Construction problems in sensors

161

Sensors and Acruarors A, 28 (1991) 161-172

ConstructIon problems m sensors Vladimw

I. Vaganov

Sensoelectronrcs Laboratory, Moscow Physm Engzneermg Insnture and ECOTIXH,

Moscow (U S S R )

(Received January 22, 1991, accepted January 31, 1991)

Abstract Tlus paper attempts to grve a systematic view of construction problems m sensors First, an analysis of the mam constructional and mlcrostructurmg problems IS presented Secondly, several classlficattons of different groups of mlcromechamcal elements are dlscussed These are sensor structures, mlcroprofiles, flexible element geometries and buffer mlcroconstructlon elements Then, the problems of connectmg the mlcroconstructlon elements with the package and the external leads are consldered Fmally, a method of mlcroconstructlon design IS presented

1. Introduction

Sclentlsts workmg m the sensor field are aware of the rapid increase m new types of sensors over the last few years. According to the literature [l], one of the reasons for this growth 1s the lack of an overall view of the SUbJeCt,so that we lose our way in the sensor ‘forest’ Perhaps a more apt simile IS that of the sensor ‘lutchen-garden’, where hundreds of gardeners are cultlvatmg then own vegetables without systematically takmg note of what is happening on the next bed The system view of the subject supposes several levels. The higher levels deal with the classification of either sensor prmclples like the ‘sensor effect cube’ [l], or general problems m the sensor field [2] The lower level IS associated with the particular type of sensor, which can be characterized by a system of parameters, the descnptlon of the prmclple of operation (physical, chemical, blologlcal), the construction of the device, technology, cncmtry and metrological charactenstlcs [2]. This dlvlsion of the parameters and correspondmg problems IS not artfiaal, because all of them should be solved at different stages of design and fabrrcatlon Underestunatlon of one of these parts of the system will not result m a vegetable that is fresh, beautiful, tasty, healthy and competitive m the grocerystore!

0924-4247/91/$350

In spite of the above-mentioned growth m the number of new sensors, there IS still a large gap between a laboratory-created sensor chip and the reahzatlon of an industrially manufactured device Apparently, one of the reasons for this IS the lack of development of constructlon and microstructurmg problems, both m practice and theory Some particular aspects of this problem are considered m the literature, for example m ref 3 for implantable mtegrated sensors and m ref 4 for chemical mlcrosensors The sensitive or actuating element in most cases cannot be hermetically sealed or Isolated from the environment As IS well known, It 1s the prmclpal difference between sensors and actuators on one hand and conventional integrated circuits on the other On the contrary, the element should interact with the environment m the most rational way Therefore it requires a special sensor package, the infinite variety of measurement and control problems means that an unhmlted number of these must exist

2. Analysis of main constructional microstructure problems

and

The most obvious and unmistakable dlfference between sensors and conventlonal transducers IS their smaller size and mass

0 1991 - Etsevler Sequoia, Lausanne

162

Therefore, the problem of sensor package mmraturrzatron becomes evrdent Thts problem has several aspects [5] For those apphcatrons where a partrcular part of the transducer mountmg does not require small size and mass, mmraturtzatron of sensor packages IS stall vabd because of the general strategy of technologrcal progress the economy or rational use of resources m a broad sense Other apphcatrons where mmraturrzatron IS also a technologrcal necessrty can be dtvrded mto three classes according to the number of drmensrons which are to be mmtaturrzed A flat plate, a needle-rod and a sphere or a cube are the three extreme physrcal cases of the shape of mmrature sensor packages A typical apphcatton for the first class of package shape IS aero- or hydrodynamrc research on the surface of natural objects or therr models The catheter type of transducer IS an example for the second class of construction The thrrd shape can be effecttvely used m portable or mmtaturlzed equipment like tmplantable devices, radtopellets, etc All the extstmg sensor constructtons are mtermediate between these extreme types, and approaching one of them The considered systemahzatron of package shape does not have a pure theoretical sense but grves a key to understandmg and developing specific ways of solvmg the practrcal problems of sensor desrgn According to the basic mtcroelectromcs prmcrples, the general technologrcal conception of a sensor should be based on batch processmg of rts separate elements and construction of the whole However, not all sensor constructron elements are equally adaptable for batch processing It turns out that the most mconvement elements for thus purpose are the lomt between the mrcrostructure of the sensor chip and the package, output leads or cables and their connectton to a chtp, protection elements against envtronmental effects; the mrcropackage Itself and its assembly and also the mountmg elements Probably this ISbecause these elements of sensors have specrfic functrons m comparrson wrth the same elements of conventronal mtegrated crrcutts For example, often the Joint between the microstructure and the package should solve three problems mechanical strength, sealing, and mechanical buffering from me-

