Advanced RTP-process for boron-doped and oxygen contaminated Cz silicon
An improvement of the stable carrier lifetime was achieved by Rapid Thermal Processing (RTP). On three different Cz materials and a FZ material the influence of the plateau temperature on the stable lifetime was investigated. At plateau temperatures below 900 °C, the carrier lifetime can be improved using an optimized process whereas at temperatures above 900 °C, the carrier lifetime is decreased not only for all Cz materials but also for FZ materials. Interestingly, in two subsequent high-temperature steps the last step determines the stable carrier lifetime and the degraded stable lifetime due to a first step can be reversed by an optimized second step. The effect of such process sequences on the standard RTP-solar cell has been analyzed.