Conformal coating by photoresist of sharp corners of anisotropically etched through-holes in silicon

Heschel, M.; Bouwstra, S.

doi:10.1016/s0924-4247(98)00104-6

Cited by 49 publications

(32 citation statements)

References 4 publications

(5 reference statements)

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“…3D nature of the microstructure makes it very difficult to transfer the pattern [168,169,[171][172][173][174]. There are three major issues in lithography process on 3D topography: Figure 45 SEM photographs of (a) acute and (b) obtuse convex corners fabricated using triangular compensation patterns in 42.5 wt% KOH at 80°C [116].…”

Section: Perfect Convex Corners Using Two-step Etching Techniquesmentioning

confidence: 99%

A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

Pal

Sato

2015

Micro and Nano Syst Lett

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Section: Perfect Convex Corners Using Two-step Etching Techniquesmentioning

confidence: 99%

A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

Pal

Sato

2015

Micro and Nano Syst Lett

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“…However this technique provides protected convex corners, the second step of lithography is onerous as it is performed on 3D surface topography. 3D nature of the microstructure makes it very difficult to transfer the pattern [168,169,[171][172][173][174]. There are three major issues in lithography process on 3D topography: uniform photoresist coating, reflection of UV light from tilted sidewalls and the uneven gap between mask and bottom surface.…”

Section: Perfect Convex Corners Using Two-step Etching Techniquesmentioning

confidence: 99%

“…First concern is the uniform coating of photoresist using spin coating method which is most commonly used in microfabrication. Although electrodeposition can be employed to obtain uniform thickness photoresist on uneven surface, it has its own limitations [172][173][174]. The electrodeposited photoresist needs conductive base on which the photoresist electrodeposition takes place and therefore it cannot be used at all stages of a process.…”

Section: Perfect Convex Corners Using Two-step Etching Techniquesmentioning

confidence: 99%

A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

Pal¹,

Sato²

2016

Nano Online

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Wet anisotropic etching based silicon micromachining is an important technique to fabricate freestanding (e.g. cantilever) and fixed (e.g. cavity) structures on different orientation silicon wafers for various applications in microelectromechanical systems (MEMS). {111} planes are the slowest etch rate plane in all kinds of anisotropic etchants and therefore, a prolonged etching always leads to the appearance of {111} facets at the sidewalls of the fabricated structures. In wet anisotropic etching, undercutting occurs at the extruded corners and the curved edges of the mask patterns on the wafer surface. The rate of undercutting depends upon the type of etchant and the shape of mask edges and corners. Furthermore, the undercutting takes place at the straight edges if they do not contain {111} planes. {100} and {110} silicon wafers are most widely used in MEMS as well as microelectronics fabrication. This paper reviews the fabrication techniques of convex corner on {100} and {110} silicon wafers using anisotropic wet chemical etching. Fabrication methods are classified mainly into two major categories: corner compensation method and two-steps etching technique . In corner compensation method, extra mask pattern is added at the corner. Due to extra geometry, etching is delayed at the convex corner and hence the technique relies on time delayed etching. The shape and size of the compensating design strongly depends on the type of etchant, etching depth and the orientation of wafer surface. In this paper, various kinds of compensating designs published so far are discussed. Two-step etching method is employed for the fabrication of perfect convex corners. Since the perfectly sharp convex corner is formed by the intersection of {111} planes, each step of etching defines one of the facets of convex corners. In this method, two different ways are employed to perform the etching process and therefore can be subdivided into two parts. In one case, lithography step is performed after the first step of etching, while in the second case, all lithography steps are carried out before the etching process, but local oxidation of silicon (LOCOS) process is done after the first step of etching. The pros and cons of all techniques are discussed.

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“…The feedthrough interconnects are processed in three different ways [21,33,34]. The interconnects are realized as multiple feedthroughs per through-hole.…”

Section: Through-wafer Interconnectsmentioning

confidence: 99%

Multiple Through-wafer Interconnects for MEMS Applications

Heschel

Kuhmann²,

Bouwstra³

2001

Sensors Update

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This chapter reports on the design and manufacturing of multiple through-wafer interconnects for stacking of microelectromechanical devices. The feedthroughs have been applied to an interconnect (intermediate) layer for an integrated microphone. The integrated microphone consists of the transducer part and an application specific integrated circuit (ASIC). The two parts are joined by stacking them on top of each other with the interconnect (intermediate) layer between them. The intermediate layer is a multifunctional layer. It provides the microphone with an acoustic frontchamber. The intermediate layer ensures the interchange of acoustical and electrical signals with the environment. Also, the intermediate layer protects the microphone during dicing, chip handling and in operation. The two active components are electrically connected through the intermediate layer by multiple wafer frontside to backside interconnects. The feedthrough interconnects are provided with under bump metallizations (UBM), solder bumps and sealing rings on the microphone side and top surface metallizations (TSM) on the ASIC side. The entire metallization system is based on electroplating techniques. The patterning of the metallizations has been done utilizing an electrodepositable photoresist (EDPR) as a plating mold. Several EDPR processes have been developed which are optimized for the respective metallization. The feedthrough interconnects have been optimized in terms of series resistance and parallel capacitance. Electrical characterization of the feedthrough interconnects has been carried out analytically and experimentally. The series resistance of one single interconnect wire is in the order of 100 mX. The parallel (parasitic) capacitance is in the order of 2 pF. Coupling between two adjacent feedthrough interconnects is negligible for low relative humidity (<50%). For high relative humidity (>90%) the impedance between two wires may be reduced due to a condensed water film. Sensitivity measurements performed before and after bonding of the interconnect layer to the microphone showed identical results which proves sufficient (TX) isolation between the feedthrough wires.

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Conformal coating by photoresist of sharp corners of anisotropically etched through-holes in silicon

Cited by 49 publications

References 4 publications

A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

A comprehensive review on convex and concave corners in silicon bulk micromachining based on anisotropic wet chemical etching

Multiple Through-wafer Interconnects for MEMS Applications

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