NO870525L - RESONANCE SENSOR AND PROCEDURE FOR PRODUCING THE SAME. - Google Patents

Description

The invention relates to the field of microminiature resonator structures, especially ribbon, wire, beam, hollow beam, and cantilever-hollow beam, and double beam resonator structures and more particularly the combination of such structures with piezoelectric drive/data detection methods and - devices and manufacturing methods for

made such miniature and rni chromi ni atyr resonator structures. The piezoelectric material is deposited as a thin layer and can be activated electrically or optically.

The latest developments in microfabrication methods, including rni cr omask i ner i ng applied to discrete semiconductors and to integrated circuits (IC-r) have led to major changes in the electronic industry and have focused attention on smaller, more efficient components that can be manufactured in large scale with low cost.

Microfabrication and micromachining include the methods of planar technology, wet chemical etching and other etching methods, meta 1 1 in ser ing ng and rneta 1 1 deposition ng. Planar technology also includes the various methods used in integrated circuit production, such as photography, oxidation, thermal diffusion, i onei rnp 1 antering, chemical application and tsj.-rp 1 asrnaetsi ng.

Recognition of the need to develop rni kr osensors rned photooptical fiber and microcomponent communication and control methods in the process control industry has created an unfulfilled need for the development of compatible new components in this industry.

For the purposes of this limited description, "process control" includes both individual variable processes and complex multivariable processes that include a large number of controlled process conditions (or "measured quantities") such as flow rate, size change rate, temperature, pressure, level and the like. "Station" generally refers to a place, place, base, installation, point or locality. "Resonant structure" here generally refers to ribbon, wire, beam, hollow beam, cantilever beam and cantilever beam and double beam products and their like that can be brought into resonance at particular oscillation frequencies. As used here, "laminar" refers to morphology characterized by one or more relatively thin layers compared to the length and/or width of an object or element. When describing process steps, the component being produced can be referred to as a "work piece".

Industrial process control equipment and methods have developed over a number of years from relatively simple, individual variable pneumatic regulators for special, respectively, processes in rich ices to very large integrated systems that include analogue and digital processing equipment with sophisticated grain communication methods (telemetry ) for remote transfer of multiple process controls 1 lsi needles to and from. instead of the p.r qsesskontr.o 1 the actuator which is often a valve, switch, coupling, brake, sonoid, relay, motor or ser vorne two r or sensor.

The grain communication/telemetry process may include pneumatic, electrical, fiber optic or various other grain communication media techniques. Transforming grain communication data into energy to produce changes in the process controllable often includes linking different energy and grain communication methods. Historically, such systems were large and unwieldy and often used significant amounts of energy.

Methods of making certain resonance 1 ernents similar to those of the present invention are described in P.W. Barth, "Silicon Sensors Meet Integrated Circuits", CHEMTECH, November1382, 666-673.

Other publications of interest relating to the fabrication methods used in the present invention include: "Cadmium Sulphide and Zinc Oxide Thin Film Transducers", by N.F. Foster

et al, IEEE Transactions on Sonics "Reactive Magnetron Sputtering of ZnO", by B.T. Khuri-Yakub et al, J. Appl. Phvs. 52 (7), July 1981, pp. 4772-4774, "Zinc Oxide Film Transducers", by N.R. Foster et al, Applied Physics Letters, Vol. S, No. 9, 1.

May 1966, pp. 221-223, "Preparation of ZnO Thin Films by Sputtering of the Compound in Oxygen and Argon", by S.A. Rosgony et al, Applied Physics Letters, Vol. S, No. 9, May 1, 1966, pp. 220-

221, "Monolotich Integratad Zinc-Oxida on Silicon Pyroelectric Anernometer", by D.L. Pol la et al, IEEE IEDM S3, CH 1973-7/83/000-0639, pp. 639-642, "Thin Zinc-Oxide Film Array for Pr ogramrnab 1 e Filter and Scanned Receiving Transducers", C.T. Chung et al, IEEE 1979 LMtrasonics Symposium, IEEE CH1432-9/79/0000-0915, pp. 915-920; "Heat and Strain-Sensiti ve Thin-Film Transducers", R.S. Muller, Sensors and Actuators, 4 (Elsevier Sequoia, The Netherlands, 1983), pp. 173-182, "Piezoelectricity in Thin Film Materials", N.F. Foster, J. Acoust. Soc. Am. 70 (6), December 1981, pp. 1609-1614, "Thin-Film Integrated Sensors Respond Down to 0.1 Hz", pp. 15, 17, "The Piezoelectric Crystal as an Air Pollution Monitor", G.G. Guilbault, Plenary Lecture, pp. 637-643, and "Structure and Properties of Vacuurn-Deposited Thin Film: A Naw Basic Re 1 ationship", P.S. Vincent et al, Journal and Applied Physics, Vol. 48, No. 9, September 1977, pp. 3800-3806.

The present inventive concept includes basic miniature and rni chromium resonance structures in various designs and methods for producing them. The preferred alternative embodiments of the present invention address the need for rni ni atyr resonance structures that can be easily stimulated into oscillation and that can be mass produced by using rni kr ornask i ner i ngs and rni kr of abr i cation methods for hal we eder.

These resonance structures can take the form of a band, wire, hollow beam or hollow collar beam, double tbja 1keresonators and the like. The structures can be produced in large quantities at half--1 hour to two days. In general, the process includes first steps to deposit a thin layer of piezoelectric material and the interconnecting structures on one or more surfaces of resonant structures! during the production of this. The methods used in the production of hu 1bje1ke resonance structures are e.g. shown in US Patent Application No. 709,870, assignee's case no. TM.002, by Paul M. Zavracky, Richard Morrison and Stephan Senturia, filed Mar. 13, 1985, the teachings of which are incorporated herein by reference. One or more piezoelectric thin layers are deposited on the surface areas of the resonance structure to allow the resonance structure to be driven into oscillation. Particularly advantageous in the present invention are the methods for producing the resonance structure with the necessary thin-layer piezoelectric areas and, if desired, the electrical contacts for the piezoelectric areas. Electronic circuits can also be included in some resonator packages. Osei 1 lation of the resonance 1ement can be initiated and detected either electrically or optically.

