Glass flatness correction method

Abstract

The invention relates to a glass flatness correction method. The method for correcting the flatness of the glass comprises the following steps: carrying out a first group of polishing on the glass, namely alternately carrying out a polishing step A and a polishing step B on the glass; the polishing step A is a polishing correction step for generating a surface type effect of low center and high periphery after one surface of the glass is polished for one time; and the polishing step B is a polishing correction step for generating a surface type effect of high center and low periphery after one surface of the glass is polished for one time. According to the glass flatness correction method, accumulation of glass surface type defects in the polishing correction process can be avoided through surface type complementation, and finally the glass flatness can be corrected to be 0.5 micron or below.

Description

Technical Field

[0001] The invention relates to the field of processing components related to photolithography technology, and in particular to a glass flatness correction method. Background Art

[0002] At present, almost all modern chips need to be manufactured using photolithography. The principle of photolithography is to transmit light through a mask with a circuit diagram, scale down the circuit diagram on the mask and map it onto the photoresist on the surface of the silicon wafer, and then go through a series of subsequent processing such as development, hardening, etching, etc. to finally get the chip.

[0003] The mask is the master of the pattern on the wafer, so the performance of the mask directly affects the quality of the photolithography process. The mask is mainly composed of two parts: the mask substrate and the light-shielding film. The mask substrate is divided into a resin substrate and a glass substrate, which are used for different process requirements. Quartz glass has stable chemical properties, high optical transmittance, and low thermal expansion coefficient. Quartz glass mask substrates are currently widely used in the production of ultra-large-scale integrated circuit masks.

[0004] In order for the performance of the mask to meet the requirements of the subsequent photolithography process, the flatness of the glass used as the substrate must first meet certain standards. As chips develop towards ultra-high speed, integration, and intelligence, the technical nodes of integrated circuits continue to shrink, and the requirements for the flatness of mask substrates, especially the front side of the substrate, continue to increase. At present, the flatness is often graded according to different flatness levels such as 2μm, 1μm, and 0.5μm. The product technology nodes and product added value corresponding to different levels of flatness vary greatly. Masks with unqualified flatness have fluctuations in the focus position when imaging on the wafer surface, resulting in a reduction in the photolithography process window, affecting the quality and accuracy of the photolithography. Strictly controlling the flatness of the quartz glass substrate helps to ensure that the fluctuations in the focus position are much smaller than the focus depth, thereby ensuring the quality of the photolithography process. Flatness, also known as flatness, is usually expressed using the total indicator reading (TIR), which is usually expressed using The flatness measuring machine can directly measure it. TIR refers to the sum of the absolute values ​​of the maximum positive and negative deviations between the substrate surface and the reference plane, with the surface with the smallest sum of intercepts between the substrate surface and all points in the local area as the reference plane when the substrate is in close contact. Therefore, the larger the TIR value, the worse the flatness effect.

[0005] The current mainstream flatness correction method is usually chemical mechanical polishing (CMP). Double-sided polishing machine is a commonly used CMP tool, such as Figure 1 and Figure 2As shown, it includes an upper polishing disc 11, an electric push rod, a lower polishing disc 12, a base 20, an upper polishing pad 13, a lower polishing pad 14, an inner gear ring 15, an outer gear ring 16, a plurality of planetary wheels 17, four motors and a polishing liquid supply pipeline (the electric push rod, the motor and the polishing liquid supply pipeline are not shown in the figure). The upper polishing disc 11 is rotatably mounted on the electric push rod and can be moved up and down in the vertical direction by the electric push rod. The rotating shaft of the upper polishing disc 11 is connected to an independent motor and is driven to rotate independently by the motor. The lower polishing disc 12 is rotatably mounted on the base 20, and its rotating shaft is connected to an independent motor and is driven to rotate independently by the motor. The lower polishing disc 12 and the upper polishing disc 11 are arranged parallel to each other with their axes facing each other. The upper polishing pad 13 and the lower polishing pad 14 are respectively covered on the opposite surfaces of the upper polishing disc 11 and the lower polishing disc 12, and the thickness of the upper polishing pad 13 and the lower polishing pad 14 is 0.5-5mm. The diameter of the inner gear ring 15 is smaller than that of the lower polishing plate 12, and the outer ring is provided with teeth. It is rotatably mounted on the base 20 and located between the upper polishing plate 11 and the lower polishing plate 12. Its rotation center line coincides with the rotation center line of the lower polishing plate, and its rotation shaft is connected to an independent motor and is driven to rotate independently by the motor. A through hole is provided inside the planetary wheel for placing the glass 19 workpiece; the outer ring of the planetary wheel 17 has teeth, and several planetary wheels 17 mesh with the outer ring teeth of the inner gear ring 15, and the planetary wheels do not contact each other. The diameter of the outer gear ring 16 is larger than that of the inner gear ring 15, and it is rotatably mounted on the base 20 and located in the same plane as the inner gear ring 15. The rotation center line coincides with the rotation center line of the inner gear ring 15, and its rotation shaft is connected to an independent motor and is driven to rotate independently by the motor; the inner ring is provided with teeth and meshes with the planetary wheel. The upper polishing disc 11 is also provided with a liquid guide hole 18 , and the polishing liquid supply pipeline sprays the polishing liquid onto the upper polishing disc 11 . The polishing liquid can flow along the liquid guide hole 18 to the upper polishing pad, and then further infiltrate between the upper and lower polishing pads and the glass 19 .

