DocumentCode :
1289966
Title :
Spatial characterization of wafer state using principal component analysis of optical emission spectra in plasma etch
Author :
White, David A. ; Boning, Duane ; Butler, Stephanie Watts ; Barna, Gabriel G.
Author_Institution :
Microsystems Technol. Lab., MIT, Cambridge, MA, USA
Volume :
10
Issue :
1
fYear :
1997
fDate :
2/1/1997 12:00:00 AM
Firstpage :
52
Lastpage :
61
Abstract :
Optical emission spectroscopy (OES) is often used to obtain in-situ estimates of process parameters and conditions in plasma etch processes. Two barriers must be overcome to enable the use of such information for real-time process diagnosis and control. The first barrier is the large number of measurements in wide-spectrum scans, which hinders real-time processing. The second barrier is the need to understand and estimate not only process conditions, but also what is happening on the surface of wafer, particularly the spatial uniformity of the etch. This paper presents a diagnostic method that utilizes multivariable OES data collected during plasma etch to estimate spatial asymmetries in commercially available reactor technology. Key elements of this method are: first, the use of principal component analysis (PCA) for dimensionality reduction, and second, regression and function approximation to correlate observed spatial wafer information (i.e., line width reduction) with these reduced measurements. Here we compare principal component regression (PCR), partial least squares (PLS), and principal components combined with multilayer perceptron neural networks (PCA/MLP) for this in-situ estimation of spatial uniformity. This approach has been verified for a 0.35-μm aluminum etch process using a Lam 9600 TCP etcher. Models of metal line width reduction across the wafer are constructed and compared: the root mean square prediction errors on a test set withheld from training are 0.0134 μm for PCR, 0.014 μm for PLS, and 0.016 μm for PCA/MLP. These results demonstrate that in-situ spatially resolved OES in conjunction with principal component analysis and linear or nonlinear function approximation can be effective in predicting important product characteristics across the wafer
Keywords :
function approximation; least squares approximations; multilayer perceptrons; plasma diagnostics; spectrochemical analysis; sputter etching; statistical analysis; 0.35 micron; Al; Lam 9600 TCP etcher; function approximation; metal line width; multilayer perceptron neural network; multivariable OES; optical emission spectroscopy; partial least squares; plasma etching; principal component analysis; real-time process diagnosis; regression; spatial uniformity; wafer state; Etching; Function approximation; Parameter estimation; Plasma applications; Plasma diagnostics; Plasma materials processing; Plasma measurements; Principal component analysis; Spectroscopy; Stimulated emission;
fLanguage :
English
Journal_Title :
Semiconductor Manufacturing, IEEE Transactions on
Publisher :
ieee
ISSN :
0894-6507
Type :
jour
DOI :
10.1109/66.554484
Filename :
554484
Link To Document :
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