A MEMS sensor

Abstract

The utility model provides a MEMS sensor, which includes: a substrate layer; a MEMS layer, which is located on one side surface of the substrate layer, and a MEMS sensor structure is formed in the MEMS layer; a cap layer, which is located on one side surface of the MEMS layer away from the substrate layer; a bottom blocking block, which is located on one side surface of the MEMS layer adjacent to the substrate layer, and the bottom blocking block is spaced from the substrate layer to limit the movement of the movable parts in the MEMS sensor structure. Compared with the prior art, the utility model sets a blocking block on the MEMS layer to replace the oxide blocking block, so as to limit the displacement of the movable parts in the MEMS layer while avoiding the generation of electrostatic force.

Description

[Technical field]

[0001] The utility model relates to the technical field of MEMS (Micro-Electro-Mechanical System), in particular to a MEMS sensor. [Background technology]

[0002] Common MEMS structures use insulating oxides such as silicon oxide as blocking blocks to limit MEMS movement, but the insulator will accumulate a large amount of charge and generate electrostatic force during the collision process. The electrostatic force will pull the movable parts of the MEMS sensor, thereby affecting the component output signal or causing the movable parts to get stuck.

[0003] Please refer to Figure 1 As shown, it is a cross-sectional view of a common capacitive accelerometer Z-axis structure in the prior art.

[0004] The cap layer 110 and the MEMS layer 120 are bonded and fixed by the first bonding layer 130, and the bonding area is provided by the first connecting portion 112 of the cap layer 110. The first bonding layer 130 is usually oxide melt bonding, but is not limited thereto.

[0005] The substrate layer 140 and the MEMS layer 120 are bonded and fixed via a second bonding layer 150 . The bonding area is provided by the second connection portion 122 of the MEMS layer 120 and the metal layer 160 above the substrate layer 140 . The second bonding layer 150 is usually aluminum-germanium eutectic bonding, but is not limited thereto.

[0006] The anchoring structure 123 in the MEMS layer 120 simultaneously connects the cap layer 110 , the MEMS layer 120 , and the substrate layer 140 , providing support for the MEMS layer 120 .

[0007] The positive mass block 124 and the negative mass block 126 in the MEMS layer 120 are connected to the anchor structure 123 via the MEMS torsion spring 127. Due to the asymmetric mass, when the element is subjected to Z-direction acceleration, the positive mass block 124 and the negative mass block 126 will rotate up and down like a seesaw.

[0008] The positive sensing electrode 162 and the negative sensing electrode 164 in the metal layer 160 are respectively located below the positive mass block 124 and the negative mass block 126. When the mass blocks 124 and 126 are displaced, the distance between the sensing electrodes 162 and 164 changes, so the inter-plate capacitance between the sensing electrodes 162 and 164 and the mass blocks 124 and 126 changes, thereby outputting an electrical signal to achieve the purpose of detecting acceleration.

[0009] The silicon oxide stopper 170 is located below the mass blocks 124 and 126. When the mass blocks 124 and 126 swing up and down, they will collide with the silicon oxide stopper 170 and limit their displacement to prevent damage caused by excessive swing. However, since silicon oxide is an insulator, excessive collisions will accumulate a large amount of charge and generate electrostatic force. The electrostatic force attracts the mass blocks 124 and 126, causing them to deviate or get stuck, affecting the operation of the components.

[0010] Therefore, it is necessary to propose a new technical solution to solve the above problems. [Contents of the utility model]

[0011] One of the purposes of the utility model is to provide a MEMS sensor, which is provided with a stopper on the MEMS layer to replace the oxide stopper, so as to limit the displacement of the movable parts in the MEMS layer and avoid the generation of electrostatic force.

[0012] According to one aspect of the utility model, the utility model provides a MEMS sensor, which includes: a substrate layer; a MEMS layer, which is located on one side surface of the substrate layer, and a MEMS sensor structure is formed in the MEMS layer; a cap layer, which is located on one side surface of the MEMS layer away from the substrate layer; a bottom stop block, which is located on one side surface of the MEMS layer adjacent to the substrate layer, and the bottom stop block is spaced from the substrate layer to limit the movement of movable parts in the MEMS sensor structure.

