Ultra-precision grinding and photochemical mechanical polishing combined process for laser crystal slice

Abstract

The invention relates to an ultra-precision grinding and photochemical mechanical polishing combined process for a laser crystal sheet. Comprising the following steps that coarse grinding is conducted through a coarse-grained grinding wheel, rapid thinning is achieved, the depth of a subsurface damaged layer is determined, and reference is provided for the grinding wheel feeding amount in the accurate grinding stage; a fine-grained grinding wheel is adopted for accurate grinding, a damaged layer introduced in the coarse grinding stage is removed, and high surface / subsurface quality and surface precision are obtained by optimizing technological parameters; a special polishing solution for photochemical mechanical polishing is prepared from an aluminum oxide (Al2O3) grinding material, semi-fine polishing is carried out on a laser crystal sheet, and surface damage caused in the grinding stage is rapidly removed; a special polishing solution for photochemical mechanical polishing is prepared from a zirconium oxide (ZrO2) grinding material, and the laser crystal sheet is finely polished, so that the surface quality and the surface precision are further optimized; an ultrasonic cleaning instrument is adopted to clean the laser crystal slice, and a cleaning agent is absolute ethyl alcohol. According to the invention, high-surface integrity and high-efficiency processing of the laser crystal slice can be synchronously realized.

Description

Technical Field

[0001] The invention relates to the technical field of ultra-precision processing of laser crystal slices in thin-slice lasers, and in particular to a combined process of ultra-precision grinding and photochemical mechanical polishing of laser crystal slices. Background Art

[0002] Thin-disk lasers have the advantages of extremely thin gain medium, high pumping efficiency, small wavefront distortion, and compact structure of solid-state lasers, and have become the development direction of high-power lasers in the future. Among them, the gain medium is the core component of thin-disk lasers, and the preparation quality directly affects the performance and service life of the laser. Common gain media (such as YAG, Lu 2 O 3 Laser crystal sheets such as AG and GGG have the characteristics of high hardness, high brittleness and strong chemical inertness. At the same time, due to the thin thickness and large diameter-to-thickness ratio of laser crystal sheets, the warping deformation caused by processing and holding makes it difficult to ensure the surface accuracy requirements.

[0003] For the processing of laser crystal slices, the main processing technology used is a combination of grinding and polishing. However, there are two problems in the combined processing of laser crystal slices using traditional grinding and chemical mechanical polishing: on the one hand, the material removal rate is low when grinding laser crystal slices with free abrasives, and the large abrasive particles in the grinding fluid easily cause deep scratches and sub-surface damage on the processed surface of the laser crystal slice, thereby increasing the processing time of the subsequent polishing process stage; on the other hand, due to the stable chemical properties of the material of the laser crystal slice, the chemical reaction rate is low when using traditional mechanical polishing, and the mismatch of chemical-mechanical action leads to low material removal rate and long processing time, and excessive polishing time will lead to poor surface accuracy of the laser crystal slice. Summary of the invention

[0004] According to the technical problems raised above, a combined process of ultra-precision grinding and photochemical mechanical polishing of laser crystal slices is provided, which includes an ultra-precision grinding stage and a photochemical mechanical polishing stage.

[0005] The ultra-precision grinding stage includes the rough grinding stage and the fine grinding stage. The purpose of the rough grinding stage is to quickly realize the thinning operation of the laser crystal slice and to improve the grinding allowance reference for the fine grinding stage; the purpose of the fine grinding stage is to remove the crystal subsurface damage caused by the rough grinding and to improve the surface accuracy PV and surface roughness RMS of the laser crystal slice by optimizing the grinding parameters.

[0006] The photochemical mechanical polishing stage includes a semi-fine polishing stage and a fine polishing stage. In the semi-fine polishing stage, without deteriorating the surface accuracy of the laser crystal slice, the surface damage of the laser crystal slice caused by the grinding stage is removed with the material removal rate as the main factor and the surface quality as the auxiliary factor. In the fine polishing stage, with the surface quality as the main factor and the material removal rate as the auxiliary factor, the surface quality of the laser crystal slice is optimized and the surface accuracy of the laser crystal slice is trimmed, thereby obtaining a laser crystal slice with high precision and high surface integrity.

