This machine has a micro needle on the tip of a cantilever beam. The needle is used to map the surface of the wafer. It can tell if the surface varies on a micro scale. This is important when the entire circuit is only a few microns long.
A diamond stylus is moved vertically in contact with a sample and then moved laterally across the sample for a specified distance and specified contact force. A profilometer can measure small surface variations in vertical stylus displacement as a function of position. A typical profilometer can measure small vertical features ranging in height from 10 nanometres to 1 millimetre. The height position of the diamond stylus generates an analog signal which is converted into a digital signal stored, analyzed and displayed. The radius of diamond stylus ranges from 20 nanometres to 25 ĂŽÂĽm, and the horizontal resolution is controlled by the scan speed and data signal sampling rate. The stylus tracking force can range from less than 1 to 50 milligrams.
Advantages of contact profilometers:
- Acceptance: Most of the world’s surface finish standards are written for contact profilometers. To follow the prescribed methodology, this type of Profilometer is often required. Surface Independence: Because the stylus is in contact with the surface, this method is not sensitive to surface reflectance or color. Also, contacting the surface is often an advantage in dirty environments where non-contact methods can end up measuring surface contaminants instead of the surface itself.
- Resolution: The stylus tip radius can be as small as 20 nanometres, significantly better than white-light optical profiling.
- Direct Technique: No modeling required.