected. 1. The space occupied by the sample stage is 724*827mm.

There is a circular hollow part 18 in the middle of the sample table, which is responsible for placing the wafer, so that different light sources can detect wafer defects from above or below the wafer; there is a transparent circular glass sheet 17 at each of the four corners of the hollow part to support the wafer and not block the detection light. Edge defects can also be accurately detected. The hollow portion is edged with notches 16 to allow the operator to use a stylus to pick and place the test wafer.

The light source adopts a combination of three light sources, and the wavelengths of the three light sources are 450-480 nm. The first light source is located directly above the sample stage, which is a reflective light source and is equipped with a reflector. The polarizer is connected above the first light source, and the reflected light passes through the polarizer and then goes up to a lens, which reaches the light source receiver after passing through the lens; The light source is located directly under the sample stage, which is a transmission light source. The transmitted light emitted by the second light source first passes through the sample from bottom to top, then passes through the polarizer and the lens in sequence, and finally reaches the light source receiver; the third light source is located directly behind the second light source. Below, this is the transmission light source. A polarizer is provided between the second light source and the third light source. The transmitted light emitted by the third light source first passes through the polarizer to become polarized transmission light, and then passes through the sample, the test polarization from bottom to top. The receiver and lens finally reach the light source receiver.

As shown in FIG. 1 , the optical system of the three light sources includes a first light source 9 and a first reflection mirror 10 above the sample stage, which provide reflected light to detect the wafer. The light is irradiated onto the wafer through the mirror and reflected upward, so that the reflected light is used to detect the defects on the front surface of the substrate including chipping of the wafer.

The optical system of the three light sources includes a second light source 11 and a second mirror 12 above the sample stage, providing transmitted light to detect the wafer. The light is transmitted from the lower surface of the wafer to the upper side of the wafer through the mirror, so that the transmitted light is used to detect the internal defects of the wafer and the encapsulation.

The optical system of the three light sources includes a third light source 13, a third mirror 14 and a polarizer 3 below the second light source, and provides a transmitted polarized light detection wafer. The light is irradiated to the lower surface of the wafer through the third mirror 14, and polarized light is formed in the middle through the polarizer 3, and then transmitted from the lower surface of the wafer to the upper surface of the wafer, so as to realize the detection of the internal stress of the wafer including the micropipes by the transmitted polarized light. defect.

The comprehensive defect detection device for silicon carbide wafers combines the data of transmitted light and reflected light for comprehensive analysis, and can identify scratches and pits on the front and back of the wafer.

Above the first light source are a polarizer, a lens and a light source receiver. All three light sources generate detection light in an upward direction: reflected light, transmitted light, and transmitted polarized light. Silicon carbide wafers are generated through the polarizer, lens and light source receiver. Comprehensive defect detection pictures.

All detection light sources will eventually enter the lens 7 and the light source receiver 8, generate detection pictures, and transmit the detection data and results to the computer for automatic processing. The lens of the invention does not use an eyepiece, and the magnification of the objective lens used is 1-20 times. When testing the wafer, the objective lens can move up and down to automatically focus, and the objective lens is adjusted by the laser displacement sensor and its own program. The field of view is automatically and accurately focused again to ensure detection accuracy. During the auto-focusing process, the sample stage does not move, the objective lens moves up and down, and the moving speed is 0-50 mm/s, and the lens has a field of view of 5-100 mm ² for a single acquisition of the silicon carbide wafer. Then the intelligent recognition algorithm program automatically recognizes the inspection pictures, finds various defects and classifies them.

The device can automatically test various defects on the front and back and inside of the silicon carbide wafer through the program setting of the control unit, without the need to manually switch the light source. side.

The front and back defect testing mechanism is to use the first light source and the second light source to jointly test and analyze. If the defect is detected in the first light source and the second light source test results at the same time, the defect is on the silicon surface; if only in the second light source test result If it is detected that the first light source detection result is not detected, the defect is on the carbon surface.

Only the first light source is used for the edge chipping defect, only the third light source is used for the micropipe defect, and only the second light source is used for the miscellaneous crystal and wrapping defects.

