Blanket films of ultralow dielectric constant (ULK) materials and photoresist films have been processed downstream from hydrogen and deuterium-based discharges produced using an inductively coupled plasma reactor. Photoresist ashing rates and ULK modifications have been determined as a function of process parameters. The explored ULK materials differed widely in porosity and carbon content. The effect of processing time, substrate temperature , and gas composition on the surface and bulk chemical composition of ULK materials was monitored and quantified by ex situ ellipsometry and time-of-flight secondary ion mass spectrometry (SIMS). The stripping rates of photoresist films were found to strongly depend on processing temperature and only weakly on the nature of the /additive gas mixture. The authors found that hydrogen (or deuterium) fully penetrates the high porosity ULK layer, whereas for low porosity materials, such penetration is limited to a near-surface region. SIMS measurements also reveal that diffusion into carbon-rich ULK layers can cause substantial carbon depletion throughout the penetration region. ULK damage values increase with temperature and injection of gas additives such as argon, helium, and nitrogen to or process gases. For each ULK material, the amount of damage depends on the gas mixing ratio; in general, high percentages of nitrogen in (or ) mixtures cause the most damage. Overall, the results demonstrate that ULK ashing damage depends strongly on both ULK material properties and -based plasma process parameters. In addition, the authors observed in this work a kinetic isotope effect for stripping of photoresist films in -based discharges. For given ashing process conditions, the photoresist ashing rate decreases by a factor of 1.414 (or square root of 2) in plasma compared to plasma. This can be explained by the influence of the H or D mass on the chemical reaction rate through a change in the frequency of nuclear vibrations of the reacting atoms. The presence of the kinetic isotope effect for gas mixtures provides unambiguous evidence of the rate-limiting role of atomic hydrogen in the fundamental etching reaction. Simultaneously processed ULK materials showed minor film thickness changes in or discharges, and the ULK damage level does not reflect a kinetic isotope effect. Therefore the isotope effect can be used to separate associated ashing and etching processes from other chemistries or mechanisms.
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September 2007
This content was originally published in
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena
Research Article|
August 17 2007
On the photoresist stripping and damage of ultralow dielectric materials using remote - and -based discharges
Guido J. Stueber;
Guido J. Stueber
Department of Materials Science and Engineering and Institute for Research in Electronics and Applied Physics,
University of Maryland
, College Park, Maryland 20742
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Gottlieb S. Oehrlein;
Gottlieb S. Oehrlein
a)
Department of Materials Science and Engineering and Institute for Research in Electronics and Applied Physics,
University of Maryland
, College Park, Maryland 20742
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P. Lazzeri;
P. Lazzeri
ITC-irst
, Center for Scientific and Technological Research, Via Sommarive 18, Povo, I-38050 Trento, Italy
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M. Bersani;
M. Bersani
ITC-irst
, Center for Scientific and Technological Research, Via Sommarive 18, Povo, I-38050 Trento, Italy
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M. Anderle;
M. Anderle
ITC-irst
, Center for Scientific and Technological Research, Via Sommarive 18, Povo, I-38050 Trento, Italy
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Richard McGowan
Richard McGowan
SEMATECH
, Austin, Texas 78741
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a)
Author to whom correspondence should be addressed; electronic mail: [email protected]
J. Vac. Sci. Technol. B 25, 1593–1602 (2007)
Article history
Received:
June 09 2006
Accepted:
July 11 2007
Citation
Guido J. Stueber, Gottlieb S. Oehrlein, P. Lazzeri, M. Bersani, M. Anderle, Eric Busch, Richard McGowan; On the photoresist stripping and damage of ultralow dielectric materials using remote - and -based discharges. J. Vac. Sci. Technol. B 1 September 2007; 25 (5): 1593–1602. https://doi.org/10.1116/1.2769360
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