Physical aspects of particle deposition in RTP

Advanced-logic and DRAM technology for the 90 nm node and beyond results in increasingly stringent particle specifications. Particles can be transported to the sensitive wafer surface via sedimentation, convective diffusion, thermo- electro-and photophoresis. Depending on the manufacturing equipment, the various transport mechanisms are more or less dominant. In atmospheric rapid thermal processing (RTP) equipment for instance, thermophoresis strongly influences the particle transport. Therefore it is important to control this effect such that it protects the wafer surface from particles rather than contaminate it. This paper briefly explains the physical aspects of the different particle transport mechanisms, but mainly it focuses on experimental data on thermo- and photophoresis, including 10000 wafer marathon run and production data. For particle generating processes correctly tuned thermophoresis reduces the particle number on the wafer by an order of magnitude