CN-121986388-A - Plasma processing/controlling apparatus and plasma processing/controlling method

CN121986388ACN 121986388 ACN121986388 ACN 121986388ACN-121986388-A

Abstract

In the present invention, it is an object to estimate the thickness of a processing object with high accuracy even when a previously prepared spectrum pattern deviates from a spectrum pattern measured at the time of actual processing with respect to the processing object subjected to plasma etching processing. Accordingly, the plasma processing/control apparatus of the present invention compares a measured spectrum obtained by receiving reflected light of plasma from a processing chamber at any time during etching with an estimated spectrum obtained in advance in association with the thickness of the same processing object, calculates a spectral error between the measured spectrum and a plurality of estimated spectrums, and estimates the thickness of the processing object at any time using an estimated spectrum that takes at least a first minimum value and an estimated spectrum that takes a second minimum value of the plurality of spectral errors.

Inventors

Naga Mitsuru
SUWA YUJI
ETO SOICHIRO

Assignees

株式会社日立高新技术

Dates

Publication Date: 20260505
Application Date: 20240829

Claims (10)

1. A plasma processing/controlling apparatus etches a processing object disposed in a processing chamber to a predetermined thickness by using a plasma formed in the processing chamber in a vacuum vessel, The plasma processing/control device is characterized in that, Comparing a measured spectrum obtained by receiving reflected light of plasma from the processing chamber at any time during etching with an estimated spectrum obtained in advance in association with the thickness of the same processing object as the processing object, calculating a spectral error between the measured spectrum and a plurality of estimated spectrums, The plasma processing/controlling device includes a thickness estimating/determining unit that estimates the thickness of the processing object at any time using an estimation spectrum called a "first minimum spectrum" that is a first minimum value among the plurality of spectrum errors and an estimation spectrum called a "second minimum spectrum" that is a second minimum value.
2. The plasma processing/control apparatus as claimed in claim 1, wherein, The thickness estimating/determining unit estimates the thickness of the processing object at the arbitrary timing using a spectral error calculated between a synthesized spectrum obtained by synthesizing the first minimum spectrum and the second minimum spectrum in consideration of a mixing ratio and the measured spectrum.
3. The plasma processing/control apparatus as claimed in claim 1, wherein, An estimation spectrum called a "third minimum spectrum" which is a third minimum value among the plurality of spectrum errors is used, and an approximate curve automatically generated from at least the first to third minimum values and the thicknesses of the processing object corresponding to the first to third minimum spectra is used to estimate the thickness of the processing object at any time.
4. The plasma processing/control apparatus as claimed in claim 1, wherein, Using an estimation spectrum called a "third minimum spectrum" which is a third minimum value which is a further at least third minimum value among the plurality of spectrum errors, estimating the thickness of the processing object at any time by resampling processing based on at least the first to third minimum values and the thicknesses of the processing object corresponding to the first to third minimum spectra.
5. The plasma processing/control apparatus according to any one of claims 1 to 4, wherein, The spectral error is a value obtained by summing squares of differences in light intensities of the compared spectra with wavelengths.
6. A plasma processing/control method for etching a processing object disposed in a processing chamber to a predetermined thickness by using a plasma formed in the processing chamber in a vacuum vessel, In the thickness estimating/determining section, a measured spectrum obtained by receiving reflected light of plasma from the processing chamber at any time during etching is compared with an estimated spectrum of a processing object obtained in advance in association with the thickness of the same processing object as the processing object, a spectral error is calculated between the measured spectrum and a plurality of the estimated spectrums, The thickness of the processing object at any time is estimated using an estimation spectrum called a "first minimum spectrum" which is a first minimum value among the plurality of spectrum errors and an estimation spectrum called a "second minimum spectrum" which is a second minimum value.
7. The plasma processing/control method as claimed in claim 6, wherein, In the thickness estimating/determining unit, the thickness of the processing object at any time is estimated using a spectral error calculated between the measured spectrum and a synthesized spectrum synthesized from the first minimum spectrum and the second minimum spectrum in consideration of a mixing ratio.
8. The plasma processing/control method as claimed in claim 6, wherein, An estimation spectrum called a "third minimum spectrum" which is a third minimum value among the plurality of spectrum errors is used, and an approximate curve automatically generated from at least the first to third minimum values and the thicknesses of the processing object corresponding to the first to third minimum spectra is used to estimate the thickness of the processing object at any time.
9. The plasma processing/control method as claimed in claim 6, wherein, Using an estimation spectrum called a "third minimum spectrum" which is a third minimum value which is a further at least third minimum value among the plurality of spectrum errors, estimating the thickness of the processing object at any time by resampling processing based on at least the first to third minimum values and the thicknesses of the processing object corresponding to the first to third minimum spectra.
10. The plasma processing/control method according to any one of claims 6 to 9, wherein, The spectral error is a value obtained by summing squares of differences in light intensities of the compared spectra with wavelengths.

