CN210084937U

CN210084937U - Back hole lead wire type pressure sensor

Info

Publication number: CN210084937U
Application number: CN201920895399.2U
Authority: CN
Inventors: 李刚; 刘迪; 胡维; 吕萍
Original assignee: Memsensing Microsystems Suzhou China Co Ltd
Current assignee: Memsensing Microsystems Suzhou China Co Ltd
Priority date: 2019-06-14
Filing date: 2019-06-14
Publication date: 2020-02-18
Anticipated expiration: 2029-06-14

Abstract

The utility model provides a back hole lead wire type pressure sensor, which uses the through hole lead wire technology to prepare the pressure sensor, realizes the non-routing paster encapsulation, and reduces the encapsulation size of the pressure sensor; meanwhile, the pressure resistance of the pressure sensor is positioned in the sealing cavity, the conducting pad is also electrically connected with an external structure through the through hole, the influence of the external environment is small, the stability of the device is good, and the pressure sensor can be used for monitoring the pressure in liquid or severe environment.

Description

Back hole lead wire type pressure sensor

Technical Field

The utility model relates to a micro-electromechanical system and pressure sensor field especially relate to a back of body hole pin formula pressure sensor.

Background

With the development of mems technology, the fabrication of pressure sensors has become a more mature technology. Pressure sensors can be classified into piezoresistive type, capacitive type, piezoelectric type and the like, wherein the piezoresistive pressure sensors are applied to various fields of aviation, navigation, petrochemical industry, power machinery, biomedical engineering, meteorology, geology, seismic survey and the like due to the advantages of small volume, high sensitivity, good linearity and the like.

A common fabrication method for piezoresistive pressure sensors is to fabricate the piezoresistance and the electrode on the upper surface of the sensitive membrane. The sensor prepared by the method has a packaging mode that the front side of the sensitive film senses pressure, the electrodes of the sensor chip are connected with the electrodes of the supporting structure (tube shell) through metal flexible wires, and the packaging needs the metal flexible wires to be isolated from a measured medium, so that the packaging volume is large. The other package is back pressure sensing and does not need to be isolated from a measured medium, but the piezoresistance, the electrode and the metal flexible wire of the sensor are exposed to the external environment, the metal flexible wire is easy to break under the strong vibration condition, and meanwhile, the device is not corrosion-resistant and has poor stability. There is also a way of packaging using TSV technology, i.e. filling the vias with metal to wire, which typically results in poor temperature characteristics of the sensor.

SUMMERY OF THE UTILITY MODEL

The utility model aims to solve the technical problem that a back of body hole pin formula pressure sensor is provided, it can realize no routing paster encapsulation, has reduced pressure sensor's encapsulation size, and device stability is good, can be used to the monitoring of pressure in liquid or the adverse circumstances.

In order to solve the above problem, the utility model provides a back of body hole pin formula pressure sensor, it includes: the device layer is internally provided with a plurality of piezoresistors and a plurality of conductive pads, and the conductive pads are electrically connected with the piezoresistors; the supporting layer is bonded with the device layer and is provided with a groove and a plurality of through holes penetrating through the supporting layer, the groove and the device layer form a sealed cavity, the piezoresistors are arranged corresponding to the sealed cavity, and the conducting pads are arranged corresponding to the through holes; and a plurality of electrodes arranged on the unbonded surface of the supporting layer, wherein the electrodes extend along the side wall of the through hole and are electrically connected with the conductive pad.

Optionally, the back-hole wire pressure sensor further comprises an insulating layer disposed between the electrode and the support layer.

Optionally, the back-hole lead type pressure sensor further includes a conductive transition layer disposed on the surface of the conductive pad, and the electrode is electrically connected to the conductive pad through the conductive transition layer.

Optionally, the back-hole lead type pressure sensor further includes a solder mask layer covering the electrode and exposing a solder joint of the electrode to be electrically connected with an external structure.

Optionally, the solder resist layer fills the through holes, or the solder resist layer extends along the surface of the electrode.

Optionally, the back-hole lead type pressure sensor further comprises a plurality of conductive bumps disposed on the electrode for electrically connecting the electrode with an external structure.

