Kang Renke

Material removal rate of 6H-SiC crystal substrate CMP using an alumina (Al2O3) abrasive

The influences of the polishing slurry composition, such as the pH value, the abrasive size and its concentration, the dispersant and the oxidants, the rotational velocity of the polishing platen and the carrier and the polishing pressure, on the material removal rate of SiC crystal substrate (0001) Si and a (0001) C surface have been studied based on the alumina abrasive in chemical mechanical polishing (CMP). The results proposed by our research here will provide a reference for developing the slurry, optimizing the process parameters, and investigating the material removal mechanism in the CMP of SiC crystal substrate.

Microstructure studies of the grinding damage in monocrystalline silicon wafers

Abstract The depth and nature of the subsurface damage in a silicon wafer will limit the performance of IC components. Damage microstructures of the silicon wafers ground by the #325, #600, and #2000 grinding wheels was analyzed. The results show that many microcracks, fractures, and dislocation rosettes appear in the surface and subsurface of the wafer ground by the #325 grinding wheel. No obvious microstructure change exists. The amorphous layer with a thickness of about 100 nm, microcracks, high density dislocations, and polycrystalline silicon are observed in the subsurface of the wafer ground by the #600 grinding wheel. For the wafer ground by the #2000 grinding wheel, an amorphous layer of about 30 nm thickness, a polycrystalline silicon layer, a few dislocations, and an elastic deformation layer exist. In general, with the decrease in grit size, the material removal mode changes from micro-fracture mode to ductile mode gradually.

An automated wafer-handling system based on the integrated circuit equipments

Based on the integrated circuit equipments, this paper respectively introduces the constitute and function of the automated wafer-handling system, the design and principle of the wafer-handling robot, wafer positioning system, and end-effector calibration system. This paper studies the up-down and rotation component, radial linear stretch component, end rotation component and the principle of work. The kinematics analysis of the linear mechanism of radial stretch component is presented

A signal processing method for the friction-based endpoint detection system of a CMP process

A signal processing method for the friction-based endpoint detection system of a chemical mechanical polishing (CMP) process is presented. The signal process method uses the wavelet threshold denoising method to reduce the noise contained in the measured original signal, extracts the Kalman filter innovation from the denoised signal as the feature signal, and judges the CMP endpoint based on the feature of the Kalman filter innovation sequence during the CMP process. Applying the signal processing method, the endpoint detection experiments of the Cu CMP process were carried out. The results show that the signal processing method can judge the endpoint of the Cu CMP process.

Material removal rate in chemical-mechanical polishing of wafers based on particle trajectories

Distribution forms of abrasives in the chemical mechanical polishing (CMP) process are analyzed based on experimental results. Then the relationships between the wafer, the abrasive and the polishing pad are analyzed based on kinematics and contact mechanics. According to the track length of abrasives on the wafer surface, the relationships between the material removal rate and the polishing velocity are obtained. The analysis results are in accord with the experimental results. The conclusion provides a theoretical guide for further understanding the material removal mechanism of wafers in CMP.

Research on microwave and millimeter-wave IPD measurement system for radome

Radome is of great importance in all kinds of aircraft, such as carrier rocket, airship, missile and controllable satellite. Insert phase delay (IPD) is one of the vital electrical parameters influencing electric properties of the radome. It is essential to measure the IPD in manufacturing of the radome. In this paper, the microwave and millimeter-wave technology is introduced into the IPD measurement for the radome. The basic theory of the IPD measurement using microwave and millimeter-wave is analyzed, the measurement system scheme with the vector network analyzer as the kernel part is developed, and the signal detection of microwave and millimeter-wave in the system is discussed. This system has high precision and powerful flexibility, and can satisfy the requirement of the IPD precise measurement for the radome.

Vapor‐melt Ratio in Laser Fine Cutting of Slot Arrays

In order to improve cut quality for slot arrays, a new method of laser fine cutting under the consideration of the ratio of vapor to melt is presented. Laser cutting of 6063 aluminum alloy sheet, 0.5 mm in thickness, was carried out on a JK701H Nd:YAG pulse laser cutting system. The effects of vapor‐melt ratio on kerf width, surface roughness and recast layer were studied which relate cutting qualities. Observation on the cut samples with different vapor‐melt ratios (0.687, 1.574, 3.601 varied with laser power increasing, and 1.535, 3.601, 7.661 with decreasing of beam cutting speed) shows that high vapor‐melt ratio improves laser cut quality clearly. Kerf width 0.2 mm of smooth area on kerf top area and thickness 2.03 μm of recast layer are obtained. No dross was found on the kerf bottom and the percentage of the smooth area is up to 40% out of whole kerf side. The research on vapor‐melt ratio provides a deeper understanding of laser cutting and improves laser cut quality effectively.

Surface shape control of the workpiece in a double-spindle triple-workstation wafer grinder

Double-spindle triple-workstation (DSTW) ultra precision grinders are mainly used in production lines for manufacturing and back thinning large diameter (≥ 300 mm) silicon wafers for integrated circuits. It is important, but insufficiently studied, to control the wafer shape ground on a DSTW grinder by adjusting the inclination angles of the spindles and work tables. In this paper, the requirements of the inclination angle adjustment of the grinding spindles and work tables in DSTW wafer grinders are analyzed. A reasonable configuration of the grinding spindles and work tables in DSTW wafer grinders are proposed. Based on the proposed configuration, an adjustment method of the inclination angle of grinding spindles and work tables for DSTW wafer grinders is put forward. The mathematical models of wafer shape with the adjustment amount of inclination angles for both fine and rough grinding spindles are derived. The proposed grinder configuration and adjustment method will provide helpful instruction for DSTW wafer grinder design.

Model analysis and experimental investigation of the friction torque during the CMP process

A model for calculating friction torque during the chemical mechanical polishing (CMP) process is presented, and the friction force and torque detection experiments during the CMP process are carried out to verify the model. The results show that the model can well describe the feature of friction torque during CMP processing. The research results provide a theoretical foundation for the CMP endpoint detection method based on the change of the torque of the polishing head rotational spindle.

Effects of the reciprocating parameters of the carrier on material removal rate and non-uniformity in CMP

Based on the Preston equation, the mathematical model of the material removal rate (MRR), aiming at a line-orbit chemical mechanical polisher, is established. The MRR and the material removal non-uniformity (MRNU) are numerically calculated by MATLAB, and the effects of the reciprocating parameters on the MRR and the MRNU are discussed. It is shown that the smaller the inclination angle and the larger the amplitude, the higher the MRR and the lower the MRNU. The reciprocating speed of the carrier plays a minor role to improve the MRR and decrease the MRNU. The results provide a guide for the design of a polisher and the determination of a process in line-orbit chemical mechanical polishing.