An efficient detection method and device for the small facet area of an ingot

Abstract

The present invention relates to the field of semiconductor processing technology, and in particular to a method and device for efficiently detecting a small facet area of a crystal ingot. The purpose of the present invention is to provide a method for efficiently detecting a small facet area of a crystal ingot, which shapes a laser beam into a rectangular laser output, replaces point laser scanning with surface laser scanning, expands the single scanning area, thereby improving scanning efficiency, and avoids omission of information on the end face of the crystal ingot, making the efficiency and resolution of the crystal ingot end face detection higher; at the same time, the present invention uses a silver reflector to obtain the light intensity distribution of the rectangular laser, and then corrects the light intensity distribution of the crystal ingot reflected light, thereby avoiding the influence of the uneven intensity of the rectangular laser on the light intensity distribution of the crystal ingot reflected light, and improving the measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor processing technology, and in particular to a high-efficiency detection method and device for a small facet area of a crystal ingot. Background Art

[0002] Semiconductor materials, resistant to high temperatures and radiation, and boasting wide bandgap widths and high breakdown electric fields, are increasingly becoming the primary substrate for electronic devices, holding significant application prospects in fields such as communications and defense. Among the multiple steps involved in converting a crystal ingot into a qualified substrate wafer, ingot cutting is a major source of material loss. Currently, the main ingot cutting technologies include wire sawing and laser lift-off (LAS). Compared to traditional wire sawing, laser lift-off offers significant development potential due to its high production efficiency and minimal material consumption. Laser lift-off (LAS) focuses a laser at a predetermined depth within the semiconductor material, creating a large modified area before wafer separation. However, during the ingot growth process, varying doping concentrations can create faceted and non-faceted regions with varying resistivity and refractive index. When the modified laser passes through these faceted and non-faceted regions, the depth of its focus varies, resulting in poor flatness in the resulting wafer and significant losses during subsequent polishing. Therefore, accurate and efficient detection of facet position is crucial for improving wafer production capacity.

[0003] Existing technologies for detecting facets in ingots primarily include fluorescence detection and transmitted light detection. For example, patent document CN110911268A provides a method for detecting facets using a camera unit. This method uses a camera unit to capture the top surface of the ingot and an image processing unit to perform binarization on the captured image, thereby distinguishing between facet and non-facet areas. However, since the ingot is relatively thick, distinguishing between facet and non-facet areas through direct imaging is not easy, and errors are easily introduced during implementation.

[0004] Patent document CN115472515A, titled "Ingot Processing Method and Processing Device," provides a method for detecting small facets using fluorescence. This method uses a laser of a specific wavelength to illuminate the ingot and detects the intensity of the fluorescence light generated on the upper surface of the ingot to determine the small facet area. However, in the fluorescence detection step, a lens is used to focus the laser onto the sample surface, resulting in insufficient laser point scanning efficiency. Furthermore, the laser power density after focusing is relatively high, which can easily damage the ingot surface.

[0005] In addition, patent document CN117316791A adopts a transmitted light detection method. This method completes the detection of the first peeled wafer by comparing the transmission intensity of the wafer and the output intensity of the light source, and then optimizes the laser processing conditions of the next wafer based on the position information corresponding to the small facet area of the first wafer. However, when using laser to measure the transmittance of the wafer, it is carried out in the form of point scanning, which also has the problems of low efficiency and omission of small facet information.

[0006] In summary, in response to the need to detect small areas of ingots, existing detection methods usually use fluorescence detection and transmitted light detection. The published solutions based on optical non-destructive testing do not discuss the impact of laser energy distribution and laser coverage on scanning efficiency and measurement accuracy. Therefore, further optimization of the solution is needed to achieve efficient and accurate detection. Summary of the Invention

[0007] In order to solve the above-mentioned technical problems, the purpose of the present invention is to provide an efficient detection method for the small face area of a crystal ingot, which shapes the laser beam into a rectangular laser output, replaces point laser scanning with surface laser scanning, expands the single scanning area, thereby improving the scanning efficiency, and avoiding the omission of information on the end face of the crystal ingot, so as to make the efficiency and resolution of the crystal ingot end face detection higher; at the same time, the present invention uses a silver reflector to obtain the light intensity distribution of the rectangular laser, and then corrects the light intensity distribution of the reflected light from the crystal ingot, thereby avoiding the influence of the uneven light intensity of the rectangular laser on the light intensity distribution of the reflected light from the crystal ingot, and improving the measurement accuracy.

