CN212934659U

CN212934659U - Packaging structure of integrated thermopile infrared detector

Info

Publication number: CN212934659U
Application number: CN202021380419.1U
Authority: CN
Inventors: 凌方舟; 刘尧; 金羊华; 蒋乐跃
Original assignee: Memsic Semiconductor Wuxi Co Ltd
Current assignee: Memsic Semiconductor Wuxi Co Ltd
Priority date: 2020-07-14
Filing date: 2020-07-14
Publication date: 2021-04-09
Anticipated expiration: 2030-07-14

Abstract

The utility model provides an integrated thermopile infrared detector's packaging structure, integrated thermopile infrared detector's packaging structure includes: the first wafer comprises a first substrate, a thermopile film, a metal pad and a first cavity, wherein the thermopile film and the metal pad are arranged on the front surface of the first substrate, and the first cavity is opposite to the thermopile film and extends to the thermopile film from the back surface of the first substrate; the second wafer is bonded with the first wafer and is positioned on the front surface of the first substrate; and the third wafer is bonded with the first wafer and is positioned on the back surface of the first substrate, and the third wafer comprises a second substrate and a second cavity which is arranged on the second substrate and is opposite to the thin film. Compared with the prior art, the utility model discloses very big reduction thermopile infrared sensor's manufacturing cost, provide production efficiency, reduced the device size.

Description

Packaging structure of integrated thermopile infrared detector

[ technical field ] A method for producing a semiconductor device

The utility model relates to a microelectronics packaging technology field especially relates to an integrated thermopile infrared detector's packaging structure.

[ background of the invention ]

Infrared detectors are one of the most critical elements in infrared systems. Thermopile infrared detectors were a non-refrigerated type of infrared detector that was developed earlier. At present, a TO (TO heads) metal tube shell packaging method is generally adopted for the thermopile infrared detector, and each thermopile infrared sensor needs an independent TO packaging base and an independent TO packaging cap, so that the material cost of packaging materials is greatly increased, and the packaging efficiency is reduced. Compared with surface mounting devices, the device has larger volume, and the application range of the device is limited.

Therefore, it is necessary to provide a technical solution to overcome the above problems.

[ Utility model ] content

An object of the present invention is to provide a package structure of an integrated thermopile infrared detector, which employs a wafer level package method to reduce the device size.

According to an aspect of the utility model, the utility model provides an integrated thermopile infrared detector's packaging structure, it includes: the first wafer comprises a first substrate, a thermopile film, a metal pad and a first cavity, wherein the thermopile film and the metal pad are arranged on the front surface of the first substrate, and the first cavity is opposite to the thermopile film and extends to the thermopile film from the back surface of the first substrate; the second wafer is bonded with the first wafer and is positioned on the front surface of the first substrate; and the third wafer is bonded with the first wafer and is positioned on the back surface of the first substrate, and the third wafer comprises a second substrate and a second cavity which is arranged on the second substrate and is opposite to the thin film.

Further, the packaging structure of the integrated thermopile infrared detector further comprises: and the metal wire is led out from the metal bonding pad and redistributed to the surface, far away from the first wafer, of the third wafer.

Further, the thermopile thin film comprises a thermopile functional layer and a supporting layer; the material of the second wafer is glass, silicon or other organic or inorganic materials that can have sufficient transparency in the infrared wavelength range.

Further, an infrared filtering coating is arranged on one surface, away from the first wafer, of the second wafer; and a reflective coating is arranged on one surface of the third wafer, which is far away from the second wafer, or a reflective coating is arranged at the bottom of the second cavity.

Furthermore, the metal wire is led out from the metal bonding pad in the following manner: performing sidewall lead or through hole lead through the third wafer; and a getter is arranged in the first cavity and/or the second cavity.

Further, the thickness of the thermopile thin film is 2-10 microns; the depth of the second cavity is 50-800 microns.

