MEMS device with a single-cavity MEMS element and an ASIC device

Abstract

MEMS device comprising a MEMS element with one cavity, wherein the cavity is at least partially bounded by an ASIC device, wherein the ASIC device has several conductor layers stacked on top of each other along a y-direction between a top layer and a bottom layer, wherein the conductor layers are connected to circuit elements of the ASIC device and / or a sensor element and / or an actuator element of the MEMS element, wherein the ASIC device is adjacent to the cavity with its top layer, wherein the conductor layers have at least a first conductor layer and at least a second conductor layer, wherein the first conductor layer is arranged between the second conductor layer and the top layer, wherein the first conductor layer has at least one conductor, wherein the conductor has a layer stack with an aluminum layer and a titanium layer arranged one above the other in the y-direction, wherein the titanium layer is arranged between the second conductor layer and the aluminum layer, and wherein the titanium layer has a thickness greater than 40 nm in the y-direction, wherein the second conductor layer has a second conductor with copper, and wherein the titanium layer is intended as a getter layer for binding hydrogen, the hydrogen being supplied by the copper of the second conductor track, in particular, outgassing can occur from a copper-based body layer stack, with the titanium layer reducing or preventing the penetration of outgassing hydrogen into the cavity.

Description

[0001] The invention relates to a MEMS device comprising a MEMS element with a cavity, wherein the cavity is at least partially bounded by an ASIC device.

[0002] From DE 10 2004 020 685 B3 a MEMS device with a cavity is known, wherein a getter layer is provided in the cavity to absorb certain gas molecules. State of the art Disclosure of the invention

[0003] The invention consists in designing a MEMS device with a cavity, wherein an ASIC device at least partially limits the cavity, in such a way that a pressure change in the cavity due to gases diffusing out in the ASIC device is reduced, in particular avoided.

[0004] The object of the invention is solved by the features of claim 1.

[0005] Advantageous embodiments of the invention are specified in the dependent claims.

[0006] One advantage of the proposed MEMS device is that outgassing of hydrogen from the ASIC device into the cavity of the MEMS element is reduced, and in particular avoided.

[0007] This is achieved by the ASIC device having a conductor track with a titanium layer, the titanium layer being positioned between the cavity and another conductor track. The titanium layer has a thickness preferably greater than 40 nm. The second conductor track system (i.e., conductor track and insulation) has copper, or the second conductor track has copper, or is designed as a copper conductor track, from which hydrogen can outgas. Furthermore, the ASIC device can have a copper conductor stack with multiple copper conductor tracks from which hydrogen can outgas. The hydrogen that outgasses from the copper conductor track(s) and diffuses towards the cavity is at least partially, and in particular completely, bound by the titanium layer. Thus, the titanium layer acts as a getter layer for binding the hydrogen.Depending on the chosen embodiment, the titanium layer can also have greater thicknesses in order to sufficiently bind the hydrogen of the second conductor track.

[0008] The titanium in the titanium layer has the property of forming hydrides, whereby hydrogen is incorporated into the titanium layer, releasing energy. The thickness and / or width of the titanium layer can be adjusted depending on the expected amount of hydrogen. Preferably, there is enough titanium to bind all the hydrogen outgassing from the at least one second conductor track or the copper conductor stack.

[0009] The ASIC component is adjacent to the cavity of the MEMS element via a cover layer. Sensor elements and / or actuator elements can be arranged adjacent to or within the cavity, or connected to the cavity via a conduit.

[0010] The ASIC device has several layers of conductive traces arranged one above the other between the top layer and a bottom layer. The conductive traces of the conductive layers can be connected to circuit elements of the ASIC device and / or to sensor elements and / or actuator elements of the MEMS element. The ASIC device has a first conductive layer located between the top layer and the second conductive layer. The first conductive layer has at least one conductive trace, which is a stack of layers consisting of at least one aluminum layer and one titanium layer. The titanium layer is located between the aluminum layer and the second conductive layer and thus faces the second conductive layer. The second conductive layer has a second conductive trace made of copper or is designed as a copper layer.Thus, the titanium layer acts as a getter layer to bind hydrogen that can outgas from the copper conductor stack of the second conductor and diffuse towards the cavity. In this way, the penetration of outgassing hydrogen into the cavity is reduced or prevented.