[0008] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0009] An efficient detection method for a facet area of an ingot comprises the following steps:

[0010] 1) Optimize the laser of a specific wavelength into a flat-top beam through a homogenization system;

[0011] 2) The laser beam is shaped into a rectangular beam by a beam shaping system;

[0012] 3) The rectangular laser beam is reflected by the beam splitter to the surface of the ingot, where it is reflected;

[0013] 4) The electric translation stage drives the ingot surface to move, causing the laser to scan the ingot surface along a fixed path. At the same time, the CCD detects and records the intensity distribution of the reflected light.

[0014] 5) The reflected light intensity distribution information is transmitted to the control end, and the error caused by uneven laser energy distribution is corrected in combination with a silver reflector to identify the small facet area of the crystal ingot.

[0015] As an advantage, the laser emitted by the laser is a Gaussian beam with a wavelength of 300-1000 nm, an adjustable power of 0-30 W, and a beam quality factor M. 2 <1.3, spot diameter is 1~10 mm.

[0016] Preferably, the light homogenization system includes a spatial light modulator, an aspheric lens group or a micromirror array, which is used to optimize the laser spot into a flat-top beam with uniform energy distribution.

[0017] Preferably, the beam shaping system uses a cylindrical lens group, a special prism or a Fresnel lens to compress the laser beam in one direction and collimate it in another direction, thereby outputting a rectangular spot. The area of the laser spot can be dynamically adjusted according to the size of the ingot.

[0018] Preferably, the sampling frequency of the CCD detection system is synchronized with the movement speed of the electric translation stage to ensure that a high-precision reflected light distribution image is collected at each position on the surface of the ingot to avoid data omission.

[0019] Preferably, the electric translation stage has an XYZ three-dimensional motion function, and adjusts the distance between the ingot surface and the CCD by controlling the displacement in the Z-axis direction to optimize the reflected light imaging quality.

[0020] Preferably, the detection of the reflected light uses a bandpass filter to filter stray light to improve the accuracy of the CCD detection signal, and the filter has high transmittance in the laser band.

[0021] Preferably, the reflected light image information collected by the CCD is corrected by the control end, and the corrected image is spliced to identify the small face area of the ingot; further, the control end performs Z-Score normalization processing based on the reflected light intensity distribution image collected by the CCD to eliminate the influence of uneven ambient light and laser light intensity, thereby obtaining high-precision small face area information of the ingot.

[0022] Preferably, the silver reflector is used to correct the laser energy distribution, and the collected light intensity distribution reflected by the silver reflector is used as a reference background image to correct the uneven reflected light distribution on the surface of the ingot.

[0023] Furthermore, the present invention also discloses a device for implementing the method, the device comprising:

[0024] Laser, used to emit laser light of a specific wavelength;

[0025] Light homogenization system, used to optimize the energy distribution of the laser spot;

[0026] A beam shaping system for shaping the laser beam into a rectangular beam;

[0027] The beam splitter is used to reflect part of the laser light to the surface of the ingot, and the other part is used to transmit the reflected light signal;

[0028] Electric translation stage, used to carry the ingot and move it in XY direction;

[0029] CCD, used to detect and record the reflected light intensity distribution image;

[0030] The control end is used to control system parameters and process reflected light data.

