Avalanche Breakdown Voltage in Silicon Diffused p-n Junctions as a Function of Impurity Gradient

A method is presented for controlling the reverse breakdown voltage (VB) in a silicon graded junction. The significant process parameters are shown to be resistivity, time of diffusion, and temperature of diffusion. For a constant resistivity, VB increases with the fourth root of the time of diffusion and with the square root of the depth of diffusion as predicted by theory. Statistical analysis shows that the mean breakdown voltage for a large group of units can be predicted within 2%. The method fails for very low or high resistivity material.