[0007] The technical means adopted by the present invention are as follows:

[0008] A laser crystal slice ultra-precision grinding and photochemical mechanical polishing combined process, comprising the following steps:

[0009] Step 1, rough grinding stage: paraffin is used to fix the laser crystal slice on the silicon wafer, and the silicon wafer is adsorbed on the vacuum suction cup worktable of the self-rotating ultra-precision grinding machine. During grinding, the grinding wheel and the laser crystal slice rotate around their respective axes respectively, and the grinding wheel is fed along the axial direction of the machine tool spindle, and deionized water is used as a coolant; a cup-type grinding wheel with a preset coarse fixed abrasive particle size is used to rough grind the laser crystal slice based on preset grinding parameters;

[0010] Among them, the raw materials are laser crystal slices such as yttrium aluminum garnet and lutetium oxide with a diameter ≥Φ12mm.

[0011] The self-rotating ultra-precision grinding machine tool includes a vacuum chuck worktable and a grinding wheel. Paraffin wax is used to fix the laser crystal slice at a certain position away from the center of the silicon wafer, and the silicon wafer is adsorbed on the vacuum chuck worktable to ensure that the center of the silicon wafer coincides with the center of the worktable.

[0012] A cup-type grinding wheel with coarser bonded abrasive grains was used to roughly grind the laser crystal slices, determine the reasonable grinding parameters, coordinately control the thinning efficiency and surface integrity of the laser crystal slices, determine the depth of the subsurface damage layer, and provide a reference for the material removal allowance in the next process stage.

[0013] Step 2, fine grinding stage: use a cup grinding wheel with a preset finer fixed abrasive grain size to fine grind the laser crystal slice; according to the depth value of the sub-surface processing damage layer obtained in the rough grinding stage, set the total amount of grinding wheel feed in the fine grinding stage to grind away the damage layer, and obtain good grinding surface / sub-surface quality and surface accuracy of the laser crystal slice by optimizing the grinding process parameters;

[0014] Step 3, semi-finishing polishing stage: paraffin wax is used to stick the ground laser crystal slice on the carrier plate, and a counterweight block is added to the carrier plate to make the workpiece in close contact with the polishing pad on the polishing disk of the chemical mechanical polishing device; alumina abrasive is used to prepare a special polishing liquid for the semi-finishing polishing stage of photochemical mechanical polishing, and the laser crystal slice is semi-finishing polished to quickly remove surface damage such as scratches and pits caused by the grinding stage, and obtain a laser crystal slice with a better surface morphology; the chemical mechanical polishing device is an automatic polishing machine; the ultraviolet light source is set at a certain position just above the polishing pad;

[0015] Step 4, fine polishing stage: using zirconium oxide abrasive with lower hardness to prepare a special polishing liquid for the fine polishing stage of photochemical mechanical polishing, and fine polishing the laser crystal slice after semi-fine polishing;

[0016] In step 3 and step 4, ultraviolet light irradiation is performed by an ultraviolet light emitting device.

[0017] Furthermore, after step 4, step 5 is further provided, using anhydrous ethanol as a cleaning agent, and placing the finely polished laser crystal slice in an ultrasonic cleaning apparatus for cleaning.

[0018] Further, in step 1, the abrasive grain size of the cup grinding wheel is #325 or #600.

[0019] Further, in step 2, the abrasive grain size of the cup grinding wheel is #1500 or #3000.

[0020] Furthermore, in step 1 and step 2, the grinding wheel speed range is 1000-3000 rpm, the laser crystal slice self-rotation speed range is 60-240 rpm, and the grinding wheel axial feed speed range is 5-20 um / min.

[0021] Furthermore, the ultraviolet light emitting device is any one of a mercury lamp, a xenon lamp, a deuterium lamp and a bromine tungsten lamp, with a wavelength range of 180 to 1800 nm and an ultraviolet light intensity of 50 to 150 mw / cm 2 .

[0022] Furthermore, in step 3 and step 4, the polishing load is 10-40 kPa, the polishing disc rotation speed is 50-90 rpm, the polishing liquid flow rate is 2-14 ml / min, and the polishing pad is a polyurethane polishing pad IC1000.

[0023] Furthermore, in step 3 and step 4, the abrasive particle size in the special polishing liquid is 20 to 500 nm, and the abrasive concentration is 20 to 110 g / L.

