Xiaolin Dai

Optimization of heat shield for single silicon crystal growth by using numerical simulation

In integrated circuit-grade single silicon Czochralski growth, the position and material of heat shield are main parameters affecting the heat exchange and crystal growth condition. By optimizing the above parameters, we attempted to increase the growth rate and crystal quality. Numerical simulation proved to verify the results before and after optimization. Through analyses of the temperature and microdefect distribution, it is found that the optimized heat shield can further increase the pulling rate and decrease the melt/crystal interface deflection, increase the average velocity of argon flow from ∼2 to ∼5 m·s−1, which is in favor of the transportation of SiO, and obtain the low defects concentration crystal and that the average temperature along the melt-free surface is 8 °C higher than before avoiding supercooled melt effectively.

Effect of thermal shield and gas flow on thermal elastic stresses in 300 mm silicon crystal

Abstract The thermal elastic stresses induced in 300 mm Si crystal may be great troubles because it can incur the generation of dislocations and undesirable excessive residual stresses. A special thermal modeling tool, CrysVUn, was used for numerical analysis of thermal elastic stresses and stress distribution of 300 mm Si crystal under the consideration of different thermal shields and gas flow conditions. The adopted governing partial equations for stress calculation are Cauchys first and second laws of motion. It is demonstrated that the presence and shape of thermal shield, the gas pressure and velocity can strongly affect von Mises stress distribution in Si crystal. With steep-wall shield, however, the maximal stress and ratio of high stress area are relatively low. With slope-wall shield or without shield, both maximal stress and ratio of high stress area are increased in evidence. Whether thermal shields are used or not, the increase of gas flow velocity could raise the stress level. In contrast, the increase of gas pressure cannot result in so significant effect. The influence of thermal shield and gas flow should be attributed to the modification of heat conduction and heat radiation by them.

Advanced silicon and silicon-based materials for fast transition from micrometer- to nanometer-scale integrated-circuit technology

300 mm silicon single crystals have been grown using 24-28¿ hot zones with the aid of numerical simulation. Mechanical strength of silicon seeds has been tested and a new style seed chuck developed. The damage layers during cutting, double side grinding (DSG) and double side polishing (DSP) have been investigated. The processing technology and the defects in silicon based materials such as silicon on insulator (SOI) and silicon germanium (SiGe) have also been discussed.