EP1031161B1 - Microrelay - Google Patents

Abstract

A microrelay manufactured by microsystem technology and a process for manufacturing the same are disclosed. In the claimed microrelay, the excitation coil has a conical form. This conical arrangement of the coil windings induces a magnetic field which is substantially more homogeneous than in planar coils. Due to this more homogeneous magnetic field, the relay contact elements are pressed more strongly onto the contact surfaces and an electromagnetic relay with higher wear resistance and longer service life is obtained. The conical arrangement of the coil windings can be obtained by metal deposition and structuring on the walls of a pit anisotropically etched in a silicon chip.

Description

The present invention relates to a microsystem technically manufactured micro relay as well as a Process for its manufacture. Especially in the Fields of telecommunications, medical technology, Data processing, measurement technology and in the automotive sector a great need for miniaturized relays.

So far, have been used for a variety of applications mainly electrostatic relays used. This However, relays require high voltages (typically in the range of 100 V), so that specially designed Control devices and insulation measures for operation are necessary. However, this increases the system costs.

In H. Hosaka, et al., Sensors and Actuators A, 40 (1994), Pp. 41-47 is therefore on the advantages of electromagnetic Microrelay received. The presented there Microrelay consists of one or more conventional ones small electromagnet over which a flat one Contact spring is moved. Hosaka examined it especially the influence of the contact force on the Contact resistance, the dependence of the size of the Breakdown voltage of the width of the electrode gap as well as the behavior of different Contact spring geometry. With the micro relay from Hosaka high switching speeds (around 1 kHz) realize. However, this microrelay cannot be used Means of semiconductor technology are produced.

Furthermore, they are manufactured using microsystems technology Microrelay known. These consist of a planar Magnetic field generating coil and free-standing contact arms of the working circuit, the were generated by suitable etching techniques.

However, the use of planar coils brings a number of Disadvantages with themselves. Planar coils are very susceptible to magnetic fields (see e.g. H. Meinke et al., Taschenbuch der Hochfrequenztechnik, Springer-Verlag Berlin (1968), p. 19). That with planar coils generated magnetic field is also very inhomogeneous, and the maximum field strength density is limited. The latter is particularly due to the small cable cross-section (with the consequence of a low current flow), which results from the necessary limitation of the large space requirement planar coils.

For these reasons, the contact arms (spring contacts) force acting relatively small, so that Contact pressure of the spring contacts on the contact surfaces, for example in the event of vibrations, is not sufficient is. This results in wear on the contact points and the life of the component is shortened. Farther are the maximum adjustable distance between the contact arms and hence the maximum switchable voltage in the working circuit limited.

In Y. Watanabe et al., Sensors and Actuators A 54 (1996), Pp. 733-738, a manufacturing process for a Planar coil described that with higher current densities work and can therefore generate higher field strengths. Also however, this coil has the above problems due to the inhomogeneity of the magnetic field.

The object of the present invention is a Microrelay and a method of manufacturing the same to indicate that a longer life and a less wear than known microrelays has planar coil, and simply by means of Semiconductor technology can be produced.

This task comes with the characteristics of the current Claims 1 and 13 solved. Advantageous further training the invention are the subject of the dependent claims.

The microrelay according to the invention consists of how known microrelay, from an excitation coil Generation of a magnetic field and an or several contact elements. The contact elements can in this case, for example, clamped on one side, free-standing contact arms or contact springs. Also elastic contact bridges clamped on both sides or comparable contact elements clamped on several sides are suitable. These contact elements are made by Effect of the magnetic field of the coil on one Pressed or released contact surface, so that thereby a contact in a working circuit is closed or opened. According to the invention Microrelay on a coil with a conical shape.

