Pressure sensor and packaging method thereof

Abstract

The invention provides a pressure sensor and a packaging method thereof, and relates to the technical field of pressure sensors. A first bonding body and a second bonding body are prepared respectively, one side of the first bonding body is provided with a first electrode layer and a pressure-sensitive area, and one side of the second bonding body is provided with a second electrode layer and a first cavity. And then the first bonding body and the second bonding body are bonded through a bonding process, so that the first electrode layer is in contact with the second electrode layer, the pressure-sensitive area and the first cavity are oppositely arranged, and a sealed cavity is formed. And finally, a second cavity is prepared and formed in the side, away from the second bonding body, of the first bonding body, a bonding pad is prepared and formed on the second bonding body, the second cavity and the pressure-sensitive area are oppositely arranged, and the bonding pad is communicated with the second electrode layer. According to the technical scheme, the point-to-point connection between the SOI substrate and the silicon wafer is realized by using the first electrode layer and the second electrode layer, the electrical performance and the space utilization rate of the pressure sensor can be greatly optimized, and the miniaturization requirement of the MEMS pressure sensor is particularly met.

Description

Technical Field

[0001] This invention relates to the field of pressure sensor technology, and in particular to a pressure sensor and its packaging method. Background Technology

[0002] In pressure sensor packaging, traditional wire bonding connects the chip's front-side pads to the substrate using metal leads, such as gold or copper wires. This packaging method suffers from signal delay, poor heat dissipation, large package size, and poor electrical performance. Therefore, there is an urgent need to design a packaging method that can optimize the electrical performance of pressure sensors while reducing their size. Summary of the Invention

[0003] One objective of this invention is to provide a packaging method for a pressure sensor, thereby solving the technical problems of poor electrical performance and large size caused by lead wires in the packaging of pressure sensors in the prior art.

[0004] Specifically, the present invention provides a method for packaging a pressure sensor, comprising the following steps: A first bond and a second bond are prepared respectively. One side of the first bond has a first electrode layer and a pressure-sensitive region, and one side of the second bond has a second electrode layer and a first cavity. The first bonding body and the second bonding body are bonded together by a bonding process, so that the first electrode layer and the second electrode layer are in contact, and the pressure-sensitive area and the first cavity are arranged opposite to each other to form a sealed cavity; A second cavity is formed on the side of the first bond body away from the second bond body, and a pad is formed on the second bond body. The second cavity is arranged opposite to the pressure-sensitive region, and the pad is connected to the second electrode layer.

[0005] Optionally, the steps of preparing the first bond and the second bond separately include the following steps: An SOI substrate is provided, the SOI substrate comprising a top silicon layer; An active region is formed on the top silicon layer; The first electrode layer is formed on the upper surface of the active region; A deep silicon trench is etched on the top silicon layer to form the pressure-sensitive region, thereby preparing the first bond.

[0006] Optionally, the steps of preparing the first bond and the second bond separately further include the following steps: Silicon wafers are supplied; Through-holes are formed on the silicon wafer; A first oxide layer is formed on the inner wall of the through hole; A metal material is filled into the through hole, and a second electrode layer is formed on the lower surface of the through hole; The first cavity is formed on the lower surface of the silicon wafer to obtain the second bond.

[0007] Optionally, after filling the through-hole with a metallic material and forming the second electrode layer on the lower surface of the through-hole, the method further includes the following steps: A second oxide layer is formed on the upper surface of the silicon wafer, and a third oxide layer is formed on the lower surface of the silicon wafer at the remaining positions, avoiding the second electrode layer.

[0008] Optionally, the step of forming pads on the second bond body specifically includes the following steps: The portion of the second oxide layer corresponding to the through-hole is removed to expose the metal material; The pads are formed on top of the metal material.

[0009] Optionally, both the first electrode layer and the second electrode layer are made of gold.

[0010] Optionally, the first electrode layer is made of germanium, and the second electrode layer is made of aluminum.

[0011] Optionally, the first electrode layer is made of copper, and the second electrode layer is made of tin.

[0012] Optionally, the metallic material is copper.

