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Influence of Fluoride Ions Contamination in Front Opening Unified Pod (FOUP) Generating Defective Bonding Pad

Category: Technical Note

Volume: 17 | Issue: 3 | Pages: 936-941
DOI: 10.4209/aaqr.2016.10.0457
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Soon Seok Kwon1, Sung Min Hwang1, Hyoung Ryeun Kim1, Hee Chang Jang1, Jeong Hoon Hong1, Gil Joo Song1, Hyun Yul Park1, Minsoo Kim2, Youhwan Shin2, Jin Young Kim3, Tae Yong Noh4, Seoung-Kyo Yoo 4

  • 1 Contamination Quality Engineering, Manufacturing and Technology Division, SK Hynix Semiconductor Inc., Icheon-si, Gyeonggi-do 467-701, Korea
  • 2 Center for Urban Energy Research, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 02792, Korea
  • 3 Fuel Cell Research Center, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 02792, Korea
  • 4 WITHTECH INC., Yuseong-gu, Daejeon 34036, Korea

Highlights

The bonding pad of semiconductor chip can be contaminated by etching process.
Defects on bonding pad have crystal structure, not amorphous.
Al2O3 layer of bonding pad abnormally becomes thicker due to presence of F ion.
F ion concentration in FOUP was dramatically decreased by Ar sputtering N2 purge.
N2 purge of FOUP after etching process is necessary to minimize pad defects.


Abstract

We analyzed defective bonding pad in various ways and determined the causes of defects that boosts oxidation of aluminium by fluoride residue on surface of pad with moisture. Additionally, we compared and evaluated methods to minimize pad defects in aspects such as etching and wafer storage environment. In case of wafers after pad open etching process using common CF4 stored in FOUP, the concentration of fluoride ions in FOUP was 230 ng L–1 and it decreased down to 170 ng L–1 when Ar sputtering step was added after using CF4. Also under the same condition, fluoride ion concentration in FOUP decreased down to 20 ng L–1 when nitrogen purge was introduced for 10 minutes to the FOUP where wafers were stored and the moisture also decreased from 40% before purge to 10% after purge. As a result of observation on pad surface after storing wafers in FOUP for 120 hours under each condition, negligible amount of defects were found when nitrogen was purged. Therefore, we conclude that defects on pad were generated by existing fluoride ions after etching process and moisture in the air.

Keywords

Bonding pad Fluoride ion Etching process Contamination Front opening unified pod (FOUP)


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