Multiple zone inverse diffusion solver for silicon processing

In this paper we present the implementation and testing of an inverse diffusion solver that determines implant doses and drive-in times for a set of coupled one-dimensional diffusion profiles spreading over several regions of a device. The solver starts with a description of each distinct device diffusion region in terms of a set of junction depth x/sub j/ and peak concentration c/sub s/ specifications, and a simplified description of the process flow. From this information, the solver setups a storage data structure containing the full history of each profile within each region at each process step. Starting from a guess for the dose and drive-in times, the software first fills the storage structure with approximate profiles and then iteratively solves the problem backwards starting from the last diffusion to the first followed by a forward guess correction loop. The backward-forward recursion loop is repeated until errors in x/sub j/ and c/sub s/ are negligible. The solution method was successfully tested with several conventional device structures.