[0006] When polishing the glass, the upper polishing disc 11 is lifted up, and the glass is placed in the through hole of the planetary wheel 17. The upper polishing disc 11 is pressed down with a certain processing pressure, so that the upper polishing disc 11 and the lower polishing disc 12 apply pressure to the upper surface (reverse side) and the lower surface (front side) of the glass through the upper polishing pad 13 and the lower polishing pad 14 respectively. The upper polishing disc 11 and the lower polishing disc 12 rotate respectively, driving the upper polishing pad 13 and the lower polishing pad 14 to rub the glass. The polishing liquid infiltrates through the polishing liquid supply pipe and the liquid guide hole 18. Because the polishing liquid contains cerium dioxide, under the action of the polishing pressure, the Ce atoms of cerium dioxide in the polishing liquid can react with the Si-O bonds in the quartz glass to form Ce-O-Si bonds, and the quartz glass will form a shaving mass and be peeled off by the cerium dioxide abrasive particles, and be polished away when the polishing pad rubs against the glass. At the same time, the inner gear ring 15 and the outer gear ring 16 rotate at different speeds, driving the planetary wheel 17 and the glass 19 therein to rotate and revolve, so that all parts of the glass surface are evenly polished and the flatness of the glass 19 is corrected. CMP combines chemical reaction and mechanical grinding, which can effectively avoid surface damage caused by simple mechanical polishing and defects such as slow polishing speed, poor surface flatness and polishing consistency caused by simple chemical polishing. The double-sided polishing machine polishes the front and back of the glass at the same time, which can effectively improve the uniformity, stability and optical quality of the glass 19.

[0007] In the prior art, technicians usually use a double-sided polishing machine to perform a first set of rough polishing and a second set of fine polishing on the glass 19. The first set of rough polishing mainly determines the flatness of the glass 19, while the second set of fine polishing is to remove scratches on the glass surface, reduce the surface roughness of the glass 19, and facilitate the downstream coating process. During the rough polishing, technicians usually adjust and optimize the parameters of the double-sided polishing machine, such as the rotation speed, processing pressure, and processing time, to remove the excessively high parts of the glass surface, preliminarily optimize the flatness, and reduce the thickness difference of the same batch of glass; then further polish the glass surface to optimize the flatness. However, technicians have found that the existing methods are still difficult to achieve a high degree of flatness, especially difficult to achieve a flatness below 0.5μm. Summary of the invention

[0008] Based on this, the object of the present invention is to provide a glass flatness correction method: comprising performing a first set of polishing on the glass, including alternately performing a polishing step A and a polishing step B on the front side of the glass;

[0009] The polishing step A is a polishing correction step for producing a surface effect of a low center and high surroundings after a single polishing of one side of the glass;

[0010] The polishing step B is a polishing correction step for producing a high center and low surrounding surface effect after a single polishing of one side of the glass.

[0011] The glass flatness correction method of the present invention can avoid the accumulation of glass surface defects during the polishing correction process by surface complementation, and can ultimately correct the glass flatness to below 0.5 μm.

[0012] Further, polishing step A is performed first, and then polishing step B is performed.

[0013] Furthermore, while the polishing correction step is being performed on the front side of the glass, the back side of the glass is polished.

[0014] Further, both polishing step A and polishing step B use a double-sided polishing machine, which includes an upper polishing disc, a lower polishing disc, an upper polishing pad, a lower polishing pad, an inner gear ring, an outer gear ring, and a plurality of planetary wheels;

[0015] The upper polishing disc can rotate independently;

[0016] The lower polishing plate can rotate independently; the lower polishing plate and the upper polishing plate are arranged parallel to each other with their axes facing each other; the upper polishing plate and the lower polishing plate can move away from or close to each other;

[0017] The upper polishing pad and the lower polishing pad cover the surfaces opposite to the upper polishing plate and the lower polishing plate respectively;

[0018] The inner gear ring is located between the upper polishing plate and the lower polishing plate, and its rotation center line coincides with the rotation center line of the lower polishing plate. It can rotate independently, and its diameter is smaller than that of the lower polishing plate. The outer ring is provided with teeth;

[0019] The outer ring of the planetary gear has teeth and a through hole is provided inside; a number of planetary gears mesh with the outer ring teeth of the inner gear ring, and the planetary gears do not contact each other;

[0020] The outer gear ring can rotate independently, and the rotation center line coincides with the rotation center line of the inner gear ring. The inner ring is provided with teeth, which mesh with the planetary gear.

