DE10229038B4 - Verkappes microstructure device with high-frequency feedthrough - Google Patents

Abstract

Microstructure component, with a base body (11), wherein on the base body (11) in regions a planar conductor structure (17, 17 ', 17' ', 17' '') is arranged, and a sealing region (16) is provided, in which the Conductor structure (17, 17 ', 17' ', 17' '') of the base body (11) and a glass (19) is enclosed, wherein the sealing region (16) in the longitudinal direction of the conductor pattern (17, 17 ', 17' ' , 17 '' ') has a width b1, and wherein a capping (15) is provided, which protects a microelectronic or microelectromechanical component (12) or a sensor element together with the base body (11) from external influences or gas-tight and / or moisture-proof is closed, wherein the cap (15) with the main body (11) via the gasket forming glass (19) is connected, and wherein the conductor pattern (17, 17 ', 17' ', 17' '') of which in an interior space (21) the microelectronic or microelectromagnetic component (12) or the capping (15) or Sensor element on the base body (11) through the sealing region (16) in an outer space (22) of the capping (15) is guided, characterized in that the conductor structure (17, 17 ', 17' ', 17' '') in shape a coplanar line for high-frequency electromagnetic waves with two ground lines (17 ', 17' ''), which include a signal line (17 '') is formed and between the signal line (17 '') and in each case a ground line (17 ', 17' '') is an air gap (24) filled by the glass (19), wherein in an environment of the sealing region (16) of the air gap (24) is widened in each case to a common air gap (23), wherein the area with the respective air gap (23) in the longitudinal direction of the conductor structure (17, 17 ', 17' ', 17' '') has a greater width b2 than the width b1 of the sealing region (16).

Description

The invention relates to a microstructure component, in particular a microstructured high-frequency component, according to the preamble of the main claim.

State of the art

Out DE 100 37 385 A1 there is known a micromechanically fabricated high frequency shorting switch having a thin metal bridge stretched between two ground lines of a coplanar waveguide. This high frequency short circuit switch is useful, for example, in ACC (Adaptive Cruise Control) or SRR (Short Range Radar) applications in automobiles, and operates at frequencies typically of 24 gigahertz or 77 gigahertz.

In addition, a variety of other microstructure components or microsystem components, for example, for applications in the field of high frequency technology based on silicon known. These are also referred to as MEMS components (microelectromechanical structures / systems) or HF MEMS components (high frequency microelectromechanical structures / systems).

As a rule, it is necessary in the case of microstructure components and in particular microstructured high-frequency components to protect them from environmental influences such as moisture, air, dirt particles or other external media or gases, which often happens with the aid of a capping. However, in order not to impair the function of the microstructure component enclosed by the capping or not too strongly, it is necessary to introduce a conductor structure for electrical contacting or activation of the microstructure component into the capping.

At first, there is the problem of ensuring the gas-tightness or moisture-tightness. Next must be ensured in the implementation of the conductor structure from the outer space of the capping in the interior, in particular in the case of a high-frequency component, that the conductor structure for high-frequency electromagnetic waves is continuous, d. H. There must not be any appreciable damping or disturbance of the propagation of the electromagnetic waves on the conductor structure.

See B. Pillaus, S. Eshelman, A. Malczewski, J. Ehmke, C. Goldsmith, "Ka-band RF MEMS Phase Shifters for Phased Array Applications," 2000 IEEE Radio Frequency Integrated Circuits (RFIC) Symposium Digest of Papers, pp 195 to 199, is proposed as a sealing material for a run on a body conductor structure, which is in communication with a microstructure device, in the region of the capping a polymer. However, this is not suitable to meet the requirements in automotive technology in terms of life and reliability.

From the Scriptures JP 11135661 A For example, a microstructure element for a high-frequency range is known. In this case, a high-frequency element is encapsulated on a substrate via an insulating cover element by means of glass. An arranged on the substrate track for the transmission of high frequencies is guided through the glass to the outside and sealed from the glass. In the glass area, the conductor track is made thinner.

The font DE 199 45 178 C2 shows the execution of a measuring tip for high-frequency measurement. Here, the measuring tip is designed at its end for contacting with planar structures with a coplanar conductor structure, which is partially surrounded by a dielectric. Between each two conductors of the coplanar conductor structure, a gap is provided in each case such that a constant characteristic impedance results. For this purpose, the gap is made wider in the region of the conductor structure surrounded by the dielectric than in the region outside the dielectric.

The object of the present invention was to hermetically seal a planar conductor structure running on a base body in a sealing area against media such as air and moisture, while at the same time not impairing the transmission properties of the conductor structure for high-frequency electromagnetic waves, in particular in the gigahertz range.

