DE2749937A1 - ELECTROMECHANICAL CIRCUIT ELEMENT, IN PARTICULAR CAPACITY MEMBER, AND PROCESS FOR ITS MANUFACTURING - Google Patents

Description

27A9937 Dr. HATE Dr. FRANKE - Dr. ULLRICH

PATENT LAWYERS IN MUNICH AND HEIDELBERG

P 8O / ifO1. £. November 7, 1977

Dr F / F Munich

Wisconsin Alumni Besearch Foundation

61 '+ N. Walnut Street Madison, Wisconsin 53707 (V.St.A.)

Electromechanical circuit element, in particular capacitance element, and its method of manufacture

The invention relates generally to monocrystalline diaphragms or membranes, in particular made of silicon, which are electrostatic thanks to their Allow deformability to be used in a wide range of uses, and it relates particularly to electromechanical ones Circuit elements and especially capacitance elements and their manufacture.

In the manufacture of integrated circuits and integrated Electronic components using a substrate made of a semiconductor material such as silicon have long been sought after in circuit elements wanted that behave like coils that are compatible with the substrate material. So far, however, is still not a satisfactory one Processes have been developed for this purpose and one is therefore related to the use of macroscopic or discrete components instructed with integrated circuits.

The avoidance of such discrete components would now be of great value in reducing both the size and weight of circuits that require components with inductive behavior, and would also result in significant cost savings. The high costs of such hybrid circuits arise namely mainly from the manufacturing step of an extension or of a connector

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of the discrete components to the integrated circuits, their manufacture has already been mechanized and automated by integrated circuit technology; the elimination of this manufacturing step would therefore Considerably reduce manufacturing costs for such circuits.

The state of the art also includes membranes with a thin cross-section made of silicon or other semiconductors, but this has not yet been done it has been recognized that the electrostatic deformation of such membranes, which have certain dimensions, their use as variable capacitance, as an electromechanical resonator (by superimposing an alternating voltage via a DC voltage for the generation of the electrostatic force) or for other purposes in which a small controllable or Resonance movement of a diaphragm is useful.

In the previous technology, for example, silicon membranes are as Pressure sensors have been used, but these components have generally been made to take the form of strain gauges. This application is described, for example, in US Pat. No. 3,697,918 and US Pat. No. 3,814,998 shows silicon membranes used to form serving of a sandwich with a dielectric core, the decrease the thickness of the inner dielectric core changes the capacitance of the sandwich. In none of the previously considered applications of Diaphragms made of silicon, however, have been recognized that the application of electrostatic forces of attraction between a thin silicon membrane formed in a thin silicon plate on the one hand and a thin silicon membrane Electrode of opposite polarity, on the other hand, is able to induce both movement and electro-mechanical resonance.

In contrast, the invention is based on the object. Structures too create that both resonance behavior and controlled turning as Can show reaction to external forces.

The object set is achieved according to the invention by circuit elements, components and methods with those in the claims individual specified characteristics.

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The structures obtainable with the invention enable construction in particular of improved pressure transducers, electro-optical display devices, electromechanical resonance modules such as resonant circuits and inductive components, all of which are mechanized on the same Substrate can be obtained as conventionally manufactured integrated circuits and with techniques compatible with the current one State of the art in integrated circuit manufacture.

In this context, the invention is concerned with thin silicon membranes, which are formed in silicon layers, as they are normally used as substrates in the manufacture of integrated electronic circuits Find use. The thin membranes constructed according to the invention can be deformed by electrostatic forces and, in a wide range of applications, include the manufacture of pressure sensors Solid-state basis, of resonators and antenna structures as well as of electro-optical Insert display elements.

According to the invention and in particular according to it below in Individual preferred embodiments described can be thin membranes with a thickness in the order of a micron by selective Etch the surfaces of silicon wafers. Such membranes are responsive to the application of electrostatic forces thereby capable of physical turning.

For the further explanation of the invention and its features and advantages, reference is now made to drawing B _e , in which preferred exemplary embodiments are illustrated; show in the drawing:

1 shows the structure of a membrane in a schematic generalization according to the invention with the ability to electrostatic bending and electromechanical resonance,

2 shows a special embodiment for a valve using a thin silicon membrane according to the invention,

Fig. 3 shows a special embodiment for the use of a Membrane according to the invention for the construction of a selectively tunable tuning circuit or oscillating circuit,

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Fig. K shows a structure for determining the deflection of a membrane,

5 shows a structure according to the invention for electrostatic deformation of a membrane and

6 shows an electro-optical display cell using a thin one Silicon membrane according to the invention.

