Chemical mechanical grinding method and device for semiconductor wafer

Abstract

The invention provides a chemical mechanical grinding method and device for a semiconductor wafer, and belongs to the technical field of wafer grinding. The chemical mechanical grinding method for the semiconductor wafer comprises the following steps that S1, the wafer is kept in a constant-speed rotating state after being positioned; s2, the ultraviolet light and the chemical grinding fluid act on the surface of the wafer at the same time, the chemical grinding fluid is evenly distributed on the surface of the wafer, and meanwhile the chemical grinding fluid and the surface of the wafer are subjected to a Fenton reaction under irradiation of the ultraviolet light; s3, the step S2 is continued, the grinding wheel is moved to the surface of the wafer, and grinding operation is started; and S4, after the grinding operation is stopped, adding of the chemical grinding fluid and ultraviolet irradiation are stopped, and the Fenton reaction is stopped. According to the chemical mechanical grinding method for the semiconductor wafer, a soft oxide layer is generated on the surface of the wafer to be machined through the ultraviolet light catalytic Fenton reaction, the surface hardness of the wafer to be machined is reduced, then the oxide layer is removed through the mechanical effect, the abrasion of a grinding wheel can be greatly reduced, and the surface quality of the wafer is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of wafer grinding, and more specifically, relates to a chemical mechanical grinding method and device for semiconductor wafers. Background Art

[0002] To become a qualified chip substrate, semiconductor materials need to go through a series of processes such as crystal growth, cutting, grinding, and polishing, and finally obtain an ultra-smooth surface without defects, edge collapse, and surface / subsurface damage. In order to stably achieve this goal, higher requirements are placed on the first surface processing process - grinding. Ultra-precision grinding technology can achieve rapid and large-scale removal of rough surfaces on wafers, reduce surface roughness, and improve flatness, which plays a decisive role in the smooth progress of subsequent polishing.

[0003] In the conventional precision grinding process, deionized water is used as the grinding fluid, and #325, #1000, #2000, and #3000 super-hard abrasive grinding wheels are used for rough grinding to remove the wire cutting marks and quickly remove the processing allowance; #6000, #8000, and #30000 grinding wheels are used for fine grinding to obtain a smooth, low-damage surface. During grinding, the grinding wheel is in direct contact with the wafer, and the material is brittlely removed under mechanical action. The grinding force is large, the grinding wheel is severely worn, and the grinding wheel needs to be frequently dressed, which increases the processing cost and prolongs the processing time. In addition, the mechanical action will cause a large amount of brittle damage, and the surface roughness of the wafer is large and the flatness is poor.

[0004] A single mechanical action will inevitably cause a large amount of brittle damage on the surface of the chip, affecting the surface roughness and flatness of the chip. In addition, since semiconductor chips are hard and brittle materials, the grinding wheel will be worn out during grinding, resulting in increased processing costs, reduced processing efficiency, and extended processing time. Summary of the invention

[0005] The object of the present invention is to provide a method and device for chemical mechanical grinding of semiconductor wafers, aiming to solve the problem that a single mechanical action causes a large amount of brittle damage on the wafer surface, resulting in poor surface flatness of the wafer.

[0006] To achieve the above object, the technical solution adopted by the present invention is: to provide a chemical mechanical grinding method for a semiconductor wafer, comprising the following steps: S1, the wafer is positioned and kept rotating at a constant speed; S2, ultraviolet light and chemical grinding fluid act on the wafer surface at the same time, the chemical grinding fluid is evenly distributed on the wafer surface, and Fenton reaction occurs with the wafer surface under the irradiation of ultraviolet light; S3, continuing step S2, then moving the grinding wheel to the surface of the wafer to start the grinding operation; S4, after the grinding operation is stopped, the addition of chemical grinding fluid and ultraviolet light irradiation are stopped to stop the Fenton reaction; S5. Clean and dry the wafer.

[0007] As another embodiment of the present application, in step S2, the wafer is rotated horizontally at a uniform speed so that the chemical grinding liquid sprayed at a uniform speed on the wafer surface is evenly distributed.

[0008] As another embodiment of the present application, in step S3, during the Fenton reaction, the chemical grinding fluid generates a strong oxidant under the catalytic reaction of ultraviolet light. , strong oxidants It undergoes an oxidation reaction with the wafer surface, forming an oxide layer with lower hardness on the wafer surface.

[0009] As another embodiment of the present application, the chemical grinding fluid includes deionized water, a photocatalyst, a Fenton reagent and a pH adjuster.

