DE102017215236A1 - MEMS switch and method of manufacturing a MEMS switch - Google Patents

Abstract

The MEMS switch has a deflectable articulated flexure, the MEMS switch having a silicon on insulator substrate.
In the method for producing at least one MEMS switch, a silicon-on-insulator substrate is used.
The arrangement comprises two or more MEMS switches, wherein the MEMS switches are such MEMS switches as mentioned above or manufactured according to the aforementioned method.

Description

The invention relates to a MEMS switch and to a method for producing a MEMS switch.

Microelectromechanical Systems (MEMS) switches typically comprise micrometer-sized electrostatically actuated flexures. Frequently, a plurality of such MEMS switches are arranged in an array, in particular for the circuit of sufficiently large currents.

However, the switching times of such switches vary in an arrangement. For typical applications, however, such a variation of the switching times is undesirable.

Against this background of the prior art, it is therefore an object of the invention to provide a MEMS switch which can be formed precisely, in particular reliably with respect to its switching times. It is a further object of the invention to provide a method for producing a MEMS switch, by means of which MEMS switches can be precisely manufactured precisely and in particular with regard to the switching times. In addition, it is an object of the invention to provide an arrangement of MEMS switches, in which the variation of switching times of different MEMS switches is reduced.

This object of the invention is achieved with a MEMS switch having the features specified in claim 1 and with a method having the features specified in claim 5 and with an arrangement comprising two or more MEMS switches having the features specified in claim 13. Preferred embodiments of the invention are set forth in the appended subclaims, the following description and the drawing.

The inventive MEMS switch has a deflectable arranged bending element. The MEMS switch according to the invention has a silicon-on-insulator substrate. In the case of the MEMS switch according to the invention, the bending elements as a result of the silicon-on-insulator substrate can be produced with high precision, in particular with regard to their thicknesses. In contrast, a precise formation of galvanic layers and thus a sufficiently precise realization of a predetermined switching time in previously known MEMS switches is difficult. According to the invention, however, silicon-on-insulator substrates already have very homogeneous silicon layers, so that high-precision MEMS switches with a precisely defined switching time can be produced with silicon-on-insulator substrates. In addition, in the MEMS switch according to the invention, the bending element can be realized with monocrystalline silicon, which has a precisely controllable modulus of elasticity, so that unintentional deviations and, as a result, an inhomogeneity of the switching times can be avoided in this regard as well.

In the case of the MEMS switch according to the invention, the silicon-on-insulator substrate expediently forms a silicon-insulator-silicon layer sequence or has a silicon-insulator-silicon layer sequence. In this development of the invention, the bending element of the MEMS switch according to the invention can advantageously be formed by means of one of the silicon layers of the silicon-insulator-silicon layer sequence. Preferably, further layers of the silicon-insulator-silicon layer sequence are at least partially removed by etching, so that an at least partially free-standing bending element can be realized.

In the case of the MEMS switch according to the invention, the bending element preferably has the silicone-on-insulator substrate and / or the silicone-on-insulator substrate has the bending element.

Preferably, in the MEMS switch according to the invention, the bending element is arranged on an insulator layer of the silicon-on-insulator substrate. Particularly preferably, in the MEMS switch according to the invention, the silicon-on-insulator substrate has a silicon-insulator-silicon layer sequence, wherein by means of etching in portions of at least one silicon layer of the silicon-insulator-silicon layer sequence, the bending element of the MEMS switch is formed and wherein a part of the insulator layer of the silicon-insulator-silicon layer sequence forms a connection, by means of which the bending element is arranged on a further silicon layer of the silicon-insulator-silicon layer sequence. Suitably, this further silicon layer of the silicon-insulator-silicon layer sequence acts as a foot for the flexure, i. a in the operation of the MEMS switch in itself rigid and fixed point-like region of the MEMS switch, on which the bending element is movably arranged.

The inventive method is a method for producing at least one MEMS switch, in particular a MEMS switch according to the invention with a bending element as described above. In the method according to the invention, a silicon-on-insulator substrate is used, preferably such a silicon-on-insulator substrate, which forms or has a silicon-insulator-silicon layer sequence.

Suitably, in the method according to the invention for forming the bending element, a layer formed with silicon at least partially removed. Preferably, a silicon-on-insulator substrate having a silicon-insulator-silicon layer sequence is used for this purpose, wherein a silicon layer and an insulator layer of the silicon-insulator-silicon layer sequence are removed to form the bending element.