Thin membranes or diaphragms made of silicon with a manufacture and for a use according to the invention typically have a thickness of the order of a micron and can be obtained by selectively etching one or more surfaces of a thin silicon wafer of the type generally used for the manufacture of Integrated circuit substrates are in use. In a preferred mode of operation, such platelets can be prepared by diffusing boron into one of their surfaces to a depth which corresponds to the thickness desired for the particular membrane or diaphragm. The other side of the die can then be etched away following a pattern designed in the prior art for the preparation and manufacture of integrated circuits. Investigations by the applicant have shown that the diffused boron in the silicon forms a barrier for the etching process, which makes it possible to determine the thickness of the diaphragm by the depth of penetration of the boron diffused into the plate. There is no restriction to boron, and depending on the etchant used, boron or another substance that can be used as an etching retarder or etching inhibitor for the respective etchant can be used, the introduction of these substances into the silicon wafer also by other known techniques such as Growth process or ion implantation can be done. There are numerous conventional techniques for selectively etching away silicon material to a desired depth, all of which are useful and suitable in this regard. A mode of operation which has proven to be particularly favorable in practical testing will be explained in more detail below in connection with an exemplary embodiment.

Diaphragms or membranes, as they are calibrated in the manner mentioned above can be preserved, are useful for the construction of various

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directions and components or building blocks. One type of module with a very broad field of use or application spectrum uses a silicon diaphragm according to the invention as a plate or a covering of a capacitance element. Numerous shapes of conductors can be used for the second plate or electrode, and the embodiment shown in FIG. 1, in which a second silicon plate is used as the second conductor or coating of a capacitor, represents only one possible example 1, a 1 micron thick layer 30 of silicon dioxide is sandwiched between two silicon wafers 10 and 20. In the first or upper silicon wafer 10, a membrane 50 of 1 micron thickness is formed in accordance with the techniques already proposed. Immediately below this membrane 50, a portion of the layer 30 is selectively removed, so that there is a chamber or a cavity kO between the membrane 50 and the second or lower silicon wafer 20. This cavity ^ Q is of course dimensioned so that the appropriate and desired range of motion for the membrane 50 is obtained. The membrane 50 of the first silicon wafer 10 and the second silicon wafer 20 separated therefrom by the layer JQ of silicon dioxide form a capacitor across the cavity. In this construction, the membrane 50 and the second or lower silicon plate 20 form the two plates or coatings of the capacitor.

Since the structure shown in Fig. 1 gives rise to a capacitance and because the thin membrane 5O under the plant electrostatic and other Forces can be deformed, this particular structure can be used as a sensor or feeler. For example, the one shown in FIG Membrane 50 deforms itself in response to forces acting on it which then leads to a change in the spacing of the diaphragm 50 from the lower silicon wafer 20 comes. In this way, the relative distance between the plates or surfaces of the capacitor leads to a change in the total capacity of the structure. The forces for the deformation of the membrane 50 can by the expansion of a gas under changing thermal conditions or as a reaction to the pressure of acoustic waves or other forces of sufficient to deform the membrane 50

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Greatness coming about. So the membrane 5 ° can be used as force, temperature or Pressure transducers are used, the respective measured variable being related to changes in capacitance. With the help of the structure shown in FIG Numerous phenomena to be examined, which are connected with the generation of forces, can be quantified in capacitance values and their changes.

In addition to the direct mechanical aspect described above The structure shown in FIG. 1 also shows transducer behavior, electrostatic phenomena which can be used in a wide range. By applying a DC voltage as a bias voltage between the upper silicon wafer 10 and the lower silicon wafer 20 can be on the Underside of membrane 50 and on top of lower silicon wafer 20, which is etched into layer 30 of silicon dioxide Cavity * f0 are facing, a charge pattern can be formed, and this charge pattern then leads to electrostatic attraction between the membrane 50 and the lower silicon wafer 20. In certain Voltage ranges, such an electrostatic attraction is sufficient to produce a measurable and essentially linear physical deformation of the To effect membrane 50.

This mechanical movement can be illustrated in FIG Way to build a valve that can be used in response to the application of a DC voltage between a membrane 250 and a lower silicon layer 220 opens or closes. When building according to 2, the membrane 250 carries a valve body integrally formed thereon 260, which extends into a cavity 2 ^ 0 in a silicon dioxide layer 230 and, in response to a deformation of the membrane 25Ο made of silicon, seals an opening 270 in the lower silicon layer 220.