[0013] Compared with the prior art, the utility model arranges a blocking block on the MEMS layer to replace the oxide blocking block, thereby limiting the displacement of the movable parts in the MEMS layer while avoiding the generation of electrostatic force.

Brief Description of the Drawings

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following briefly introduces the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0015] Figure 1 It is a cross-sectional view of a common capacitive accelerometer Z-axis structure in the prior art;

[0016] Figure 2 A longitudinal cross-sectional schematic diagram of a MEMS sensor in one embodiment of the utility model;

[0017] Figure 3 In one embodiment of the present invention, Figure 2 Flowchart of a method for manufacturing a MEMS sensor shown. [Specific implementation method]

[0018] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0019] The term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments. Unless otherwise specified, the words "connected", "connected" and "connected" herein that indicate electrical connection all refer to direct or indirect electrical connection.

[0020] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "front", "back", "left", "right", "vertical", "perpendicular", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0021] Please refer to Figure 2 As shown, it is a longitudinal cross-sectional schematic diagram of a MEMS sensor in one embodiment of the utility model.

[0022] For better explanation Figure 2 The structure of the MEMS sensor shown in the figure can establish a three-dimensional rectangular coordinate system. Figure 2 In the embodiment shown, the X-axis and the Y-axis are perpendicular to each other and define Figure 2 The substrate of the MEMS sensor shown in the figure is located in a plane where the Z axis is perpendicular to the plane defined by the X axis and the Y axis. The three-dimensional rectangular coordinate system established by the X axis, the Y axis and the Z axis is in Figure 2 It is reflected in the figure, where the X-axis is along the left-right direction, the Y-axis is perpendicular to the paper surface, and the Z-axis is along the up-down direction.

[0023] Figure 2The MEMS sensor shown includes a cap layer 210, a MEMS layer 220, a substrate layer 240, and bottom stoppers 225a and 225b. The MEMS layer 220 is located on one side of the substrate layer 240, and a MEMS sensor structure (not labeled) is formed in the MEMS layer 220; the cap layer 210 is located on one side of the MEMS layer 220 away from the substrate layer 240; the bottom stoppers 225a and 225b are located on one side of the MEMS layer 220 adjacent to the substrate layer 240, and the bottom stoppers 225a and 225b are spaced apart from the substrate layer 240 to limit the movement of the movable parts in the MEMS sensor structure (not labeled).

[0024] exist Figure 2 In the specific embodiment shown, the bottom blocking blocks 225a, 225b and the movable parts of the MEMS layer 220 are an integral structure; the bottom blocking blocks 225a, 225b and the MEMS layer 220 are made of the same material; and the bottom blocking blocks 225a, 225b are formed by etching the MEMS layer 220.

[0025] exist Figure 2 In the illustrated embodiment, the cap layer 210 includes a groove 216 . The groove 216 extends from a surface of the cap layer 210 adjacent to the MEMS layer 220 to the inside of the cap layer 210 . The groove 216 is formed by etching the cap layer 210 .

[0026] Figure 2 The MEMS sensor shown also includes a first bonding layer 230 and a second bonding layer 250. The first bonding layer 230 is located between the first connection portion 212 of the cap layer 210 and the MEMS layer 220, and the first connection portion 212 of the cap layer 210 is bonded to the MEMS layer 220 through the first bonding layer 230, wherein the first connection portion 212 of the cap layer 210 is located on a side surface of the cap layer 210 adjacent to the MEMS layer 220, and the first connection portion 212 of the cap layer 210 is formed by etching the cap layer 210. The second bonding layer 250 is located between the second connection portion 222 of the MEMS layer 220 and the substrate layer 240, and the second connection portion 222 of the MEMS layer 220 is bonded to the substrate layer 240 through the second bonding layer 250, wherein the second connection portion 222 of the MEMS layer 220 is located on a side surface of the MEMS layer 220 adjacent to the substrate layer 240, and the second connection portion 222 of the MEMS layer 220 is formed by etching the MEMS layer 220.

