An analytical approach to quantify the thermal budget in consideration of consecutive thermal process steps

For characterizing the susceptibility of processes or process flows for diffusion effects, usually the term "thermal budget" (TB) is used. However, even though there are several definitions of the TB, still no quantitative and manageable description of the TB of several consecutive process steps exists due to the Arrhenius-nature of diffusion processes. This paper presents an analytical approach to quantify the TB of a given CMOS process flow based on the shift of a pn-junction due to thermal process steps. Furthermore, classification numbers for each process step were introduced which allow one to rate their significance with regard to the TB. In conjunction with a device specification-dependent diffusion limit, it is then possible to determine the remaining temperature-time-window at each stage of the process flow.