724
`
`Integrated
`
`IEEE TRANSACTIONS ON ELECTRON DEVICES. VOL 15 NO 6. JUNE 1988
`
`Movable Micromechanical Structures for
`Sensors and Actuators
`
`Abstract-Movable pin joints, gears, springs, cranks, and slider
`structures with dimensions measured in micrometers have been fab-
`ricated using silicon microfabrication technology. These micromechan-
`ical structures, which have important transducer applications, are
`batch-fabricated in an IC-compatible process. The movable mechani-
`cal elements are built on layers that are later removed so that they are
`freed for translation and rotation. A new undercut-and-refill technique
`that makes use of the high surface mobility of silicon atoms undergoing
`chemical vapor deposition is used to refill undercut regions in order to
`form restraining Ranges. Typical element sizes and masses are mea-
`sured in millionths of a meter and billionths of a gram. The process
`provides the tiny structures in an assembled form, avoiding the nearly
`impossible challenge of handling such small elements individually.
`
`I. INTRODUCTION
`HE UNPRECEDENTED growth of integrated-circuit
`
`T technology and computing techniques has made so-
`
`phisticated data processing accurate, economical, and
`widely available. Today's electronic systems are capable
`of dealing with large numbers of physical input and output
`variables, but the transducers that provide interfaces be-
`tween the electrical and physical world are in many cases
`outmoded and dependent on awkward hybrid-fabrication
`techniques. Many of the materials and processes used to
`produce integrated microcircuits, however, can be em-
`ployed in new ways to produce microsensors and actua-
`tors. These structures complement the IC process and pro-
`vide a means to produce new electronic systems.
`Thus far, micromechanical transducer structures such
`as cantilevers, bridges, and diaphragms have been fabri-
`cated with IC-compatible processes for various useful ap-
`plications. These structures, however, contain only bend-
`able joints, a severe limitation on mechanical design
`capabilities for many applications. Microstructures with
`rotatable joints, sliding and translating members, and me-
`chanical-energy storage elements would provide the basis
`for a more general micromechanical transducer-system
`design. Because such structures add important degrees of
`freedom to designers, we have investigated techniques to
`fabricate them using IC-based microfabrication processes
`[ 11. Rotatable silicon elements, made using IC technol-
`
`ogy, have also been reported by Gabriel et al. [2]. The
`new mechanical elements use polysilicon thin-film tech-
`nology combined with techniques that we describe in this
`paper. An important advantage of the procedures de-
`scribed is that they provide mechanical structures contain-
`ing more than one part in a preassembled form; this avoids
`individually handling the very tiny structures. The initial
`demonstration of the technique to make these structures
`employs polysilicon as the structural material and phos-
`phosilicate glass for the sacrificial layer. Other materials
`may, however, be used in place of these, provided that
`they are compatible with the overall process.
`
`11. STRUCTURES AND PROCESSES
`A. Fixed-Axle Pin Joints
`A pin joint is composed of an axle around which a
`member (rotor) is free to rotate. Movement along the axle
`by the rotor is constrained by flanges. Fig. 1 shows the
`cross section and top view of a pin joint fixed to the sub-
`strate that has been fabricated using polycrystalline sili-
`con. The rotor, axle, and flange are all made of polysili-
`con that has been deposited by a low-pressure chemical-
`vapor-deposition (LPCVD) process on top of a silicon
`substrate. The pin joint is produced using a double-poly-
`silicon process and a phosphosilicate glass (PSG) sacrifi-
`cial layer in a three-mask process as indicated in Fig. 2.
`In this process, openings are first made by dry etching a
`composite layer of polysilicon on PSG deposited by se-
`quential LPCVD processes. Another PSG layer is depos-
`ited over the entire structure including the edges of the
`circular openings. Photolithography steps are then used to
`expose bare silicon at specific locations so that a subse-
`quent deposition of polysilicon will anchor to the silicon
`substrate at these desired places. After depositing and pat-
`terning the second polysilicon layer for axles and flanges,
`all previously deposited PSG layers are removed in buff-
`ered hydrofluoric acid (BHF). The remaining polysilicon
`layers form the pin-joint structure. The rotor is free to
`rotate when the PSG layer is removed by BHF. An SEM
`photo (Fig. 3 ) shows a completed pin joint of this type.
