Abstract: Endpoint control of thickness of a film being deposited or etched is achieved by use of an ellipsometer that derives delta and psi coordinates of a polarized light beam reflected from the work piece during the course of processing. Measured film thickness is a function of the delta and psi coordinates and other parameters. Delta and psi coordinates of a selected end point (final film thickness) of the process are calculated, and an unbounded line through the endpoint perpendicular to the direction of a plot of delta and psi coordinates adjacent the endpoint is defined. As the processing continues, an ERROR is generated that becomes zero when measured delta and psi coordinates are on the line. When this error changes sign, in the appropriate cycle and within a reasonable range of the endpoint, the desired thickness has been attained, and the process is stopped. The improved film thickness endpoint control is used in a rapid thermal processing system wherein temperatures are changed at a rate of 100.degree. C.

Abstract: A diffusion furnace and method for processing semiconductor wafers standing on edge wherein the furnace has vertically adjacent electrical resistance heating elements wired in parallel and disposed above the wafers. This arrangement enables the heat input to the furnace by the heating elements to be varied. In a preferred embodiment, the heating elements in the upper section of the tube are connected in one circuit and the heating elements in the lower section of the tube are connected in a second circuit and each circuit is controlled in response to the temperature in that section.

Abstract: There is a substantial heat loss and drop in temperature in a hot-wall diffusion tube when a batch of wafers at room temperature is loaded into the tube. The temperature of the atmosphere in a zone in the tube is quickly recovered by sensing both the temperature of the tube atmosphere and the temperature of a heating element surrounding the zone with thermocouples, mixing the signals of the thermocouples to produce a ratio average signal and then controlling the heat input to the heating elements in response to the ratio average of the sensed temperature.