Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Chapter 29Fabrication of Microelectromechanical

Devices and Systems (MEMS)

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Parts Made by Chapter 29 Processes

Figure 29.1 A gyroscope sensor used for automotive applications that combinedmechanical and electronic systems. Perhaps the most widespread use of MEMSdevices is in sensors of all kinds. Source: Courtesy of Motorola Corporation.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Bulk Micromachining

Figure 29.2 Schematic illustration of bulk micromachining. (1) Diffuse dopant indesired pattern. (2) Deposit and pattern masking film. (3) Orientation-dependentetching (ODE) leaves behind a freestanding structure. Source: Courtesy of K.R.Williams, Agilent Laboratories.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Surface Micromachining

Figure 29.3 Schematic illustration of the steps in surface micromachining: (a)deposition of a phosphosilicate glass (PSG) spacer layer; (b) etching of spacerlayer; (c) deposition of polysilicon; (d) etching of polysilicon; (e) selective wetetching of PSG, leaving the silicon and deposited polyilicon unaffected.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Microlamp

Figure 29.4 A microlamp produced from a combination of bulk and surfacemicromachining technologies. Source: Courtesy of K.R. Williams, AgilentTechnologies.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Stiction After Wet Etching

Figure 29.5 Stiction after wet etching: (1) unreleased beam; (2) unreleased beambefore drying; (3) released beam pulled to the surface by capillary forces duringdrying. Source: After B. Bhushan.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Example: Surface Micromachining of a Hinge

Figure 29.6 (a) SEM image of a deployed micromirror. (b) Detail of the micromirrorhinge. Source: Courtesy of Sandia National Laboratories.

(a)(b)

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Example: Hinge Manufacture

Figure 29.7 Schematic illustration of the steps required to manufacture a hinge. (a)Deposition of a phosphosilicate glass (PSG) layer and polysilicon layer. (b)Deposition of a second spacer layer. (c) Selective etching of the PSG. (d)Deposition of polysilicon to form a staple for the hinge. (e) After selective wetetching of the PSG, the hinge can rotate.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Digital Pixel Technology

Figure 29.8 The Texas Instrumentsdigital pixel technology device. (a)Exploded view of a single digitalmicromirror device. (b) View of twoadjacent pixels. (c) Images of DMDarrays with some mirrors removed forclarity; each micromirror measuresapproximately 17 µm (670 µin.) on aside. (d) A typical digital pixeltechnology device used for digitalprojection systems, high definitiontelevisions, and other image displaysystems. The device shown contains1,310,720 micromirrors and measuresless than 50 mm (2 in.) per side.Source: Courtesy of TexasInstruments Corporation.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Digital Pixel Technology Device Manufacture

Figure 29.9 Manufacturingsequence for the TexasInstruments DMD device.

Figure 29.10 Ceramic flat-package construction used forthe DMD device.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

SCREAM

Figure 29.11 The SCREAM process. Source: After N. Maluf.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

SIMPLE

Figure 29.12 Schematic illustration of silicon micromachining by single-stepplasma etching (SIMPLE) process.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Diffusion Bonding and DRIE

Figure 29.13 (a) Schematicillustration of silicon-diffusionbonding combined with deepreactive-ion etching to producelarge, suspended cantilevers.(b) A microfluid-flow devicemanufactured by DRIE etchingtwo separate wafers, thenaligning and silicon-diffusionbonding them together.Afterward, a Pyrex layer (notshown) is anodically bondedover the top to provide a windowto observe fluid flow. Source:(a) After N. Maluf. (b) Courtesyof K.R. Williams, AgilentTechnologies.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Thermal Inkjet Printer

Figure 29.14 Sequence of operation of a thermal inkjet printer. (a) Resistive heating element isturned on, rapidly vaporizing ink and forming a bubble. (b) Within five microseconds, the bubblehas expanded and displaced liquid ink from the nozzle. (c) Surface tension breaks the inkstream into a bubble, which is discharged at high velocity. The heating element is turned off atthis time, so that the bubble collapses as heat is transferred to the surrounding ink. (d) Within24 microseconds, an ink droplet (and undesirable satellite droplets) are ejected, and surfacetension of the ink draws more liquid from the reservoir. Source: From Tseng, F-G, "MicrodropletGenerators," in The MEMS Handbook, M. Gad-el-hak, (ed.), CRC Press, 2002.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Manufacture of Thermal Inkjet Printer Heads