[0031] The present invention adopts the above-mentioned technical solution. The method uses beam shaping technology to shape the laser beam into a rectangular beam, and expands the single scanning area through surface laser scanning, avoiding the low efficiency problem caused by point scanning. At the same time, a silver reflector is used to correct the unevenness of the laser energy distribution to ensure the detection accuracy and the uniformity of the reflected light intensity distribution. Through this innovative laser scanning and correction method, the present invention effectively solves the problems of low efficiency, laser damage to the ingot surface, and insufficient measurement accuracy in existing detection technologies, greatly improving the detection speed and accuracy of small areas of the ingot, and is suitable for the production and detection needs of large-scale ingots.

[0032] The technical solution of the present invention not only significantly improves the detection efficiency of the small facet area of the ingot, but also ensures the accuracy of the detection results by optimizing the laser scanning mode and reflected light correction processing, providing reliable technical support for the production of high-quality wafers. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Flowchart for detecting small faces with reflected light.

[0034] Figure 2 Schematic diagram of the device structure of the present invention; wherein: 1 laser; 2 light homogenization system; 3 beam shaping system; 4 beam splitter; 5 crystal ingot or silver reflector; 6 electric translation stage; 7 convex lens; 8 bandpass filter; 9 CCD; 10 control terminal.

[0035] Figure 3 This is a process diagram of laser scanning of the present invention, wherein Figure 3 (a) is a schematic diagram of the end face of the ingot 501; Figure 3 Middle (b) is a schematic diagram of a rectangular spot scanning the end face of the ingot; Figure 3 (c) Schematic diagram of stitching N rectified images together. DETAILED DESCRIPTION

[0036] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0037] like Figure 2 As shown, the ingot facet detection device of the present invention includes 1 a laser; 2 a light homogenization system; 3 a beam shaping system; 4 a beam splitter; 5 a crystal ingot or silver reflector; 6 an electric translation stage; 7 a convex lens; 8 a bandpass filter; 9 a CCD; and 10 a control terminal.

[0038] Laser 1, emitting laser light of a specific wavelength for ingot surface detection; homogenization system 2, optimizing the energy distribution of the laser spot; beam shaping system 3, shaping the laser spot to produce a rectangular output spot; beam splitter 4, reflecting the laser light and reflecting light from the upper surface containing target information; motorized translation stage 6, loading the ingot; convex lens 7, focusing the reflected light; bandpass filter 8, transmitting the reflected light and cutting off stray light; CCD 9, detecting the reflected light passing through the bandpass filter; control terminal 10, controlling the laser timing, the motorized translation stage movement, and processing the reflected light intensity distribution image measured by CCD 9.

[0039] like Figure 1 As shown, the method for detecting the small facet area of the ingot, the ingot detection stage includes the following steps:

[0040] (1) Place the crystal ingot 501 on the electric translation stage 6;

[0041] (2) The laser beam of a specific wavelength is transmitted to the beam shaping system 3 after the energy distribution of the light spot is optimized by the homogenization system 2;

[0042] (3) The beam shaping system 3 shapes the laser beam into a rectangular laser beam, and transmits part of the laser beam reflected by the beam splitter 4 to the upper surface of the crystal ingot 501, where it is reflected;

[0043] (4) The electric translation stage 6 drives the crystal ingot 501 to move, so that the laser scans the surface of the crystal ingot 501 along a fixed path. At the same time, the CCD 9 detects the intensity of the reflected light on the upper surface of the crystal ingot 501 at a determined sampling frequency and transmits the image of the reflected light intensity distribution to the control terminal;

[0044] (5) The control terminal 10 stores the intensity distribution of the reflected light of the crystal ingot before correction collected by the CCD 9.

[0045] The light homogenization system 2 can optimize the laser beam into a flat-top beam with relatively uniform energy distribution.

[0046] The beam shaping system 3 can compress the laser beam along a certain direction to generate a rectangular laser spot of a certain area required for detection.

[0047] The laser 1 emits a Gaussian beam with a wavelength of 300-1000 nm, an adjustable power of 0-30 W, and a beam quality factor M. 2 <1.3, spot diameter 1~10 mm.

