RF sputtering: A viable tool for MEMS fabrication

Abstract

Fabrication of Micro-Electro-Mechanical-Systems (MEMS) requires deposition of films such as SiO 2 , Si 3 N 4 , ZnO, polysilicon, phosphosilicate glass (PSG), Al, Cr-Au, Pt, etc. for use as structural, sacrificial, piezoelectric and conducting material. Deposition of these materials at low temperature is desirable for fabricating sensors/actuators on temperature-sensitive substrates and also for integrating MEMS structures on silicon in post-CMOS processing procedures. Plasma enhanced chemical vapour deposition (PECVD) and sputtering are amongst potential techniques for preparing films for MEMS fabrication at comparatively low temperatures. The sputtering technique has an added advantage that the process is carried out in an inert ambient (argon) and chemically sensitive substrate/sacrificial layers can be used in realization of MEMS. Furthermore, the same system can be used for depositing dielectric, piezoelectric and conducting materials as per requirement in the fabrication sequence. This enables rapid low-cost prototyping of MEMS with minimum fabrication facilities.In the present work, we report preparation, characterization and application of RF sputtered SiO 2 , Si 3 N 4 and ZnO films for MEMS fabrication. The effect of RF power, sputtering pressure and target-to-substrate spacing was investigated on the structural and other properties of the films. The residual stress in the films was obtained using wafer curvature measurement technique. The deposition parameters are optimized to obtain low stress films of SiO 2 and Si 3 N 4 . The self-heating of the substrate during deposition was advantageously exploited to obtain highly c-axis oriented films of ZnO without any external heating. A variety of MEMS structures such as cantilever beams, micro-bridges, diaphragms, etc. are demonstrated using bulk, surface and surface-bulk micromachining techniques.

Characteristics of GaN Thin Films Using Magnetron Sputtering System

“…Growing high quality GaN has been a main challenge as this material does not exist purely in nature [6] [7]. Most of the fabrication processes are not suitable for sensitive electronic applications as they are complex, involve corrosive materials, and require high temperature depositions [8]. In the present work, we extend the research by investigating optimized sputtering conditions of GaN and AlGaN, for the purpose of preparing an AlGaN/GaN heterostructure by RF magnetron sputter technique.…”

Modulation of electrical properties of sputtered Ta2O5 films by variation of RF power and substrate temperature

“…Though preparation of high-quality Ta 2 O 5 film is a challenging issue, many possible methods are used to fabricate Ta 2 O 5 thin film such as chemical vapor deposition (CVD) technique [27], thermal oxidation [28], e-beam evaporation [29], atomic layer deposition [30], anodization [31], DC sputtering [32], RF sputtering [20] and sol-gel process [33]. Among these techniques, RF reactive magnetron sputtering has many advantages due to its low deposition temperature, non-toxic approach, uniformity, conformal coverage, and high yield [34][35][36]. Furthermore, the properties of the sputtered thin film depend upon the different process parameters such as RF power, working pressure, substrate temperature, and argon (Ar) to oxygen (O 2 ) gas flow ratios.…”

Suppression of Oxide and Interface Charge Density in Radio Frequency Sputtered Ta2O5 Thin Films

“…[29][30][31][32] Among these deposition techniques, sputtering is a low-temperature, nontoxic, complementary metal-oxide-semiconductor (CMOS)-compatible technology that produces a smooth uniform thin film of excellent quality. [33,34] Regardless of the methodology adopted for Ta 2 O 5 synthesis, the deposition parameters have a significant impact on the properties of Ta 2 O 5 film. The sputtering parameters such as working pressure and Ar/O 2 gas flow ratio have a significant impact on growth kinetics during the sputtering process.…”