[0027] Figure 2The MEMS sensor shown also includes a metal layer 260, which is deposited and patterned on a side surface of the substrate layer 240 adjacent to the second bonding layer 250; the substrate layer 240 is bonded to the second connecting portion 222 of the MEMS layer 220 through the metal layer 260 and the second bonding layer 250; the bottom blocking blocks 225a, 225b are spaced apart from the metal layer 260 to limit the movement of the movable parts in the MEMS sensor structure (not marked).

[0028] exist Figure 2 In the specific embodiment shown, the MEMS sensor structure (not labeled) formed in the MEMS layer 220 is a capacitive MEMS sensor structure. Among them, the first bonding layer 230 is an oxide bonding layer (for example, an oxide film); the second bonding layer 250 is a metal bonding layer (for example, a metal germanium layer); the MEMS sensor structure (not labeled) includes an anchoring structure 223, a first torsion spring 227a and a second torsion spring 227b in addition to a movable part (not labeled); the movable part includes a first mass block (or a positive mass block) 224 and a second mass block (or a negative mass block) 226; the anchoring structure 223 is bonded to the cap layer 210 through the first bonding layer 230, and the anchoring structure 223 is bonded to the substrate layer 240 through the second bonding layer 250 and the metal layer 260;

[0029] The first mass block 224 is located in the first cavity A surrounded by the cap layer 210, the anchoring structure 223 and the substrate layer 240; the second mass block 226 is located in the second cavity B surrounded by the cap layer 210, the anchoring structure 223 and the substrate layer 240; the first mass block 224 is connected to the anchoring structure 223 through the first torsion spring 227a; the second mass block 226 is connected to the anchoring structure 223 through the second torsion spring 227b; the mass of the first mass block 224 is greater than the mass of the second mass block 226, and when subjected to acceleration in the Z-axis direction, the first mass block 224 and the second mass block 226 perform a seesaw motion. The patterned metal layer 260 includes a first electrode (or positive sensing electrode) 262 located below the first mass block 224 and a second electrode (or negative sensing electrode) 264 located below the second mass block 226; there are two bottom blocking blocks 225a and 225b, respectively denoted as a first bottom blocking block 225a and a second bottom blocking block 225b, the first bottom blocking block 225a is located in the first cavity A and located on a side surface of the first mass block 224 adjacent to the substrate layer 240; the second bottom blocking block 225b is located in the second cavity B and located on a side surface of the second mass block 226 adjacent to the substrate layer 240. The Z-axis direction is the sensitive direction of acceleration.

[0030] Please refer to Figure 3 As shown, the utility model is in one embodiment as Figure 2Flowchart of a method for manufacturing a MEMS sensor shown. Figure 3 The manufacturing method of the MEMS sensor shown includes the following steps.

[0031] Step 310 , providing a cap wafer 210 , a MEMS wafer 220 and a substrate wafer 240 .

[0032] Step 320 , bonding the first surface of the cap wafer 210 to the first surface of the MEMS wafer 220 .

[0033] Step 330, back-etching the MEMS wafer 220 from the second surface of the MEMS wafer 220 away from the cap wafer 210 to form a MEMS sensor structure, a second connecting portion 222 and bottom stoppers 225a, 225b in the MEMS wafer 220. Figure 2 In the illustrated embodiment, the MEMS sensor structure includes a first torsion spring 227a, a second torsion spring 227b, a first mass block (or positive mass block) 224, and a second mass block (or negative mass block) 226, etc.; the back etching performed on the MEMS wafer 220 can be DIRE (Deep Reactive Ion Etching).

[0034] Step 350 , depositing a second bonding layer 250 (eg, a metal germanium layer) on a second surface of the MEMS wafer 220 on which the MEMS sensor structure, the second connecting portion 222 and the bottom stoppers 225 a and 225 b are formed, away from the cap wafer 210 .

