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Radiation Sensitive Organosilicon Materials for E-Beam Lithography

IP.com Disclosure Number: IPCOM000122465D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 37K

Publishing Venue

IBM

Related People

Babich, ED: AUTHOR [+6]

Abstract

High molecular weight polydimethylsiloxanes (PDMS) are know to be very sensitive to electron beam (E-beam) irradiation and therefore can be used as imageable protective top layers for O2 RIE pattern transfer using double layer lithographic technique [1]. Disadvantages of PDMS gums working as negative tone crosslinkable resist materials are low glass transition temperature (Tg) and low contrast.

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Radiation Sensitive Organosilicon Materials for E-Beam Lithography

      High molecular weight polydimethylsiloxanes (PDMS) are
know to be very sensitive to electron beam (E-beam) irradiation and
therefore can be used as imageable protective top layers for O2 RIE
pattern transfer using double layer lithographic technique [1].
Disadvantages of PDMS gums working as negative tone crosslinkable
resist materials are low glass transition temperature (Tg) and low
contrast.

      One of the ways to increase Tg is the introduction of aromatic
substituents into PDMS-type polymers.  But such a modification
reduces dramatically E-beam sensitivities of resist materials [2].

      It was found that linear PDMS oligomers having pendant
aminopropyl groups (mol. wt. of about 5.000-20.000, nitrogen content
3-5% wt.) when reacted with mesitylene-2-sulfonyl chloride or
toluene-4- sulfonyl chloride in the presence of trithylamine (HCI
acceptor) form products with the following structure:
whose sensitivity to E-beam irradiation is in the range of 1 to 10
uC/cm2 (at 25 KeV) and contrast of about 2 depending on the amount of
modifying groups introduced.  Tg's are much higher compared to PDMS
gums.

      Due to the high silicon content, etch rates are about 20-50
A/min. at 0.2 watt/cm2 and 10 mTorr of oxygen pressure.

      References
(1)  E. D. Roberts, J . Electrochem . Soc . 120, (12), 1716 (1973).
(2)  C. Delides, Radiat . Phys . Chem . 16, 345 (1980).