The utility model has the advantages that the pressure sensor is prepared by using the through hole lead technology, the packaging without routing and pasting is realized, and the packaging size of the pressure sensor is reduced; meanwhile, the pressure resistance of the pressure sensor is positioned in the sealing cavity, the conducting pad is also electrically connected with an external structure through the through hole, the influence of the external environment is small, the stability of the device is good, and the pressure sensor can be used for monitoring the pressure in liquid or severe environment.

Drawings

Fig. 1 is a schematic step diagram of a first embodiment of a method for manufacturing a back-hole lead-type pressure sensor according to the present invention;

fig. 2A to fig. 2H are process flow diagrams of a first embodiment of a method for manufacturing a back-hole lead-type pressure sensor according to the present invention;

FIGS. 3A-3D are process flow diagrams of forming a device substrate in the first embodiment;

fig. 4 is a process flow chart of forming a solder resist layer in a second embodiment of the method for manufacturing a back-hole lead-type pressure sensor of the present invention;

fig. 5A to 5D are process flow charts of forming electrodes in a third embodiment of the method for manufacturing a back-hole lead-type pressure sensor according to the present invention;

FIG. 6 is a schematic diagram of a first embodiment of a back-hole wire-lead pressure sensor;

FIG. 7 is a schematic diagram of a second embodiment of a back-hole wire-lead pressure sensor;

fig. 8 is a schematic structural diagram of a third embodiment of a back-hole wire-lead pressure sensor.

Detailed Description

The following describes in detail a specific embodiment of the back-hole lead type pressure sensor according to the present invention with reference to the accompanying drawings.

Fig. 1 is a schematic step diagram of a first embodiment of a method for manufacturing a back-hole lead-type pressure sensor according to the present invention. Referring to fig. 1, the preparation method includes the following steps: step S10, providing a device substrate, wherein a first surface of the device substrate is provided with a plurality of piezoresistors and a plurality of conductive pads, and the conductive pads are electrically connected to the piezoresistors; step S11, providing a supporting substrate, wherein the supporting substrate has a first surface and a second surface opposite to each other, the first surface of the supporting substrate has a groove, and a plurality of through holes penetrate through the supporting substrate from the first surface to the second surface; step S12, bonding the device substrate and the supporting substrate by using the first surface of the device substrate and the first surface of the supporting substrate as bonding surfaces, wherein the groove and the first surface of the device substrate form a sealed cavity, the piezoresistance corresponds to the sealed cavity, the through hole corresponds to the conductive pad, and the through hole exposes the conductive pad; step S13, forming a plurality of electrodes on the second surface of the supporting substrate, wherein the electrodes extend along the sidewalls of the through holes and are electrically connected to the conductive pads.

Fig. 2A to fig. 2H are process flow diagrams of a first embodiment of a method for manufacturing a back-hole lead-type pressure sensor according to the present invention.

Referring to step S10 and fig. 2A, a device substrate 200 is provided, wherein a plurality of piezoresistors 201 and a plurality of conductive pads 202 are disposed on a first surface 200A of the device substrate 200, and the conductive pads 202 are electrically connected to the piezoresistors 201.

In this embodiment, the method of forming the device substrate 200 includes the steps of:

referring to fig. 3A, a first substrate 300 is provided, the first substrate 300 has a first surface 300A, and a first insulating layer 301 covers the first surface 300A of the first substrate 300. The first substrate 300 includes, but is not limited to, a single crystal silicon or an SOI wafer. If the first substrate 300 is an SOI silicon wafer, the thickness of the upper silicon layer of the SOI wafer needs to just meet the thickness requirement of the sensitive film. The first insulating layer 301 may be formed through a thermal oxidation process, which may reduce channeling of ion implantation in a subsequent process of forming piezoresistance.