`
`Manuscript received October I , 1987; revised January 19, 1988. The
`Berkeley Sensor and Actuator Center is an NSF/Industry/University Co-
`operative Research Center. This work was partially supported by the U.S.
`Army Harry Diamond Laboratory.
`The authors are with the Berkeley Sensor and Actuator Center, Depart-
`ment of Electrical Engineering and Computer Sciences, and the Electronics
`Research Laboratory, University of California, Berkeley, CA 94720.
`IEEE Log Number 8820452.
`
`B. Self-constraining pin Joints
`A rotating-.joint structure that provides several new DOS-
`sibilities for mechanical design can be built using only a
`On the process described above. To differ-
`entiate joints of this type from the fixed-axle pin joints
`
`_ .
`
`0018-9383/88/0600-0724$01 .OO O 1988 IEEE
`
`Sony Corp. v. Raytheon Co.
`IPR2016-00209
`
`Raytheon2023-0001
`
`

`
`FAN rr id/
`
`IN1 K R A T F D MOVABLF MICROMECHANICAL STRUCTURES
`
`125
`
`1st Polyslllcon
`
`1st Polysllicon
`2nd Polysilicon
`, ,2nd PSG/ 1st PSG
`
`Fig
`
`I Top viev, dnd cro\\ section of d pol)cilicon micromechanical pin
`pint
`
`2nd PSG
`
`1st Polyslllcon
`I
`
`1st PSG
`
`6:
`
`2nd PSG
`
`2nd Polyslllcon 1st Polyslllcon
`
`I
`
`Y ” ” ” ” ’ 4
`
`Vlst PSG 2nd PSG 1st Polyslllcon
`
`Fig. 4. Fabrication process for the self-constraining joint
`
`2nd PSG
`
`2nd Polyslllcon 1st Polyslllcon
`
`Fig. 2
`
`Fabrication process for the anchored pin joint shown in Fig. 1 .
`
`Fig. 3. SEM photograph of anchored pin joint. The outer radius of the
`flange connected tu the axle is 25 Fm.
`
`described above, we call these structures self-constrain-
`ing joints. Self-constraining joints can, for example, al-
`low for rotation while, at the same time, permitting trans-
`lation across the silicon surface. These joints need to have
`a flange on the axle underneath the rotor to keep it in
`place. The axle can either be fixed to the substrate or else
`left free to translate across its surface.
`Self-constraining joints are produced by a double poly-
`silicon process with a PSG sacrificial layer. An undercut-
`and-refill technique is introduced to position the second-
`
`layer polysilicon both over and under the axle formed of
`first-layer polysilicon. Fig. 4 outlines the process for these
`joints, which are produced using two masks. In this pro-
`cess, after the PSG and polysilicon layers have been de-
`posited by LPCVD, the polysilicon is patterned by dry
`etching. The next step is to use a timed etch of the first
`PSG layer to undercut the polysilicon. An optional mask
`may be used if only selected regions are to be undercut.
`Another PSG layer is then deposited. A second polysili-
`con layer that fills in the undercut regions is the patterned
`to produce axles and flanges. After this, all PSG layers
`are removed in a buffered hydrofluoric-acid solution. The
`remaining polysilicon layers form the self-constraining
`joint structure as shown in the SEM photograph of Fig.
`5 . The interleaved polysilicon layers, evident in Fig. 4,
`can be made because of the high surface mobility of sili-
`con atoms during the LPCVD process. This permits the
`undercut regions to refill so that restraining flanges remain
`over and under the first-layer polysilicon.
`For more complex structures, both pin joints and self-
`constrained joints can be made in the same process. Fig.
`6 shows four-joint crank structures fabricated using both
`types of joints in a three-mask process (four, if the op-
`tional undercut mask is used). In Fig. 6 , the joints at both
`ends of the central element are self-constraining but they
`are freed from the substrate. The other two joints are
`pinned to the substrate. Note that, except for the fixed
`joints, the entire structure has moved from its original po-
`sition, indicated by a darkened pattern on the silicon sub-
`strate in Fig. 6 . Using a surface profiler (Alpha-Step 200),
`we have found that in the darkened pattern there is a pit
`that is roughly 100 nm deep. This pit appears to be caused
`by enhanced etching of the silicon surface by the BHF
`under the polysilicon moving elements. The enhanced
`etching may, in turn, result from localized stress in this
`region. Further research to test this hypothesis is under-
`way.