chanical and thermomechamcal strain mduced m the package In conventional KS only the first problem needs to be solved It ISknown that the problem of protectron from the envnonment m a conventtonal IC ISusually solved by total sealing of the package But the sensor constructron should provide for the dehvery of the measurand, pressure for example, to the sensttrve components At the same time, the constructron should protect the sensor from all other mfluencmg parameters, such as chemical, optrcal and radroactrve effects Often external leads or cables m sensors should be connected directly to the sensrtrve chip This 1s also not typrcal for conventtonal ICs An absolutely specrfic sensor problem IS constructmg the elements and a procedure for mdrvtdual tunmg of a sensor, for example, by trrmmmg the film resistors Therefore, the most essentral problems of sensor construction are (1) sensor mrcrostructure connection to a package, (2) cables and then connectton wrth a sensor chtp, (3) protection from the environment, (4) provrdmg mdtvrdual tuning All the exlstmg types of mtcroelectromc transducer constructions can be divided mto four classes (1) tradttronal ones, machme made wrth threaded mountmgs and mechamcal internal constructron details, (2) those based on standard packages of conventronal ICs, (3) specral packages based on IC package technology, (4) mtcrostructures (microconstructions)

3. Classification of sensor structures Sensor mtcrostructure 1s essentrally determined by the structure of the mural wafers, characterrzed by a number of criteria [6] The presence of three mam parts of the sensor chip structure, die, substrate and sensrtrve component, does not srmply detemune the number of layers of the uuttal wafer Actually m some cases all three parts can be made from the same matenal, 1e , from a umform mitral wafer In other cases the num-

163

tures wtth different types of rsolatron of the sensrttve components, which can be synthesized on the basis of the above-mentioned prmcrple of systemattzatton, are shown m Fig 1 A comparatrve analysis of the main structure 1s described elsewhere [6,7] The most promrsmg structures are of the POPOP-type Sensors based on this structure have the best metrologrcal characterrstrcs, mcludmg a wide temperature range, and the highest freedom and precision m mrcrostructure technology It mrght be pointed out here that these structures open a novel stage m sensor design and technology In fact, the three mam elements of the sensor structure mentioned above (support, substrate and sensrtrve components) play different roles and should satisfy different requirements The support, for example, should have a certam shape, which might be obtained by amsotroptc etchmg of srhcon The substrate may need to have particular mechanical properties that are also amsotroprc Finally, the transducing component sensrtrvrty 1s highly dependent on orrentatron in many cases Therefore, m a general case all three layers should be independent m terms of their crystallographic orrentatron m order to obtain the best quality based on the amsotropy of the correspondmg physical property Namely, the structures concerned possess this feature It 1s known that there are different technologies to fabricate sample (two monocrystalhne layers) SOI structures [8] Further development of these technologres, or then

POW

WKJP

Fig 1 Sensor structures component lsolatlon

with dtfferent

types of transducmg

ber of different layers m the wafer structure can reach five or seven For example, basesupport, flextble substrate element and sensrtive components are always present in prezoresrstrve pressure transducers [7] In general, all these layers can be fabricated from dtfferent materrals In this case rt mtght be necessary to use at least two more layers for connectmg the other layers together and rsolatmg them from each other Table 1 lrsts the materials commonly used and their designations and apphcatrons m sensor structures By using the sequence sensitrve component -mtermediate layer-substrate intermediate layer-support and using appropriate symbols for the layers for the desrgnatron of the sensor structure, a system of sensor structure emerges Examples of strucTABLE