[0011] In one embodiment, the titanium layer has a base surface in a first xz-plane, and the second conductor has a base surface in a second xz-plane. The base surface of the titanium layer is arranged above the second conductor in a perpendicular projection along the y-direction over at least 50% of its length and, in particular, covers the entire width of the second conductor. Thus, the titanium layer of the first conductor preferably covers the entire width of the second conductor over at least 50% of its length in a perpendicular projection along the y-direction. In this way, the titanium layer of the first conductor achieves coverage of the second conductor, giving the titanium layer a relatively high efficiency as a getter layer.

[0012] Depending on the chosen embodiment, the titanium layer covers more than 50% of the length of the second conductor track in the vertical projection, in particular 70% or more, and in particular 90% or more. Preferably, the titanium layer covers the entire width of the second conductor track, and in particular at least 5%, and in particular 10%, of the width of the second conductor track on each side. The more the titanium layer covers the width of the second conductor track in the vertical projection, the better the titanium layer's effectiveness as a getter layer.

[0013] In a further embodiment, the second conductor layer has, in addition to the second conductor layer, a further second conductor layer, which also comprises copper or is designed as a copper layer. The second and the further second conductor layers are arranged laterally at a distance from each other via an intermediate section. The base surface of the titanium layer is designed in a perpendicular projection along the y-direction such that the base surface of the titanium layer covers the base surface of the second conductor layer, the intermediate section between the second conductor layer and the further second conductor layer, and the base surface of the further second conductor layer. In this way, not only the second conductor layer and the further second conductor layer, but also the intermediate section between the two second conductor layers are covered by the titanium layer to prevent hydrogen outgassing towards the cavity.In this way, an improved effect of the titanium layer as a getter layer is achieved.

[0014] In a further embodiment, a barrier layer is provided between the cavity and the first conductor layer. The barrier layer is designed to reduce, and in particular prevent, the outgassing of argon from the first conductor layer into the cavity. For example, the barrier layer comprises a silicon nitride layer, wherein the silicon nitride layer has a thickness of at least 40 nm and is, for example, formed as a sputtered layer. The barrier layer reduces, and in particular prevents, the outgassing of argon into the cavity.

[0015] In another embodiment, the MEMS device features a via contact that connects to the titanium layer of the first conductor. In the region of the via contact, the titanium layer has a reduced thickness in the y-direction compared to a lateral region adjacent to the xz-plane. This reduces the electrical resistance between the via contact and the aluminum layer. The reduced thickness is achieved, in particular, by a recess in the titanium layer through which the via contact is guided. Thus, despite the relatively thick titanium layer, the ohmic resistance of the electrically conductive connection between the via contact and the aluminum layer can be reduced. The aluminum layer is designed to carry a significant portion of the current of the first conductor.

[0016] In one embodiment, the via contact conductor contains tungsten and is specifically made of tungsten. Tungsten is suitable for a reliable and low-resistance design of the via contact conductor.

[0017] Depending on the chosen embodiment, the titanium layer in the y-direction can have a thickness greater than 100 nm, in particular greater than 150 nm or greater than 180 nm. The greater the thickness of the titanium layer, the more titanium is available for the getter function to bind hydrogen.

[0018] In a further embodiment, a further titanium layer is arranged between the aluminum layer of the first conductor layer and the cover layer, wherein the further titanium layer has a thickness of less than 20 nm, in particular less than 15 nm. The further titanium layer serves more to ensure the reliable structure of the first conductor layer and less as a getter layer.

