Application of ultraviolet depth lithography for surface micromachining

Loechel, B.; Maciossek, A.; Rothe, Martina

doi:10.1116/1.588282

Cited by 9 publications

(5 citation statements)

References 5 publications

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“…However, the X-ray source, synchrotron, is very expensive and not widely available. The other is LIGA-like process [2,3], called UV-LIGA or often known as poor man's LIGA, using UV optical lithography, has been developed and demonstrated as a economical and effective way to produce high aspect ratio microstructures. While using UV lithography to fabricate microstructures with thickness up to 1 mm, its diffraction error can severely affect the quality of sidewall profile of microstructures.…”

Section: Introductionmentioning

confidence: 99%

Reduction of diffraction effect of UV exposure on SU-8 negative thick photoresist by air gap elimination

Chuang¹,

Tseng²,

Lin³

2002

Microsystem Technologies

112

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This paper reports a novel way to compensate the air gap between photomask and photoresist for eliminating UV light diffraction on photoresist, which greatly increases the sidewall straightness of high-aspect-ratio resist structures. In this research, SU-8 negative tone photoresist was used for experiments, and glycerol was employed as an index match material for bridging air gap between photomask and photoresist during exposure. Results showed that a high aspect ratio wall structure of 156 lm thick and 25 lm wide had a 45% pattern width error when exposed under 100 lm air gap, while glycerol compensated process accomplished a straight resist wall without appreciable error. This method is simple and cheap to employ, compared to the usage of costly thickphotoresist-film spinner for resist planarization. Numerical simulation on the diffraction effect upon the structure wall has also been conducted. The calculated and experiment wall profiles showed similarity in trend.

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Section: Introductionmentioning

confidence: 99%

Reduction of diffraction effect of UV exposure on SU-8 negative thick photoresist by air gap elimination

Chuang¹,

Tseng²,

Lin³

2002

Microsystem Technologies

112

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“…An optimized procedure guarantees highquality resist patterns, in particular high edge steepness, high resolution, high aspect ratio, high resist stability, and short process duration. During the process, mechanical stress has to be reduced to a minimum [19,20]. Different strategies are under investigation.…”

Section: Introductionmentioning

confidence: 99%

Thick-layer resists for surface micromachining

Loechel¹

2000

J. Micromech. Microeng.

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Interest in thick-photoresist applications is steadily growing. In addition to bump fabrication and wire interconnect technology (WIT), the process of patterning thick-layer photoresists by UV lithography is specially qualified for applications in microelectromechanical systems (MEMS). Specialized equipment and new photoresists have been developed or are under development to cope with the new challenges in the field of preparing extremely thick photoresist layers, the process of patterning these thick resists, and to deal with the difficulties of the following galvanoplating step. As one of the most critical steps in thick-photoresist processing, the baking procedure was investigated. Positive tone photoresists (AZ 4562, maP 100) were processed by means of three different baking methods: air-forced oven, ramped hotplate, and IR radiation. It could be shown that IR baking is advantageous compared to the other methods with respect to process duration and energy consumption. As for edge steepness, resolution, edge loss, and surface roughness, all methods deliver nearly the same results. A minimum width of 2-3 µm for the resist bars was found to be necessary to withstand the fabrication process of lines and spaces in about 15 µm thick resists. For thicker layers, high aspect ratios of about 10 as well as steep edges of more than 88 • could be fabricated. The development of SU-8, a chemically amplified negative tone photoresist for the 300-450 nm region opened totally new dimensions for the UV depth lithography. Even under development, SU-8 delivers results otherwise only achievable by x-ray lithography. The deposition of photoresist on highly-structured surfaces demands advanced methods. Electrodeposition of resist is one solution. PEPR 2400 was used for patterning by UV light in order to generate resist patterns around a free standing silicon bar. The achieved resist patterns were moulded by using electroplating. For microsystem applications some metals and alloys were deposited. Three-dimensional micro components were fabricated as demonstrators for the new technique. Electrodeposition allows the use of materials with interesting properties which could not be provided by standard processes in microelectronics.

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“…This may be the reason why we can find surface-micromachined passive components preferably used for circuit integration in many recent papers [2], [20], [22], [28], [29]. As a technique to build microstructures on the top of substrate, thick-metal surface micromachining has been investigated during the last decade, based on LIGA and LIGA-like technologies [38]- [41]. It consists of fabrication of molds followed by electroplating.…”

Section: Introductionmentioning

confidence: 99%

“…UV-sensitive polyimide [39] has been used to build inductors [16], [23], [24], [26] and filters [24]. Conventional positive thick photoresist [40], [41] have been utilized for inductors [17]- [19], [25], [27] and CPW lines [33]. Epoxy-based negative thick photoresist [42] has been also utilized for inductors [20].…”

Section: Introductionmentioning

confidence: 99%

3-D construction of monolithic passive components for RF and microwave ICs using thick-metal surface micromachining technology

Yoon

Kim

Choi

et al. 2003

IEEE Trans. Microwave Theory Techn.

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As a viable technological option to address today's strong demands for high-performance monolithic low-cost passive components in RF and microwave integrated circuits (ICs), a new CMOS-compatible versatile thick-metal surface micromachining technology has been developed. This technology enables to build arbitrary three-dimensional (3-D) metal microstructures on standard silicon substrate as post-IC processes at low temperature below 120 C. Using this technology, various highly suspended 3-D microstructures have been successfully demonstrated for RF and microwave IC applications. We have demonstrated spiral inductors suspended 100 m over the substrate, coplanar waveguides suspended 50 m over the substrate, and complicated microcoaxial lines, which have 50m-suspended center signal lines surrounded by inclined ground shields of 100 m in height. The microwave performance of the microcoaxial transmission line fabricated on a glass substrate has been evaluated to achieve very low attenuation of 0.03 dB/mm at 10 GHz with an effective dielectric constant of 1.6. The process variation/manufacturability, mechanical stability, and package issues also have been discussed in detail. Index Terms-Coaxial transmission lines, coplanar microstrip lines, high-, inductors, RF and microwave microelectromechanical systems (MEMS), silicon RF integrated circuits (ICs), surface micromachining, three-dimensional (3-D) micromachined passive components.

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Application of ultraviolet depth lithography for surface micromachining

Cited by 9 publications

References 5 publications

Reduction of diffraction effect of UV exposure on SU-8 negative thick photoresist by air gap elimination

Reduction of diffraction effect of UV exposure on SU-8 negative thick photoresist by air gap elimination

Thick-layer resists for surface micromachining

3-D construction of monolithic passive components for RF and microwave ICs using thick-metal surface micromachining technology

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