Compared with the prior art, the utility model provides an integrated thermopile infrared detector's packaging structure includes first wafer, second wafer and third wafer, and its method that adopts wafer level encapsulation has avoided the process of TO metal tube shell encapsulation, very big reduction thermopile infrared sensor's manufacturing cost, provide production efficiency, reduced the device size. The reduced cost and reduced device size also provide the user with ease of use and increased range of applications.

[ description of the drawings ]

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without inventive labor. Wherein:

fig. 1 is a schematic longitudinal sectional view of a package structure of an integrated thermopile infrared detector in one embodiment of the present invention;

fig. 2 is a schematic longitudinal sectional view of a package structure of an integrated thermopile infrared detector in another embodiment of the present invention;

fig. 3 is a schematic flow chart illustrating a method for packaging a package structure of an integrated thermopile infrared detector according to an embodiment of the present invention;

fig. 4-10 are longitudinal sectional views of the structure corresponding to the steps shown in fig. 3 according to an embodiment of the present invention.

[ detailed description ] embodiments

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention is described in detail with reference to the accompanying drawings and the detailed description.

Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with at least one implementation of the invention is included. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Unless otherwise specified, the terms connected, and connected as used herein mean electrically connected, directly or indirectly.

Fig. 1 is a schematic longitudinal sectional view of a package structure of an integrated thermopile infrared detector according to an embodiment of the present invention. The package structure of the integrated thermopile infrared detector shown in fig. 1 includes a first wafer 110, a second wafer 120, and a third wafer 130. After wafer level packaging, a wafer dicing step is performed to form a plurality of mutually independent package structures, i.e., independent chips. The first wafer, the second wafer and the third wafer are three independent wafers from the perspective before wafer dicing, i.e., from the wafer level perspective, and the first wafer, the second wafer and the third wafer can be understood as chips of each wafer from the perspective after wafer dicing, i.e., from the chip level perspective.

A thermopile infrared sensor is disposed (or fabricated) on the first wafer 110, and includes a first substrate 111, a thermopile thin film 112, a metal pad 113, and a first cavity 114, wherein the thermopile thin film (or thermopile thin film structure) 112 and the metal pad 113 are disposed on the front surface of the first substrate 111, and the first cavity 114 is opposite to the thermopile thin film 112 and extends from the back surface of the first substrate 111 to the thermopile thin film 112. In one embodiment, the thickness of the thermopile thin film 112 is 2-10 microns; the thermopile film 112 includes a thermopile functional layer (not shown) and a support layer (not shown). In the particular embodiment shown in fig. 1, the metal pad 113 is located outside the thermopile film 112.

A thermopile infrared sensor may be fabricated on the first wafer 110 typically using a MEMS (Micro-Electro-Mechanical System) or CMOS (Complementary Metal Oxide Semiconductor) process. Silicon dioxide, silicon nitride, polysilicon, metal or organic materials can be used as the support layer; then, forming a thermopile by utilizing the N-doped or P-doped polycrystalline silicon and aluminum or the N-doped and P-doped polycrystalline silicon; other materials such as single or multiple layers of metal (aluminum, polysilicon, etc.) may also be utilized and fabricated as an assist pattern (not shown) to increase absorptivity; a first cavity 114 extending from the back surface of the first substrate 111 can be formed on the first substrate 111 by back etching (DRIE, KOH etching), and only the thermopile thin film 112 consisting of the thermopile functional layer and the support layer with a thickness of only 2-10 μm is left.

The second wafer 120 is bonded to the front side of the first substrate 111 of the first wafer 110 (or the front side of the first wafer 110). The second wafer 120 serves as an infrared filter and may be selected from glass, silicon, or other organic or inorganic materials that are sufficiently transparent in the infrared wavelength range. An infrared filter coating 140 is disposed (or covered) on the front surface of the second wafer 120 (or the surface of the second wafer 120 away from the first wafer 110), and the infrared filter coating 140 has an anti-reflection coating, and a wavelength cut-off coating.

The third wafer 130 is structurally bonded to the back side of the first substrate 111 of the first wafer 110 (or the back side of the first wafer 110). The third wafer 130 includes a second substrate 131, and a second cavity 132 disposed on the second substrate 131 and opposite to the thermopile thin film 112.