`
`Raytheon2023-0002
`
`

`
`126
`
`IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 35. NO. 6. JUNE 1988
`
`Fig. 5. SEM photograph of a self-constraining joint. The rotor is attached
`to a hub that turns in a collar projecting from a stationary polysilicon
`surface. There is a retention flange on the hub below the collar.
`
`Fig. 7. Square slider with two edges restricted by flanges. One side of the
`slider is 100 pm and the central opening is a square of IO pm.
`
`SEM photograph of a four-joint crank having a central arm
`6 .
`held
`Fig.
`sition
`r sel
`If-constrainine ioints that are free to translate. The original PO!
`b,
`of the crank is indicated by the darker pattern. All crank&ms.are 150
`pm in length.
`
`C. Flanged Structures
`The procedures carried out to make the two types of pin
`joints can be employed to produce other mechanical struc-
`tures. For example, the three-mask pin-joint process can
`be used directly to fabricate the square slider shown in
`Fig. 7. The slider has a polysilicon moving element that
`is constrained by flanges along two of its edges so that
`only translational movement in one dimension is allowed.
`In the gear-slider Combination of Fig. 8 (produced by the
`pin-joint process with four masks), the slider has a guide
`at its center to constrain movement to one dimension. Fig.
`9 shows a crank-slot combination that requires five masks
`to produce. The slot element, formed by first-layer poly-
`silicon, is pinned to the substrate by another element made
`of second-layer polysilicon so that both translational and
`rotational movements can take place. The joint for the
`crank-slot in Fig. 9 is self-constraining.
`
`D. Design Variutions
`The versatility of the techniques described permits many
`potentially useful variations in design. As an example,
`Fig. 10 is a slider that can be thought of as a dual to the
`structure in Fig. 7. The flanges holding the parts together
`
`Fig. 8. Gear and slider combination. The slider is 210 by 100 p
`The
`m.
`toothed edges mesh with four gears, two of which have flat spiral
`rings
`SP
`attached.
`
`Fig. 9. Crank-slot combination with a center pin. The slot is 130 p m long
`and 20 pm wide. The diameters of the two joints are each 50 pm.
`
`are on opposite members in each of these two versions of
`the mechanical slider. In the same sense, Fig. 11 shows
`a four-joint crank that is dual to the one in Fig. 6. All
`four joints in this crank are made using a self-constraining
`process; the two end joints are fixed and the two center
`joints can translate.
`E. Micromechanicul Bushings
`The undercut-and-refill technique is useful for other ap-
`plications also. When combined with pin joints, this tech-
`
`Raytheon2023-0003
`
`

`
`FAK e / <I/ : INTEGRATED MOVABLE MICROMECHAKICAL STRUCTURES
`
`727
`
`TOP VIEW
`
`Fig. IO. Slider structure with outer edges guided by self-constraining
`joints. Stops limit the extent of lateral motion by the slider.
`
`2nd Polysilicon<
`
`)Ist Polysilicon
`
`I
`
`.-
`
`,
`
`CROSS SECTION
`Fig. 13. Top view and cross section of flat spiral spring fixed on one end
`to an axle.
`
`made of second-layer polysilicon and connected on one
`end to the axle of a pin joint. The other end is attached to
`a movable disc made of first-layer polysilicon. The spring,
`produced using four masks, returns the disc to its original
`position after it is displaced. Figs. 14 and 15 show SEM
`photographs of restraining springs connecting rotors to
`pin-joint axles. Both springs are made of 2-pm-wide sec-
`ond-layer polysilicon. Shown in Fig. 15 is a beam spring
`that has an appreciably larger spring constant than does
`the flat spiral spring of Fig. 14.
`
`G. Processing Details
`In the foregoing, we have described the essential tech-
`niques for the in situ fabrication of assembled micro struc-
`tures. The achievable dimensions for the finished ele-
`ments depend on the lithography and processing steps
`used, but they can be roughly estimated at ten or fewer
`micrometers. Any of the microstructures can be fabri-
`cated separately using fewer than four masks. Six masks
`are needed to build all of the structures in the same run.
`When all are produced at one time there is an unavoidable
`loss in element precision because of the extra processing
`steps.
