High precision Resistivity Measurement of thin epitaxial layers and substrates
Aim
Measuring the resistivity of epitaxial layers on highly doped semiconductors is a huge challenge, but crucial for several reasons:
Material quality assessment, as an insight in the structural and electronic quality
Doping density verification
Device performance prediction
Extraction of material parameters as carrier concentration
Process development and simulation of doping models
Detection of contaminations, process drift and inhomogeneities and defects
Hence the availability of such a measurement with precision and reproducibility is critical for advanced semiconductor applications. So far only destructive methods with no or low spatial resolution as Mercury CV are available.
Application example
Figure 1 shows an exemplary mapping of the doping density of an 4 inch, highly doped 4H-SiC substrate with a 11 µm thick epitaxial layer. The growth facet in the substrate can be clearly detected as well as the radial gradient in the doping of the epitaxial layer. The edge exclusion is appr. 3 mm and a reproducibility of better than 99 % is reached.
![Figure 1: Example of a doping density map of a 350 µm thick, highly doped SiC substrate (right) with clearly observable growth facet and a 11 µm thick epitaxial layer (left) [1]](/fileadmin/_processed_/3/3/csm_THZ_Time-Domain_spectroscopy_Figure_1_left_1a0353c7d6.png)
Figure 1: Example of a doping density map of a 350 µm thick, highly doped SiC substrate (right) with clearly observable growth facet and a 11 µm thick epitaxial layer (left) [1]
A comparison with mercury CV measurements shows a very good agreement (Figure 2). The deviation is within 0.56 %.
![Figure 2: comparison of a linescan through the center of the wafer with mercury CV measurements [1]](/fileadmin/_processed_/9/4/csm_THZ_Time-Domain_spectroscopy_Figure_2_left_d28861ed19.png)
Figure 2: comparison of a linescan through the center of the wafer with mercury CV measurements [1]
THZmap
Contactless doping-density mapping for epitaxial layers on highly doped semiconductors
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Related Materials: Si, SiC, and more
Related Solutions and Industries: Epitaxial Layers & Thin Films