[0013] In particular, the present invention also provides a pressure sensor, which utilizes the above-described packaging method, comprising: The first bonding body includes an SOI substrate, an active region, a deep silicon trench, and a first electrode layer. The active region and the varistor region are both formed on the top silicon layer of the SOI substrate. The first electrode layer is located above the active region. The bottom silicon layer of the SOI substrate has a second cavity arranged opposite to the varistor region. The second bonding body is bonded to the first bonding body by a bonding process, and includes a silicon wafer, a metal material, and a second electrode layer. The silicon wafer has through holes and a first cavity. The metal material fills the through holes. The second electrode layer is located at the bottom of the metal material and is in contact with the first electrode layer. The first cavity is arranged opposite to the pressure-sensitive area and forms a sealed cavity. The solder pad is located above the metal material.

[0014] This invention first fabricates a first bonding body and a second bonding body. One side of the first bonding body has a first electrode layer and a pressure-sensitive region, while one side of the second bonding body has a second electrode layer and a first cavity. Then, the first and second bonding bodies are bonded together using a bonding process, bringing the first and second electrode layers into contact. This allows the pressure-sensitive region and the first cavity to be arranged opposite each other, forming a sealed cavity. Finally, a second cavity is formed on the side of the first bonding body facing away from the second bonding body, and a bonding pad is formed on the second bonding body. The second cavity is arranged opposite to the pressure-sensitive region, and the bonding pad is connected to the second electrode layer. This technical solution utilizes the first and second electrode layers to achieve point-to-point connection between the SOI substrate and the silicon wafer, significantly optimizing the electrical performance and space utilization of the pressure sensor. It is particularly suitable for the miniaturization requirements of MEMS pressure sensors, such as mobile phone barometers and automotive tire pressure sensors.

[0015] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0016] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic flowchart of a pressure sensor packaging method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a method for preparing a first bond according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a method for preparing a second bond according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the bonding of a first bond and a second bond according to an embodiment of the present invention; Figure 5 This is a schematic flowchart illustrating the preparation of a first bond according to an embodiment of the present invention; Figure 6 This is a schematic flowchart illustrating the preparation of a second bond according to an embodiment of the present invention; Figure label: 100-Pressure sensor, 10-First bond, 20-Second bond, 11-Bottom silicon layer, 12-Silicon oxide layer, 13-Top silicon layer, 14-Active region, 15-First electrode layer, 16-Pressure-sensitive region, 17-Deep silicon trench, 18-Second cavity, 21-Silicon wafer, 22-Through hole, 23-First oxide layer, 24-Metal material, 25-Second electrode layer, 26-Second oxide layer, 27-Third oxide layer, 28-First cavity, 30-Sealed cavity, 40-Pad. Detailed Implementation

[0017] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0018] In the description of this invention, it should be understood that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0019] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature, that is, include one or more of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. When a feature "includes or contains" one or more of the features it encompasses, unless otherwise specifically stated, this indicates that other features are not excluded and may be further included.

[0020] Unless otherwise specified, all terms (including technical and scientific terms) used in the description of this embodiment have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0021] Figure 1 This is a schematic flowchart of a packaging method for a pressure sensor 100 according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a method for preparing a first bond according to an embodiment of the present invention. Figure 3 This is a schematic diagram of a method for preparing a second bond according to an embodiment of the present invention. Figure 4 This is a schematic diagram illustrating the bonding of a first bond and a second bond according to an embodiment of the present invention. Figures 1 to 4 As shown, in one specific embodiment, the packaging method of the pressure sensor 100 includes the following steps: Step S100: Prepare a first bond 10 and a second bond 20 respectively. One side of the first bond 10 has a first electrode layer 15 and a pressure-sensitive region 16, and one side of the second bond 20 has a second electrode layer 25 and a first cavity 28. In step S200, the first bonding body 10 and the second bonding body 20 are bonded together using a bonding process, so that the first electrode layer 15 and the second electrode layer 25 come into contact, and the pressure-sensitive region 16 and the first cavity 28 are arranged opposite to each other, forming a sealed cavity 30; see also Figure 4 Figure (j) in the middle; In step S300, a second cavity 18 is formed on the side of the first bond 10 away from the second bond 20, and a pad 40 is formed on the second bond 20. The second cavity 18 is arranged opposite to the pressure-sensitive region 16, and the pad 40 is connected to the second electrode layer 25.

[0022] This embodiment utilizes the first electrode layer 15 and the second electrode layer 25 to achieve point-to-point connection between the SOI substrate and the silicon wafer 21, which can significantly optimize the electrical performance and space utilization of the pressure sensor 100, especially meeting the miniaturization requirements of MEMS pressure sensors 100, such as mobile phone barometers and car tire pressure sensors.