1 Commonly

used materials,,

Maternal

1

their deslgnatlons Symbol

Monocrystalhne or recrystalhzed sthcon slhcon

and apphcattons

in sensor structures

Apphcatton Transducmg element

Substrate, flexible element

Suppofi

Connectmg or separatmg layer

P P+ N N+

+ + + +

+ + + +

+ + + +

+ -

2

Polycrystalhne

L

+

+

+

3

SlItcon dloxlde

0

+

+

-

4

Glass

G

+

+

+

5

Metal

M

+

+

+

+

6

Sapphire

S

-

+

+

164

combmatton, wrll create a practrcal way to fabrrcate multrlayered SO1 structures Then a new generation of sensors and mrcromechamcal devices wrll appear 4 The system of microprofiles mxromechanical

of

elements

The varrety of exrstmg mrcromechamcal constructtons can be systematrzed as a hmrted set of three-dimensional forms [9] The mlcroprofile classrficatron of these forms IS represented m Fig 2 for local non-selective and selective one-sided and double-sided etching of &con Using selectrve etching, e g , etching of the wafers with the required structure, substantrally broadens the capabrhty to create drfferent forms. It becomes possible to get more complicated shapes of mrcrostructures bridge structures with arbitrary angular ortentatron on the surface of the wafer, cantilever beams, starrhke profiles of different depths, moving parts on the hubs or axles etc The stze ratio of the dtfferent parts of mtcrostructures can vary wtthm a wide range because the mrcrodetails themselves can have srzes from several meters down to a fraction of a micrometer 5. The system of flexible element geometries The sensor chrp design includes

the fol-

lowing

d

Fig 2 The shapes of mcroprofiles obtamed by local nonsclectme (a)-(f), and selectwe (g)-(l), non-through (a), (b), (g)-(l) and through (c), (d), one-sided (a), (c), (g)-(l) and two-sided (b), (d) etchmg of s&con wafers and by bondmg two wafers to each other (e), (f)

(a) deternunatton of the shape and size of the central (thin) part of the chip, (b) determmatron of the chip geometry, (c) finding the layout of the flexible element, transducing and addttronal electronic components, contact pads and region for connecting the sensor chip with the package, (d) determmatron of the shape and srzes of the support cross section In IC sensors of mechanical parameters, the central element determmmg the chip mrcroconstructron as a whole IS a flexible element (diaphragms, beams, torstons, etc ) The classrficatton of these drfferent types of elements IS represented m Table 2, together with the references, where, according to the author’s knowledge, the corresponding sensors were first described

6. Connection of the microconstruction with the package

When solvmg the problem of mrcroconstructron connectron with the package, one should formulate (a) the general requirements for the package, mcludmg its shape and srze, (b) the requirements for the mtennedrate (buffermg) element, mcludmg its material, size and shape and the technology of its connectron with the sensor chip and the package, (d) the three-drmensronal position of the sensor chip relative to the construction elements that connect rt with the package The problems associated with the package do not require spectal consrderatron here The problems of the connecting block constructron and technology are very specrfic m comparrson with conventional ICs Nowadays the following ways of connecting a sensor chip with a package are used anodrc bonding of the sensor chip wrth either glass or s&on constructron elements (tubes, bushes, washers), which m turn should be connected with a package [42, 431, the use of low-temperature glasses [44,45], multilayer metal deposition with subsequent soldermg [46, 471, glue or cement connection [48]. The first way 1s considered to be the most wrdely used because of its known advantages It seems to be even more attractive with the devel-

165 TABLE 2 Types of flextble elements Features Layout

for sensors

of mechamcal

of shape

solId (draphragms)

Type of flexrble element

Reference

round square rectangular hexagonal octagonal comphcated

[10,11,12,13] [14,15,16] 1171 WI

WI shape

P91

cantrlever two stdes clamped comphcated wtth tethers torsronal, sample torstonal, comphcated spual

[16,20,21] WI

sohd perforated

1291 P51

bossed double bossed multr bossed

[30,31,32]

wrth concentratmg grooves wttb stram-changmg mesas

]351 1361

both srdes profiled

wtth hollow boss convoluted unrfonn beam-diaphragm convoluted non-unrform

]371 ]3gl L391 ]401

undercut

with brtdge structures trussed

[26,411 [371

perforated

Profile

parameters

flat back-stde

planar

profiled

srde profiled

etched

opment of different new technologies of sdIcon-to-srlicon bondmg hke those described m refs 49 and 50 However, the other methods, mcludmg glue connection, seem to be very far from exhaustion The recrprocal posrtron of the sensor chrp and the Intermediate elements can be formally descrrbed by a sequence of sensor constructron parameters Many of those parameters are generally Independent Therefore, different combinations of mdivrdual features are possible For example, the contact pads can be situated at the planar side of the sensor chip and the sensor die can be connected with the package from the profiled srde or vrce versa, and so on As a result of a reasonable combination of different constructron features, a system of possible construction solutions of the connectron block was synthesrzed. Some of them are shown m Fig 3, but only a few are used m practrce The 4C type of connectron 1s the most wrdely usable one Example 1C IS smtable for both absolute [51-531 and dtierentral[51,