A number of variations in the materials and structures will be apparent to those skilled in the art of process control sensors. The applicants have successfully produced effective experimental resonance band structures that include electric currents to the piezoelectric elements and in which a thin layer of zinc oxide (ZnO) serves as the piezoelectric element.

It is a purpose and an advantage of the present invention to produce a number of these resonance structures with thin-layer piezoelectric areas on a single substrate to thereby enable fast, cheap, high-volume production of these resonator components.

Another advantage of this invention is that manufacturing requires only a limited number of standard programmable microminiature resonator structure components to be manufactured for a large number of types of process control sensors.

Further purposes and advantages of inventions will be obvious from the following detailed description of the preferred alternative embodiments in connection with the accompanying sign in ng.

A number of features of the invention described here will be obvious when examining the many figures that form part of it. In all figures, the same reference numerals show corresponding parts.

Fig. 1 shows a simplified cross-section of a resonant band structure comprising a piezoelectric drive area and electrical contacts for this and shows the basic elements of the invention on it

simple read form,

fig. 2 shows a co-oscillating block resonance structure according to the present invention seen in a simplified cross-section,

fig. 3a and 3b show a double tuning fork resonance structure according to the present invention,

fig. 4a to 4g show the lamination process for producing essentially flat resonant structures, such as ribbon or double sternnegaf 1's,

fig. 5a to 5f show the plating process for producing essentially flat resonant structures, such as ribbons or double tuning forks,

fig. 6a to 6k show the process for fabricating three-dimensional resonant structures and in particular a hollow cantilever beam resonant structure,

fig. 7a to 71 show various proposed placements in pi ezoe1 ektr i ske tynsk i ktbe1 agg,

fig. Sa and Sb show proposed electrical drive and detection circuits, and

fig. 9 shows optical driving/detection for a resonant structure according to the present invention;.

Due to the many microphones in cation networks and the many applications for which micromechanical resonators according to the present invention can be used, a number of specific embodiments of the invention and examples of how they are produced are included here to illustrate the scope of the invention. Fig. 1 graphically shows the essential elements of a first embodiment of the invention, in which the resonance structure is a band element formed as a whole by microfabrication in the cation process. Fig. 2 shows a hollow beam structure according to another embodiment of the invention. Fig. 3a and 3b show a double tuning fork. A simplified cross-section of a vibrating band resonator 10 according to this invention is shown in fig. 1, where a band element 37 is tensioned between tension elements 34, 38 at one end [it should be understood that a similar device occurs (not shown) on the opposite end to stretch the band element 371 and suspended over a support structure of the substrate 31. An insulating layer 32 cover selected portions of the upper surface of the band element 37. At a desired location, an area of piezoelectric material 33 is bonded to an exposed surface area of the band element 37. A metal interface layer 36 provides an electrical connection between the upper tension element 34 and the upper main surface of the piezoelectric material 33, while the metallic strip element 37 in itself provides an electric current to the other main surface of the piezoelectric material 33. By using a periodic electric pulse via the lower clamp 33 and connecting the line 35 to the piezoelectric material, the band element 37 can be stimulated to oscillate. Correspondingly, the frequency of an oscillating band element 37 can be detected by measuring the frequency of a signal produced by stimulation of the piezoelectric feed through the connection 35 and the lower clamp 38. Note that the insulating layer 32 provides an electrical insulation between the band 1 ernent 37 and meta 1 1 in ser i ngs layer 36.

In fig. 3a and 3b there is shown a resonator of the type that is usually called an double tuning fork fa 1 12, shown e.g. on that pair of end sub1 ag or substrates 58, 61. These substrates are not necessary. Essentially, a pair of elongated longitudinal members 59 and 62 extend from the substrates so that oscillation is possible in each direction normal to the longitudinal direction of the longitudinal members or "tins" 59, 62. Dual tuning forks according to the present invention are similar to resonant bands.

It was found useful to include a resistive layer such as a rigid size limiting or blocking layer 65 in electrical series with the connections to the piezoelectric layer. For the purposes of this description, this will generally be shown between the piezoelectric material and a metallization layer included as a current to/from the piezoelectric material.

In fig. 3a and 3b, a bottom 1 agsornråde 53 can be included as desired to carry the gaf f e 1 e 1 ements 59 (62 is hidden). A piezoelectric material 54 is placed on a surface of tuning fork 1 at a desired location discussed below under microfabrication methods. Appropriate resist layer 65 is deposited on the upper surface of

the small area of. on the top plate of the double tuning fork, and then an insulating material 60 is formed to cover the main part of the surface at the end of the resonator 12. In Fig. 3b, the isolation material is indicated by reference ta11 et 60. A meta11 in the viewing layer 66 provides connection 50, 51, 52, 56 between the size-limited piezoe 1 ectric area to any external circuits as needed. 3a, 3b is deposited on an isolator sublayer as described and thus isolates the substrate 53 from the contact surfaces 51, 56, where external connections can be made for the drive/detection circuits. A channel 53 separates the two fork elements 59, 62 in the double tuning fork 1 12 Plate contacts 51, 52 provide ohmic contact to the piezoelectric material. When the double tuning fork 1s tines 59, 62 are formed on

an electrically conductive material, the contact pin must be:- 55, 57 opened in the surface of the solar layer to allow ohmic contact rned the gaf fe lal ernent. Several piezoelectric areas can be formed to facilitate driving/detection in the component. If the resonant response must be made of non-conductive material, the underlying conductive metal in the viewing layer (not shown) must be included to provide another current flow to the piezoelectric material 54.