[0021] In polishing step A, the load speed ratio of the upper polishing plate relative to the lower polishing plate is 50-80%, the load speed ratio of the inner gear ring relative to the lower polishing plate is 80-100%, and the load speed ratio of the outer gear ring relative to the lower polishing plate is 5-30%, wherein the lower polishing plate has opposite rotation directions to the upper polishing plate, the inner gear ring, and the outer gear ring.

[0022] This step can make a preliminary correction to the flatness of the glass. The glass has a surface that is low in the center and high around. If it is a flatness correction for batch glass, the thickness difference of the same batch of glass can be reduced to within 20μm.

[0023] Furthermore, in polishing step B, the load speed ratio of the upper polishing disc to the lower polishing disc is 50-80%, the load speed ratio of the inner gear ring to the lower polishing disc is 80-100%, and the load speed ratio of the outer gear ring to the lower polishing disc is 20-50%, wherein the rotation direction of the lower polishing disc, the upper polishing disc, the inner gear ring, and the outer gear ring are opposite. This step can further correct the flatness of the glass to less than 0.5μm. At the same time, the load speed ratio can change the shape of the front surface of the glass in the direction of high center and low surroundings during a single polishing, so it is finally superimposed with the surface shape effect of polishing step A to optimize the flatness.

[0024] Furthermore, in the polishing step A, the rotation speed of the lower polishing disc is 10-50 rpm.

[0025] Furthermore, in the polishing step B, the rotation speed of the lower polishing disc is 5-30 rpm.

[0026] Furthermore, in the polishing step A, the pressure applied by the upper polishing disc and the lower polishing disc to the glass is 20-50 g / cm 2 , polishing time is 2-4 hours.

[0027] Furthermore, in the polishing step B, the pressure applied by the upper polishing disc and the lower polishing disc to the glass is 10-30 g / cm 2 , polishing time is 0.5-2 hours.

[0028] Further, the method further includes performing a second group of polishing on the glass using a double-sided polishing machine, wherein the rotation speed of the lower polishing disc is 10-50 rpm, the load speed ratio of the upper polishing disc relative to the lower polishing disc is 50-80%, the load speed ratio of the inner gear ring relative to the lower polishing disc is 80-100%, and the load speed ratio of the outer gear ring relative to the lower polishing disc is 5-30%, wherein the lower polishing disc rotates in opposite directions to the upper polishing disc, the inner gear ring, and the outer gear ring, and the processing pressure is 10-30 g / cm 2 The polishing time is 0.1-1 hour. The second group can reduce the surface roughness of the glass to less than 1nm, and the surface shape is slightly low in the center and high around.

[0029] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the side structure of a double-sided polishing machine;

[0031] Figure 2 It is a schematic diagram of the top view of the double-sided polishing machine;

[0032] Figure 3 This is a front view of the glass after only polishing step A is performed on the glass in comparative example 1;

[0033] Figure 4 This is a front view of the glass after only polishing step B is performed on the glass in comparative example 2;

[0034] Figure 5 is a schematic diagram of the step flow;

[0035] Figure 6 This is a rendering of the front surface of the glass after polishing step A and polishing step B are performed on the glass in Example 1;

[0036] The reference numerals in the drawings are: 11 upper polishing plate, 12 lower polishing plate, 13 upper polishing pad, 14 lower polishing pad, 15 inner gear ring, 16 outer gear ring, 17 planetary wheel, 18 liquid guide hole, 19 glass, and 20 base. DETAILED DESCRIPTION

[0037] In order to solve the problem that the prior art cannot achieve a high level of flatness, the present invention analyzes the causes and explores the effects of each step and effect of the existing correction method. Through statistics and observation of the performance of the processed glass 19, it is found that the front of the glass 19 that has undergone double-sided chemical mechanical polishing finally presents a surface shape with a low center and high surroundings. In the prior art, technicians only considered reducing the thickness difference between the glasses and removing the excessively high parts of the glass surface during the parameter adjustment process, but did not consider the changes in the surface shape of the glass 19 during each polishing correction. At this time, even if the second or even more flatness polishing corrections are performed, without changing the trend of changing the front surface shape of the glass to a low center and high surroundings each time, the height difference between the center bottom and the four corners will not be reduced, and the flatness cannot be further improved. It may even cause the same surface shape to pile up, and the height difference between the middle bottom and the four corners will increase, that is, the flatness will deteriorate.

