Quantitative determination of borophosphosilicate glass thin-film properties using infrared emission spectroscopy

We have completed an experimental study to investigate the use of infrared emission spectroscopy (IRES) for the quantitative analysis of borophosphosi licate glass (BPSG) thin films on silicon monitor wafers. Experimental para meters investigated included temperatures within the range used in the micr oelectronics industry to produce these films so that the potential for usin g the IRES technique for real-time monitoring of the film deposition proces s could be evaluated. The film properties that were investigated included b oron content, phosphorus content, film thickness, and film temperature. The studies were conducted over two temperature ranges, 125 to 225 degrees C a nd 300 to 400 degrees C. The latter temperature range includes realistic pr ocessing temperatures for the chemical vapor deposition (CVD) of the BPSG f ilms, Partial least-squares (PLS) multivariate calibration methods were app lied to spectral and film property calibration data. The cross-validated st andard errors of prediction (CVSEP) from the PLS analysis of the IRES spect ra of 21 calibration samples each measured at six temperatures in the 300 t o 400 degrees 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 degrees C for temperature. Upon lowering t he spectral resolution from 4 to 32 cm(-1) and decreasing the number of spe ctral scans from 128 to 1, we were able to determine that all the film prop erties 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 m onitor wafers is possible with the methods reported here.