Since the deflection of the membrane 250 can be controlled very precisely by changing the electrical bias, as can be done using suitable means for monitoring the charge on the plates of the capacitor comprising the membrane 250 and the lower silicon layer 220 are shown In addition, the structure of Figure 2 can also be used as a highly accurate microactuator.

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A particular advantage of the structure shown in FIG. 1 is that it is able to show resonance behavior when the membrane 5 ° is excited by an alternating voltage in addition to the application of the direct voltage as a bias voltage. Since the mechanical deformations described above, which are caused by the electrostatic charges forming on the surfaces of the membrane 50 and the lower silicon wafer 20, can lead to mechanical fiesonanz the membrane ^ O , the structure shown in Fig. 1 as a voltage between the Electrical energy supplied to silicon wafers 10 and 20 capable of triggering mechanical resonance of the membrane 50 and maintaining it. At such frequencies, the membrane 50 vibrating in mechanical resonance acts like a tuned resonant circuit as a storage element for electrical energy. Such a resonance behavior is analogous to that of a quartz crystal, and viewed macroscopically the entire structure behaves in electrical terms at its connections essentially like an electrical resonance circuit with capacitance and inductance.

Since the process in the manufacture of a membrane or a diaphragm according to the invention is compatible with the techniques used on the same silicon wafer for the manufacture of integrated circuits and circuits, the manufacture of filters, oscillators and tuning devices that represent or require resonant circuits is therefore compatible , possible on an integrated circuit basis. An example of an application using the resonance behavior of a membrane or a diaphragm according to the invention when excited with alternating current is illustrated in FIG. The position in FIG. 3 shows a structure made of silicon wafers or wafer segments made from a solid silicon crystal which can be tuned to a number of predeterminable frequencies. The component thus obtained represents an integrated solid-state oscillating circuit or solid-state tuner. As shown in FIG. 3, the structure contains individually doped pyramids 38Q made of silicon, which are located at various points along the length of a lower silicon wafer 320 in a cavity 3 ^ 0 in a layer 33O of silicon dioxide are arranged, which separates the lower silicon wafer 320 from an upper silicon wafer JIQ , in which a membrane 350

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is trained. Electrical voltages applied to a single pyramid J&Q can cause electrostatically induced flexing of the upper diaphragm 350 made of silicon to contact a special energized pyramid 380. A suitable resonance length for the membrane 330 can be selected by selective excitation of individual pyramids. The additional application of an alternating voltage excitation to the structure of FIG. 3 between the upper silicon wafer 310 and the lower silicon wafer 320 then causes the diaphragm 350 to resonate at the selected frequency, and the entire structure works like an oscillating circuit tuned to certain frequencies.

Because the resonance shift of the electrostatically charged membranes according to the invention, the movement of an electrical charge pattern a certain frequency brings with it, the membranes and in particular the vibrating membranes can be sources of radiation and Propagation of electromagnetic signals can be used. The membrane structures therefore turn out to be very useful for the construction of very small-sized antennas that can be formed in integrated circuits together with the associated circuit. It is there It is obvious that the frequency at which such a membrane resonates is a function of external forces acting on the membrane. In this way, a resonance circuit according to the invention for Monitor or be used to implement such forces. The resonance of such structures can be controlled by the supply of external direct current energy from the outside, which makes the construction of tunable with direct voltage Filtering and changing the resonance frequency by applying a certain DC voltage level as a bias voltage to the membrane of the structure permitted. In addition to electrostatic forces, forces can also be used to act on the membranes. Pressure, from temperature changes in a gas or from the acceleration of a mass resulting in the construction of other devices such as temperature and pressure transducers or accelerometers. These structures are in turn compatible with the manufacturing techniques integrated circuits.

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Diaphragms according to the invention can be obtained from thin silicon wafers of the type which are generally used to obtain the substrate material in the manufacture ^of integrated circuits. Oils membranes are produced by first diffusing an etching retardant such as boron into the plate to a depth corresponding to the thickness required for the diaphragm to be produced. Subsequently, the wafer is then covered on its entry surface for the diffusion of the Atzverzogerungsmittels opposite surface with a mask, that the subsequent application of a ^w embran leads from etchant to form the appropriate size. An etching process that has proven to be useful in practical testing is by CL Huange and T. van Duser in an article entitled "Single Crystal Silicon Barrier Josephson Junctions" in volume MAG-11 of IEEE Transactions on Magnetics of March 2, 1975, page 766 , has been described.