[0024] Furthermore, in step 3 and step 4, in addition to aluminum oxide abrasive and zirconium oxide abrasive, the remaining additive components include 0.05-0.20 g / L semiconductor photocatalyst, 5-20 g / L electron capture agent, pH adjuster, 1-5 g / L abrasive dispersant, and the pH adjuster adjusts the pH value of the solution to 2-5.

[0025] Furthermore, the semiconductor photocatalyst is MnFe 2 O 4 ,CuFe 2 O 4 and CoFe 2 O 4 At least one of spinel ferrites; the electron capture agent is hydrogen peroxide H 2 O 2 , peracetic acid CH3COOOH, sodium dichromate Na 2 Cr 2 O 7 and potassium permanganate KMnO 4 At least one of; the regulator is HNO 3 , H 2 SO 4 , H 2 CO 3 and one of phosphoric acid; the abrasive dispersant is at least one of sodium dodecylbenzene sulfonate SDBS, sodium hexametaphosphate SH, polyvinyl pyrrolidone PVP, sodium polyacrylate SP, polyethylene glycol PEG2000 and sodium tripolyphosphate STPP.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. High processing efficiency: Under the premise of given surface quality and surface accuracy, the total processing time used by the traditional process route (grinding + traditional chemical mechanical polishing) is about 14.5 hours, while the total processing time used by the new combined processing method of the present invention (ultra-precision grinding + photochemical mechanical polishing) is up to about 5 hours, and the processing efficiency is improved by nearly 3 times.

[0028] 2. Good surface / subsurface quality: By using the new combined process method of the present invention to process laser crystal slices, a surface roughness RMS < 0.30 nm and a surface quality without surface / subsurface damage can be obtained.

[0029] 3. High surface accuracy: The combined process method of the present invention has an average surface accuracy PV of 60nm<1 / 10λ@632.8nm for the obtained laser crystal slice, which is much higher than the processing quality of traditional processing technology.

[0030] The invention has reasonable design, low processing cost, strong universality and is suitable for batch processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 This is a schematic diagram of the processing principle of ultra-precision grinding and photochemical mechanical polishing of laser crystal slices according to the present invention.

[0033] Figure 2 This is a process roadmap for the combined processing of laser crystal slices according to the present invention, wherein (a) is self-rotating ultra-precision grinding; and (b) is photochemical mechanical polishing.

[0034] Figure 3 Optical surface diagram of the surface quality and surface accuracy of laser crystal thin slice processing, where (a) is the 3D surface morphology; (b) is the sub-surface morphology; and (c) is the surface accuracy PV.

[0035] Figure 4 These are samples of laser crystal slices processed in batches, where (a) is a YAG laser crystal slice; (b) is a Lu 2 O 3 Laser crystal slices.

[0036] Figure 5 The figure compares the processing efficiency between the new combined process method of the present invention and the traditional process.

[0037] In the figure: 1. Laser crystal slice; 2. Silicon wafer; 3. Vacuum suction cup workbench; 4. Spindle axial direction; 5. Cup grinding wheel; 6. Counterweight; 7. Laser crystal slice; 8. Polishing disk; 9. Ultraviolet light emitting device; 10. Polishing liquid; 11. Loading tray; 12. Polishing pad. DETAILED DESCRIPTION

[0038] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0041] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0042] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0043] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0044] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0045] like Figures 1 to 5 As shown, the embodiment of the present invention discloses a laser crystal slice ultra-precision grinding and photochemical mechanical polishing combined process,

[0046] The self-rotating ultra-precision grinding device includes a vacuum chuck worktable 3 and a cup grinding wheel 5. In this embodiment, the laser crystal slice 1 is fixed at a distance of 35 mm from the center of the silicon wafer 2 by paraffin wax, and the silicon wafer 2 is adsorbed on the vacuum chuck worktable 3, and it is ensured that the center of the silicon wafer 2 coincides with the center of the worktable 3. During the grinding process, the cup grinding wheel 5 and the laser crystal slice 1 rotate around their respective axes, and the cup grinding wheel 5 feeds along the axial direction 4 of the machine tool spindle, and deionized water is used to remove the heat and chips generated during the grinding process of the workpiece.

[0047] Rough grinding process stage: Use a cup-shaped grinding wheel 5 with a coarse fixed abrasive grain size to rough grind the laser crystal slice 1, determine reasonable grinding parameters, coordinately control the thinning efficiency and surface integrity of the laser crystal slice 1, determine the depth of the subsurface damage layer, and provide a reference for the total amount of grinding in the next process stage, so as to remove the subsurface damage layer caused by rough grinding. The processing time of this stage is 38min to 2.5h.