[0010] As another embodiment of the present application, in step S3, the abrasive grain size of the grinding wheel is .

[0011] As another embodiment of the present application, the illumination range of the ultraviolet light covers the entire surface of the wafer to be processed, the wavelength λ of the ultraviolet light is 300 to 550 nm, and the power is 100 to 2000 mW / cm 2 .

[0012] As another embodiment of the present application, the grinding wheel and the wafer rotate in opposite directions.

[0013] The beneficial effect of the chemical mechanical grinding method for semiconductor wafers provided by the present invention is that: compared with the prior art, the chemical mechanical grinding method for semiconductor wafers of the present invention generates a softer oxide layer on the surface of the wafer to be processed through ultraviolet light catalyzed Fenton reaction, reduces the surface hardness of the wafer to be processed, and then removes it by mechanical action, which can greatly reduce the grinding wheel loss and improve the surface quality of the wafer.

[0014] A chemical mechanical grinding device for a semiconductor wafer is also provided, comprising: A workbench, wherein the workbench is provided with a vacuum chuck, and the vacuum chuck is used to position the wafer and carry the wafer to rotate horizontally; A grinding body, located above the workbench, comprising a grinding wheel that can move longitudinally, with a working end of the grinding wheel facing downward; A liquid spray pipe, wherein the outlet end of the liquid spray pipe extends above the vacuum suction cup and toward the vacuum suction cup; An ultraviolet light source is located above the workbench and is used to irradiate the wafer on the vacuum chuck.

[0015] As another embodiment of the present application, the grinding body also includes an air spindle, the upper end of the air spindle is connected to a fixed frame, the air spindle can be swung along a longitudinal reference plane, and the air spindle has freedom along the length direction, and the grinding wheel is located at the lower end of the air spindle.

[0016] As another embodiment of the present application, an air passage is provided in the workbench, and the air passage is connected to the negative pressure adsorption chamber of the vacuum suction cup.

[0017] The beneficial effects of the chemical mechanical grinding device for semiconductor wafers provided by the present invention are as follows: compared with the prior art, the chemical mechanical grinding device for semiconductor wafers of the present invention can achieve continuous operation of the grinding wheel without dressing by adjusting parameters such as initial pressure, grinding wheel speed, workpiece disc speed, feed speed, ultraviolet light wavelength and power, grinding fluid ratio, etc.; the chemical mechanical grinding device for semiconductor wafers cooperates with the chemical mechanical grinding method to provide a buffer for the direct mechanical contact between the hard and brittle wafer and the grinding wheel, greatly reducing brittle damage such as micro-fragmentation, pits, micro-cracks on the wafer surface, reducing surface roughness, and improving the overall surface quality, which can improve the current problems of large spindle load, large grinding wheel loss, low grinding efficiency, poor wafer surface quality, etc. in grinding processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, 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 only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 A schematic structural diagram of a chemical mechanical grinding device for a semiconductor wafer provided by an embodiment of the present invention; Figure 2 A top view of a chemical mechanical grinding apparatus for a semiconductor wafer provided by an embodiment of the present invention; Figure 3 is an AFM topography image of the silicon carbide surface after chemical mechanical grinding in Example 1; Figure 4 The AFM morphology of the silicon carbide surface after mechanical grinding in Comparative Example 1; Figure 5 is an AFM topography image of the silicon carbide surface after chemical mechanical grinding in Example 2; Figure 6 This is the AFM morphology image of the silicon carbide surface after mechanical grinding in Comparative Example 2.

[0020] In the figure: 1. UV lamp; 2. Air spindle; 3. Left and right tilt angle control bolts and nuts; 4. Front and rear swing angle control bolts and nuts; 5. Grinding wheel base; 6. Grinding wheel abrasive segment; 7. Liquid spray pipe; 8. Thickness probe; 9. Wafer; 10. Vacuum suction cup; 11. Airway; 12. Workbench. DETAILED DESCRIPTION

[0021] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] See also Figure 1 and Figure 2 The chemical mechanical grinding method and device for semiconductor wafers provided by the present invention are now described. The chemical mechanical grinding method for semiconductor wafers comprises the following steps: S1, after the wafer 9 is positioned, it keeps rotating at a constant speed; S2, ultraviolet light and chemical grinding fluid act on the wafer surface at the same time, the chemical grinding fluid is evenly distributed on the wafer surface, and Fenton reaction occurs with the wafer surface under the irradiation of ultraviolet light; S3, continuing step S2, then moving the grinding wheel to the surface of the wafer to start the grinding operation; S4, after the grinding operation is stopped, the addition of chemical grinding fluid and ultraviolet light irradiation are stopped to stop the Fenton reaction; S5, the wafer 9 is cleaned and dried.