[0038] The present invention further analyzes the reasons for the height difference between the center and the surroundings after polishing. Figure 1In the double-sided polishing machine shown, the relative movement speed between the glass and the polishing pad is regulated by the inner gear ring 15, the outer gear ring 16, the upper polishing plate 11, and the lower polishing plate 12. On the one hand, the planetary wheel 17 is affected by the inner gear ring 15 and the outer gear ring 16 to revolve and rotate in the polishing machine, and the glass 19 also revolves and rotates in the planetary wheel 17. On the other hand, the upper polishing plate 11 and the lower polishing plate 12 rotate separately and rub against the surface of the glass 19. The superposition of these complex movement relationships leads to different relative grinding speeds of the polishing pad on different parts of the glass 19. The relative grinding speed of this part is fast, and the grinding amount in a certain period of time is large, so the surface of this part is low. Finally, the two sides of the processed glass 19 present a surface shape with a low center and high surroundings, or a high center and low surroundings. In summary, the present invention concludes that, for each polishing of the glass, the movement relationship of the four rotating components of the double-sided polishing machine - the upper polishing plate 11, the lower polishing plate 12, the inner gear ring 15, and the outer gear ring 16 determines the direction of the surface shape change of the polishing; and their actual rotation speed and processing pressure affect the overall polishing speed of the glass 19, and together with the adjustment of the processing time, ultimately affect the degree of change in the final surface shape of the glass 19 - either a surface shape with a low center and high surroundings, or a surface shape with a high center and low surroundings.

[0039] Such a final surface shape effect is an inevitable inherent additional effect of the double-sided polishing machine, which is determined by the polishing principle of the polishing machine. If you want to eliminate this inherent effect, you may need to perform a lot of analysis and make major changes to the polishing machine, and the analysis and modification costs are relatively high. In this regard, the present invention does not change the structure of the polishing machine and the corresponding polishing principle, but utilizes the result of the change in the glass surface shape that can be produced by each polishing, and alternately performs polishing correction step A and polishing correction step B on the front of the glass, wherein step A is "a polishing correction step that produces a surface shape effect with a low center and high surroundings after a single polishing of one side of the glass", and step B is "a polishing correction step that produces a surface shape effect with a high center and low surroundings after a single polishing of the front of the glass", and finally makes the center slightly lower, and improves the flatness of the front of the glass through the complementary surface shape effects of the two times.

[0040] Based on the above conception, the present invention further analyzes the motion relationship, pressure, time and other parameter relationships of each rotating component of the polishing machine to form the surface shapes of polishing step A and polishing step B, so as to achieve the complementarity of the surface shapes produced by the successive polishing steps and eliminate the technical problem of the flatness failing to meet the standard due to the accumulation of the same surface shape produced by each polishing.

[0041] The present invention uses a conventional double-sided polishing machine with a structure as described in the background technology for polishing. After testing and analyzing different types of polishing machines, the present invention concludes that compared with directly changing the rotation speed, controlling the motion relationship between the rotating components by controlling the load speed ratio can more universally achieve the surface effects of the above-mentioned polishing step A and polishing step B on various types of double-sided polishing machines. Among them, the load speed ratio is the ratio of the speed load between the two rotating components. The speed load is the ratio of the actual set speed of a rotating component to the maximum speed that the component can reach at this moment when the speed of the lower plate is a certain value. After experiments and analysis, the present invention concludes that when the load speed ratio of the upper polishing disc 11 relative to the lower polishing disc 12 is 50-80%, the load speed ratio of the inner gear ring 15 relative to the lower polishing disc 12 is 80-100%, and the load speed ratio of the outer gear ring 16 relative to the lower polishing disc 12 is 5-30%, and the lower polishing disc 12 rotates in the opposite direction to the other three, the front side of the glass 19 can achieve the effect of a single polishing with a low center and high surroundings, such as Figure 3 Based on this, the present invention further studies the relationship between the polishing correction speed, time and the final surface shape, and finds that the rotation speed of the lower polishing disc 12 is 10-50rpm, and the processing pressure is 20-50g / cm 2 , the polishing time is 2-4 hours, and finally the glass 19 with a low center and high surrounding surface can be obtained. That is, the above parameters can make the front of the glass 19 produce a low center and high surrounding surface after a single polishing. Relatively speaking, when the load speed ratio of the upper polishing disc 11 to the lower polishing disc 12 is 50-80%, the load speed ratio of the inner gear ring 15 to the lower polishing disc 12 is 80-100%, and the load speed ratio of the outer gear ring 16 to the lower polishing disc 12 is 20-50%, and the lower polishing disc 12 rotates in the opposite direction to the other three, the front of the glass 19 can achieve the effect of a high center and low surrounding surface after a single polishing, such as Figure 4 As shown. The polishing disc speed is further adjusted to 5-30 rpm and the processing pressure is 10-30 g / cm 2 , the polishing time is 0.5-2 hours, and the front side of the glass 19 with high center and low surrounding can be obtained. That is, after the front side of the glass 19 is polished once, the effect of high center and low surrounding can be produced.