[0035] Step 360 , patterning the second bonding layer 250 to remove the second bonding layer 250 in the MEMS sensor structure region and on the surfaces of the bottom stoppers 225 a and 225 b , and retaining the second bonding layer 250 on the second connection portion 222 .

[0036] It can be seen from steps 350 and 360 that after the second bonding layer 250 (for example, a metal germanium layer) is deposited on the second surface of the MEMS wafer 220 away from the cap wafer 210, the back of the entire MEMS sensor structure, the second connecting portion 222 and the bottom blocking block 225a will be covered by the second bonding layer 250 (for example, a metal germanium layer). It is necessary to etch and remove the second bonding layer 250 (for example, a metal germanium layer) on the back of the MEMS sensor structure area. At this time, the second bonding layer 250 (for example, a metal germanium layer) on the surface of the bottom blocking blocks 225a and 225b is also removed, so that the bottom blocking blocks 225a and 225b cannot be bonded to the metal layer 360 mentioned below to form a movable gap, so as to limit the movement of the movable parts in the MEMS sensor structure (not marked).

[0037] In step 380 , the second connection portion 222 of the MEMS wafer 220 is bonded to the substrate wafer 240 via the second bonding layer 250 .

[0038] exist Figure 2 In the specific embodiment shown, the bottom stoppers 225a, 225b are integrally structured with the movable parts of the MEMS layer 220; the bottom stoppers 225a, 225b are spaced apart from the substrate layer 240 to limit the movement of the movable parts in the MEMS sensor structure (not marked).

[0039] Figure 3 The manufacturing method of the MEMS sensor shown also includes step 370, depositing and patterning a metal layer 260 on the first surface of the substrate wafer 240. Correspondingly, step 380, the second connection portion 222 of the MEMS wafer 220 is bonded to the substrate wafer 240 through the second bonding layer 250 and the metal layer 260. The bottom stopper blocks 225a, 225b are spaced apart from the metal layer 260 to limit the movement of the movable parts in the MEMS sensor structure (not marked).

[0040] exist Figure 3 In the specific embodiment shown, step 320 specifically includes:

[0041] Step 322 , etching the cap wafer 210 to form a groove 216 and a first connecting portion 212 on the first surface of the cap wafer 210 .

[0042] Step 324 , depositing a first bonding layer 230 on the first surface of the cap wafer 210 formed with the groove 216 and the first connecting portion 212 , wherein the first bonding layer 230 covers the inner wall of the groove 216 and the surface of the first connecting portion 212 .

[0043] Step 326 , bonding the first connection portion 212 of the cap wafer 210 to the first surface of the MEMS wafer through the first bonding layer 230 .

[0044] Figure 3 The manufacturing method of the MEMS sensor shown further includes: step 340 between step 330 and step 350, removing the first bonding layer 230 on the inner wall of the groove 216 by etching. The first bonding layer 230 on the inner wall of the groove 216 can be removed by wet etching.

[0045] In this way, we can obtain Figure 2 The MEMS sensor shown. Figure 2In the MEMS sensor shown, when the mass blocks 224 and 226 twist, the gap between the bottom blocking blocks 225a and 225b and the metal layer 260 is small, so the mass blocks 224 and 226 will collide with the metal layer 260 with the same potential. Since the bottom blocking blocks 225a and 225b and the MEMS wafer 220 are the same wafer, their materials are non-insulating materials such as silicon, so no charge will be accumulated during the collision, thereby avoiding the influence of electrostatic force.

[0046] It should be noted that, from the perspective of semiconductor wafers before being cut, that is, from the perspective of the semiconductor wafer level, the cap wafer 210, the MEMS wafer 220 and the substrate wafer 240 are three independent semiconductor wafers; from the perspective of semiconductor wafers after being cut, that is, from the chip level perspective, the cap wafer 210, the MEMS wafer 220 and the substrate wafer 240 can be understood as chips of each semiconductor wafer; or the cap wafer 210, the MEMS wafer 220 and the substrate wafer 240 can be understood as the cap layer 210, the MEMS layer 220 and the substrate layer 240.