`To illustrate the processes more completely, we de-
`scribe in fuller detail the steps used to fabricate all struc-
`tures on the same chip. First, a 1.5-pm-thick phosphorus-
`doped (8 wt. %) LPCVD silicon-dioxide layer is depos-
`ited at 450°C on a (100) silicon substrate. Photolithog-
`raphy and the first mask are used to open selected areas
`on the substrate where the first-layer polysilicon is to be
`anchored. Undoped LPCVD polysilicon, 1.5 pm-thick, is
`then deposited at 630°C and patterned with a second mask
`in a CCl, plasma. The third mask is used to define the
`undercut regions for self-constraining and bushing struc-
`tures. Buffered HF etching creates a 2-ym undercut. Next,
`a 0.5-pm-thick phosphorus-doped (8 wt. %) LPCVD sil-
`
`Fig. 11. Four-joint crank made with self-constraining joints
`
`2nd PolyslllcOn
`
`I
`
`i s 1 Polysllicon
`
`i, 1
`
`Fig. 12. Cross section o f a micromechanical bushing built by the self-con-
`straining-joint process.
`
`nique permits the fabrication of bushings that can be used,
`for example, to elevate a rotor away from the silicon sur-
`face. This can greatly reduce frictional forces, especially
`if the bushing elements are coated with or made from an-
`other material such as silicon nitride that may provide bet-
`ter wear properties. Fig. 12 shows a cross section for a
`bushing produced using the self-constraining--ioint pro-
`cess described above and one extra mask for anchoring to
`the substrate (three masks in all).
`
`F. Polysilicon Springs
`Mechanical energy storage is important in many sys-
`tems, and therefore it is very desirable to be able to fab-
`ricate micromechanical springs. These elements can also
`be produced using the process described above. The flat
`spiral spring attached to a pin joint, shown in Fig. 13, is
`
`Raytheon2023-0004
`
`

`
`128
`
`IEE IE TRANSACTIONS ON ELECTRON DEVICES, VOL. 35, NO. 6, JUNE 1988
`
`Fig. 14. SEM photograph of the spring-axle structure shown in Fig. 13.
`The 2.5-revolution spiral spring is made of 2-pm-wide second-layer
`polysilicon. Its inner end is fixed to an axle IO pm in diameter, and its
`outer end is connected to a movable arm.
`
`Fig. 16. Slider and bridge structure. One end of the bridge is anchored to
`the substrate and the other is attached to a slider. The central square
`opening is 20 pm on a side and the square slider is 80 pm on a side.
`
`frictional behavior, damping, fatique limits, and of fun-
`damental properties, such as Young's modulus, Poisson's
`ratio, and the orientational dependences of these param-
`eters.
`In general, a residual stress is found in LPCVD poly-
`silicon after deposition. Previous papers [3], [4] have de-
`scribed useful ways to study uniform stress distributions.
`The stress distribution in the direction of polysilicon film
`growth is, however, very likely not to be uniform and
`therefore to induce a bending moment across the films.
`The bending moment is of special concern in cases where
`flatness is important.
`Using slider structures (Figs. 7 and lo), we expect to
`be able to separate the effects of uniform and bending
`stresses in thin-film mechanical structures. Fig. 16 shows
`the top view of a slider and a bridging beam. The outer
`edge of the flanges are defined with teeth to act as mea-
`suring scales. One end of the beam is anchored on the
`silicon substrate, and the other end is connected to a self-
`constraining slider. Since the slider allows translational
`movement, the compressive-stress component in the
`polysilicon beam can be released after freeing the whole
`structure, while the bending moment will be left in the
`beam. Detailed analytical study of such structures to de-
`termine both the compressive stress and the bending mo-
`ment in deposited polysilicon is underway.
`
`IV. FRACTURE-STRENGTH STUDY
`
`A flat spiral spring made of second-layer polysilicon is
`used to restrain a pin joint. Within its fracture limit, the
`spring can return the structure to its original position after
`it has been moved. Experiments have been done on these
`spring structures to estimate the lateral fracture stength of
`the polysilicon. A simplified mechanical analysis pro-
`vides the basis for this estimate. For a 2 pm-wide l-pm-
`thick spring extending 2.5 revolutions with inner radius
`r, = 10 pm connected to the central axle and outer radius
`r2 = 30 pm connected to one arm, fractures occur at de-
`flections of roughly 300". For a spiral spring of width h
`and thickness t , assuming that adjacent turns do not come
`
`Fig. 15. SEM photograph of a beam spring attached to a central axle. The
`beam is 60 pm long and 2 pm wide.
