Furnace annealing after plasma processing and other process steps such as implantation and contact formation in advanced CMOS processing are extensively used to improve the overall device characteristics. With an ever emerging trend towards lower thermal budget processing and the unique capabilities of RTP to provide that along with flexibility to change process ambients, we present the results of our experiments to do low temperature mixed gas and pure hydrogen anneals in RTP and study its effects on junction leakage and transistor characteristics.
Recently, with the advent of the contact plug technology, the sintering function is not as important as the alloy effect on the transistor and junction device parameters. Therefore, the requirements for the alloy are more related to threshold voltage, (Vt) uniformity and reduced junction leakage. The key is that the hydrogen atoms diffuse far into the silicon to reach the dangling bonds at the field edge and by the transistors. The hydrogen rapid thermal processor (HRTP) can accomplish the basic device annealing function as long as there is sufficient time for hydrogen diffusion and reaction time. The aluminum metallization limits the temperature to 500°C due to increased metal roughness and increased metal resistance. Also, the hotter temperatures compete in the reaction by breaking hydrogen bonds as well as satisfying the dangling silicon bonds. The best ambient gas was at 100% hydrogen flow at low pressure with HRTP times in excess of one minute.