]231 ]24,25] ]26,271 127,281

PI (33,341

541 pressure sensors. Construction 2C is quite close to that described in ref 13 and construction 3C corresponds to rt [46] The remammg types of connections can be used for specrfic apphcatrons. For example, version 5C was suggested m ref 55 7. Buffer microconstruchon elements The buffer element between a sensor chip and a package should amongst other things provide rsolatron of sensitive components from mechanical and thermomechamcal strain mduced m the package. In fact a buffermg element has to be a certain kmd of sprmg, the schematrc space posrtron of which relative to the rigrd frame of a sensor chip 1s shown m Frg 4. It can be seen that all the buffer elements can be conventionally drvrded mto two extremes: the lateral configuratron disposed parallel to the plane of a sensor chip and the vertical configuration perpendmular to the plane of a chip. On the other hand, they can be solid, provrding sealing, or per-

166

Fig 3 Dlfferent ways of connectmg packagmg element3

a sensor chip with

Rg 4 Mutual space dtspostttons of a sensor chtp and a mechamcal buffermg element

forated The first can be used m static pressure sensors where the dtvrsron of two media 1s required The second type may be useful m acceleration and vibration sensors and dynamrc pressure sensors The classification of solid buffer elements IS shown m Table 3, where they are divided mto rune classes Correspondmg references are also represented m Table 3 An example of a uniform honzontal buffer element 1s a lateral pressure sensor chrp for a catheter type of transducer, described first m ref 51 and then m refs. 52 and 56. Here the connectron with the other elements of a package can be reahzed m that part of the chip which 1s separate from the diaphragm, as shown on the drawmgs m Table 3 by dots.

The rtgrd frame around the dtaphragm happens to be relatively far from the package with Its mechamcal and thermomechamcal stresses The other horizontal buffer elements are one with two supportmg rings [57] and wtth a circular groove on the planar side of the sensor chip [40] The disadvantage of the first element IS relatively low buffering compared with the second, the dtsadvantage of which m turn IS the problem of conducting paths from the sensmve components on the draphragm to the external rigid frame, where bonding pads should preferably be placed The buffer element, which combines the posmve features of both these elements and eliminates then disadvantages, IS suggested m ref 58 and shown m Ag 5 It ISa corrugated mrcrostructure having closed grooves on both planar and back sides of a chrp The grooves on the planar side are crossed by either dams (a) or bridges (b) These dams or bridges can either be shifted relative to each other or placed on different stdes of rectangular frames The structure provides both high buffering properties and planar conductrve paths A srhcon washer [17] and mushroom-like [59] buffer elements have been known for years Recently a series of novel buffering elements was proposed [60] Versrons of the one-layer mrcrostructures of the buffer element are shown m Frg 6 Package 1 1s connected with the sensor chip 2 through the buffer element 7 The disadvantage of these structures as well as of the structure descrtbed m ref 61 1s the problem of the small size of area 12 for connecting the buffer element with the package The requnements for the quality of the package surface where it 1s connected with the buffer, and for then posmomng during bonding are very strict Twolayer buffer elements avoid thus problem Versions of these structures are shown m Fig 7. The buffer element 7 cons&s of two chips 8 and 9, which are bonded m the central part 10 of the clnps The sensor chip 2 IS bonded to a buffer element m the peripheral part 11 of the chrps The srze of area 12 for connecting the buffer element with the package 1smuch larger compared with the previous case. Thus IS the first advantage The second IS much better buffering The thud 1s that the problems of bonding two small areas are

167 TABLE

3 Clawficabon of bufferelements Draft, Reference

Combined

Draft, Reference

_. ^.. w ‘T >

r591

Vertical

Draft, Reference

Tubes Bushes

[51,52,56]

With two supporting rings

v$!j

s111con washer

'. i* lz?SI

Washers 1171

Profiled tubes

ProflIed washer

[571 Two layer proflled

Circular

Aneroid

1401

type Two layer convoluted

With planar bridges [581

solved on the wafer level, and therefore by batch processing. Further development of the described structures IS shown m Fig 8, where corrugated or convoluted springy elements are used m both buffermg chips The final solution of the proposed senes of buffers ISa multilayer microstructure shown m Fig 9 This mlcroanerold box can be useful not only as a buffer element m sensors It might find many applications m micromechamcs, for example, micropumps, microvalves and other cases where a large threednnenslonal displacement or motion is required whilst preserving the seal between or boundary of two media.

