CN-122015671-A - Film thickness measuring method and device based on spectrum confocal

CN122015671ACN 122015671 ACN122015671 ACN 122015671ACN-122015671-A

Abstract

The invention relates to the technical field of high-precision measurement and discloses a film thickness measurement method and device based on spectrum confocal, wherein the method comprises the steps of obtaining a temperature parameter at the current moment, a focusing wavelength of the upper surface of a measured film and an initial focusing position; calculating the focusing position of the upper surface of the measured film according to the focusing wavelength to obtain the focusing position; calculating a focus deviation amount caused by temperature change according to the focus wavelength and the temperature parameter; the invention improves the accuracy of film thickness measurement.

Inventors

SUN XINYU
MENG WEITAO
KOU MINGHU

Assignees

北京特思迪半导体设备有限公司

Dates

Publication Date: 20260512
Application Date: 20260313

Claims (10)

1. A method for measuring film thickness based on spectral confocal, the method comprising: Acquiring a temperature parameter at the current moment, a focusing wavelength of the upper surface of the measured film and an initial focusing position; Calculating the focusing position of the upper surface of the measured film according to the focusing wavelength to obtain the focusing position; calculating a focus deviation amount caused by temperature change according to the focus wavelength and the temperature parameter; correcting the focusing position according to the focusing deviation amount to obtain an actual focusing position at the current moment; And calculating the film thickness according to the actual focusing position and the initial focusing position to obtain the measured film thickness at the current moment.
2. The method of claim 1, wherein the temperature parameter comprises an ambient temperature, the ambient temperature being an ambient temperature of a spectrally confocal film thickness measurement device at a current time; The calculating of the focus bias amount due to the temperature change based on the focus wavelength and the temperature parameter includes: calculating the refractive index variation of a lens in the spectral confocal thin film thickness measuring device caused by temperature according to the ambient temperature and the focusing wavelength; calculating a single lens power variation according to the refractive index variation; Calculating a total power variation of the plurality of lenses from the single lens power variation; and calculating a focusing position variation according to the total focal power variation to obtain the focusing deviation.
3. The method according to claim 2, wherein calculating the temperature-induced refractive index variation of the lens in the spectrally confocal thin film thickness measurement device according to the ambient temperature and the focus wavelength includes: acquiring an initial environmental temperature before thickness measurement of the measured film; Calculating a real-time temperature variation according to the ambient temperature and the initial ambient temperature; And calculating the refractive index variation of the lens of the spectral confocal thin film thickness measuring device caused by temperature according to the real-time temperature variation and the focusing wavelength.
4. The method of claim 1, wherein the temperature parameter comprises a light source temperature; The calculating of the focus bias amount due to the temperature change based on the focus wavelength and the temperature parameter includes: determining a drift rate of the focus wavelength with temperature rise according to the light source temperature; and calculating the focus wavelength deviation according to the drift rate and the time length from the measurement start to the current moment to obtain the focus deviation.
5. The method of claim 4, wherein said determining a drift rate of said focused wavelength with increasing temperature from said light source temperature comprises: acquiring a change function of the focusing wavelength along with the temperature change; And calculating the drift rate of the focusing wavelength along with the temperature rise according to the change function and the light source temperature.
6. The method of claim 4, wherein said correcting said focal position based on said amount of focal offset to obtain an actual focal position at a current time comprises: performing compensation calculation on the focusing wavelength according to the focusing wavelength deviation amount to obtain an actual focusing wavelength; calculating the instantaneous slope of the current moment according to the calibration relation function of the focusing wavelength and the pre-constructed focusing position; And calculating a focusing position according to the actual focusing wavelength and the instantaneous slope to obtain the actual focusing position at the current moment.
7. The method of claim 6, wherein the compensation calculation is performed for the focused wavelength using: , Wherein, the Representing the actual focal wavelength in question, Representing the wavelength of the light to be focused, Indicating the rate of said drift-off, Representing the duration of the measurement from the start to the current moment.
8. The method of claim 6, wherein calculating the instantaneous slope at the current time from the calibrated function of the focal wavelength and the pre-constructed focal position comprises: Obtaining a calibration relation function of a pre-constructed focusing position, and conducting derivation to obtain a slope function relation; And calculating the focusing wavelength by using the slope function relation to obtain the instantaneous slope at the current moment.
9. The method according to claim 6, characterized in that the actual focus position at the current moment is calculated by: , Wherein, the Representing the actual focal position in question, Representing the said instantaneous slope of the slope, Is constant.
10. A film thickness measuring apparatus based on spectral confocal, comprising a processor and a memory connected to the processor, wherein the memory stores instructions executable by the processor to cause the processor to perform the film thickness measuring method based on spectral confocal according to any one of claims 1 to 9.