[0023] Figure 5 This is a schematic flowchart illustrating the preparation of the first bond 10 according to an embodiment of the present invention. Figure 5 As shown, and see Figure 2 In some embodiments, step S100 specifically includes the following steps: Step S110: Provide an SOI substrate, the SOI substrate including a top silicon layer 13; Step S120: An active region 14 is formed on the top silicon layer 13; Step S130: A first electrode layer 15 is formed on the upper surface of the active region 14; In step S140, a deep silicon trench 17 is etched on the top silicon layer 13 to form a pressure-sensitive region 16, thereby preparing the first bond 10.

[0024] In step S110, SOI includes a bottom silicon layer 11, a silicon oxide layer 12, and a top silicon layer 13 arranged sequentially from bottom to top. See [link to relevant documentation]. Figure 2 Figure (a) in the middle.

[0025] In step S120, the active region 14 is specifically obtained through ion implantation. There are two active regions 14, see [link to relevant documentation]. Figure 2 Figure (b) in the middle.

[0026] In step S130, there are two first electrode layers 15, see [link / reference] Figure 2 Figure (c) in the middle.

[0027] In step S140, the deep silicon trench 17 is preferably etched using a Bosch process. There are two deep silicon trenches 17, and the varistor region 16 is located between the two deep silicon trenches 17. See [link to relevant documentation]. Figure 2 Figure (d) in the middle.

[0028] Figure 6 This is a schematic flowchart illustrating the preparation of the second bond 20 according to an embodiment of the present invention. Figure 6 As shown, and see Figure 3 In some embodiments, step S100 further includes the following steps: Step S150, provide silicon wafer 21, see Figure 3 Figure (e) in the middle; Step S160: Form a through-hole 22 on the silicon wafer 21, see [link to relevant documentation]. Figure 3 Figure (f) in the middle; Step S170: A first oxide layer 23 is formed on the inner wall of the through hole 22, see [link to previous step]. Figure 3 (g) diagram; Step S180: Fill the through hole 22 with metal material 24, and form a second electrode layer 25 on the lower surface of the through hole 22. See [link to previous step]. Figure 3 (g) diagram; In step S190, a first cavity 28 is formed on the lower surface of the silicon wafer 21, thereby preparing the second bond 20. (See below) Figure 3 Figure (i) shows the diagram. It should be noted that there is no sequential relationship between steps S150 and S110.

[0029] In step S160, through-hole 22 is formed specifically by deep reactive ion etching, wet etching, or laser drilling.

[0030] In step S170, the first oxide layer 23 can be prepared by chemical vapor deposition.

[0031] In step S180, the metal material 24 is copper. In other embodiments, the metal material 24 may be other materials.

[0032] In some embodiments, the following steps are included after step S180: Step S181: A second oxide layer 26 is formed on the upper surface of the silicon wafer 21, and a third oxide layer 27 is formed on the lower surface of the silicon wafer 21, avoiding the remaining positions of the second electrode layer 25. See [link to previous step]. Figure 3 Figure (h) shows that the second oxide layer 26 and the third oxide layer 27 were specifically prepared by chemical vapor deposition.

[0033] like Figure 4 As shown, in some embodiments, the step of forming the pad 40 on the second bond 20 specifically includes the following steps: In step S320, the portion of the second oxide layer 26 corresponding to the through hole 22 is removed to expose the metal material 24; specifically, the portion of the second oxide layer 26 corresponding to the through hole 22 can be removed by an etching process.

[0034] Step S330: A pad 40 is formed on top of the metal material 24, see [link to previous step]. Figure 4 The middle (l) diagram.

[0035] Before step S320, the following steps are also included: Step S310: A second cavity 18 is formed on the side of the first bonded body 10 opposite to the second bonded body 20, see [link to previous step]. Figure 4 Figure (k) shows the second cavity 18, which can be obtained through an etching process.

[0036] In some embodiments, the first electrode layer 15 and the second electrode layer 25 are both made of gold. This can be understood as the first bond 10 and the second bond 20 employing gold-gold bonding.

[0037] In another embodiment, the first electrode layer 15 is made of germanium, and the second electrode layer 25 is made of aluminum. This can be understood as the first bond 10 and the second bond 20 employing a germanium-aluminum bond.

[0038] In another embodiment, the first electrode layer 15 is made of copper, and the second electrode layer 25 is made of tin. This can be understood as the first bond 10 and the second bond 20 being bonded using copper-tin bonding.