8. External leads problem The ways of solvmg the external leads problems m sensors often drlTer significantly from those used in common ICs. While solvmg these problems in sensors, the followmg aspects should be considered. the mutual positions m space of the sensor chip and external

[601

[6'Jl

wire leads; the material of the wire, the diameter and length of the leads, and the technology of electncal and mechamcal bondmg of the wires to the chip These questions and theJr dependence on both chip and package construction and technology are mterconnected. An appropriate solution can be found by combmmg the mutual dlsposltions of a sensor chip and the external wire leads as shown m Fig 10 The versions 1B and 5B are the most commonly used because they are based on standard bondmg technology Type 2B JS also used often, see, for example, [19]_ Combmations 3B and 4B are irreplaceable for mmlature transducers hke catheter-tip types The more common version 3B was described m refs. 11 and 13 and the more unusual one 4B m ref. 55 Versions 6B, 7B and 8B are mdispensable for mmiature flat sensors or for catheter-type sensors with a lateral disposltlon of the sensor chip relative to the longtudmal directlon of the catheter. Structure 6B was described in refs. 51, 52 and 56 and structure 8I3 was suggested m ref 63. Although version 7B 1s not common, it nught be useful in combmatlon with 8B for super-

168

64

I

2

7

6

12

II

FIN 6 Versions of mlcroconstmctton of one-layer chamcal buffering of a sensor chip from a package

(b) FIN 5 Microstructure of a sensor chip wth corrugated horizontal buffenng and planar path for metalhzatlon of dam we (a) and bridge type (b) external (1) and Internal (2) supportmg rmgs, flenble element (3), grooves (5, 6), planar path on dam (7, 8) and on bridge (9)

mmrature sensors, hke the 0 4 pressure sensor presented by Novasensor [64]. Comparmg the structure schemes m Frg 10 and Fig 3, one can notice that different, tf not arbitrary, mutual combmatrons of those schemes are possible Several solutions for both the connection of the sensor chip with the package and external leads problems are known (65, 661 The first ISbased on V-grooves on the planar side of a sensor chip, covered by sealed glass wrth sputtered metal pads The tunnels formed serve as a socket for the wire leads Inserted there DrlTerent bondmg technologres provrde both normal electrrcal contact and perfect mechanical strength of the connection

me-

The second one 1s shown m Frg 11 [66, 671 The sensor consists of two sihcon parts a sensor chip wrth a rectangular diaphragm and bondmg pads and a structured cover The mrcrostructure of the cover provides a chamber for the reference pressure (vacuum, for example), an overload protector and rsolated grooves over the contact pads After bonding two srhcon parts together, the mrcrosocket for either wire leads or flat microcable 1sformed The partttrons between neqhbourmg tunnels prevent undesirable electrical shorting of the bonding pads By formmg the cover from (110) srhcon, a further decrease of space for the contact pads 1s possible because the grooves have vertical walls and thinner partitions

9. Method of microconstruction design The final geometry of three-drmensronal details of the mrcrostructures that can be synthesrzed on the basis of the descrrbed mrcroprofiles also depends on a figure layout Thus the varrety of rmcrostructures that can be fabncated IS determined by the followmg

27/

26 //25

124

22\

21\\20

FIN 9 S111con mlcroanerold box as a mechamcal element m a sensor mlcroconstructlon

Fig 7 Versions of nncroconstructlon of two-layer chamcal buffermg of a sensor chip from a package

buffermg

me-

c

Rg 8 Mlcroconstructlon chamcal buffenng element

of two-layer

corrugated

me-

factors. the variety of quahtatively different forms of mlcroprofiles, choosmg the geometric proportlons of the mlcroprofile, the locahzatlon or extension of the three-dimensional figure with a certain microprofile, the layout of the figure with the required rmcroprofile, and combmations or mutual transformations of one detail mto another. Use of all the rmcroprofile variety allows quite complicated micromechamcal devices to be designed and fabncated. The method of mlcroconstruction design can be represented by the following

hg 10 Combmataons chip and the external

of mutual dlsposltlon wire leads

of a sensor

sequence of procedures, which 1s illustrated m Fig 12 (1) Macroconstruaon of device or mechamsm (prototype) bemg proposed, developed or ordered. (2) The macroconstruction IS presented as a monohthlc device wlthout traditional connectmg elements and details. (3) The number and mutual dlspositlon of closed cavities and horizontal niches are determmed

