Specific Process Knowledge/Characterization/Topographic measurement
Topographic measurements are measurements were you can measure hight differences on your substrate. If you measure in many spots of you substrate you can get a topographic image of your substrate.
AT DANCHIP we have three systems for topographic measurement:
- Tencor - Profiler for measuring micro structures
- Dektak - Profiler for measuring micro structures
- Nanoman - AFM for measuring nano structures
High Aspect ratio structures
The fact that the tip is shaped like a cone with some tip angle causes a problem when characterizing high aspect ratio structures. For instance, if a 20 Failed 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 \mu} m wide trench is etched deeper than approximately 18 Failed 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 \mu} m, the tip of the Dektak will not be able to reach the bottom. In this case the only solution is to cleave the sample along a line that is perpendicular to the trench and then put it in a scanning electron microscope.
Comparing the two profilers and the AFM
| Tencor | Dektak | Nanoman | |
|---|---|---|---|
| General description | Profiler for measuring micro structures | Profiler for measuring micro structures. Can do wafer mapping and stress measurements. | AFM for measuring nanostructures and surface roughness |
| Substrate size | small pieces -> 4" | 2" -> 8" | 6" or less |
| Max. scan range xy | Line scan x: Full substrate size | Line scan x: 50µm to 200mm | 90 µm square |
| Max. scan range z | <100Å to~0.3mm | 50Å to 262µm | 1 µm (can go up to 5 µm under special settings) |
| Resolution xy | up to 5900 data points per profile | down to 0.067 µm | Depending on scan size and number of samples per line and number of lines - accuracy better than 2% |
| Resolution z | 1Å or 25Å | 1Å, 10Å or 20Å | <1Å - accuracy better than 2% |
| Max. scan depth [µm] (as a function of trench width W) | 0.87(W[µm]-5µm) | 1.2(W[µm]-5µm) | ~1 with standard cantilever. |
| Tip radius | 5 µm 60o cone | 5 µm 45o cone | <12 nm on standard cantilever |
| Stress measurement | Can be done | Can be done | Cannot be done |
| Surface roughness | Can be done on a line scan | Can be done on a line scan | Can be done on a selected surface area |