This conical arrangement of the coil turns induces a much more homogeneous magnetic field than in the case of planar coils. Due to this more homogeneous magnetic field, a higher contact pressure of the contact elements on the contact surfaces is generated, so that a higher wear resistance and longer life of the electromagnetic relay can be achieved. Switching times are also shortened.
A larger conductor cross-section of the excitation coils, which can be generated due to the smaller area requirement of the conical coil, enables the use of higher currents and thus the generation of stronger magnetic fields. This makes it possible to maintain larger distances between the contact arms, so that the switchable voltage in the working circuit can be increased.

A further increase in field strength can be done easily Way by filling the interior of the conical coil can be achieved with ferromagnetic material. On complete filling of the interior is from Advantage.

Another advantage of the microrelay according to the invention is the easy integration into one Semiconductor substrate, as is the case with the invention Procedure is carried out. The proceeding continues the advantage that all components of the microrelay in one process run together on one Semiconductor wafer can be produced. The semiconductor compatibility manufacturability of the microrelay is of particular advantage.

In a special embodiment, this is electromagnetic microrelay of two microsystem technically manufactured parts, one component with the excitation coil and a component with Contact elements, assembled.

The component with the excitation coil consists of an anisotropic trench etched into a silicon wafer, the Floor area over a highly doped diffusion area the opposite side of the disc (in the following arbitrarily referred to as the front) electrical connected is. On an insulation layer on the A metal layer is deposited on the trench walls. By Lithography of a galvanic applied to it The intended coil structure is produced by means of photoresists. In the same process step, the contact areas as well the lead out of a coil connection on the Rear of disc formed. The second coil connector is through the via (the highly doped Diffusion area) on the front of the disc guided.

Then in this embodiment, the Conductor cross sections through galvanic metallization elevated. Finally, the coil interior becomes after Deposition of an insulation layer with a filled ferromagnetic material.

The contact elements are also anisotropic Etching a trench into a silicon substrate Use of the etch stop on highly doped layers manufactured. As a result, free-standing booms or Tongues (as contact arms) formed on the previously one ferromagnetic and the contact metal deposited and were structured. By applying a system layers that are braced against each other is also the bend and thus the distance between the tongues and the contact surfaces adjustable on the coil unit. It is about here layers with different thermal Expansion coefficient. In the last manufacturing step the two components are placed on top of each other, whereby different bonding techniques can be used. Furthermore, the connections to the housing are made.

Fig. 1

ein Beispiel für die Ausgestaltung der Spuleneinheit des erfindungsgemäßen Mikrorelais;

Fig. 2

ein Beispiel für die Einheit mit den Kontaktelementen des erfindungsgemäßen Mikrorelais;

Fig. 3 bis 11

verschiedene Herstellungsschritte der Einheiten des erfindungsgemäßen Mikrorelais gemäß den Fig. 1 und 2; und

Fig. 12 und 13

eine weitere Ausgestaltung der Spuleneinheit und der Einheit mit den Kontaktelementen eines erfindungsgemäßen Mikrorelais.

A preferred production method for a micro relay according to the invention is described below with reference to the drawings. Here show:

Fig. 1

an example of the design of the coil unit of the microrelay according to the invention;

Fig. 2

an example of the unit with the contact elements of the microrelay according to the invention;

3 to 11

different manufacturing steps of the units of the microrelay according to the invention according to FIGS. 1 and 2; and

12 and 13

a further embodiment of the coil unit and the unit with the contact elements of a microrelay according to the invention.

Fig. 1 shows a coil unit of a microrelay according to the invention with contacts for a two-pole relay. In the following, the side of the coil unit visible in FIG. 1 is referred to as the rear side.
The coil unit is formed from a silicon substrate 4 which has an anisotropically etched trench 6. The coil turns of the excitation coil 1 are located on the trench walls. One coil end is connected in an electrically conductive manner to the coil contact 10 on the front side of the substrate 4 via the highly doped silicon region 7 at the bottom of the trench 6. The coil contact 10 is separated from the silicon substrate 4 by an insulation layer 13 (SiO ₂ ). Likewise, the coil turns of the coil 1 and the further connection surfaces on the back of the substrate are insulated from it by a layer 22. The input poles 3a and the output poles 3b forming the contact surfaces are also arranged on the back of the substrate 4. A working circuit is closed by connecting the input poles to the output poles via the contact springs of the further component (FIG. 2). Furthermore, the coil contact 11 and solder contacts 9 are located on the back of the substrate.

