Abstract
In an embodiment, a pressure sensor module includes a base electrode surrounding at least a part of a bottom electrode, an anchor arrangement on top of the base electrode including at least two electrically conductive walls that both surround at least the part of the bottom electrode and an electrically conductive layer that covers at least the bottom electrode and the anchor arrangement such that a cavity is formed between the bottom electrode, the anchor arrangement and the electrically conductive layer, wherein, on at least one side of the cavity, a proportionate area of the electrically conductive walls in a cross section extending from a surface of an inner wall of the anchor arrangement facing the cavity to a surface of an outermost wall of the anchor arrangement facing away from the cavity in a plane parallel to a plane of the bottom electrode is equal to or less than 10%.
Claims
1. A pressure sensor module comprising: a base electrode surrounding at least a part of a bottom electrode; an anchor arrangement on top of the base electrode comprising at least two electrically conductive walls that both surround at least the part of the bottom electrode; and an electrically conductive layer that covers at least the bottom electrode and the anchor arrangement such that a cavity is formed between the bottom electrode, the anchor arrangement and the electrically conductive layer, wherein, on at least one side of the cavity, a proportionate area of the electrically conductive walls in a cross section extending from a surface of an inner wall of the anchor arrangement facing the cavity to a surface of an outermost wall of the anchor arrangement facing away from the cavity in a plane parallel to a plane of the bottom electrode is equal to or less than 10% of an area of the anchor arrangement.
2. The pressure sensor module according to claim 1, wherein the electrically conductive layer forms a suspended membrane.
3. The pressure sensor module according to claim 1, wherein the electrically conductive walls of the anchor arrangement are in electrical and mechanical contact with the base electrode.
4. The pressure sensor module according to claim 1, wherein the proportionate area of the electrically conductive walls in the cross section has approximately the same value in all planes that are parallel to the bottom electrode and positioned between the electrically conductive layer and the base electrode.
5. The pressure sensor module according to claim 1, wherein the pressure sensor module is positioned on top of an integrated circuit.
6. The pressure sensor module according to claim 1, wherein the proportionate area of the electrically conductive walls in the anchor arrangement within the cross section is at least 0.5%.
7. The pressure sensor module according to claim 1, wherein the anchor arrangement has a rectangular shape.
8. The pressure sensor module according to claim 1, wherein the anchor arrangement further comprises electrically conductive vias between the at least two electrically conductive walls of the anchor arrangement which are also connected to the base electrode and to the electrically conductive layer, and wherein the proportionate area of the electrically conductive walls and vias in a total cross section extending from the surface of the inner wall of the anchor arrangement facing the cavity to the surface of the outermost wall of the anchor arrangement facing away from the cavity in a plane parallel to the plane of the bottom electrode is between 0.5% and 10%.
9. The pressure sensor module according to claim 1, wherein the anchor arrangement further comprises electrically conductive structures between the at least two electrically conductive walls of the anchor arrangement which are also connected to the base electrode and the electrically conductive layer, and wherein the proportionate area of the electrically conductive walls and structures in a total cross section extending from the surface of the inner wall of the anchor arrangement facing the cavity to the surface of the outermost wall of the anchor arrangement facing away from the cavity in a plane parallel to the plane of the bottom electrode is between 0.5% and 10%.
10. The pressure sensor module according to claim 1, wherein a top of the electrically conductive walls of the anchor arrangement facing the electrically conductive layer is topographically flat due to chemical mechanical polishing.
11. The pressure sensor module according to claim 1, wherein an isolation layer is formed on top of the bottom electrode and below the cavity.