[0042] Furthermore, since it is preferred for the front side of the glass 19 of the mask substrate to be slightly low in the center and high around the edges for downstream processes, the present invention adjusts parameters so that after the surface shapes are superimposed, the front side of the glass 19 can have a flatness of less than 0.5 μm or a slightly low in the center and high around edges. The present invention further analyzes and believes that the method of "first performing a single polishing to produce a polishing correction with a high center and low around edges, then performing a single polishing to produce a polishing correction with a low center and high around edges, and finally making the center slightly lower" removes more glass 19 substrate than "first performing a single polishing to produce a polishing correction with a low center and high around edges, then performing a single polishing to produce a polishing correction with a high center and low around edges, and finally making the center slightly lower". When the processing object is unqualified glass 19 that has been repaired again, its thickness is already within the standard range. If the removal amount is too much, the thickness of the glass 19 may be lower than the standard and scrapped, that is, the former has a narrower range of use.

[0043] Therefore, the present invention will take "polishing step A on the front side of the glass first, then polishing step B, and finally making the center slightly lower" as an example to introduce a specific embodiment. Figure 5 .

[0044] The solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] Example 1

[0046] This embodiment uses a double-sided polishing machine with the structure as described in the background technology to correct the flatness of the glass 19. Four planetary wheels 17 are placed correspondingly, and the upper polishing pad 13 and the lower polishing pad 14 are polyurethane rough polishing pads with a thickness of 2.5 mm. Before polishing, a polishing pad dresser is used to flatten the disk surface until the height difference between the highest and lowest points of the disk surface is within 30 μm. In this embodiment, the difference between the high and low points of the polishing pad surface after trimming is 15 μm. Select 8 glass 19 substrates to be reworked with a thickness difference of less than 50 μm, place them in the through holes of the planetary wheels 17, and place 2 pieces in each planetary wheel 17 to perform the first set of polishing. The specific polishing correction steps are as follows:

[0047] Polishing step A: Control parameters are: set the rotation speed of the lower polishing disc 12 to 35rpm, the load speed ratio of the upper polishing disc 11 to the lower polishing disc 12 to 50%, the load speed ratio of the inner gear ring 15 to the lower polishing disc 12 to 90%, and the load speed ratio of the outer gear ring 16 to the lower polishing disc 12 to 10%, wherein the rotation direction of the lower polishing disc 12 is opposite to the rotation direction of the other three. The polishing liquid uses a commercially available cerium oxide rough polishing liquid with a pressure of 40g / cm 2 , polishing for 2.5 hours.

[0048] Polishing step B: The control parameters are to set the rotation speed of the lower polishing disc 12 to 15rpm, the load speed ratio of the upper polishing disc 11 to the lower polishing disc 12 to 50%, the load speed ratio of the inner gear ring 15 to the lower polishing disc 12 to 92%, and the load speed ratio of the outer gear ring 16 to the lower polishing disc 12 to 22%, wherein the rotation direction of the lower polishing disc 12 is opposite to the rotation direction of the other three. The polishing liquid is a cerium oxide rough polishing liquid purchased on the market, and the pressure is 25g / cm 2 , polishing for 1.2 hours.

[0049] After polishing step A, the thickness difference of this batch of glass 19 is reduced to 10μm. After the second polishing step B, The flatness measuring machine detected that the front flatness of the glass 19 in this batch was 0.1-0.5μm, and the average flatness could reach 0.470μm. Figure 6 As shown, after two complementary surface effects, one of the glass sheets presents a very slight shape with a low center and high surroundings, and the TIR, i.e., flatness, of the front surface is 0.469 μm. The method of explaining the method is that the combination of polishing step A and polishing step B can make the front surface flatness of the glass 19 reach the requirement of less than 0.5 μm.

[0050] The maximum rotation speeds of the rotating components of the polishing machine used in this embodiment are: 20 rpm for the upper polishing disc 11, 50 rpm for the lower polishing disc 12, 30 rpm for the inner gear ring 15, and 20 rpm for the outer gear ring 16, but not limited thereto.

