GB/T 14847-2025Test method for thickness of lightly doped silicon epitaxial layers on heavily doped silicon substrates - Infrared reflectance method (English PDF)

1 Scope

This document describes a method for measuring the thickness of a lightly doped silicon epitaxial layer on a heavily doped substrate using infrared reflection.

This document applies to silicon epitaxy with a thickness greater than 0.5 µm prepared on substrates with resistivity of 0.0006 ohm·cm to 0.025 ohm·cm.

Layer thickness testing.

2 Normative references

The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.

For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies.

This document.

GB/T 6379.2-2004 Accuracy (Correctness and Precision) of Measurement Methods and Results - Part 2.Determining Standard Measurement Methods

Basic methods of repeatability and reproducibility

GB/T 14264 Semiconductor Materials Terminology

GB/T 25915.1-2021 Cleanrooms and related controlled environments - Part 1.Classification of air cleanliness levels by particle concentration

3 Terms and Definitions

The terms and definitions defined in GB/T 14264 and the following terms and definitions apply to this document.

4 Method Principles

Infrared incident light, upon contact with the surface of the epitaxial layer, penetrates the epitaxial layer and reaches the substrate, where it is reflected and refracted at the upper and lower interfaces of the epitaxial layer, respectively.

The total reflected light is the superposition of these two reflected parts. Due to the wave nature of light, the phases of these two reflected parts may be constructive or interfering.

The phase relationship is destructive, while the optical path difference between the two parts depends on the optical path difference. The optical path difference is determined by the epitaxial layer thickness, the optical constants of the epitaxial layer and the substrate, and the wavelet velocity of light.

The incident angle of long- and infrared light on the epitaxial layer and the refractive index of the epitaxial layer determine the incident angle.

When the optical path difference is an even multiple of half the wavelength, the two sets of reflected light are in phase, resulting in constructive interference, which means that the maximum value of the reflection spectrum is observed.

Peak position; conversely, when the optical path difference is an odd multiple of half the wavelength, the two sets of reflected light are out of phase, resulting in destructive interference, i.e., exhibiting a minimum in the reflection spectrum.

Value trough position.

The interferogram was recorded by the instrument detector and converted into a reflectance spectrum, and the sample reflectance spectrum showed continuous maxima and minima of interference fringes.

Spectral phenomena are determined based on the extreme wavenumbers of interference fringes in the reflection spectrum, the optical constants of the epitaxial layer and substrate, and the incident infrared beam on the sample.

The thickness of the epitaxial layer can be calculated by using the angle. […]