GB/T 42905-2023 in English

1. Background and significance of the standard

National Standard of the People's Republic of China GB/T 42905-2023 "Infrared Reflection Method for Testing the Thickness of Silicon Carbide Epitaxial Layers" is a standard document proposed and managed by the National Technical Committee for Standardization of Semiconductor Equipment and Materials. This standard specifies the method for testing the thickness of silicon carbide epitaxial layers using infrared reflection method. It is applicable to the testing of the thickness of homogeneous silicon carbide epitaxial layers with a homogeneous doping concentration less than $1\times10^{16}~\mathrm{cm^{-3}}$ on silicon carbide substrates with an n-type doping concentration greater than $1\times10^{18}~\mathrm{cm^{-3}}$, and the test range is $3\mu\mathrm{m}{\sim}200\mu\mathrm{m}$.

2. Principle of the Method

Silicon Carbide Epitaxial Layer Thickness Tester measures by infrared reflection method. Its core principle is based on the difference in optical constants between the silicon carbide substrate and the epitaxial layer, which leads to the optical interference phenomenon of continuous maximum and minimum characteristic spectra in the reflection spectrum of the sample. By analyzing the extreme wave number of the interference fringes in the reflection spectrum, the optical constants of the epitaxial layer and the substrate, and the incident angle of the infrared beam on the sample, the corresponding epitaxial layer thickness can be calculated.

3. Interference factors and solutions

4. Instruments and test conditions

Fourier transform infrared spectrometer is the core equipment of this test method, and its wave number range is $360~\mathrm{cm}^{-1}{\sim}7800~\mathrm{cm}^{-1}$. It is recommended to use a reflection accessory with an incident angle of no more than $30^\circ$ and a rotatable sample stage to ensure accurate measurement.

5. Implementation suggestions

Laboratory test conditions:

• Temperature control: $(22\pm2)^{\circ}\mathrm{C}$.
• Humidity control: $(45\pm10)\%$.
• Sample preparation: Ensure that the sample surface is clean and the roughness is less than $5~\mathrm{nm}$.

Instrument calibration:

• Use a polystyrene film with a thickness of less than $50\mu\mathrm{m}$ as a standard for wavenumber calibration.
• Ensure that the deviation between the test value and the calibration value of the calibration piece is no more than $3\%$.