[0051] As comparative example 1, only polishing step A was performed on glass 19, and the surface shape and flatness of the front surface of glass 19 were measured: after polishing correction, the flatness of the front surface of glass 19 was measured to be 0.6-1.0 μm, and the average flatness was 0.850 μm. Figure 3 As shown, the TIR, i.e., flatness, of the front surface of one of the glass sheets is 0.857 μm, and the surface shape is low in the center and high around. This indicates that the parameters of polishing step A can make the front surface shape of glass 19 low in the center and high around, but polishing step A alone cannot make the flatness of the front surface of glass 19 reach less than 0.5 μm.

[0052] As comparative example 2, only polishing step B was performed on glass 19, and the surface shape and flatness of the front surface of glass 19 were measured: the flatness of the front surface of glass 19 was 0.6-1.0 μm, and the average flatness was 0.846 μm. Figure 4 As shown, the TIR, i.e., flatness, of the front side of one of the glass pieces is 0.875 μm, and the surface shape is high in the center and low around. This indicates that the parameters of polishing step A can make the front side of glass 19 high in the center and low around, but polishing step B alone cannot make the flatness of the front side of glass 19 reach less than 0.5 μm.

[0053] Example 2

[0054] Use the double-sided polishing machine as described in Example 1. The double-sided polishing machine is equipped with 5 planetary wheels 17. The upper polishing pad 13 and the lower polishing pad 14 are 3 mm thick polyurethane rough polishing pads. Use a polishing pad dresser to trim the polishing pad surface until the difference between the high and low points is 20 μm. Select 50 pieces of 6-inch glass 19 with a thickness difference of less than 50 μm, place them in the through holes of the planetary wheels 17, and place 10 pieces of glass 19 in each planetary wheel 17 to perform the first set of polishing. The specific steps are as follows:

[0055] Polishing step A: The control parameters are that the rotation speed of the lower polishing disc 12 is 30 rpm, the load speed ratio of the upper polishing disc 11 to the lower polishing disc 12 is 50%, the load speed ratio of the inner gear ring 15 to the lower polishing disc 12 is 85%, and the load speed ratio of the outer gear ring 16 to the lower polishing disc 12 is 5%, wherein the rotation direction of the lower polishing disc 12 is opposite to the rotation direction of the other three. The polishing liquid uses a commercially available cerium oxide rough polishing liquid with a pressure of 50 g / cm 2 , polishing time 2 hours.

[0056] Polishing step B: The control parameters are that the rotation speed of the lower polishing disc 12 is 10 rpm, the load speed ratio of the upper polishing disc 11 to the lower polishing disc 12 is 50%, the load speed ratio of the inner gear ring 15 to the lower polishing disc 12 is 90%, and the load speed ratio of the outer gear ring 16 to the lower polishing disc 12 is 20%, wherein the rotation direction of the lower polishing disc 12 is opposite to the rotation direction of the other three. The polishing liquid is a cerium oxide rough polishing liquid purchased on the market, and the pressure is 30 g / cm 2 , polish for 1 hour.

[0057] According to the flatness measuring machine, the flatness of the glass 19 substrate before processing is about 2-5 μm. After two polishings, the average TIR of the front surface of the glass 19 is measured to be 0.303 μm. The method of explaining the method is to combine the polishing steps A and S2 so that the flatness of the glass 19 can reach the requirement of less than 0.5 μm.

[0058] As comparative example 3, only polishing step A was performed on glass 19, and the surface shape and flatness of the front surface of glass 19 were measured: after polishing correction, the average TIR, i.e., the average flatness of the front surface of glass 19 was measured to be 1.029 μm. This indicates that the use of polishing step A alone cannot make the flatness of the front surface of glass 19 reach less than 0.5 μm.

[0059] Example 3

[0060] Use the double-sided polishing machine as described in Example 1, and place 4 planetary wheels 17 accordingly. The upper polishing pad 13 and the lower polishing pad 14 are flat polyurethane rough polishing pads with a thickness of 3 mm. Select 8 glass substrates 19 to be reworked with a thickness difference of less than 50 μm, place them in the through holes of the planetary wheels 17, and place 2 pieces in each planetary wheel 17 to perform the first set of polishing. The specific steps are as follows.

[0061] Polishing step A: The control parameters are that the rotation speed of the lower polishing disc 12 is 40rpm, the load speed ratio of the upper polishing disc 11 to the lower polishing disc 12 is 50%, the load speed ratio of the inner gear ring 15 to the lower polishing disc 12 is 95%, and the load speed ratio of the outer gear ring 16 to the lower polishing disc 12 is 15%, wherein the rotation direction of the lower polishing disc 12 is opposite to the rotation directions of the other three. The polishing liquid uses a commercially available cerium oxide rough polishing liquid with a pressure of 30g / cm 2 , polishing time 3 hours.