[0048] Fine grinding process stage: Use a cup grinding wheel 5 with a finer fixed abrasive grain size, and refer to the depth value of the subsurface damage layer of the laser crystal slice 1 in the rough grinding stage to set the total feed amount of the cup grinding wheel 5 in the fine grinding stage to grind away the damage layer. Then, by optimizing the grinding process parameters, a laser crystal slice 1 with good grinding surface / subsurface quality and high surface accuracy is obtained. The processing time of this stage is 1min to 10min.

[0049] Semi-finishing polishing process stage: The polishing stage uses a special device for photochemical mechanical polishing, including an ultraviolet light emitting device 9 and an automatic polishing machine; the ultraviolet light source 9 is set 15 cm above the polishing pad; paraffin wax is used to evenly stick the ground laser crystal slice 7 on the carrier plate, and a counterweight block 6 is added to the carrier plate 11 to make the laser crystal slice 7 and the polishing pad 12 on the polishing plate 8 in close contact; alumina abrasive is used to prepare a special polishing liquid 10 for the semi-finishing polishing stage of photochemical mechanical polishing, and the laser crystal slice 7 is semi-finished to quickly remove surface defects such as scratches and pits caused by the grinding stage, and obtain a laser crystal slice 7 with a better surface morphology. The processing time of this stage is 40min to 60min.

[0050] Fine polishing process stage: In the fine polishing stage of the laser crystal slice 7, a special polishing liquid 10 for photochemical mechanical polishing is prepared using zirconium oxide abrasive with lower hardness to polish the laser crystal slice 7 after semi-fine polishing, so as to further optimize the surface quality and surface accuracy of the workpiece. The processing time of this stage is 60min to 90min.

[0051] Workpiece cleaning process: Place the finely polished laser crystal slice 7 in an ultrasonic cleaning apparatus for cleaning, and use anhydrous ethanol as a cleaning agent to remove residual abrasives, chemicals and other contaminants on the surface to obtain a clean surface of the laser crystal slice 7. The processing time of this stage is 10 minutes to 30 minutes.

[0052] Example 1

[0053] In this embodiment, the raw material processed is yttrium aluminum garnet with a diameter of Φ15 mm.

[0054] The laser crystal slice was coarsely ground using a #325 cup grinding wheel, with a grinding wheel speed of 2800 rpm, a laser crystal slice self-rotation speed of 150 rpm, a grinding wheel axial feed speed of 15 um / min, and a processing time of 2 h.

[0055] A #1500 cup grinding wheel was used. The total feed amount of the cup grinding wheel was set in the fine grinding stage to remove the damaged layer, referring to the depth of the subsurface processing damage layer of the laser crystal slice in the rough grinding stage. The grinding wheel speed was 1200rpm, the rotation speed of the laser crystal slice was 150rpm, the axial feed speed of the grinding wheel was 15um / min, and the processing time of this stage was 5min.

[0056] Of course, in the actual processing process, since it is not easy to determine the actual processing allowance, after setting the grinding parameters, adjustments can be made within the set range during the specific processing time period, and the same applies to the following embodiments.

[0057] Semi-finishing polishing process stage: set a mercury lamp light source with a wavelength of 254nm and an ultraviolet light intensity of 50-150mw / cm 2 Alumina abrasive was used to prepare a special polishing liquid for the semi-finishing stage of photochemical mechanical polishing. The laser crystal slice was semi-finished. The abrasive particle size was 20-500nm, the abrasive concentration was 80g / L, and it also included 0.05g / L MnFe 2 O 4 , 15g / L potassium permanganate KMnO 4 , pH value regulator, 5g / L sodium dodecylbenzene sulfonate SDBS, sodium hexametaphosphate SH, H 2 SO 4 The pH value of the solution was adjusted to 3 to quickly remove surface defects such as scratches and pits caused by the grinding stage, and obtain a laser crystal slice with good surface morphology. The polishing load was 40 kPa, the polishing disc speed was 90 rpm, and the polishing liquid flow rate was 10 ml / min. The processing time of this stage was 40 min.