Referring to fig. 3B, a plurality of piezoresistors 201 and a plurality of thick boron wires 302 electrically connected to the piezoresistors 201 are formed on the first surface 300A of the first substrate 300, wherein the piezoresistors 201 are light boron piezoresistors. In this step, the light boron piezoresistor 302 and the thick boron conductive wire 302 can be fabricated by photolithography and ion implantation processes. The piezoresistance 201 is a strain piezoresistance formed by light boron diffusion, and the concentrated boron conducting wire 302 is a concentrated boron ohmic contact region formed by injecting concentrated boron. In this embodiment, four piezoresistors 201 (two piezoresistors 201 are shown in the figure) are connected by a dense boron wire 302 to form a Wheatstone bridge. In other embodiments of the present invention, eight piezoresistors 201 can be used.

Referring to fig. 3C, the first insulating layer 301 is patterned to form a plurality of openings 301A on the first insulating layer 301, wherein the openings 301A expose the surface of the boron-rich wires 302. In this step, the opening 301A may be formed by using a photolithography and etching process.

Referring to fig. 3D, a plurality of conductive pads 202 are formed at the openings 301A, and the conductive pads 202 are electrically connected to the dense boron wires 302, thereby forming the device substrate 200. In this step, the conductive pad 202 is made of metal, and may be formed by sputtering or deposition, photolithography and etching, wet etching or dry etching. In other embodiments, the conductive pad 202 may be polysilicon, which may be formed by a doping process.

Alternatively, in other embodiments of the present invention, a passivation layer (not shown) may be formed after the conductive pad 202 is formed, and the conductive pad is exposed to the passivation layer. In this step, a passivation layer may be deposited, and then the conductive pad may be exposed by photolithography and etching processes. The passivation layer may be used to protect the conductive pad 202 and the passivation layer may serve as a bonding layer for subsequent bonding. In this embodiment, the passivation layer is not formed.

Referring to step S11 and fig. 2B, a supporting substrate 210 is provided, in which the supporting substrate 210 has a first surface 210A and a second surface 210B disposed opposite to each other. The support substrate 210 includes, but is not limited to, a silicon substrate, a glass substrate, and the like. In this embodiment, the supporting substrate 210 is a silicon wafer with a thickness of 400 microns, and in other embodiments of the present invention, the thickness of the supporting substrate 210 may not be limited to 400 microns.

The first surface 210A of the support substrate 210 has a recess 211. In this step, the recess 211 may be formed on the first surface 210A of the supporting substrate 210 by using a photolithography and etching process. It is understood that the recess 211 does not extend through the support substrate 210. The shape of the recess 211 includes, but is not limited to, a rectangle, a circle, or a polygon.

A plurality of vias 212 extend through the support substrate 210 from the first surface 210A to the second surface 210B. In this embodiment, the through hole 212 may be formed by performing photolithography and etching processes on the second surface 210B of the supporting substrate 210. Further, the through holes 212 are located outside the groove 211, that is, a plurality of through holes 212 are disposed around the groove 211. The number of vias 212 may correspond to the number of conductive pads 202. The shape of the through hole 212 includes, but is not limited to, a rectangle, a circle, or a polygon.

Optionally, the present embodiment further includes a step of forming a second insulating layer 213. Referring to fig. 2C, a second insulating layer 213 is formed, wherein the second insulating layer 213 covers the first surface 210A of the supporting substrate 210, the second surface 210B of the supporting substrate 210, the inner surface of the recess 211, and the sidewall of the through hole 212. In this step, the second insulating layer 213 may be formed using a thermal oxidation or LPCVD process. The second insulating layer 213 functions to insulate the support substrate 210 from a subsequently formed electrode. It is understood that if the supporting substrate 210 is a non-insulating substrate, the second insulating layer needs to be formed; if the support substrate 210 is an insulating substrate, the second insulating layer may not be formed. Specifically, in the present embodiment, the supporting substrate 210 is a silicon substrate, and the second insulating layer 213 needs to be formed to insulate the electrode from the supporting substrate 210; in another embodiment of the present invention, the support substrate is a glass substrate, and the second insulating layer may not be formed since the glass substrate itself has an insulating property.

Referring to step S12 and fig. 2D, the device substrate 200 and the supporting substrate 210 are bonded by using the first surface 200A of the device substrate 200 and the first surface 210A of the supporting substrate 210 as bonding surfaces. In this embodiment, the device substrate 200 and the supporting substrate 210 are bonded with the upper surface of the first insulating layer 301 and the upper surface of the second insulating layer 213 as bonding surfaces.