(7) The total microstructure of each layer synthesrzed on the basis of a set of technologrcally realizable mrcrodetalls (8) The materials for layers, crystallographrc orrentatron of nutlal wafers, mrcromachmmg and bonding technologies are determined (9) The layout of masks for local etching of each layer and then bonding to fabricate the finished constructron of a devrce IS destgned The further development and algonthmlzatlon of the separate stages of this sequence, which only represents a general principle, can provrde a practical basis for destgnmg a wide variety of mrcromechamcal devices IS

Fig 11 Example of constructlon solutton mvolvmg both connectlon of a sensor chip with the package and bondmg of external leads

Conclusions The rapid growth of new types of sensors, new technologres and new apphcatton areas increases the importance of selectmg partlcular solutions out of the ocean of possJbilities Thus cannot be achieved wrthout an overall VJCW of the subject Construction problems are an essential part of it Some unanswered questrons still remam, such as the systematrzatron of constructmg envrronmental protectron and provldmg mdlvtdual sensor tuning However, both problems requxe the specrfic ConsJderation of the type of measurand and the operatronal prmciple

References

Fig

12 The method

of mlcroconstructlon

design

(4) The mmtmum number of layers (wafers) needed to fabncate the whole constructron IS determined (5) The monolrthtc constructron ISrationally divided into layers A closed cavity supposes at least two layers A horizontal niche does not require a definite number of layers, but depends on the complexny of the mittal wafer structure (6) The number, geometry and mutual drsposrtron of the mrcrodetarls formmg each layer are determined

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28 J I Hansson, U S Patent No 4553 436 (Nov 1982) 29 A D Kurtz, Development dnd apphcatlon of ultrammiature pressure transducers for use m wmd tunnel model, Instrum Aerospace Ind, Voi 15, Pittsburgh, PA, 1969, pp 133-143 30 V 1 Vaganov and P P Pohvanov, Local amsotropx etching of slhcon for IC pressure sensor fabncatmg, Efectronnala Technrca, Ser II, (4) (1975) 93-98 31 A D Kurtz, J R Mallon and T A Nunn, U S Patent No 4 236 137 (Mar 1979) 32 M Shlmazoe,V Matsuka,A Yagukawaand M Tanabe, A spexlal sthcon dtaphragm pressure sensor with high output and high accuracy, Sensors and Actuators, 2 (1982) 275-282 33 L B Wdner, Sculptured pressure diaphragm, U S Patent 4 093 933 (May 1976) 34 V M Nebusov, Y V Suntzm, I K Bronstem, A E Galushkm and V N Ztmrn, USSR Parent No 1234 904 (Jul 1984) 35 V I Vaganov and G D Pqakhm, USSR Patent No 1435 967 (Jul 1985) 36 0 V Jako’lev and S M Zasedatelev, USSR Patent No 922545 (1981) 37 V I Vaganov and 1 I Sluchak, USSR Pafent No I404 852 (Jun 1989) 38 J R Mallon and A D Kurtz, Transducers employing convoluted diaphragms, US Patent No 4 467657 (Mar 1983) 39 M Bao, L Yu and Y Wang, Mlcromachmed beamdiaphragm structure improves performance of pressure transducer, Sensors and Actuators, A21-A23 (1990) 137-141 40 L K Bronstern, I K Panfiiov, Y V Snutzm, A A Sharapov and V N Shegtda, US S R Patent No 655917 (Ott 1977) 41 K Ikeda, H Kuwayama, T Kobayasht, T Watanabe, T Nlshlkawa, T Yoshlda and K Harada, Sdtwn pressure sensor Integrates resonant stram gage on diaphragm, Sensors and Actuators, A21-A23 (1990) 146150 42 G Walhs and D I Pomerantz, Field asslsted glass-metal sealing, J Appl Phys, 40 (1969) 3946 43 A D Brooks and R P Donovan, Low-temperature electrostatic sdxon-to-slhcon seals usmg sputtered borosthcate glass. J Electrochem Sot, 119 (1972) 545 44 M L Lubtmov, Metal to Glass Connection, EnergtJa, Moscow, 1968, p 270 45 A F Yurkov and V K L.eko, Transrtronal Glass and Connectwm m Electrovacuum industry, EnerglJa, Moscow, 1979, p 315 46 A C M Gteles, P F A Haans and J V Esdonk, Pressure transducer for hqulds or gases, U S Patent No 3838379 (Jan 1973) 47 W H Ko,J HymzcekandS F Boettcher,Development of a mmtature pressure transducer for bromedxal apphcatlons, IEEE Trans Electron Devrces, ED-26 (12) (1979) 1896-1905 48 A P Petrova, Thermoresutunt Glues, fimga (ChemIstry), Moscow, 1977, p 237 49 K Petersen, P Barth, J Poydock, J Brown, J Mallon and J BIyzek, Slllcon fusion bonding for pressure sensors, Tech Digest, IEEE Sohd-State Sensor Workshop, H&on Head Island, SC, USA, June 6-9, 1988, pp 144-147

