Dependence of Trench Charging on the Velocity Distribution of Ions incident on a SiO2 Wafer

T. Yagisawa, T. Makabe

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

As ULSI device dimensions have been scaled down, a number of issues have been raised during plasma etching. Especially, a charging damage during plasma etching is important issue to be addressed. We focus on the charging caused by the difference of the velocity distribution between electrons and positive ions incident on a SiO2 wafer. Etching of SiO2 is performed by using high energy positive ions accelerated in a sheath in a collision dominated region for pressure, 5 mTorr - 50 mTorr in two-frequency capacitively coupled plasma (2f-CCP). The velocity distribution of ions incident on a wafer is, therefore, one of the crucial factors governing the characteristics of the plasma etching. The velocity distribution striking the wafer is strongly affected by the oscillation of the sheath potential formed in front of the wafer, and the distribution depends on the bias frequency, voltage, gas pressure and sheath width etc. A numerical analysis is an attractive approach to predict the time profile of the velocity distribution, because it is difficult to perform a time resolved measurement of the ion velocity distribution.A negative ion injection to the wafer were numerically predicted and designed in a pulsed 2f-CCP driven at VHF(100 MHz) - LF(1 MHz) as one of the practical solutions to the reduction of the charging damage. An experimental evidence of the injection of negative ion to the wafer and of a reduction of charging at the bottom of SiO2 holes were visualized by the emission selected CT image close to the wafer and the test chip measurement during etching in almost the same system as the numerical. We have, however, few results of ion velocity distribution at the wafer deeply biased by the LF source in a 2f-CCP system.In this work, the time dependence of the velocity distribution of positive and negative ions incident on the wafer in a pulsed 2f-CCP in CF4(5%)/Ar is first discussed. Quite different behavior of the velocity distribution of ions between ON and OFF period of the VHF plasma source was shown. These velocity distributions with difference in polarity and magnitude have key roles in reducing the topographically local charging inside the trench during plasma etching. The mechanism of the charge reduction is also discussed associated with the ion velocity incident on the wafer with a trench pattern.

Original languageEnglish
Title of host publicationIEEE International Conference on Plasma Science
Pages128
Number of pages1
Publication statusPublished - 2003
Event2003 IEEE International Conference on Plasma Science - Jeju, Korea, Republic of
Duration: 2003 Jun 22003 Jun 5

Other

Other2003 IEEE International Conference on Plasma Science
CountryKorea, Republic of
CityJeju
Period03/6/203/6/5

Fingerprint

charging
velocity distribution
wafers
plasma etching
ions
positive ions
sheaths
negative ions
etching
ion injection
damage
time dependence
gas pressure
numerical analysis
polarity
chips
time measurement
injection
oscillations
collisions

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Yagisawa, T., & Makabe, T. (2003). Dependence of Trench Charging on the Velocity Distribution of Ions incident on a SiO2 Wafer. In IEEE International Conference on Plasma Science (pp. 128)

Dependence of Trench Charging on the Velocity Distribution of Ions incident on a SiO2 Wafer. / Yagisawa, T.; Makabe, T.

IEEE International Conference on Plasma Science. 2003. p. 128.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Yagisawa, T & Makabe, T 2003, Dependence of Trench Charging on the Velocity Distribution of Ions incident on a SiO2 Wafer. in IEEE International Conference on Plasma Science. pp. 128, 2003 IEEE International Conference on Plasma Science, Jeju, Korea, Republic of, 03/6/2.
Yagisawa T, Makabe T. Dependence of Trench Charging on the Velocity Distribution of Ions incident on a SiO2 Wafer. In IEEE International Conference on Plasma Science. 2003. p. 128
Yagisawa, T. ; Makabe, T. / Dependence of Trench Charging on the Velocity Distribution of Ions incident on a SiO2 Wafer. IEEE International Conference on Plasma Science. 2003. pp. 128
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