The third wafer 130 acts as the bottom plate of the back cavity. The third wafer 130 desirably includes a plurality of second cavities 132 corresponding to the first wafer 110. The second cavity 132 has a depth of 50-800 microns and acts as a thermal barrier. The third wafer 130 may be covered with a reflective coating 150. The reflective coating 150 may cover the front surface of the third wafer 130 (or the surface of the third wafer 130 close to the first wafer 110), for example, the reflective coating 150 is located at the bottom of the second cavity 132, as shown in fig. 1, and the reflective coating 150 may also be coated on the back surface of the third wafer 130 (or the surface of the third wafer 130 far from the first wafer 110), as shown in fig. 2. The reflective coating 150 may be comprised of a metal such as gold, aluminum, silver, or other materials that are capable of reflecting a substantial portion of infrared radiation. The reflective coating 150 may be full-surface or arranged in a patterned manner.

If the first cavity 114 and/or the second cavity 132 are vacuum cavities, getters, including aluminum 16, vitriol, etc., may be introduced into the first cavity 114 and/or the second cavity 132. If the substrate 111 of the first wafer 110 and the substrate 131 of the third wafer 130 are silicon materials, the first cavity 114 and the second cavity 132 may be obtained by one or more etching processes. In the bonding of the second wafer 120 and the first wafer 110, and the bonding of the third wafer 130 and the first wafer 110, the bonding may be performed by using a bonding machine under the condition of controllable gas content. Most desirably vacuum, other stable and thermally conductive gases (e.g., nitrogen, krypton, xenon) may be used. The bonding material can be metal, alloy, glass, epoxy glue and other choices. Anodic, fusion bonding is also an optional process.

In the embodiment shown in fig. 1, the back surface of the bonded third wafer 130 (or the surface of the third wafer 130 away from the second wafer 120) is provided with a metal wire 160, which is led out from the metal pad 113 and redistributed to the back surface of the third wafer 130. The metal pad 113 is led out from the third wafer 130 by punching a hole in the third wafer 130, and is implemented by a through hole process.

A solder ball 170 is disposed on the back side of the third wafer 130. Both the metal pads 113 and the solder balls 170 may serve as signal contacts. In another embodiment, the solder balls 170 may be replaced with metal pads.

Fig. 2 is a schematic longitudinal sectional view of a package structure of an integrated thermopile infrared detector according to another embodiment of the present invention, which has a structure substantially the same as that of the embodiment shown in fig. 1, and also includes a first wafer 110, a second wafer 120, and a third wafer 130; it differs from the embodiment shown in fig. 1 in that: the metal pad 113 has different leading-out modes of the metal wire 160, and the leading-out mode of the pad is realized by a slope metal rewiring process (or a side wall lead process); the reflective coating 150 is coated on the back side of the third wafer 130 (or the side of the third wafer 130 away from the second wafer 120).

Fig. 3 is a schematic flow chart illustrating a method for packaging a package structure of an integrated thermopile infrared detector according to an embodiment of the present invention; fig. 4-10 are longitudinal sectional views corresponding to the steps shown in fig. 3 according to an embodiment of the present invention. The packaging method of the packaging structure of the integrated thermopile infrared detector shown in FIG. 4 comprises the following steps.

Step 310, as shown in fig. 4 and 5, a first wafer 110 is provided, and a thermopile infrared sensor is disposed (or fabricated) on the first wafer 110. First, a thermopile film 112 and a metal pad 113 are fabricated on the front surface of a first substrate 111, as shown in fig. 4 in detail; then, a first cavity 114 extending from the back surface of the first substrate 111 is formed on the first substrate 111 by back surface etching (DRIE, KOH etching), and only the thermopile thin film 112 consisting of the thermopile functional layer and the support layer with a thickness of only 2-10 μm is left, i.e. the first cavity 114 is opposite to the thin film 112 and extends from the back surface of the first substrate 111 to the thermopile thin film 112, as shown in fig. 5.