[0047] In summary, the MEMS sensor and the manufacturing method thereof provided by the utility model have the following beneficial effects:

[0048] 1. The utility model can be used for common MEMS structures such as capacitive ones to limit the displacement of the MEMS movable structure and prevent device damage.

[0049] 2. The blocking blocks 214a and 214b of the present invention are non-insulators and do not accumulate charges compared to common oxide blocking blocks, thereby preventing electrostatic forces from affecting device operation.

[0050] 3. The utility model is based on the common MEMS process flow and does not require the introduction of additional processes.

[0051] In the present invention, words such as “connect”, “connected”, “connected”, “connected”, etc. indicating electrical connection, if not otherwise specified, indicate direct or indirect electrical connection.

[0052] The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. Any equivalent modifications or changes made by ordinary technicians in this field based on the disclosure of the present invention should be included in the protection scope recorded in the claims.

Claims

1. A MEMS sensor, characterized in that: It includes: substrate layer; A MEMS layer, which is located on one side surface of the substrate layer, and a MEMS sensor structure is formed in the MEMS layer; A cap layer, which is located on a surface of the MEMS layer away from the substrate layer; A bottom stopper is located on a side surface of the MEMS layer adjacent to the substrate layer, and the bottom stopper is spaced apart from the substrate layer to limit the movement of the movable component in the MEMS sensor structure.

2. The MEMS sensor according to claim 1, characterized in that: The bottom stopper and the movable part of the MEMS layer are an integral structure; The bottom stopper is made of the same material as the MEMS layer; The bottom stopper is formed by etching the MEMS layer.

3. The MEMS sensor according to claim 2, characterized in that: The capping layer comprises a groove, The groove extends from a surface of the cap layer adjacent to the MEMS layer to the inside of the cap layer; The groove is formed by etching the cap layer.

4. The MEMS sensor according to any one of claims 1 to 3, characterized in that: It also includes: A first bonding layer, which is located between the first connection portion of the cap layer and the MEMS layer, the first connection portion of the cap layer is bonded to the MEMS layer through the first bonding layer, and the first connection portion of the cap layer is formed by etching the cap layer; The second bonding layer is located between the second connection portion of the MEMS layer and the substrate layer. The second connection portion of the MEMS layer is bonded to the substrate layer through the second bonding layer. The second connection portion of the MEMS layer is formed by etching the MEMS layer.

5. The MEMS sensor according to claim 4, characterized in that: It also includes a metal layer, The metal layer is deposited and patterned on a surface of the substrate layer adjacent to the second bonding layer; The substrate layer is bonded to the second connection portion of the MEMS layer through the metal layer and the second bonding layer; The bottom stopper and the metal layer are spaced apart from each other to limit the movement of the movable component.

6. The MEMS sensor according to claim 5, characterized in that: The MEMS sensor structure is a capacitive MEMS sensor structure; The first bonding layer is an oxide bonding layer; The second bonding layer is a metal bonding layer; The MEMS sensor structure further includes an anchoring structure, a first torsion spring and a second torsion spring; the movable component includes a first mass block and a second mass block; the anchoring structure is bonded to the cap layer through the first bonding layer, and the anchoring structure is bonded to the substrate layer through the second bonding layer and the metal layer; The first mass block is located in a first cavity surrounded by the cap layer, the anchoring structure and the substrate layer; The second mass block is located in a second cavity surrounded by the cap layer, the anchoring structure and the substrate layer; The first mass block is connected to the anchoring structure through the first torsion spring; the second mass block is connected to the anchoring structure through the second torsion spring; the mass of the first mass block is greater than the mass of the second mass block, and when subjected to acceleration in a sensitive direction, the first mass block and the second mass block perform a seesaw motion; The patterned metal layer includes a first electrode located below the first mass block and a second electrode located below the second mass block; There are two bottom blocking blocks, which are respectively referred to as a first bottom blocking block and a second bottom blocking block. The first bottom blocking block is located in the first cavity and on a side surface of the first mass block adjacent to the substrate layer; the second bottom blocking block is located in the second cavity and on a side surface of the second mass block adjacent to the substrate layer.

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