Abstract
Abstract. Lapping and polishing technology is an efficient processing method for wafer planarization processing. The structure of the fixed abrasive pad (FAP) is one of the most concerning issues in the research. The FAP structure affects the pressure distribution on the wafer surface, and the pressure distribution during processing has a significant influence on the wafer surface. Therefore, in this paper, a better pressure distribution is obtained by adjusting the angle of the spiral arrangement and the damping distribution of the damping layer of the FAP, thereby obtaining better processing quality. Based on the above theory, a new type of FAP, with coupling between the arrangement of the pellets and the damping regulation of the damping layer, was designed and optimized. The machining effects of different FAPs on the workpiece surface are compared in terms of material removal rate, material removal thickness, and surface roughness. The test results show that the workpiece material removal rate is higher than that of the traditional FAP when using the optimized FAP. The non-uniformity of the optimized FAP for that of material removal was 4.034 µm, which was lower than the traditional FAPs by 24.4 % and 17.6 %, respectively. The average surface roughness, Ra, of the optimized FAP is 0.21 µm, which is lower than 19.1 % and 12.5 % of the two traditional FAPs, respectively. Therefore, workpiece material removal and distribution are more uniform, and the surface quality of the workpiece is better when the optimized FAP processing is used. The test results prove that the optimized pellet arrangement and damping can achieve a better surface quality of the workpiece, which can meet the precision lapping process requirements for high-quality surfaces and large-scale production of brittle and hard materials such as sapphire.
Highlights
The most common substrate for gallium nitride (GaN) growth is sapphire
In order to quantitatively evaluate the pressure distribution results, an evaluation method for the pressure uniformity is introduced, which is similar to the trajectory uniformity evaluation method, and it grids the pressure data values of all nodes and evaluates the surface pressure distribution of the workpiece through the non-uniformity of pressure (NUP)
It can be observed that the material removal rate (MRR) of the workpiece after regulation is better than the MRR before regulation, and it is closer to the current level, so the scheme with a Mix 2 is selected for optimized fixed abrasive pad (FAP) production
Summary
The most common substrate for gallium nitride (GaN) growth is sapphire. Sapphire has stable chemical properties, and the quality of the processed device is better (Zhang et al, 2019; Fang et al, 2017, 2019; Sokol et al, 2013) As substrate geometries are still shrinking, lithographic accuracy requirements are becoming higher and higher. The use of FAPs can improve machining efficiency, but there is severe wear of the FAP and surface damage to the workpiece To overcome these problems, some scholars have realized that the precise lapping of brittle and hard materials, such as sapphire, from the perspective of regulating the surface pressure distribution of the workpiece during process is needed. This paper designs a new type of FAP, from the optimization of the surface structure and control of damping layer of the base pad, and performs experimental processing. It compares our model with the traditional FAP and tests the angles of MRR and workpiece surface quality
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