DE102014211190A1 - Micromechanical sound transducer arrangement and a corresponding manufacturing method - Google Patents

Abstract

The present invention provides a micromechanical sound transducer assembly and a corresponding manufacturing method. The micromechanical sound transducer arrangement comprises an ASIC chip (AC) having a first front side (VS1) and a first rear side (RS1), an interposer chip (1a, 1a '', 1a '' ') having a second front side (VS2, VS2' '). ) and a second rear side (RS2; RS2 '') which has a cavity (BV; BV ''; BV '' ') accessible at least from the second front side (VS2; VS2' ') and a MEMS chip (MC ) having a third front side (VS3) and a third rear side (RS3), which has an integrated sound conversion device (BE, FE) for converting sound energy (S) into electrical energy or vice versa. The first face (VS1) is on the second back (RS2; RS2 '') and the second face (VS2; VS2 '') is on the third face (RS3). The sound energy (S) can thus be supplied from the third rear side (RS3) starting from the integrated sound conversion device (BE, FE) and the cavity (BV; BV ", BV" ') as part of a return volume.

Description

The present invention relates to a micromechanical sound transducer arrangement and a corresponding manufacturing method.

State of the art

Although applicable in principle to any micromechanical sound transducer arrangements, for example loudspeakers and microphones, the present invention and the problem on which it is based are explained on the basis of micromechanical microphone arrangements based on silicon.

Micromechanical microphone arrangements usually have a sound conversion device integrated on a MEMS chip for converting sound energy into electrical energy, wherein a sound energy deflectable first electrode and a fixed perforated second electrode cooperate capacitively. The deflection of the first electrode is determined by the difference in the sound pressures before and after the first electrode. If the deflection changes, the capacitance of the capacitor formed by the first and second electrodes is changed, which can be detected metrologically.

On the back of the first electrode, a so-called back volume is provided, which prevents rapid changes in the sound pressure applied to both sides of the first electrode, which would lead to sensitivity losses. The size of the back volume thus determines the sensitivity of the micromechanical microphone arrangement, since a compression caused by the deflection of the first electrode in the back volume, in particular in the case of small back volumes, has a damping effect.

Micromechanical microphone arrangements, such as those used in mobile devices such as smartphones, are basically available in two design variants, such as from the US 2013/0147040 A1 known.

In the "bottom port" variant, the acoustic access from below is realized via a printed circuit board. In this case, the MEMS chip is glued to the sound conversion device on the circuit board and sealed with a lid to form the back volume.

In the "top port" variant, the access is from above, wherein the MEMS chip is glued with the sound conversion device in a lid, so that the acoustic access is through a hole in the lid.

For newer applications, e.g. for headsets or electronic goggles, the size plays an increasingly decisive role. It is important to achieve the largest possible back volume with a minimum footprint and height, as this contributes significantly to the overall performance.

Due to manufacturing tolerances in known solutions for the housing further miniaturization is currently not possible while maintaining the overall performance. In addition, the maximum possible back volume and the maximum size of the access hole are also not achieved due to the tolerances.

From the DE 10 2006 022 379 A1 It is known to bond an ASIC chip with a back cavity to a MEMS chip with a sound conversion device in such a way that the back volume is increased by the cavern, since it is distributed over both chips.

Disclosure of the invention

The present invention provides a micromechanical sound transducer arrangement according to claim 1 and a corresponding manufacturing method according to claim 11.

Preferred developments are subject of the dependent claims.

Advantages of the invention

The present invention enables a "bare-die" approach for a micromechanical transducer assembly (ie, the transducer assembly need not be packaged in another package) for realizing very small transducers, particularly microphones and loudspeakers, the minimum size being limited only by the larger one is limited by MEMS and ASIC chip. In addition, the present invention allows better utilization of the existing volume for the back volume. Furthermore, the micromechanical sound transducer arrangement according to the invention has a reduced parasitic capacitance and is insensitive to particles, in particular if an optional protective film is used or if the deflectable first electrode is arranged facing outward.

The idea underlying the present invention is to connect a MEMS chip and an ASIC chip via a wafer stack with one or more interposer chips, whereby one can achieve smaller tolerances than in known standard methods. In addition, fewer parts must be placed, so that the necessary provisions are significantly reduced.