[0048] The beam splitter 4 reflects and transmits light in a ratio of 1:1. The reflected laser light is used for detecting the upper surface of the crystal ingot, and the light reflected from the upper surface of the crystal ingot 501 is used to characterize the facet information.

[0049] When the electric translation stage 6 carries the crystal ingot, its movement is controlled by the control end 10 so that the laser beam scans along a fixed path on the surface of the crystal ingot 501 .

[0050] The moving speed of the electric translation stage 6 is 50-500 mm / s.

[0051] The electric translation stage 6 includes XYZ three-axis movement. When detecting crystal ingots of different thicknesses, the distance between the upper surface of the crystal ingot 501 and the CCD 9 is optimized by controlling the displacement in the Z-axis direction to achieve high-quality imaging.

[0052] The control terminal 10 stores each rectangular sampling area containing the intensity distribution information of the reflected light from the crystal ingot 501 collected by the CCD 9 for subsequent correction.

[0053] The bandpass filter 8 has high transmittance in the laser wavelength band.

[0054] The detection method of the ingot facet area is characterized by the fact that the actual rectangular laser after shaping still has uneven distribution, which will affect the intensity distribution of the reflected light from the ingot, so correction is required. The correction stage includes the following steps:

[0055] (1) Place a silver reflector 502 at position 6 of the electric translation stage;

[0056] (2) Without changing the parameters of the laser, the light homogenization system, and the beam shaping system, the laser beam is transmitted to the beam shaping system after passing through the light homogenization system;

[0057] (3) The beam shaping system outputs a rectangular laser beam, which is reflected by the beam splitter and transmitted to the upper surface of the silver reflector 502, where it is reflected;

[0058] (4) CCD9 transmits the intensity distribution image of the light reflected by the silver reflector to the control terminal 10;

[0059] (5) The control terminal 10 uses the intensity distribution of the reflected light from the silver reflector as a background to correct the intensity distribution of the reflected light from the ingot before correction, thereby obtaining the corrected intensity distribution of the reflected light from the ingot. The control terminal 10 stitches together all the corrected intensity distribution images of the reflected light from the ingot and identifies the facet area on the surface of the ingot based on the intensity of the reflected light from the images.

[0060] The electric translation stage 6 optimizes the distance between the upper surface of the silver reflective mirror 502 and the CCD 9 by controlling the displacement in the Z-axis direction, thereby achieving high-quality imaging.

[0061] The control terminal 10 calibrates the pre-calibration intensity distribution of the ingot reflected light with the intensity distribution of the silver reflector. The rectangular area of the intensity distribution of the ingot reflected light obtained by the above method is consistent in size and direction with the rectangular area of the intensity distribution of the silver reflector. Therefore, it is only necessary to divide all the pre-calibration intensity distributions of the ingot reflected light by the intensity distribution of the silver reflector and normalize the result using the Z-Score to obtain the calibrated intensity distribution of the ingot reflected light.

[0062] The control end 10 stitches together the corrected intensity distribution images of the reflected light from the ingot, and identifies the facet area on the surface of the ingot according to the intensity of the reflected light.

[0063] When a laser with the same parameters is reflected on the upper surface of the ingot, due to the different reflectivities of the laser to the small facet area and the non-small facet area, reflected light with different intensities will be obtained. The intensity distribution of the reflected light corresponds to the distribution of the small facet area, so the small facet area and the non-small facet area of the ingot can be judged by the intensity of the reflected light. In addition, due to the errors of the laser, the light homogenization system and the beam shaping system, the rectangular laser beam after shaping is not uniform, which will cause the detection results to be affected by the actual rectangular laser beam distribution. The present invention adopts a light homogenization system and a beam shaping system to optimize the laser beam and output a rectangular light spot with a more uniform energy distribution. The rectangular surface laser scans the upper surface of the ingot, covering a wider range, improving the scanning efficiency and avoiding the omission of upper surface information. At the same time, the actual distribution of the rectangular laser beam is obtained by a silver reflector, and the scanning results are corrected, thereby improving the accuracy of small facet area recognition.