[0023] The chip substrate needs to be ground after cutting. The main purpose of grinding is to remove the wire cutting marks and quickly remove the processing allowance. Fine grinding and polishing will be performed after grinding. The difference between the two is that grinding has high efficiency and high speed, and can greatly remove the processing allowance while ensuring the surface quality as much as possible; polishing has low efficiency and slow speed, but the surface quality is high and the removal of less allowance is less. The specific performance is shown in Table 1.

[0024] Table 1 Comparison of the characteristics of grinding and polishing

[0025] The grinding currently used is mechanical grinding, which uses a grinding wheel to grind the surface of the wafer. This method causes a large amount of brittle damage to the surface of the wafer, and the surface roughness of the wafer is relatively large. Although the wafer 9 after grinding still needs to be finely ground and polished again, the surface and flatness of the wafer obtained by grinding will have a great impact on subsequent operations. The higher the precision and the better the flatness of the ground wafer 9, the higher the efficiency and the better the surface quality during the later polishing. Therefore, the present invention considers introducing chemical action into the process of ultra-precision grinding. Compared with the prior art, the chemical mechanical grinding method of the semiconductor wafer provided by the present invention generates a softer oxide layer on the surface of the wafer to be processed through ultraviolet light catalyzed Fenton reaction, reduces the surface hardness of the wafer 9 to be processed, and then removes it by mechanical action, which can greatly reduce the loss of the grinding wheel and improve the surface quality of the wafer.

[0026] The ultraviolet catalysis-Fenton reaction proposed in the present invention is combined with mechanical grinding to generate a softer oxide layer on the surface of the wafer to be processed through chemical reaction, thereby reducing the surface hardness of the wafer to be processed 9, thereby reducing the grinding force and spindle load, reducing the loss of the super-hard abrasive grinding wheel, and extending the service life of the machine tool. In addition, the use of chemical grinding fluid has a better lubrication effect. The grinding fluid continuously flushes the processing area, can clean up the grinding debris in time, and avoid clogging of the grinding wheel.

[0027] Specifically, during the grinding process, due to the large amount of material removed and high surface roughness, more debris and pollutants may be generated, which increases the Fenton reaction during the grinding process. The Fenton reaction produces a strong oxidant - hydroxyl radical ( ), hereinafter referred to as Strong oxidants can quickly oxidize and decompose organic matter and micron-sized particles, avoid equipment blockage caused by debris accumulation, and achieve real-time degradation of pollutants, reduce the complexity of subsequent cleaning steps, and improve overall process efficiency. Compared with traditional chemical oxidation methods, the present invention combines ultraviolet catalytic reaction with Fenton reaction, which greatly improves the efficiency of strong oxidants. The generation rate of the wafer 9 is further improved, and the oxidation efficiency is further improved by using ultraviolet light to directly illuminate the processing area, so that the generated Directly participate in the chemical reaction, avoiding the liquid transportation process By dynamically adjusting the wavelength and power of the UV lamp 1 and the distribution ratio of each group of chemical grinding fluid, it can be coordinated with the mechanical action under the condition of micro-feeding, so as to achieve high-efficiency and low-damage flattening processing of semiconductor wafers. And Fenton reagent is safe and pollution-free, and will not harm the environment.

[0028] Since the grinding speed is very fast and the mechanical action is greater than the chemical action, the introduction of a stronger oxidation reaction such as UV-Fenton is likely to achieve a balance between chemistry and mechanics.

[0029] The grinding method that combines chemical reaction and mechanical grinding provides a buffer for the direct mechanical contact between the hard and brittle wafer and the grinding wheel, greatly reducing the brittle damage such as micro-fragmentation, pits, micro-cracks on the wafer surface, reducing the surface roughness, and improving the overall surface quality. It can improve the current problems in grinding processing, such as heavy spindle load, large grinding wheel loss, low grinding efficiency, and poor wafer surface quality.

[0030] Specifically, in step S1 , the wafer 9 needs to be fixed on a rotatable workbench 12 , and an air spindle 2 for mounting a grinding wheel is arranged above the workbench 12 . The grinding wheel is located at the lower end of the air spindle 2 and is lifted and lowered by the air spindle 2 .