The following is a general process for fabricating piezoelectrically driven microminiature resonant structure sensor components according to certain embodiments included in this disclosure. In general, the procedure outlines the necessary steps to produce a resonance structure sensor according to 1 amines in the thin metal foil manufacturing method according to the present invention. A number of variations will be obvious to an ordinary person skilled in the field of microfabrication. A subsequent, more detailed procedure is included and describes how band resonator structures have been successfully fabricated according to two special processes, one f o 1 i elarni ner i ng process and a plating process.

1. Selection and pretreatment of a suitable substrate.

2. Attaching the metal layer to the substrate.

3. Cleaning of exposed meta11overf1ate.

4. Photomasking of a first resist for the resonance structure by conventional methods.

5. Skimming.

6. Etching of the resonance structure using common methods.

7. Cleaning and firing of the workpiece.

S. Deposit the desired piezoelectric layer and then a rigid current-blocking layer. 9. Masking of barrier and piezoelectric layers and etching with usual methods.

10. Cloud 1 1 in ng.

11. Application of an insulating layer and meshing using the same rn ed van 1 i ge methods. 12. Set aside a conductive rneta 1 1 in se i ngsk i k t, machine and etching.

13. Remove the resonator.

Thin rneta 1 1 f o 1 i er (including nickel, copper, chromium, gold, silver, platinum, alloys of the same, and others) have both mechanical and metallurgical properties due to the manufacturing and production methods for foil. The yield strength in the Flan of the foil is hcy F-å because the grain boundaries are oriented parallel to the surface of the plane. Practical meta11 thicknesses used in the manufacture of resonant bands vary from 2 ju to 1 1 mm, with a typical value of 10 ju. Foliar thicker than 5xlO~^M does not need to be laminated to a rigid substrate. The following process steps describe the manufacture of a pair of thin, parallel band resonators of beryllium copper (BeCu) metal foil according to the present invention. See fig. 4. 1) Substrate preparation: In order to produce grain particles using p1 anar techniques, it is necessary to have a rigid specimen. The foils (e.g. less than 5x10"^ m) are not rigid, therefore not suitable on their own. To overcome this problem, a rigid substrate is used. The substrate can be of any material that has good dimensional stability, which can withstand temperatures of up to 200°C and which is essentially resistant to all etching agents used in the process. Glass is a cheap and readily available material and is available in the preferred form: 75-150 mm (3-6 inch) diameter discs. I experimental work for the present invention, 0211M cover glass, 0.25 mm (10 mil) thick, obtained from the Corning Glass Company, was used and found suitable. 2) Laminates in ngsp ro sess (Fig. 4a): The metal foil 72 must be laminated to the substrate. In the present experimental preparation of the invention, epoxide 71 was applied to the center of the substrate 70 surface and then spread out by pressing 0.013 mrn (0.5 mil) be 1 y 1 i um copper (BeCu) foil 72 between the of epoxide 71 covered substrate 70 and a flat surface More sophis labeled methods could be used. Attempts to apply the epoxy evenly by "screening" were successful, but when the foil was brought into contact, there was some difficulty. "Five-minute" epoxy from Devcon Co. was used, but a number of two-component, epoxides which harden at room temperature could also be used. Attempts to bond at elevated temperatures should be avoided due to possible failure due to thermal mismatch between the substrate and the foil (e.g. the laminate may curl at poor temperatures).

Other k leberni dde 1 types tried included instant lirn and cyanoakry1 at 1 im. Application and curing of these materials can present problems. The yarn must be able to remain unaffected during the high-temperature processes used (200°C). Epoxy was successfully tested and found suitable. A number of epoxy resins can lose their adhesive properties at elevated temperatures. The epoxy should therefore be chosen carefully to sufficiently attach the foil to the substrate, but not so effectively that it prevents the individual structures from being released.

After the 1amination step, meta11 fo1 in its 72 surface is cleaned. These cleaning steps can e.g. include immersion in an ultrasonic cleaning solution, followed by ultrasonic war rna v - ionized washing, a surface etching in dilute hydrochloric acid, and then rinsing. 3) Metal etching (see fig. 4b and 4c): Next, the lines 1 1 f o 1 in a 72 in the band elements 75, 76 are washed and etched separately to form the desired resonance structure. Resists 73, 74 are applied and exposed to a first mask to form the desired resonator pattern and then developed (fig. 4b). Other conventional washing methods can be substituted. A planar etching step can be performed to further clean the surface. The metal etch can have an adverse effect on the other parts of the component. By etching the rneta 1 1 band first (see fig. 4c and 4d) such problems are avoided. For strip material of barium 1 i urn-copper (BeCu) f er r i c-k 1 or i d (FeC 1 3) can be used as etchant. Either bowl, tank or spray etching would be suitable for use in a large-scale commercial production environment. In addition, it is possible to use a P1 asrna etch electrode, such as in onestra 1 efresi ng or spray etch i ng to reduce undercutting at the expense of a slower etch rate and therefore production.

Fig. 4d-4g shows a transverse section taken along the line D-D in fig. 4c and shows a single band 1 ernen 75 along its length, with the middle portions removed for ease of viewing. 4) Piezoelectric material deposition: Piezoelectric material 76 is deposited on the band 75. The thickness of this layer will affect the efficiency of the disorder. The range of practical thicknesses goes from 100 nm to 100 m, with a typical value of around 4 ju. a) Zinc oxide (ZnO) deposition: Sputtering (eg RF sputtering) is the preferred method for ZnO deposition, chemical vapor deposition (CVD) is an alternative process method. Equivalent methods can also be used. The temperature for the spraying process is low - 200-400°C, e.g. less than 400°C, and preferably less than 300°C. Vapor deposition can be used successfully, but this procedure requires careful control of an oxygen back pressure and of the substrate temperature during deposition. b) Carbon dioxide (CdS) deposition: Spraying is the preferred method for carbon dioxide deposition, chemical vapor deposition is an alternative method. Equivalents can also be used. During spraying, a sulfur back pressure is maintained by introducing hydrogen sulphide (H23) during the deposition. Control of the hydrogen sulphide back pressure affects the stoichiometry of the deposited layer. 5) Zinc oxide drnode 1 1 is i ng (see also step 6 below): Modeling of the zinc oxide is achieved by usual methods. It is carried out in a bowl using a solution of hydrogen peroxide (HC1) and water. The modeling step can be included in step 6. It can be spray etched to reduce undercutting. Again, drying processes can be used. Suggested patterns are shown in fig. 7. 6) Resistive barrier or so 1ator layer (see fig. 4e): A thin (typically 10-200 nm) silicon dioxide (SiO2) layer or other resistive layer on top of the zinc oxide (or kadrni umsulf - fi it) can be deposited to produce a "barrier layer" 77 to limit the electric current. The thickness of this layer should be chosen so that it does not limit the increasing Istrsmrr.en of the component at resonance to a large extent. Other insulators can be used, including non-limiting example si 1 i si umni tr i d (Si^N^) , aluminum oxide (Al 2 O 3 ) or the like, and organic insulators such as polyirnide, paralene and polytetrafluoroethylene.

