Study of Development Processes for ZEP-520 as a High-Resolution Positive and Negative Tone Electron Beam Lithography Resist

Mohammad, Mohammad Ali; Koshelev, K.; Fito, Taras; Zheng, David Ai Zhi; Stepanova, Maria; Dew, S. K.

doi:10.7567/jjap.51.06fc05

Cited by 23 publications

(16 citation statements)

References 29 publications

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“…To evaluate the effect of the development process on adhesion, it is known that development is not a layer-by-layer linear dissolution process. 20,21 Instead, the solvent diffuses and penetrates below the top (recessing) surface and dissolves or swells the resist there. The situation is worse for low energy exposure because the under-exposed resist at the bottom is more susceptible to swelling/weakening by the solvent developer that has penetrated there.…”

Section: Resultsmentioning

confidence: 99%

Lift-off with solvent for negative resist using low energy electron beam exposure

Dey

Cui

2014

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Lift-off and direct etch are the two most popular pattern transfer methods for electron beam lithography. For some applications negative resist would offer significantly less exposure time than positive one. Unfortunately, lift-off using negative resist is very challenging because the resist profile is typically positively tapered due to electron forward scattering, and upon exposure, negative resist is cross-linked and thus insoluble in solvents. Here, the authors will show that low energy exposure can circumvent both issues simultaneously, and the authors achieved liftoff of Cr with polystyrene resist using a solvent xylene. Moreover, low energy exposure offers proportionally higher resist sensitivity. Lastly, since low energy electrons are mostly stopped inside the resist layer, radiation damage to the sublayer is greatly reduced. Thus, the current method may be employed to fabricate metal nanostructures on top of an organic conducting layer.

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Section: Resultsmentioning

confidence: 99%

Lift-off with solvent for negative resist using low energy electron beam exposure

Dey

Cui

2014

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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“…In fact, such kind of mixed exposure property is well known for a long time for PMMA that displays a positive tone at low doses and becomes a negative tone at approximately 10 times higher doses [21], which was also employed to generate complex structures [22]. Though less known, another popular resist ZEP-520A actually also exhibits a mixed tone behavior just like PMMA [23]. However, unlike PMMA and ZEP for which the negative tone behavior appears only after roughly 10 times higher doses, for nitrocellulose, the negative tone behavior proceeds the positive tone, and the dose ranges for the two tones have a large overlap and thus they are not clearly separated.…”

Section: Resultsmentioning

confidence: 99%

Electron beam lithography with feedback using in situ self-developed resist

Dey

Cui

2014

Nanoscale Res Lett

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Due to the lack of feedback, conventional electron beam lithography (EBL) is a ‘blind’ open-loop process where the exposed pattern is examined only after ex situ resist development, which is too late for any improvement. Here, we report that self-developing nitrocellulose resist, for which the pattern shows up right after exposure without ex situ development, can be used as in situ feedback on the e-beam distortion and enlargement. We first exposed identical test pattern in nitrocellulose at different locations within the writing field; then, we examined in situ at high magnification the exposed patterns and adjusted the beam (notably working distance) accordingly. The process was repeated until we achieved a relatively uniform shape/size distribution of the exposed pattern across the entire writing field. Once the beam was optimized using nitrocellulose resist, under the same optimal condition, we exposed the common resist PMMA. We achieved approximately 80-nm resolution across the entire writing field of 1 mm × 1 mm, as compared to 210 nm without the beam optimization process.

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“…The quantity contrast-weighted sensitivity has been introduced as our figure of merit to factor in sensitivity while selecting the developer with the best contrast. The IPA/water developer has other merits including cost, safety, and experience of the EBL community using it as a developer for PMMA [1,19,21] and ZEP [19,22] at both ambient and cold development conditions. In addition to the aforementioned developers, the development of SML in MIBK/IPA (1:3) at -15°C cold development conditions was also attempted; however, due to the extremely low sensitivity (clearance onset >1,000 μC/cm 2 ), it was abandoned.…”

Section: Resultsmentioning

confidence: 99%

SML resist processing for high-aspect-ratio and high-sensitivity electron beam lithography

2013

Self Cite

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A detailed process characterization of SML electron beam resist for high-aspect-ratio nanopatterning at high sensitivity is presented. SML contrast curves were generated for methyl isobutyl ketone (MIBK), MIBK/isopropyl alcohol (IPA) (1:3), IPA/water (7:3), n-amyl acetate, xylene, and xylene/methanol (3:1) developers. Using IPA/water developer, the sensitivity of SML was improved considerably and found to be comparable to benchmark polymethylmethacrylate (PMMA) resist without affecting the aspect ratio performance. Employing 30-keV exposures and ultrasonic IPA/water development, an aspect ratio of 9:1 in 50-nm half-pitch dense grating patterns was achieved representing a greater than two times improvement over PMMA. Through demonstration of 25-nm lift-off features, the pattern transfer performance of SML is also addressed.

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Study of Development Processes for ZEP-520 as a High-Resolution Positive and Negative Tone Electron Beam Lithography Resist

Cited by 23 publications

References 29 publications

Lift-off with solvent for negative resist using low energy electron beam exposure

Lift-off with solvent for negative resist using low energy electron beam exposure

Electron beam lithography with feedback using in situ self-developed resist

SML resist processing for high-aspect-ratio and high-sensitivity electron beam lithography

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