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Title: Methods for passivating silicon devices at low temperature to achieve low interface state density and low recombination velocity while preserving carrier lifetime

Abstract

A new process has been developed to achieve a very low SiO.sub.x /Si interface state density D.sub.it, low recombination velocity S (<2 cm/s), and high effective carrier lifetime T.sub.eff (>5 ms) for oxides deposited on silicon substrates at low temperature. The technique involves direct plasma-enhanced chemical vapor deposition (PECVD), with appropriate growth conditions, followed by a photo-assisted rapid thermal annealing (RTA) process. Approximately 500-A-thick SiO.sub.x layers are deposited on Si by PECVD at 250.degree. C. with 0.02 W/cm.sup.-2 rf power, then covered with SiN or an evaporated thin aluminum layer, and subjected to a photo-assisted anneal in forming gas ambient at 350.degree. C., resulting in an interface state density D.sub.it in the range of about 1-4.times.10.sup.10 cm.sup.-2 eV.sup.-1, which sets a record for the lowest interface state density D.sub.it for PECVD oxides fabricated to date. Detailed analysis shows that the PECVD deposition conditions, photo-assisted anneal, forming gas ambient, and the presence of an aluminum layer on top of the oxides during the anneal, all contributed to this low value of interface state density D.sub.it. Detailed metal-oxide semiconductor analysis and model calculations show that such a low recombination velocity S is the result of moderately high positive oxide charge (5.times.10.sup.11 -1.times.10.sup.12more » cm.sup.-2) and relatively low midgap interface state density (1.times.10.sup.10 -4.times.10.sup.10 cm.sup.-2 eV.sup.-1). Photo-assisted anneal was found to be superior to furnace annealing, and a forming gas ambient was better than a nitrogen ambient for achieving a very low surface recombination velocity S.« less

Inventors:
 [1];  [2]
  1. Duluth, GA
  2. Marietta, GA
Issue Date:
OSTI Identifier:
870137
Patent Number(s):
5462898
Assignee:
Georgia Tech Research Corporation (Atlanta, GA)
DOE Contract Number:  
E21-H21; E21-H31
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
methods; passivating; silicon; devices; temperature; achieve; interface; density; recombination; velocity; preserving; carrier; lifetime; process; developed; sio; cm; effective; eff; oxides; deposited; substrates; technique; involves; direct; plasma-enhanced; chemical; vapor; deposition; pecvd; appropriate; growth; conditions; followed; photo-assisted; rapid; thermal; annealing; approximately; 500-a-thick; layers; 250; degree; 02; -2; rf; power; covered; evaporated; aluminum; layer; subjected; anneal; forming; gas; ambient; 350; resulting; range; 1-4; times; 10; -1; sets; record; lowest; fabricated; date; detailed; analysis; presence; top; contributed; value; metal-oxide; semiconductor; model; calculations; result; moderately; positive; oxide; charge; 11; 12; relatively; midgap; -4; found; superior; furnace; nitrogen; achieving; surface; silicon device; enhanced chemical; aluminum layer; forming gas; thermal annealing; silicon substrates; chemical vapor; vapor deposition; silicon substrate; rf power; silicon devices; technique involves; rapid thermal; carrier lifetime; plasma-enhanced chemical; oxide semiconductor; deposition conditions; /438/

Citation Formats

Chen, Zhizhang, and Rohatgi, Ajeet. Methods for passivating silicon devices at low temperature to achieve low interface state density and low recombination velocity while preserving carrier lifetime. United States: N. p., 1995. Web.
Chen, Zhizhang, & Rohatgi, Ajeet. Methods for passivating silicon devices at low temperature to achieve low interface state density and low recombination velocity while preserving carrier lifetime. United States.
Chen, Zhizhang, and Rohatgi, Ajeet. Sun . "Methods for passivating silicon devices at low temperature to achieve low interface state density and low recombination velocity while preserving carrier lifetime". United States. https://www.osti.gov/servlets/purl/870137.
@article{osti_870137,
title = {Methods for passivating silicon devices at low temperature to achieve low interface state density and low recombination velocity while preserving carrier lifetime},
author = {Chen, Zhizhang and Rohatgi, Ajeet},
abstractNote = {A new process has been developed to achieve a very low SiO.sub.x /Si interface state density D.sub.it, low recombination velocity S (<2 cm/s), and high effective carrier lifetime T.sub.eff (>5 ms) for oxides deposited on silicon substrates at low temperature. The technique involves direct plasma-enhanced chemical vapor deposition (PECVD), with appropriate growth conditions, followed by a photo-assisted rapid thermal annealing (RTA) process. Approximately 500-A-thick SiO.sub.x layers are deposited on Si by PECVD at 250.degree. C. with 0.02 W/cm.sup.-2 rf power, then covered with SiN or an evaporated thin aluminum layer, and subjected to a photo-assisted anneal in forming gas ambient at 350.degree. C., resulting in an interface state density D.sub.it in the range of about 1-4.times.10.sup.10 cm.sup.-2 eV.sup.-1, which sets a record for the lowest interface state density D.sub.it for PECVD oxides fabricated to date. Detailed analysis shows that the PECVD deposition conditions, photo-assisted anneal, forming gas ambient, and the presence of an aluminum layer on top of the oxides during the anneal, all contributed to this low value of interface state density D.sub.it. Detailed metal-oxide semiconductor analysis and model calculations show that such a low recombination velocity S is the result of moderately high positive oxide charge (5.times.10.sup.11 -1.times.10.sup.12 cm.sup.-2) and relatively low midgap interface state density (1.times.10.sup.10 -4.times.10.sup.10 cm.sup.-2 eV.sup.-1). Photo-assisted anneal was found to be superior to furnace annealing, and a forming gas ambient was better than a nitrogen ambient for achieving a very low surface recombination velocity S.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1995},
month = {1}
}

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