Handbook of Silicon Based MEMS Materials and Technologies

6.6. Metrology

A brief overview of metrology as it applies to epitaxial layers for measurements of thickness, resistivity and defect densities is provided in this section. For greater detail, please refer to Chapter 7 of reference [1] as well as Chapter 16 in Part III of this handbook.

6.6.1. Measurement of Si Epi Layer Thickness

Epitaxial thickness measurements are most often performed using the FTIR (Fourier Transform Infrared spectrometry) technique [16]. This method requires a structure where the epi layer has a relatively low doping concentration (N^dope < ∼10¹⁸ cm⁻³) and the region underlying the epi layer has a high doping concentration (N^dope>5 × 10¹⁸ cm⁻³). The refractive index change of Si at high doping concentrations provides the ...