[0031] Before installing the wafer 9, it is necessary to adjust the front and rear tilt angle and left and right swing angle of the air spindle 2 according to the processing surface requirements of the wafer 9, install a dressing wheel at the lower end of the air spindle 2, and use the dressing wheel to dress the workbench 12. Then replace the dressing wheel with a grinding wheel, brush the rotating workbench 12, and place the wafer 9 to be processed on the upper end of the workbench 12 and fix it by vacuum adsorption.

[0032] In step S2, the ultraviolet lamp 1 is turned on, and the chemical grinding liquid is sprayed onto the surface of the wafer by the nozzle, and the workbench 12 is turned on at the same time; as the workbench 12 rotates horizontally, the chemical grinding liquid is evenly distributed on the crystal surface, and under the photocatalysis of ultraviolet light, the chemical grinding liquid reacts with the crystal surface.

[0033] In step S3, the irradiation of the ultraviolet lamp 1 and the spraying of the chemical grinding liquid in step S2 are continued, and then the grinding wheel is fed down longitudinally to the surface of the wafer to start the grinding operation; during grinding, the workbench 12 and the grinding wheel perform planar rotational motion in the clockwise / counterclockwise direction; the two rotate in opposite directions.

[0034] During grinding, the ultraviolet light and the chemical grinding fluid undergo a Fenton reaction. During the Fenton reaction, the chemical grinding fluid generates a strong oxidant under the catalytic reaction of ultraviolet light. , strong oxidants It undergoes an oxidation reaction with the wafer surface, forming an oxide layer with lower hardness on the wafer surface.

[0035] After the wafer 9 is ground to a set thickness in step S3, the grinding wheel spindle is raised and stops rotating; step S4 is entered, the addition of chemical grinding fluid and the irradiation of the ultraviolet lamp 1 are stopped to stop the Fenton reaction; after stopping, the wafer 9 is removed from the workbench 12. Finally, the wafer 9 removed in step S4 is sent to a cleaning device for cleaning and drying.

[0036] Some of the parameters in the above method are as follows: The range of the front and rear tilt angle and left and right swing angle of the air spindle 2 is -0.1° +0.1°.

[0037] UV lamp 1 wavelength λ is 300~550nm, power is 100~2000mW / cm 2 .

[0038] The rotatable workbench 12 has an air passage inside, and negative pressure air holes are left on the surface of the workbench 12, and the negative pressure air holes are connected to the air passage. The wafer is attached to the surface of the workbench 12 and fixed by the negative pressure adsorption of the negative pressure air holes. The vacuum pressure at the negative pressure air holes is -10 to -20 InHg, and the rotation speed is 50 to 500 rpm.

[0039] The grinding wheel speed is 800-4000rpm, the feed speed is 0.01-1μm / s, the abrasive is one or more of diamond, silicon carbide, aluminum oxide and boron carbide, and the grinding wheel abrasive particle size is .

[0040] The diameters of standard semiconductor wafers to be processed include but are not limited to 2, 4, 6, 8, 10, and 12 inches, and the materials include but are not limited to silicon, gallium nitride, silicon carbide, and diamond.

[0041] The chemical grinding fluid is a standard process configuration, and its components include: deionized water, photocatalyst, Fenton reagent, and pH regulator.

[0042] In the above grinding method, the chemical part designs the combined effect of ultraviolet catalytic reaction and Fenton reaction, and takes silicon carbide wafer as an example to illustrate the reaction principle: The Fenton reaction is a strong oxidation reaction. Add Promotes strong oxidants - hydroxyl radicals ( ) is generated, and the reaction equation is shown in (1). Ultraviolet light catalysis can also generate strong oxidants , the reaction equations are shown in (2) and (3).

[0043] + → + + (1) + hv → + (2) +2 →2 (3) As shown in reaction equation (4), a strong oxidant Reacts with SiC to generate low-hardness SiO on the wafer surface 2The reaction layer is removed by the grinding wheel through mechanical action, and then a new SiC surface is exposed to continue the reaction, and the cycle is repeated to perform high-efficiency and low-damage grinding processing on the SiC wafer 9, which can greatly reduce the wear of the grinding wheel and improve the surface quality of the wafer.

[0044] SiC+4 +O 2 →SiO 2 +CO 2 +2H 2 O(4) During the reaction, the workbench 12 is rotated so that the workbench 12 drives the wafer 9 to rotate horizontally at a uniform speed, and the chemical grinding liquid is sprayed on the surface of the wafer at a uniform speed so that the chemical grinding liquid is evenly distributed on the surface of the wafer.

[0045] During the Fenton reaction, the synchronous irradiation of UV light can promote Restore to reaction, maintaining the catalytic cycle and improving the efficiency of the Fenton reaction; and ultraviolet light directly excites Decomposition, synergistic with the Fenton reaction, accelerates the reaction of organic matter.

