Sputter Depth Profiling by SIMS; Calibration of SIMS Depth Scale Using Multi-layer Reference Materials

In-depth distribution of doping elements in shallow depth region is an important role of secondary ion mass spectrometry (SIMS) for the development of next-generation semiconductor devices. KRISS has developed two types of multi-layer reference materials by ion beam sputter deposition. A multiple delta-layer reference material where the layers of one element are very thin can be used to evaluate SIMS depth resolution, to calibrate the depth scale and to monitor sputtering uniformity. The scale of a stylus profilometer can be also calibrated by comparison of the crater depths measured by a stylus profilometer and the certified thickness of the reference material measured by high resolution TEM. In a Korean round robin test for the scale calibration of a stylus profilometer using a Si/Ge multiple delta-layer (MDL), the average slope of the linear fitting results between the measured depth and the nominal depth was 0.989 with the standard deviation of 0.05. In depth scale calibration using a Si/Ge multi-layer reference material showed that the determination of interface position is very important to calibrate the sputtering rates of two different constituent materials. Especially, it is critical to define the positions of interfaces in a SIMS depth profile with interface artifacts.