Figure 29.15 The manufacturing sequence for producing thermal inkjetprinter heads. Source: From Tseng, F-G, "Microdroplet Generators," inThe MEMS Handbook, M. Gad-el-hak, (ed.), CRC Press, 2002.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

LIGA

Figure 29.16 The LIGA(lithography, electrodeposition andmolding) technique. (a) Primaryproduction of a metal final productor mold insert. (b) Use of theprimary part for secondaryoperations, or replication. Source:IMM Institute für Mikrotechnik.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Electroformed Structures

Figure 29.17 (a) Electroformed, 200 µm tall nickel structures; (b) Detail of 5 µmwide nickel lines and spaces. Source: After Todd Christenson, MEMS Handbook,CRC Press, 2002.

(a) (b)

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Micromold Manufacturing

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Example: Rare Earth Magnets

Figure 29.18 Fabrication process usedto produce rare-earth magnets formicrosensors. Source: T. Christenson,Sandia National Laboratories.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Example: Rare Earth Magnets (cont.)

Figure 29.19 SEM images of Nd2Fe14B permanent magnets. Powder particle size rangesfrom 1 to 5 µm, and the binder is a methylene-chloride resistant epoxy. Mild distortion ispresent in the image due to magnetic perturbation of the imaging electrons. Maximumenergy products of 9 MGOe have been obtained with this process. Source: T. Christenson,Sandia National Laboratories.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Wafer-Scale Diffusion Bonding

Figure 29.20 (a) Multilevel MEMS fabrication through wafer-scale diffusionbonding. (b) A suspended ring structure for measurement of tensile strain, formedby two-layer wafer-scale diffusion bonding. Source: After T. Christenson, SandiaNational Laboratories.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

HEXSIL

Figure 29.21 Illustration of theHEXagonal honeycombstructure, SILiconmicromachining and thin-filmdeposition, or HEXSILprocess.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

HEXSIL Example: Microtweezers

Figure 29.22 (a) SEM image of micro-scale tweezers used in microassembly andmicrosurgery applications. (b) Detailed view of gripper. Source: Courtesy ofMEMS Precision Instruments (memspi.com).

(a) (b)

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Instant-Masking

Figure 29.23 The instant masking process: (a) bare substrate; (b) duringdeposition, with the substrate and instant mask in contact; (c) the resulting patterndeposit. Source: After A. Cohen, MEMGen Corporation.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Case Study: Airbag Accelerometer

Figure 29.24 Schematic illustration ofa micro-acceleration sensor. Source:After N. Maluf.

Figure 29.24 Photograph of AnalogDevices’ ADXL-50 accelerometer witha surface micromachined capacitivesensor (center), on-chip excitation,self-test and signal conditioningcircuitry. The entire chip measures0.500 by 0.625 mm. Source: FromR.A. Core, et al., Solid State Technol.,pp. 39-47, October 1993

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Accelerometer Manufacture

Figure 29.26 Preparation of IC chipfor polysilicon. (a) Sensor areapost-BPSG planarization and moatmask. (b) Blanket deposition of thinoxide and thin nitride layer. (c)Bumps and anchors made in LTOspacer layer. Source: From Core,R.A., et al., Solid State Technol.,pp. 39-47, October 1993.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Accelerometer Manufacture (cont.)

Figure 29.27 Polysilicon depositionand IC metallization. (a) Cross-sectional view after polysilicondeposition, implant, anneal andpatterning. (b) Sensor area afterremoval of dielectrics from circuitarea, contact mask, and PlatinumSilicide. (c) Metallization scheme andplasma oxide passivation andpatterning. Source: From R.A. Core,et al., Solid State Technol., pp. 39-47,October 1993.

Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and Steven R. Schmid.ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

Figure 29.28 Pre-releasepreparation and release. (a) Post-plasma nitride passivation andpatterning. (b) Photo-resistprotection of the IC. (c)Freestanding, released,polysilicon beam. Source: FromCore, R.A., et al., Solid StateTechnol., pp. 39-47, October1993.

Accelerometer Manufacture (conc.)