Abstract
We have completed an experimental study to investigate the use of infrared emission spectroscopy (IRES) for the quantitative analysis of borophosphosilicate glass (BPSG) thin films on silicon monitor wafers. Experimental parameters investigated included temperatures within the range used in the microelectronics industry to produce these films so that the potential for using the IRES technique for real-time monitoring of the film deposition process could be evaluated. The film properties that were investigated included boron content, phosphorus content, film thickness, and film temperature. The studies were conducted over two temperature ranges, 125 to 225 °C and 300 to 400 °C. The latter temperature range includes realistic processing temperatures for the chemical vapor deposition (CVD) of the BPSG films. Partial least-squares (PLS) multivariate calibration methods were applied to spectral and film property calibration data. The cross-validated standard errors of prediction (CVSEP) from the PLS analysis of the IRES spectra of 21 calibration samples each measured at six temperatures in the 300 to 400 °C range were found to be 0.09 wt % for B, 0.08 wt % for P, 3.6 nm for film thickness, and 1.9 °C for temperature. Upon lowering the spectral resolution from 4 to 32 cm−1 and decreasing the number of spectral scans from 128 to 1, we were able to determine that all the film properties could be measured in less than one second to the precision required for the manufacture and quality control of integrated circuits. Thus, real-time in situ monitoring of BPSG thin films formed by CVD deposition on Si monitor wafers is possible with the methods reported here.
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