[0064] Inspection equipment for the small facet area of the ingot, such as Figure 2As shown, the crystal ingot 501 is fixed on the electric translation stage 6, and its movement path is controlled by the control terminal 10. The laser 1 emits a Gaussian beam, which is passed through the light homogenization system 2 and the beam shaping system 3 to obtain a rectangular laser. The rectangular laser is reflected by the beam splitter 4 to the upper surface of the crystal ingot to be measured. The laser is emitted and refracted on the upper surface, and the reflected light signal is half transmitted and half reflected by the beam splitter 4. The transmitted reflected light is converged by the convex lens 7, filtered by the bandpass filter 8, and then transmitted to the CCD 9. The CCD 9 detects and records the reflected light image and transmits it to the control terminal 10. By moving the electric translation stage 6 in the XY direction, the laser scans the entire upper surface of the crystal ingot, and measures the intensity distribution images of the reflected light of N crystal ingots to be corrected. The crystal ingot 501 is replaced with the silver reflector 502. According to the same parameters of the laser 1, the light homogenization system 2, and the beam shaping system 3, the rectangular laser is reflected by the beam splitter 4 to the upper surface of the silver reflector 502. The laser on the upper surface is emitted and refracted, and the reflected light signal is half transmitted and half reflected by the beam splitter 4. The transmitted reflected light is converged by the convex lens 7, filtered by the bandpass filter 8 for stray light, and then transmitted to the CCD9. The CCD9 detects and records the intensity image of the light reflected by the silver reflector 502 and transmits it to the control terminal 10. The intensity of the reflected light of the N crystal ingots 501 to be corrected is divided by the intensity of the reflected light of the silver reflector 502 and Z-Score normalization is performed to obtain the intensity images of the reflected light of the N corrected crystal ingots 501. The control terminal 10 splices the N corrected images of the reflected light of the crystal ingot 501 together and identifies the small facet area of the end face of the crystal ingot 501 according to the distribution of the intensity of the reflected light.

[0065] Preferably, the power density of the rectangular laser transmitted to the upper surface of the ingot 501 is not less than 0.1 W / cm 2 .

[0066] Among them, the present invention adopts a uniform light system to optimize the energy distribution of the light spot, which can be achieved through optical elements such as a spatial light modulator, an aspheric lens group, and a micromirror array.

[0067] The beam shaping system can utilize cylindrical lens systems and special prisms to compress the laser beam in one direction and collimate it in another, achieving a rectangular spot output. Furthermore, using optical components with different parameters can achieve laser output with varying spot sizes, adapting to the inspection of ingot facets of varying sizes.

[0068] Figure 3 (a) is a schematic diagram of the end face of the crystal ingot 501. Figure 3 (b) is a schematic diagram of a rectangular light spot scanning the end face of the ingot. Figure 3 As shown in (b), a laser of a specific wavelength forms a rectangular spot after passing through the homogenization system and the beam shaping system, which is then irradiated onto the end face of the ingot. The CCD records the image of the reflected light in the rectangular area. The electric translation stage 6 drives the ingot 5 to move in the XY direction at a certain speed, forming a scanning path ( Figure 3 The corresponding rectangular laser scanning path in (b) is Ⅰ→Ⅱ→Ⅲ→Ⅳ→Ⅴ→VI→VII→VIII→IX). After the laser completes the scanning of the ingot end face, the CCD records N images of the reflected light intensity distribution. The control end stitches the N corrected images together, as shown in Figure 1. Figure 3 As shown in (c), the non-facet region 5a and the facet region 5b of the ingot end face are identified based on the reflected light intensity distribution.