FIG. 2 shows a unit with spring contacts 2 which, together with the coil unit from FIG. 1, form a microrelay according to the invention. The visible surface of this unit is referred to below as the front. The unit with the spring contacts consists of a silicon substrate 5 with an anisotropically etched trench 8, through which the spring contacts are exposed. On the front of the substrate 5 there are solder contacts 9 within an SiO ₂ / Si ₃ N ₄ layer 13, 14. The spring contacts 2 themselves consist of a layer sequence of highly doped n ⁺⁺ silicon, SiO ₂ / Si ₃ N ₄ , chromium , Nickel and gold.

3 to 11 will now be used with reference to FIGS preferred manufacturing process for the relay according to the 1 and 2 are described. When presenting the individual process steps are those in the Semiconductor technology not usual cleaning steps listed, although they are done naturally. The The front of the silicon substrates corresponds to the following figures on the top page. to The coil unit with coil component are simplified and the unit with the spring contacts with Spring contact component named.

As the starting material for the manufacture of the micro relay become low-resistance, p-doped silicon wafers used. Typical slice thicknesses are here between 300 µm and 700 µm. Are currently Disc diameter of 100 mm or 150 mm usual which a variety of micro-relays according to the invention can be manufactured.

The microrelay consists of two micromechanically Silicon manufactured parts (coil component and Spring contact component), which at the end of the Manufacturing process are put on top of each other. So far Unless otherwise described, the following relate Manufacturing steps on both sub-elements. differing Process steps are shown by separate figures characterized.

The silicon wafer 4, 5 is first thermally Scattering oxide 13 for the subsequent implantation step grew up (see Fig. 3). The typical thickness of the Scatter oxide layer 13 is in the range of 20 nm here Oxide grows on both sides of the disc.

Then it becomes about 500 to 1500 nm thick Photoresist layer 15 applied and to the implanting sites removed photolithographically (see Fig. 3). The dimensioning and arrangement of these Areas are selected in the case of the excitation coil so that the implanted area the bottom of the later etched Trench 6 forms (see. Fig. 1). He puts that Through contact to the front of the substrate 4. Im The case of the spring contact component corresponds to implanting area of shape and area of the Spring contacts (see Fig. 2).

High dose ion implantation follows to produce highly doped n regions 7, 16. Typical elements for the n ⁺⁺ implantation are phosphorus and arsenic.
The scatter oxide 13 is then removed by wet chemistry at the exposed locations on the front side and on the entire rear side. The lacquer layer 15 is then removed.

After a thermal diffusion step at temperatures around 1000 ° C., a relatively homogeneously distributed n ⁺⁺ layer 7, 16 forms in the p-doped silicon substrate 4, 5 (see FIG. 4). This highly doped area is necessary for the electrochemical etching stop in the subsequent anisotropic etching step and as an electrical contact area 7 for the excitation coil. Furthermore, these highly doped areas are not attacked by the anisotropic etching solution, so that free-standing cantilevers or tongues 2 are formed for the spring contacts. The depth of the n-region 7, 16 is up to 10 μm.

In order to protect the front of the pane from scratching during the subsequent nitride deposition and in the dry etching process, it is provided with a coating 17 over the entire surface (see FIG. 4). Silicon nitride 18 is deposited on the back of the substrate 4, 5 as a mask for the anisotropic etching by means of cathode sputtering (see FIG. 4).
This is followed by lacquering 19 of the rear side and the photolithographic exposure of the region to be etched anisotropically (cf. FIG. 4).

