The Effect Of High Temperature Annealing On Surface Guality And Oxvqen Precipitation Of Polished Czochralski Silicon Wafers

Surface quality and oxygen precipitation (OP) of the polished Czochralski (Cz) silicon wafers are of significance for manufacturing yield of integrated circuits (ICs). The Cz silicon wafers are generally subjected to high temperature anneal in either silicon wafering or IC fabrication processes. Therefore, it is necessary to explore the effects of high temperature anneal on the surface quality and OP of CZ silicon wafers. In this thesis, the surface status and OP in200mm polished CZ wafers received high temperature anneal have been investigated. The primary results are described as follows:1. The issues of appearing colorful and white hazes during1200℃anneal that is used for annihilation of crystal-originated-particles in200mm CZ silicon wafers have been addressed. The colorful hazes can be eliminated by cleaning the furnace tube for removal of metal contaminations. While the visible white hazes can be eliminated by appropriate polishing means, the hazes detected by laser scatterometer are significant and distribute non-uniformly across the wafers. Such surface hazes are not well correlated with the surface micro-roughness.. It seems that the appearing of surface hazes is a "persistent ailment" of high temperature anneal for CZ silicon wafers. It can be cured by a refine polishing process.2. The effects of high temperature pre-anneal on OP in Cz silicon wafers have been investigated. It is found that the high temperature pre-anneal can significantly enhanced OP in the subsequent low-high two-step anneal and the three-step anneal consisting of high temperauture RTP and low-high conventional furnace anneal. Such enhancement effect becomes stronger with increasing time of pre-anneal at high temperature. It is believed that the high temperature pre-anneal annihilates the grown-in oxygen precipitates and therefore the accompanied silicon-interstitials, which facilitates the OP nucleation in the subsequent anneal.3. It is found that the application of high temperature anneal prior to the RTP-based internal gettering (IG) process can substantially reduce the annealing time for the growth of oxygen precipitates at high temperature and, moreover, increase the bulk micro-defect density and therefore the IG capability. It is shown that the high temperature pre-anneal can be used to reduce the thermal budget of the RTP-based IG process.