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SIERRA is a 3-D general purpose semiconductor device simulation program which serves as a foundation for investigating integrated circuit (IC) device and reliability issues. This program solves the Poisson and continuity equations in silicon under dc, transient, and small-signal conditions. Executing on a vector/parallel minisupercomputer, SIERRA employs a matrix solver which uses an incomplete LU (ILU) preconditioned conjugate gradient square (CGS, BCG) method. The ILU-CGS method provides a good compromise between memory size and convergence rate. We have observed a 5X to 7X speedup over standard direct methods in simulations of transient problems containing highly coupled Poisson and continuity equations such as those found in reliability-oriented simulations. Also, the applications of SIERRA to parasitic CMOS latchup and dRAM Single Event Upset studies are described.

A detailed analysis of various mechanisms involved in alpha-particle induced charge transfer between two trench type dRAM cells is reported and an analytical model has been developed to represent the transfered charge. The results compare very favorably with detailed simulation results.UANTITATIVE modeling of the upsets due to alphaarticles has become necessary for development of e large dRAM's. Furthermore, due to purely geometrical factors, the probability of an alpha-particle track intersecting two adjacent cells in trench type storage devices becomes significant as separations shrink. It is then essential to understand how the charge transfer under these conditions differs from that occurring in the much studied single cell case. Convincing qualitative arguments have been offered which assert that the alpha-particle track will act as a plasma wire which short circuits the two cells. Under this model the two cells will ultimately be brought to the same potential unless the cell capacitance is so large that the plasma track dissipates by radial spreading before the charge transfer is complete.We have developed analytical models which describe this situation. These models were stringently tested by applying them to two-dimensional (2-D) structures under a wide variety of conditions and comparing the results to those obtained from our modified version of the 2-D device simulator, PISCES. Predictions from the analytic model compared very favorably with the results of numerical simulation. It is shown below that the analytical models are directly applicable to the threedimensional (3-D) case.This letter presents numerical values for the charge transfer in 3-D structures and provides a brief description of the physics of this phenomenon with emphasis on the ways it differs from the single cell problem.As a result of 2-D simulations on structures such as that shown in Fig. 1, it has been found that an alpha particle track intersecting two trenches can look like a "plasma wire" shorting the trenches. (See Fig. 2 t = 0.3 ps curve.) However the wire starts to "dissolve" in a few picoseconds (Fig. 2 t = 20 ps) greatly reducing its potential as a powerful charge transfer mechanism. The duration of alpha-particle induced shorting is much less than expected on the basis of conventional analysis since it is governed by mechanisms other than the conventionally assumed radial ambipolar diffusion rate.