`
`icon-dioxide sacrificial layer is deposited at 450°C. The
`fourth and fifth masks are used to pattern the silicon-diox-
`ide layer to anchor the spring element to the substrate and
`the rotor, respectively. Undoped LPCVD polysilicon, 1 .O
`pm thick, is then deposited at 630"C, defined and pat-
`terned using the sixth mask, and eteched in a CC14 plasma.
`Prolonged etching (and therefore thick resist films) are
`required to remove completely any residue of polysilicon
`from the regions near to topographic steps. For shorter
`etching times, a more isotropic plasma such as SF6 might
`be used. A 1-h annealing step in nitrogen at 1000°C is
`used to reduce stress in the polysilicon. To release the
`structures from the oxide required 6 h of etching in a 5 : 1
`buffered HF solution.
`
`111. STUDY OF MECHANICAL PROPERTIES
`An important use for these structures is to carry out re-
`search on the micromechanical properties of materials.
`This research is especially necessary since many of the
`materials have thus far been applied exclusively for elec-
`tronics. One means for obtaining useful data is to carry
`out visual inspection of high-speed magnified video-tape
`images that show the response of dynamically actuated
`elements. Analysis of these data will permit studies of
`
`Raytheon2023-0005
`
`

`
`INTEGRATED MOVABLE MICROMECHANICAL STRUCTURES
`FAN Pf u /
`into contact, the energy stored is [SI
`M' ds
`
`u = i:=
`
`where M is the bending moment, EY is Young's modulus,
`I is the moment of inertia of the spring cross section, ds
`is the length of a small element of the spring, and 1 is the
`total length of the spiral. The spiral is generated using the
`equation r = a8 where 8 is the polar-coordinate angle and
`a is a design constant chosen for a particular spring size.
`The bending moment can be shown [5] to be constant
`along the length of the spring. The angular deflection (P
`is
`
`The moment of inertia of the rectangular cross section is
`/ = rh / 12 and the maximum stress in the spring urnax is
`Mh/2/. Using these equivalents in (2), we can express
`the maximum stress in terms of the angular deflection (P.
`
`( 3 )
`
`The spiral springs were unwound using microprobes
`until they fractured. The bending moment in the spring
`loaded in this manner is constant along its length. Spring
`fractures occurred in all cases at deflection angles of 300
`30". The fractures were observed in one or several lo-
`cations and typically more then 20 pni away from the at-
`tachment points. The spiral springs (of the type shown in
`Fig. 13). have inner and outer radii of r , = 10 pm and r2
`= 30 pm, respectively. Other parameters are: thickness r
`= 1 pm, width h = 2 pm, and spiral constant a = 1.27
`pm. Using the observed value of
`at fracture (300"
`or 5.24 radians) in (3), we calculate a fracture strength
`ulmct that is 1.7 percent times Young's modulus EY for
`thin-film polysilicon. At least two simplifying assump-
`tions underlie the conclusions made above: 1) that the
`spring motion is entirely in the horizontal plane (neglect-
`ing possible vertical motions that would relax stress), and
`2) that the spring has sufficient turns to be treated as ideal
`[6]. Other studies, still in progress, indicate a slightly
`lower fracture strength ( in the order of 1.3- 1.4 percent of
`E,). For a perspective on our results, we note that the
`highest reported fracture strength for single-crystal silicon
`is 2.6 percent times E y [7]. We expect that values for E ,
`will depend on the deposition conditions for the film and
`on the direction of the stress relative to the growth direc-
`tion.
`To estimate E , for our polysilicon films. we make use
`of Johnson's analysis IS], X-ray difl'raction studies show-
`ing the distribution of crystalline orientations in our films,
`and published orientation-dependent elastic constants for
`single-crystal silicon [ 91. Ignoring grain-boundary ef-
`fects, we estimate that EY for our films is 169 GPa and
`the fracture strength is in the 2 to 3 GPa range. For com-
`parison, Guckel and co-workers have published a value
`
`129
`
`of E , for polycrystalline silicon of 22.2 Mpsi (153 GPa)
`[lo].