[0019] In a further embodiment, the ASIC component has a further first conductor layer between the first conductor layer and the second conductor layer, wherein the further first conductor layer comprises at least one further first conductor, and the further first conductor comprises a layer stack with an aluminum layer and a titanium layer. The aluminum layer is arranged on the titanium layer of the further first conductor and between the titanium layer of the further first conductor and the first conductor layer. The titanium layer of the further first conductor has a thickness greater than 40 nm and serves as a getter layer for binding hydrogen that can outgas from at least one or more second conductors with copper, in particular from a layer stack with several second conductor layers. This also reduces or prevents the penetration of outgassing hydrogen into the cavity.

[0020] Another advantage of the proposed MEMS device is that it can withstand sequential temperature stress processes, such as those occurring during standard soldering, overmolding, or high-temperature storage, without significant impairment of its electrical properties. This allows for the reliable long-term maintenance of internal cavity pressure.

[0021] The MEMS device comprises a MEMS (micro electromechanical system) element with micromechanical structures and a cavity, and an ASIC (application-specific integrated circuit) device with circuit components that interact with the micromechanical structure of the MEMS element. The MEMS element is mounted on the ASIC device, such that the micromechanical structure of the MEMS element is located in the cavity between the MEMS element and the ASIC device.

[0022] The following section explains exemplary embodiments of the MEMS device in more detail with reference to the figures. They show Fig. 1 a schematic cross-section through a MEMS device with a single-cavity MEMS element and an ASIC device, Fig. 2 a schematic top view of the ASIC component, Fig. 3 in a schematic cross-section a more detailed view of the ASIC component, Fig. 4 in a schematic representation a top view of the first conductor track of the ASIC component, Fig. 5 a schematic cross-section through another embodiment of the ASIC device, Fig. 6 a schematic partial cross-section through a via contact line of an ASIC component, and Fig. 7 a schematic cross-sectional representation of another embodiment of the ASIC component.

[0023] Fig. Figure 1 shows a schematic cross-section through a MEMS device 1, which comprises a MEMS element 2 and an ASIC device 3. A cavity 4 is formed between the MEMS element 2 and the ASIC device 3. The cavity 4 is bounded by the MEMS element 2 and at least partially by the ASIC device 3. Sensor and / or actuator elements 5 of the MEMS element 2 can be arranged adjacent to or within the cavity 4, or at least connected to the cavity 4 via a channel. The ASIC device 3 has a cover layer 6 that is at least partially directly adjacent to the cavity 4.

[0024] Fig. Figure 2 shows a schematic view of the ASIC component 3, with the cavity 4 schematically indicated by dashed lines. In the illustrated embodiment, the cavity 4 is bounded on five sides by the MEMS component 2 and on one side by the ASIC component 3.

[0025] Fig. Figure 3 shows a schematic cross-section of a partial cross-section of the ASIC device 3, where the ASIC device 3 has a first conductor layer 8 adjacent to the top layer 6. A second conductor layer 9 adjoins the first conductor layer 8 along the y-direction. A bottom layer 7 adjoins the second conductor layer 9. Electrical and / or electronic circuits of the ASIC device can be integrated in the bottom layer 7.

[0026] The first conductor layer 8 has a first insulating layer 10 in which a first conductor 11 is embedded. Adjacent to the second conductor layer 9, the first conductor 11 has a first layer 12, which comprises or is made of titanium. Depending on the chosen embodiment, the first layer 12 may also consist of or comprise a stack of layers consisting of the sequence titanium nitride, titanium, titanium nitride. A first conductor layer 13, which comprises or is made of aluminum, is arranged on the first layer 12. A first cover layer 14, which comprises titanium and is in particular formed from a stack of layers consisting of the sequence titanium nitride, titanium, titanium nitride, may be arranged on the first conductor layer 13.

[0027] The titanium layer of the first layer 12 can have a thickness between 40 nm and 200 nm or more. The titanium layer of the first layer 12 forms a getter layer for diffusing hydrogen. The titanium nitride layers of the first layer can have a thickness of less than 10 nm and, for example, function as an adhesion promoter or a separating layer to suppress a material mixture.

