Papers by Author: Fei Yan Lou

Abstract: A three-dimensional hydrodynamic lubrication model based on lubrication theory is developed which accounts for pad roughness and slurry flow. The distribution of the slurry film thickness and pressure between the pad and the wafer are predicted using the model. The effects of the pad roughness, the polishing applied load and rotation speed on slurry film thickness and tilt angle are discussed. At last, a CMP experiment is carried out. It is found that the results are proved the three-dimensional model considering pad roughness agrees well with our experimental data. The results improve the previous models so that the CMP process can be better simulated using the model. Furthermore, they are useful in the processing of CMP and the design of the pad roughness.

Abstract: Friction drives offer certain advantages over gears. In particular, they generally run more quietly and are easier to manufacture than geared units. The friction drives used in revolving stages call for a large driving radius in order to reduce friction force. In traditional friction drives, the two friction wheels (driving and driven) must be highly and precisely circular. This makes the manufacture of the driven wheel difficult and uneconomical. In this paper, a floating and self-actuating friction drive device was developed with the use of a swinging gearbox. In this device, the driving wheel is floatable, so the driven wheel is permitted to have certain deviation of roundness in the make and certain eccentricity in the installation. This avoids the difficulties in making and installing the driven wheel. This is a strong point in the applications of the revolving stage and other large-scale revolving devices. Meanwhile, this configuration can adaptively generate a normal torque on demand by using a swinging gearbox. This relieves the friction wheels of a continuous and high-stress load, thus prolonging their workability. Also, this paper described the working principles of this new friction drive device and presented a force analysis.

Abstract: A three-dimensional hydrodynamic lubrication model for chemical-mechanical polishing is presented based on the Reynolds equation and Reynolds boundary condition. By solving the Reynolds equation, the slurry film pressure distribution has been obtained. The effects of minimum film thickness and the wafer tile angle on the film pressure are analyzed, and the influence of the polishing applied load and rotation speed on slurry film thickness and tilt angle are discussed. At last, by experiment, it is found that the simulation results are similar to experiment results which film thickness is increasing with the increasing of rotation speed, decreasing of the applied load. It is proved that the simulation is reliable.

Abstract: 9Cr18 is a type of martensite stainless steel. It has high hardness, chemical stability, fine anticorrosion, wearable and quench stability. It has been used in different areas with high-anticorrosion and high polishing surface as mirror. So it requires for the high level surface quality after lapping and polishing. In this paper, the surface quality (surface roughness and flatness) of 9Cr18 is discussed with lapping parameters which include velocity, load and time distribution of two lapping steps(rough lapping and Ultra-precision lapping). In order to optimize those parameters, an optimization experiment for lapping 9Cr18 with Al2O3 was designed by Taguchi method. Finally, the optimum condition of each factor can be determined that speed: 80rpm, load:3.0kPa, and time distribution: rough lapping time=15min, Ultra-precision lapping time＝45min are the optimum conditions for both Ra and Wt.

Abstract: The high precision balls are requested in national defense, astronautics and high-tech commercial domain urgently. Conventional precision machining methods are sensitive to uniformity of abrasives and machining environment. After precision machining, there are easily to produce thick damaged layer on the ball surface because of machining stress and chemical conversion. On the basis of the floating polishing mechanism, a new scatheless ultra-precision polishing method of ball surface can solve the problems of abrasives uniformity effectively and damaged layer. In order to ensure that the new polishing method polishes ball surface equally, the appropriate angular velocities of the ball should be selected. This paper sets up the mathematical model about the motion of ball. By analyzing and simulating the relationship of the angular velocities, the best processing parameters are acquired.

Abstract: The ultra-precision lapping processes to obtain the damage-free surfaces at Å level surface roughness of Potassium titanyl phosphate (KTiOPO4, KTP) crystal is studied in this paper. The influence of the lapping parameters on the stoke removal rate and surface roughness and material removal mechanism in the process of ultra-precision lapping process is discussed, and the evolution of the lapped surface is also observed with electric telescope. A super-smooth surface of quartz crystal with roughness Ra 0.8667 Å has been obtained by adopting the fine SiO2 abrasive powders and the elastic polyurethane pad in this study.

Abstract: 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.

Abstract: A novel lapping mode is developed on the base of present eccentric v-grooves lapping mode for precise balls. The kinematics analysis shows that the ball spin axis can wiggle up to 180° under the developed mode, so the lapping trace will be dispersed onto the whole surface of the ball. The effect of offsetting and groove radius on the lapping uniformity in the developed eccentric v-grooves, the present eccentric v-grooves and the traditional v-grooves lapping mode are compared, and the advantage of the developed mode is that the impact offsetting is less while the groove radius has no impact.

Abstract: Potassium Titanium Oxide Phosphate (KTP) is a new nonlinear frequency-conversion crystal. It has chemical stability, high nonlinear coefficient, high damage threshold, easily-polished surface, and a broad transparency range. It is be used in solid green laser with medium and low power widely. The requirement for surface roughness is less than 1nm.In this paper, the removal rate and surface roughness are discussed with different velocity, pressure and size of abrasive powder. In order to satisfy the requirement, new polishing techniques with ultra-precision plane polishing machine (Nanopoli-100), and fine AL2O3, SiO2 powders are proposed in this study. The final surface roughness of the KTP is less than 1nm.The machining process and characteristics are also indicated.

Abstract: STAVAX ESR（S-136）is a type of high stainless steel, used in precision mould widely . It has fine anticorrosion, polishing-alike, wearable，good process capacity and quench stability. To obtain the smooth surface of STAVAX ESR, the material removal mechanism in the paper is discussed. The experiment is processed on the ultra-precision plane polishing machine (Nanopoli-100). The experiment processes are as follows. Rough lapping and Ultra-precision lapping: the material of lapping pads is cast iron. #1000Al203 (10wt%) abrasive powders are used in rough lapping. Finally, surface roughness is 62nm. In ultra-precision lapping, abrasive powders are for #4000Al203（10wt%）. Removal rate is 1nm with linear velocity 8.6m/min, pressure 3.65MPa. After 4000 rounds, surface roughness is 35nm.Ultra precision polishing: The super smooth surfaces of STAVAX ESR（S-136）with 5nm roughness have been obtained by adopting SiO2(> 30wt%) slurry and soft tin polisher in the experiment.