Ch29 microeletrical fabrication Erdi Karaçal Mechanical Engineer University of Gaziantep

Chapter 29
Fabrication 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 combined
mechanical and electronic systems. Perhaps the most widespread use of MEMS
devices is in sensors of all kinds. Source: Courtesy of Motorola Corporation.

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

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 spacer
layer; (c) deposition of polysilicon; (d) etching of polysilicon; (e) selective wet
etching of PSG, leaving the silicon and deposited polyilicon unaffected.

Microlamp
Figure 29.4 A microlamp produced from a combination of bulk and surface
micromachining technologies. Source: Courtesy of K.R. Williams, Agilent
Technologies.

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

Example: Surface Micromachining of a Hinge
(a)
(b)
Figure 29.6 (a) SEM image of a deployed micromirror. (b) Detail of the micromirror
hinge. Source: Courtesy of Sandia National Laboratories.

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 wet
etching of the PSG, the hinge can rotate.

Digital Pixel Technology
Figure 29.8 The Texas Instruments
digital pixel technology device. (a)
Exploded view of a single digital
micromirror device. (b) View of two
adjacent pixels. (c) Images of DMD
arrays with some mirrors removed for
clarity; each micromirror measures
approximately 17 μm (670 μin.) on a
side. (d) A typical digital pixel
technology device used for digital
projection systems, high definition
televisions, and other image display
systems. The device shown contains
1,310,720 micromirrors and measures
less than 50 mm (2 in.) per side.
Source: Courtesy of Texas
Instruments Corporation.

Digital Pixel Technology Device Manufacture
Figure 29.9 Manufacturing
sequence for the Texas
Instruments DMD device.
Figure 29.10 Ceramic flat-package
construction used for
the DMD device.

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

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

Diffusion Bonding and DRIE
Figure 29.13 (a) Schematic
illustration of silicon-diffusion
bonding combined with deep
reactive-ion etching to produce
large, suspended cantilevers.
(b) A microfluid-flow device
manufactured by DRIE etching
two separate wafers, then
aligning and silicon-diffusion
bonding them together.
Afterward, a Pyrex layer (not
shown) is anodically bonded
over the top to provide a window
to observe fluid flow. Source:
(a) After N. Maluf. (b) Courtesy
of K.R. Williams, Agilent
Technologies.

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

Manufacture of Thermal Inkjet Printer Heads
Figure 29.15 The manufacturing sequence for producing thermal inkjet
printer heads. Source: From Tseng, F-G, "Microdroplet Generators," in
The MEMS Handbook, M. Gad-el-hak, (ed.), CRC Press, 2002.

LIGA
Figure 29.16 The LIGA
(lithography, electrodeposition and
molding) technique. (a) Primary
production of a metal final product
or mold insert. (b) Use of the
primary part for secondary
operations, or replication. Source:
IMM Institute für Mikrotechnik.

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

Micromold Manufacturing

Example: Rare Earth Magnets
Figure 29.18 Fabrication process used
to produce rare-earth magnets for
microsensors. Source: T. Christenson,
Sandia National Laboratories.

Example: Rare Earth Magnets (cont.)
Figure 29.19 SEM images of Nd2Fe14B permanent magnets. Powder particle size ranges
from 1 to 5 μm, and the binder is a methylene-chloride resistant epoxy. Mild distortion is
present in the image due to magnetic perturbation of the imaging electrons. Maximum
energy products of 9 MGOe have been obtained with this process. Source: T. Christenson,
Sandia National Laboratories.

Wafer-Scale Diffusion Bonding
Figure 29.20 (a) Multilevel MEMS fabrication through wafer-scale diffusion
bonding. (b) A suspended ring structure for measurement of tensile strain, formed
by two-layer wafer-scale diffusion bonding. Source: After T. Christenson, Sandia
National Laboratories.

HEXSIL
Figure 29.21 Illustration of the
HEXagonal honeycomb
structure, SILicon
micromachining and thin-film
deposition, or HEXSIL
process.

HEXSIL Example: Microtweezers
(a) (b)
Figure 29.22 (a) SEM image of micro-scale tweezers used in microassembly and
microsurgery applications. (b) Detailed view of gripper. Source: Courtesy of
MEMS Precision Instruments (memspi.com).

Instant-Masking
Figure 29.23 The instant masking process: (a) bare substrate; (b) during
deposition, with the substrate and instant mask in contact; (c) the resulting pattern
deposit. Source: After A. Cohen, MEMGen Corporation.

Case Study: Airbag Accelerometer
Figure 29.24 Schematic illustration of
a micro-acceleration sensor. Source:
After N. Maluf.
Figure 29.24 Photograph of Analog
Devices’ ADXL-50 accelerometer with
a surface micromachined capacitive
sensor (center), on-chip excitation,
self-test and signal conditioning
circuitry. The entire chip measures
0.500 by 0.625 mm. Source: From
R.A. Core, et al., Solid State Technol.,
pp. 39-47, October 1993

Accelerometer Manufacture
Figure 29.26 Preparation of IC chip
for polysilicon. (a) Sensor area
post-BPSG planarization and moat
mask. (b) Blanket deposition of thin
oxide and thin nitride layer. (c)
Bumps and anchors made in LTO
spacer layer. Source: From Core,
R.A., et al., Solid State Technol.,
pp. 39-47, October 1993.

Accelerometer Manufacture (cont.)
Figure 29.27 Polysilicon deposition
and IC metallization. (a) Cross-sectional
view after polysilicon
deposition, implant, anneal and
patterning. (b) Sensor area after
removal of dielectrics from circuit
area, contact mask, and Platinum
Silicide. (c) Metallization scheme and
plasma oxide passivation and
patterning. Source: From R.A. Core,
et al., Solid State Technol., pp. 39-47,
October 1993.

Accelerometer Manufacture (conc.)
Figure 29.28 Pre-release
preparation and release. (a) Post-plasma
nitride passivation and
patterning. (b) Photo-resist
protection of the IC. (c)
Freestanding, released,
polysilicon beam. Source: From
Core, R.A., et al., Solid State
Technol., pp. 39-47, October
1993.

Ch29 microeletrical fabrication Erdi Karaçal Mechanical Engineer University of Gaziantep

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