Effect Of Rapid Thermal Processing On Mechanical Properties Of Silicon

The mechanical properties of silicon are becoming more and more important due to the decreasing feature size of integrated circuits (ICs), increasing diameter of silicon wafer used for ICs and increasingly stringent requirements on silicon wafer processing. As one of the most important processes in manufacturing of ICs, rapid thermal processing (RTP) can lead to the injection of nitrogen impurity into silicon. However, the effect of RTP on the mechanical properties of single crystalline silicon has been rarely studied. In this thesis, the glide of dislocations during RTP and the effect of RTP on the dislocation motion, modulus, hardness and fracture toughness in silicon have been investigated. The results achieved in this thesis are listed as follows:(1) The motion of dislocations originated from Vicker indentations in single crystalline silicon wafers subjected to high temperature RTP under different atmospheres has been investigated. It is found that the dislocations move very rapidly due to the release of residual stress around the indentation during the RTP. Moreover, as the RTP temperature exceeds1100℃, the gliding distances of dislocations in the specimens subjected to the RTP under nitrogen (N2) atmosphere are much shorter than those in the counterparts received the RTP under argon (Ar) atmosphere. We believe that the nitrogen atoms injected into the indentation by the RTP under N2atmosphere exhibit pinning effect on dislocation motion.(2) Effect of prior RTP under different atmospheres on the motion of dislocations initiated from indentations in Czochralski (CZ) silicon has been investigated. It is found that the maximum gliding distances of dislocations in the specimens with the prior RTP under N2atmosphere are much smaller than those in the specimens with the prior RTP under Ar atmosphere. This is also the case when the specimens received annealing for oxygen precipitation (OP) subsequent to the RTP at1250℃under N2and Ar atmospheres, respetively. It is believed that the nitrogen atoms introduced during the RTP under nitrogen atmosphere or the oxygen precipitates facilitated by the RTP-introduced nitrogen atoms can exhibit pinning effect on the dislocation motion, which increase the critical resolved shear stress for dislocation glide.(3) Effect of the prior RTP at high temperature on the modulus, hardness and fracture toughness of silicon has been researched by nanoindentation and microindentation. For CZ silicon, the prior RTP under Ar atmosphere reduced the modulus, hardness and fracture toughness of silicon, the prior RTP under N2atmosphere also reduced the modulus and hardness of silicon, but increased the fracture toughness. For FZ silicon, the prior RTP under Ar atmosphere reduced the modulus and hardness of silicon, while the prior RTP under N2atmosphere have almost no influence on them. Both the prior RTP under two different atmospheres have little impact on the fracture toughness and the phase transformation behavior of silicon.