Clamp for preventing wafer edge collapse in polishing process
By setting a circular groove on the back of the polishing fixture and adjusting the weight of the counterweight block, the stress distribution of the wafer is changed, and the edge collapse problem during the wafer polishing process is solved and the flatness of the wafer surface is improved.
Patent Information
- Application Number
- CN202422261956.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-14
- Publication Date
- 2025-07-22
- Estimated Expiration
- 2034-09-14
AI Technical Summary
In the existing polishing technology, edge collapse often occurs during the polishing process, and the shape changes of existing polishing discs and adjustment of polishing process parameters are difficult to effectively solve, and some fixtures have complex designs or no significant improvement effect.
A fixture including a polishing fixture and a counterweight is designed to change the pressure distribution of the wafer center and edge by providing a circular groove on the back of the fixture and adjusting the weight of the counterweight to prevent the wafer from collapse.
It realizes simple operation and effectively prevents edge collapse problems during the polishing process, and improves the surface flatness of the wafer.
Smart Images
Figure CN223130383U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of wafer polishing, and particularly relates to a fixture for preventing the edge collapse of a wafer during the polishing process. Background Art
[0002] The polishing technology is a key technology for semiconductor wafers to obtain low surface roughness and surface planarization. However, during the polishing process, due to factors such as the force condition, movement condition of the wafer, and the flow rate, distribution, and ratio of the polishing liquid, the wafer often shows an edge collapse phenomenon after the polishing process, that is, the removal thickness at the wafer edge is greater than the removal thickness at the center, thereby reducing the surface flatness of the wafer and affecting the subsequent processes.
[0003] At present, many patents and articles have reported on how to alleviate the edge collapse problem during wafer polishing, mainly focusing on the changes in the shape of the polishing plate, the trimming of the polishing pad shape, the adjustment of polishing process parameters, and the design of polishing fixtures. Changing or trimming the shapes of the polishing plate and the polishing pad is relatively difficult to achieve. Especially for the trimming of the polishing plate, it has a large processing difficulty, high cost, and also requires customizing corresponding polishing pads. Although the adjustment of polishing process parameters is easy to achieve, the effect of improving edge collapse is not significant. Therefore, among the means to solve the edge collapse problem, more are mainly focused on the design of polishing fixtures. However, among these reported polishing fixtures that we know, either the design is complex and the processing difficulty is large, or the improvement of the edge collapse phenomenon during use is not significant, and they cannot help us solve the edge collapse problem in the existing polishing process. Summary of the Utility Model
[0004] In order to solve the edge collapse problem that occurs in the existing polishing process, the utility model provides a fixture that can effectively prevent the edge collapse of a wafer during the polishing process.
[0005] The fixture provided by the utility model includes a polishing fixture and a counterweight. A wafer placement groove and a diversion groove are formed in the middle position of the front surface of the polishing fixture. The wafer placement groove is used for placing the wafer, and the diversion groove is used for diverting the polishing liquid. A circular groove is formed in the center position of the back surface of the polishing fixture, and the depth of the circular groove is greater than the depth of the wafer placement groove. The counterweight includes a cylindrical counterweight and an annular counterweight. The annular counterweight is sleeved on the cylindrical counterweight, and either end of the cylindrical counterweight sleeved with the annular counterweight can be movably placed in the circular groove. The size of the circular groove is designed according to the calculated edge collapse size of the wafer, and the pressure distribution applied to the center and edge of the wafer is adjusted by adjusting the weight of the cylindrical counterweight and / or the annular counterweight, thereby changing the force condition of the wafer and finally solving the problem of edge collapse of the wafer during the polishing process.
[0006] In the above fixture, the polishing fixture is preferably made of polytetrafluoroethylene material, and the counterweight is made of stainless steel material.
[0007] In the above-mentioned fixture, the length and width of the wafer placement groove are equal to the length and width of the wafer, and the groove depth is less than the thickness of the wafer.
[0008] In the above-mentioned fixture, the groove depth of the flow guide groove is the same as that of the wafer placement groove, the groove depth of the circular groove is greater than that of the wafer placement groove, and the diameter of the circular groove is determined according to the size of the edge collapse.
[0009] In the above-mentioned fixture, the diameter of the cylindrical counterweight is the same as the diameter of the circular groove, the inner diameter of the annular counterweight is the same as the diameter of the cylindrical counterweight, and the outer diameter of the annular counterweight is the same as the diameter of the polishing fixture.
[0010] In the above-mentioned fixture, the mass specifications of the cylindrical counterweight and the annular counterweight can be designed in multiple specifications according to needs.