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Hebuguchl, S ShoJl and M Esashl, Room-temperature anodlc bondmg with low-melrmg pomt glass film, Tech Drg, 9th Sensor Symp, Japan, 1990, pp 31-34 Research and development of IC pressure sensors for mtraheart catheterlzatlon, Frnal Repon, State Reg No 74057365, MPhEI, Moscow, 1973 T A Nunn, U S Patent No 3918019 (Mar 11, 1974) M Takahashl, T Tamgarm, K Uchlyama, H Mmortkawa, M Nlshlhdra, K Kawakaml, S Suzuki, H Hachmo and Y Mlsawa, SemIconductor absolute pressure transducer assembly and method, U S Purenf No 4 29.5 I15 (Apr 1979) N E Samek and M Mel, Diffused sdlcon wet/wet dlfferentlal pressure sensor and transducer for mmus to plus 120 “C, Sensors and Acfuabrs, A21623 (1990) 155-158 V I Vaganov and A B Noskm, USSR Patent No 788926 (Dee 1978) H Nakamura, K Tsukada and S SuguJama, U S Patent No 3968466 (Ott 1974) P P Pohvanov, Sdtcon pressure sensor chip with double frame, Pnbon I sysfem~ upravlenya (Dewces and Conrrol Systems), 7 (1979) 30-31 E J Bregman, S 0 Bntvm, V I Vaganov and A A Iophan, USSR Patent No I407348 (Ott 1986) W C Rosvold, SemIconductor transducer packaged assembly, US Patent No 4 129042 (Nov 1977) V I Vaganov, USSR Parent No 1544 1.20 (Ott 1988) H L Offerems and H Sandmarer, Novel stress free assembly technque for mlcromechanrcal devxes, Tech Digest, M~crosy~rem Technologm 90, Berlin, F R G , Sept 10-13, 1990, pp 515-520 Pressure Sensors, Mtcro Switch, a Honeywell Dwlslon, Catalog, 1984 V 1 Vaganov and A B No&m, USSR Patent No 708891 (Jul 1988) K Petersen, S&con-a material for mlcrosystems, Mrcrosysiem Technologres 90, Berlin, F RG, Sept 10-13, 1990 J B Angell, S C Terry and P W Barth, Sthcon mlcromecharun, Scr Am, 6 (1983) 4-17

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Biography Pladrmu- I Vaganov received M S and Ph D degrees in electrIca engmeermg from Moscow Physics Engmeermg Institute (MPhEI) m 1962 and 1967 respectively. In 196%1970 he worked as a scholar at Stanford Unwerslty, where he became interested m the field of sohd-state sensors Coming back to Moscow, he started developmg a research programme on plezoreslstlve sensors, sensor technology and mlcromechamcs In 1975 he was invited to carry out research at Maryland Umversity and Stanford University, and m 1981 he was chosen as Fulbrlght professor at Stanford Uruverslty Now he is the professor and chalrman of the Sensoelectrorucs Laboratory at the Moscow Physics Engmeermg Institute His present research interests are focused on mlcromecharucs, mlcrostructure design and technology m particular, and on the development of XC sensors for ddferent apphcatlons Dr Vaganov orgamzed and served as the than-man of the conference senes Mlcroelectromcs Transducers m Moscow He IS also a member of different sclentlfic councils He is an author of the book ZC Plezoreslstrve Sensors, published m 1983 m the U S S R , an author of more than 180 papers and more than 30 U S.S R patents He recently founded the ECOTECH company in Moscow for transducer manufacturing