Theoretical modeling of the detailed surface chemistry and concomitant surface evolutions during microsystems fabrication processes is recognized as having great potential for improving surface micromachining (SMM) process fabrication technologies. For example, there is a clear need to better understand the fundamental factors leading to surface non-uniformities and how to control these effects. The value of modeling in this area has been demonstrated by earlier researchers and advances have been made in developing transport models, chemical mechanisms, and surface evolution modeling. Currently available computer codes, however, have not been designed to use large parallel architectures efficiently, nor fully exploit all of the modeling advances that different researchers have made. Thus size and complexity of problems that have been addressed have been limited.

We are developing ChISELS (Chemically Induced Surface Evolution with Level-Sets), a parallel code to model 2-D and 3-D material depositions and etches at feature scales on patterned wafers at low pressures. ChISELS is a platform on which to build and improve upon previous feature-scale modeling tools while taking advantage of the most recent advances in load balancing and scalable solution algorithms. The framework in which the ChISELS code is built is based upon the level-set method for modeling evolving interfaces. The level-set method, an implicit interface tracking technique, was chosen for its natural ability to handle changes in topology that frequently occur, for example, when films are grown in high aspect-ratio features in MEMS devices.

From the level-set function, the surface is discretized into linear (planar) elements. A ballistic transport model is employed to solve for the fluxes incident on each of the surface elements. Surface Chemkin is used to model the chemical reactions at each surface element determining the rate of growth of the surface. The collection of these tools is then used to aid in understanding surface chemistry or to model, in our case, the SUMMIT V growth and etch processes used to fabricate MEMS at Sandia National Laboratories.

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.