Determination of the Emitter Lateral Doping Profile for Self-aligned Bipolar Transistors

The lateral arsenic doping profile of the emitter outdiffused from the polysilicon layer has been estimated. It has been done by a combination of measured E/B depletion junction capacitance CEB and that calculated by 2D simulation. Since the peripheral CEB is very sensitive to the lateral doping profile, it is varied until the simulated CEB reproduces the measurement. The result shows that the lateral diffusion length is very much dependent on the drive-in condition for the diffusion. The drive-in temperature of 1050 °C / 10 sec gives the lateral diffusion of about 75 %. That of 1075 °C / 10 sec gives nearly 100 % of the vertical one.