DE10243511A1 - Method and micromechanical device - Google Patents

Abstract

A method and a device are proposed in which a high-frequency component with a metallic conductor is produced by means of a low-pressure temperature method.

Description

State of the art

The invention is based on one Method and a device according to the genus of the secondary Expectations. Coils are already generally known, using surface micromechanical technology getting produced. It is particularly provided that the coil is provided as a self-supporting coil over a deep cavity is. To create such a cavity, it is according to the state the technology provided that the cavity is created by that in a first step in the area of the later cavity substrate material is oxidized and then by means of an etching medium attacking the oxidized material the cavity is created. This has the disadvantage of producing of the oxidized substrate material requires high temperatures are. As a result, the manufacture of such a coil is not compatible with the production of standard semiconductor components, for example in CMOS technology.

Advantages of invention

The method according to the invention and the device according to the invention with the features of the subordinate claims have the Advantage that according to the invention not an oxide, but Silicon is used as a sacrificial layer. The area of the sacrificial layer is first deeply structured, for example using Deep Reactive Ion Etching DRIE and then with an isotropic etching process laterally complete etched for example by means of a xenon difluoride or chlorine trifluoride process. Alternatively, you can in the isotropic etching process wet chemical processes such as KOH etching are also used become. The method according to the invention is characterized by a simple process sequence and thus an inexpensive one execution across from the state of the art. In contrast to the prior art oxidation can be dispensed with. The proposed process is a low temperature process which makes it easy for integrated Can use sensors, which additional monolithic to the high-frequency component further circuit elements provide integrated. About that there is also the advantage that the conductor tracks that are brought in are completely included Isolators can be passivated because the etching process Silicon extremely selective across from Insulators such as silicon dioxide, silicon nitride or also dielectrics with a low K-value are etched. The isotropic etching step but is also extremely selective across from Track materials such as aluminum, aluminum alloys with copper or / and silicon, TiN or tungsten. The coil layers or the metallic conductors can in the case of gold as a metallic conductor, easily with a passivation before the caustic attack protected become.

By the measures listed in the subclaims are advantageous developments and improvements in the secondary claims specified method and the device possible. Particularly advantageous is that the method is intended to be CMOS-compatible. In order to Is it possible, electronic circuits together with the high-frequency component integrate on the same substrate as with a conventional Technology for manufacturing microelectronic circuits, for example CMOS. It is also advantageous that the at least one metallic conductor is structured, that subsequently one Tiefenätzschritt carried out and that after that another isotropic etching step is carried out. This makes it possible particularly inexpensive and the high-frequency component with a low temperature load manufacture. It is also advantageous that the deep etching step is provided as a DRIE step. This can be a special inexpensive Manufacturing technology used become.

It is also advantageous that the further isotropic etching step is carried out using a XeF ₂ , ClF ₃ , BrF ₃ or SF ₆ plasma or wet-chemically using TMAH or KOH or HNO ₃ / HF etchant. This makes it possible according to the invention to carry out the isotropic etching step in a particularly simple and cost-effective manner. It is also advantageous that the at least one metallic conductor is a coil. This makes it possible according to the invention to produce a component which is to be produced particularly frequently and with great effort using the method according to the invention. It is also advantageous that the metallic conductor is self-supporting or is provided on a supporting insulation layer. In the case of a self-supporting conductor, this makes it possible to produce particularly good insulation and a particularly large distance from the substrate, and in the case of a conductor which is provided on a supporting insulation layer, it is possible to increase the mechanical stability.

drawing

An embodiment of the invention is shown in the drawing and in the description below explained in more detail. It demonstrate

1 a known coil arrangement according to the prior art,

2 a first preliminary stage of the device according to the invention,

3 a second preliminary stage of the device according to the invention,

4 a third preliminary stage of the device according to the invention,

5 a fourth preliminary stage of the fiction moderate device,

6 a fifth preliminary stage of the device according to the invention,

7 a sixth preliminary stage of the device according to the invention,

8th a seventh preliminary stage of the device according to the invention and

9 the device according to the invention.

description of the embodiment

The development of microelectromechanical Components for High frequency applications primarily target high frequency oscillators or high-frequency resonators, the frequency of which is due to mechanical components is determined. Across from Purely electrical resonant circuits have mechanical microelectromechanical ones Components or resonators have the advantage of very high quality of Q = 1000 and achieve more. This will result in low losses in the high Frequencies, for example a few 10 MHz, allows. According to the invention, Radio frequency resonant circuits and circuits complete with microelectromechanical components and electronic integrated Equip circuits for full integration on one To achieve chip or a substrate. In addition to resonators, too Filters, for example coupled band filters, tunable capacities or inductors represent in micromechanical systems, for example for LC resonators. The challenges of radio frequency microelectromechanical Systems lies among other things in the capping, in particular the Vacuum capping of high quality stones and in the implementation of tiny plate distances in tunable capacities and still in the implementation of very large insulation distances, for example in coil designs or conductor tracks to reduce the dielectric losses in insulation layers or conductive component components.