Si 1 i si urndi oxy d, which can be easily processed in the laboratory, can either be deposited by spraying or electron beam deposition. It is etched in a solution of hydrofluoric acid (HF) and water. The zinc oxide and si 1 in the sium dioxide can be deposited in the same thin-film cycle, patterned once by conventional methods and then etched with hydrofluoric acid solution (for si 1 in sium dioxide) first, followed by etching the zinc oxide in a

solution of hydrochloric acid (HC1) and water.

7) Insulation layer. (fig. 4f and 4g) : The layer of insulating material 73 is deposited so that the subsequent upper meta 1 1 i se i ngssk i kt (current flow for contact connections) can be prevented from producing unwanted electrical contact to that conductive material in the band 75 or to the lower electrode (the strip metal can be used as the lower electrode) . Polyurethane has been used as an insulator because of its ability to cover wood and because it can be deposited at the lower temperatures essential for the amination process. However, other materials that can be deposited by a p 1 asrnak iron deposition process should be assessed, such as SiO-2°9SigNij. work just as well as an insulating layer. The

insulating layer 7S is generally relatively thick (10 V), so that it reduces the blind or shunt cover capacitance in the component. Experimental resonance structures were prepared with du Font P12555 po 1 y i rni d-i so 1 as j on, preheated at 90°C for 15 minutes. The polyimide is etched by the usual methods below

developing the 1 ing cycle before the positive resi st. It is then stripped of rasist as n-butyl acetate and cured at about 200°C for 1 hour.

3) Current 1 open number 1 in ser i ng (see fig. 4g): Where an electrical current to the electrical material 76 is needed (as in electrical activation/detection), aluminum (file) has been used to make conductive metal in layer 79. Other materials can also be used, examples include: chromium-silver

(Cr/Ag), ti tani um-wc 1 f ram-gu 1 1 (Ti/W/Au), platinum (Pt), chromium (Cr) and titanium (Ti). During the production of the experimental resonance structures, approximately one micron of aluminum was deposited for 1 ederrneta 1 1 in ser i nge. After usual modeling of the 1ederneta11 in section 79, it is etched in a normal aluminum urnetserni dde 1, the etching being facilitated at a somewhat elevated temperature, e.g. 50°C. It is important that it used

etchant for modeling the selected metal does not attack other parts of the component.

After the etching step, the residue is removed and the component(s) are cleaned and rinsed in deionized water. 9) Removal of the components: The components are removed from the substrate 70 and the epoxy 71 by peeling them away from the substrate with suitable tweezers. For some epoxy laminates, the substrates can be heated to about 100°C to facilitate the removal process. This reduces the adhesion of the epoxy and allows the components to be peeled away easily.

In an alternative process, the metal p1 can be etched or deposited in some other way to form the substrate for the manufacture of band resonators. The procedure is thus similar to that which uses laminated foil.

A number of materials (including, but not limited to, nickel, copper, berylium-copper alloys, chrome, gold, salve, platinum) that could be used for resonant bands can be deposited by methods such as plating, vacuum deposition or spraying. The main disadvantage of such material is that the crystal boundaries tend to orient the saw itself perpendicular to the plane of the deposited material. The yield strength of the metal in the plane can thus be expected to be lower than it could be if the grain lines were parallel to the stress. The advantages of this method, however, include a higher process temperature.

A procedure for the p 1 ether in ng/deposition method for the production of mi chrominium resonance structures follows: 1) Substrate weight: In order to produce resonance structures using photonic methods, it is desirable to have a rigid workpiece. A rigid substrate is used to provide suitable rigidity for the piece. The substrate can be made from any suitable material that has good ion stability, can withstand temperatures up to 200°C and is resistant to the etchants used in the process. Glass is a cheap, readily available material and can be obtained in the desired shape: 75-115 mm (3-6 in nch) diameter discs. 0.25 rnrn (10 mil) thick "0211" cover glass from Corning Glass Company may be used. 2) Substrate preparation: The substrate must be prepared for the application of metal1 in the viewing layer. Such a means of one type or another can be used, so that the final product can be removed from the substrate in an undamaged condition. To do this, a thin (100 nanometer) layer of copper was used experimentally. Copper is suitable because it adheres to the glass well enough to survive all the processing steps, but not so well as to prevent easy removal of the finished components from the substrates. Copper is also conductive, which allows it to be plated without the need for additional conductive layers. Alternatively, a material with poor mechanical durability, such as copper oxide, can be used as a pernid part. Germanium (Ge) also represents a useful alternative, because it is soluble in many acids and bases and has good mechanical durability during the process. It must be metallized if plating is the means of depositing resonator material a 1 et. Finally, a material such as a polymer or even an inorganic compound can be applied and later dissolved from the underside of the components. 3) Meta 1 1 deposition (see fig. 5a): The thickness of the deposited tape material itself depends on the geometry and expected stress in the component. The meta layer is deposited on the substrate with the use of suitable deposition methods, including e.g. spraying, chemical vapor deposition (CVD), thermal deposition, electron beam deposition and p 1 asrnast i mu 1 er t chemical vapor deposition. Plating and chemical vapor deposition up to several hundred n in thickness is possible man's vapor deposition (both electron beam and thermal) and sputtering is limited to about 10 ju maximum thickness. Jc higher the material's yield point, the greater the work dsf regensornåre. Nik kke 1 p 1 after i ng can better

yield strength of metallic materials.