By dry etching in the plasma Silicon nitride layer 18 at the free locations on the Back removed. This will make the later etchable Area of the silicon substrate defined. The ones to be etched Surfaces are chosen so that none of the coil component complete etching through of the disk is possible, i.e. that the etching process on the heavily doped n region 7 stops (see Figures 5A and 1). The exposed area of the Spring contact component, however, extends over the n-regions 16 that the etching solution up to Front panel penetrates and free-standing arms arise (see Fig. 5B and 2).

Then the lacquer 17, 19 is peeled off on both sides.

To generate spring contacts bent downwards, open the spring contact component is a combination of silicon oxide and deposited silicon nitride. 5B shows this Layer 14. Silicon oxide has a lower one thermal expansion coefficient as silicon, Silicon nitride a higher. When the panes cool down after the deposition processes, depending on the thickness tensile or compressive stress on the two layers Contact arms. As soon as the contact arms are free, bend consequently they move up or down (see FIG. 2). On in this way the production of relays is possible Working circuit open or closed in idle state is. This process step is omitted for the coil component.

For defining the conductor tracks and contact areas both components in the layer lifting process is now the Front coated and structured photolithographically. Here is a negative paint 20 with thicknesses between 2 and 5 µm to choose.

Next a thin (20 to 50 nm are sufficient) chrome layer for adhesion and a between 1 and 3 µm thick nickel layer as the basis for the galvanic gold plating of the conductor tracks applied. This layer combination 21 is shown in FIGS. 5A and 5B detect. Nickel is ferromagnetic and therefore also serves as a magnet to attract or repel the Spring contact arms. The thicker the layer will be run the better the switching behavior of the relay.

When the paint is peeled off, those on the removed coated areas of deposited metals, so that the desired trace pattern on the front arises (see FIGS. 6A, 6B and 2). To increase the mechanical stability of the microrelay are on several places of the spring contact component small Solder contact surfaces 9 attached (see FIG. 2).

By means of anisotropic etching in an alkaline solution (e.g. Potassium hydroxide) are now the spring contacts and the conical coil space exposed. The front of the window is by a suitable holder before the solution protect. Because of different Removal rates of potassium hydroxide in different crystal directions of silicon are the Sidewalls always 54.74 ° compared to the Slice surface inclined (see Figs. 6A, 6B, 1 and 2; not shown true to the angle). In both components will have different effects for automatic Stop of the etching process exploited. In the coil component by applying a suitable voltage to the highly doped via 7 of the excitation coil Etching process about 5 microns before reaching the n-area 7 to Broken down (electrochemical etching stop, see Fig. 6A). The spring contact component takes advantage of the fact that Potassium hydroxide highly doped areas, oxides and nitrides attacks very little, so that the one shown in Fig. 6B Structure of the component is created.

Using dry etching, this is now done on both components back silicon nitride 18 removed. Furthermore, on Spring contact component the exposed combination layer etched from oxide 13 and nitride 14, so that free-standing, spring contacts clamped on one side (see Fig. 7). This component is now except for the galvanic gilding of the metal areas completed and is therefore not included in the next steps included.

The coil component is then coated on the front (not shown in the figures) to the surface in front of the to protect subsequent processes.

In an isotropic etching step (e.g. in a dilute Hydrofluoric acid) are those that result from anisotropic etching Edges with approx. 3 to 5 µm overhang (see. Fig. 6A, 6B and 7) rounded. The result can be seen in FIG. 8.

A low temperature oxide is placed on the etched back 22 deposited (e.g. with cathode sputtering), which as electrical insulator to the silicon substrate. Then a thin, if possible reflection-free metal layer 23 (for example titanium deposited with a layer thickness of 50 nm) (see Fig. 8).

