Browsing by Author "Shew, BY"

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High precision, low cost mask for deep x-ray lithography
(1998-02-01)
Shew, BY
;
Cheng, Y
;
Shih, WP
;
Lu, M
;
Lee, WH
The precision of transferred patterns are highly dependent on the quality of the mask in deep x-ray lithography. Many parameters, such as the critical energy of the synchrotron light, beamline optics and even the microstructure to be exposed should be considered in mask design. In this paper, the design rules and the boundary conditions for deep x-ray mask are discussed in general. The method of making a precision, multilayer mask using UV lithography technique is also described.
High precision, low cost mask for deep x-ray lithography
(1998-02-01)
Shew, BY
;
Cheng, Y
;
Shih, WP
;
Lu, M
;
Lee, WH
The precision of transferred patterns are highly dependent on the quality of the mask in deep x-ray lithography. Many parameters, such as the critical energy of the synchrotron light, beamline optics and even the microstructure to be exposed should be considered in mask design. In this paper, the design rules and the boundary conditions for deep x-ray mask are discussed in general. The method of making a precision, multilayer mask using UV lithography technique is also described.
High resolution x-ray micromachining using SU-8 resist
(2003-09-01)
Shew, BY
;
Hung, JT
;
Huang, TY
;
Liu, KP
;
Chou, CP
This paper investigates the feasibility of using SU-8 as a high contrast x-ray resist. The SU-8 resist was irradiated with various x-ray doses and then developed for a fixed time. The developing rate was then measured and plotted versus absorbed x-ray dosage. The results revealed that SU-8 exhibited very high lithographic contrast other than elevated sensitivity. Therefore, a very thin mask absorber is required to switch the negative resist 'ON' or 'OFF'. Preliminary results showed that 1 mum wide, 17 mum thick SU-8 resists could be successfully patterned using an absorber of submicron thickness. Once the absorber thickness is effectively reduced to less than 1 mum, a high-resolution x-ray mask can be patterned simply by conventional UV lithography. An extra soft x-ray beamline was not required to increase the absorber's thickness in certain cases. The process of fabricating the membrane x-ray mask could thus be considerably simplified. X-ray micromachining may be an easy way to pattern high-resolution and high-aspect-ratio microstructures for optical and photonic applications.
Micromachining program status at the SRRC
(1997-12-01)
Cheng, Y
;
Shew, BY
;
Shih, WP
;
Wang, SS
;
Lin, CY
This paper describes the micromachining program status of the micromachining laboratory at the SRRC. A preliminary LIGA process has been established. Many joint projects with local and foreign institutes to develop devices for domestic industries have been started. The interests in the application of the LIGA technology is continuously growing in Taiwan. Two-millimeter ultra-deep microstructures have been achieved.
Oxygen quenching effect in ultra-deep X-ray lithography with SU-8 resist
(2004-03-01)
Shew, BY
;
Huang, TY
;
Liu, KP
;
Chou, CP
;
機械工程學系
An ultra-thick (1.5 mm) SU-8 resist was prepared and patterned using synchrotron x-rays. The lithographic sensitivity of the SU-8 resist is over 100 times higher than that of the traditional PMMA resist. However, preliminary results showed that the standard resist process produced poor lithographic quality. The fluorescence induced by high-energy x-ray irradiation was believed to blur the transfer pattern. The lithographic quality improved significantly if the resists were relaxed in an oxygen atmosphere before being soft baked. The FTIR spectrum displayed new absorption peaks, corresponding to the C=O bond, in the oxygen-relaxed resists. The development rates of the low-dosed resists increased if they were held in the oxygen atmosphere, implying that trapped oxygen restrains the cross linking of the SU-8 resist. Based on these observations, this study proposes an oxygen quenching mechanism for interpreting these phenomena. When the SU-8 is oxygen relaxed, the oxygen molecules will gradually diffuse into the resist. Oxygen is a strong free-radical scavenger, and thus kills the free radicals generated by fluorescence, providing a clear pattern defined by x-ray irradiation. After the SU-8 resist was properly oxygen treated, the maximum dimension error was only about 2 mum for a 1.5 mm-thick SU-8 resist. This lithographic quality is good enough to meet the micromachining requirements for mm-wave RF (radio frequency) cavity applications.
UV-LIGA interferometer biosensor based on the SU-8 optical waveguide
(2005-05-17)
Shew, BY
;
Kuo, CH
;
Huang, YC
;
Tsai, YH
;
機械工程學系
SU-8 resist was used as a core/cladding waveguide material to fabricate a Mach-Zehnder interferometer (MZI) for biochemical sensing. The refractive index of the SU-8 resist was fine-tuned with a Delta n of 0.004 for single-mode transmission. The UV lithography processes of the SU-8 resist were also optimized to pattern the high resolution (1 mu m) and high aspect ratio (A(R) = 6) Y-branch structure of the optical interferometer. Optical measurements reveal that the SU-8 MZI chip can efficiently transmit the NIR laser (lambda = 13 10 mu) with a total loss less than 6 dB. When one branch of the MZI is in contact with the analyte, the interfered intensity stabilizes after the soaking time exceeds 5 min. NaCl solution with a concentration of 10(-9) g/l can be detected using the SU-8 MZI chip. In the future, the polymer MZI chip can be mass-produced by molding process (or the LIGA process). The low-cost, label-free, real-time and high-sensitivity MZI chip will benefit many applications related to biological, environmental and industrial detection. (c) 2005 Elsevier B.V. All rights reserved.
X-ray micromachining SU-8 resist for a terahertz photonic filter
(2005-04-07)
Shew, BY
;
Li, HC
;
Pan, CL
;
Ko, CH
;
機械工程學系
Deep x-ray lithography (DXL) was used to fabricate two-dimensional photonic crystals (PCs) for a terahertz high-pass filter. Instead of the conventional poly(methyl rnethacrylate) resist, high-sensitivity SU-8 resist was used to pattern the ultra-deep (1 mm), and high aspect ratio (> 30) PC structures. In this study, an x-ray mask with thick Si membrane was used in the DXL process owing to the high-sensitivity nature of SU-8. The robust mask structure can significantly improve the fabrication yield of the conventional x-ray mask with a very thin (< 2 mu m) membrane. Preliminary results demonstrate that SU-8 has poor pattern definition after DXL process, probably due to its high sensitivity. This phenomenon can be eliminated by dissolving oxygen into the resist to 'quench' the excessive photochemical reaction. Thanks to the high adhesion property of SU-8, the sticking problem of the high aspect ratio crystals is easily solved with natural drying by reducing the unbalanced capillary force. After optimizing all the processes. the proposed DXL SU-8 technique successively fabricated the terahertz crystals with high efficiency, high precision 1(< 1 mu m) and high surface quality (R(a) similar to 12 nm). The resist pillars were then deposited with a 300 nm thick gold layer for subsequent terahertz, measurement. The measurement results show that the PC structure acts as a high-pass filter in the terahertz, range. agreeing with the simulation results.