Experimentally, a thin layer of copper 91 was deposited on a 75 mm (3 inch) diameter 0211 Corning glass substrate 90. The substrate 90 was patterned [patterning can be accomplished by conventional methods with any of a variety of resists known to those skilled in the art. rni kr of abr in the cation technique, both positive (AZ1300 series) and negative resistors have been used successfully. See fig. 5b. A positive resist, such as AZ1375, was used and spun on at low speed (2,000 turns per minute). The resist was exposed and developed so that it formed a series of bands of lines 92 on the copper-clad substrate. Two are shown. Resist stone was missing in the areas where the plated bands were to form. See fig. 5b and c. Fig. 5c is a section in the transverse direction taken along the line C-C in fig. 5b and shows a single strip element 94 along its length, with the center portions removed for ease of viewing. Plating was performed in a tank using commercially available Technics Watts nickel plating solution and current density and temperature conditions recommended by the supplier. Plating is continued to a thickness of about 12 ji. After plating, the residue was removed (in acetone), other common methods and materials could be used followed by a methanol or isopropanol

(or similar) cloud 1 liquid, followed by a water cascading cloud1-1 in ng rned avi oni serted water. The piece was then ready for piezoelectric deposition. See fig. 5d.

The process continues with the piezo1 ectr i ske material 95 cg resistance or barrier i kt 96 as in the above mentioned process in part; rn an continues from its step 4. See fig. 5e and 5f. An insulating layer 97 is applied as shown in fig. 4, followed by a suitable 1 ederrneta 1 1 in ser i ng 93. See fig. 3rd o^f. Again, finished resonance structures can be removed by rorritern<p>erature using pointed tweezers or a knife to lift the corner at one end. As soon as it is lifted, the resonator can be easily peeled off the substrate.

b) Bje 1 kestruk tours

Piezo1 ectrically driven and sensed resonant structures such as

single-ended and double-ended double-beam resonance structures (eg single-ended and double-ended tuning fork structures) can be made according to the following general method:

1. The resonance structure is made of the desired material. 2. Piezoelectric material is deposited, then modeled and etched to remove unwanted piezoelectric material from the rest of the workpiece. 3. An insulating layer can, if necessary, be deposited and fashioned. 4. A thin metallic layer is deposited and defined to provide electrical connection points for the piezoelectric circuit. 5. A thick metal layer is then deposited and defined if desired.

6. An insulating layer can be deposited if desired.

More specifically, piezoelectrically driven and sensed hollow collar-bje 1 ke resonance 1 ernents of silicon can be fabricated according to the following detailed procedure: (see Figs. 6a to 6k) 1. Si 1 i si urnsk i vernate i a 1 e of N- the type [1001 polished on both sides is a suitable material for the substrate 110. See fig. 6a. A mask layer 111 of si 1 i si urndi oxy d (S i O 2 ) is thermally grown (or equivalent) on both sides (front and back) of first and second regions (only one is shown) on a selected si 1 i si urn ( Si)-sk i ve 110 to a thickness of from 0.3 to 1.0 m, and preferably about 0.3 u. The mask layer 111 can also be formed by chemical vapor deposition (CVD), e 1 ek trcnstra 1 e (E- straw 1 a) -steaming, by spraying or by an equivalent process. Alignment markers are masked by conventional methods on the opposite side (not shown). The front oxide layer 111 on each wafer surface is modeled by conventional methods to provide a bank recess 112, an electronics cap 114 and a contact cap 115 on the front surface, and is then etched by conventional wet or dry methods

[wet electrodes include hydrofluoric acid (HF), dry electrodes include plasma etching] , preferably in hydrofluoric acid (HF) to leave precisely positioned alignment marks on the backs of each disc surface and to define

the grain components form the front over the edges of each disc face. The front surface of each disc surface then has a recess 112, an electronics cap 114 and a contact cap 115 etched on, using potassium hydroxide (KOH) or an equivalent anisotropic etchant. The recesses are etched to the correct mesh outline, e.g. the recess mask outline 113. The electronics cap 114 and/or the contact cap 115 can be omitted if they are not needed. 2. See fig. 6c, 6d and 6e. Si 1 in the sium dioxide mask layer 111 is then stripped from the respective wafer surfaces with dilute hydrofluoric acid (HF) and regrown thermally to a thickness of from about 0.5 to about 1.5 µm, preferably about 0.7 µm. 111 can also be formed by CvD, E-beam vaporization especially by spraying. This si 1 i si urndi oxy dsk i k te 111 is modeled by usual methods on each disk surface and etched in the usual way in dilute hydrofluoric acid (HF) to obtain a si 1 i si umdi oxy drnask for p+-dopetr i nnet. An undoped area 1IS (Fig. 6c) is left for later etching to release the beam. Boron (B), boron nitride (BN), boron oxide (E2O3) or ion implantation, e.g. diborane gas (B2Hg) and equivalent compounds can be used in the p + - doping step. The doped regions 116 are shown in fig. 6th. This mask 117 protects the e1 electronics area and the adjacent hat areas 114, 115 on the wafer, and also defines the p+ doping of the N-tvpa [1003 si 1 i si umornr i ss of b ja 1 kaf orm. Ornr i ssdef i ni s ion of bj e 1 k e for men u rn f ater wall tv k k e I see, sto 11 e f 1 0 y 0 m r råde r, bja1ketatation limits, etc. See US Patent Application 709,870. 3. Si 1 i si urn di oxy d dope mask i k ted 111 is stripped from both wafer surfaces with the help of hydrofluoric acid (HF) etching, and that new si 1 i si urni oxid d 111 is thermally grown over both wafer areas to a thickness of from approximately 0.2 to about 0.6 ju, preferably about 0.2 ju. The new dioxide layer can alternatively be formed by chemical vaporisation, E-beam vaporisation or by spraying. 4. Such electronics etch (see Figs. 6c and 6e) as desired on the front surface of the first wafer to form an electronics circuit board 117. Specific circuits and masks for such are known to those of ordinary skill in the art. within the technique of manufacturing integrated circuits and may in any case vary according to the intended use of the sensor. The step to form the electronics can also be skipped when not needed. 5. This new si 1 in the sium dioxide mask layer 111 (both front over1 sides of the wafer) is modeled (see fig. 6f, 6g and 6h) with a mask by usual methods, etched in hydrofluoric acid (HF) or the like, so that a contact opening is opened to the p+<->doped area 120 inside the recess 112, and so that a contact opening 119 to the p+<->doped front surface of the disc is opened in the contact area. See fig. 6f, 6g and 6h. 6. Next, the piezoelectric material is deposited using normal masking and etching methods and is etched so that the piezoelectric material 121 only remains in the . the desired indentation area of the respective disc areas. See fig. 6f, 6g and 6h. Examples of suitable piezoelectric materials include zinc oxide (ZnO), which can be etched in dilute hydrochloric acid (HCl), cadmium i urnsu 1 f i d (CdS) and lead oxide (PbO). 7. After excess piezoelectric material 121 is etched away, a thin metal layer 122 of about 0.03 to about 0.1 ju thickness, approximately 0.1 ju thick, is selectively deposited on each front surface of the disc (by definition) rned using common "lift-off" methods for photo-racist. Mata 11 the layer becomes