Description

Film thickness measuring method and device based on spectrum confocal Technical Field The invention relates to the technical field of high-precision measurement, in particular to a film thickness measurement method and device based on spectrum confocal. Background The spectral confocal technology is widely applied to multiple fields by virtue of generating a continuous focus on an optical axis by using a broadband light source. Based on the chromatic aberration principle, the accurate measurement of the film thickness is realized through the correlation between the surface position of the film to be measured and the peak wavelength of the continuous focus of the reflection spectrum. In the actual measurement process, the temperature change of the environment and the workpiece can directly influence the final thickness measurement precision and accuracy. To cope with this problem, the prior art mainly uses temperature compensation or calibration techniques to reduce the effect of temperature on the measurement results. However, the prior art is highly dependent on early modeling and calibration of specific material characteristics and specific working conditions, and has serious shortages of universality, which results in failure to provide stable and reliable real-time measurement results in the face of unknown materials or complex and variable temperature environments, and poor accuracy of film thickness. Disclosure of Invention In view of the above, the present invention provides a method and apparatus for measuring film thickness based on spectrum confocal, so as to solve the problem of poor film thickness measurement accuracy. The invention provides a film thickness measuring method based on spectrum confocal, which comprises the steps of obtaining a temperature parameter at the current moment, a focusing wavelength and an initial focusing position of the upper surface of a measured film, calculating the focusing position of the upper surface of the measured film according to the focusing wavelength to obtain the focusing position, calculating the focusing deviation amount caused by temperature change according to the focusing wavelength and the temperature parameter, correcting the focusing position according to the focusing deviation amount to obtain an actual focusing position at the current moment, and calculating the film thickness according to the actual focusing position and the initial focusing position to obtain the measured film thickness at the current moment. In an alternative embodiment, the temperature parameter comprises an ambient temperature, the ambient temperature is the ambient temperature of the spectral confocal thin film thickness measuring device at the current moment, the focusing deviation amount caused by temperature change is calculated according to the focusing wavelength and the temperature parameter, the method comprises the steps of calculating refractive index change amount of a lens in the spectral confocal thin film thickness measuring device caused by temperature according to the ambient temperature and the focusing wavelength, calculating single lens focal power change amount according to the refractive index change amount, calculating total focal power change amounts of a plurality of lenses according to the single lens focal power change amount, and calculating focusing position change amount according to the total focal power change amount to obtain the focusing deviation amount. In an alternative embodiment, calculating the refractive index change of the lens of the spectral confocal thin film thickness measuring device caused by temperature according to the ambient temperature and the focusing wavelength comprises obtaining the initial ambient temperature before the thickness of the measured thin film is measured, calculating the real-time temperature change according to the ambient temperature and the initial ambient temperature, and calculating the refractive index change of the lens of the spectral confocal thin film thickness measuring device caused by temperature according to the real-time temperature change and the focusing wavelength. In an alternative embodiment, the temperature parameter comprises a light source temperature, calculating a focus offset caused by temperature change according to the focus wavelength and the temperature parameter comprises determining a drift rate of the focus wavelength along with temperature rise according to the light source temperature, and calculating the focus wavelength offset according to the drift rate and a time period from the beginning of measurement to the current moment to obtain the focus offset. In an alternative embodiment, determining the drift rate of the focus wavelength with temperature increase based on the light source temperature includes obtaining a variation function of the focus wavelength with temperature change, and calculating the drift rate of the focus wavelength with temperature increase bas