12. A method for forming a pressure sensor module, the method comprising: forming at least two trenches surrounding at least a part of an area by patterning of a sacrificial layer; depositing an electrically conductive material on top of the sacrificial layer and in the trenches such that an anchor arrangement comprising at least two electrically conductive walls is formed; removing a portion of the electrically conductive material; depositing an electrically conductive layer covering at least the anchor arrangement and the sacrificial layer; and removing the sacrificial layer through at least one etch opening in the electrically conductive layer such that a cavity is formed below the electrically conductive layer, wherein, on at least one side of the cavity, a proportionate area of the electrically conductive walls in a cross section extending from a surface of an inner wall of the anchor arrangement facing the cavity to a surface of an outermost wall of the anchor arrangement facing away from the cavity in a plane parallel to a plane of the electrically conductive layer is between 0.5% and 10% of an area of the anchor arrangement.
13. The method for forming the pressure sensor module according to claim 12, wherein the electrically conductive layer forms a suspended membrane.
14. The method for forming the pressure sensor module according to claim 12, wherein the pressure sensor module is positioned on top of an integrated circuit.
15. The method for forming the pressure sensor module according to claim 12, wherein the portion of the electrically conductive material is removed by chemical mechanical polishing.
16. The method for forming the pressure sensor module according to claim 12, wherein the anchor arrangement has a rectangular shape.
17. The method for forming the pressure sensor module according to claim 12, further comprising providing a bottom electrode below the cavity.
18. The method for forming the pressure sensor module according to claim 17, further comprising forming an isolation layer on top of the bottom electrode and below the cavity.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The following description of figures may further illustrate and explain exemplary embodiments. Components that are functionally identical or have an identical effect are denoted by identical references. Identical or effectively identical components might be described only with respect to the figures where they occur first. Their description is not necessarily repeated in successive figures.
(2) FIG. 1 shows a cutaway view of an exemplary embodiment of the pressure sensor module;
(3) FIG. 2 shows a top view of an exemplary embodiment of the anchor arrangement on top of the base electrode;
(4) FIG. 3A shows a height profile for two different devices;
(5) FIG. 3B shows a cutaway view of a device with a closed top electrode;
(6) FIG. 3C shows a cutaway view of a device with a suspended membrane;
(7) FIG. 3D shows a cutaway view of an exemplary embodiment of an anchor arrangement;
(8) FIGS. 4A and 4B show a top view on a section of an anchor arrangement;
(9) FIG. 5A shows a top view of an exemplary embodiment of a square-shaped anchor arrangement;
(10) FIG. 5B shows a height profile along the anchor arrangement shown in FIG. 5A;
(11) FIG. 6A shows a zoom-in of the height profile in FIG. 5B;
(12) FIG. 6B shows a cutaway view of a part of an exemplary embodiment of a pressure sensor module;
(13) FIGS. 7A, 7B and 7C show cutaway views of different embodiments of the anchor arrangement;
(14) FIGS. 8A to 8E show top views of exemplary embodiments of electrically conductive structures within the anchor arrangement;
(15) FIG. 9A shows a cutaway view of a part of an exemplary embodiment of an anchor arrangement;
(16) FIG. 9B shows a height profile along the embodiment shown in FIG. 9A; and
(17) FIG. 9C shows a cutaway view of another exemplary embodiment of an anchor arrangement.
DETAILED DESCRIPTION
(18) FIG. 1 shows a cutaway view of an exemplary embodiment of a pressure sensor module 10 on top of a passivation layer 11 of an integrated circuit 12. The integrated circuit 12 can be, for example, a complementary metal oxide semiconductor device. The semiconductor device may include a contact pad 13. On top of the passivation layer 11 there is a base electrode 14 that surrounds at least a part of a bottom electrode 15. The base electrode 14 and the bottom electrode 15 are electrically isolated from each other by a etch stop layer 16 on top and in between the base electrode 14 and the bottom electrode 15. Above the etch stop layer 16 a cavity 17 is formed below an electrically conductive layer 18 and bordered by an anchor arrangement 20. The anchor arrangement 20 comprises at least two electrically conductive walls 19 which are connected to the base electrode 14 and the electrically conductive layer 18 and which surround at least a part of the bottom electrode 15. Below the electrically conductive layer 18 there may be an adhesion layer 21 and there may be another adhesion layer 22 on top of the electrically conductive layer 18. The electrically conductive layer 18 and the adhesion layers 21 and 22 comprise several etch openings 23. On top of the electrically conductive layer 18 and the adhesion layers 21, 22 there is a sealing layer 24 that laterally extends also over other parts of the device. Vias 25 connect the pressure sensor module 10 to an electrically conductive layer 18 of the integrated circuit 12. Cutaway views of the semiconductor device or the pressure sensor module 10 are given along the x or y axis and top views are given along the z axis.