By selecting the material of the or the interposer chips can also be an increased electrical resistance, ie a better electrical isolation, achieve between the individual electrical connections between the MEMS chip and basic chip, which improves the signal / noise ratio. The one or more interposer chips also allow greater flexibility in the height and thus in the rear volume.

According to a preferred embodiment, the cavity passes through the interposer chip. This is how you can achieve a big return volume.

According to a further preferred development, at least one further interposer chip is provided with a further front side and a further rear side, which has a further hollow space, which passes through the further interposer chip, wherein the further interposer chip is mounted between the second front side and the third front side. This allows the back volume to be further increased.

According to a further preferred development, the interposer chip is laterally widened in comparison to the MEMS chip. This also increases the achievable back volume, since a lateral width gain can be achieved.

According to a further preferred development, the cavity in the interior of the interposer chip has a lateral broadening. This allows for an interposer chip with large surface area and, at the same time, optimal volume utilization for the back volume.

According to a further preferred development, the interposer chip has one or more plated-through holes which electrically connect the MEMS chips to the ASIC chip. This simplifies the structure.

According to a further preferred development, the further interposer chip has further plated-through holes, which are electrically connected to the plated-through holes and which electrically connect the MEMS chip to the ASIC chip. This allows for easy stacking.

According to a further preferred development, the interposer chip or the further interposer chip consists of glass. Glass has the advantage of high electrical resistance to avoid leakage and parasitic capacitances.

According to a further preferred development, the sound conversion device has a first electrode deflectable by the sound energy and a fixed perforated second electrode. This allows a simple sound conversion.

According to a further preferred development, a protective film is applied to the third rear side. This ensures protection against environmental influences.

Brief description of the drawings

The present invention will be explained in more detail with reference to the exemplary embodiments indicated in the schematic figures of the drawings. Show it:

1 a micromechanical transducer assembly according to a first embodiment of the present invention;

2 a micromechanical transducer assembly according to a second embodiment of the present invention;

3 a micromechanical transducer assembly according to a third embodiment of the present invention; and

4 a micromechanical transducer assembly according to a fourth embodiment of the present invention.

Embodiments of the invention

In the figures, like reference numerals designate the same or functionally identical elements.

1 shows a schematic vertical cross-sectional view of a micromechanical transducer assembly according to a first embodiment of the present invention.

In 1 Numeral AC designates an ASIC chip having a first front side VS1 and a first back side RS1. reference numeral 1 denotes an ASIC wafer substrate, for example of silicon, in which a plurality of integrated circuits 50 is integrated, which are used for signal processing and signal evaluation.

At the first front side VS1 is on the ASIC wafer substrate 1 a rewiring device L is formed, which has a plurality of conductor tracks and intervening insulating layers with corresponding plated-through holes. Provided as the uppermost layer is a front-side insulation layer IV. On the first back side RS1, a back-side insulation layer IR is provided.

Through-contacts D1, D2 connect the rewiring device L with connection pads P1, P2, on which solder balls L1, L2 are provided, electrically. About the solder balls L1, L2, the transducer assembly can be soldered to any (not shown) carrier substrate.

Vias V1, V2 filled with conductive material on the first front side VS1 penetrate the front-side insulation layer IV in order to form an electrical connection between the rewiring device L and bonding connections B1, B2 formed on the first front side.

About the bonds B1, B2 is on the ASIC chip AC an interposer chip 1a attached by bonding, which has a second front side VS2 and a second rear side RS2. The interposer chip 1a Conveniently consists of a material with high electrical resistance, such as glass. The interposer chip has one through the interposer chip 1a passing cavity BV, which thus extends from the second front side VS2 to the second rear side RS2.

Further provided in the interposer chip 1a are plated-through holes D1a, D2a, which enable an electrical connection between the bonding connections B1, B2 on the second rear side RS2 and opposed bonding connections B3, B4 on the second front side.

A MEMS chip is mounted on the second front side VS2 via the bonding connections B3, B4, which has a third front side VS3 and a third rear side RS3, the third front side VS3 being mounted on the second front side VS2.