Lacquer 24 is now electrochemically applied to this metal layer deposited with a thickness of 5 to 25 µm (for example Electroplating varnish PEPR 2400, company Shipley) and structured photolithographically, so that the area over the via 7 is exposed (see Fig. 8). Then the Titan 23 and the Oxide layer 22 removed by wet chemical means (see FIG. 9). In the next step, the galvanic lacquer 24 is removed.

Deposition of a titanium layer with some follows 100 nm thickness, which is covered with a wafer - thin nickel layer of a few nanometers thick. This Layer combination 25 is shown in FIG. 9. she serves as the basis for the following galvanic Interconnect gilding.

Electrochemical lacquer 26 with 5 to 25 µm thick deposited (galvanic paint PEPR 2400) and structured photolithographically so that the Coil geometry and the conductor tracks of the Rear of the pane can be defined (see FIGS. 9 and 1). Here you can also find the mirrored ones on the Spring contact component provided solder contacts 9 for Increasing the mechanical stability of the microrelay (see Fig. 1).

Now the titanium / nickel layer 25 on the open Places removed by wet chemistry. The titanium / titanium / nickel layer is drawn as a layer in Figure 10. The electroplating lacquer 26 is removed.

To increase the conductor cross-sections (thicknesses from 1 to 20 µm) now become the metal areas on both components electroplated (see Fig. 10, layer 27). Then the ones on the semiconductor wafer manufactured components isolated by sawing.

At the end of the manufacturing process, the two Components connected with a reflow soldering process. This is done at the points to be merged fusible solder 28 applied and the second component placed. Tempering the parts creates a firm, conductive connection achieved. Fig. 11 shows the composite components that the invention Form micro relays.

To increase the magnetic field and with it associated benefits, i.e. Reduction of switching times, Increase of switchable voltages and currents, Shock resistance, lower contact resistance and consequently less contact load, etc. is the Installation of a ferrite core in the coil space possible. To For this purpose, a Insulation layer applied (for example paints with high viscosity or oxide). Then one ferromagnetic layer, a ferrite mass or a Ferrite core introduced. As materials have alloys made of iron and nickel have proven their worth.

1 and 2 show a two-pole relay, which in Has open contacts. It can be however, with the above method also one or more poles Establish relays that open or at rest have a closed contact in the idle state can.

Furthermore, the use of bimetallic Spring contact arms advantageous as this is the manufacture of bimetallic relays, the states of which are indicated by short Current pulses can be exchanged.

In the above description of making a Microrelay according to the invention Spring contact component with its front on the Back of the coil component set. With more suitable Arrangement of the conductor tracks, contact areas and However, solder contacts are also possible for both components to connect on the front. Furthermore is of course, a different structure of the both components, as it is for example in the 12 and 13 is shown. For example, here are the Contact arms 2 on the rear of the spring contact component arranged, the trench only as with the coil component up to a highly doped area 16 as the bottom of the Digging is enough. Also in this example are the Input poles 3a and 3b output poles on different Components arranged.

Because of the possibility of switching high voltages and with correspondingly large conductor cross sections high currents is the microrelay according to the invention for the Use in the field of power electronics in particular suitable. The low level is characteristic of the relay Size and the low power requirement of the Electromagnets as well as an ideal conductor separation.

Due to the great resistance to vibrations, an application in the field of automotive electronics.

Claims (19)