`
`Polysilicon Material Studies
`An analysis to be published will detail the procedures
`sketched in the previous paragraph; we provide here only
`a few features of our studies of polycrystalline silicon to
`clarify the discussion. Using X-ray diffraction, we have
`found that the undoped LPCVD polysilicon films grown
`on PSG at 630°C have a preferred orientation that is gen-
`erally in the (1 10) direction normal to the substrate. An-
`nealing these films in nitrogen fosters grain growth but
`does not change their orientation. The polycrystalline-film
`orientation is actually described in terms of a distribution
`function derived from analysis of the X-ray diffraction
`data. This distribution function is used to calculate the
`effective film properties in terms of single-crystal param-
`eters [SI.
`
`V. CONCLUSIONS
`We have described a technique to build micro-scale
`movable mechanical pin joints, springs, gears, cranks, and
`sliders using a silicon microfabrication process. The abil-
`ity of LPCVD polysilicon to fill undercut regions has been
`utilized in this research to build new structures including
`rotating and translating joints, bushings, and sliding ele-
`ments.
`The initial demonstration of the technology has em-
`ployed polycrystalline silicon for the movable-joint mem-
`bers, but the process is not limited to using this material.
`The structural members might possibly be made from
`metals. alloys, and dielectric materials provided that these
`materials can be freed from their supporting substrate by
`selective etching of sacrificial (dissolvable) materials.
`Construction of these new elements gives rise to the need
`for research on mechanical parameters and properties for
`design. The process to produce these elements points up
`the need for further studies of sacrificial-layer etching,
`LPCVD growth, and remnant stresses in microfabricated
`systems. At the same time the realization of these struc-
`tures brings new focus on the brightening prospects for
`producing microminiature prime movers [ 111.
`The movable micromechanical structures can be batch-
`fabricated into multi-element preassembled mechanisms
`on a single substrate. or, if desired, they can be freed
`entirely from their host substrate to be assembled as sep-
`arate elements. The potential uses for this new technology
`include the production of miniature ratchets, micro-posi-
`tioning elements, mechanical logic, tuning elements, op-
`tical shutters, micro-valves, micro-pumps, and other
`mechanisms that have numberless applications in the
`macroscopic world. The method promises unheralded
`precision in the construction of miniature mechanical parts
`and systems with routine control at micrometer dimen-
`sions. Their manufacture in the world of micromechanics
`opens important avenues for further research and devel-
`opment.
`
`Raytheon2023-0006
`
`

`
`730
`
`IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 35. NO. 6. JUNE 198R
`
`ACKNOWLEDGMENT
`We thank Prof. G. Johnson for valuable discussion on
`the characterization of polycrystalline films, and K. Vo-
`ros, R. Hamilton, and the staff of the Berkeley Micro-
`fabrication Laboratory for help in experiments and fabri-
`cation.
`
`REFERENCES
`[ I ] L. S . Fan, Y. C. Tai, and R. S . Muller, “Pin-joints, springs, cranks,
`gears, and other novel micromechanical structures,” in Tech. Dig.
`4th Int. Con$ Solid-state Sensors and Actuators (Tokyo, June 1987),
`pp. 849-852 (U.S. patent pending).
`121 K. J . Gabriel, W. S . N. Trimmer, and M. Mehregany, “Micro gear
`and turbines etched from silicon,” in Tech. Dig. 4th Int. Con$ Solid-
`State Sensors and Actuators (Tokyo, June 1987). pp. 853-856.
`[3] R. T. Howe and R. S . Muller, “Stress in polycrystalline and amor-
`phous silicon thin films,” J . Appl. Phys., vol. 54, pp. 4674-4675,
`Aug. 1983.
`[4] H. Guckel, T . Randazzo, and D. W. Burns, “A simple technique for
`determination of mechanical strain in thin films with applications to
`polysilicon,”J. Appl. Phys., vol. 57, pp. 1671-1675, Mar. I , 1985.
`[SI S . Timoshenko, Strength of Materials, 3rd ed. Princeton, NJ: Van
`Nostrand, 1955.
`[6] R. P. Kroon and C. C. Davenport, “Spiral springs with small number
`of turns,” J . Franklin Insr., vol. 225, p. 171, 1938.
`171 G. L. Pearson, W. T. Read, and W . L. Feldmann, “Deformation and
`fracture of small silicon crystals,” Acta Metallurgica, vol. 5 , pp. 181-
`191, Apr. 1957.
`[8] G. C. Johnson, “Acoustoelastic response of polycrystalline aggre-
`gates exhibiting transverse isotropy,” J . Nondestructive Evaluation,
`VOI. 3, pp. 1-8, 1982.
