Fabrication and characterization of amorphous Si films by PECVD for MEMS

Abstract

Thick and smooth amorphous Si film of 2 µm without hillocks has been obtained at low temperature of 300 °C by plasma-enhanced chemical vapor deposition (PECVD) technology. In comparison with conventional sputtering deposition, PECVD-deposited thick amorphous Si film has better adhesion to Si or oxide substrate without cracking or peeling. The film quality depends on the following process parameters: RF power, frequency mode and gas flow ratio as well as substrate material. The deposition rate increases with the RF power for both RF modes of 380 kHz and 13.56 MHz, and higher deposition rate together with lower compressive stress occurs at high frequencies of 13.56 MHz. Amorphous Si film without hillocks is formed on the 100 nm oxide/Si(100) substrate while some hillocks appear on the top of the amorphous Si film deposited on the crystalline Si(100) substrate. Good quality of amorphous Si at low temperature is very important for the fabrication of MEMS devices. Fabrication of suspended MEMS microstructure and sensor array has been demonstrated using the smooth amorphous Si films as sacrificial layer in surface micromachining.

Low Stress PECVD SiNx Process for Biomedical Application

“…A schematic diagram of the equipment was presented by Chung et al in [11]. The unique characteristic of the system is that the plasma can be activated in two RF modes: at 380 kHz (LF) and/or at 13.56 MHz (HF).…”

“…The developed process was able to produce near zero stress SiNX layers with a high deposition in a PECVD reactor. The developed process was used to deposit thick SiNX layer and produced 11 ltm layers with around 2.5MPa stress. These layers can be used to fabricate large area window which will be used in cell culture experiments.…”

Integrated design of MEMS: aiming at manufacturability

“…1) Example: Thick and smooth amorphous Si film of 2 µm without hillocks has been obtained at low temperature of 300 • C by PECVD technology [3]. Fabrication of suspended MEMS microstructure are thus accessible (Fig.…”

Evaluation of Au/a-Si eutectic wafer level bonding process

“…They have obtained better results compared to the Au/c-Si (crystal Si) bond type. However, the uniformity and amorphous level of a-Si formed by PECVD process are relatively difficult to control [9], which would decrease the uniformity of the bonding. Thus, we introduce the ion implantation technology to form the amorphous layer for Au/Si bonding [10].…”