[0028] The second conductor layer 9 has a second insulating layer 15 in which a second conductor 16 is embedded. The second conductor 16 has copper or is made of copper. The second conductor 16 and the second insulating layer 15 are arranged above the base layer 7.

[0029] The first layer 12 has a width along the x-direction that is wider than the width of the second conductor track 16. Furthermore, the first layer 12 is positioned between the cavity 4 and the second conductor track 16 such that, in a projection along the y-direction, the first layer 12 covers the entire width of the second conductor track 16. Preferably, the titanium layer of the first layer 12 extends laterally beyond the second conductor track 16 on both sides along the x-direction. This ensures good getter action against hydrogen diffusion into the cavity 4.

[0030] Furthermore, the ASIC component 3 can be configured such that several first conductors 11 are arranged side by side in the first conductor layer 8. Additionally, the ASIC component 3 can be configured such that several second conductors 16 are arranged side by side in the second conductor layer 9. The structure of the first conductors 11 can be identical or vary. Similarly, the second conductors 16 can also be identical or vary in structure.

[0031] The top layer 6 can be a barrier layer or have a barrier layer that reduces, and in particular prevents, the outgassing of carrier gas, e.g., argon, from the first conductor layer into the cavity. For example, the top layer 6 can have a silicon nitride layer as a barrier layer. The silicon nitride layer can, in particular, have a thickness of, for example, 50 nm to 100 nm along the y-direction. The barrier layer, in particular the silicon nitride layer, can be formed as a sputtered layer.

[0032] Fig. Figure 4 shows a schematic top view of the titanium layer of the first layer 12, with the underlying second conductor 16 represented by dashed lines. The first conductor 11, or the first layer 12, extends longitudinally along the z-direction, and the second conductor 16 also extends longitudinally along the z-direction.

[0033] The titanium layer of the first layer 12 projects laterally, i.e., along the x-direction, at least a predetermined distance x1, x2 beyond the second conductor track 16. The predetermined distances x1, x2 can represent 1 to 5% or more of the width of the second conductor track 16 in the x-direction. The more the first conductor track 11 projects laterally beyond the second conductor track 16 on both sides along the x-direction, the better the shielding effect against the diffusion of hydrogen into the cavity.

[0034] Fig. Figure 5 shows a schematic cross-section through another embodiment of the ASIC component 3. In this embodiment, the second conductor layer 9 has a further second conductor 17, which is spaced laterally in the x-direction from the second conductor 16 by an intermediate area 18. The further second conductor 17 also has copper or is formed from copper. In this embodiment, the first conductor 11 is connected to the titanium layer of the first layer 12, the first conduction layer 13, and the first cover layer 14 analogously to the embodiment of Fig. The titanium layer 3, however, in a projection in the y-direction, covers the second conductor track 16, the intermediate area 18 between the second conductor track 16 and the further second conductor track 17, and the further second conductor track 17 itself. Furthermore, the first layer 12 of the first conductor track 11 projects laterally beyond the second conductor track 16 and the further second conductor track 17 along the x-direction. In this way, not only the second conductor track 16 and the further second conductor track 17, but also the intermediate area 18 between the second conductor track 16 and the further second conductor track 17 are covered by the titanium layer of the first layer 12 of the first conductor track 11 in the direction of the cavity. This provides improved protection against hydrogen diffusion into the cavity 4.

[0035] Fig. Figure 6 shows a schematic partial sectional view of a section of the ASIC device 3, in which an electrically conductive via 20 extends from the base layer 7 through the second insulating layer 15 of the second conductor layer 9 for electrical contact with the first conductor layer 13. To reduce the electrical resistance of the first layer 12, which has titanium, the first layer 12 has a recess 19 filled with the conductor material 11. Thus, the residual thickness 21 of the first layer 12, which is formed between the end of the via 20 and the first conductor layer 13, is significantly reduced and is, for example, in the range of 5% to 30% of the thickness of the titanium layer of the first layer 12.

