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Determination of Overetching by Combined PCV and SIMS

IP.com Disclosure Number: IPCOM000042035D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Hinkel, H: AUTHOR [+3]

Abstract

Unwanted etching of a doped silicon substrate during the removal of an overlaying SiO2 layer can be quantitatively measured by comparing the doping profiles obtained by pulsed capacitance voltage (PCV) measurements at the unetched sample and by secondary ion mass spectroscopy (SIMS) after etching. Fig. 1 shows in its lower part the original layer structure with SiO2 covering an Si substrate doped with boron. The upper part of Fig. 1 shows the boron concentration as determined by PCV. The doping profile obtained by SIMS after etching is illustrated in Fig. 2, where the SIMS intensity is plotted over a time axis related to the depth scale by the etch rate during SIMS analysis. Surface effects distort the SIMS profile in a range S below the surface.

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Determination of Overetching by Combined PCV and SIMS

Unwanted etching of a doped silicon substrate during the removal of an overlaying SiO2 layer can be quantitatively measured by comparing the doping profiles obtained by pulsed capacitance voltage (PCV) measurements at the unetched sample and by secondary ion mass spectroscopy (SIMS) after etching. Fig. 1 shows in its lower part the original layer structure with SiO2 covering an Si substrate doped with boron. The upper part of Fig. 1 shows the boron concentration as determined by PCV. The doping profile obtained by SIMS after etching is illustrated in Fig. 2, where the SIMS intensity is plotted over a time axis related to the depth scale by the etch rate during SIMS analysis. Surface effects distort the SIMS profile in a range S below the surface. It has been found that for relatively low boron concentrations (up to 1017/cm3) the boron profiles measured by SIMS and PCV are identical if they are matched to each other, using only the known doping dose and the maxima of both profiles. Thus, the degree of overetching (distance W between the original Si surface 20 and the new surface
21) can be read from the combined diagram in Fig. 3. No recalibration of the time axis in the original SIMS plot is necessary for this purpose.

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