Characterization & Optimization of Low Stress PecVD Silicon Nitride for Production GaAs Manufacturing
Kenneth D. Mackenzie, Brad Reelfs, Michael W. DeVre, Russell Westerman, and David J. Johnson
Unaxis USA, Inc., 10050 16th North,
Keywords: PecVD, silicon nitride, stress, manufacturing
A designed experiment has been used to characterize and optimize a process for low-stress silicon nitride deposition using a commercial batch PecVD reactor developed for production GaAs manufacturing. The deposition process is based on a low power, low damage technique in which precise control of the silicon nitride stress is achieved by adjusting the relative concentration of N2 and He carrier gases in the plasma. In the designed experiment, the influence of rf power, NH3 gas flow rate, and also N2/He concentration on film stress, deposition rate, refractive index, thickness non-uniformity, and wet etch rate resistance has been investigated. From the analysis of the design, a practical process regime has been established to achieve a highly uniform low-stress silicon nitride film with high wet etch resistance.
To understand the mechanism for stress control by the above technique, optical spectroscopic analysis of different N2/He plasmas in the PecVD reactor has been performed. Results from this work are also presented.