[0036] Depending on the chosen embodiment, the via contact line can contain 20 tungsten or be made of tungsten.

[0037] Fig. Figure 7 shows another embodiment of an ASIC device 3 in a cross-section and a schematic representation. In this embodiment, the cover layer 6 has a cover insulation layer 25 and a barrier layer 26. The first conductor layer 8 has a bottom insulation layer 27 on which the first conductors 11 and the first insulation layer 10 are arranged.

[0038] Furthermore, adjacent to the first conductor layer 8, another first conductor layer 22 is arranged, which also has a first insulating layer 10, a bottom insulating layer 27, and further first conductors 30. The conductors 11 of the first conductor layer 8 and the further first conductors 30 of the further first conductor layer 22 can have the same layer structure, in particular a first layer 12 with titanium and a first conduction layer 13 with aluminum, as shown by Fig. 3 was described.

[0039] The second conductor layer 22 is arranged on the second conductor layer 9. In the illustrated embodiment, the second conductor layer 9 has a second bottom insulation layer 28, a second insulation layer 15, and several second conductors 16. In the illustrated embodiment, further second conductor layers 23, 24, 25 are arranged, which are configured analogously to the second conductor layer 9. The second conductor layer 9 and the further second conductor layers 23, 24, 25 can have the same structure, in particular, they can have second conductors 16 with copper.

[0040] The second conductor layers 9, 23, 24, and 25 offer the advantage of achieving a high wiring density with low parasitic wiring capacitances. This high wiring density with narrow conductor tracks significantly increases the utilization of the digital gates, thus enabling high area efficiency.

[0041] The first conductor layers 8, 22 have the advantage that, with the help of the relatively thick titanium layers, i.e., the first layers 12, a relatively good getter layer is provided to bind hydrogen outgassing from the underlying copper conductors. Despite the incorporation of hydrogen into the titanium, the electrical properties of titanium hardly change. Preferably, the layer thickness of the first layer 12 is adapted to the expected amount of hydrogen gas. The titanium layer is applied as a layer in the proposed MEMS device, so that no extra masks or additional process steps are required.

[0042] Preferably, the first layers 12 of the first conductor layer 8 cover as much as possible of the areas of the second conductor layers 16 of the second conductor layers 9 when viewed in the projection along the y-direction.

[0043] The via contact conductor used, which contains tungsten, prevents copper from leaking into the aluminum material of the first conductor layer 13.

[0044] Furthermore, cratering during wafer bonding can be reduced or eliminated using a solid tungsten frame.

[0045] The proposed MEMS device enables optimization of the layer structure, reducing hydrogen outgassing while still allowing for a high wiring density in the ASIC device.

[0046] The aluminium layer of the first conduction layer 13 can have a thickness in the range of 250 to 350 nm or even up to 1 µm and more.

[0047] The insulating layers can be, for example, oxide layers, in particular silicon oxide layers or silicon nitride layers.

[0048] The second conductor tracks 16, which contain or are formed from copper, can have a width of less than 100 nm or more. The first layers 12 and the first conduction layers 13 can have a width of 150 nm or more. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2004 020 685 B3

[0002]

