Process optimization of silicon carbide (SiC) substrates and corresponding polishing materials

Process optimization of silicon carbide (SiC) substrates and corresponding polishing materials

2021-03-01 16:38:44 30

Silicon carbide (SiC), as the third-generation bandwidth semiconductor material, is also the most mature third-generation semiconductor material.

With excellent properties of thermal, mechanical, chemical, and electrical, it is not only one of the best materials for making high-temperature, high-frequency, and high-power electronic devices, 

but also can be used as a substrate material based on GaN blue light-emitting diodes, which can be widely used in the fields of power electronics, microwave devices, and LED optoelectronics.


In terms of material performance, silicon carbide is very superior, its bandwidth is 3 times that of silicon,

saturation electron drift rate is 2 times higher than that of silicon, 

critical breakdown electric field is 10 times higher than that of silicon, and 5 times higher than that of GaAs, 

while thermal conductivity is 20 times higher than that of sapphire and 10 times higher than that of GaAs, 

as well as its chemical stability, is very good.

In addition, from the structure comparison, sapphire is not a semiconductor but an insulator, it can only do single-sided electrodes; however, silicon carbide is a conductive semiconductor, it can do vertical structure. 

The thermal conductivity of silicon carbide substrate is more than 10 times higher than that of sapphire. 

L-shaped is using for silicon carbide substrate equipped the electrodes of the chip, and the two electrodes are distributed on the surface and bottom of the device, so the heat generated can be directly exported through the electrodes.

At the same time, this substrate does not need a current diffusion layer, so the light will not be absorbed by the material of the current diffusion layer, which in turn improves the light output efficiency.


As the Mohs hardness of silicon carbide itself is relatively large, between 9.2-9.3, which determines its fine processing is very tedious and difficult.

Due to the efficiency is too low, eventually, leading to capacity production is seriously inadequate, which can not be large-scale mass production. 

At present, the processing of silicon carbide wafers generally uses a diamond grinding solution with higher Moh's hardness and a faster rate to grind to reach a certain thickness. 

Finally fine polish to the required surface condition with traditional CMP polishing solution.


However, the current process of silicon carbide substrate is long and complicated, resulting in low efficiency and unable to meet the needs of the downstream market.

In view of this, GRISH has optimized the polishing process of silicon carbide (SiC) substrates and developed polishing materials.


The test machine used for polishing is an ordinary polishing machine


Silicon carbide (SiC) substrate polishing process: rough polishing test conditions and parameter settings:

Polishing object: 4 inch 4H SiC substrate film * 3 pcs * 4 Head (film thickness of about 470μm) polishing pad: special polyurethane rough polishing pad

Rough polishing slurry: GRISH compound rough polishing slurry

Adhesion method: Wax paste


The optimized polishing process for silicon carbide (SiC) substrates:

It mainly involves a rough polishing process and materials (GRISH compound rough polishing solution) as well as fine polishing materials (CMP polishing solution).The time of finishing after rough polishing is greatly reduced.



The main advantages of the optimized polishing process for silicon carbide (SiC) substrates:

The advantages of the optimized process conditions simply focus on the second rough polishing process, 

which consists of a rough polishing solution (GRISH compound rough polishing solution) matched with the corresponding rough polishing pad having a faster polishing rate, and crucially, a smaller surface roughness, 

which greatly reduces the pressure of the fine polishing process. 

The fine polishing solution is designed for silicon carbide materials, and also has a higher polishing rate, improving the surface quality of the product. 

In short, the overall process can reduce the current procedure of silicon carbide substrates and improve production efficiency.


Polishing rate data:

Rough polishing rateFine polishing rate
Si sideC sideSi sideC side
12.23μm/h14.57μm/h2.02μm/h1.89μm/h


Measurement points:

AFM test (surface roughness Ra):

CANDELA test after cleaning:

Summary:

The optimized process and materials are much more efficient for processing silicon carbide (SiC) 

Roug & Fine Polishing Slurry

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