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Proceedings ArticleDOI

Low cost process for development of electrostatically actuated optical devices using gold electroplating

TL;DR: In this article, a low cost fabrication process for development of electrostatically actuated optical microstructures is presented, which consist of 1-2 micron thick micromirrors suspended at a height of 2-5 micron and surface roughness of 22-30 nm.
Abstract: This paper presents a low cost fabrication process for development of electrostatically actuated optical microstructures. To illustrate the process - a design, fabrication and measurement iteration for digital micromirror test structures is presented. The structures are fabricated on Single Crystal Silicon wafer using surface micromachining and gold electroplating. The major focus of the work has been on the process compatibility with conventional CMOS fabrication technology, lower cost, complexity, lower surface roughness and susceptibility of compliant structures to thermal cycling during the process. Thelstructures consist of 1–2 micron thick micromirrors suspended at a height of 2–5 micron and surface roughness of 22–30 nm. Vertical deflection (3 micron), pull-in voltage (31V) and mechanical resonance frequency (25 KHz) match within 5–10% to the simulated design. The approach can be extended to realize optical switches, light modulators, grating structures, barcode readers and optical scanners.
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Journal ArticleDOI
TL;DR: In this paper, it is shown that very large stresses may be present in the thin films that comprise integrated circuits and magnetic disks and that these stresses can cause deformation and fracture to occur.
Abstract: The mechanical properties of thin films on substrates are described and studied. It is shown that very large stresses may be present in the thin films that comprise integrated circuits and magnetic disks and that these stresses can cause deformation and fracture to occur. It is argued that the approaches that have proven useful in the study of bulk structural materials can be used to understand the mechanical behavior of thin film materials. Understanding the mechanical properties of thin films on substrates requires an understanding of the stresses in thin film structures as well as a knowledge of the mechanisms by which thin films deform. The fundamentals of these processes are reviewed. For a crystalline film on a nondeformable substrate, a key problem involves the movement of dislocations in the film. An analysis of this problem provides insight into both the formation of misfit dislocations in epitaxial thin films and the high strengths of thin metal films on substrates. It is demonstrated that the kinetics of dislocation motion at high temperatures are expecially important to the understanding of the formation of misfit dislocations in heteroepitaxial structures. The experimental study of mechanical properties of thin films requires the development and use of nontraditional mechanical testing techniques. Some of the techniques that have been developed recently are described. The measurement of substrate curvature by laser scanning is shown to be an effective way of measuring the biaxial stresses in thin films and studying the biaxial deformation properties at elevated temperatures. Submicron indentation testing techniques, which make use of the Nanoindenter, are also reviewed. The mechanical properties that can be studied using this instrument are described, including hardness, elastic modulus, and time-dependent deformation properties. Finally, a new testing technique involving the deflection of microbeam samples of thin film materials made by integrated circuit manufacturing methods is described. It is shown that both elastic and plastic properties of thin film materials can be measured using this technique.

2,347 citations

Journal ArticleDOI
01 Aug 1998
TL;DR: The digital display engine (DDE) as discussed by the authors is based on a single DMD device having array dimensions of 800/spl times/600 elements, illuminated by a metal halide arc lamp through a compact optics train.
Abstract: A period of rapid growth and change in the display industry has recently given rise to many new display technologies. One such technology, the Digital Micromirror Device/sup TM/ (DMD), developed at Texas Instruments, represents a unique application of microelectromechanical systems to the area of projection displays. In this paper, we describe a representative example of a DMD-based projection display engine, the digital display engine (DDE). The DDE is based on a single-DMD device having array dimensions of 800/spl times/600 elements, illuminated by a metal halide arc lamp through a compact optics train. The engine is designed for portable and fixed conference-room graphics and video display applications, and many design decisions were made to tailor the engine for its intended venue. The design of the projection engine optics and electronics is discussed, along with the basic operation, manufacture, and reliability of the DMD itself.

642 citations

Journal ArticleDOI
TL;DR: In this paper, a new type of compact optical switch using silicon micromachining technique was developed using torsion mirrors supported by thin polysilicon beams (16 /spl mu/m wide, 320 /spl m/m long, and 0.4 /spl mm/m thick) arranged in a 2/spl times/2 matrix.
Abstract: We have developed a new type of compact optical switch using silicon micromachining technique. Torsion mirrors (300 /spl mu/m/spl times/600 /spl mu/m) supported by thin polysilicon beams (16 /spl mu/m wide, 320 /spl mu/m long, and 0.4 /spl mu/m thick) are arranged in a 2/spl times/2 matrix (total size 3 mm/spl times/5 mm, t 0.3 mm). The mirrors are independently attracted by electrostatic force of applied bias voltage to redirect the incident light in a free space. Using collimated beam fibers for optical coupling, we obtained small insertion loss (/spl les/-7.66 dB), considering the length of a light path (/spl ges/10 mm), a large switching contrast (/spl ges/60 dB), and small crosstalk (/spl les/-60 dB). The fabrication yield was higher than 80% thanks to the newly developed releasing technique that used a silicon oxide diaphragm as an etch-stop layer and as a mechanical support in the process. Holding voltage (/spl les/50 V) was lower than the voltage to attract the mirror (100/spl sim/150 V) because of the hysteresis of angle-voltage characteristic of electrostatic operation.

435 citations


"Low cost process for development of..." refers methods in this paper

  • ...MEMS based micromirror devices are applications like optical display [1, 2, 3], ad Communication networks [5], MEMS scanne lithography [8] and multi-object spectroscopy fabrication reported in literature involves bul of silicon and SOI wafer [10, 11], two-wafer process assembly [12,13]....

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Journal ArticleDOI
Kurt E. Petersen1
TL;DR: This device is extremely simple to make and operate, has operational characteristics comparable to commercial magnetically driven high-frequency scanners, and has exhibited a promising reliability.
Abstract: Conventional batch photolithography and thin film techniques are employed to fabricate an electrostatically driven torsional scanning mirror from single-crystal silicon. This device is extremely simple to make and operate, has operational characteristics comparable to commercial magnetically driven high-frequency scanners, and has exhibited a promising reliability.

306 citations

Journal ArticleDOI
TL;DR: In this paper, a new class of silicon-based deformable mirrors is described, which are capable of correcting time-varying aberrations in imaging or beam forming applications.
Abstract: A new class of silicon-based deformable mirrors is described. These devices are capable of correcting time-varying aberrations in imaging or beam forming applications. Each mirror is composed of a flexible silicon membrane supported by an underlying array of electrostatic parallel plate actuators. All structural and electronic elements were fabricated through conventional surface micromachining using polycrystalline silicon thin films. A layout and fabrication design strategy for reducing nonplanar topography in multilayer micromachining was developed and used to achieve nearly flat membrane surfaces. Several deformable mirrors were characterized for their electromechanical performance. Real-time correction of optical aberrations was demonstrated using a single mirror segment connected to a closed-loop feedback control system. Undesirable mirror contours caused by residual stress gradients in the membrane were observed.

201 citations