[0062] Polishing step B: The control parameters are that the rotation speed of the lower polishing disc 12 is 20 rpm, the load speed ratio of the upper polishing disc 11 to the lower polishing disc 12 is 50%, the load speed ratio of the inner gear ring 15 to the lower polishing disc 12 is 94%, and the load speed ratio of the outer gear ring 16 to the lower polishing disc 12 is 24%, wherein the rotation direction of the lower polishing disc 12 is opposite to the rotation directions of the other three. The polishing liquid is a cerium oxide rough polishing liquid purchased on the market, and the pressure is 20 g / cm 2 , polishing for 1.5 hours.

[0063] After completing two polishing corrections, the average TIR, that is, the average flatness, of the front surface of the glass 19 was measured to be 0.468 μm.

[0064] As comparative example 4, only polishing step A was performed on glass 19, and the surface shape and flatness of glass 19 were measured: after polishing correction, the average TIR, i.e., the average flatness, of the front surface of glass 19 was measured to be 1.209 μm. This indicates that the use of polishing step A alone cannot make the flatness of the front surface of glass 19 reach less than 0.5 μm.

[0065] Example 4

[0066] Considering that if the glass 19 substrate needs to be coated with a light-shielding film in the subsequent process, the glass 19 substrate needs to have a flatness of less than 0.5μm and a surface roughness of less than 1nm. Therefore, an additional step of fine polishing can be added to reduce the roughness, further remove shallow scratches, and improve the roughness, so that the glass 19 substrate can better meet the subsequent process requirements.

[0067] On the basis of Example 1, a second set of polishing is performed using the same double-sided polishing machine as that of Example 1, except that the upper polishing pad 13 and the lower polishing pad 14 are polyurethane polishing pads.

[0068] The second group of polishing: Use the double-sided polishing machine to perform fine polishing on the glass 19: the rotation speed of the lower polishing disc 12 is 35rpm, the load speed ratio of the upper polishing disc 11 to the lower polishing disc 12 is 50%, the load speed ratio of the inner gear ring 15 to the lower polishing disc 12 is 90%, and the load speed ratio of the outer gear ring 16 to the lower polishing disc 12 is 10%, wherein the rotation direction of the lower polishing disc 12 is opposite to the rotation direction of the other three. The polishing liquid uses a commercially available cerium oxide fine polishing liquid, and the pressure is 15g / cm 2 , polishing time 0.33 hours.

[0069] Finally, the average flatness of the front surface of glass 19 was measured to be 0.464μm, the surface roughness Ra<1nm, the surface shape was slightly low in the center and high around, and there was no obvious processing defect on the surface after cleaning. This shows that this step will not deteriorate the flatness of the front surface of glass 19 to a range exceeding the required range of 0.5μm, and the surface roughness of glass 19 can meet the requirements and meet the coating standards.

[0070] Example 5

[0071] On the basis of Example 2, a second set of polishing is performed using the same double-sided polishing machine as that of Example 2, except that the upper polishing pad 13 and the lower polishing pad 14 are polyurethane polishing pads.

[0072] The second group of polishing: Use the double-sided polishing machine to fine polish the glass 19, and the control parameters are: the rotation speed of the lower polishing disc 12 is 30rpm, the load speed ratio of the upper polishing disc 11 to the lower polishing disc 12 is 50%, the load speed ratio of the inner gear ring 15 to the lower polishing disc 12 is 85%, and the load speed ratio of the outer gear ring 16 to the lower polishing disc 12 is 5%, wherein the rotation direction of the lower polishing disc 12 is opposite to the rotation direction of the other three. The polishing liquid uses the cerium oxide fine polishing liquid purchased on the market, and the pressure is 15g / cm 2 , polishing time 0.5 hours.

[0073] Finally, the average flatness of the front surface of glass 19 was measured to be 0.370μm, the surface roughness Ra<1nm, and there were no obvious processing defects on the surface after cleaning. This shows that this step will not deteriorate the flatness of the front surface of glass 19 to a range exceeding the required range of 0.5μm, and the surface roughness of glass 19 can meet the requirements and meet the coating standards.

[0074] Compared with the prior art, the present invention has the following advantages:

[0075] 1. In the process of flatness polishing and correction of glass, the change of the front surface of the glass is controlled in a single time, which avoids the accumulation of a single surface shape. The flatness can reach below 0.5μm, and the effect is significantly improved.

[0076] 2. Use the strategy of first polishing the surface with a low center and high surroundings, and then polishing the surface with a high center and low surroundings, so that the removal amount in the flatness correction process is less. This method has a wider range of uses, especially for reworked glass, which can avoid being scrapped due to too thin thickness after processing.