In this step, the bonding process of the device substrate 200 and the support substrate 210 includes, but is not limited to, low temperature Si-Si fusion bonding, high temperature Si-Si fusion bonding, and Si-Glass anodic bonding. Specifically, in the present embodiment, the conductive pad 202 is made of aluminum metal, and the bonding process of the device substrate 200 and the support substrate 210 is a low-temperature Si — Si fusion bonding, wherein the bonding temperature does not exceed the melting point 660 ℃ of the conductive pad 202; in another embodiment of the present invention, the conductive pad 202 is polysilicon, and the bonding process between the device substrate 200 and the support substrate 210 is high temperature Si-Si fusion bonding, wherein the bonding temperature does not exceed the melting point 1410 ℃ of the conductive pad 202; in another embodiment of the present invention, the conductive pad 202 is polysilicon, the supporting substrate 210 is a Glass substrate, and the bonding process between the device substrate 200 and the supporting substrate 210 is Si-Glass anodic bonding.

After the device substrate 200 is bonded to the supporting substrate 210, the recess 211 forms a sealed cavity 220 with the first surface 200A of the device substrate 200. In this embodiment, the groove 211 and the upper surface of the first insulating layer 301 form the sealed cavity 220. The pressure resistance 201 corresponds to the sealed cavity 220, that is, the pressure resistance 201 is located in the projection range of the sealed cavity 220. The via 212 corresponds to the conductive pad 202, and the via 212 exposes the conductive pad 202, i.e., the conductive pad 202 is visible from the direction of the second surface 210B of the support substrate 210.

Optionally, before the bonding step, a step of aligning the device substrate 200 with the supporting substrate 210 is further included. This step is performed to ensure that the piezoresistor 201 corresponds to the sealed cavity 220, and the through hole 212 corresponds to the conductive pad 202. Optionally, a step of polishing the surface of the device substrate 200 is included before the bonding step. In this embodiment, since the bonding surface of the device substrate 200 is the surface of the first insulating layer 301, the first insulating layer 301 on the surface of the device substrate 200 is polished before the bonding step is performed, so that the flatness thereof meets the bonding requirement.

Alternatively, referring to fig. 2E, in the present embodiment, after the bonding step is completed, the device substrate 200 is thinned and polished from a surface of the device substrate 200 opposite to the first surface 200A. The thickness of the device substrate 200 may be reduced to several microns after the thinning and polishing processes are completed. If the device substrate 200 is an SOI (silicon on insulator) sheet, thinning is firstly carried out until the thickness is close to the SiO in the middle of the SOI sheet₂Wet method in layeringEtching off SiO₂And obtaining the top layer Si film.

Referring to step S13 and fig. 2F, a plurality of electrodes 230 are formed on the second surface 210B of the supporting substrate 210, wherein the electrodes 230 extend along the sidewalls of the vias 212 and are electrically connected to the conductive pads 202. In this embodiment, the specific steps of forming the electrode 230 are: first, an electrode layer (not shown) is formed on the second surface 210B of the support substrate 210, and the electrode layer covers the second surface 210B of the support substrate 210, the sidewalls of the through hole 212 and the conductive pad 202; next, the electrode layer is patterned to form a plurality of electrodes 230, wherein the electrode layer may be patterned to form the electrodes 230 by using photolithography and etching.

In this step, the electrode 230 extends along the sidewall of the via 212, rather than filling the via 212. If the electrode 230 fills the through hole 212, the temperature characteristic of the sensor may be deteriorated. In this embodiment, the second insulating layer 213 is disposed between the electrode 230 and the supporting substrate 210.

Alternatively, referring to fig. 2G, after the step of forming the electrode 230, the preparation method further includes the steps of: forming a solder mask layer 240, wherein the solder mask layer 240 covers the electrode 230 and exposes a solder joint 230A of the electrode 230, which is required to be electrically connected with an external structure. In this embodiment, the solder mask is an organic oligomer that fills the vias 212 to improve the performance of the sensor. In a second embodiment of the present invention, referring to fig. 4, the solder mask layer 240 is made of inorganic material such as silicon nitride, silicon oxide, silicon oxynitride, etc. and extends along the surface of the electrode 230, i.e. the solder mask layer 240 covers the electrode 230 in the form of a thin film.