Suitably, in the method according to the invention, a layer is removed by using lithography and subsequent etching. The above methods are advantageously routinely used for the production of MEMS switches manufacturing steps.

Preferably, in the method according to the invention for contacting the bending element, an insulator layer of the silicon-on-insulator substrate is removed at least in areas and these areas are metallized or an insulator layer of the silicon-on-insulator substrate is metallized, at least in some areas.

In the method according to the invention, a silicon layer of the silicon-on-insulator substrate is suitably at least partially doped for contacting the bending element.

In an advantageous development of the method according to the invention, a mating contact with the bending element, in particular with a contacting of the bending element, of the MEMS switch is produced by using a substrate formed with glass. Preferably, for the formation of recesses in the substrate at least partially glass is removed and the substrate is subsequently metallized. Advantageously, manufacturing techniques for removing glass are routinely used with high precision. By means of this method step, a precise dimensioning of the recess can be achieved and thus ensure a defined distance between the bending element and the mating contact. In this development of the method according to the invention, a MEMS switch with a defined and homogeneous switching time can be produced.

In the method according to the invention, preferably two or more MEMS switches are produced, wherein the MEMS switches are produced with the same silicon-on-insulator substrate. Due to the production of MEMS switches with bending elements with defined thicknesses, which is possible by means of the silicon-on-insulator substrate, it is possible according to the invention to produce two or more MEMS switches with switching times which differ from one another extremely small.

The arrangement according to the invention comprises two or more MEMS switches, wherein in the arrangement the MEMS switches according to the invention are MEMS switches as described above and / or MEMS switches which are manufactured according to the method according to the invention as explained above. Thus, the arrangement according to the invention can be realized with particularly small deviating switching times of the MEMS switches from each other.

In an advantageous embodiment of the invention, in the arrangement, the MEMS switches are formed with the same silicon-on-insulator substrate. In particular when manufactured with the same silicon-on-insulator substrate, the bending elements of the two or more MEMS switches can be formed from the same layer, so that the thickness and thus the switching time of the two or more MEMS switches have particularly small deviations from one another.

The invention will be explained in more detail with reference to embodiments shown in the drawing.

• 1 bis 7 einen Teil eines Ablauf des erfindungsgemäßen Verfahrens zur Herstellung erfindungsgemäßer MEMS-Schalter, in welchem Biegebalken der MEMS-Schalter einer erfindungsgemäßen Anordnung hergestellt werden, in aufeinanderfolgenden Prozessstadien schematisch im Längsschnitt,
• 8 bis 12 einen weiteren Teil des Ablauf des erfindungsgemäßen Verfahrens gem. 1 bis 7, in welchem Gegenkontakte des Biegebalkens der MEMS-Schalter hergestellt werden, in aufeinanderfolgenden Prozessstadien schematisch im Längsschnitt sowie
• 13 und 14 zwei Ausführungsbeispiele von mittels des erfindungsgemäßen Verfahrens gem. 1 bis 12 hergestellter erfindungsgemäßer MEMS-Schalter schematisch im Längsschnitt.

Show it:

• 1 to 7 a part of a sequence of the method according to the invention for the production of MEMS switches according to the invention, in which bending beams of the MEMS switches of an inventive arrangement are produced, in successive process stages, schematically in longitudinal section,
• 8th to 12 another part of the process of the method according to the invention. 1 to 7 , in which mating contacts of the bending beam of the MEMS switches are produced, in successive stages of the process schematically in longitudinal section and
• 13 and 14 two embodiments of means of the method according to the invention. 1 to 12 produced inventive MEMS switch schematically in longitudinal section.

As in the 1 to 7 is shown for the inventive production of an inventive arrangement of inventive MEMS switch an SOI substrate 10 ("Silicon On Insulator" substrate) used, which is a silicon-insulator-silicon layer sequence 20 having on an insulating layer formed with glass 30 is arranged. The insulation layer 30 and a layered insulator 40 the silicon-insulator-silicon layer sequence 20 of the SOI substrate 10 are each made of glass, ie silicon dioxide. Thus, the SOI substrate has 10 a layer sequence on which a homogeneous glass layer 30 (in 1 at the bottom), building on this a 300 micron thick homogeneous silicon layer 70 , then the one micrometer thick layer formed as a glass layer insulator 40 and finally a 10 micron thick outer silicon layer 80 having.

