Zhao Zhong Zhou

Study on Pad Conditioning Parameters in Silicon Wafer CMP Process

Polishing pad plays a key role in determining polish rate and planarity of a chemical mechanical planarization (CMP). The properties of the pad would deteriorate during polishing because of pad surface grazing, which results in reduced removal rates and poorer planarity of wafer surface. Pad conditioning and its influence on pad surface structure and CMP process is introduced and discussed in this paper. The study shows that the surface structure can be regenerated by breaking up the glazed areas with conditioner, MRR(Material Removal Rate) can be maintained at high level with proper pad conditioning, and UN(Non-uniformity)can also improved. Orthogonal experiments design is employed in this study to determine the best conditioning parameters.

Research and Simulation on the Wear Uniformity of Lapping Plate

Lapping plate wear is of great influence on shape precision of workpiece. Investigation on the wear uniformity of uncertain eccentricity plane lapping was carried out in this research. The relative velocity function of the plate to the workpiece is obtained through kinematic analyses in the mode of uncertain eccentricity plane lapping, and material removal rate (MRR) function and wear uniformity function were deduced based on Preston equation. Effects of the ratio and eccentricities on the wear uniformity are discussed in detail through MATLAB simulation. Theoretical analysis and simulation results show that the ratio k1 of workpiece revolution speed to lapping plate is the key to decide whether the lapping plate is lapped uniformly. Theoretically, when k1<0, the greater |k1| is, the better the lapped uniformly of lapping plate can be. The ratio k2 of workpiece rotation speed to lapping plate has great influence on the lapped uniformly when k1 approximate 1, and k2 has little influence on the lapped uniformly when k1<0 or k1>1, Besides, a bit bigger eccentricity e1 is propitious to the lapping uniformly of the lapping plate, and bigger eccentricity e2 are also helpful to lapping uniformly of the lapping plate. And the conclusion could be extended to single-side plane lapping and double-side plane lapping process.

Study on Dual-Plane Ball Polishing Method for Finishing Ceramics Ball

This paper represents a dual-plane polishing method for ceramics ball. Compared with traditional ball polishing method, its upper and lower plate are all flat and easy to use soft pad to polish, so it can largely reduce the surface mechanical damage and obtain high quality processing surface. This paper analyzes surface polishing trajectory by calculation and simulation to test the polishing trajectory uniformity. A mathematics model of polishing process is established to disintegrate the process of a balls movement. Experiment is operated in dual-plane planetary polishing machine. The result shows that perfect polishing surface and spherical error can be obtained under the proper process parameters, the surface roughness achieves 4nm and the spherical error can reach 0.217μm.

Application of Taguchi Method for Optimization of Finishing Conditions in SUS440 Stainless Steel Substrate

This paper focuses on the application of Taguchi method for optimization of SUS440 stainless steel polishing process parameters to obtain the best finish. An optimization experiment for polishing stainless steel with SiO2 was designed by Taguchi method. Surface roughness Ra is considered as criteria for optimization. Influence of parameters involving load, speed, and slurry concentration for a given workmaterial with given abrasive (material and size) are discussed, and the optimum polishing conditions are figured out. Compared with single parameter experimental results, it illustrates that the experiment design based on Taguchi method can successfully applied to determine the optimum processing conditions for SUS440 stainless steel polishing process.

Modeling and Simulation of Lapping Processes Based on Grain Size Sensitivity Model

It is of high importance to avoid scratches in lapping process. A Grain Size Sensitivity (GSS) model is put forward in this paper. The GSS is a relative parameter which defines the relative change of the depth of cutting, influenced by the change of the size of grain powders, by which it is possible to evaluate quantificationally the capability of lapping machines in avoiding scratches. It is useful for designing and using lapping machines. The simulating of lapping processes based on GSS model is carried out. The transferring of error is also discussed and a new structure of lapping plate with spring cells developed by the authors is introduced.

Visualized Characterization of Slurry during CMP Based on LIF

Chemical mechanical polishing has emerged recently as an indispensable processing technique in large scale integration. In chemical and mechanical polishing process, chemical and mechanical principle is the vital factor in the removal process. Little is known about what is occurring beneath a wafer during Chemical Mechanical Polishing (CMP) processes. The paper provides a LIF technology to visualize the fluid flow between the wafer and pad. In this paper, the experiment setup is built. And then, the images of fluorescence intensity excited by LIF have been obtained from CCD. Finally, the relationships between pH, temperature, laser power, film thickness and fluorescence intensity excited by LIF (Laser induced Fluorescence) are studied.

Study on Ultra-Precise Machining of CLBO Crystal

Cesium Lithium Borate (CsLiB6O10 or CLBO) is the most effective non-linear crystal which generates ultraviolet harmonics of the Nd:YAG fundamental laser wavelength. In order to enhance the damage threshold, low CLBO surface roughness, by ultra-precision machining, is needed. Because the CLBO crystal has easy hydroscopic reaction and micro scratches in machining, ultra-precise machining of the CLBO crystal is a difficult technical problem. In this paper, the new lapping slurry and polishing slurry are introduced. And the deliquescence degree of CLBO is fallen to lowest. A new working technology is also adopted. After rough polishing, the concentration of ultra-precision polishing slurry is increased properly. So does the ultra-precision polishing speed, and the wiping speed is faster than the deliquescence speed. The CLBO crystal surface roughness can achieve 1nm and keep the surface quality well.

Research on Wear Mechanism of Self-Sharpening Fine Super-Hard Abrasive Tool

To achieve the components of the highest quality in terms of shape, dimension, surface integrity and high efficiency in the course of processing difficult-to-cut material, the concept of self-sharpening fine super-hard abrasive tool as machining tool is put forward, this method not only improves the dressing performance of the abrasive tool, but also ensures the accuracy and durability of the abrasive tool, self-sharpening fine super-hard abrasive tool lapping technology is developed by using Zn as abrasive fillers and using FeCl3 solution as lapping liquid, the wear form of the self-sharpening fine super-hard abrasive tool and the influence of abrasive wear on the material removal form is studied, research shows that the wear of the self-sharpening fine super-hard abrasive tool is mainly in breakage wear, which has a good self-sharpening performance, and the material removal form is mainly in two-body material removal mode., which means this method has good holding force of abrasives.

Analysis on Wear of Self-Sharpening Fine Super-Hard Abrasive Tool

In order to improve the efficiency of ultra-precision processing, the self-sharpening fine super-hard abrasive tool is presented to reduce or eliminate the surface and subsurface defects and improve the process efficiency. In the study of efficient experimental research of self-sharpening fine super-hard abrasive tool, base on single factor experiments such as additives composition, grinding speed, grinding pressure and processing liquid. The results showed that the wear rate of the self-sharpening fine super-hard abrasive tool can reach appropriate rate when the additive concentration 30wt%, grinding pressure 45N, grinding speed 60rpm and processing liquid 1wt%.

Study on Roundness Error Correction for the Ceramic Ball in Rotated Dual-Plates Lapping Process

The correction process of balls roundness error during lapping is discussed qualitatively. Dynamic analysis for rotated dual-plates lapping mode of ceramic balls is performed, under the assumption of a fluid loading system. The effect of the damping of the loading system on the correction of balls roundness error is discussed. And the result shows large damp causes an increase of magnification of load, and improves the correction of roundness error of balls.