Optionally, referring to fig. 2H, a conductive bump 250 is formed at the solder point 230A of the electrode 230, and the conductive bump 250 is used to electrically connect the electrode 230 with an external structure. In this embodiment, a ball-mounting reflow is performed on the solder joint 230A to form the conductive bump 250. The conductive bump 250 may be electrically connected to an external printed circuit board or the like.

In the first embodiment, the electrode 230 is formed after the bonding step, and in the third embodiment, the step of forming the electrode includes a step performed before the bonding step and a step performed after the bonding step. The concrete description is as follows:

referring to fig. 5A, after the structure diagram shown in fig. 2C, an electrode layer 500 is formed, wherein the electrode layer 500 covers the second surface 210B of the supporting substrate 210 and the sidewall of the through hole 212. The material of the electrode layer 500 is polysilicon, which may be formed by an LPCVD process.

Further, in an actual process, the electrode layer 500 also covers the first surface 210A of the supporting substrate 210 and the inner side walls of the groove 211, and in this step, the electrode layer 500 on the first surface 210A of the supporting substrate 210 and the inner side walls of the groove 211 may be removed by an etching process, and the electrode layer 500 covering the second surface 210B of the supporting substrate 210 and the side walls of the through hole 212 may be remained. Referring to fig. 5B, the device substrate 200 and the supporting substrate 210 are bonded by using the upper surface of the first insulating layer 301 and the upper surface of the second insulating layer 213 as bonding surfaces. In the step, the bonding process is high-temperature Si-Si fusion bonding, and the temperature is not more than 1410 ℃ of the melting point of the polycrystalline silicon.

Referring to fig. 5C, the electrode layer 500 is patterned to form a plurality of initial electrodes 501. In this step, a photolithography and etching process may be used to remove a portion of the electrode layer 500 on the first surface 210A of the supporting substrate 210, so as to form the initial electrode 501. The initial electrode 501 covers the sidewalls of the via 212 and a portion of the second surface 210B of the support substrate 210.

Referring to fig. 5D, a conductive transition layer 502 is formed on the surface of the conductive pad 202, i.e., the conductive transition layer 502 is formed at the bottom of the via 212. The material of the conductive transition layer 502 includes, but is not limited to, a metal material. The conductive transition layer 502 electrically connects the conductive pad 202 with the initial electrode 501, i.e., the initial electrode 501 and the conductive transition layer 502 together form an electrode 510. After the electrode 510 is formed, the subsequent steps are the same as those of the first embodiment, and are not described again.

In the third embodiment, the conductive pad 202 and the initial electrode 502 are made of polysilicon, which has poor electrical connection performance and poor contact if they are directly electrically connected, whereas in the present embodiment, the conductive transition layer 502 forms ohmic contact with both the conductive pad 202 and the initial electrode 502, which can enhance the electrical connection performance between the conductive pad 202 and the initial electrode 502.

The utility model also provides a back hole pin type pressure sensor's that adopts foretell preparation method preparation concrete implementation mode.

Fig. 6 is a schematic structural diagram of a first embodiment of a back-hole wire-lead pressure sensor. Referring to fig. 6, the back-hole lead type pressure sensor includes a device layer 600, a supporting layer 610 and a plurality of electrodes 620.

A plurality of piezoresistors 601 and a plurality of conductive pads 602 are disposed in the device layer 600, and the conductive pads 602 are electrically connected to the piezoresistors 601. In this embodiment, the piezoresistors 601 are light boron piezoresistors, and the light boron piezoresistors are electrically connected to the conductive pad 602 through a thick boron conductive wire 603. The device layer 600 includes a first substrate 604 and a first insulating layer 605 disposed on the first substrate 604, the piezoresistive layer 601 being disposed within the first substrate 604. The first insulating layer 605 has a plurality of openings (not shown in the drawings), and the conductive pad 602 is disposed in the openings, i.e., the conductive pad 602 is exposed outside the first insulating layer 605.