(19) With the pressure sensor module 10 being positioned on top of the integrated circuit 12 and not next to it the extent of the device can be reduced such that the device requires less area on the chip.
(20) FIG. 2 shows a top view of an exemplary embodiment of the anchor arrangement 20. The at least two electrically conductive walls 19 are arranged on top of the base electrode 14 and surround the bottom electrode 15. The surface 32 of the inner wall of the anchor arrangement 20 faces the cavity 17 and the surface 33 of the outermost wall of the anchor arrangement 20 faces away from the cavity 17.
(21) FIG. 3A shows two height profiles along the x axis for two different devices. Profile 26 is the height profile for a device where a sacrificial layer 27 is positioned below the electrically conductive layer 18. The height profile is recorded on top of the anchor arrangement 20 and the sacrificial layer 27 in a lateral direction x. At the position of the anchor arrangement 20, the height is reduced in comparison to the sacrificial layer 27. This difference in height is referred to as the step height 28. The profile 29 is a height profile along a pressure sensor module 10 in lateral direction x. This means that the cavity 17 is between the anchor arrangement 20, the bottom electrode 15 and the electrically conductive layer 18. The height profile shows that the electrically conductive walls 19 and the anchor arrangement 20 are not of the same height. This means that also in this case a step height 28 is recorded. The recorded step height can be 30 to 80 nm.
(22) FIG. 3B shows a cutaway view of a part of a device with a sacrificial layer 27 between the bottom electrode 15 and the electrically conductive layer 18. Profile 26 is recorded for a device as depicted in FIG. 3B.
(23) FIG. 3C shows a cutaway view of a part of a device with a suspended membrane 30. Between the suspended membrane 30, the bottom electrode 15 and the anchor arrangement 20 there is a cavity 17. Profile 29 is recorded for a device as shown in FIG. 3C.
(24) FIG. 3D shows a cutaway view of an exemplary embodiment of an anchor arrangement 20. A sacrificial layer 27 is positioned on top of the base electrode 14 and the bottom electrode 15 and the electrically conductive walls 19 of the anchor arrangement 20 are positioned on top of the base electrode 14. The electrically conductive walls 19 may not all be of the same height due to erosion induced by the CMP process. Therefore, the actual height of the anchor arrangement 20 is reduced in comparison to the thickness of the sacrificial layer 27. The arrow below the walls 19 of the anchor arrangement 20 illustrates the extent of the cross section through the anchor arrangement 20.
(25) FIG. 4A shows a top view of a section of an exemplary embodiment of an anchor arrangement 20 which has a rectangular shape. The anchor arrangement 20 comprises several electrically conductive walls 19 that are parallel to each other.
(26) FIG. 4B shows a top view of a section of an exemplary embodiment of the anchor arrangement 20 in which the electrically conductive walls 19 are parallel to each other. A squared area 31 can be defined as a cross-section through the anchor arrangement 20 in the x-y plane.
(27) FIG. 5A shows a top view of an exemplary embodiment of the anchor arrangement 20 that has the shape of a square. The electrically conductive walls 19 are parallel to each other.
(28) FIG. 5B shows a height profile along the anchor arrangement 20 depicted in FIG. 5A along the x axis. The two encircled areas correspond to two parts of the anchor arrangement 20. In this embodiment the high percentage of the proportionate area of the electrically conductive walls 19 in a cross section through the anchor arrangement 20 leads to a reduction in height within the anchor arrangement 20 in comparison to the height of the sacrificial layer 27.
