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 tips of the 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 $\mu$m wide trench is etched deeper than approximately 18 $\mu$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.

Comparison of 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