[0069] The above is a description of the embodiments of the present invention. The above description of the disclosed embodiments will enable professionals in the field to implement or use the present invention. Various modifications to these embodiments will be apparent to professionals in the field. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but should conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An efficient detection method for the small facet area of an ingot, characterized in that: The following steps are involved: 1) Laser, used to emit laser light of a specific wavelength, which is optimized into a flat-top beam through a homogenization system; 2) The laser beam is shaped into a rectangular beam by a beam shaping system; 3) The rectangular laser beam is reflected by the beam splitter to the surface of the ingot, where it is reflected; 4) The electric translation stage drives the ingot surface to move, causing the laser to scan the ingot surface along a fixed path. At the same time, the CCD detects and records the intensity distribution of the reflected light. 5) Transmitting the reflected light intensity distribution information to the control end, and using a silver reflector to correct errors caused by uneven laser energy distribution, thereby identifying the small facet area of the ingot; the silver reflector correction stage includes the following steps: a) Place a silver mirror on the motorized translation stage; b) Without changing the parameters of the laser, light homogenization system and beam shaping system, the laser beam is transmitted to the beam shaping system after passing through the light homogenization system; c) The beam shaping system outputs a rectangular laser beam, which is reflected by the beam splitter and transmitted to the upper surface of the silver reflector, where it is reflected. d) CCD transmits the intensity distribution image of the light reflected by the silver mirror to the control end; e) The control end uses the intensity distribution of light reflected from the silver reflector as a background, and corrects the intensity distribution of light reflected from the ingot before correction to obtain the corrected intensity distribution of light reflected from the ingot. The control end stitches all corrected intensity distribution images of light reflected from the ingot together, and identifies the facet area on the surface of the ingot based on the intensity of the reflected light from the images.

2. The method according to claim 1, characterized in that The laser emitted by the laser is a Gaussian beam with a wavelength of 300~1000 nm, an adjustable power of 0~30 W, and a beam quality factor M 2 <1.3, spot diameter is 1~10 mm.

3. The method according to claim 1, characterized in that The light homogenization system includes a spatial light modulator, an aspheric lens group or a micromirror array, and is used to optimize the laser spot into a flat-top beam with uniform energy distribution.

4. The method according to claim 1, wherein The beam shaping system uses a cylindrical lens group, a special prism or a Fresnel lens to compress the laser beam in one direction and collimate it in another direction, thereby outputting a rectangular spot. The area of the laser spot can be dynamically adjusted according to the size of the ingot.

5. The method according to claim 1, wherein The sampling frequency of the CCD is synchronized with the movement speed of the electric translation stage, ensuring that high-precision reflected light distribution images are collected at every position on the ingot surface to avoid data omission.

6. The method according to claim 1, characterized in that The electric translation stage has XYZ three-dimensional motion function, and adjusts the distance between the crystal ingot surface and the CCD by controlling the displacement in the Z-axis direction to optimize the reflected light imaging quality.

7. The method according to claim 1, characterized in that The detection of the reflected light adopts a bandpass filter to filter stray light to improve the accuracy of the CCD detection signal. The filter has high transmittance in the laser band.

8. The method according to claim 1, characterized in that The reflected light image information collected by the CCD is corrected by the control end, and the corrected images are spliced to identify the small face area of the ingot; further, the control end performs Z-Score normalization processing based on the reflected light intensity distribution image collected by the CCD to eliminate the influence of uneven ambient light and laser light intensity, thereby obtaining high-precision small face area information of the ingot.

9. The method according to claim 1, characterized in that The silver reflector is used to correct the laser energy distribution, and the collected silver reflector reflected light intensity distribution is used as a reference background image to correct the uneven reflected light distribution on the surface of the ingot.

10. A device for implementing the method according to any one of claims 1 to 9, characterized in that: The device includes: Laser, used to emit laser light of a specific wavelength; Light homogenization system, used to optimize the energy distribution of the laser spot; A beam shaping system for shaping the laser beam into a rectangular beam; The beam splitter is used to reflect part of the laser light to the surface of the ingot, and the other part is used to transmit the reflected light signal; Electric translation stage, used to carry the ingot and move it in XY direction; CCD, used to detect and record the reflected light intensity distribution image; The control end is used to control system parameters and process reflected light data.

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