preferably formed of aluminum (Al), titanium (Ti), nickel (Ni), platinum (Pt), silver (Ag) or copper (Cu), or alloys of these, or similar, materials that can be processed at lower temperatures are preferred. This rneta 1 1 sk i k te 122 will be used

sorn en connect Ise's wire for the piezoe 1 ectr i ske areas (if necessary) and for connections 123, 124 to the electronics package 117 (if necessary). The photoresist is removed with acetone, N-butyl acetate or the like.

S. The front surface of the disk is then covered by a deposited high resistance [si 1 i si umni tr i d (S 131^4.) or si 1 i sium diokdis (Si 02)3 i so 1 ation layer kt kt 125. See fig. 6f, 6g and 6h. A layer of about 0.1 to 1 1 µm, preferably about 0.1 µm, thickness is suitable.

9. Contact openings 126, 127, 123 are opened in the same way as the groove-supporting layer 125 by normal masking and etching

(ordinary wet or dry electrodes) to the contact plates and a thick metal layer 129 (fli, Ti, Ni, P+, Ag, Cu) is then deposited to a thickness of about 0.5 to about 2 n and etched in the usual way as desired. See fig. 6f, 6g and 6h. This thick metal layer 129 provides contact plates 119, 127, 123 in the contactor region and is connected to the thin metal layer 122, 123, 124 and also defines the shape of the piezoelectric electrode. 10. Si 1 i si urndi oxi dsk i k tet 111 on the back is then modeled by usual methods to obtain the final etching ash. See fig. 6 i and 6 j. A tape material is then deposited on the front surface of both disc surfaces. Suitable ribbons in a 1 are described in US Patent Application 709,397. 11. The front surface of the two parts of the disc is precisely aligned and bonded together according to adjust in the ngsrners on the back, and then etched using a suitable anisotropic etchant to release the hollow beam and contactor tips. US Patent Application No. 709,870. Suitable etchants include ca 1 i um hydroxy d (KOH) , h<y>drazine (N2H4or NH2NH2) , etendi arni npyr ocatechal

(EDP) or sodium hydroxide and water (NaOH and H2O).

The ribbon stage hermetically seals the e1 electronics package.

Finally, the component is cleaned (after etching) in a water mist agent and then dried in alcohol. A slightly elevated temperature facilitates drying in the meadow.

The regions of the sensitive piezoelectric material can be placed at any of a number of locations (and combinations of locations) on the resonant structure surface, including interior surfaces of hollow structures. In addition, the piezoelectric feeder in a 1 e can be driven with electrical or optical energy, as described below. For the purposes of the following description, "excitation" of the piezoelectric mater in the a 1 areas will be understood to include either electrical or photo-optical stimulation/detection, or both, or combinations of both.

In fig. 7a and 7b, a single beam (eg ribbon) resonator component 10 is shown in plan view. Single 150 or double 151 (e.g. para!leilarranged) piezoelectric mats in a 1 areas can be deposited at one or both ends (Fig. 7a, 7b or in the middle (not shown)). Each region or dual region can serve as either a drive region or a detection region [piezoelectric materials are characterized by properties such as: a) generation of a voltage when subjected to mechanical stress and b) generation of mechanical stress when subjected to a voltage]. By using electrical or radiation energy to drive excitation out of phase with any of the piezoelectric regions or double 11 regions (or pair group) 151, the band resonator 10 in fig. 7b is oscillated in a direction parallel to that in this ground plan. Any of the remaining areas or groups of pairs can be used to generate an electrical signal for detecting the resonance frequency as an indication of the stretch on the tape. The frequency can also be detected optically. It should be noted that driving/detection can also be achieved by an initial excitation pulse of energy whose duration is significantly shorter than that of the resonance frequency, and thus detection of the resonance frequency for the remainder of the cycle or over more than one discrete oscillation cycle. These methods are generally known to those of ordinary skill in the field of process control instrumentation and well understood.

A double-ended or double tbø 1 -ges component, e.g. a so-called double tuning fork 1 12, can also be driven to oscillate and detected according to the present invention by selectively arranging piezoelectric mats in a 1deposits in shards on the branches as shown on the left side of fig. 7, one for sensing and one for detection. Piezoelectric pair array antennas can be placed along the branches, as shown on the right side of fig. 7 or 7d for more efficient driving/detection. A simple tuning fork 14 can be excited and detected by any of these methods, fig. 7y.

