Lamp design for fast cooling of rapid thermal processes with a two-zone lamp using a step cooling process

The concept of rapid thermal processing (RTP) has many potential applications in microelectronics manufacturing, but the detail of chamber design remains an active area of research. Within the framework of linearized thermoelasticity theory, the temperature and thermal stresses on the wafer for RTP are solved by using a fully implicit finite difference approach and the Thomas algorithm in conjunction with the maximal shear stress failure criterion. The results show that the radial temperature difference in the wafer produces thermal stresses that can often exceed the yield stress in silicon wafers, causing plastic deformation. The temperature non-uniformity is caused by edge effects and the geometric relation between the chamber and the wafer. A design criterion using a two-zone lamp during RTP is suggested that can compensate for the edge effects at the wafer as compared to a one-zone lamp design. The results show that the lamp design of a two-zone lamp using a step cooling process is more efficient, and can significantly shorten the required cooling time and decrease thermal budgets. Thus, the conventional lamp design of a one-zone lamp with a continuous cooling process is not appropriate for the rapid thermal process.