Typical dimensions for the membranes are included 0.8 cm square, i.e. 0.8 cm side length, and in thickness between 2 and 4 microns. Experimental testing has shown that such membranes or diaphragms are applied in a substantially linear manner Address forces. For example, one experiment made a membrane with the general dimensions 0.8 cm square and 2-4 microns thick attached with wax to a polished steel plate so that a hole in the steel plate was directly under the membrane, as shown in Fig. 4 is shown. The illustration in FIG. 4 shows a membrane 450 above an opening 460 in a steel plate 455. By connecting a Water manometer to a pipe socket at the opening 460 on the The membrane 450 on the side facing away from the steel plate 455 could be the membrane 450 Static pressure is applied through the opening 460 in the steel plate 455 will. This static pressure, which was thus applied to the back of the diaphragm 450, caused a transverse deflection of the membrane 450, which by observing the steel plate 455 with the membrane 450 was determined under the microscope, with the change was measured in focus at 400x magnification with a dial gauge on the fine focus. The dial gauge was in Divided 0.0001 inches and measured 0.5 microns

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per 100 dynes / cm for the ratio of the maximum deflection of the membrane 450 in the transverse direction to the applied differential pressure, where linearity was maintained up to deflections of 8 microns. Deflections up to 15 microns with pressures greater than 300 dynes / cm were obtained without breaking the membrane. The individual values the deflection for the various applied pressure differentials are compiled in the table below:

Applied pressure difference (in cm water column) Deflection (in I / IOOQ

0 Q

0.20 --- 0.15

0.30 0.30

0.40 0.40

0.55 0.50

0.70 0.55

0.85 0.65

1.10 0.75

1.20. 0.80

1.35 0.85

1.55 0.95

1.85 1.00

2.05 1.05

2.35 1.15

2.75 1.25

Another experiment was using a square silicon diaphragm 0.8 cm side length by etching the silicon by 19 microns against the polished surface of a silicon plate removed and this is placed on a second silicon plate on which aluminum had previously been vapor-deposited, as illustrated in FIG. 5. The illustration in FIG. 5 shows a first silicon wafer 510 with a silicon diaphragm 550 formed therein, a second and lower Silicon wafer 520 with a vapor-deposited aluminum layer 525 and an etched relief passage 56O and an S silicon dioxide layer 530 for separating the upper silicon wafer 510 from the Aluminum layer 525 on the lower silicon wafer 520 and a cavity 5 ^ 0 between the membrane 550 and the aluminum layer 525. The Relief passage 56O in lower silicon wafer 520 measures approximately 1 mm in the square and forms a gas outlet for the cavity 540, so that no There is a pressure difference on both sides of the diaphragm 550.

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A preload was applied between the two silicon wafers 510 and 520 of 50 V applied, which led to a maximum deflection of the membrane 55Ο in the transverse direction by about 2 microns. The plant of a DC voltage of * tO V as a bias voltage in conjunction with a sinusoidal AC voltage of 80 V vertex distance and 1 Hz led to changes in the transverse deflection of the membrane of at least 55 ° 6 microns. The installation of a sinusoidal alternating voltage with a peak distance of about 20 V and higher frequencies (1 Hz up to 100 kHz) did not produce any noticeable resonance characteristics, however produced the movement of the diaphragm 550 at frequencies of about * f kHz an audible sound wave, whereby the sound intensity increased abruptly with the simultaneous application of a direct voltage of about ^ fO V as a bias voltage. The acoustic signal from the diaphragm 550 was audible for frequencies up to the hearing limit of the human ear at around 18 kHz.

Fig. 6 shows a further embodiment of the invention at which a membrane according to the invention is used for the construction of optical display elements. The device shown in Fig. 6 includes a Membrane 65Ο formed in a silicon layer 610. The silicon layer 61O is separated by a second silicon layer 620 a silicon dioxide layer 63Ο, which is partially etched away, so that an open cavity β '+ Ο results immediately below the membrane 65Ο. In addition, on top of the first silicon layer 610 is a transparent layer 67Ο applied so that there is a second open cavity 66Ο between the membrane 65Ο and this layer 67Ο. the Layer 67Ο can in principle consist of any solid and transparent material, a material that can be used for this is, for example Pyrex.