[0058] Fine polishing process stage: Use zirconium oxide abrasive with lower hardness to prepare photochemical mechanical polishing fine polishing special polishing liquid, polish the laser crystal slice after semi-fine polishing, the abrasive particle size is 20-500nm, the abrasive concentration is 80g / L, and also includes 0.05g / L MnFe 2 O 4 , 15g / L potassium permanganate KMnO 4 , pH value regulator, 5g / L sodium dodecylbenzene sulfonate SDBS, sodium hexametaphosphate SH, H 2 SO 4 The pH value of the solution was adjusted to 3 to further optimize the surface quality and surface accuracy of the workpiece. The polishing load was 40 kPa, the polishing disc speed was 90 rpm, the polishing liquid flow rate was 14 ml / min, and the processing time in this stage was 90 min.

[0059] The laser crystal slice after fine polishing is placed in an ultrasonic cleaner for cleaning, and anhydrous ethanol is used as a cleaning agent to remove residual abrasives, chemicals and other contaminants on the surface to obtain a clean laser crystal slice surface. The processing time of this stage is 20 minutes.

[0060] The total time was 4h35min.

[0061] Example 2

[0062] In this embodiment, the raw material processed is Φ12mm yttrium aluminum garnet, and the laser crystal slice is coarsely ground using a #600 cup grinding wheel. The grinding wheel speed is 1800rpm, the laser crystal slice self-rotation speed is 240rpm, the grinding wheel axial feed speed is 10um / min, and the processing time is 1h20min.

[0063] A #3000 cup-shaped grinding wheel was used. The total feed amount of the cup-shaped grinding wheel in the fine grinding stage was set to remove the damaged layer, referring to the depth value of the sub-surface processing of the laser crystal slice in the rough grinding stage. The grinding wheel speed was 1500rpm, the rotation speed of the laser crystal slice was 240rpm, the axial feed speed of the grinding wheel was 10um / min, and the processing time in this stage was 2min.

[0064] Semi-finishing polishing process stage: set bromine tungsten lamp, wavelength of 254nm, ultraviolet light intensity of 50 ~ 150mw / cm 2 Alumina abrasive was used to prepare a special polishing liquid for the semi-finishing stage of photochemical mechanical polishing. The laser crystal slice was semi-finished. The abrasive particle size was 20-500nm, the abrasive concentration was 100g / L, and the total concentration of MnFe was 0.15g / L. 2 O 4 ,CuFe 2 O 4 and CoFe 2 O 4 mixture, 5g / L hydrogen peroxide H 2 O 2 , pH value regulator, 5g / L sodium tripolyphosphate STPP, H 2 SO 4 The pH value of the solution was adjusted to 2 to quickly remove surface defects such as scratches and pits caused by the grinding stage, and obtain a laser crystal slice with good surface morphology. The polishing load was 30 kPa, the polishing disc speed was 65 rpm, the polishing liquid flow rate was 14 ml / min, and the processing time of this stage was 60 min.

[0065] Fine polishing process stage: Use zirconium oxide abrasive with lower hardness to prepare photochemical mechanical polishing fine polishing special polishing liquid, polish the laser crystal slice after semi-fine polishing, the abrasive particle size is 20-500nm, the abrasive concentration is 100g / L, and also includes 0.15g / L CoFe 2 O 4 , 5g / L hydrogen peroxide H 2 O 2 , pH value regulator, 5g / L sodium tripolyphosphate STPP, H 2 SO 4The pH value of the solution was adjusted to 2 to further optimize the surface quality and surface accuracy of the workpiece. The polishing load was 30 kPa, the polishing disc speed was 90 rpm, the polishing liquid flow rate was 14 ml / min, and the processing time in this stage was 60 min.

[0066] The laser crystal slice after fine polishing is placed in an ultrasonic cleaner for cleaning, and anhydrous ethanol is used as a cleaning agent to remove residual abrasives, chemicals and other contaminants on the surface to obtain a clean laser crystal slice surface. The processing time of this stage is 20 minutes.

[0067] The total time was 3h42min.

[0068] Example 3

[0069] In this embodiment, the processed raw material is Φ15mm lutetium oxide, and the laser crystal slice is coarsely ground using a #600 cup grinding wheel. The grinding wheel speed is 1000rpm, the laser crystal slice self-rotation speed is 70rpm, the grinding wheel axial feed speed is 15um / min, and the processing time is 2.5h.

