Main steps in SiC substrate processing

The processing of 4H-SiC substrate mainly includes the following steps:

1. Crystal plane orientation: Use X-ray diffraction method to orient the crystal ingot. When a beam of X-rays is incident on the crystal plane that needs to be oriented, the crystal plane direction is determined by the angle of the diffracted beam.

2. Cylindrical tumbling: The diameter of the single crystal grown in the graphite crucible is larger than the standard size, and the diameter is reduced to the standard size through cylindrical tumbling.

3. End grinding: The 4-inch 4H-SiC substrate generally has two positioning edges, the main positioning edge and the auxiliary positioning edge. The positioning edges are grinded out through the end face.

4. Wire cutting: Wire cutting is an important process in the processing of 4H-SiC substrates. Crack damage and residual subsurface damage caused during the wire cutting process will have an adverse impact on the subsequent process. On the one hand, it will prolong the time required for the subsequent process, and on the other hand, it will cause the loss of the wafer itself. Currently, the most commonly used silicon carbide wire cutting process is reciprocating diamond-bonded abrasive multi-wire cutting. The 4H-SiC ingot is mainly cut by the reciprocating motion of a metal wire bonded with diamond abrasive. The thickness of the wire-cut wafer is about 500 μm, and there are a large number of wire-cut scratches and deep sub-surface damage on the wafer surface.

5. Chamfering: In order to prevent chipping and cracking at the edge of the wafer during subsequent processing, and to reduce the loss of grinding pads, polishing pads, etc. in subsequent processes, it is necessary to grind the sharp wafer edges after wire cutting into Specify the shape.

6. Thinning: The wire cutting process of 4H-SiC ingots leaves a large number of scratches and sub-surface damage on the wafer surface. Diamond grinding wheels are used for thinning. The main purpose is to remove these scratches and damage as much as possible.

7. Grinding: The grinding process is divided into rough grinding and fine grinding. The specific process is similar to that of thinning, but boron carbide or diamond abrasives with smaller particle sizes are used, and the removal rate is lower. It mainly removes the particles that cannot be removed in the thinning process. Injuries and newly introduced injuries.

8. Polishing: Polishing is the last step in 4H-SiC substrate processing, and is also divided into rough polishing and fine polishing. The surface of the wafer produces a soft oxide layer under the action of polishing fluid, and the oxide layer is removed under the mechanical action of aluminum oxide or silicon oxide abrasive particles. After this process is completed, there are basically no scratches and sub-surface damage on the surface of the substrate, and it has extremely low surface roughness. It is a key process to achieve an ultra-smooth and damage-free surface of the 4H-SiC substrate.

9. Cleaning: Remove particles, metals, oxide films, organic matter and other pollutants left in the processing process.