Trench MOSFET fabrication flow

1. Ion implantation (N+)

Mask with resist and inject nitrogen ions (N +).

Since SiC has a low diffusion coefficient, it is necessary to implant several types of energy by ion implantation instead of thermal diffusion technology to change the implantation energy in the depth direction. For SiC substrates, high temperature injection and low temperature injection are used properly depending on the concentration to be injected.

Ion Implantation for SiC

Introduction of Ion Implanter

2. Ion implantation (P+)

Mask with resist and inject phosphorus ions (P +).

Since SiC has a low diffusion coefficient, it is necessary to implant several types of energy by ion implantation instead of thermal diffusion technology to change the implantation energy in the depth direction. For SiC substrates, high temperature injection and low temperature injection are used properly depending on the concentration to be injected.

Ion Implantation for SiC

Introduction of Ion Implanter

3. Mask deposition for Trench process

An insulating film is deposited by CVD for trench processing.

4. Mask etching

Apply resist and dry-etch the mask of the trenched part.

In order to make the trench shape vertical, it is necessary to etch the mask vertically, and at that time, it is necessary to suppress the roughness of the side wall.

Introduction of SiC Trench etching

Introduction of GaN Trench etching

5. Trench ethcing

Trench processing is performed by dry etching. Smoothness of the side walls and a round shape at the bottom of the trench are required.

Introduction of SiC Trench etching

Introduction of GaN Trench etching

6.Carbon cap (For SiC)

In the activation annealing process, SiC requires high temperature annealing of 1600 ° C or higher due to the strength of the bond. In the case of SiC at high temperatures, Si evaporates and causes surface roughness, so this is dealt with by forming a dense carbon film by sputtering.

Ion Implantation for SiC

Sputtering system for Carbon Cap

7.Annealing & Removing carbon 

After annealing, removing carbon by ashing

8. Gate electrode

Poly-Si is deposited to from gate electrode.

9. Gate insulator film

SiO2 is deposited by CVD.

Make a resist pattern and process SiO2 by dry etching.

Introduction of CVD system

10.Source electrode

Metal is deposited by vapor deposition or sputtering to form electrodes.

Introduction of Sputtering system

11.Backside electrode

Metal is deposited by vapor deposition or sputtering to form electrodes.

Introduction of Sputtering system