Stylus profilometry (contact profilometry) brings a stylus tip into direct contact with a sample in order to trace the topography of the surface. This technique is often used to measure step heights and feature sizes for samples which have etched patterns on them.
|Other Names||Contact profilometry|
|Equipment||Dektak XT, Dektak 6M|
Latest model Dektak profiler located in the main cleanroom. This tool has a fully automated stage and is capable of 3D mapping and scanning the full diameter of a 150 mm wafer.
Older model Dektak profiler located in the ROBIN lab (Wet Chemistry).
Method of operation
- The profilometer brings a small stylus tip into contact with the sample surface. For the stylus profilometers at LNF, we have 25 μm diameter diamond tip styli.
- The tool maintains a constant stylus tip contact force as the stage moves the sample underneath the stylus.
- Deflection of the stylus tip is measured by a sensor head (LVDT - linear variable differential transformer)
- Sample surface heights are then plotted versus lateral position to be analyzed.
Stylus profilometry is often used for measuring step heights and feature sizes for samples that have been patterned and etched. The physical dimensions of the stylus cause limitations in what can be measured with this method.
- The stylus must be able to physically climb up a step feature's height. Our stylus profilometers are only able to measure step heights up to 150 μm.
- The aspect ratio (feature depth divided by width) can not be greater than ~1. The maximum aspect ratio that can be measured is dependent on the width of trench features. The plot below shows this dependence. At 25um trench width, the aspect ratio of the feature must be less than 0.5.
- For step heights taller than 150 μm or for high aspect ratio features, one of the optical 3D profilers (Zygo or LEXT) need to be used.