[0070] A #3000 cup-shaped grinding wheel was used. The total feed amount of the cup-shaped grinding wheel in the fine grinding stage was set to remove the damaged layer, referring to the depth value of the subsurface processing damage layer of the laser crystal slice in the rough grinding stage. The grinding wheel speed was 1000rpm, the rotation speed of the laser crystal slice was 70rpm, the axial feed speed of the grinding wheel was 15um / min, and the processing time in this stage was 10min.

[0071] Semi-finishing polishing process stage: set the xenon lamp with a wavelength of 254nm and a UV light intensity of 50-150mw / cm 2 Alumina abrasive was used to prepare a special polishing liquid for the semi-finishing stage of photochemical mechanical polishing. The laser crystal slice was semi-finished. The abrasive particle size was 20-500nm, the abrasive concentration was 25g / L, and 0.20g / L CuFe 2 O 4 、20g / L sodium dichromate Na 2 Cr 2 O 7 , pH regulator, total concentration of 1g / L polyvinyl pyrrolidone PVP, sodium polyacrylate SP, polyethylene glycol PEG2000, HNO 3 The pH value of the solution was adjusted to 5 to quickly remove surface defects such as scratches and pits caused by the grinding stage, and obtain a laser crystal slice with good surface morphology. The polishing load was 20 kPa, the polishing disc speed was 50 rpm, and the polishing liquid flow rate was 4 ml / min. The processing time of this stage was 60 min.

[0072] Fine polishing process stage: Use zirconium oxide abrasive with lower hardness to prepare photochemical mechanical polishing fine polishing special polishing liquid, polish the laser crystal slice after semi-fine polishing, the abrasive particle size is 20-500nm, the abrasive concentration is 25g / L, and also includes 0.20g / L CuFe 2 O 4 、20g / L sodium dichromate Na 2 Cr 2 O 7 , pH regulator, total concentration of 1g / L polyvinyl pyrrolidone PVP, sodium polyacrylate SP, polyethylene glycol PEG2000, HNO 3 The pH value of the solution was adjusted to 5 to further optimize the surface quality and surface accuracy of the workpiece. The polishing load was 20 kPa, the polishing disc speed was 50 rpm, the polishing liquid flow rate was 4 ml / min, and the processing time in this stage was 80 min.

[0073] The laser crystal slice after fine polishing is placed in an ultrasonic cleaner for cleaning, and anhydrous ethanol is used as a cleaning agent to remove residual abrasives, chemicals and other contaminants on the surface to obtain a clean laser crystal slice surface. The processing time of this stage is 20 minutes.

[0074] The total time is 5h20min.

[0075] In summary, compared with the traditional grinding and polishing process, the laser crystal slice ultra-precision grinding and photochemical mechanical polishing combined with the laser crystal slice processing of the present invention, taking Example 1 as an example, the processing efficiency is increased by nearly 3 times. Figure 5 As shown, other embodiments are even more efficient. At the same time, by using an optical microscope and a plane interferometer to detect the surface of the laser crystal slice, the surface roughness RMS <0.3nm, the surface / subsurface is free of damage, the surface accuracy PV <60nm (1 / 10λ@632.8nm) and the thickness is 100um~200um, as shown in FIG. Figure 3 , Figure 4 shown.

[0076] The metal oxide type (such as lutetium oxide crystal, sapphire crystal, etc.) and garnet crystal type (such as yttrium aluminum garnet (YAG), gadolinium gallium garnet, etc.) targeted by the present invention, especially yttrium aluminum garnet, is one of the materials with the greatest application potential in laser crystals. It is clearly different from diamond (molecular formula: C, type: atomic crystal) and silicon wafer (molecular formula: Si or SiC, type: atomic crystal or covalent compound). In terms of physical and chemical properties, there are significant differences between laser crystals and other substances.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A combined process of laser crystal thin slice ultra-precision grinding and photochemical mechanical polishing, characterized in that: The steps include: Step 1, rough grinding stage: paraffin is used to fix the laser crystal slice on the silicon wafer, and the silicon wafer is adsorbed on the vacuum suction cup worktable of the self-rotating ultra-precision grinding machine. During grinding, the grinding wheel and the laser crystal slice rotate around their respective axes respectively, and the grinding wheel is fed along the axial direction of the machine tool spindle, and deionized water is used as a coolant; a cup-type grinding wheel with a preset coarse fixed abrasive particle size is used to rough grind the laser crystal slice based on preset grinding parameters; Step 2, fine grinding stage: use a cup grinding wheel with a preset finer fixed abrasive grain size to fine grind the laser crystal slice; according to the depth value of the sub-surface processing damage layer obtained in the rough grinding stage, set the total amount of grinding wheel feed in the fine grinding stage to grind away the damage layer, and obtain good grinding surface / sub-surface quality and surface accuracy of the laser crystal slice by optimizing the grinding process parameters; Step 3, semi-finishing polishing stage: using paraffin wax to stick the ground laser crystal slice on the carrier plate, adding a counterweight block on the carrier plate to make the workpiece in close contact with the polishing pad on the polishing plate of the chemical mechanical polishing device; using aluminum oxide abrasive to prepare a special polishing liquid for the semi-finishing polishing stage of photochemical mechanical polishing, semi-finishing the laser crystal slice; Step 4, fine polishing stage: using zirconium oxide abrasive to prepare a special polishing liquid for the photochemical mechanical polishing fine polishing stage, and fine polishing the laser crystal slice after semi-fine polishing; In step 3 and step 4, ultraviolet light irradiation is performed by an ultraviolet light emitting device.