(29) FIG. 6A shows a height profile which is a zoom-in of the height profile depicted in FIG. 5B. The smaller picture shows a top view on the electrically conductive walls 19 of the anchor arrangement 20 at the respective position in the height profile. The height profile shows again the reduction in height in the region of the anchor arrangement 20.
(30) FIG. 6B shows a schematic cutaway view of the anchor arrangement 20, the sacrificial layer 27 and a part of the electrically conductive layer 18. The electrically conductive wall 19 can be about 20 nm higher than the rest of the sacrificial layer 27 due to oxide loss during the CMP step.
(31) FIG. 7A shows a schematic cutaway view of a part of the anchor arrangement 20 without the base electrode 14. The electrically conductive material of the electrically conductive walls 19 in the anchor arrangement 20 is also deposited on top of the sacrificial layer 27.
(32) FIG. 7B shows the same structure as in FIG. 7A after the CMP step. Due to the high fraction of the material of the electrically conductive walls 19 within a cross section through the anchor arrangement 20, erosion takes place on top of the anchor arrangement 20 during the CMP step. Therefore, the electrically conductive walls 19 are not of the same height and the height of the electrically conductive walls 19 in the center of the anchor arrangement 20 is significantly reduced in comparison to the height of the surrounding sacrificial layer 27.
(33) FIG. 7C shows a schematic cutaway view of an anchor arrangement 20 where the fraction of the material of the electrically conductive walls 19 within a cross section through the anchor arrangement 20 is reduced in comparison to the case depicted in FIG. 7B. With this reduced fraction of material of the electrically conductive walls 19 within the anchor arrangement 20, the erosion during the CMP step is also reduced and the height of the electrically conductive walls 19 is approximately the same as of the remaining sacrificial layer 27. The arrow below the walls 19 of the anchor arrangement 20 illustrates the extent of the cross section through the anchor arrangement 20.
(34) FIG. 8A shows a top view on a part of the anchor arrangement 20. In this exemplary embodiment circular vias 34 are positioned between the electrically conductive walls 19 of the anchor arrangement 20.
(35) FIG. 8B shows a top view on a part of the anchor arrangement 20. In this exemplary embodiment further electrically conductive structures 35 are positioned between the electrically conductive walls 19 of the anchor arrangement 20. In an exemplary embodiment these further electrically conductive structures 35 can be ring-shaped.
(36) FIG. 8C shows a top view on a part of the anchor arrangement 20. In this exemplary embodiment the electrically conductive structures 35 form the outer edge of a square.
(37) FIG. 8D shows a top view on a part of the anchor arrangement 20. In this exemplary embodiment the electrically conductive structures 35 form the outer edge of a rectangle.
(38) FIG. 8E shows a top view on a part of the anchor arrangement 20. In this exemplary embodiment the electrically conductive structures 35 form a cross between the electrically conductive walls 19.
(39) FIG. 9A shows a cutaway view of the anchor arrangement 20 and a part of the sacrificial layer 27. The fraction of the material of the electrically conductive walls 19 within a cross section through the anchor arrangement 20 is so high that the CMP step incudes erosion in the region of the anchor arrangement 20. Therefore, the height of the electrically conductive layer 18 on top of the anchor arrangement 20 and the sacrificial layer 27 is reduced in the region of the anchor arrangement 20 in comparison to the adjacent cavity 17.
(40) FIG. 9B shows a height profile along the structure depicted in FIG. 9A.
(41) FIG. 9C shows a cutaway view of the anchor arrangement 20 with a part of the sacrificial layer 27 where the fraction of the material of the electrically conductive walls 19 in a cross section through the anchor arrangement 20 is reduced in comparison to the case depicted in FIG. 9A. Therefore, the CMP step does not induce erosion in the area of the anchor arrangement 20 and thus the electrically conductive walls 19 all exhibit approximately the same height and there is no difference in height in the electrically conductive layer 18.