The MEMS chip MC has an integrated sound conversion device for converting sound energy S into electrical energy. The integrated sound conversion device comprises a first electrode BE deflectable by the sound energy S and a fixed perforated second electrode FE, which are realized in respective micromechanical functional layers F1, F2, for example of polysilicon, which overlay a MEMS wafer substrate 1b , For example, of silicon, between corresponding insulating layers, which are collectively designated by reference numeral I1 anchored.

A MEMS wafer substrate 1b passing through the trench trench TR creates an access opening for the sound energy S to the first deflectable electrode BE which in the present case has the shape of a closed membrane. By the optional closed membrane-like structure of the first deflectable electrode BE, an effective protection for the interior of the micromechanical sound transducer arrangement can be realized. Additionally glued on the third back RS3 is an optional protective foil 100 , which further increases particle safety.

Due to the structure described, the sound energy S from the third back RS3 is starting from the protective film 100 and the trenches TR through the first deflectable electrode BE and from there further to the cavity BV fed. Thus, the cavity BV provides a substantial portion of the back volume of this micromechanical transducer assembly.

By bonding the chips MC, 1a and AC, which have substantially the same lateral width, the back volume is preferably hermetically or almost hermetically sealed. An additional packaging is therefore not necessary.

In that, compared to out of the DE 10 2006 022 371 A1 known solution of the ASIC chip AC must have no cavern, this can be made more stable and easier and with more flexibility. The fact that the rewiring device L is directed with the first front side VS1 to the baking volume also simplifies the wiring effort.

2 shows a schematic vertical cross-sectional view of a micromechanical transducer assembly according to a second embodiment of the present invention.

In the second embodiment, there are two interposer chips 1a . 1a ' , which are identically constructed, stacked on each other.

In particular, another interposer chip 1a ' provided with a further front side VS2 'another back RS', wherein the further Interposerchip 1a ' another cavity BV ', by the further interposer chip 1a ' passes. The further interposer chip 1a ' is attached between the second front side VS2 and the third front side VS3 by bonding such that the further front side VS2 'are connected to the third front side via the bonding connections B3, B4 and the further back side RS "is connected to the second front side VS2 via the bonding connections B3 ', B4' is connected. Such an arrangement creates an even larger back volume, which is essentially formed by the volume of the two cavities BV, BV '.

A rewiring at the boundary between VS2 and RS2 'is possible in addition to the position of the If necessary, adapt connections B3 and B4 to another position of connections B1 and B2.

In general, an arbitrary enlargement of the back volume is possible by stacking a corresponding number of interposer chips, wherein the number of interposer chips required is essentially influenced by production conditions and the material selection of the interposer chips.

Otherwise, the second embodiment is the same as the first embodiment in terms of the ASIC chip AC and the MEMS chip MC.

3 shows a schematic vertical cross-sectional view of a micromechanical transducer assembly according to a third embodiment of the present invention.

In the third embodiment, a modified interposer chip is compared to the first embodiment 1a ' in front. This modified interposer chip 1a ' , which is also made of glass, is laterally widened with respect to the MEMS chip MC and with respect to the ASIC chip AC, wherein the MEMS chip MC and the ASIC chip AC have substantially the same lateral width, but this is not necessarily so have to be.

Also, the cavity BV "is inside the modified interposer chip 1a ' an annular lateral broadening VB, whereby the cavity BV '' can be made larger in comparison to the first embodiment, wherein at the same time the largest possible second front side VS2 'and the largest possible back RS2' of the modified interposer chip 1a ' can be maintained. However, the feedthroughs D1a ", D2a", which electrically connect the MEMS chip MC to the ASIC chip AC, must be connected to the interposer chip 1a ' be moved to the edge, since at the earlier positions according to the first embodiment, the broadening is present. Due to this fact, the bonding connections B1 to B4 are connected via respective conductor tracks LL1 to LL4 to the plated-through holes D1a "or D2a".

Otherwise, the third embodiment is the same as the first embodiment in terms of the MEMS chip MC and the ASIC chip AC.

4 shows a schematic vertical cross-sectional view of a micromechanical transducer assembly according to a fourth embodiment of the present invention.

In the fourth embodiment, the cavity BV '' ', which forms the essential part of the back volume, accessible only from the second front side VS2 and closed to the second back RS2, is thus formed in the form of a trough.

Otherwise, the fourth embodiment is the same as the first embodiment.

Although the present invention has been fully described above with reference to preferred embodiments, it is not limited thereto but is modifiable in a variety of ways.