[0046] Compared with the process of applying the Fenton reaction solution to the wafer surface after UV catalysis, the direct reaction of UV light with the chemical grinding fluid on the wafer surface can reduce the deactivation rate of the chemical grinding fluid, ensure the efficiency of the catalytic reaction, and promote the real-time The reduction reaction proceeds, and the ultraviolet light can directly excite the surface active sites of the chip (such as TiO 2 wafer), promote electron transfer and free radical generation, cooperate with Fenton reaction to further improve reaction efficiency, and reduce energy loss caused by premature reaction.

[0047] Example 1 The above chemical mechanical grinding method is used to perform rough grinding of semiconductor silicon carbide wafers. The equipment is a self-rotating grinding machine. The processing schematic diagram is shown in FIG. Figure 1 and Figure 2 The processed wafer is an 8-inch silicon carbide wafer with a thickness of 560 μm and an initial surface roughness of 5 μm. The parameters are set according to the rough grinding process. Diamond grinding wheel, initial pressure 20 lbs, workpiece disc speed 100 rpm, grinding wheel speed 1500 rpm, feed speed 0.30 μm / s, total processing volume 60 μm. UV lamp 1 wavelength 365 nm, light intensity 1000 mW / cm 2 , chemical grinding fluid is standard configuration.

[0048] Step S1: According to the processing surface requirements, adjust the front and rear inclination angles of the spindle to -0.0041° and the left and right swing angles to -0.0043°, install the dressing wheel, and dress the rotary table 12; replace the dressing wheel with a grinding wheel, brush the rotary table 12, place an 8-inch silicon carbide wafer on the rotary table 12, and fix it by vacuum adsorption.

[0049] Step S2: Turn on the UV lamp 1, set the wavelength to 365nm, and the light intensity to 1000mW / cm 2 , the light covers the entire processing area, and at the same time, the chemical grinding fluid is sprayed uniformly from the nozzle to the surface of the wafer; under the influence of ultraviolet light, the silicon carbide wafer reacts chemically with the chemical grinding fluid to form a silicon dioxide oxide layer on the surface, and the surface hardness of the wafer is greatly reduced; the rotating table 12 rotates clockwise at a uniform speed of 100rpm, and the grinding wheel rotates counterclockwise at a uniform speed of 1500rpm.

[0050] Step S3: The grinding spindle descends along the Z axis at a feed rate of 0.30 μm / s to start the grinding operation; after the wafer 9 is ground from 560 μm to 500 μm, the grinding wheel spindle rises and stops rotating; Step S4: the UV lamp 1 and the grinding fluid nozzle are turned off, and the wafer 9 is removed from the rotating table 12; Step S5: Send the wafer 9 to a cleaning device, rinse it clean and dry it using standard processes.

[0051] Comparative Example 1 The existing mechanical grinding method is used to rough grind the semiconductor silicon carbide wafer. The equipment is a self-rotating grinding machine. The processed wafer is an 8-inch silicon carbide wafer with a thickness of 560μm and an initial surface roughness of 5μm. The parameters are set according to the rough grinding process. Diamond grinding wheel, initial pressure 20 lbs, workpiece disc speed 100 rpm, grinding wheel speed 1500 rpm, feed rate 0.30 μm / s, total machining volume 60 μm.

[0052] Step S1: According to the processing surface requirements, adjust the front and rear inclination angles of the spindle to -0.0041° and the left and right swing angles to -0.0043°, install the dressing wheel, and dress the rotary table 12; replace the dressing wheel with a grinding wheel, brush the rotary table 12, place an 8-inch silicon carbide wafer on the rotary table 12, and fix it by vacuum adsorption.

[0053] Step S2: Deionized water is sprayed uniformly onto the wafer surface from the nozzle; the rotating table 12 rotates clockwise at a uniform speed of 100 rpm, and the grinding wheel rotates counterclockwise at a uniform speed of 1500 rpm.

[0054] Step S3: The grinding spindle descends along the Z axis at a feed rate of 0.30 μm / s to start the grinding operation; after the wafer is ground from 560 μm to 500 μm, the grinding wheel spindle rises and stops rotating; Step S4: Send the wafer 9 to a cleaning device, rinse it clean and dry it using standard processes.