[0077] 3. After the fine polishing step, the flatness of the glass will not deteriorate beyond the required range, and the surface roughness can meet the requirements and meet the coating standards.

[0078] 4. The method used in the present invention has a simple process and can quickly achieve the target flatness, thereby saving polishing liquid, reducing the loss of polishing pads, and thus reducing processing costs.

[0079] 5. When the target removal amount is slightly larger, the removal amount can be increased by polishing the alternating surfaces multiple times to avoid deep scratches caused by direct grinding.

[0080] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and the present invention is also intended to include these modifications and modifications.

Claims

1. A glass flatness correction method, characterized in that: Perform the first set of polishing on the glass, including: The front side of the glass is subjected to polishing step A and polishing step B alternately; wherein, The polishing step A is a polishing correction step for producing a surface shape with a low center and high surroundings after a single polishing of one side of the glass; The polishing step B is a polishing correction step for producing a high center and low surrounding surface effect after a single polishing of one side of the glass.

2. A glass flatness correction method as claimed in claim 1, characterized in that: Polishing step A is performed first, and then polishing step B is performed.

3. A glass flatness correction method as claimed in claim 2, characterized in that: While the polishing correction step is being performed on the front side of the glass, the back side of the glass is being polished.

4. A glass flatness correction method as claimed in claim 3, characterized in that: The polishing step A and the polishing step B both use a double-sided polishing machine, which includes an upper polishing disc, a lower polishing disc, an upper polishing pad, a lower polishing pad, an inner gear ring, an outer gear ring, and a plurality of planetary wheels; The upper polishing disc can rotate independently; The lower polishing plate can rotate independently; the lower polishing plate and the upper polishing plate are arranged parallel to each other with their axes facing each other; the upper polishing plate and the lower polishing plate can move away from or close to each other; The upper polishing pad and the lower polishing pad cover the surfaces opposite to the upper polishing plate and the lower polishing plate respectively; The inner gear ring is located between the upper polishing plate and the lower polishing plate, and its rotation center line coincides with the rotation center line of the lower polishing plate. It can rotate independently, and its diameter is smaller than that of the lower polishing plate. The outer ring is provided with teeth; The outer ring of the planetary gear has teeth and a through hole is provided inside; a number of planetary gears mesh with the outer ring teeth of the inner gear ring, and the planetary gears do not contact each other; The outer gear ring can rotate independently, and the rotation center line coincides with the rotation center line of the inner gear ring. The inner ring is provided with teeth, which mesh with the planetary gear. In the polishing step A, the load speed ratio of the upper polishing plate to the lower polishing plate is 50-80%, the load speed ratio of the inner gear ring to the lower polishing plate is 80-100%, and the load speed ratio of the outer gear ring to the lower polishing plate is 5-30%, wherein the lower polishing plate rotates in opposite directions to the upper polishing plate, the inner gear ring, and the outer gear ring.

5. A glass flatness correction method as claimed in claim 4, characterized in that: In the polishing step B, the load speed ratio of the upper polishing plate to the lower polishing plate is 50-80%, the load speed ratio of the inner gear ring to the lower polishing plate is 80-100%, and the load speed ratio of the outer gear ring to the lower polishing plate is 20-50%, wherein the lower polishing plate rotates in opposite directions to the upper polishing plate, the inner gear ring, and the outer gear ring.

6. A glass flatness correction method as claimed in claim 5, characterized in that: In the polishing step A, the rotation speed of the lower polishing disc is 10-50 rpm.

7. A glass flatness correction method as claimed in claim 5, characterized in that: The rotation speed of the lower polishing disc in the polishing step B is 5-30 rpm.

8. A glass flatness correction method as claimed in claim 6, characterized in that: In the polishing step A, the processing pressure is 20-50 g / cm 2 , polishing time is 2-4 hours.

9. A glass flatness correction method as claimed in claim 7, characterized in that: The processing pressure in the polishing step B is 10-30g / cm 2 , polishing time is 0.5-2 hours.

10. A glass flatness correction method as claimed in claim 5, characterized in that: Also includes: The glass is polished in the second group using a double-sided polishing machine, wherein the rotation speed of the lower polishing disc is 10-50rpm, the load speed ratio of the upper polishing disc to the lower polishing disc is 50-80%, the load speed ratio of the inner gear ring to the lower polishing disc is 80-100%, and the load speed ratio of the outer gear ring to the lower polishing disc is 5-30%, wherein the lower polishing disc rotates in the opposite direction to the upper polishing disc, the inner gear ring, and the outer gear ring, and the processing pressure is 10-30g / cm 2 , polishing time is 0.1-1 hour.

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