Claims

[1] MEMS device (1) comprising a MEMS element (2) with a cavity (4), wherein the cavity (4) is at least partially bounded by an ASIC device (3), wherein the ASIC device (3) has several conductor layers (8, 9) arranged one above the other along a y-direction between a top layer (6) and a bottom layer (7), wherein the conductor layers (8, 9) are connected to circuit elements of the ASIC device and / or a sensor element and / or an actuator element of the MEMS element, wherein the ASIC device (3) adjoins the cavity (4) with its top layer (6), wherein the conductor layers (8, 9) comprise at least a first conductor layer (8) and at least a second conductor layer (9), wherein the first conductor layer (8) is arranged between the second conductor layer (9) and the top layer (6), wherein the first conductor layer (8) comprises at least a first conductor (11) exhibitswherein the first conductor (11) comprises a layer stack with an aluminum layer and a titanium layer (12) arranged one above the other in the y-direction, wherein the titanium layer (12) is arranged between the second conductor layer (9) and the aluminum layer (13), and wherein the titanium layer (12) has a thickness greater than 40 nm in the y-direction, wherein the second conductor layer (9) comprises a second conductor (16) with copper, and wherein the titanium layer (12) is provided as a getter layer for binding hydrogen, wherein the hydrogen can outgas from the copper layer, and wherein the titanium layer (12) reduces or prevents the penetration of outgassing hydrogen into the cavity (4). [2] MEMS device according to claim 1, wherein the titanium layer (12) of the first conductor (11) has a base area in a first xz-plane, wherein the second conductor (16) has a base area in a second xz-plane, wherein the base area of ​​the titanium layer (12) in a perpendicular projection along the y-direction covers the base area of ​​the second conductor (16) over at least 50% of a length of the second conductor (16) and over the entire width of the second conductor (16). [3] MEMS device according to one of the preceding claims, wherein the second conductor layer (9) has a further second conductor layer (17) in addition to the second conductor layer (16), wherein the second conductor layer (17) has copper, wherein the second and the further second conductor layer (16, 17) are arranged laterally at a distance via an intermediate area (18), wherein the base surface of the titanium layer (12) extends in a perpendicular projection along the y-direction over the base surface of the second conductor layer (16), over the intermediate area (18) and the base surface of the further second conductor layer (17), so that the intermediate area (18) between the two second conductor layers (16, 17) is also covered against outgassing of hydrogen in the direction of the cavity (4). [4] MEMS device according to one of the preceding claims, wherein a barrier layer (26) is provided between the cavity (4) and the first conductor layer (8) which reduces, in particular prevents, outgassing of argon from the first conductor layer into the cavity. [5] MEMS device according to claim 4, wherein the barrier layer (26) comprises a silicon nitride layer, wherein the silicon nitride layer can in particular have a thickness of at least 40nm and is formed as a sputtered layer. [6] MEMS device according to one of the preceding claims, wherein a via contact line (20) is led to the titanium layer (12), wherein the titanium layer (12) has a reduced thickness (21) in the y-direction in the region of the via contact line compared to a laterally adjacent region in the xz-plane in order to produce a reduced electrical resistance between the via contact line (20) and the aluminum layer (13), wherein in particular the reduced thickness is realized by a recess (19) in the titanium layer (12), wherein the via contact line (20) is arranged in the recess (19) of the titanium layer (12). [7] MEMS device according to claim 6, wherein the via contact line (20) comprises tungsten. [8] MEMS device according to one of the preceding claims, wherein the titanium layer (12) has a thickness greater than 100 nm, in particular greater than 150 nm or greater than 180 nm. [9] MEMS device according to one of the preceding claims, wherein a further titanium layer (14) is arranged between the aluminium layer (13) of the first conductor layer (8) and the cover layer (6), wherein the further titanium layer (14) has a thickness of less than 20 nm, in particular less than 15 nm. [10] MEMS device according to one of the preceding claims, wherein a further first conductor layer (22) is arranged between the first conductor layer (8) and the second conductor layer (9), wherein the further first conductor layer (22) has at least one further first conductor (30), wherein the first conductor (11) has a layer stack (13) with aluminum layer and titanium layer (12) arranged one above the other along the y-direction, wherein the titanium layer (12) is arranged between the second conductor layer (9) and the aluminum layer (13) of the further first conductor layer (22), and wherein the titanium layer has a thickness greater than 40 nm, and wherein the titanium layer is provided as a getter layer for binding hydrogen outgassing from the copper layer of the second conductor layer (9) in order to reduce or prevent penetration of the outgassing hydrogen into the cavity (4).

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