[0055] According to Example 1 and Comparative Example 1, it can be concluded that as shown in Table 2, under the same process conditions, after the introduction of the UV-Fenton reaction, the processing time is reduced to 410s, the grinding pressure is reduced to 43 lbs, and the grinding wheel wear ratio is reduced to 95%. The initial surface roughness of silicon carbide is 5μm, and the roughness is reduced to 15nm after chemical mechanical grinding, and the flatness TTV is 6μm, which is a significant improvement compared to the existing mechanical grinding process.

[0056] Table 2 Comparison table of mechanical grinding and chemical mechanical grindinga

[0057] Example 2 The above chemical mechanical grinding method is used to perform rough grinding of semiconductor silicon carbide wafers. The equipment is a self-rotating grinding machine. The processing schematic diagram is shown in FIG. Figure 1 and Figure 2 The processed wafer 9 is an 8-inch silicon carbide wafer with a thickness of 440 μm and an initial surface roughness of 30 nm. The parameters are set according to the fine grinding process. Diamond grinding wheel, initial pressure 35lbs, workpiece disc speed 300rpm, grinding wheel speed 3500rpm, feed speed 0.10μm / s, total processing volume 15μm. UV lamp 1 wavelength 405nm, light intensity 1500mW / cm 2 , chemical grinding fluid is standard configuration.

[0058] Step S1: According to the processing surface requirements, adjust the front and rear inclination angles of the spindle to -0.0041° and the left and right swing angles to -0.0056°, install the dressing wheel, and dress the rotary table 12; replace the dressing wheel with a grinding wheel, brush the rotary table 12, place an 8-inch silicon carbide wafer on the rotary table 12, and fix it by vacuum adsorption.

[0059] Step S2: Turn on the UV lamp 1, set the wavelength to 405nm, and the light intensity to 1500mW / cm 2 , the light covers the entire processing area, and at the same time, the chemical grinding fluid is sprayed uniformly from the nozzle to the surface of the wafer; under the influence of ultraviolet light, the silicon carbide wafer reacts chemically with the chemical grinding fluid to form a silicon dioxide oxide layer on the surface, and the surface hardness of the wafer is greatly reduced; the rotating table 12 rotates clockwise at a uniform speed of 300rpm, and the grinding wheel rotates counterclockwise at a uniform speed of 3500rpm.

[0060] Step S3: The grinding spindle descends along the Z axis at a feed rate of 0.10 μm / s to start the grinding operation; after the wafer 9 is ground from 440 μm to 425 μm, the grinding wheel spindle rises and stops rotating; Step S4: the UV lamp 1 and the grinding fluid nozzle are turned off, and the wafer 9 is removed from the rotating table 12; Step S5: Send the wafer 9 to a cleaning device, rinse it clean and dry it using standard processes.

[0061] Comparative Example 2 The semiconductor silicon carbide wafer is roughly ground using the existing mechanical grinding method, and the equipment is a self-rotating grinding machine. The processed wafer 9 is an 8-inch silicon carbide wafer with a thickness of 440μm and an initial surface roughness of 30nm. The parameters are set according to the needs of fine grinding, and the Diamond grinding wheel, initial pressure 35 lbs, workpiece disc speed 300 rpm, grinding wheel speed 3500 rpm, feed rate 0.10 μm / s, total processing volume 15 μm.

[0062] Step S1: According to the processing surface requirements, adjust the front and rear inclination angles of the spindle to -0.0041° and the left and right swing angles to -0.0056°, install the dressing wheel, and dress the rotary table 12; replace the dressing wheel with a grinding wheel, brush the rotary table 12, place an 8-inch silicon carbide wafer on the rotary table 12, and fix it by vacuum adsorption.

[0063] Step S2: Deionized water is sprayed uniformly onto the wafer surface from the nozzle; the rotating table 12 rotates clockwise at a uniform speed of 300 rpm, and the grinding wheel rotates counterclockwise at a uniform speed of 3500 rpm.

[0064] Step S3: The grinding spindle descends along the Z axis at a feed rate of 0.10 μm / s to start the grinding operation; after the wafer 9 is ground from 440 μm to 425 μm, the grinding wheel spindle rises and stops rotating; Step S4: Send the wafer 9 to a cleaning device, rinse it clean and dry it using standard processes.

[0065] According to Example 2 and Comparative Example 2, it can be concluded that as shown in Table 3, under the same process conditions, after the introduction of the UV-Fenton reaction, the processing time is reduced to 380s, the grinding pressure is reduced to 39 lbs, and the grinding wheel wear ratio is reduced to 130%. The initial surface roughness of silicon carbide is 30nm, and the roughness is reduced to 3nm after chemical mechanical grinding, and the flatness TTV is 4μm, which is a significant improvement compared to the existing mechanical grinding process.