2. The combined process of laser crystal slice ultra-precision grinding and photochemical mechanical polishing according to claim 1, characterized in that: After step 4, step 5 is further provided, using anhydrous ethanol as a cleaning agent, and placing the finely polished laser crystal slice in an ultrasonic cleaning apparatus for cleaning.

3. The combined process of laser crystal slice ultra-precision grinding and photochemical mechanical polishing according to claim 1, characterized in that: In step 1, the cup wheel abrasive grain size is #325 or #600.

4. The combined process of laser crystal slice ultra-precision grinding and photochemical mechanical polishing according to claim 1, characterized in that: In step 2, the cup grinding wheel abrasive grain size is #1500 or #3000.

5. The combined process of ultra-precision grinding and photochemical mechanical polishing of laser crystal slices according to claim 1, characterized in that: In step 1 and step 2, the grinding wheel speed range is 1000-3000 rpm, the laser crystal slice self-rotation speed range is 60-240 rpm, and the grinding wheel axial feed speed range is 5-20 um / min.

6. The combined process of laser crystal thin slice ultra-precision grinding and photochemical mechanical polishing according to claim 1, characterized in that: The ultraviolet light emitting device is any one of a mercury lamp, a xenon lamp, a deuterium lamp and a bromine tungsten lamp, with a wavelength range of 180 to 1800 nm and an ultraviolet light intensity of 50 to 150 mw / cm 2 .

7. The combined process of laser crystal slice ultra-precision grinding and photochemical mechanical polishing according to claim 1, characterized in that: In step 3 and step 4, the polishing load is 10-40 kPa, the polishing disc speed is 50-90 rpm, and the polishing liquid flow rate is 2-14 ml / min.

8. The combined process of laser crystal slice ultra-precision grinding and photochemical mechanical polishing according to claim 1, characterized in that: In step 3 and step 4, the abrasive particle size in the special polishing liquid is 20-500 nm, and the abrasive concentration is 20-110 g / L.

9. The combined process of laser crystal slice ultra-precision grinding and photochemical mechanical polishing according to claim 1, characterized in that: In step 3 and step 4, in addition to aluminum oxide abrasive and zirconium oxide abrasive, the remaining additive components include 0.05-0.20 g / L semiconductor photocatalyst, 5-20 g / L electron capture agent, pH adjuster, 1-5 g / L abrasive dispersant, and the pH adjuster adjusts the pH value of the solution to 2-5.

10. The combined process of laser crystal slice ultra-precision grinding and photochemical mechanical polishing according to claim 1, characterized in that: The semiconductor photocatalyst is at least one of MnFe2O4, CuFe2O4 and CoFe2O4 spinel ferrites; the electron capture agent is at least one of hydrogen peroxide H2O2, peracetic acid CH3COOOH, sodium dichromate Na2Cr2O7 and potassium permanganate KMnO4; the regulator is one of HNO3, H2SO4, H2CO3 and phosphoric acid; the abrasive dispersant is at least one of sodium dodecylbenzene sulfonate SDBS, sodium hexametaphosphate SH, polyvinyl pyrrolidone PVP, sodium polyacrylate SP, polyethylene glycol PEG2000 and sodium tripolyphosphate STPP.

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