Description

Plasma processing/controlling apparatus and plasma processing/controlling method Technical Field The present invention relates to a plasma processing/control apparatus and a plasma processing/control method. Background In the manufacture of semiconductor devices, dry etching using plasma is widely used as a process for removing unnecessary portions. In the case where the processing shape and design are different in this etching process, the manufactured semiconductor cannot achieve desired performance, and therefore a process monitoring technique for monitoring/stabilizing the etching process is required. A process monitor that measures the thickness of a residual film and the depth of a pattern on a wafer by measuring the reflected light from the wafer during processing is called a film thickness/depth monitor, and is used for end point determination of etching processing, and the like. In patent document 1, in order to monitor the film thickness and depth in the etching process, a spectrometer is used to detect the spectrum of the plasma light reflected from the wafer surface of the etched process object. The detected spectrum data is compared with the principal component analysis data of spectrum data obtained in the previous etching by using a pattern recognition technique such as principal component analysis, and the end point of the plasma etching process is determined based on the current film thickness information obtained here. In patent document 2, standard deviation patterns corresponding to a plurality of thicknesses are prepared using wafers prepared in advance, and interference light obtained by etching a wafer to be processed is compared with the standard deviation patterns to calculate a deviation. The thickness of the film in the etching process is recorded based on the deviation, and the endpoint is determined when the etching amount is a predetermined etching amount. Further, in order to cope with the fluctuation of the interference light during etching, when the deviation does not satisfy a predetermined condition, the thickness of the film is corrected using regression line approximation or the like. Prior art literature Patent literature Patent document 1 Japanese patent laid-open No. 2001-244254 Patent document 2 Japanese patent laid-open No. 2007-234666 Disclosure of Invention Problems to be solved by the invention In recent years, with the development of miniaturization, new miniaturization processes of semiconductor devices have been increasing. Further, the improvement in performance by new materials and new structures is advanced. Therefore, development of mass production stabilization techniques for these new device manufacturing processes is necessary, and there is an increasing demand for highly accurate monitoring of film thickness/depth. However, patent document 1 and patent document 2 each disclose a method of monitoring the etching amount based on a comparison between a previously prepared spectrum pattern and a measured spectrum pattern of a wafer to be processed, and if the timing of detection of the spectrum is different, the spectrum does not completely coincide and the spectrum is deviated. Therefore, the calculated etching amount also deviates. Further, even if the etching conditions are the same, the etching process speed (etching rate) may vary due to some factors, and in this case, the spectrum shape may deviate for each etching time in the spectrum pattern prepared in advance and the measured spectrum pattern of the wafer to be processed, and as a result, the calculated etching amount may also vary. Accordingly, an object of the present invention is to provide a technique capable of estimating the thickness of a processing object with high accuracy and determining the end point of a process even when a spectrum pattern prepared in advance and a spectrum pattern measured at the time of actual processing deviate due to a difference in detection timing or the like, with respect to the processing object subjected to plasma etching processing. Means for solving the problems In order to solve the above problems, one of typical plasma processing/control apparatuses according to the present invention is a plasma processing/control apparatus for etching an object to be processed placed in a processing chamber to a predetermined thickness by using a plasma formed in the processing chamber in a vacuum chamber, wherein a measured spectrum obtained by receiving reflected light of the plasma from the processing chamber at any time during etching is compared with an estimation spectrum obtained in advance in association with the thickness of the same object to be processed, and a spectral error is calculated between the measured spectrum and a plurality of the estimation spectrums, and the apparatus includes a thickness estimation/determination unit for estimating the thickness of the object to be processed at any time by using an estimation spectrum (referred to as a "first mi