The support layer 610 is bonded to the device layer 600. The support layer 610 has a groove 611 and a plurality of through holes 612 penetrating the support layer 610. The recess 611 and the device layer 600 form a sealed cavity 630, and the piezoresistive layer 601 is disposed corresponding to the sealed cavity 630. The conductive pad 602 is disposed corresponding to the through hole 612, i.e., the through hole 612 exposes the conductive pad 602.

The electrode 620 is disposed on the unbonded surface of the support layer 610, and the electrode 620 extends along the sidewall of the through hole 612 and is electrically connected to the conductive pad 602. The electrode 620 extends along the sidewall of the via 612, rather than filling the via 612. If the electrode 620 fills the through hole 612, the temperature characteristics of the back-hole wire type pressure sensor may be deteriorated.

In this embodiment, the back-hole lead type pressure sensor further includes a second insulating layer 640, and the second insulating layer 640 is disposed between the electrode 620 and the support layer 610. Further, the second insulating layer 640 is not only disposed between the electrode 620 and the support layer 610, but also covers the entire surface of the support layer 610, the inner sidewalls of the groove 611, and the sidewalls of the through hole 612.

Further, the back hole lead type pressure sensor further comprises a solder mask layer 650, wherein the solder mask layer 650 covers the electrode 620 and exposes a welding spot 620A of the electrode 620, which is required to be electrically connected with an external structure. In this embodiment, the solder mask 650 fills the through hole 612 to improve the performance of the sensor. In a second embodiment of the present invention, referring to fig. 7, the solder mask 650 is made of inorganic material such as silicon nitride, silicon oxide, silicon oxynitride, etc. and extends along the surface of the electrode 620, i.e. the solder mask 650 covers the electrode 620 in the form of a thin film.

Further, in the present embodiment, the back-hole wire pressure sensor further includes a plurality of conductive bumps 660, and the conductive bumps 660 are disposed on the pads 620A of the electrode 620 and are used for electrically connecting the electrode 620 with an external structure.

Fig. 8 is a schematic structural diagram of a third embodiment of the back-hole lead-type pressure sensor according to the present invention. Referring to fig. 8, the third embodiment is different from the first embodiment in that the back-hole lead type pressure sensor further includes a conductive transition layer 800. The conductive transition layer 800 is disposed on the surface of the conductive pad 602, and the electrode 620 is electrically connected to the conductive pad 602 through the conductive transition layer 800. In the present embodiment, the conductive pad 602 and the electrode 620 are polysilicon, and the conductive transition layer 800 is metal. The electrode 620 does not extend to the conducting pad 602, but is connected to the conducting pad 602 through the conducting transition layer 800, so as to further improve the connection performance between the conducting pad 602 and the electrode 620.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the present invention, and these improvements and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A back-hole lead-type pressure sensor, comprising:

the device layer is internally provided with a plurality of piezoresistors and a plurality of conductive pads, and the conductive pads are electrically connected with the piezoresistors;

the supporting layer is bonded with the device layer and is provided with a groove and a plurality of through holes penetrating through the supporting layer, the groove and the device layer form a sealed cavity, the piezoresistors are arranged corresponding to the sealed cavity, and the conducting pads are arranged corresponding to the through holes;

and a plurality of electrodes arranged on the unbonded surface of the supporting layer, wherein the electrodes extend along the side wall of the through hole and are electrically connected with the conductive pad.

2. The back-hole-lead pressure sensor of claim 1, further comprising an insulating layer disposed between the electrode and the support layer.

3. The back-hole lead pressure sensor of claim 1, further comprising a conductive transition layer disposed on a surface of the conductive pad, wherein the electrode is electrically connected to the conductive pad through the conductive transition layer.

4. The back-hole wire pressure sensor according to any one of claims 1 to 3, further comprising a solder mask covering the electrode and exposing a pad of the electrode to be electrically connected to an external structure.

5. The hole-back lead pressure sensor of claim 4, wherein the solder resist layer fills the through-hole or extends along the surface of the electrode.

6. The back-hole-lead pressure sensor as claimed in any one of claims 1-3, further comprising a plurality of conductive bumps disposed on the electrodes for electrically connecting the electrodes to an external structure.