In particular, the geometries and materials shown are only examples and can be varied almost arbitrarily depending on the application.

Also, the structure of the sound conversion device in the MEMS chip and the arrangements in the ASIC chip are only exemplary and can also be varied depending on the application.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2013/0147040 A1 [0005]
• DE 102006022379 A1 [0010]
• DE 102006022371 A1 [0043]

Claims (11)

A micromechanical sound transducer assembly comprising: an ASIC chip (AC) having a first front (VS1) and a first back (RS1); an interposer chip ( 1a ; 1a '; 1a ''' ) having a second front side (VS2; VS2 '') and a second rear side (RS2; RS2 '') which has a cavity (BV; BV ''; BV '') accessible at least from the second front side (VS2; VS2 ''). ') having; and a MEMS chip (MC) having a third front side (VS3) and a third rear side (RS3), which has an integrated sound conversion device (BE, FE) for converting sound energy (S) into electrical energy or vice versa; the first front side (VS1) being mounted on the second rear side (RS2; RS2 '') and the second front side (VS2; VS2 '') on the third rear side (RS3); and wherein the sound energy (S) from the third back (RS3) starting from the integrated sound conversion device (BE, FE) and the cavity (BV, BV '', BV ''') is supplied as part of a return volume. Micromechanical sound transducer arrangement according to claim 1, wherein the cavity (BV, BV '') through the interposer chip ( 1a ; 1a ' ) goes through. Micromechanical sound transducer arrangement according to claim 1 or 2, wherein at least one further interposer chip ( 1a ' ) is provided with a further front side (VS2 ') and a further rear side (RS2'), which has a further cavity (BV ') which is penetrated by the further interposer chip ( 1a ' ), and wherein the further interposer chip ( 1a ' ) is mounted between the second front side (VS2; VS2 '') and the third front side (VS3). Micromechanical sound transducer arrangement according to one of the preceding claims, wherein the interposer chip ( 1a ' ) is widened laterally with respect to the MEMS chip (MC). Micromechanical sound transducer arrangement according to one of the preceding claims, wherein the cavity (BV '') inside the interposer chip ( 1a ' ) has a lateral broadening (VB). Micromechanical sound transducer arrangement according to one of the preceding claims, wherein the interposer chip ( 1a ; 1a '; 1a ''' ) has one or more vias (D1a, D2a; D1a '', D2a '') which electrically connect the MEMS chip (MC) to the ASIC chip (AC). Micromechanical sound transducer arrangement according to claim 6 in conjunction with claim 3, wherein the further interposer chip ( 1a ' ) has further vias (D1a ', D2a') which are electrically connected to the vias (D1a, D2a; D1a '', D2a '') and which electrically connect the MEMS chips (MC) to the ASIC chip (AC). connect. Micromechanical sound transducer arrangement according to one of the preceding claims, wherein the interposer chip ( 1a ; 1a '; 1a ''' ) or the further interposer chip ( 1a ' ) consists of glass.  Micromechanical sound transducer arrangement according to one of the preceding claims, wherein the sound conversion device (BE, FE) has a deflectable by the sound energy (S) first electrode (BE) and a fixed perforated second electrode (FE). Micromechanical sound transducer arrangement according to one of the preceding claims, wherein on the third rear side (RS3) a protective film ( 100 ) is applied. A method of fabricating a micromechanical sound transducer assembly comprising the steps of: providing an ASIC chip (AC) having a first front side (VS1) and a first back side (RS1); Providing an interposer chip ( 1a ; 1a '; 1a ''' ) having a second front side (VS2; VS2 '') and a second rear side (RS2; RS2 '') which has a cavity (BV; BV ''; BV '') accessible at least from the second front side (VS2; VS2 ''). ') having; Providing a MEMS chip (MC) having a third front side (VS3) and a third rear side (RS3), which has an integrated sound conversion device (BE, FE) for converting sound energy (S) into electrical energy or vice versa; first attaching the first front (VS1) to the second back (RS2; RS2 '') and second attaching the second front (VS2; VS2 '') to the third back (RS3), after which the sound energy (S) from the third back (RS3) starting from the integrated sound conversion device (BE, FE) and the cavity (BV, BV '', BV ''') can be supplied as part of a return volume.

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