Advantages of the invention

The microstructure component according to the invention has the advantage over the prior art that on the one hand an effective shielding of the microstructure component against undesired environmental influences is achieved, and on the other hand, the conductor structure by the provided in the sealing area glass, which encloses the conductor structure together with the main body, in terms of their transmission properties or attenuation properties for high-frequency electromagnetic waves, which are guided on the conductor structure, is not or not significantly impaired. In particular, the glass used is sufficiently long-term stable and temperature resistant for applications in automotive engineering.

Advantageous developments of the invention will become apparent from the measures mentioned in the dependent claims.

It is thus particularly advantageous if the substrate or the printed circuit board on which the microelectronic or microelectromechanical component or sensor element is arranged together with the base body and the capping has a recess which is preferably somewhat larger in dimensioning than the capping. In this case, the capping can be sunk particularly easily in the recess, and it is possible to construct the microstructure device in conventional flip-chip technology. It should be noted that the flip-chip technology allows the use of particularly short and in particular not freely extending in space conductor structures for electrical contacting, so that, especially in high-frequency components unwanted spurious effects can be suppressed.

In addition, it is advantageous if the conductor structure is made thinner in terms of its height in the sealing region or in the sealing region and a lateral environment of the sealing region than outside this region. As a result, a lower topography to be sealed arises in the sealing area, which leads to greater reliability and improved process reliability.

For sealing the conductor structure in the sealing region, a conventional glass frit is preferably used as a sealing material, as it is available from various manufacturers as a paste. Such, initially paste-like glass frit can be screen-printed and then converted into a glass, for example by heating, which leads to a melting of the glass frit.

In certain applications, finally, it is advantageous if the capping is designed so that no cavern forms between the base body and the substrate. In this case, the capping is carried out, for example, as a flat plate, which is kept at a distance over the sealing region, which is preferably designed as a frame made of the glass frit melted into glass. This embodiment allows a simplified process management in the production of the capping. In addition, the increase in the effective dielectric constant achieved in this area makes it possible to reduce the circuit or conductor structure with respect to phase-sensitive line sections.

drawings

The invention will be explained in more detail with reference to the drawings and the description below. It shows 1 a microstructure device according to the prior art in section, 2 an inventive microstructure device in section, 3 a section from 2 . 4 a cut through 3 along the marked cutting line, 5 a top view 4 , wherein the capping according to 4 is not shown, so that the glass is directly visible in the sealing area, and 6 a top view 4 in one too 5 alternative embodiment, again the capping according to 4 not shown.

embodiments

The 1 shows a known from the prior art embodiment of a microstructure device, wherein a microelectronic or micro-electro-mechanical component, not shown in detail 12 For example, a microfabricated high-frequency switch, a high-frequency diode, a high-frequency transistor or a manufactured in silicon surface micromechanical sensor element in a base body 11 integrated or arranged on the surface. The main body is for example a silicon wafer. Next is in 1 shown that the main body 11 over a circuit board 10 or more generally a substrate and by means of an electrically conductive connection 14 that with connection cables 13 communicating, is electrically contactable, so that over on the circuit board 10 led electrical connection lines 13 and the electrically conductive connection 14 that in the main body 11 integrated microelectronic or microelectromechanical component 12 is electrically controlled.

For example, in the main body 11 a device with a capacitor according to DE 100 337 385 A1 integrated, ie the circuit board 10 facing part of the body 11 is superficially provided with a coplanar waveguide which has a capacitor in a section.

The 2 shows in continuation of 1 a first embodiment of the invention. Specifically shows 2 a microstructure device 5 , For example, a microstructured high-frequency component, wherein the main body 11 which again consists of silicon in the illustrated example, superficially on its the circuit board 10 or the substrate-facing side, for example, with a manufactured in micromechanics, not shown in detail high-frequency switch according to DE 100 37 385 A1 is provided, ie this forms the microelectronic or microelectromechanical component 12 ,

It should be emphasized, however, that on the surface of the main body 11 Alternatively, another, largely arbitrary, microelectronic or microelectromechanical integrated therein Component, as they are widely known from the prior art, may be provided or integrated. In this respect, the component can 12 also a high-frequency diode, a high-frequency transistor or a manufactured in silicon surface micromechanical sensor element, for example, a rotation rate sensor or a pressure sensor element, be.

