GB/T 40279-2021 in English

Analysis of the core content of the standard

This standard specifies the methodology system for testing the thickness of silicon dioxide film and polysilicon film on the surface of silicon wafers using the optical reflection method. The technical principle is based on the Fresnel interference effect: when the incident light is reflected at the upper and lower interfaces of the film, the optical path difference between the two reflected light beams causes interference. The thickness is calculated by analyzing the relationship between the wavelength and the refractive index of the extreme points of the reflection spectrum.

Key Technical Parameters

Key Points for Test Interference Control

Instrument system configuration

The standard requires that the test system include: deuterium tungsten lamp light source (190-1050nm), spectrometer, fiber optic probe and anti-vibration sample table. Key indicators:

• Wavelength resolution: ≤1nm
• Spot diameter: 50-200μm
• Repeatability error: ＜0.3%

Implementation suggestions

1. Calibration strategy: Special calibration pieces should be used for different materials/thickness ranges, such as 300nm silicon dioxide film, which requires independent calibration

2. Data processing: It is recommended to use the least squares fitting method to optimize thickness calculation, which is 40% more accurate than manual illustration

3. Abnormal handling: When the fitting curve R² is <0.95, it is necessary to check the sample surface contamination or the optical system alignment