Browsing by Author "Ho, CH"

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Characterization of embedded root method in UV-LIGA process
(2003)
Ho, CH
;
Hsu, W
;
機械工程學系
;
Department of Mechanical Engineering
SU-8 photoresist has been popularly used as a mold for electroplating and facilitated low-cost MEMS production in many previous researches. However, the reachable thickness of electroplated structures standing on the substrate were limited to 50 mum below due to the internal stress and deformation of the SU-8 resist in final stripping process. In order to fabricate thicker structures, an embedded root method has been proposed to consolidate the adhesion of the metal structures to the substrate during the SU-8 removal process. In this paper, detailed investigation on this method is conducted to characterize the relationship among the root depth, the line-width and the allowable thickness of the electroplated structures. Some test patterns with embedded roots are designed and tested to generalize the possible extent of various structural scales associated with different niches in depth, which are completely defined through SiO2 masking and KOH etching processes., Based on establishment of the relationship between the root depth and the geometric sizes, a 3-D integrated coil with 200 mum in thickness, 80 mum in width and 4 mum in root depth is successfully released by the SU-8 mold with 400 mum in height, which can not be achieved by the standard SU-8 molding process. The UV-LIGA process presented herein may be applied to the fabrication of other microstructures and microactuators.
Experimental investigation of an embedded root method for stripping SU-8 photoresist in the UV-LIGA process
(2004-03-01)
Ho, CH
;
Hsu, WY
;
機械工程學系
;
Department of Mechanical Engineering
In much previous research it has been popular to use SU-8 photoresist as a mold for electroplating, facilitating the production of low-cost microelectromechanical systems. However, the thickness of the electroplated structures standing on the substrate could only reach 50 mum or less due to the internal force and deformation of the photoresist in the final stripping process. In order to fabricate thicker structures, an embedded root method has been proposed to consolidate the adhesion of the metal structures to the substrate during the SU-8 removal process. In this paper, an experimental investigation of this method is conducted to characterize the relationship between the root depth, the linewidth and the achievable thickness of the electroplated structures. Some test patterns with embedded roots have been designed and fabricated to estimate the possible size of various structures associated with different depths of niches, which are completely defined through the SiO2 masking and KOH etching processes. Based on the established relationship between the root depth and the geometric sizes, a three-dimensional Ni coil, with a thickness of 200 mum, a width of 80 mum and a root depth of 4 mum, is successfully released by the SU-8 mold, which has a height of 400 mum. This cannot be achieved by the standard SU-8 molding process. The process parameters presented herein may be applied to the fabrication of other thick metal microstructures with similar needs.
Liquid phase deposited SiO2 on GaN
(2003-04-29)
Wu, HR
;
Lee, KW
;
Nian, TB
;
Chou, DW
;
Wu, JJH
An efficient and low cost approach to deposit uniform silicon dioxide layers on GaN by liquid phase deposition (LPD) near room temperature are described and discussed. The process is simple. GaN wafers are immersed into a H2SiF6 and H3BO3 solution to form the silicon dioxide layers. The deposition conditions and the properties of the SiO2 films will be characterized. (C) 2002 Elsevier Science B.V. All rights reserved.
Shrinkage properties of ceramic injection moulding part with a step-contracted cross-section in the filling direction
(2004)
Chen, RH
;
Ho, CH
;
Fan, HC
;
機械工程學系
;
Department of Mechanical Engineering
The need for ceramic materials in microelectromechanical systems (MEMS) is increasing quickly. A typical form of designed ceramic micro parts involves the structuring of several micro columns and/or thin walls on a substrate. This work considers the use of a model mould with a straight mould cavity and a step-contracted cross-section in the filling direction. The injection moulding of such of ceramic micro part is experimentally simulated. The effect of the mould cavity contraction ratio, moulding conditions, and the solid loading of the ceramic/binder mixture on the distribution of the transverse shrinkage of the moulding parts at moulded, debinded, and sintered stages, respectively, are examined. Experimental results reveal that transverse shrinkage of the region downstream from the step-contracted cross-section clearly exceeds that of the region upstream in all three stages. Furthermore, transverse shrinkage varies greatly in the plane of the step-contracted cross-section. The magnitude of the variation in transverse shrinkage in the step-contracted cross-section increases with the contraction ratio of the mould cavity. Appropriately increasing either the holding pressure or the filling pressure of the mould cavity reduces the variation in the transverse shrinkage of the step-contracted cross-section. Moreover, using the ceramic/binder mixture with a composition similar to that of critical solid loading can lower the internal stress caused by sintering in the vicinity of the step-contracted cross-section. (C) 2004 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Ultrathick SU-8 mold formation and removal, and its application to the fabrication of LIGA-like micromotors with embedded roots
(2002-12-01)
Ho, CH
;
Chin, KP
;
Yang, CR
;
Wu, HM
;
Chen, SL
In this study, a novel method to completely remove crosslinked SU-8 without remnants of the resist or destroying the electroplated microstructures was utilized. The LIGA-like fabrication of a side-driven electrostatic micromotor was employed as an example to describe polymerized SU-8 resist removal. Using near-UV light, nickel components of the micromotor were electroplated 160 Pm in a 300 mum-thick SU-8 mold. A comparison of various approaches based on a commercial remover was performed during the mold removal process. Experimental results showed that components having 1 mum-deep substructures embedded in the substrate could provide stronger structures to withstand the internal stress due to the photoresist deformation. In addition, when the height of the electroplated structure was below two-thirds of the photoresist mold thickness, the net clamping force on the resist could be effectively reduced to make the removal of SU-8 with heated remover successfully. The rotor and the stator with embedded roots were released cleanly and thereby, assembled to form a high-aspect-ratio micromotor. The technique of SU-8 removal and LIGA-like process presented herein can be applied to the fabrication of other high-powered microactuators. (C) 2002 Elsevier Science B.V. All rights reserved.