The display element shown in Fig. 6 can be operated by An electrical voltage is applied between the silicon layers 610 and 620 which is sufficient to deform the membrane 65Ο cause. This deformation then changes the distance between the membrane 650 and the layer 67Ο, whereby the constructive optical interference for incident radiation and thus the optical properties

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of the display element experience a change. A compilation of a plurality of such display elements then enables an electrostatically controllable display, whereby the orad of the constructive interference can be easily controlled for each membrane by changing the electrostatic deformation of the membranes. This way you can use such display elements also build facilities for a multicolor display.

In all of the embodiments shown, it is necessary that between the silicon layer in which the membrane is formed and the Silicon dioxide layer, which is used to separate the silicon layers or the silicon platelets, creates an even and even bond will. A suitable technique for this is described in an article by G. Wallis and D. I. Pomerantz entitled "Field Assisted Glass-Metal Sealing" in Journal of Applied Physics, Vol. ΊΌ, No. 10, 1969, pages 39 ^ 6.

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Claims (1)

27A9937 Dr. HATE - Dr. FRANKE Dr. ULLRICH PATENT LAWYERS IN MÖNCHEN AND HEIDELBERG P 80/401 November 7, 1977 Dr F / F Munich Claims (1 .y K Electromechanical circuit element for installation in semiconductor substrates, in particular made of silicon, characterized in that on a semiconductor substrate (10; 310; 310; 610) consisting in particular of silicon with two opposite sides along a portion of one of these sides up to a desired one Nembrane thickness corresponding depth an etchant-resistant layer is formed with a desired membrane size corresponding lateral dimensions and from the other side to form a cavity (660) ending at the etchant-resistant layer, a selected portion is removed, so that in the etchant-resistant layer one in its lateral dimensions The bottom of the cavity corresponding membrane (30; 250; 350; ^ 50; 550; 650) is created, the thickness of which is selected, taking into account its lateral dimensions, corresponding to the depth dimension of the etchant-resistant layer, so that the membrane under the action äu external forces can experience substantial physical deflection and exhibit mechanical resonance behavior. 2. Circuit element according to claim 1, characterized in that the The thickness of the etchant-resistant layer forming the membrane (50; 250; 350; 450; 550; 65O) is between 1 and 4 microns. 3. Circuit element according to claim 1 or 2, characterized in that the electrical conductivity of the membrane (50; 250; 350-; 450; 55O; 65O) is considerably higher than that of undoped monocrystalline silicon. 4. Circuit element according to one of claims 1 to 3, characterized in that in the etchant-resistant layer in monocrystalline Silicon boron is distributed in a sufficient amount *? * «Amount to achieve resistance to etching old selected etchants for silicon. 809810/0979 5. Circuit element according to one of Claims 1 to 4, characterized in that that the membrane (50; 250; 350; V? 0; 550; 650) on the side the etchant-resistant layer is coated with an electrically conductive metal. 6. Electromechanical capacitance element, characterized by a first substrate (10; 310; 510; 610) made of crystalline silicon with two opposite sides, on which in a partial area of one of these sides an etchant-resistant layer to a selected depth and from the opposite side at the etchant-resistant layer ending cavity (660) is formed, so that a membrane (5O; 250; 35Ο; 450; 55Ο; 65Ο) with a thickness and lateral dimensions which are selected so that the membrane can experience a substantial physical deflection under the action of external forces and exhibits mechanical resonance behavior, and by a second electrically conductive electrode (20; 220; 32Ο; 520; 620) which is located at a selected distance from the side of the etchant-resistant layer of the Membrane is arranged so that electrical charge on this second electrode opposes the membrane when it is Brings the set charge to mechanical deflection and thus the membrane and the second electrode form two plates or coatings of a capacitor of capacitance that varies with the physical deflection of the membrane. 7 * capacitance element according to claim 6, characterized in that the thickness of the membrane (5O; 250; 350; 45Ο; 55Ο; 65Ο) is between 2 and k microns. 8. capacitance member according to claim 6 or 7 »characterized in that the etchant-resistant which forms the membrane (50; 250; 35Ο; 450; 55Ο; 65Ο) Layer consists essentially of crystalline silicon, in which boron is incorporated in a sufficient amount to counteract the layer Etching with selected etchants for silicon to make permanent. 