Abstract: A cage for low pressure chemical depositions reactors to provide for the relatively uniform deposition of silicon dioxide and phosphorus doped polysilicon along the length of a reactor by the chemical decomposition of silane. The cage is comprised of an open structure, generally surrounding semiconductor wafers supported on boats within the reactor, so as to discourage preferential deposition rates adjacent the silane inlet region of the reactor, and to encourage a more uniform distribution of the decomposable gas along the reactor length to effect more uniform deposition rates than previously accomplished. The open structure helps to quickly develop the flow along the reactor so that the flow quickly stabilizes adjacent the inlet end of the reactor and remains substantially uniform thereafter. Longitudinal alignment of the major elements of the cage provides continuous flow surfaces along the length of the reactor.