Specific Process Knowledge/Characterization/Topographic measurement
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Topographic measurements are measurements were you can measure hight differences on your substrate. If you measure in many spots of the substrate you can get a topographic image of the substrate.
AT DANCHIP we have four systems for topographic measurement:
- Dektak (there are two systems) - Profiler for measuring micro structures
- Optical Profiler (Sensofar) - 3D Profiler for measuring micro structures
- Nanoman - AFM for measuring nano structures
High Aspect ratio structures
The fact that the tips of the Dektak profilers and the AFM are shaped like a cone with some tip angle causes a problem when characterizing high aspect ratio structures. For instance, if a 20 µm wide trench is etched deeper than approximately 18 µm, the tip of the Dektak will not be able to reach the bottom. The optical profiler uses a light beam that is focused through an objective. Therefore it is able to measure higher aspect ratios. The aspect ratio is limited by the posibility for the light to reach the bottom and get back to the detector. On some samples we have been able to measure aspect ratios above 1:10. Otherwise the solution is to cleave the sample along a line that is perpendicular to the trench and then inspect the profile in a scanning electron microscope or a microscope (for large structures).
Comparison of the two profilers and the AFM
| Dektak 8 stylus profiler | Dektak XTA_new stylus profiler | Optical Profiler (Sensofar) | Nanoman | |
|---|---|---|---|---|
| General description | Profiler for measuring micro structures. Can do wafer mapping and stress measurements. | Profiler for measuring micro structures. Can do wafer mapping and stress measurements. | 3D Profiler for measuring micro structures. Can do wafer mapping. | AFM for measuring nanostructures and surface roughness |
| Substrate size | up to 8" | up to 6" | Up to more than 6" | 6" or less |
| Max. scan range xy | Line scan x: 50µm to 200mm | Line scan x: 50µm to 55mm in one scan. Maximum scan lenght with stiching 200mm. | Depending on the objective:
|
90 µm square |
| Max. scan range z | 50Å to 1mm | 50Å to 1mm | Depending on the objective and Z resolution:
|
1 µm (can go up to 5 µm under special settings) |
| Resolution xy | down to 0.067 µm | down to 0.003 µm | Depending on the objective:
|
Depending on scan size and number of samples per line and number of lines - accuracy better than 2% |
| Resolution z | 1Å, 10Å, 40Å or 160Å | 1Å, 10Å, 80Å or 160Å | Depending on measuring methode:
|
<1Å - accuracy better than 2% |
| Max. scan depth [µm] (as a function of trench width W) | 1.2*(W[µm]-5µm) | 1.2*(W[µm]-5µm) | Depending on material and trench width:
|
~1:1 with standard cantilever. |
| Tip radius | 5 µm 45o cone | 5 µm 45o cone | No tip - using light
|
<12 nm on standard cantilever |
| Stress measurement | Can be done | Can be done | No stress calculation capability | Cannot be done |
| Surface roughness | Can be done on a line scan | Can be done on a line scan | Can be done on a line or an area | Can be done on a selected surface area |