609819/097 $ 9. Capacitance element according to one of Claims 6 to 8, characterized in that the second conductive electrode consists of a layer (20; 220; 320; 520; 620) consists of conductive silicon that between the side of the first silicon substrate (10; 310; 510; 610) with the etchant-resistant Layer on the one hand and the second conductive electrode on the other hand a layer (30; 230; 330; 530; 63Ο) of silicon dioxide is inserted, which ensures electrical insulation therebetween, and that in this silicon dioxide layer between the membrane (5O; 25Ο; 350; 450; 55Ο; 65Ο) and the conductive silicon electrode a cavity (40; 240; 340; 540; 64Q) is designed, which allows a free deflection of the membrane. 10.Kapacitance element according to one of claims 6 to 9, characterized in that the membrane (5O; 250; 350; 450; 550; 65Ο) coated on the side of the etchant-resistant layer with an electrically conductive metal is. 11. Capacitance member according to one of claims 6 to 10, characterized in that the space between the membrane (5O; 250; 350; 450; 55Ο; 650) and the second conductive electrode (20; 220; 320; 52Ο ;. 620) with respect to the side of the first silicon substrate (10; 310; 510; 6iO) containing the cavity (66Ο) is sealed, so that pressure differences on both sides of the membrane to its deflection and thus to changes in the capacitance between the membrane and the second electrode lead, on the basis of which pressure changes can be detected. 12. Capacitance member according to one of claims 6 to 10, characterized in that the etchant-resistant layer in the first silicon substrate (10; 310; 510; 610) is formed between its two sides and that on the first cavity (66Ο) opposite side of the first silicon substrate, a second cavity is formed so that the membrane (50; 250; 35Ο; 450; 55Ο; 65Ο) in the caustic resistant Layer is created between the two cavities. 609819/0971 13 · Capacitance element according to one of Claims 6 to 12, characterized in that the second conductive electrode consists of a second layer (20; 320; 220; 520; 620) consists of conductive silicon that the second conductive electrode through a layer (30; 230; 330; 530; 63O) Isolation material separated from the membrane (5O; 250; 350; ^ 50; 550; 65O) and is electrically insulated from the fact that in the insulating material layer between the membrane and the second silicon electrode a chamber CfO; 240; 340; 540; 640) is formed that the second silicon electrode a continuous channel (270) opening into the chamber and that a body (260) is attached to the diaphragm and moves with the diaphragm and, as the case may be, between the diaphragm and the second Silicon electrode prevailing electrostatic attraction opens or closes the mouth of the channel in the chamber. 14. Capacitance member according to one of claims 6 to 12, characterized in that on the second electrode (20; 220; 320; 520; 620) facing away from the side of the first silicon substrate (10; 310; 51O; 610) a the first cavity (66O) covering, essentially planar and optically transparent layer (67O) is arranged so that the displacement of the Membrane (50; 250; 35O; 450; 55O; 65O) visible changes through constructive interference of the incident light between the optically transparent layer and the surface of the membrane facing it evokes. 15 · capacitance element according to one of claims 6 to 12, characterized in that in connection with the second conductive electrode (20; 220; 32O; 520; 620) a plurality of electrically conductive pyramid-shaped projections (380) of the membrane (5O; 25O; 35O; 450; 55O; 65O) are compared in such a way that when they are bent they towards the second electrode. individually come into contact with the membrane, each of these conductive protrusions for attraction of the membrane can be fed separately with electrical charge for mutual contact. 16. Capacitance member according to one of claims 6 to 15, characterized in that the second conductive electrode (2Q; 220; 320; 52O; 62Q) 809811/0971 one at a distance from the membrane (50; 350; 35O; if5O; 55O; 65O) arranged Layer of electrically insulating material and a layer (525) of electrically having conductive metal. 17. A method for producing electromechanical circuit elements for installation in integrated circuits on semiconductor substrates, characterized in that in one of two opposite sides of a silicon substrate to form an etchant-resistant layer of a selected depth, an etching retardant to achieve etch resistance against etching with selected etchants for silicon sufficient amount is diffused in that the side of the silicon substrate opposite the etchant-resistant layer is covered with a mask leaving a selected area of the silicon surface of predeterminable lateral dimensions and that silicon etchant is applied to the exposed surface area until enough silicon is dissolved to remove the to expose the etchant-resistant layer at which the further etching is delayed, wherein the exposed area of the etchant-resistant layer forms a thin membrane therein t, the thickness of which, taking into account its lateral dimensions, is so dimensioned that the membrane can experience substantial physical deflection under the action of external forces and exhibits mechanical resonance behavior. 18. The method according to claim 17, characterized in that the etching retardant is so diffused into the silicon substrate that an etchant-resistant layer with a thickness between 1 and k microns results. 19 · The method according to claim 17 or 18, characterized in that as Etching retardant boron is used. 809818/097