First identify the edge of the wafer and then fit an edge, and judge the edge chipping position by whether there is a black concave part at the edge. In the control unit, set a size of edge collapse and depression, and those that exceed our set value are left as collapse edges, and those that do not exceed our set value are filtered out.

The conditions for the intelligent algorithm to identify microtubules are: the similarity with the butterfly shape is greater than 40%, the brightness is greater than 200cd/m2, the light transmittance is greater than 30%, and the area ratio of the brightest area is greater than 25%.

Combined with the inspection data of transmitted light and reflected light, it is possible to identify scratches and pits on the front and back of the wafer. The conditions for the intelligent algorithm to identify pits are: they appear as point-like or block-like defects. The conditions for identifying scratches are: linear defects in reflection and transmission modes.

The condition for the intelligent algorithm to identify edge chipping is: chip edge chip defect.

The condition for the intelligent algorithm to identify miscellaneous crystals is that there are edge defects in the bulk in the transmission mode.

The condition for the intelligent algorithm to identify the package is: the area where point defects gather in transmission mode.

The invention uses the algorithm program of intelligent identification to identify and classify various defects, and at the same time accurately locate and display each defect, which has guiding significance for crystal defects and wafer surface defects generated by the previous process.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (20)

1. An integrated defect inspection apparatus for silicon carbide wafers, comprising: the supporting mechanism, and a sample stage (4), a light generating system and a light collecting system which are arranged on the supporting mechanism;

the sample table (4) is used for placing a wafer;

the light collection system is positioned on one side of the sample stage (4); the light collection system includes: a lens (7) and a light source receiver (8);

the light generating system includes: a plurality of light generating mechanisms positioned on one side or two sides of the sample stage (4); the light source receiver (8) can collect various detection light rays of the light generating mechanism through the lens (7).

2. The integrated defect inspection apparatus for silicon carbide wafers of claim 1 wherein the light generating system comprises: a light reflection mechanism positioned at the first side of the sample stage (4);

the light reflection mechanism includes: a first light source (9) and a first reflector (10); the light of the first light source (9) can be irradiated to the first side of the wafer through the first reflector (10) and reflected;

the light collection system is positioned on the first side of the sample stage (4), and the light source receiver (8) can collect the reflected light of the light reflection mechanism through the lens (7).

3. The integrated defect inspection apparatus for silicon carbide wafers as set forth in claim 1 or 2, wherein the light generating system comprises: a light transmission mechanism located on a second side of the sample stage (4);

the transmitted light mechanism includes: a second light source (11) and a second mirror (12); the light of the second light source (11) can be transmitted from the second side to the first side of the wafer by the second mirror (12);

the light collection system is located on the first side of the sample table (4), and the light source receiver (8) can collect the transmission light of the light transmission mechanism through the lens (7).

4. The integrated defect inspection apparatus for silicon carbide wafers of claim 3 wherein the light generating system further comprises: a light transmission polarization mechanism located at the second side of the sample stage (4); and the light transmission mechanism is positioned between the sample stage (4) and the light transmission polarization mechanism;

the light transmission polarization mechanism includes: a polarizer (3), a third light source (13) and a third reflector (14);

the light collection system further comprises: a deviation testing device (6); the polarization analyzer (6) is positioned between the light reflection mechanism and the lens (7); the light source receiver (8) can collect the transmission polarized light of the light transmission polarization mechanism through the lens (7).

5. The integrated defect inspection apparatus for silicon carbide wafers as set forth in claim 1, wherein said lens (7) is an objective lens of auto-focusing equipped with a ranging laser sensor and a control program with an amplification factor of 1-20 times.

6. The integrated defect inspection apparatus of silicon carbide wafers according to claim 5, wherein the light collection system is located above the sample stage (4);

the lens (7) can move up and down relative to the sample stage (4) at a moving speed of 0-50mm/s, and the single-acquisition visual field of the lens (7) is 5-50mm²。

7. The integrated defect inspection apparatus of silicon carbide wafers according to claim 1, wherein the sample stage (4) comprises: a robotic motion stage (15) capable of moving within the wafer plane.

8. The integrated defect inspection apparatus for silicon carbide wafers as set forth in claim 7 wherein said automated motion stage (15) is a magnetically driven linear motion stage capable of translating said wafers in both the X and Y directions.

