Interferometer Device and Method for Producing an Interferometer Device

Abstract

The disclosure relates to an interferometer including a substrate, and an intermediate layer region applied on the substrate. A first mirror device and a second mirror device are aligned plane-parallel with one another and are separated from one another by a first distance and are framed in or on the intermediate layer region, the intermediate layer region removed in at least one of an inner region below the first mirror device and below the second mirror device. A laterally structured electrode including a first subregion and a second laterally separated subregion which are configured to be connected to different electrical potentials. The electrode arranged at a second distance from the first or the second mirror device, the first subregion extending in the inner region and arranged on the intermediate layer region and the second subregion extending in an outer region of the intermediate layer region.

Claims

1. An interferometer device, comprising: a substrate; an intermediate layer region applied on the substrate; a first mirror device and a second mirror device, which are aligned plane-parallel with one another and are separated from one another by a first distance and are framed in the intermediate layer region or are arranged thereon, the intermediate layer region removed in at least one of an inner region below the first mirror device and/or below the second mirror device; and a laterally structured electrode including a first subregion and at least one second subregion laterally separated therefrom and electrically insulated, which subregions are configured to be connected to different electrical potentials, the electrode arranged at a second distance from the first or the second mirror device, the first subregion extending in the inner region and being arranged on the intermediate layer region and the second subregion extending in an outer region of the intermediate layer region, such that at least one of the first mirror device and the second mirror device is movable electrostatically and parallel to the substrate through the first subregion in the inner region and such that the first distance is variable.

2. The interferometer device as claimed in claim 1, wherein the electrode comprises in the inner region a recess in an optical region of the interferometer device, and the first subregion and the second subregion laterally extend around the recess at least partially.

3. The interferometer device as claimed in claim 1 or 2, wherein the electrode comprises a ring electrode.

4. The interferometer device as claimed in claim 1, wherein the subregions of the electrode are fully separated laterally from one another and electrically insulated from one another by respective separating trenches.

5. The interferometer device as claimed in claim 1, wherein at least one of the first and the second mirror device comprises one of a Bragg mirror and a metal mirror.

6. The interferometer device as claimed in claim 1, wherein the first distance is less than the second distance.

7. The interferometer device as claimed in claim 1, wherein the first subregion comprises a bearing region which is laterally electrically insulated, and wherein one of the first and the second mirror device faces directly toward the electrode and comprises abutment studs in the inner region which extend away from a mirror surface of the electrode and are configured to be placed on the bearing region when the electrode is actuated.

8. The interferometer device as claimed in claim 1, wherein at least one of the first and the second mirror device comprises an undoped material in the inner region.

9. The interferometer device as claimed in claim 1, further comprising: an etch stop, which forms a side wall at the intermediate layer region laterally between the inner region and the outer region.

10. The interferometer device as claimed in claim 1, wherein at least one of the first and the second mirror device are connected to an electrical potential.

11. A method for producing an interferometer device, comprising: providing a substrate and a first sacrificial layer on the substrate; applying an electrode onto the first sacrificial layer and structuring the electrode into a first subregion and at least one second subregion separated laterally and electrically therefrom; applying a second sacrificial layer onto the electrode and onto the first sacrificial layer; arranging a first mirror device on the second sacrificial layer; applying a third sacrificial layer on the first mirror device; arranging a second mirror device on the third sacrificial layer in a plane-parallel fashion over the first mirror device at a first distance; and removing the second sacrificial layer and the third sacrificial layer to form an inner region below the first and the second mirror device by an etching method, the inner region extending at least over a part of the first subregion, while leaving a region, remaining in the interferometer device, of the first sacrificial layer, of the second sacrificial layer and of the third sacrificial layer which form an intermediate layer region so that the first mirror device and the second mirror device are framed in an outer region of the intermediate layer region or are arranged thereon, and the first subregion extends one of fully and partly in the inner region and is arranged on the intermediate layer region, and the second subregion extends in the outer region of the intermediate layer region.

