Dr. Yun Ho Jang Profile

Dr. Yun Ho Jang

Graduate Student at Seoul National Univ

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Publications (3)

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Proceedings Article | 30 December 2004 Paper

Single crystalline silicon micromirror array for maskless photolithography in protein synthesis systems

Yun-Ho Jang, Kook-Nyung Lee, Dong-Sik Shin, Yoon-Sik Lee, Yong-Kweon Kim

Proceedings Volume 5641, (2004) https://doi.org/10.1117/12.574010

KEYWORDS: Mirrors, Semiconducting wafers, Silicon, Micromirrors, Electrodes, Optical lithography, Aluminum, Proteins, Glasses, Crystals

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This paper presents the design, fabrication, and testing of a single crystalline silicon (SCS) micromirror array (MMA) for peptide synthesis applications. Also, preliminary peptide synthesis experiments are presented for the proof of MMA performance. The application specific MMA had a simple fabrication process (only 3 photomasks), large mirror size (210x210μm²) and proper separation (60um). In order to obtain reliable structure and characteristics, we incorporated silicon on insulator (SOI) wafer and stepper photolithography. To maximize the pull-in voltage uniformity, sequential designing steps were described considering design limitations. The proposed fabrication process showed that the fabrication yield was very high up to 91.3%. The total array size consisted of 16 x 16 mirrors and tilting angle was 8.5° for left side or right side operations. The surface roughness was very low and less than 4 nm. The switching time of 156 μsec was reasonable since the exposure time during peptide synthesis was a few seconds. The fabricated MMA had a little pull-in voltage non-uniformity because of dimensional non-uniformities or fabrication errors. We have implemented an automated pull-in voltage measurement setup for verifying the pull-in voltage variation among the array. The measured pull-in voltage among 256 mirrors had the average of 96.99 V and the standard deviation of 2.12 V. The fabricated and analyzed MMA was adapted to the automatic peptide synthesis system and the peptide synthesis experiments showed that the SCS MMA improved the synthesis performance.

Proceedings Article | 30 December 2004 Paper

Silicon scanning mirror with 54.74-degree slanted reflective surface for fluorescence scanning system

Kook-Nyung Lee, Yun-Ho Jang, Jaeho Choi, Hoseoung Kim, Yoon-Sik Lee, Yong-Kweon Kim

Proceedings Volume 5641, (2004) https://doi.org/10.1117/12.575974

KEYWORDS: Mirrors, Silicon, Optical benches, Prisms, Deep reactive ion etching, Photoresist materials, Reflectivity, Electrodes, Optical fibers, Semiconducting wafers

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We fabricated a scanning mirror and optical benches monolithically in a silicon substrate using DRIE process and trench passivation by capillary filling. The micro scanning mirror, actuated by comb electrodes and supported by torsional spring, was fabricated with the optical benches in single crystalline silicon for the integration of optical fibers and ball lenses. Micro prism was adopted for high sensitive fluorescence detection system with scanning mirror. The excitation beam needs to be focused mainly on the slanted area of the micro prism in order to increase optical power efficiency. Considering beam collimation for high power efficiency, beam steering on the micro prism, and simple integration with the micro prism, we proposed silicon scanning mirror having slanted reflective plane and optical benches monolithically fabricated in the same silicon substrate. Reflective surface of the proposed scanning mirror makes parallel incident laser to the substrate be normal downward to the plane of substrate so that optical alignments become simple just by the alignment of scanning mirror’s and micro prism’s substrate. In this research the slanted angle of mirror plane is (-) 54.74 degree inclined instead of 45 degree because the scanning mirror was fabricated in single crystalline silicon (100)-oriented wafer using KOH wet process for the easy fabrication and fast feasibility test. The scanning mirror scans the laser one dimensionally by the actuation so that laser spot can be line-shape on the prism plane. The mirror is a pyramidal structure actuated by comb electrodes and torsion spring. The designed scanning mirror is 2165 x 778 μm² in an upper plane and it has a slanted trapezoidal mirror reflective surface, which size is about 2000 x 1600 μm², considering the micro prism dimension. The maximum deflection angle of the scanning mirror was 7° when 16 V_pp square type voltage is applied to the comb electrodes at resonant frequency.

Proceedings Article | 28 September 2001 Paper

Fabrication of electromagnetic micromirror array

YunHo Jang, Yong-Kweon Kim

Proceedings Volume 4557, (2001) https://doi.org/10.1117/12.442971

KEYWORDS: Mirrors, Micromirrors, Magnetism, Aluminum, Electromagnetism, Nickel, Electroplating, Reflection, Photoresist materials, Micromachining

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This paper describes the design, fabrication and experiments of a micromirror array driven by electromagnetic force for right angle beam reflection to the vertical direction of the substrate. The device was fabricated using aluminum surface micromachining combined with nickel electroplating. The micromirror has couple of torsional springs enough long for 45 degree rotation, which angular deflection is necessary for right angle beam reflection. Also micromirror has a magnetic material for electromagnetic operation, and it has a mechanical stopper for angular deflection control. The main structural material is evaporated aluminum, and magnetic material is electroplated nickel. Thick photoresist is used as a sacrificial layer, and it is removed by oxygen plasma process. Electromagnetic characteristics were measured to find that about 10kA/m magnetic field intensity is needed for 45 degrees angular deflection. 25V to approximately 50V clamping voltage is required for selectively operation between the array within the external magnetic field. The dynamic response measurement was fulfilled using He-Ne laser and position sensitive diode (PSD). The lapsed time to reach 45 degrees is less than 0.5ms. But upward spring bending prevents the stopper from touching the substrate, so some oscillations corresponding to natural response is observed.

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