Etching Process Module Development for SiC CMOS Devices

Student: Wes Renfrow

Degree: M.S., May 2022

Major Professor: Dr. Alan Mantooth​

Research Area(s):

Energy Materials & Devices ​

View Research Quadslide

Background/Relevance

  • Silicon Carbide (SiC) is a wide bandgap semiconductor that has become very popular in recent years for being a promising material for extreme environment electronics.  By creating SiC based CMOS devices, electronics can function in environments where silicon-based electronics would fail. Some benefits of SiC include:
    • High thermal conductivity

    • High drift saturation velocity​

Innovation

  • Create etching process modules for SiC CMOS devices that can be used in extreme environments. These devices can function in extremely high temperatures and areas with high radiation. 

Approach

  • Etching is the process of creating patterns in the semiconductor by removing specified areas. This can be done by dry etching using pressurized plasma or by wet etching using liquid chemicals to dissolve the material. Etching is vital to many steps in the CMOS development process such as implanting the ohmic contacts.
  • The etching method for each process needs to be calibrated so that the features are accurately transferred to the material and the depth of the etch is correct.
Etching in the shape of a star

Key Results

  • Using an inductively coupled plasma etcher we have been able to use a mixture of Cl2 and BCl3 gas to etch SiC at an etch rate of 132nm/min with a PR/SiC selectivity of 2.06.
  • The resolution of the etch was limited by the resolution of the photoresist. To increase the resolution, we have worked to improve our photolithography process. By changing our original process, we have observed significant improvements in our resolution.​
Color map showing height of the SiC; Height data plot

Conclusions

  • This work supports the understanding of the theory and principle of:
    • Etching silicon carbide using inductively coupled plasma as well as other methods of wet etching.
    • Photolithography processes that can be used through various steps in the CMOS development process.

Future Work

  • Future work will be to further understand and develop the etching processes of depositing ohmic contacts in SiC CMOS devices