Specific Process Knowledge/Etch/Wet Silicon Nitride Etch: Difference between revisions
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[[Image:Wet_nitride_etch.JPG|300x300px|thumb|Wet nitride etch: positioned in cleanroom 4]] | [[Image:Wet_nitride_etch.JPG|300x300px|thumb|Wet nitride etch: positioned in cleanroom 4]] | ||
Wet Etching of silicon nitride is done in a dedicated laminar flow bench with an integrated quartz tank (Tiger Tank - TT-4). The quartz tank can take up to one 6" wafer carrier. The flow bench is placed in cleanroom 4. The process is mainly used to strip silicon nitride (maskless), but can also be used for masked etching of silicon nitride using some kind of silicon oxide as etch mask. However, the wet silicon nitride etch is isotropic meaning that the under-etching (etch-bias) at least amounts to the thickness of the silicon nitride layer. | Wet Etching of silicon nitride - stoichiometric and si-rich - is done in a dedicated laminar flow bench with an integrated quartz tank (Tiger Tank - TT-4). The quartz tank can take up to one 6" wafer carrier. The flow bench is placed in cleanroom 4. The process is mainly used to strip silicon nitride (maskless), but can also be used for masked etching of silicon nitride using some kind of silicon oxide as etch mask. However, the wet silicon nitride etch is isotropic meaning that the under-etching (etch-bias) at least amounts to the thickness of the silicon nitride layer. | ||
The etch solution is initially 85 wt% H<math>3</math>PO<math>4</math> which is heated up to the boiling temperature - ca. 157 <sup>o</sup>C. Water is allowed to boil off thus raising the concentration and the boiling temperature of the solution until a boiling temperature of 180 <sup>o</sup>C is reached. Thereafter, the wafers are submerged into the bath and the water-cooled lid is closed to maintain the concentration and the boiling temperature. In some cases a lower boiling temperature is chosen - typically 160 <sup>o</sup>C - which lowers the etch rate and improves the selectivity R<sub>Si<sub>3</sub>N<sub>4</sub></sub> / R<sub>SiO<sub>2</sub></sub> | The etch solution is initially 85 wt% H<math>3</math>PO<math>4</math> which is heated up to the boiling temperature - ca. 157 <sup>o</sup>C. Water is allowed to boil off thus raising the concentration and the boiling temperature of the solution until a boiling temperature of 180 <sup>o</sup>C is reached. Thereafter, the wafers are submerged into the bath and the water-cooled lid is closed to maintain the concentration and the boiling temperature. In some cases a lower boiling temperature is chosen - typically 160 <sup>o</sup>C - which lowers the etch rate and improves the selectivity R<sub>Si<sub>3</sub>N<sub>4</sub></sub> / R<sub>SiO<sub>2</sub></sub> | ||
Revision as of 10:48, 30 January 2008
Wet Silicon Nitride Etch
Wet Etching of silicon nitride - stoichiometric and si-rich - is done in a dedicated laminar flow bench with an integrated quartz tank (Tiger Tank - TT-4). The quartz tank can take up to one 6" wafer carrier. The flow bench is placed in cleanroom 4. The process is mainly used to strip silicon nitride (maskless), but can also be used for masked etching of silicon nitride using some kind of silicon oxide as etch mask. However, the wet silicon nitride etch is isotropic meaning that the under-etching (etch-bias) at least amounts to the thickness of the silicon nitride layer.
The etch solution is initially 85 wt% HFailed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 3} POFailed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle 4} which is heated up to the boiling temperature - ca. 157 oC. Water is allowed to boil off thus raising the concentration and the boiling temperature of the solution until a boiling temperature of 180 oC is reached. Thereafter, the wafers are submerged into the bath and the water-cooled lid is closed to maintain the concentration and the boiling temperature. In some cases a lower boiling temperature is chosen - typically 160 oC - which lowers the etch rate and improves the selectivity RSi3N4 / RSiO2
Nitride etch - key facts
| Nitride etch @ 180 oC | Nitride etch @ 160 oC | |
|---|---|---|
| General description |
Etch of silicon nitride |
Etch of pure Gold |
| Chemical solution | KJ:JFailed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle _2} :HFailed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle _2} O (100g:25g:500ml) | HCl:HNOFailed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle _3} (3:1) |
| Process temperature | 20 oC | 20 oC |
| Possible masking materials: |
Photoresist (1.5 µm AZ5214E) |
Photoresist (1.5 µm AZ5214E) |
| Etch rate |
~100 nm/min (Pure Al) |
~(??) nm/min |
| Batch size |
1-25 wafers at a time |
1-25 wafer at a time |
| Size of substrate |
2-6" wafers |
2-6" wafers |