12. The method as claimed in claim 11, wherein a recess is formed in the first subregion and in an optical region of the interferometer device, and the first sacrificial layer is removed in this recess.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be explained in more detail below with the aid of the exemplary embodiment given in the schematized figures of the drawing, in which:

[0042] FIG. 1 shows a schematized lateral cross section of an interferometer device according to one exemplary embodiment of the present invention;

[0043] FIG. 2a shows a schematized lateral cross section of an interferometer device according to a further exemplary embodiment of the present invention;

[0044] FIG. 2b shows a schematized lateral cross section of an interferometer device according to a further exemplary embodiment of the present invention;

[0045] FIG. 3 shows a plan view of an electrode according to one exemplary embodiment of the present invention; and

[0046] FIG. 4 shows a block diagram of the method steps according to the present invention.

[0047] In the figures, references that are the same denote elements that are the same or functionally equivalent.

[0048] FIG. 1 shows a schematized lateral cross section of an interferometer device according to one exemplary embodiment of the present invention.

[0049] The interferometer device 1 comprises a substrate 2; an intermediate layer region 3, which is applied on the substrate 2; a first mirror device SP1 and a second mirror device SP2, which are aligned plane-parallel with one another and are separated from one another by a first distance d12 and are framed in the intermediate layer region 3 or are arranged thereon, the intermediate layer region 3 being removed in an inner region IB below the first mirror device SP1 and/or below the second mirror device SP2; and a laterally structured electrode E, which comprises a first subregion E1 and at least one second subregion (not shown) laterally separated therefrom and electrically insulated, which subregions can be connected to different electrical potentials, the electrode E being arranged at a second distance d2 from the first or the second mirror device SP1; SP2, the first subregion E1 extending in the inner region IB and being arranged on the intermediate layer region 3a and the second subregion E2 extending in an outer region AB of the intermediate layer region 3, so that the first mirror device SP1 and/or the second mirror device SP2 is movable electrostatically and parallel to the substrate 2 through the first subregion E1 in the inner region IB and the first distance d12 can be varied. FIG. 1 shows a cross section of a contact guide from the first subregion E1 through the intermediate region 3, and for example, to the intermediate region 3a, and to the through-contact K1 thereof, which runs through the intermediate region 3b and 3c. By the actuation, a substantially parallel deflection of one of the mirror devices SP1, SP2 relative to the other mirror device may be carried out in the inner region, and particularly in the optical region OB.

[0050] By variation of the distance of the mirror devices from one another, a transmission wavelength of the interferometer device (Fabry-Perot interferometer) can be modified.

[0051] The inner region IB may advantageously correspond to that region in which the second and third sacrificial layers 3b and 3c have been removed, i.e. the mirror devices SP1 and SP2 are freed. The intermediate layer region 3 may therefore constitute anchoring of the mirror devices and of the electrode in the outer region AB and fasten them on the substrate 2 mechanically and in an electrically insulated fashion. The first subregion E1 may be arranged on a residual region of the first sacrificial layer 3a, i.e. on a residual portion of the intermediate layer region 3, which may extend into the inner region IB under the first subregion E1. FIG. 1 shows a recess in the optical region OB, which recess may extend from the mirror devices to the substrate 2 and in which recess the electrode is also removed or was not initially formed there. An antireflective layer AR may be arranged on the substrate 2, for example on both sides, in the optical region OB. On an underside of the substrate 2, a mask B, by which light incidence or emergence and for instance the angle thereof can be influenced or filtered may be arranged outside the optical region. The second subregion of the electrode may advantageously be embedded into the intermediate layer region and enclosed by it on both sides. Contacting K of the mirror device, and advantageously of that embedded in the intermediate layer region, may be carried out from the upper side by means of a contact K through the intermediate layer region. The contacting of the subregion E1 may also be fed by means of a through-contact, for instance from an upper side of the intermediate layer region, through the latter. The arrangement of the contacts is represented merely by way of example and may be adapted in respect of the specific electrode arrangement. By means of the first subregion E1, the closest mirror device may therefore be actuated by the potential applied to the first subregion E1 and by means of a counter-electrode of the mirror device, so that the central region of the mirror device in the region of the optical region can be deflected parallel to the other mirror device. Deformation of the mirror device during actuation advantageously takes place primarily in the inner region IB but outside the optical region, so that mirror planarity and parallelism in the optical region can be promoted. For this effect, with this structure, lateral presence of different potentials on the mirror device is advantageously not necessary, which may represent a significant simplification of production. Over the first subregion E1, the mirror device may comprise its own electrode as a separate actuation electrode, which however may also be framed in the mirror device or formed there.