In fig. 7f to 7k show proposed locations for deposition of the piezoelectrically driven areas 152 on a cantilever beam resonator (not a hollow beam resonator), in which multiple deposits are made on the upper and/or lower planar surfaces of the beam, so that the beam is deflected during excitation, the excitation producing mechanical stress to generate a voltage in the remaining piezoelectric region 153.

In addition to a number of other designs of the deposited resonant structure/piezoelectric material arrangement, it should be noted that torsional buckling of an elongated structure can be achieved by placing elongated piezoelectric regions diagonally along a beam (or other resonator) surface, as shown in Fig. 7e.

In addition, membrane pressure sensors 15, as shown in cross-section in fig. 71, is driven to oscillate and then detected by arranging piezoelectric areas 150 in the membrane area 15. The membrane 15 is stored over a membrane-bare substrate 142 and exposed to a pressure F.

The resonance structures described here can also be operated and disposed of by methods and devices similar to those used for larger resonance structures known to ordinary professionals in process control engineering.

In perhaps the simplest form (see Fig. 3b), a resonant band 10 can be stretched between the clamping ends of a simple device of a material that has a high coefficient of variation such as the temperature sensor substructure 140, as shown in Fig. Sb. Correspondingly, a resonant element 16 (Fig. Sa), which can be a band, a double tuning fork 1 or other resonant structures according to this invention can be suspended under tension between a fixed point 141 and a flexible element 142 sorn, in a non-limiting example can be a membrane or bellows that senses a pressure value (P) as shown in fig. So. Hu 1 bje 1 ke structures can be filled with a variable pressure related to a measured value Cpressure, differential 1 pressure, temperature (via a filled thermal sensor) or other force! , thereby changing the resonance frequency of the memory structure.

Electrical excitation is achieved in many ways, and depends mainly on the design and arrangement of the piezoelectric material. Fig. Sa shows a basic oscillator circuit, including a phase shift circuit 143 and a winding stage 144 and has an output at 0. Fig. Sa shows a simple oscillator that uses both drive and detector piezoelectric deposits 160, 161 on a simple band sensor 10 connected between a fixed point 141 and a membrane 142 which is subjected to a pressure P.

In fig. 3b provides capacitors 147 and 143 in phase in ft, and the winding stages 146 provide the desired gain, while the piezoelectric element 160 provides the desired oscillating feedback. In some situations, it may be desirable to operate the resonance 1 ernent in a plane other than perpendicular to the plane of the deposited piezoelectric material. In such a situation, pairs of piezoelectric mats in a 1 areas can be arranged and grouped (therefore "pair groups") to provide tvarrosci11lation, portion-oscillation or oscillation in another mode. The individual piezoelectric areas of a particular pair group are simply driven out of phase to achieve the desired piezoelectric voltage. For the first time, the detector provides the area of the piezoelectric material with a voltage that varies regularly with the mechanical tension in the resonant structure. This effect can be used to feedback and maintain oscillation, as well as providing a resonant output signal, or a separate piezoelectric region can be used to generate resonant output

the turn signal.

Fig. 9 illustrates in a simple way a simple cantilever beam resonator IS, in which the beam 171 is fixed at one end to a fixed point 142, and the other end is free. A first fiber optic path 172 is driven remotely with an interrupted radiant energy beam B which excites the piezoelectric region 173 and causes the cantilever beam 171 to oscillate. A second radiation energy beam B2 is sent down another fiber optic conductor 174. The beam B2 is alternately reflected depending on the oscillations of the cantilever beam 171 and returns via the second optical fiber 174 to a remote detection location (not shown). Note that a single fiber optic conductor can be substituted for conductors 172, 174 by using separate wavelengths with limited spectral dispersion for each function - driving the piezoelectric area 173 and reflection via oscillation of the cantilever beam 171. US Patent Application 330,637 filed February 22, 19S2 by A.C. GiIby et al describe single and multi-conductor optical driving and detection methods.

Claims (1)