[0066] Table 3 Comparison table of mechanical grinding and chemical mechanical grinding b

[0067] According to the descriptions in Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Tables 2 and 3, it can be seen that chemical mechanical grinding can reduce processing time, reduce grinding wheel loss, and improve processing efficiency compared to pure mechanical grinding. On this basis, the surface quality of the chip 9 is further improved, paving the way for subsequent processes.

[0068] Example 3 The process of the present invention is used to perform rough grinding of a semiconductor gallium nitride wafer. The equipment is a self-rotating grinding machine. The processed wafer 9 is a 4-inch gallium nitride wafer with a thickness of 540 μm and an initial surface roughness of 100 nm. The parameters are set according to the rough grinding process requirements. Diamond grinding wheel, initial pressure 15 lbs, workpiece disc speed 100 rpm, grinding wheel speed 1500 rpm, feed speed 0.2 μm / s, total processing volume 40 μm. UV lamp 1 wavelength 365 nm, light intensity 500 mW / cm 2 , chemical grinding fluid is standard configuration.

[0069] Step S1: According to the processing surface requirements, adjust the front and rear inclination angles of the spindle to -0.02° and the left and right swing angles to -0.01°, install the dressing wheel, and dress the rotary table 12; replace the dressing wheel with a grinding wheel, brush the rotary table 12, place a 4-inch gallium nitride wafer on the rotary table 12, and fix it by vacuum adsorption.

[0070] Step S2: Turn on the UV lamp 1, set the wavelength to 365nm, and the light intensity to 500mW / cm 2 , the light covers the entire processing area, and the chemical grinding fluid is sprayed uniformly from the nozzle to the surface of the wafer. Under the influence of ultraviolet light, the gallium nitride wafer reacts with the chemical grinding fluid to form a gallium oxide layer on the surface, and the surface hardness of the wafer is greatly reduced; the rotating table 12 rotates clockwise at a uniform speed of 100rpm, and the grinding wheel rotates counterclockwise at a uniform speed of 1500rpm.

[0071] Step S3: The grinding spindle descends along the Z axis at a feed rate of 0.2 μm / s to start the grinding operation; after the wafer 9 is ground from 540 μm to 500 μm, the grinding wheel spindle rises and stops rotating; Step S4: the UV lamp 1 and the grinding fluid nozzle are turned off, and the wafer 9 is removed from the rotating table 12; Step S5: Send the wafer 9 to a cleaning device, rinse it clean and dry it using standard processes.

[0072] Furthermore, according to Example 1, Example 2, and Example 3, it is proved that the chemical mechanical grinding method can be applied to a variety of wafer materials, such as silicon, gallium nitride, silicon carbide, diamond, etc., and has a wide range of applications.

[0073] A chemical mechanical grinding device for semiconductor wafers is also proposed, comprising a workbench 12, a grinding body, a liquid spray pipe 7 and an ultraviolet light source; a vacuum suction cup 10 is provided on the workbench 12, and the vacuum suction cup 10 is used to position the wafer 9 and carry the wafer 9 for horizontal rotation; the grinding body is located above the workbench 12, and the grinding body comprises a grinding wheel that can be moved longitudinally, and the working end of the grinding wheel faces downward; the outlet end of the liquid spray pipe 7 extends to above the vacuum suction cup 10 and faces the vacuum suction cup 10; the ultraviolet light source is located above the workbench 12, and is used to irradiate the wafer 9 on the vacuum suction cup 10.

[0074] Compared with the prior art, the chemical mechanical grinding device for semiconductor wafers provided by the present invention can achieve continuous operation without the need for grinding wheel dressing by adjusting parameters such as initial pressure, grinding wheel speed, workpiece disc speed, feed speed, ultraviolet light wavelength and power, and grinding fluid ratio.

[0075] By utilizing the chemical mechanical grinding device for semiconductor wafers as described above and in conjunction with the chemical mechanical grinding method, a buffer is provided for the direct mechanical contact between the hard and brittle wafer 9 and the grinding wheel, thereby greatly reducing brittle damage such as micro-fractures, pits, and micro-cracks on the wafer surface, reducing the surface roughness, and improving the overall surface quality. This can improve the current problems in grinding processing, such as heavy spindle load, large grinding wheel loss, low grinding efficiency, and poor wafer surface quality.