[0052] A separate electrode may, for example, be formed on the mirror device by deposition of an electric material or structuring of a conductive layer on the mirror device, or deliberate doping of a semiconductor material (for instance silicon). A significant reduction of the parasitic capacitances may be achieved by a reduction of the areas contributing to the capacitance (only necessary regions formed as electrodes). The separate electrode may, for example, be configured as a ring. In the case of forming an electrode region in the mirror device (for instance with doping), the parasitic capacitance may be restricted to a small area of the contact and a supply line to the counter-electrode.

[0053] Bending of the electrode may, for example, be prevented or reduced by a sufficient stiffness of the intermediate layer region 3, to which end the intermediate layer region 3 may have a sufficient thickness.

[0054] The basic distance d12 before the actuation may be known for the corresponding interferometer.

[0055] The reflectivity of the mirror devices SP1 and SP2 may, for example, be produced by metal layers on carrier membranes or a dielectric DBR membrane stack (Bragg mirror).

[0056] FIG. 2a shows a schematized lateral cross section of an interferometer device according to a further exemplary embodiment of the present invention.

[0057] The embodiment of FIG. 2a differs from FIG. 1 only by the etch stop 4 and by the bearing region E1a. The first subregion E1 may comprise a bearing region E1a, which is laterally electrically insulated from the other subregions of the electrode E and E1, and wherein the first or the second mirror device SP1; SP2 faces directly toward the electrode E.

[0058] The bearing region E1a may be delimited and insulated from the first subregion E1 by a trench G in the intermediate layer region 3. The trench G may extend through the intermediate layer region 3 as far as the substrate 2.

[0059] Antireflection layers AR may be arranged on all interfaces in the optical path that are not part of the mirror devices. By the masks B, it is possible to form an optical region OB which may delimit the optical light path and the angle of incidence by reflection and/or absorption.

[0060] In the intermediate layer region 3, an etch stop 4, which may for example comprise the material of one of the mirror devices SP1, SP2, may be formed on a side wall laterally between the inner region IB and the outer region AB. The etch stop may therefore already belong to the outer region AB. Furthermore, there may be a possibility for protection against undefined undercut etching in sacrificial layer processes. This etch stop 4 may be formed during production as a trench in the second and third sacrificial layers 3b and 3c and be filled with the mirror material, and have a lower etching rate than the sacrificial layers. Such an etch stop layer may also be formed on a side wall of the intermediate layer region of the first sacrificial layer, for instance toward the optical region (not shown). This may likewise be produced by trench formation. Any topographies generated, protruding vertically beyond the electrode or the mirror device, could be compensated for by methods of thinning back. Precise definition of the membrane clampings of the mirror devices may be achieved by the etch stop 4, since this is usually determined by how far the membranes are freed during the sacrificial layer process, which is typically subject to large variations. In this way, any nonideal arrangement of the etching accesses as well as a varying etching rate may likewise be compensated for. The etch stop 4 may be produced during production in such a way that it can be drawn down onto the bearing region E1a. Between the first subregion E1 and the second subregion, there may also be a trench in the intermediate layer region 3 below the electrode E (this is not shown). This may lead to significantly simplified process management during production. In the case of a mirror membrane which does not contain a layer that is electrically insulating and at the same time sufficiently resistant to the sacrificial layer etching (which is often the case), in order to achieve an etch stop, in a conventional process sequence it would otherwise be necessary to deposit at least one additional layer and structure it in such a way that no perturbing topography is formed. Such etch stops may also be formed in other regions of the interferometer device, for example in the region of electrical contacts and feeds.

