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1. FZ Etching Wafers Specifications
2. CZ Etching Wafers Specifications
3. About the Etched Wafer Process
The existing polycrystalline silicon wafers are cut into pieces of polycrystalline silicon square wafers by a cuboid crystal ingot in a multi-line cutting saw. Since the slicing is made by the steel wire being cut into silicon wafers repeatedly under the action of emery solution, the emery hardness is very high, which will bring certain mechanical damage to the silicon wafer surface. If the damage is not removed, it will affect the fill factor of the devices.
Silicon wafer etching refers to the use of sodium hydroxide to corrode polysilicon to remove the surface damage layer produced by the multi-wire saw slicing of the silicon wafer. At the same time, the anisotropy of sodium hydroxide on silicon corrosion is used to strive for a surface texture with a lower reflectivity.
Comparison of the Acid Etching and Alkali Etching Process of Silicon Wafer
|パラメータ||Acid Etching Process||Alkali Etching Process|
|Heat Corrosion Reaction||Exothermic||Endothermic|
|Surface Flatness(STIR/TIR/TTV)||Need to rely on the rotation of the wafer and a special fixture. Improve the surface flatness by fully mixing the corrosive liquid through gas, special mechanisms and technological means.||A certain surface flatness can be achieved without special mechanism.|
|Surface Roughness After Etching（Ra)||The etched silicon wafer surface is smaller than the alkaline etching process and is related to the original damage of the wafer.||The etched silicon wafer surface is larger than the acid etching process and is related to the original damage degree of the wafer.|
|Residual Particles on Wafer Surface||The particles that are already on the surface of the wafer are difficult to remove, and the low surface roughness is not easy to adsorb particles.||The particles that have existed on the surface of the wafer are easy to remove, and the poor surface roughness is easy to absorb the particles.|
|Metal Pollution Degree(Cu/Ni)||The purity of the corrosive liquid is relatively high, the corrosion temperature is relatively low, and the degree of metal diffusion is small.||The purity of the corrosive liquid is relatively poor, the corrosion temperature is high, the metal diffusion is large, and the (111) crystal orientation is more serious than the (100) crystal orientation.|
|Surface Etching Spots Remaining Prints||The transfer time of the wafer from the etching solution to the water must be less than 0.6s to effectively prevent the occurrence of spots. The wafers with lower resistivity are more likely to produce spots.||The transfer time of the wafer from the etching solution to the water must be less than 2s to effectively prevent the occurrence of spots, which has nothing to do with the resistivity of the wafer.|
|Service Life of the Corrosive Tank||shorter||longer|
|Processing Cost||The chemical reagents used are about 2 times more expensive than the chemical reagents used for alkali etching.||The chemical reagents used are cheaper.|
|Environmental Protection Treatment||Environmental protection treatment is relatively complicated.||Environmental treatment is relatively easy.|
There are two basic silicon wafer etching methods in semiconductor manufacturing: dry etching and wet etching.
Dry etching silicon wafer is to expose the surface of the silicon wafer to the plasma generated in the gaseous state. The plasma passes through the window opened in the photoresist, and physically or chemically reacts with the silicon wafer, thereby removing the exposed surface material. This is the plasma etching of wafer. Dry etching is the most important method for etching devices at sub-micron size.
In wet etching, liquid chemical reagents (such as acids, alkalis, solvents, etc.) chemically remove the material on the surface of the silicon wafer. Wet etching is generally only used for larger sizes (greater than 3 microns). Wet etching is still for etching epitaxial wafer on the silicon substrate or to remove residues after dry etching.
4. Basic Etching Wafer Process Requirements:
An ideal etching in wafer fabrication must have the following characteristics:
- Anisotropic etching: only vertical etching, no lateral undercutting. Only in this way can it be ensured that the exact same geometric pattern as that on the resist is copied on the etched film;
- Good etching selectivity: for the resist used as a mask and another layer below, the etching rate of the film or material is much lower than the etching rate of the film to be etched, which ensure the effectiveness of resist masking during the wafer etching procedure, and prevent damage to other materials under the film due to over-etching;
- Due to the large processing batch, low cost, and small environmental pollution, the wafer etching mechanism is suitable for industrial production.