In this paper, we examine alternative methods for reducing thedimensionality of nonlinear dynamical system models arising incontrol of rapid thermal chemical vapor deposition (RTCVD) forsemiconductor manufacturing. We focus on model reduction forthe ordinary differential equation model describing heattransfer to, from, and within a semiconductor wafer in theRTCVD chamber. Two model reduction approaches are studied andcompared: the proper orthogonal decomposition and the method of balancing.This leads to a discussion of computational issues in the practicalimplementation of balancing for nonlinear systems.