Specific Process Knowledge/Etch/ICP Metal Etcher/silicon/nano
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Etching of nanostructures in silicon
A series of experiments with etching nanostructures in silicon has been carried out. The common process parameters are:
- Substrates
- A pattern containing 30 nm, 60 nm, 90 nm, 120 nm and 150 nm wide lines has been transferred using E-beam lithography onto three separate batches of 2" wafers (with three different thicknesses of zep resist). In order to make sure that the narrowest features are fully opened they are intentionally over-exposed in the E-beam writer (400 muC/cm2) causing the lines to widen. The resist profiles of the three batches are:
- The 180 nm zep resist profiles (Wafer WF_2B1_feb06_2011)
- The 340 nm zep resist profiles (Wafer WF_2C1_feb2011)
- The 211 nm zep resist profiles (Wafer WF_2E02_mar23_2011)
The exposed area is very small. The 211 nm batch has the same lines distributed in a different way that allows you monitor the progress of the etch in three different durations by cleaving off a piece of the wafer 3 times. After E-beam exposure the wafers have been developed: N50 for 2 minutes followed by 30 seconds of IPA.
- Substrate mounting
- The 2" wafers are mounted with crystalbond in the center of 4" Si carriers that have an oxide layer facing the plasma.
- Conditioning the process chamber
| Recipe Sinano | 3.0 | 3.1 | 3.2 | 3.3 | 3.4 | 4.0 | 3.5 | 3.6 | 3.3 | 3.7 | 3.31 | 3.31 | 3.32 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cl2 (sccm) | 0 | 0 | 0 | 0 | 0 | 20 | 15 | 15 | 0 | 0 | 0 | 0 | 0 |
| BCl3 (sccm) | 5 | 3 | 5 | 5 | 5 | 0 | 5 | 5 | 5 | 5 | 5 | 5 | 5 |
| HBr (sccm) | 15 | 17 | 15 | 15 | 15 | 0 | 0 | 0 | 15 | 15 | 15 | 15 | 15 |
| Coil power (W) | 900 L | 900 F | 900 F | 900 F | 900 F | 900 L | 900 L | 900 F | 900 F | 900 L | 900 F | 900 F | 900 F |
| Platen power (W) | 50 | 50 | 60 | 75 | 90 | 60 | 60 | 60 | 75 | 60 | 75 | 75 | 30 |
| Pressure (mtorr) | 2 | 2 | 2 | 2 | 2 | 2 | 5 | 10 | 2 | 10 | 2 | 2 | 2 |
| Temperature (oC) | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 20 | 50 | 50 | 50 | 50 |
| Spacers (mm) | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 30 | 100 |
| Process time (s) | 150 | 180 | 120 | 180 | 120 | 90 | 120 | 180 | 300 | 180 | 180 | 180 | 180 |
| Etch rates (nm/min) | |||||||||||||
| Averages | 311 | 104 | 92 | 105 | 116 | 169 | 108 | 79 | 101 | 66 | 91 | 98 | 59 |
| Std. Dev | 44 | 15 | 15 | 21 | 22 | 9 | 11 | 31 | 29 | 4 | 28 | 18 | 12 |
| Zep etch rate (nm/min) | |||||||||||||
| 30 | 40 | 51 | 67 | 45 | 59 | 53 | 36 | 19 | |||||
| Sidewall angle (degrees) | |||||||||||||
| Averages | 82 | 82 | 82 | 82 | 82 | 84 | 81 | 83 | 83 | 85 | 80 | 83 | 79 |
| Std. Dev | 2 | 2 | 1 | 1 | 1 | 1 | 1 | 2 | 2 | 1 | 3 | 2 | 2 |
| CD loss (nm pr edge) | |||||||||||||
| Averages | 65 | -11 | -15 | -2 | -11 | 67 | 63 | -29 | -5 | -29 | 10 | -14 | -17 |
| Std. Dev | 30 | 5 | 2 | 4 | 3 | 29 | 27 | 6 | 5 | 8 | 7 | 8 | 10 |
| Bowing (nm) | |||||||||||||
| Averages | 31 | 31 | 15 | 6 | 5 | 22 | 12 | 15 | 28 | 13 | 25 | 1 | -2 |
| Std. Dev | 6 | 7 | 3 | 6 | 4 | 5 | 2 | 6 | 9 | 7 | 5 | 2 | 2 |
| Bottom curvature | |||||||||||||
| Averages | -9 | -6 | -9 | -11 | -9 | 9 | -4 | -8 | -24 | -2 | -9 | -13 | -10 |
| Std. Dev | 22 | 19 | 19 | 11 | 7 | 17 | 15 | 15 | 12 | 15 | 13 | 17 | 18 |