1. Micro relay constituted by a field coil (1) for establishing a magnetic field, and by one or several contact elements (2) opening or closing a contact (3) under the action of the electric field of said coil,
   characterised in that said coil (1) has a conical shape.
2. Micro relay according to Claim 1, characterised in that said coil is integrated into a semiconductor substrate (4).
3. Micro relay according to Claim 1 or 2, characterised in that the interior space enclosed by said coil is charged with a ferromagnetic material.
4. Micro relay according to Claim 1 or 2, characterised in that a ferrite core is disposed in said interior space enclosed by said coil.
5. Micro relay according to any of the Claims 1 to 4, characterised in that said contact element(s) is/are designed in the form of self-supporting contact arms.
6. Micro relay according to any of the Claims 1 to 5, characterised in that said contact element(s) is/are designed in the form of spring-finger contactors.
7. Micro relay according to any of the Claims 1 to 6, characterised in that the relay is composed of two parts manufactured by micro mechanical techniques, of a coil unit (4) and a unit (5) with one or several contact elements.
8. Micro relay according to Claim 7, characterised in that said coil unit consists of a silicon substrate (4) with a trough (6) etched therein by an anisotropic technique, with the windings of said coil bearing against the lateral walls of said trough.
9. Micro relay according to Claim 8, characterised in that the bottom surface of said trough connects one end of said coil via a highly doped diffusion zone (7) to the opposite side of said electrically conducting substrate.
10. Micro relay according to any of the Claims 7 to 9, characterised in that said units with contact elements consists of a silicon substrate (5) with a trough (8) etched therein and above which are disposed one or several self-supporting studs as contact elements, extending from an edge of said trough.
11. Micro relay according to any of the Claims 1 to 10, characterised in that the contact element(s) is/are structured to present layers biased relative to each other.
12. Micro relay according to any of the Claims 1 to 10, characterised in that the contact element(s) comprise(s) a bimetallic layer.
13. Method of manufacturing a micro relay according to any of the preceding Claims, comprising the following steps of operation:

    etching a trough (6) by an anisotropic technique in a first silicon substrate (4) on a rear side of said substrate;

    depositing an isolating layer (22) in said trough;

    depositing a layer (23, 25) of a coil material on said isolating layer;

    depositing a photoresist (26) on said layer of coil material;

    structuring said photoresist by a photolithographic technique in correspondence with a coil structure to be produced on the lateral walls of said trough;

    removing said coil material (23, 25) from exposed zones;

    removing said photoresist (26);

    creating contact surfaces (3a, 3b) and connecting surfaces (10, 11) for the coil windings on the front and rear sides of said first substrate (4);

    providing a second silicon substrate (5) at one or several contact elements (2) coated with an electrically conductive material;

    connecting said two substrates in a way that the contact element in said second substrate open or close corresponding contacts (3b) in the other substrate (4) when a movement is induced by the magnetic field of said coil.
14. Method of manufacturing a micro relay according to Claim 13, characterised in that prior to etching of said trough (6) in said first substrate, a highly doped diffusion zone (7) is formed by ion implantation on the front side of said substrate (4), which constitutes the bottom surface of said trough (6) and establishes the electric connection of one coil end to the front side of said substrate.
15. Method of manufacturing a micro relay according to Claim 13 or 14, characterised in that said contact elements (2) of said second silicon substrate (5) are produced by the following steps of operation:

    creating a highly doped diffusion zone (16) that has the lateral dimensions of said contact elements (2), by ion implantation on one self-supporting contact arm on the front side of said second substrate (5);

    depositing an electrically conductive layer (21) on this zone;

    etching, by application of an anisotropic technique, a lead-through (8) or a trough in aid second silicon substrate, starting out from the rear side of the latter, such that cantilever arms will be exposed as contact elements.
16. Method of manufacturing a micro relay according to any of the Claims 13 to 15,
    characterised in that prior to the etching step, a system of layers (14) biased relative to each other is applied on said contact elements, so as to define a desired subsequent bending of said contact elements.
17. Method of manufacturing a micro relay according to any of the Claims 13 to 16,
    characterised in that the cross-sections of the windings of said coil are increased by a galvanic metal coating (27).
18. Method of manufacturing a micro relay according to any of the Claims 13 to 17,
    characterised in that the windings of said coil are coated with an insulating layer and that said trough of said first substrate is filled with a ferromagnetic material.
19. Method of manufacturing a micro relay according to any of the Claims 13 to 18,
    characterised in that said first substrate (4) and said second substrate (5) are present on a semiconductor chip and are processed at the same time.

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