To fabricate bending beams the MEMS switch is placed on the SOI substrate 10 initially applied a metallization:

This is done on the SOI substrate 10 to the outer silicon layer 80 a homogeneous 300 nanometer thick outer glass layer 90 sputtered. The homogeneous glass layer 90 is structured by means of lithography such that this glass layer 90 along two parallel stripes 100 (in the drawing acc. 2 perpendicular to the plane of the drawing) can be removed by etching. Below is the glass layer along the strips 100 removed by etching according to the RIE (Reactive Ion Etching) method. Consequently, in the in 2 process stage represented the glass layer 90 along two parallel stripes 100 away.

The glass layer 90 thus forms a mask for subsequent doping of the upper silicon layer 80 , The upper silicon layer 80 will be like in 3 represented in a superficial area 102 heavily doped with phosphorus. The following is the outer silicon layer 80 with the glass layer 90 Etched using hydrofluoric acid and then by means of a 300 nanometer thick gold layer 110 metallized. The gold layer thus extends along the two strips 100 along which the silicon of the outer silicon layer 80 doped by phosphorus and along one between the strips 100 intermediate area 105 , which by means of one between the strips 100 remaining area of the glass layer 90 from the outer silicon layer 80 is electrically isolated.

Furthermore, one of the stripes will be added 100 remote area of the glass layer 90 by means of a 300 nanometer thick gold layer 120 metallized. In further, not specifically illustrated embodiments, the metallization can also be formed with a 20 nanometer thick chromium layer. The metallization is carried out as known per se by means of lithography and a subsequent etching step ( 4 ). The two gold layers 110 . 120 At the MEMS switch, a connection (gold layer 110 ) and a free end (gold layer 120 ) of the bending beam form.

Subsequently, the SIO substrate 10 spatially structured ( 5 ):

These will be adjacent to the gold layers 110 . 120 at their respective other gold layer 110 . 120 far side to the stripes 100 parallel extending column 130 . 140 in the outer glass layer 90 and the outer silicon layer 80 introduced, which in the thickness direction d through the outer glass layer 90 to the insulator 40 adjacent to the SIO substrate 10 protrude. The gaps run to the stripes 100 parallel.

These are the outer glass layer 90 by lithography and the RIE process and the outer silicon layer 80 by means of the DRIE method (DRIE = Deep Reacive Ionetching) for the formation of the column 130 . 140 away. Below is how in 6 represented the insulation layer 30 and the silicon layer 70 and the insulator 40 by lithography and sequential execution of the RIE method, the DRIE method and the RIE method in the region of the SIO substrate 10 removed, which at the on the gold layer 120 lying gap 140 as well as the gold layer 120 and between the gold layer 110 and gold layer 120 lying region of the outer silicon layer 80 adjoin.

Consequently, by means of the gold layers 110 and 120 bearing outer silicon layer 80 the bending beam 150 formed, whose free end with the gold layer 120 is formed and which by means of the insulator 40 close to the gold layer 110 attached to the SIO substrate. As a result of the gap 130 is the bending beam of other areas of the outer silicon layer 80 mechanically decoupled.

Below is the outer glass layer 90 at those areas of the outer silicon layer 80 , which are not metallized, removed by means of hydrofluoric acid. Consequently, only the outer silicon layer remains 80 to which further parts of the MEMS switch can be connected in one of the subsequent production steps.

At the bending beam 150 forms the gold layer 120 a first contact bending beam 150 of the MEMS switch. The first contact of the bending beam 150 corresponding mating contact according to the invention with a glass wafer 200 educated:

This is a 700 micrometer thick glass wafer 200 used in which two trough-shaped trenches 210 . 220 are introduced, which are parallel to each other and perpendicular to the plane of the drawing. The ditch 220 is a multiple as wide as the ditch 210 , For this purpose, the glass wafer is first at those points of the glass wafer 200 , which are to remain unchanged, by means of a 100 nanometer thick silicon layer 230 coated. For this purpose, silicon is deposited on the glass wafer by means of LPCVD (LPCVD = Low Pressure Chemical Vapor Deposition) 200 applied. The applied silicon layer 230 is subsequently structured by means of lithography and unwanted areas of the silicon layer 230 removed by the RIE method.

The following are from the silicon layer 230 uncovered areas of the trough-shaped trenches 210 . 220 manufactured. These are the trenches 210 . 220 Etched using hydrofluoric acid.

After the etching of the trenches 210 . 220 becomes the silicon layer 230 removed by means of potassium hydroxide ( 11 ).

