Journal ArticleDOI
Porous polycrystalline silicon: a new material for MEMS
TLDR
In this paper, a multilayer structure of polysilicon between two layers of low-stress silicon nitride is prepared on a wafer of silicon, and a window in the outer nitride layer provides contact between the poly-silicon and the HF solution.Abstract:
A new technique for the fabrication of thin patterned layers of porous polycrystalline silicon (polysilicon) and surface micromachined structures is presented. First, a multilayer structure of polysilicon between two layers of low-stress silicon nitride is prepared on a wafer of silicon. Electrochemical anodization with an external cathode takes place in an RF solution. A window in the outer nitride layer provides contact between the polysilicon and the HF solution; the polysilicon layer contacts the substrate through openings in the lower silicon nitride layer (remote from the upper windows). Porous polysilicon growth in the lateral direction is found at rates as high as 15 /spl mu/m min/sup -1/ in 12M (25%, wgt) HF to be controlled by surface-reaction kinetics. A change in morphology occurs when either the anodic potential is raised or the HF concentration is decreased, causing the polysilicon to be electropolished. The etch front advances proportionally to the square root of time as expected for a mass-transport-controlled process. Similar behavior is observed in HF anodic reactions of single-crystal silicon. Dissolution of the polysilicon layer is confirmed using profilometry and scanning electron microscopy. Enclosed cavities (chambers surrounded by porous plugs) are formed by alternating between pore formation and uniform dissolution. Porous polysilicon also forms over a broad-area layer of polycrystalline silicon that has been deposited without overcoating the silicon wafer with a thin film of silicon nitride. The resulting porous layer may be useful for gas-absorption purposes in ultrasonic sensors. >read more
Citations
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BookDOI
The MEMS Handbook
TL;DR: In this paper, the authors present a detailed overview of the history of the field of flow simulation for MEMS and discuss the current state-of-the-art in this field.
Journal ArticleDOI
Polysilicon: a versatile material for microsystems
TL;DR: In this article, the authors look back at the development of polysilicon, its structure, fabrication and both mechanical and electrical properties, and present a wide range of successful devices.
Patent
Methods of providing an interlevel dielectric layer intermediate different elevation conductive metal layers in the fabrication of integrated circuitry
Terrence McDaniel,Max F. Hineman +1 more
TL;DR: In this article, a method of providing an interlevel dielectric layer intermediate different elevation conductive metal layers in the fabrication of integrated circuitry includes forming a conductive mesh interconnect layer over a substrate.
Patent
Microfabricated filter and shell constructed with a permeable membrane
TL;DR: In this paper, the authors describe microfabricated filters constructed with permeable polysilicon membranes for encapsulating micro-electromechanical structures (MEMS) such as micro-structures.
Journal ArticleDOI
Porous silicon as a sacrificial material
TL;DR: Porous silicon is emerging in micromachining technology as an excellent material for use as a sacrificial layer as discussed by the authors, largely due to the ease of fabrication and freedom of design it allows.
References
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Book
Diffusion: Mass Transfer in Fluid Systems
TL;DR: An overview of diffusion and separation processes brings unsurpassed, engaging clarity to this complex topic as mentioned in this paper, which is a key part of the undergraduate chemical engineering curriculum and at the core of understanding chemical purification and reaction engineering.
Journal ArticleDOI
Porosity and Pore Size Distributions of Porous Silicon Layers
TL;DR: In this article, the pore size distribution of porous silicon was investigated on different types of substrates and under different experimental conditions, and it was shown that porosity is strongly dependent on the type and resistivity of the original silicon substrate and on the electrochemical parameters used during anodization processes.
Journal ArticleDOI
An experimental and theoretical study of the formation and microstructure of porous silicon
TL;DR: In this paper, the formation and properties of porous silicon formed by anodising silicon under a wide range of conditions were investigated and the currentvoltage characteristics of the silicon-hydrofluoric acid system were presented.
Book
Polycrystalline Silicon for Integrated Circuit Applications
TL;DR: In this paper, the authors present an overview of the deposition process of polysilicon and discuss its application in a variety of applications, e.g., semiconductor manufacturing, semiconductor fabrication, and semiconductor sensor networks.