In the illustrated example with the high-frequency switch according to DE 100 37 385 A1 runs on the circuit board 10 facing surface of the body 11 according to 2 a ladder structure 17 in the form of structured gold planar tracks. The conductor structure is preferred 17 a coplanar line with two ground lines 17 ' . 17 ''' that has a signal line 17 '' Include, like this DE 100 37 385 A1 also already known.

The 2 finally shows that the circuit board 10 partially a recess 20 has, and that on the circuit board 10 facing side of the body 11 a capping 15 in the form of a cap on the body 11 is applied. The capping 15 closes together with the main body 11 a cavern 18 or an interior 21 one about the capping 15 from one outside the capping 15 located outside space 22 is disconnected. Next to it is the capping 15 in one or more sealing areas 16 , which preferably form a peripheral frame ("bonding frame"), with the main body 11 connected, wherein at the same time the conductor structure 17 in the interior with the component 12 is connected through the sealing area 16 from the interior 21 in the outside space 22 is guided where the ladder structure 17 with the connection 14 , which consists of an electrically conductive material, and conventional connecting cables 13 on the circuit board 10 are guided, electrically contacted and can be controlled. In particular, over the connecting lines 13 and the connections 14 the ladder structure 17 with high-frequency electromagnetic waves in the frequency range above 10 MHz, preferably above 1 GHz, are applied. The sealing area 16 apart from the ladder structure carried out by it 17 from a glass 19 that was produced by means of a molten glass frit.

The 3 shows an enlarged section 2 , where the sealing area 16 with the glass 19 is more clearly recognizable.

The 4 shows a cut through 3 along the marked section line in the sealing area 16 , whereby the basic body 11 , the sealing area 16 with the glass 19 and the capping 15 become more visible. Next is in this illustration, the ladder structure 17 clearly recognizable, in the form of a coplanar line with a ground line 17 ' , a signal line 17 '' and a mass line 17 which are at least partially parallel to each other, is formed. One recognizes that the ladder structure 17 on the surface of the main body 11 passes and through the sealing area 16 is passed. The glass 19 thus separates together with the main body 11 the interior 21 from the outside space 22 hermetically sealed off.

The 5 shows a plan view 4 from the direction of the capping 15 , where in 5 the capping 15 is missing, ie one sees directly on the basic body 11 with the ladder structure running on it 17 in the form of a coplanar line with ground line 17 ' , Signal line 17 '' and ground line 17 ''' , wherein the conductor structure 17 in the sealing area 16 through the glass provided there 19 is covered. Between ground line 17 ' and signal line 17 '' or between signal line 17 '' and ground line 17 ''' there is always one of the glass 19 filled air gap 24 ,

For the preparation of the structure according to the 2 . 3 or 4 was first a low-melting glass frit as a sealing material, for example by screen printing on the end faces of the capping 15 applied in the form of a frame ("bonding frame"). Such, as low as possible melting glass frits, which preferably have a PbO ₂ content of more than 80%, for example, by the companies Schott-DESAG AG, Grünenplan, or Ferro Corporation, Cleveland, USA, prepared as a paste and sold.

In particular, the sealing glass from Schott-Desag, which is available under Glass No. 6, is suitable. 8330, or one of the seal glasses offered by Ferro Corp under the category "Sealing Glasses".

Subsequently, the printed glass frit was then transferred via a temperature treatment in a suitable gas atmosphere, for example inert gas, into a glass. This glass can then be reheated if necessary and thereby softened or alternatively processed while still warm. Finally, then the capping 15 with the frame of glass by mechanical pressure with the with the ladder structure 17 provided surface of the body 11 brought into contact and connected so that the essentially of the glass 19 formed sealing area 16 forms, which is formed according to the shape of the glass frame and the conductor structure 17 includes, and the desired hermetically sealed separation of interior space 21 and outdoor space 22 guaranteed.

A significant advantage of the sealing of the interior 21 over the glass 19 with the im sealing area 16 guided ladder structure 17 This is because glass is very well suited for carrying high-frequency electromagnetic signals. Thus, for example, metallic, planar conductor tracks, as are typical for a coplanar, interference and low-loss high-frequency electromagnetic signals through the glass 19 be passed.

In the integration of high-frequency components in a circuit environment on a circuit board so far usually not the otherwise conventional connection techniques such as wire bonding and wireframes are used, but active components such as high-frequency diodes or high-frequency transistors applied unhoused in flip-chip technology. In this respect, the aim is the flip-chip technology here in connection with packaged or disguised components 12 ie using the capping 15 to maintain. In this way, the advantages of established technology and the electronic advantages of flip-chip technology can be combined with the advantages of a capping. In addition, this leads to reduced investments in production facilities.

