Low stress PECVD—SiNx layers at high deposition rates using high power and high frequency for MEMS applications

Abstract

The paper reports a new fabrication method for low stress SiNx layers at high deposition rates in a PECVD reactor using high power and high frequency (13.56 MHz) and their MEMS applications. By increasing the deposition power at 600 W in high frequency mode, a decrease of the tensile residual stress to values between 0 and 20 MPa was noticed. Meanwhile, the high power, which promotes a high dissociation of gases, generates a high deposition rate (in the range 250 to 350 nm min−1). In addition, the paper presents the influence of other important parameters that affect the residual stress and deposition rate such as pressure and SiH4, NH3 and N2 flow rates. SiNx layers fabricated at high power in high frequency mode were successfully used in two classical MEMS applications: fabrication of the masking layer for anisotropic wet etching in KOH solution and fabrication of a low stress cantilever.