Wafer Warp Elimination Through Control of Process Gas System
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
A technique for eliminating film stress and wafer warping when films are deposited on wafers via low pressure chemical vapor deposition is provided. The technique comprises optically monitoring the index of refraction of the growing film, and feeding the index of refraction results back to a system which dynamically controls the gas composition ratio during deposition such that the refractive index of the depositing film is maintained at a value constantly equal to the characteristic refractive index for the temperature being used. Stresses due to film tension are created on a silicon wafer when nitride process films are applied to the wafer. The stresses are known to cause warpage of the wafer. The warpage results in the magnification error during lithographic exposure which causes overlay and linewidth error.