Coils have generally been produced using surface micromechanical technology. This is in 1 such a coil construction is shown according to the prior art. In 1 is a top view of a radio frequency coil is shown on the left side of the figure, in which the coil winding with the reference numeral 4 , the returning, higher lying coil path with the reference symbol 3 and the cavern below the coil, which is provided for air insulation, with the reference symbol 5 is designated. In the right part of the 1 A corresponding cross section through the coil body of such a coil arrangement is shown, the substrate, in particular silicon substrate, with the reference symbol 1 , an insulation oxide with the reference symbol 2 , the returning coil conductor track with the reference symbol 3 , the coil winding with the reference symbol 4 and the cavern again with the reference symbol 5 is designated. At in 1 Known coils, not shown, are etched in the sacrificial layer area below the coil or below the coil winding using a DRIE (Deep Reactive Ion Etching) process to a depth of between 50 and 100 μm. The silicon supports are completely oxidized in a subsequent oxidation process and covered with an oxide in a CVD (Chemical Vapor Deposition) process. This creates an almost planar oxide surface on which additional layers for the coil construction can be applied. Due to the large thickness of the oxide block that is formed, capacitances between the coil and the substrate are greatly reduced and losses are thus reduced. Furthermore, it is also generally known that this oxide support construction, as in 1 shown, with etching media containing hydrofluoric acid, for example BOE (buffered oxide etch), is removed selectively with respect to the coil materials and the substrate layers as a sacrificial layer. This creates a cantilevered bobbin over a deep cavity, which in 1 with the reference symbol 5 is designated. Due to the large distance from conductive surfaces and the low dielectric constant of the cavity insulator (in particular air), only small losses occur during high-frequency operation of the coil.

The method according to the invention provides a Manufacture self-supporting high-frequency component, the component is provided in particular as a coil. The invention cannot only for the insulation of coils are used, but is in principle also on other component components in high-frequency components applicable, such as conductor tracks etc. According to the invention Process CMOS compatible, i.e. it can be on the same substrate like the high-frequency component also microelectronic circuits by means of a usual Process technology, especially CMOS technology or be provided.

In the 2 to 9 the manufacturing process according to the invention is described on the basis of various preliminary stages and finally the device according to the invention.

In 2 a first preliminary stage of the device according to the invention is shown. On a substrate 10 , which is provided in particular as a silicon substrate, is a first insulation layer 21 applied, which according to the invention can be provided in a structured manner. The first layer of insulation 21 is made of silicon dioxide or silicon nitride, for example.

Iri 3 is a second preliminary stage of the device according to the invention, again with the substrate 10 , the first layer of insulation 21 and a first conductive layer 31 , shown. The first guiding layer 31 is provided in a structured manner and forms part of the at least one according to the invention seen metallic conductor. The first guiding layer 31 is therefore provided in particular from a metal such as aluminum, gold and the like. Alternatively, it can also be provided that silicon is the material of the conductor of the first conductive layer 31 to use. However, the sheet resistance should be small, which is why the invention provides for the use of metals.

In 4 A third preliminary stage of the device according to the invention is shown. In addition to the substrate 10 , the first layer of insulation 21 and the first conductive layer 31 is a second layer of insulation 22 shown. For the second layer of insulation 22 is in particular the same material as for the first insulation layer 21 provided, in particular silicon dioxide or silicon nitride. As in the sectional view of the 4 shown is the second insulation layer 22 also structured.