Against this background is also the recess 20 provided in the illustrated embodiment, for example, in the circuit board 10 has been milled. It allows to keep the usual flip-chip technique. The recess 20 is incidentally opposite the capping 15 preferably slightly larger dimensions, so that the capping 15 after assembly at least partially into the recess 20 intervenes. To make a reliable connection to the circuit board 10 to ensure it can continue into the recess 20 a so-called "underfiller" can be applied.

The capping 15 is in the embodiment according to 2 respectively. 3 as in plan view, for example, circular or rectangular cap executed. In principle, however, it is also possible the capping 15 only in the form of a simple plate to perform in the sealing area 16 through the glass provided there 19 opposite the main body 11 kept at a distance. This leads to a simplified process management in the production of the capping 15 , but usually requires a very thin plate as capping 15 ,

Furthermore, it is advantageous in many cases if the conductor structure 17 in the sealing area 16 or the sealing area 16 and an environment of the sealing area 16 is thinner than outside this area, ie in the wider interior 21 or further outdoor space 22 , In this way, the topography to be sealed is in the sealing area 16 lower, which leads to higher reliability and process reliability.

The ladder structure 17 is preferably designed as a planar conductor structure with metallic interconnects having a height of less than 100 .mu.m, in particular less than 10 .mu.m, while the sealing region 16 one the height of the ladder structure 17 exceeding height of preferably less than 1 mm, for example, 400 microns has.

The capping 15 To achieve as high as possible high-frequency properties preferably a high-resistance material, at least in the area in which the capping 15 with the glass 19 is in contact, one the glass 19 has non-reducing surface. This will prevent it from being in the contact area to a reaction of the material of the capping 15 For example, comes with the PbO ₂ contained in the glass under lead elimination.

Particularly suitable material for the capping is high-resistance silicon, which is oxidized superficially to SiO ₂ . Incidentally, the material has the capping 15 possibly one to the main body 11 same or similar thermal expansion coefficient.

The illustrated exemplary embodiment is particularly suitable for microstructure components 5 in which, at least at times, high-frequency electromagnetic waves in the frequency range above 1 gigahertz, for example 24 gigahertz or 77 gigahertz, on the conductor structure 17 be guided. However, it is clear that DC bushings can be realized with the described technique.

It could be demonstrated by comparative experiments that the application of the glass 19 in the sealing area 16 on the ladder structure designed as a coplanar line 17 in the frequency range mentioned not to a significant impairment of the electrical properties of the conductor structure 17 leads.

In particular, it has been shown that for high-frequency electromagnetic fields in the range 1 GHz to 80 GHz, the transmission of a coplanar line with gold tracks compared to a coplanar line, which is covered according to the embodiment of the invention with a 400 micron thick layer of seal glass, and for example, in 430 ° C, is not affected.

For producing the microstructure component or microstructured high-frequency component 5 according to 2 First, the capping is preferred 15 For example, structured out of a silicon wafer, below the glass frit in some areas on the front sides of the side walls of the capping 15 Screen printed as a paste, then a conventional thermal preconditioning of the glass frit on the capping 15 and then the basic body 11 , which is preferably also a silicon wafer, with the component applied thereto 12 and the already generated conductor structure 17 opposite the capping 15 adjusted. Subsequently, a defined gas atmosphere, in particular a protective gas atmosphere or an inert gas atmosphere, or alternatively a negative pressure is generated, and the molten glass frit in the sealing area 16 in which is the capping 15 and the main body 11 Touch, under mechanical pressure and / or elevated temperature with the body 11 connected.

The 6 explains one in too 5 alternative embodiment, again the capping according to 4 not shown .. are different from 5 in an environment of the sealing area 16 with the glass 19 the two air gaps 24 in plan view in each case in particular symmetrically to a widened air gap 23 widened. This will be according to 6 by appropriately structured in this area or provided with a plan view in each case, for example, rectangular recess grounding lines 17 ' . 17 ''' reached. Next shows 6 also, that the area with the widened air gaps 23 has a larger width b ₂ , as the sealing area 16 whose width is designated b ₁ .

The enlarged air gap 23 allows, if necessary, a simple adaptation of the impedance in the area of the sealing area 16 , On the opposite to the width b ₁ enlarged width b ₂ , which serves as a compensation path, an increased offset tolerance is achieved at the same time, which improves the high-frequency characteristics and simplifies installation.

