KINETICS OF GETTERING IN SILICON

Two basic functions of getters in silicon during gettering processes are investigated in detail. The sink action of getters for absorbing impurities is described by a gettering parameter g, which relates to the diffusion ratio g(d), segregation coefficient S, and the activation energies E(m,Si), E(m,G) of impurities in intrinsic Si and in the getter phase. The kickout mechanism is suggested for describing the diffusion of impurities because of the contribution of Si interstitials to kick out the impurities to be gettered. Based on the interaction of Si interstitials with impurities and the influence of the sink in absorbing impurities, a set of gettering equations is derived and used to calculate the gettering of gold in silicon with back surface getters. Theoretical results agree well with reported experimental data and five conclusions are provided to determine the optimal gettering conditions for a given gettering cycle.