In 5 A fourth preliminary stage of the device according to the invention is shown. In addition to the substrate 10 , the first layer of insulation 21 , the first conductive layer 31 and the second insulation layer 22 is a second guiding layer 32 shown. The second guiding layer 32 is in certain and in 5 with the reference symbol 39 areas provided with the first conductive layer 31 connected so that an electrically low-resistance contact between the first conductive layer 31 and the second conductive layer 32 arises. The first guiding layer 31 and the second guiding layer 32 together form the metallic conductor. In 5 . 6 . 7 . 8th and 9 is a cross-sectional view of a coil body indicated as a metallic conductor. Also for the second conductive layer or the second interconnect level 32 come for the first guiding layer 31 materials already described in question. Optionally, the in 5 illustrated preliminary stage of the device according to the invention still a third isolation level, but in 5 is not shown.

In 6 A fifth preliminary stage of the device according to the invention is shown. In the area of the component in which there is no layer of the metallic conductor 31 . 32 located - compare in particular the top view in the left part of the 1 - It is possible to carry out a deep etching to create a cavity below the conductor structure. For this purpose there is first an opening through the insulation layers 21 . 22 to run through. Such openings are in the 6 with the reference symbol 41 Mistake. Next to the openings 41 is in 6 also the substrate 10 , the first layer of insulation 21 , the second layer of insulation 22 , the first conductive layer 31 and the second guiding layer 32 shown. To open the one with the reference symbol 41 provided areas, it is particularly provided according to the invention that a large-area opening or a large-area perforation of the areas 41 arises. A dry etching method, for example reactive ion etching, is preferably used for this. With this opening 41 become the first layer of insulation 21 , the second layer of insulation 22 and an optional third insulation layer is opened.

In 7 a sixth preliminary stage of the device according to the invention is shown. Here, the from 6 with the reference symbol 41 provided open areas by means of a deep etching step down into the substrate 10 expanded into the cavern precursors 42 to build. In the deep etching step, the DRIE method is used in particular and an etching depth of 10 to 200 μm is achieved. Here it is provided according to the invention to provide an end point check or to carry out the deep etching without an end point check. Furthermore, in 7 again the substrate 10 , the first and second insulation layers 21 . 22 and the first and second guiding layers 31 . 32 shown.

In 8th the seventh preliminary stage of the device according to the invention is shown. Here, the cavern precursors 42 an isotropic etching step is carried out into it 7 and 8th with the reference symbol 11 designated supports of the micromechanical structure removed. The isotropic etching step is carried out according to the invention in particular by using etching media such as XeF ₂ , ClF ₃ , BrF ₃ or SF ₆ , ie by means of a plasma etching process or also by means of a wet chemical etching process with etching media such as TMAH, KOH, HNO ₃ / HF and the like. The etching medium is in 8th with the reference symbol 45 Mistake. Otherwise the substrate is again 10 , the first and second insulation layers 21 . 22 and the first and second guiding layers 31 . 32 shown.

In 9 The device according to the invention is shown, the support structures being formed by the isotropic etching process 11 removed and a cavern 44 under the structure of the metallic conductor 31 . 32 was generated. In 9 is again the substrate 10 , the first and second insulation layers 21 . 22 and the metallic conductor 31 . 32 shown.

According to the invention, it is thus possible to use a CMOS compatible Any high-frequency components as micromechanical structures manufacture. It is particularly important that when carrying out the Process not too high temperatures are required. Such one Low temperature process is characterized in that essential lower temperatures are necessary than those temperatures that are needed in the formation of thermally oxidized silicon. According to the invention, these are in particular provided as temperatures below 600 ° C.

Claims (8)

Method for producing a micromechanical device with at least one conductor provided as a high-frequency component ( 31 . 32 ), characterized in that the process is a low temperature process. A method according to claim 1, characterized in that the process is CMOS compatible. Method according to claim 1 or 2, characterized in that first the at least one metallic conductor ( 31 . 32 ) that a deep etching step is then carried out and that an isotropic etching step is then carried out. A method according to claim 3, characterized in that the deep etching step is provided as a DRIE step. Device according to claim 3, characterized in that the isotropic etching step is carried out by means of a XeF ₂ , ClF ₃ , BrF ₃ or SF ₆ plasma or wet-chemically by means of TMAH or KOH or HNO ₃ / HF. Method according to one of the preceding claims, characterized in that the at least one metallic conductor ( 31 . 32 ) is a coil. Micromechanical device with at least one metallic conductor provided as a high-frequency component ( 31 . 32 ), produced by a method according to one of the preceding claims. Apparatus according to claim 7, characterized in that the metallic conductor ( 31 . 32 ) is self-supporting or provided on a load-bearing insulation layer.