[0061] FIG. 2b shows a schematized lateral cross section of an interferometer device according to a further exemplary embodiment of the present invention.

[0062] FIG. 2b differs from FIG. 2a in that in FIG. 2b no etch stop is shown and abutment studs AN of the first mirror device SP1 may protrude from the latter in the direction of the electrode E1. Furthermore, there may be further insulated regions E1a (bearing regions) of the electrode E, onto which it is possible to place (during actuation) abutment studs, which may extend away from a mirror surface to the electrode E and can be placed onto the insulated region during actuation. The abutment studs AN can prevent contact of the mirror device SP1; SP2 and the electrode E and generally limit the deflection of the mirror device, may themselves be electrically conductive and may be placed outside the potential of the actuation electrode E1. If contact of the abutment studs with the electrode E1 nevertheless takes place in the insulated region E1a, this may be released again easily. By means of the abutment studs, it is possible to prevent welding to the tips of the abutment studs taking place in the event of contact with the electrode E in the insulated region and an electrical voltage applied to the first subregion E1, the abutment studs conventionally either needing to be electrically separated from the rest of the mirror potential or needing to consist of an insulator. According to the invention, the abutment studs may comprise a conductive material or the material of the mirror device, which may lead to simplified process management. The bearing regions E1a may be laterally adjacent directly to the optical region or lie further out in the inner region IB.

[0063] FIG. 3 shows a plan view of an electrode according to one exemplary embodiment of the present invention.

[0064] The electrode E may comprise a ring electrode with a recess in the middle, i.e. for the optical region of the interferometer device. By suitable structuring of the conductive layers into subregions E1, E2 and so on, different potentials may be applied laterally separately from one another by the contacts K1, K2, for example from above. These contacts may be drop-shaped, round, rectangular or shaped in the form of a polygon. Lateral insulation of the individual subregions, which may constitute rings, may be achieved by separating trenches TG, by which an interruption of the ring structures may be obtained. In this case, so-called feed-throughs may be formed. In addition, a conductive layer, for example in the electrode layer E, may be used as a buried conductive track of a contact K1, K2, K3 in order to produce contacting below other conductive layers and optionally contact these by means of the buried conductive track. This may be achieved by subsequent deposition of an insulator layer. The electrical contacts may in general also be produced in another way.

[0065] FIG. 4 shows a block diagram of the method steps according to the present invention.

[0066] In the method for producing an interferometer device, a substrate and a first sacrificial layer on the substrate are provided S1; an electrode is applied S2 onto the first sacrificial layer and the electrode is structured S2a into a first subregion and at least one second subregion separated laterally and electrically therefrom, which extends laterally around the first subregion; a second sacrificial layer is applied S3 onto the electrode and onto the first sacrificial layer; a first mirror device is arranged S4 on the second sacrificial layer; a third sacrificial layer is applied S5 on the first mirror device; a second mirror device is arranged S6 on the third sacrificial layer in a plane-parallel fashion over the first mirror device at a first distance; and the second sacrificial layer and the third sacrificial layer are removed S7 in an inner region below the first and the second mirror device by means of an etching method, the inner region extending over the first subregion, and a region, remaining in the interferometer device, of the first sacrificial layer, of the second sacrificial layer and of the third sacrificial layer forming an intermediate layer region so that the first mirror device and the second mirror device are framed in an outer region of the intermediate layer region or are arranged thereon, and the first subregion extends in the inner region and is arranged on the intermediate layer region, and the second subregion extends in the outer region of the intermediate layer region.

[0067] Furthermore, a recess may be formed in the first subregion and in an optical region of the interferometer device, and the first sacrificial layer may be removed in this recess. The formation of the recess may already take place during the arrangement or provision of the electrode. It is likewise possible for the method steps to be carried out in an order other than that mentioned. For example, the electrode may be arranged between the mirror devices or over them as an upwardly closing element, i.e. on the third sacrificial layer or between the second and third sacrificial layers.

[0068] The present invention has been fully described above with the aid of the preferred exemplary embodiment, it is not restricted thereto but may be modified in a variety of ways.