Comparison of liquid- and vapor-phase silylation processes for 193-nm positive-tone lithography

Mihov

Advances in Resist Technology and Processing XX

et al. 2003

Focused Ion beam (FIB) lithography has significant advantages over the electron beam counterpart in terms of resist sensitivity, backscattering and proximity effects. However, combining the FIB lithography with Top Surface Imaging (TSI) will extend its advantages by allowing anisotropic processing of thicker resist layers. This paper reports the development of novel single layer lithography process by combining focused Ga + ion beam (Ga + FIB) lithography, silylation and oxygen dry etching. The Negative Resist Image by Dry Etching (NERIME) is a TSI scheme for DNQ/novolak based resists and can result in either positive or negative resist images depending on the extent of the ion beam exposure dose. Results show that Ga + ion beam dose in the range of 1µC/cm 2 to 50µC/cm 2 at 30keV can successfully prevent silylation of the resist, thus resulting in the formation of positive image after the dry etching. A negative image can be formed by using a second Ga + ion beam exposure with a dose higher than 900µC/cm 2 at 30keV to pattern lines into the original exposed resist area. It was observed that resist regions exposed to such high doses can effectively withstand oxygen dry development, thus giving formation of negative resist image. In this study, nanometer resist patterns with high aspect ratio up to 15 were successfully resolved due to the ion beam exposure and anisotropic dry development. This novel TSI scheme for ion beam lithography could be utilized for the fabrication of critical CMOS process steps, such as deep isolation trench formation and lithography over substantial topography.

Section: The Nerime Processmentioning

confidence: 80%

Negative resist image by dry etching as a novel top surface imaging process for ion-beam lithography

Mihov

Advances in Resist Technology and Processing XX

et al. 2003

“…Case II diffusion, rather than Fickian diffusion, denotes that the diffusion of the silylation agent through the polymer and the chemical reaction with the phenolic -OH resin groups occur at comparable time scales. The same behaviour of the liquid-phase silylation process was also observed by Hartney et al [11], using HMCTS silylation agent and Rutherford backscattering (RBS) analysis.…”

Section: B Silicon Uptake In Spr505asupporting

confidence: 78%

“…The siloxane structures are products of a polymerization reaction resulting in more than one silylating molecule bonded to each phenolic -OH group [18]. A similar siloxane formation from the reaction of the silylating agent with water impurity in the bath or in the film has been reported earlier [12,16,18], although Hartney et al [11] reported no polymerization has took place after HMCTS silylation.…”

Section: B Silicon Uptake In Spr505amentioning

confidence: 55%

“…Gogolides et al [10] demonstrated a 0.5µm resolution using a commercial novolak resist AZ5214 with HMCTS (Hexamethylcyclotrisilazane) liquid-phase silylation process. Hartney et al [11] has evaluated the performance of poly-vinyl-phenol based resists under 193nm exposure and liquid-phase silylation with HMCTS, achieving a 0.25µm resolution. Ohfuji et al [12] shrink the resolution down to 0.15µm using the same resist under 193nm exposure and Bis[Dimethylamino]dimethylsilane (B[DMA]DMS) liquid-phase silylation agent.…”

Section: Top Surface Imaging Processesmentioning

confidence: 99%

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Top surface imaging lithography processes for I-line resists using liquid-phase silylation

2002 23rd International Conference on Microelectronics. Proceedings (Cat. No.02TH8595)

Mihov

Arshak³

et al.

-In this paper, liquid-phase silylation process for Top Surface Imaging Lithography systems incorporated e-beam exposure has been experimentally investigated using FT-IR spectroscopy, UV spectroscopy, SIM spectrometry and SEM cross-sectionals. The impact of different silylating agents on Shipley SPR505A resist system is presented for both the UV exposed and e-beam crosslinked regions of the resist. Results show that an e-beam dose of 50µC/cm 2 at 30KeV is sufficient to crosslink the resist and prevent silylation. The silylation contrast using HMCTS was found to be the highest (11:1) in comparison with other two agents. It was found that the silicon incorporation in SPR505A resist follows Case II diffusion mechanisms.

“…Also, the use of liquid-phase silylation process in NERIME instead of gas-phase result in improved silylation contrast, better selectivity and higher silicon incorporation levels, leading to improved final dry etch profiles as reported elsewhere [18,19] .…”

Section: The Nerime and The Modified 2-step Nerime Processesmentioning

confidence: 81%

Two-step modified NERIME process using combined focused ion beam lithography and plasma etching

et al. 2003

Focused ion beams (FIB) have been widely used as a patterning lithography technique for advanced ICs and optical masks fabrication. FIB lithography has certain advantages over the direct-write electron beam lithography in terms of resist sensitivity, backscattering and proximity effects. However, combining the FIB exposure with both Top Surface Imaging (TSI) and dry etching will further extend its advantages towards anisotropic processing of thicker resist layers in comparison to those used by the conventional lithography processes. The newly developed NERIME (Negative Resist Image by Dry Etching) process combines these advantages by the incorporation of focused Ga + ion beam (Ga + FIB) exposure, near UV exposure, silylation and dry etching. The work described here follows our investigations into the NERIME process for nanostructure applications and outlines a simplified (two-step) process incorporating FIB exposure and oxygen dry development. The two-step modified NERIME process is a negative working TSI system for DNQ/novolak based resists. Results show that Ga + ion beam dose higher than 800µC/cm 2 at 30keV can modify the exposed resist areas as to withstand the subsequent oxygen plasma etching, thus giving formation of negative resist image. In this study, nanometer resist patterns as small as 30nm with high aspect ratio of up to 15 were successfully resolved due to the high resolution ion beam exposure and anisotropic dry development. The proposed two-step lithography scheme could be utilized for the fabrication of critical CMOS process steps, such as sub-100nm gate formations and lithography over substantial topography.