GB/T 40279-2021Test method for thickness of films on silicon wafer surface—Optical reflection method (English PDF)

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for Standardization Work Part 1: Structure and Drafting Rules of Standardization Documents" Drafting.

This document is composed of the National Semiconductor Equipment and Material Standardization Technical Committee (SAC/TC203) and the National Semiconductor Equipment and Material Standards The material subcommittee of the Chemical Technology Committee (SAC/TC203/SC2) jointly proposed and managed.

1 Scope

This document specifies the method for measuring the thickness of silicon dioxide film and polysilicon film on the surface of silicon wafers using the optical reflection method.

This document is suitable for testing the thickness of silicon dioxide films and polysilicon films grown on the surface of silicon wafers, as well as all smooth, transparent Or semi-transparent, low absorption coefficient film thickness testing, such as surface films such as amorphous silicon, silicon nitride, diamond-like carbon coating, photoresist, etc.

2 Normative references

The contents of the following documents constitute the indispensable clauses of this document through normative references in the text. Among them, dated quotations Only the version corresponding to that date is applicable to this document; for undated reference documents, the latest version (including all amendments) is applicable to this document.

GB/T 14264 Terminology of Semiconductor Materials

3 Terms and definitions

The terms and definitions defined in GB/T 14264 are applicable to this document.

4 Principles of the method

After the incident light touches the surface of the film, it penetrates the film to reach the substrate, and is reflected and refracted at the upper and lower interfaces of the film. The total reflected light is The superposition of these two parts of reflected light. Because of the volatility of light, the phases of the two parts of the reflected light may interfere constructively (intensity addition) or interfere with each other. Cancellation (intensity subtraction), and the phase relationship depends on the optical path difference between the two parts of the reflection. The optical path is determined by the thickness of the film, the optical constant, the wavelength of the light, and the reflection Determined by emissivity and refractive index.

When the optical path in the film is equal to an integer multiple of the light wavelength, the two groups of reflected light have the same phase, and the interference is constructive, that is, the peak position of the test pattern is presented.

On the contrary, when the optical path in the film is one-half of the integral multiple of the wavelength, the two sets of reflected light have opposite phases, and the interference cancels, that is, the test pattern is displayed. The trough position.

The reflection signals at different wavelengths are collected by a spectrometer, and the reflection interference spectrum curves of the upper and lower surfaces of the film are obtained. Use manual illustration or With the help of the instrument's own software, the curve fitting is completed and the extreme points are selected for calculation, and finally the thickness of the film is obtained.

5 Disturbing factors

5.1 Strong light, magnetic field, temperature, humidity and other fluctuations in the environment will affect the test results.

5.2 The surface roughness of the sample will also affect the test results. The direct test on the surface of the non-mirror sample will cause the test due to the uneven interface. The error of the result increases, and even produces wrong results. Mirror polishing treatment on the sample surface can solve the above problems and achieve a good measurement. Test results, for example, to test the silicon dioxide film on the surface of the silicon corrosion wafer, usually a silicon single crystal polished wafer is used as a companion wafer, and the test is produced on the polished surface. The long silicon dioxide film thickness is completed. At the same time, ensure that the surface of the sample is clean, so as not to affect the optical path difference.

5.3 The film on the sample surface and the material used as the sample substrate sometimes cannot fit the ideal curve, and it is necessary to add a layer between the two.