The superficial areas of the glass wafer 200 , which have not been etched with hydrofluoric acid, subsequently become with a 300 nanometer thick gold layer 240 metallized. In particular, the one between the two trenches 210 . 220 located area of the glass wafer 200 with a metallization 255 Mistake. In addition, a narrower ditch is also included 210 also edge region of a floor of the wider trench 220 with a metallization 250 provided which a mating contact for the contact of the bending beam 150 forms. Distanced from the metallization 250 is the narrower ditch 210 closer area of the bottom of the wider trench 220 with a gate metallization 260 provided after completion of the MEMS switch of the deflection of the bending beam 150 by means of supply with control signals.

For this purpose, gold is deposited, subsequently structured by lithography and excess gold removed by etching the gold. Alternatively, instead of using a gold layer 240 be metallized by means of a 20 nanometer thick chromium layer.

The inventive production of the MEMS switch is completed by the gold layer 240 of the glass wafer 200 to the outer silicon layer 80 of the SOI wafer with the metallization of the glass wafer is so flat joined together that the contacting of the bending beam 150 forming gold layer 120 the counter-contact forming metallization 250 is turned.

The on the strip 100 located metallization 110 becomes ( 13 ) with the between the trenches 210 . 220 located metallization 255 placed in flat contact and, for example, galvanically connected cohesively. This is the bending beam 150 fixed on two opposite sides by the bending beam 150 on the one hand by means of the insulator 40 with the rest of the SIO substrate 10 connected on the other hand via the interconnected metallizations 255 and 110 on the glass wafer 200 is connected.

In a further embodiment, the bending beam 150 not doped and - unlike in 13 shown - formed electrically conductive. This is the bending beam 150 not just with a metallization 120 at the free end of the bending beam 150 but the bending beam is along its entire longitudinal extent (ie, along its entire extent in the direction of the planar extensions of the layers of the silicon-insulator-silicon layer sequence 20 , ie metallized perpendicular to the thickness direction d). Along this extension also remains the outer glass layer 90 as in the field of metallization 120 of in 13 obtained embodiment shown. In comparison to 13 omitted in the embodiment, the doping of the superficial region 102 and the training of stripes 100 , Rather, the metallizations 110 and 255 from SIO substrate 10 and glass wafers 200 directly connected to each other by means of electroplating.

Not specifically shown, the inventive arrangement of MEMS switches comprises a plurality of MEMS switches, which are manufactured as described above. These are the MEMS switches with the same SIO substrate 10 manufactured and have extremely small deviations of the switching times from each other.

Claims (14)

A MEMS switch with a deflectable bending element (150), characterized in that the MEMS switch comprises a silicon-on-insulator substrate (10). A MEMS switch according to the preceding claim, wherein the silicon-on-insulator substrate (10) forms or comprises a silicon-insulator-silicon layer sequence (20). A MEMS switch according to any one of the preceding claims, wherein the flexure (150) comprises the silocon on insulator substrate (10) and / or the silicon on insulator substrate (10) comprises the flexure (150). A MEMS switch according to any one of the preceding claims, wherein the flexure (150) is disposed on an insulator layer (40) of the silicon-on-insulator substrate (10). Method for producing at least one MEMS switch, in particular according to one of the preceding claims, characterized in that in the method a silicon-on-insulator substrate (10) is used. A method according to the preceding claim, wherein the silicon-on-insulator substrate (10) forms or comprises a silicon-insulator-silicon layer sequence (20). Method according to one of the preceding claims, wherein for forming the / a bending element (150), a layer formed with silicon (70) is at least partially removed. Method according to one of the preceding claims, in which a layer is removed by using lithography and subsequent etching. Method according to one of the preceding claims, wherein for contacting the bending element (150) at least in areas an insulator layer (90) of the silicon-on-insulator substrate (10) is removed and these areas are metallized or an insulator layer (90) of the silicone On insulator substrate (10), at least partially metallized. Method according to one of the preceding claims, wherein for contacting the bending element (150), a silicon layer (80) of the silicon-on-insulator substrate is at least partially doped. Method according to one of the preceding claims, in which a mating contact (250) to the bending element (150) of the MEMS switch is produced by using a glass-formed substrate (200), preferably to form recesses (210, 220) in FIG Substrate (200) at least partially glass is removed, and is subsequently metallized. The method of any one of the preceding claims, wherein two or more MEMS switches are fabricated, wherein the MEMS switches are fabricated with the same silicon-on-insulator substrate (10). Arrangement comprising two or more MEMS switches, wherein the MEMS switches are MEMS switches according to one of the preceding claims or produced by a method according to one of the preceding claims. Arrangement according to the preceding claim, in which the MEMS switches are formed with the same silicon-on-insulator substrate (10).

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