`[9] H. J. McSkimin, W. L. Bond, E. Buehler, and G. K. Teal, ‘‘Mea-
`surement of the elastic constants of silicon single crystals and their
`thermal coefficients,” Phys. Rev. vol. 83, p. 1080, 1951.
`[IO] H. Guckel, D. W. Burns, C . R. Rutigliano, D. K. Showers, and J.
`Uglow, “Fine grained polysilicon and its application to planar pres-
`sure transducers,” in Tech. Dig. 4th Int. Con$ Solid-state Sensors
`and Actuators (Tokyo, June 1987), pp. 277-282.
`[ 1 I] R. P. Feynman, “There’s plenty of room at the bottom,” in Minia-
`turization, H. D. Gilbert, Ed. New York: Reinhold, 1961, pp. 282-
`296.
`*
`
`Long-Sheng Fan (M’88) was born in Taiwan,
`Republic of China, in 1958. He received the B.S.
`degree in electrical engineering from National
`Taiwan University, Taipei, Taiwan, Republic of
`China, in 1974 and the M.S. degree in electrical
`engineering and computer science from the Uni-
`versity of California, Berkeley, in 1984.
`He is currently working at the Berkeley Sensor
`and Actuator Center, Department of Electrical
`Engineering and Computer Sciences, University
`of California, Berkeley, on the fundamental as-
`
`pects of miniaturization and the actuation of micro-scaled machines and
`transducers for better interaction between the electronic and nonelectronic
`worlds. He served in the Chinese Air Force for his ROTC service from
`1980 to 1982. In the 1982-1983 academic year, he received a University
`of California Regents Fellowship. Since then, he has been supported by
`the Electronics Research Laboratory at UC, Berkeley, for his research. His
`major research interests are in novel devices, physics, and materials tech-
`nology.
`Mr. Fan is a member of the American Physics Society.
`*
`
`Yu-Chong Tai was born in Taiwan, Republic of
`China, on May 28. 1959. He received
`the
`B.S.E.E. degree from National Taiwan Univer-
`sity, Taiwan, in 1981, and the M.S.E.E. degree
`from the University of California, Berkeley. in
`1986. He is currently working toward the Ph.D.
`degree in the Department of Electrical Engineer-
`ing and Computer Sciences, University of Cali-
`fornia. Berkeley.
`He served in the Chinese Air Force as a Radio
`Engineer for his ROTC service from 1981 to 1983.
`His current research interests are silicon micromachining technology, poly-
`silicon material study, polysilicon micromechanics, and micromechanical
`integrated sensors such as flow sensors. accelerometers. miniature electric
`motors, and mechanical logic.
`
`*
`
`Richard S. Muller (S’57-M’62-SM‘70-F’88)
`received the degree of Mechanical Engineer from
`the Stevens Institute of Technology, Hoboken, NJ,
`and the M S /E E and Ph D degrees from the
`California Institute of Technology
`He was a Member of the Technical Staff of the
`Hughes Aircraft Company and taught at the Uni-
`versity of Southern California and the California
`Institute of Technology before joining the De-
`partment of Electrical Engineering and Computer
`Sciences at the University of California, Berke-
`ley, where he is currently a Professor and Director of the Berkeley Sensor
`and Actuator Center, a National Science Foundation/industryluniversity
`research center He is the author, together with T 1 Kamins, of DeLice
`Electronics for Inregrated Circuits, second edition (Wiley, 1986)
`Dr Muller was elected a Fellow of the IEEE for “contributions to solid-
`state sensors and to education in solid-state electronics” and was awarded
`a NATO Fellowship (1968-1969) and a Fulbright Senior Research Profes-
`sorship (1982-1983) at the Technical University, Munich, Germany He
`is Chairman of the Sensors Advisory Board for the IEEE Electron Devices
`Society. He is Chairman of the Steering Committee for the International
`Conference on Sensors and Actuators, General Chairman of the IEEE 1988
`Workshop on Sensors and Actuators, North American Chairman of
`TRANSDUCERS ’89, and General Chairman of TRANSDUCERS ’91 He
`has also served as Chairman of the Detectors, Sensors, and Displays Com-
`mittee for the International Electron Devices Meeting and is a member of
`the editorial boards for Sensors and Actuators and Sensors and Materials
`
`Raytheon2023-0007