Reactive Ion Etching Resistant Negative Resists for Ion Beam Lithography

Wada, Yasuo; Mochiji, Kōzō; Obayashi, Hidehito

doi:10.1149/1.2119654

Cited by 8 publications

(1 citation statement)

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“…These results suggest the submicrometer resolution capability of hydrogen ion beam lithography. Together with the reactive ion etching resistant resists (15), the hydrogen ion beam lithography should provide a method for realizing the coming submicrometer VLSI's.…”

Section: Exposure Characteristics O] Pmma By Relatively Lowmentioning

confidence: 99%

Hydrogen and Phosphorus Ion Beam Exposure Characteristics of PMMA

Wada

Migitaka

Mochiji

et al. 1983

J. Electrochem. Soc.

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Hydrogen and phosphorus ion beam exposure characteristics of PMMA are investigated as functions of dose and acceleration energy. PMMA shows both positive and negative exposure characteristics depending on the ion dose. A hydrogen ion dose of 1.6 • 10 -6 C/cm 2 is required to reveal positive exposure characteristics with a contrast of 3, which indicates that PMMA is about two orders of magnitude more sensitive to ions than to electron beam. More than a 4• 10 -5 C/cm 2 ion dose affords negative exposure characteristics with a contrast of about I. The positive exposure characteristics of PMMA are mainly determined by the amount of energy deposited per unit volume. On the other hand, the negative exposure characteristics are mainly determined by the total energy that the surface region receives. The projected ranges and projected deviations of hydrogen and phosphorus ions in PMMA are experimentally determined from the exposure characteristics and are about one order of magnitude smaller than the calculated results. Patterns as narrow as 1 ~m on a stencil mask are neatly replicated in a PMMA layer by a 180 keV hydrogen ion beam, and demonstrate the applicability of ion beam lithography to the submicrometer VLSI fabrication.The technological innovations of lithography in the semiconductor industry have lead to a reduction of the minimum dimensions utilized in LSI's by about 30% every three years (1). The extrapolation of this trend should bring the semiconductor industry to the stage where novel submicrometer lithogi'aphic technology is indispensable by about 1985. Recently, ion beam lithography has gathered attention for its capability to fabricate fine patterns. The experimental results of fine line formation in poly (methylmethacrylate) (PMMA) by gallium ion beams (2) and hydrogen ion beams (3, 4) as well as the results of calculated energy deposition of a hydrogen ion beam (5) together with the ion beam sensitivity investigations of PMMA (8,19) suggest that ion beam lithography should provide very high resolution in replicating mask patterns. This paper reports the exposure characteristics of PMMA by hydrogen and phosphorus ion beams, placing emphasis on the experimental verification of the energy deposition of these ions in PMMA. It also reports the capability of fine-line formation by replication of a stencil mask, with as narrow as 1 ~m wide patterns. Experimental ProceduresA p-type, (100) oriented silicon wafer was used as a substrate. PMMA was spun on the substrate to a thickness of around 0.85 ,~m, then prebaked in a nitrogen atmosphere at 200~ for 30 min. The average molecular weight (Mw) of the PMMA was 600,000. Hydrogen or phosphorus ions were implanted into the PMMA layer at an energy of between 30-180 keV by an ion implanter. The dose range utilized in this experiment was between 10 -s and 10 -3 C/cm e. Charge up effect on the resist during ion implantation was negligible, which has been experimentally demonstrated previously (17). The substrate temperature during ion exposure was kept below 50~ by a su...

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Section: Exposure Characteristics O] Pmma By Relatively Lowmentioning

confidence: 99%