New and extended possibilities of orientation dependent etching in microtechnics

Hannemann, Birgit; Frühauf, Joachim

doi:10.1109/memsys.1998.659760

Cited by 4 publications

(2 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It may, therefore, be instructive to reexamine anisotropy in the light of the present results. Apparent instabilities in orientation-dependent etch rates observed by Fru ¨hauf and Hannemann in experiments with wagon-wheel masked samples, 29,30 may be due to galvanic effects. For high reliability and reproducibility in device etching, design rules, which take into account galvanic effects, are required.…”

Section: Discussionmentioning

confidence: 90%

Anisotropic Etching of Three-Dimensional Shapes in Silicon

Kretschmer

Xia

Kelly

et al. 2004

J. Electrochem. Soc.

View full text Add to dashboard Cite

As a result of the exposure to solution of different crystallographic facets during anisotropic etching of three-dimensional structures in silicon, the open-circuit potential of the semiconductor can change markedly. Using a ͑100͒Si substrate, masked to reveal ͑111͒ facets, we show that such a shift in potential can alter the chemical etch rates of the individual facets. The extent of the changes depends both on the facets exposed and on their relative areas. Because the surface geometry, and with it the silicon potential, change continuously in time, chemical etching must adapt continuously to these changes. This is an interesting example of a self-regulating system with a complex feedback mechanism. The effects described in this work clearly influence anisotropic etching ratios and are therefore important for the fabrication of microelectromechanical systems. Anisotropic etching of silicon in alkaline solutions is an important step in the technology of microelectromechanical systems ͑MEMS͒.1 Etching is employed to make high-definition, threedimensional structures in silicon wafers. These are required for a range of applications including miniature sensors for the measurement of pressure, flow, angular rate, and velocity. Other microsystems, such as filters, resonators, valves, pumps, and optomechanical connectors, can also be fabricated. The form that is obtained depends on the surface orientation of the wafer, the mask geometry, and the relative dissolution rates of the various crystallographic faces exposed during etching. The low etch rate of the ͑111͒ face with respect to that of other faces is exploited to produce deep grooves with flat walls, inverted pyramids, V-shaped grooves, and various other forms.1-3 For ͑100͒-oriented wafers, widely used in MEMS technology, the ratio of the etch rates of ͑111͒ and ͑100͒ faces, referred to here as the anisotropic ratio, is of vital importance for making high-resolution micromechanical structures. Although in the most favorable case the anisotropic ratio can exceed 100, 4 control and reproducibility at this level are poor. The composition of the etchant and the etching conditions as well as the ͑mis͒orientation of both the wafer surface and the mask edge are clearly important. Other factors which may play a role are dislocations in the silicon, defects at the silicon-mask interface, and impurities ͑even at very low concentrations͒ in the etchant.

show abstract

Section: Discussionmentioning

confidence: 90%

Anisotropic Etching of Three-Dimensional Shapes in Silicon

Kretschmer

Xia

Kelly

et al. 2004

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…Recently, some papers considered an unconventional etching technique which uses the underetching of vertical +1 0 0, silicon planes to fabricate MEMS [Chen et al (1997), Hannemann and FruK hauf (1998), Nikpour et al (1997), SchroK pfer et al (1997)]. In this paper we present a detailed investigation of this technique, mainly focusing on three topics: z description of a simple and inexpensive wet etching process which allows to fabricate perpendicular walls in 11 0 02oriented silicon z presentation of some micromachined devices fabricated by this process z discussion of advantages, disadvantages, reproducibility and limits of the etching technique, e.g., with a simulation tool for anisotropic etching.…”

Section: Introductionmentioning

confidence: 99%

Applications and simulation of unconventional bulk-micromachining using underetching of {100} silicon planes

Schropfer

Labachelerie²,

Tellier

1999

Microsystem Technologies

View full text Add to dashboard Cite

In this paper we present the principle and feasibility of bulk-micromachining using underetching of vertical +1 0 0, Silicon planes. Beside the demonstration of realized devices we investigate the fabrication reproducibility of these devices by simulating the anisotropic etching process for different cases of mask misalignment and crystal misorientation of the silicon wafer. Devices fabricated by the proposed etching technique can be reproduced within variations in mechanical performance lower than 3% if precautions such as an adapted design or pre-etching are considered.

show abstract