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Improved Polysilicon Deposition Process

IP.com Disclosure Number: IPCOM000043504D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Choi, MS: AUTHOR [+2]

Abstract

Described is a modification for precleaning prior to a polysilicon deposition process, which reduces the number of LPDs (Light Point Defects). Typically this proposed polysilicon deposition process involves the steps of: (i) preclean with H2SO4 (150 C) + 10:1 dilute HF for 15 seconds (ii) dark field inspection (magnification 375X) for LPDs, (iii) polysilicon deposition, and (iv) dark field inspection for LPDs. Fig. 1 shows the plot of yield vs number of LPDs/transistor for the polysilicon deposition process. As indicated, the yield is strongly dependent on the number of LPDs/transistor. Fig. 2 shows a typical in-line data for number of LPDs/transistor vs. run numbers processed in an experimental line (DPF).

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Improved Polysilicon Deposition Process

Described is a modification for precleaning prior to a polysilicon deposition process, which reduces the number of LPDs (Light Point Defects). Typically this proposed polysilicon deposition process involves the steps of: (i) preclean with H2SO4 (150 C) + 10:1 dilute HF for 15 seconds

(ii) dark field inspection (magnification 375X)

for LPDs,

(iii) polysilicon deposition, and

(iv) dark field inspection for LPDs. Fig. 1 shows the plot of yield vs number of LPDs/transistor for the polysilicon deposition process. As indicated, the yield is strongly dependent on the number of LPDs/transistor. Fig. 2 shows a typical in-line data for number of LPDs/transistor vs. run numbers processed in an experimental line (DPF). As seen in this figure, product wafers of conventional processing had an unacceptable amount of LPDs (specifically less than 10/transistor) compared to monitor wafers. Both product and monitor wafers appeared good (clean) after preclean. This indicates that there is some residue (possibly organic) on product wafers which was not completely removed by the former processing and was invisible under the dark field inspection done before polysilicon was deposited. Fig. 3 shows the results of different pre-clean experiments to remove those invisible contaminations which affect the nucleation and growth of polysilicon film. Post-clean in this experiment means conventional post-clean operation at the photoresist sector performed...