Plasma Enhanced Chemical Vapor Deposition (PECVD)
Plasma Enhanced Chemical Vapor Deposition (CVD) uses plasma of ionized species to break one or more stable volatile precursors to deposit high quality thin films on desired substrates. Plasma is created by applying high RF electic field around the area near the substrate. Plasma is widely known to break stable molecules that would have otherwise taken much higher thermal energy (or temperature) to break. These reactive plasma species deposit on heated substrate to deposit thin film of interest. Unlike CVD which uses only thermal energy on substrate, PECVD process uses both energy from plasma and thermal energy on substrate to achieve desired chemical reaction for thin film growth. For example, Silane and Nitrous Oxide can deposit SiO2 films at 280 C using PECVD process. The same chemistry using a CVD process would have taken more than 800 C to grow SiO2 film. Lower temperature also permits deposition on substrates that may not withstand higher temperatures. Plasma can also help controlling stress in the thin films.
Many standard precursors are available today that can deposit metals, silicon oxide, silicon, silicon nitride, etc by PECVD process. Precusor must be volatile, leaves no impurity in deposited films, and give desired film properties (such as uniformity, electrical resistance, roughness, etc.). All byproducts from PECVD surface reaction should be volatile and easily removable in vacuum.
The above process can be carried out in IMSE Facility. IMSE offers (Nanofab PECVD system) to accomplish the task safely. Click the link to start the training process.
Thin film metrology
Estimating film growth peformance (deposition rate, planar roughness, etc.) is critical to fabricate device at micron scale in repeated manner. IMSE offers number of instruments ( Ellipsometer, Profilometer, Optical Microscope, SEM) to help in the quantitative measurements.
- Optical microscope can measure the critical dimension width (for patterned thin films)
- Profilometer can measure the thin film height as long as step edge is available. The simplest solution may be to cover part of planar surface with kapton tape during metal deposition. Instrument may also be used to estimate roughness of etched films.
- Ellipsometry can measure the film thickness of selected materials when deposited on Silicon substrate. Unlike profilometer, no patterned region should exist in the area of measurement.