[0039] In some embodiments, a pressure sensor 100 is also provided. Using the packaging method of any of the above embodiments, the pressure sensor 100 includes a first bonding body 10, a second bonding body 20, and a pad 40. The first bonding body 10 includes an SOI substrate, an active region 14, a deep silicon trench 17, and a first electrode layer 15. The active region 14 and the pressure-sensitive region 16 are both formed on the top silicon layer 13 of the SOI substrate. The first electrode layer 15 is located above the active region 14. The bottom silicon layer 11 of the SOI substrate has a second cavity 18 arranged opposite to the pressure-sensitive region 16. The second bonding body 20 is bonded to the first bonding body 10 by a bonding process and includes a silicon wafer 21, a metal material 24, and a second electrode layer 25. The silicon wafer 21 has a through-hole 22 and a first cavity 28. The metal material 24 fills the through-hole 22. The second electrode layer 25 is located at the bottom of the metal material 24 and is in contact with the first electrode layer 15. The first cavity 28 is arranged opposite to the pressure-sensitive region 16 and forms a sealed cavity 30. The pad 40 is located above the metal material 24.

[0040] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A method for packaging a pressure sensor, characterized in that, Includes the following steps: A first bond and a second bond are prepared respectively. One side of the first bond has a first electrode layer and a pressure-sensitive region, and one side of the second bond has a second electrode layer and a first cavity. The first bonding body and the second bonding body are bonded together by a bonding process, so that the first electrode layer and the second electrode layer are in contact, and the pressure-sensitive area and the first cavity are arranged opposite to each other to form a sealed cavity; A second cavity is formed on the side of the first bond body away from the second bond body, and a pad is formed on the second bond body. The second cavity is arranged opposite to the pressure-sensitive region, and the pad is connected to the second electrode layer.

2. The packaging method according to claim 1, characterized in that, The steps for preparing the first bond and the second bond separately include the following steps: An SOI substrate is provided, the SOI substrate comprising a top silicon layer; An active region is formed on the top silicon layer; The first electrode layer is formed on the upper surface of the active region; A deep silicon trench is etched on the top silicon layer to form the pressure-sensitive region, thereby preparing the first bond.

3. The packaging method according to claim 2, characterized in that, The steps of preparing the first bond and the second bond separately further include the following steps: Silicon wafers are supplied; Through-holes are formed on the silicon wafer; A first oxide layer is formed on the inner wall of the through hole; A metal material is filled into the through hole, and a second electrode layer is formed on the lower surface of the through hole; The first cavity is formed on the lower surface of the silicon wafer to obtain the second bond.

4. The packaging method according to claim 3, characterized in that, The steps of filling the through-hole with metallic material and forming the second electrode layer on the lower surface of the through-hole are followed by the following steps: A second oxide layer is formed on the upper surface of the silicon wafer, and a third oxide layer is formed on the lower surface of the silicon wafer at the remaining positions, avoiding the second electrode layer.

5. The packaging method according to claim 4, characterized in that, The step of preparing a pad on the second bond specifically includes the following steps: The portion of the second oxide layer corresponding to the through-hole is removed to expose the metal material; The pads are formed on top of the metal material.

6. The packaging method according to claim 5, characterized in that, Both the first electrode layer and the second electrode layer are made of gold.

7. The packaging method according to claim 5, characterized in that, The first electrode layer is made of germanium, and the second electrode layer is made of aluminum.

8. The packaging method according to claim 5, characterized in that, The first electrode layer is made of copper, and the second electrode layer is made of tin.

9. The packaging method according to claim 8, characterized in that, The metallic material is copper.

10. A pressure sensor, employing the encapsulation method as described in any one of claims 1-9, characterized in that, include: The first bonding body includes an SOI substrate, an active region, a deep silicon trench, and a first electrode layer. The active region and the varistor region are both formed on the top silicon layer of the SOI substrate. The first electrode layer is located above the active region. The bottom silicon layer of the SOI substrate has a second cavity arranged opposite to the varistor region. The second bonding body is bonded to the first bonding body by a bonding process, and includes a silicon wafer, a metal material and a second electrode layer. The silicon wafer has through holes and a first cavity. The metal material fills the through holes. The second electrode layer is located at the bottom of the metal material and is in contact with the first electrode layer. The first cavity is arranged opposite to the pressure-sensitive area and forms a sealed cavity. The solder pad is located above the metal material.

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