[0011] The design principle of the fixture of the present utility model is: the size of the circular groove is designed according to the calculated size of the edge collapse of the wafer, and then the pressure distribution applied to the center and edge of the wafer is adjusted by adjusting the weights of the cylindrical counterweight and the annular counterweight, so as to change the stress condition of the wafer and achieve the purpose of preventing the wafer from collapsing.
[0012] The present utility model has the advantages of simple production, simple operation and effectively solving the problem of edge collapse. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 is a schematic diagram of the overall structure of the fixture of the present utility model.
[0014] Figure 2 is a schematic diagram of the front structure of the polishing fixture.
[0015] Figure 3 is a schematic diagram of the back structure of the polishing fixture and different stress conditions.
[0016] Figure 4 is Figure 2 a schematic diagram of the sectional structure of the A-A plane of the polishing fixture in
[0017] Figure 5 is a schematic diagram of the overall structure of the cylindrical and annular counterweights.
[0018] In the figure: 1 - polishing fixture; 2 - cylindrical counterweight; 3 - annular counterweight; 4 - wafer placement groove; 5 - circular groove; 6 - flow guide groove. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0019] To make the technical problems to be solved and the design advantages of the present utility model more clearly understood, the present utility model will be further described in detail below with reference to the accompanying drawings.
[0020] As Figures 1-5As shown in the figure, the embodiment of the utility model includes a polishing fixture 1, a cylindrical counterweight 2 and an annular counterweight 3. There is a wafer placement groove 4 in the middle of the front surface of the polishing fixture 1, and a diversion groove 6 at the edge position. The wafer placement groove 4 is used for placing wafers. The length and width of the wafer placement groove 4 are equal to the length and width of the wafer, and the groove depth is less than the thickness of the wafer. The diversion groove 6 is connected to the wafer placement groove 4 and is used for draining the polishing liquid. The groove depth is the same as that of the wafer placement groove 4, and the groove width can be set according to requirements. In the embodiment of the utility model, the groove width is 5 mm.
[0021] There is a circular groove 5 at the center of the back surface of the polishing fixture 1. The groove diameter of the circular groove 5 is determined according to the size of the edge collapse. In the embodiment of the utility model, the groove depth of the circular groove 5 is 5 mm, which is greater than the groove depth of the wafer placement groove, and the diameter is 30 mm, which is less than the width of the wafer placement groove.
[0022] The diameter of the cylindrical counterweight 2 is the same as the diameter of the circular groove 5. The cylindrical counterweight 2 can be movably placed in the circular groove 5 to form a nested structure. The inner diameter of the annular counterweight 3 is the same as the diameter of the cylindrical counterweight 2. The annular counterweight 3 can be flexibly nested on the cylindrical counterweight 2, and the outer diameter of the annular counterweight 3 is the same as the diameter of the polishing fixture 1. In the embodiment of the utility model, the cylindrical counterweight 2 has three mass specifications, which are 100 g, 300 g and 500 g respectively, and the diameters are all 30 mm. The annular counterweight 3 has three mass specifications, which are 100 g, 200 g and 500 g respectively, and the outer diameters are all 90 mm.
[0023] After the counterweights are configured as a whole, they are placed upright in the circular groove 5. At this time, the height of the cylindrical counterweight 2 above the back surface of the polishing fixture 1 should not be greater than 6 cm.
[0024] The use process of the utility model includes:
[0025] (1) During polishing, drop a few drops of water into the wafer placement groove 4, place the wafer to be polished in the wafer placement groove 4 of the polishing fixture 1, and gently shake it to ensure that the wafer adheres firmly to the wafer placement groove 4;
[0026] (2) Then, place the polishing fixture 1 upside down on the polishing disc;
[0027] (3) Then, place the cylindrical counterweight 2 into the circular groove 5 on the back of the polishing fixture 1, and place the annular counterweight 3 in the remaining positions on the back of the polishing fixture 1 by nesting it with the cylindrical counterweight 2. In this embodiment, since the wafer size is relatively large, in order to improve the polishing efficiency, a cylindrical counterweight 2 with a specification of 500 g is placed in the circular groove 5. First, an annular counterweight 3 with a specification of 200 g is sleeved on the cylindrical counterweight 2 and pressed on the back of the polishing fixture 1, and the thickness is measured after polishing for a certain period of time. The test results show that the combination of the cylindrical counterweight with a specification of 500 g and the annular counterweight with a specification of 200 g cannot solve the problem of edge collapse. Then, still place the cylindrical counterweight 2 with a specification of 500 g in the circular groove 5, and use one 100 g and one 200 g annular counterweight 3 to sleeve on the cylindrical counterweight 2 for polishing. The test results show that this combination also cannot solve the problem of edge collapse. After that, increase the number of annular counterweights in sequence for polishing until the combination of the cylindrical counterweight 2 with a specification of 500 g and a certain number of annular counterweights 3 can effectively solve the problem of edge collapse. Adjust the weights of the cylindrical counterweight and the annular counterweight according to the edge collapse situation to adjust the pressure distribution applied to the center and edge of the wafer, and change the force distribution of the wafer.
