NanoLab Research on SiC

 

Chemical Vapor Deposition of SiC thin films

Activities include thin film growth by CVD, surface studies, metallization, doping, and etching. Device applications of wide band gap materials are designed for "extremes" of temperature, power, radiation, etc.  Using novel precursors, crystalline SiC thin films have been deposited at temperatures as low as 700 C.  For CVD the current aim of research is the growth of SiC thin film on Si or SiC substrate from organosilane precursors, which is part of a larger effort to make superior electronic devices which can work at high temperature, high power, and a highly corrosive environment. The precursors utilized in the study are mainly trimethylsilane and silacyclobutane  The structural and chemical properties along with growth mechanisms of the films have been investigated by variety of surface SiC_PSG_Si(100).jpg (9756 bytes)analysis techniques. Additionally, electrical properties of the SiC films are mainly measured by Hall effect.  At this time, the clear object of SiC research is trying to optimize growth process to obtain SiC films with best electrical properties for next generation electronic devices.  Recently, we have directly grown 3C-SiC(111) on SiO2, Si3N4 and ploy-Si surface by CVD from organosilanes (pictured left), which makes SiC a perfect material for high temperature MEMS application. In addition to MEMS application, SiC could also be integrated into the current Si-based microelectronics fabrication process for gate dieletric materials and diffusion barrier for Cu interlayers. Finally, this process could also be used to fabricate SiC SOI structure

 

 

SiCOI for MEMs and Fiber-optic Applications (Lin)

An increasing demand for micro-sensors that can operate at temperature well above 300C and often in severe environments (such as those in automotive and aerospace applications, in combustion processes or gas turbine control, and in oil industry) has stimulated the search for alternatives to conventional Si. The research in direct formation of SiC films on insulating substrates (SiCOI structures) in this study finds a very promising technology for producing complicated SiC device structures and provides an excellent alternative material solution for robust MEMS devices operating at high temperature.

 

Two kinds of SiCOI structures, SiC/poly-Si/SiC/Si3N4/Si for bent-beam strain sensors and SiC/sapphire for electrically passive fiber-optic temperature sensors, have been fabricated, as shown in the attached pictures. The research work in this study extends from SiC thin-film growth using a single organosaline (3MS) precursor and a rapid thermal LPCVD system, photolithography and ICP etch of SiC thin-films, as well as material & device characterization. The techniques used to characterize the as-grown and patterned SiC thin-films and starting substrates include XRD, SEM, AFM, Hall Effect, four-point probe, mercury probe, FTIR, XPS, depth profilometer, UV-Visible-IR absorption/transmission/reflection spectroscopy, and UV-Visible-NIR fiber.

 

The ease of deposition and the ability to deposit large area SiC thin-films on many different insulating substrates make the SiCOI structures very attractive for many MEMS applications, particularly in connection with surface micro-machining fabrication techniques. The growth temperature and 3MS flow rate are the two key parameters on the grain size and the distribution of grain orientations, which determine the structural, electrical and optical properties of the SiC thin-films and related device performance. Moreover, the ability to use electrically passive poly-SiC fiber-optic temperature sensors gives the unique advantages of SiCOI for low-cost, robust, high-temperature applications in harsh environments.