The Swelling Effects during the Development Processes of Deep UV Lithography of SU-8 Photoresists: Theoretical Study, Simulation and Verification

Zhou, Zai-Fa; Huang, Qing-An; Li, Weihua; Lu, Wu; Zhu, Zhen; Feng, Ming

doi:10.1109/icsens.2007.4388402

Cited by 15 publications

(17 citation statements)

References 16 publications

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“…The modulus of the as‐fabricated SU‐8 was measured by AFM nano‐indentation, 1.7 GPa, and the swelling ratio in PGMEA was ≈ 1.05–1.1, which agreed well with literature . If keeping AR constant, but exposing the SU‐8 film at a higher dosage, more photoacids will be generated, leading to higher crosslinking density and higher filling fraction.…”

Section: Resultssupporting

confidence: 85%

“…Swelling‐deswelling of SU‐8 thin films have been investigated to optimize the processing conditions in photolithography, to study pattern transformation in 2D membranes, and 3D phononic crsytals, and to enhance grafting of polymer brushes on 2D and 3D structures . Typically in photolithography of 1D structures, pattern collapse of high AR structures is observed due to capillary force during drying.…”

Section: Resultsmentioning

confidence: 99%

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Transforming One‐Dimensional Nanowalls to Long‐Range Ordered Two‐Dimensional Nanowaves: Exploiting Buckling Instability and Nanofibers Effect in Holographic Lithography

Cho

Choi

et al. 2013

Adv Funct Materials

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Two‐dimensional nanowaves with long‐range order are fabricated by exploiting swelling‐induced buckling of one‐dimensional (1D) nanowalls with nanofibers formed in‐between during holographic lithography of the negative‐tone photoresist SU‐8. The 1D film goes through a constrained swelling in the development stage, and becomes buckled above the critical threshold. The degree of lateral undulation can be controlled by tuning the pattern aspect ratio (height/width) and exposure dosage. At a high aspect ratio (e.g., 6) and a high exposure dosage, nanofibers (30–50 nm in diameter) are formed between the nanowalls as a result of overlapping of low crosslinking density regions. By comparing experimental results with finite‐element analysis, the buckling mechanism is investigated, which confirms that the nanofibers prevent the deformed nanowalls from recovery to their original state, thus, leading to long‐range ordered two‐dimensional (2D) wavy structures. The film with nanowaves show weaker reflecting color under an ambient light and lower transmittance compared to the straight nanowalls. Using double exposure through a photomask, patterns consisting of both nanowaves and nanowalls for optical display are created.

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Section: Resultssupporting

confidence: 85%

Section: Resultsmentioning

confidence: 99%

Transforming One‐Dimensional Nanowalls to Long‐Range Ordered Two‐Dimensional Nanowaves: Exploiting Buckling Instability and Nanofibers Effect in Holographic Lithography

Cho

Choi

et al. 2013

Adv Funct Materials

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“…3b,c and Supplementary Fig. 10) because the volume expansion due to swelling decreases as the cross-linking density increases 18 . We also found that the cracks tend to reach a constant width-todepth ratio of about 10 (for example, 130-nm deep and 1.3-mm wide; Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Tensile stresses occur naturally in the elastic layer during the development process, causing the viscoelastic layer to swell (Fig. 1c) 18 . When the coarsely cross-linked viscoelastic layer absorbs the solvent molecules, it swells isotropically, and consequently, the thin elastic layer above is subjected to an isotropic tensile stress.…”

Section: Resultsmentioning

confidence: 99%

Cracking-assisted photolithography for mixed-scale patterning and nanofluidic applications

Kim

2015

Nat Commun

104

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Cracks are observed in many environments, including walls, dried wood and even the Earth's crust, and are often thought of as an unavoidable, unwanted phenomenon. Recent research advances have demonstrated the the ability to use cracks to produce various micro and nanoscale patterns. However, patterns are usually limited by the chosen substrate material and the applied tensile stresses. Here we describe an innovative cracking-assisted nanofabrication technique that relies only on a standard photolithography process. This novel technique produces well-controlled nanopatterns in any desired shape and in a variety of geometric dimensions, over large areas and with a high throughput. In addition, we show that mixed-scale patterns fabricated using the 'crack-photolithography' technique can be used as master moulds for replicating numerous nanofluidic devices via soft lithography, which to the best of our knowledge is a technique that has not been reported in previous studies on materials' mechanical failure, including cracking.

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“…The exposure extension is critical because short times produce less dense cross-linked polymers. Therefore, the solvent molecules diffuse into SU-8 bulk swelling the film during its development 34 . PEB raises adhesion, reduces scumming, and improves the contrast and profile of the resist 3 .…”

Section: The Approachmentioning

confidence: 99%

Sacrificial adhesive bonding: a powerful method for fabrication of glass microchips

Lima

Leão

Piazzetta

et al. 2015

Sci Rep

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A new protocol for fabrication of glass microchips is addressed in this research paper. Initially, the method involves the use of an uncured SU-8 intermediate to seal two glass slides irreversibly as in conventional adhesive bonding-based approaches. Subsequently, an additional step removes the adhesive layer from the channels. This step relies on a selective development to remove the SU-8 only inside the microchannel, generating glass-like surface properties as demonstrated by specific tests. Named sacrificial adhesive layer (SAB), the protocol meets the requirements of an ideal microfabrication technique such as throughput, relatively low cost, feasibility for ultra large-scale integration (ULSI), and high adhesion strength, supporting pressures on the order of 5 MPa. Furthermore, SAB eliminates the use of high temperature, pressure, or potential, enabling the deposition of thin films for electrical or electrochemical experiments. Finally, the SAB protocol is an improvement on SU-8-based bondings described in the literature. Aspects such as substrate/resist adherence, formation of bubbles, and thermal stress were effectively solved by using simple and inexpensive alternatives.

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The Swelling Effects during the Development Processes of Deep UV Lithography of SU-8 Photoresists: Theoretical Study, Simulation and Verification

Cited by 15 publications

References 16 publications

Transforming One‐Dimensional Nanowalls to Long‐Range Ordered Two‐Dimensional Nanowaves: Exploiting Buckling Instability and Nanofibers Effect in Holographic Lithography

Transforming One‐Dimensional Nanowalls to Long‐Range Ordered Two‐Dimensional Nanowaves: Exploiting Buckling Instability and Nanofibers Effect in Holographic Lithography

Cracking-assisted photolithography for mixed-scale patterning and nanofluidic applications

Sacrificial adhesive bonding: a powerful method for fabrication of glass microchips

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