[0028] In the embodiment of the present utility model, the finally selected cylindrical counterweight 2 has a specification of 500 g, and the annular counterweights 3 have specifications of 200 g and 500 g. After polishing under this condition, the edge of the wafer no longer collapses, and the problem of edge collapse in the existing polishing process is successfully solved. This fixture is simple to manufacture, convenient and effective to operate, and can be completed by those skilled in the art based on common general knowledge.
[0029] The above-described embodiments are the preferred embodiments of the present utility model, but should not be construed as limiting the scope of the present utility model. It should be noted that for those skilled in the art, without departing from the technical principle described in the present utility model, several improvements and modifications can still be made, and these improvements and modifications all fall within the protection scope of the present utility model.
Claims
1. A fixture for preventing the edge collapse of a wafer during polishing, characterized in that: The fixture includes a polishing fixture (1) and a counterweight. A wafer placement groove (4) and a diversion groove (6) are provided on the front surface of the polishing fixture (1), and a circular groove (5) is provided at the center position of its back surface; the counterweight includes a cylindrical counterweight (2) and an annular counterweight (3). After the annular counterweight (3) is sleeved on the cylindrical counterweight (2), either end thereof can be movably placed in the circular groove (5); The diversion groove (6) is communicated with the wafer placement groove (4) for draining the polishing liquid; The size of the circular groove (5) is determined according to the calculated edge collapse size of the wafer; by adjusting the weights of the cylindrical counterweight (2) and / or the annular counterweight (3), the pressure distribution applied to the center and edge of the wafer is adjusted to prevent the edge collapse of the wafer during polishing.
2. The fixture for preventing the edge collapse of a wafer during polishing according to claim 1, characterized in that: The diameter of the cylindrical counterweight (2) is the same as the diameter of the circular groove (5).
3. The fixture for preventing the edge collapse of a wafer during polishing according to claim 1, characterized in that: The inner diameter of the annular counterweight (3) is the same as the diameter of the cylindrical counterweight (2); The outer diameter of the annular counterweight (3) is the same as the diameter of the polishing fixture (1).
4. The fixture for preventing the edge collapse of a wafer during polishing according to claim 1, characterized in that: The annular counterweight (3) includes several pieces with the same inner and outer diameters, and several pieces of the annular counterweight (3) can be movably sleeved on the cylindrical counterweight (2) in sequence.
5. The fixture for preventing the edge collapse of a wafer during polishing according to claim 1, characterized in that: The groove depth of the diversion groove (6) is the same as the groove depth of the wafer placement groove (4).
6. The fixture for preventing the edge collapse of a wafer during polishing according to claim 1, characterized in that: The length and width of the wafer placement groove (4) are equal to the length and width of the wafer, and the groove depth is less than the thickness of the wafer.
7. The fixture for preventing the edge collapse of a wafer during polishing according to any one of claims 1-6, characterized in that: The counterweight is selected from one or more of metal materials, alloy materials, ceramic materials, and organic materials; The fixture is made of an organic material with a low elastic modulus.
8. The fixture for preventing the edge collapse of a wafer during polishing according to any one of claims 1-6, characterized in that: The groove width of the diversion groove (6) is 5 mm.
9. The fixture for preventing the edge collapse of a wafer during polishing according to any one of claims 1-6, characterized in that: The cylindrical counterweight (2) has three mass specifications, which are 100 g, 300 g, and 500 g respectively, and the diameters are all 30 mm; The annular counterweight (3) has three mass specifications, which are 100 g, 200 g, and 500 g respectively. Each mass specification has several pieces, and the outer diameters are all 90 mm.
10. The fixture for preventing the edge collapse of a wafer during polishing according to claim 9, characterized in that: When the overall counterweight is placed upright in the circular groove (5), the height of the cylindrical counterweight (2) above the back of the polishing fixture (1) is not more than 6 cm.