9. Integrated defect inspection device of silicon carbide wafers according to claim 7 characterized by the fact that the moving speed of the automatic moving platform (15) is 0-100mm/s, able to move in serpentine shape.

10. Comprehensive defect inspection device of silicon carbide wafers according to claim 1 characterized in that the sample stage (4) is provided with a hollow section (18) for placing a wafer and/or the sample stage (4) has a transparent section for contacting the wafer.

11. Integrated defect inspection device of silicon carbide wafers according to claim 10, characterized in that the edges of the hollow part (18) are notched (16).

12. The integrated defect inspection apparatus for silicon carbide wafers as set forth in claim 10, wherein said transparent portions are glass disks (17) provided at four corners of said hollow portion (18).

13. The integrated defect inspection apparatus for silicon carbide wafers of claim 1 wherein the support mechanism comprises: a base (1) and an equipment housing (2);

the comprehensive defect detection device for the silicon carbide wafer further comprises: a light shield (5) arranged on the equipment shell (2).

14. The integrated defect inspection apparatus for silicon carbide wafers as set forth in claim 1, further comprising: a control unit;

the comprehensive defect detection device for the silicon carbide wafer can automatically test various defects on the front side, the back side and the inside of the wafer through the program setting of the control unit, wherein the defects comprise: front and back scratches, front and back pits, micropipes, mixed crystals and edge breakage.

15. A silicon carbide wafer comprehensive defect inspection method characterized by inspecting the wafer placed on the sample stage (4) by using the silicon carbide wafer comprehensive defect inspection apparatus according to any one of claims 1 to 14, comprising the steps of:

collecting detection light rays of a plurality of light generating mechanisms through the light collecting system;

and analyzing and identifying the defects according to the collected detection light data.

16. The silicon carbide wafer comprehensive defect inspection method of claim 15, wherein said collecting a plurality of inspection lights of said light generating means comprises:

collecting reflected light of the light reflection mechanism, transmitted light of the light transmission mechanism and transmitted polarized light of the light transmission polarization mechanism;

the defect is identified according to the analysis of the collected detection light data, which comprises the following steps:

the defects of the front surface of the substrate including the edge breakage of the wafer are detected by using reflected light, the mixed crystals and the internal defects including the wrapping of the wafer are detected by using transmitted light, and the internal stress defects including the micropipes of the wafer are detected by using transmitted polarized light.

17. The silicon carbide wafer comprehensive defect inspection method according to claim 16, wherein the conditions for identifying edge chipping are: chip edge gap defects;

the conditions for recognizing the mixed crystals are as follows: the block has edge defects in the transmission mode;

the conditions for identifying the package are as follows: a region where point-like defects are gathered in the transmissive mode;

the conditions for identifying the microtubes were: the similarity with butterfly shape is more than 40%, the brightness is more than 200cd/m2, the light transmittance is more than 30%, and the area ratio of the brightest area is more than 25%.

18. The silicon carbide wafer integrated defect inspection method of claim 16, wherein said analyzing and identifying defects based on collected inspection light data further comprises:

if the defect is detected in the detection results of the reflected light and the transmitted light at the same time, the defect is on the silicon surface;

if the defect is detected only in the transmitted light detection result and not in the reflected light detection result, the defect is on the carbon surface.

19. The silicon carbide wafer comprehensive defect inspection method according to claim 15, further comprising, before said collecting, by said light collection system, inspection light rays of said plurality of kinds of light generation mechanisms:

firstly, recognizing the edge of a wafer, then fitting one edge, and judging the edge breakage position according to whether a black recessed part exists at the edge;

the defect is identified according to the analysis of the collected detection light data, which comprises the following steps:

detecting defects on the front surface of the substrate including the edge breakage of the wafer by utilizing reflected light, judging whether the size of the edge breakage recess exceeds a set value, if so, remaining the edge breakage calculation, and if not, filtering.

20. The silicon carbide wafer comprehensive defect inspection method of claim 15, further comprising, after said analyzing and identifying defects based on the collected inspection light data:

the defects are identified and classified, and each defect is located.

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