Claims (12)

Microstructure component, with a basic body ( 11 ), wherein on the base body ( 11 ) a planar conductor structure ( 17 . 17 ' . 17 '' . 17 ''' ), and a sealing area ( 16 ), in which the conductor structure ( 17 . 17 ' . 17 '' . 17 ''' ) of the basic body ( 11 ) and a glass ( 19 ), wherein the sealing area ( 16 ) in the longitudinal direction of the conductor structure ( 17 . 17 ' . 17 '' . 17 ''' ) has a width b1, and wherein a capping ( 15 ), which is a microelectronic or microelectromechanical component ( 12 ) or a sensor element together with the basic body ( 11 ) protects against external influences or seals off gas-tight and / or moisture-proof, the capping ( 15 ) with the basic body ( 11 ) over the glass forming the seal ( 19 ) and the conductor structure ( 17 . 17 ' . 17 '' . 17 ''' ) of which in an interior ( 21 ) of the capping ( 15 ) microelectronic or microelectromagnetic component ( 12 ) or sensor element on the base body ( 11 ) through the sealing area ( 16 ) in an outdoor area ( 22 ) of the capping ( 15 ), characterized in that the conductor structure ( 17 . 17 ' . 17 '' . 17 ''' ) in the form of a coplanar line for high-frequency electromagnetic waves with two ground lines ( 17 ' . 17 ''' ), which is a signal line ( 17 '' ) is formed, and between the signal line ( 17 '' ) and one each ground line ( 17 ' . 17 ''' ) one of the glass ( 19 ) filled air gap ( 24 ) is present, wherein in an environment of the sealing area ( 16 ) the air gap ( 24 ) each to a common air gap ( 23 ) is widened, wherein the area with the respectively prevailing air gap ( 23 ) in the longitudinal direction of the conductor structure ( 17 . 17 ' . 17 '' . 17 ''' ) has a greater width b 2 than the width b 1 of the sealing region ( 16 ). Microstructure component according to claim 1, characterized in that the air gaps filled by the glass ( 24 ) in plan view in each case symmetrically to a widened air gap ( 23 ) are formed widened. Microstructure components according to claim 1 or 2, characterized in that the conductor structure ( 17 . 17 ' . 17 '' . 17 ''' ) is provided with a rectangular recess. Microstructure component according to one of the preceding claims, characterized in that the conductor structure ( 17 . 17 ' . 17 '' . 17 ''' ) is formed as a planar conductor structure with a height of less than 100 microns, in particular less than 10 microns, and that the sealing area ( 16 ) one the height of the ladder structure ( 17 . 17 ' . 17 '' . 17 ''' ) exceeding the height of in particular less than 1 mm. Microstructure component according to one of the preceding claims, characterized in that the conductor structure ( 17 . 17 ' . 17 '' . 17 ''' ) in terms of their height in the sealing area ( 16 ) or in the sealing area ( 16 ) and a lateral environment of the sealing area ( 16 ) is formed thinner than outside the sealing area ( 16 ) or the lateral environment of the sealing area ( 16 ). Microstructure component according to one of the preceding claims, characterized in that the glass ( 19 ) is a glass frit melted under the influence of an external pressure. Microstructure component according to one of the preceding claims, characterized characterized in that the basic body ( 11 ) consists at least largely of silicon. Microstructure component according to one of the preceding claims, characterized in that the basic body ( 11 ) in some areas superficially in the main body ( 11 ) integrated or applied microelectronic or microelectromechanical component ( 12 ), which is designed as a micromechanically manufactured high-frequency switch, as a high-frequency diode, as a high-frequency transistor, or as a manufactured in particular in silicon surface micromechanical sensor element having, with the conductor structure ( 17 . 17 ' . 17 '' . 17 ''' ). Microstructure component according to one of the preceding claims, characterized in that the interior ( 21 ) of the capping ( 15 ) an encapsulated cavern ( 18 ), in the region of which the microelectronic or microelectromechanical component ( 12 ) or sensor element is arranged. Microstructure component according to one of the preceding claims, characterized in that a substrate ( 10 ), in particular a printed circuit board, is provided, on which the main body ( 11 ), wherein the conductor structure ( 17 . 17 ' . 17 '' . 17 ''' ) with or on the substrate ( 10 ) running connection lines ( 13 . 14 ) is contactable or connected. Microstructure component according to claim 10, characterized in that the substrate ( 10 ) In some areas a recess ( 20 ) that the capping ( 15 ) between the main body ( 11 ) and the substrate ( 10 ) and that the capping ( 15 ) and at least partially into the recess ( 20 ) intervenes. Microstructure component according to claim 11, characterized in that the recess ( 20 ) in its dimensioning greater than the capping ( 15 ).

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