1. Resonance sensor element, characterized by the fact that it includes a) a resonance structure, b) devices for storing the resonance structure, d) at least one first plate of piezoelectric material having first and second surfaces, in which the first surface is in contact with resonant sensors 1 intended to vibrate the resonant sensor element, and e) drive means for causing the resonant structure to oscillate upon excitation of the first plate of piezoelectric material. 2. Resonance sensor element according to claim 1, characterized in that it also includes means for electrical contact in the piezoelectric material, where the electrical contact means is a network in the viewing layer in contact with the other surface of said piezoelectric material. 3. Resonance sensor element according to claim 1, characterized in that it also includes organs connected to resonance sensors 1 designed to reject vibration of the resonance structure. 4. Resonance sensor 1 according to claim 3, characterized in that it also comprises at least one additional plate of piezoelectric material in contact with the resonant element, in which at least eight of the additional plates of piezoelectric material are arranged to vibrate the resonance sensor structure. 5. Resonance sensor element according to claim 1, characterized in that the resonance structure is an elongated trad. 6. Resonance sensors 1 according to claim 1, characterized in that the resonance structure is a hollow beam. 7. Resonance sensor element according to claim 6, characterized in that the resonance structure is a cantilevered hollow beam. 3. Resonance sensor element according to claim 1, characterized in that the resonance structure is a double beam. 9. Resonance sensor element according to claim 1, characterized in that the means for storing the resonance structure comprise one or more compression tension means. 10. Resonance sensor element according to claim 1, characterized in that the first plate of piezoelectric material is zinc oxide (ZnO . 11. Resonance sensor element according to claim 1, characterized in that the first plate of Piezoe 1 ek tr i sic material is kadrni urnsu 1 f i d (CdS) . 12. Resonance sensor element according to claim 1, characterized in that the first plate of Piezoe 1 ektr i sic material is ga 1 i urna r seni d (GaAs) . 13. Resonance sensor element according to claim 1, characterized in that the first plate of piezoelectric material is a lead compound. 14. Resonance sensor element according to claim 1, characterized in that the drive means comprises radiant energy guided by an optical fiber path. 15. Resonance sensor element according to claim 1, characterized in that the first plate of piezoelectric material is polymer-based piezoelectric material. 16. Resonance sensor according to claim 2, characterized in that it also comprises insulating sk i ktorgans for electrical isolation of parts of the resonance structure, where the isolation layer is between the metallization layer and the resonance structure. 17. Resonance sensor element according to claim 1, characterized in that the resonance structure comprises electrically conductive surface arrays for delivering drive and detection signals to and from the piezoelectric plates. ICE. Resonance sensor element according to claim 1, characterized in that the resonance structure is an electrical insulator. 19. Resonance sensor element according to claim 4, characterized in that the first and, at least a further one of the piezoelectric material plates, are arranged near one end of the resonance structure. 20. Resonance sensor element according to claim 4, characterized in that the first and at least one of the further piezoelectric rna ter in a lp 1 ater are arranged near the respective opposite ends of the resonance structure'. 21. Resonance sensor element according to claim 1, characterized in that the drive device comprises an external electric drive circuit. 22. Resonance sensor element according to claim A3, characterized in that said means for sensing vibration comprise an electrical detection circuit. 23. Resonance sensor element according to claim 3, characterized in that the means for sensing vibration comprise an optical fiber path. 24. Resonance sensor element according to claim 3, characterized in that the means for sensing vibration is another plate of piezoelectric material which has a surface in contact with the resonance structure. 25. Resonance sensor element according to claim 1, characterized in that the resonance structure is mainly of laminar form. 26. Resonance sensor element according to claim 1, characterized in that the resonance structure is a membrane. 27. Resonance sensor element according to claim 1, characterized in that the resonance structure is a cantilevered fixed beam. 23. Method for producing a laminar resonance structure, characterized in that it includes steps for a) preparation of a substrate, b) attaching a larninary material to the substrate, c) cleaning of exposed lami close feeders in a 1 surface, d) modeling a first resist on the larni close materia I surface, e) purification of the racist, f) etching the workpiece to form a resonant structure, g) cleaning and baking of the workpiece, h) deposition of a piezoelectric layer on the work piece above the surface, i) modeling and etching the piezoelectric layer to form the piezoelectric plate, j) cleaning and rinsing the workpiece, k) application of an insulating layer on the workpiece surface and modeling of the same, 1) deposition of a conductive net 1 1 in ser i ngsk i kt on the workpiece surface and modeling and etching of the same, m) removal of the resonance structure. 29. Method according to claim 23, characterized in that the larni close material is a meta11. 30. Method according to claim 23, characterized in that the substrate is a glass. 31. Method according to claim 23, characterized in that the resonance structure formed is a band. 32. Method according to claim 23, characterized in that the resonance structure formed is a tuning fork. 33. Method according to claim 32, characterized in that the resonance structure formed is a double tuning fork 1. 34. Method according to claim 23, characterized in that the resonance structure formed is a cantilever beam. 35. Method according to claim 28, characterized in that the piezoelectric element in the ska layer is zinc oxide. 36. Method according to claim 28, characterized in that the piezoelectric layer is k ad rn i urnsu 1 f i d. 37. Method according to claim 28, characterized in that an anisotropic etching process is used for step f. 33. Method for producing a laminar resonance structure, characterized in that it includes steps for: a) preparation of a substrate, b) deposition of a rneta 1 lski kt on the substrate, c) cleaning the exposed meta11 layer transfer 1ate, d) modeling the first resist, e) purification of the racist, f) etching the workpiece to form a resonant structure, g) cleaning and firing of the workpiece, h) deposition of a piezoelectric layer on the workpiece surface, i) modeling and etching the piezoelectric layer to form a piezoelectric plate; j) cleaning and rinsing the workpiece, k) application of an insulating layer on the workpiece surface and modeling of the same, 1) deposition of a conductive metal1 in a sealing layer and modeling and etching of the same, m) removal of the resonance structure. 39. Method according to claim 33, characterized in that the laminar material is a rneta 1 1. 40. Method according to claim 33, characterized in that the substrate is a glass. 41. Method according to claim 39, characterized in that the resonance structure formed is a band. 42. Method according to claim 33, characterized in that the resonance structure formed is a tuning fork 1. 43. Method according to claim 42, characterized in that the resonance structure formed is a double tuning fork 1. 44. Method according to claim 33, characterized in that the formed resonator is a cantilever beam. 45. Method according to ten 1 claim 33, characterized in that the piezoelectric layer is a zinc oxide. 46. Method according to claim 33, characterized in that the piezoelectric layer is kadrni urnsu 1 f i d. 47. The larninary resonance structure produced according to the method in claim 23. 43. The larninary resonance structure produced according to the method in claim 38. 49. Method for producing a hu 1bje1ke resonance structure, characterized in that it includes the following tr i nn: a) etching at least one depression in the front surface of a first substrate area, b) doping a selected recess area of the first substrate area ti 1 a predetermined etch stop depth, c) deposition of a piezoelectric material in a selected one of at least one of the recess areas, d) depositing a resistive ion current barrier layer between the first substrate layer and the piezoelectric feeder in a 1 a, e) deposition of a net 1 1 in ser i ngsski ktorgan to transmit driving and detonation signals to the piezoelectric material, f) etching of at least one grain p 1 ernenterbild ldef ordypning ng in the front end-cvar f 1 stan of another substrate area, g) doping a selected recess area of the second substrate-c rn in accordance with a predetermined etch stop depth, h) alignment of the first and second substrate boards in exact accordance Isa with their respective front end substrate surfaces joined; i) banding of the joined front end substrate surfaces, and j) etching away sufficient undoped substrate from the doped substrate area to remove the doped part from the remaining substrate network in a 1 e and leave a freed, hollow microstructural cantilever block.