[0076] Among them, the vacuum suction cup 10 of the workbench 12 is made of microporous ceramics, with a dense structure and easy to clean. The surface shape can be trimmed by a grinding wheel and can be used repeatedly. During operation, the wafer 9 is firmly fixed on the surface by the vacuum negative pressure, and the ground wafer has a good flatness. The workbench 12 has an airway 11, which is connected to the negative pressure adsorption chamber of the vacuum suction cup 10; the other end of the airway 11 is connected to a negative pressure adsorption device, such as a vacuum pump. A thickness measuring probe 8 can also be set on the workbench 12, and the thickness of the wafer 9 is monitored in real time by the thickness measuring probe 8.

[0077] The grinding body also includes an air spindle 2, the upper end of which is connected to a fixed frame, and the air spindle 2 can be swung along the longitudinal reference plane, and the air spindle 2 has a degree of freedom along the length direction, and the grinding wheel is located at the lower end of the air spindle 2. The air spindle 2 can achieve angle adjustment, can reduce the grinding force, and can obtain the corresponding wafer surface shape according to requirements. The upper end of the air spindle 2 has left and right inclination control bolts and nuts 3 and front and rear swing angle control bolts and nuts 4. When adjusting, the swing angle and inclination of the air spindle 2 are changed by changing the above two angle control bolts and nuts. The axial directions of the left and right inclination control bolts and nuts 3 and the front and rear swing angle control bolts and nuts 4 are vertical. The grinding wheel includes a grinding wheel base 5 installed at the lower end of the air spindle 2, and a grinding wheel abrasive block 6 protruding downward is provided on the grinding wheel base 5.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for chemical mechanical grinding of a semiconductor wafer, characterized in that: The following steps are involved: S1, the wafer is positioned and kept rotating at a constant speed; S2, ultraviolet light and chemical grinding fluid act on the wafer surface at the same time, the chemical grinding fluid is evenly distributed on the wafer surface, and Fenton reaction occurs with the wafer surface under the irradiation of ultraviolet light; S3, continuing step S2, moving the grinding wheel to the surface of the wafer and starting the grinding operation; S4, after the grinding operation is stopped, the addition of chemical grinding fluid and ultraviolet light irradiation are stopped to stop the Fenton reaction; S5. Clean and dry the wafer.

2. The chemical mechanical grinding method for a semiconductor wafer according to claim 1, wherein: In step S2, the wafer is rotated horizontally at a constant speed so that the chemical grinding liquid sprayed at a constant speed on the wafer surface is evenly distributed.

3. The chemical mechanical grinding method for a semiconductor wafer according to claim 2, wherein: In step S3, during the Fenton reaction, the chemical grinding fluid generates a strong oxidant under the catalytic reaction of ultraviolet light. , strong oxidants It undergoes an oxidation reaction with the wafer surface, forming an oxide layer with lower hardness on the wafer surface.

4. The chemical mechanical grinding method for a semiconductor wafer according to claim 3, wherein: The chemical grinding fluid includes deionized water, a photocatalyst, a Fenton reagent and a pH adjuster.

5. The chemical mechanical grinding method for a semiconductor wafer according to claim 1, wherein: In step S3, the abrasive grain size of the grinding wheel is .

6. The chemical mechanical grinding method for a semiconductor wafer according to claim 1, wherein: The illumination range of the ultraviolet light covers the entire surface of the wafer to be processed. The wavelength λ of the ultraviolet light is 300~550nm, and the power is 100~2000mW / cm 2 .

7. The chemical mechanical grinding method for a semiconductor wafer according to claim 1, wherein: The grinding wheel and the wafer rotate in opposite directions.

8. A chemical mechanical grinding device for semiconductor wafers, characterized in that: include: A workbench, wherein the workbench is provided with a vacuum chuck, and the vacuum chuck is used to position the wafer and carry the wafer to rotate horizontally; A grinding body, located above the workbench, comprising a grinding wheel that can move longitudinally, with a working end of the grinding wheel facing downward; A liquid spray pipe, wherein the outlet end of the liquid spray pipe extends above the vacuum suction cup and toward the vacuum suction cup; An ultraviolet light source is located above the workbench and is used to irradiate the wafer on the vacuum chuck.

9. The chemical mechanical grinding device for semiconductor wafers according to claim 8, characterized in that: The grinding body also includes an air spindle, the upper end of which is connected to a fixed frame, the air spindle can be swung along a longitudinal reference plane, and the air spindle has a degree of freedom along the length direction, and the grinding wheel is located at the lower end of the air spindle.

10. The chemical mechanical grinding device for semiconductor wafers according to claim 8, characterized in that: An air passage is provided in the workbench, and the air passage is connected to the negative pressure adsorption chamber of the vacuum suction cup.

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