Thermopile infrared sensors may be fabricated on the first wafer 110, typically using MEMS or CMOS processes. Silicon dioxide, silicon nitride, polysilicon, metal or organic materials may be used as a support layer (not shown); then, forming a thermopile by utilizing the N-doped or P-doped polycrystalline silicon and aluminum or the N-doped and P-doped polycrystalline silicon; other materials such as single or multiple layers of metal (aluminum, polysilicon, etc.) may also be utilized and fabricated as assist patterns (not shown) to increase absorption.

Step 320, as shown in fig. 6, a second wafer 120 is provided, and the second wafer 120 is bonded to the front surface of the first substrate 111 of the first wafer 110. The second wafer 120 serves as an infrared filter and may be selected from glass, silicon, or other organic or inorganic materials that are sufficiently transparent in the infrared wavelength range. An infrared filter coating 140 is disposed (or covered) on the front surface of the second wafer 120 (or the surface of the second wafer 120 away from the first wafer 110), and the infrared filter coating 140 has an anti-reflection coating, and a wavelength cut-off coating.

Step 330, as shown in fig. 7 and 8, providing a third wafer 130, bonding the third wafer 130 to the back surface of the first substrate 111 of the first wafer 110 (or the back surface of the first wafer 110), where the third wafer 130 includes a second substrate 131 and a second cavity 132 disposed on the second substrate 131 and opposite to the thermopile film 112.

The third wafer 130 acts as the bottom plate of the back cavity. The third wafer 130 desirably includes a plurality of second cavities 132 corresponding to the first wafer 110. The second cavity 132 has a depth of 50-800 microns and acts as a thermal barrier. The third wafer 130 may be covered with a reflective coating 150. The reflective coating 150 may cover the front surface of the third wafer 130 (or the surface of the third wafer 130 close to the first wafer 110), for example, the reflective coating 150 is located at the bottom of the second cavity 132, as shown in fig. 7, or the reflective coating 150 may cover the back surface of the third wafer 130 (or the surface of the third wafer 130 far from the first wafer 110), as shown in fig. 8. The reflective coating 150 may be comprised of a metal such as gold, aluminum, silver, or other materials that are capable of reflecting a substantial portion of infrared radiation. The reflective coating 150 may be full-surface or arranged in a patterned manner.

If the first cavity 114 and/or the second cavity 132 are vacuum cavities, getters including aluminum oxide 16, zinc oxide, etc. may be introduced into the first cavity 114 and/or the second cavity 132. If the substrate 111 of the first wafer 110 and the substrate 131 of the third wafer 130 are silicon materials, the first cavity 114 and the second cavity 132 may be obtained by one or more etching processes. In the bonding of the second wafer 120 and the first wafer 110, and the bonding of the third wafer 130 and the first wafer 110, the bonding may be performed by using a bonding machine under the condition of controllable gas content. Most desirably vacuum, other stable and thermally conductive gases (e.g., nitrogen, krypton, xenon) may be used. The bonding material can be metal, alloy, glass, epoxy glue and other choices. Anodic, fusion bonding is also an optional process.

In step 340, as shown in fig. 9 and fig. 10, a metal wire 160 is disposed on the back surface of the bonded third wafer 130 (or the surface of the third wafer 130 away from the second wafer 120), and is led out from the metal pad 113 and redistributed to the back surface of the third wafer 130. The metal pad 113 may be extracted by punching a hole in the third wafer 130, and the metal pad is extracted by a via process, as shown in fig. 9; the metal pad 113 leading-out manner can also be realized by a ramp metal rewiring process (or a sidewall wiring process), as shown in fig. 10.

In step 350, as shown in fig. 9 and 10, solder balls 170 are disposed on the back surface of the third wafer 130. Both the metal pads 113 and the solder balls 170 may serve as signal contacts. In another embodiment, the solder balls 170 may be replaced with metal pads.

To sum up, the utility model discloses an among integrated thermopile infrared detector's packaging structure and the packaging method thereof, integrated thermopile infrared detector's after the wafer is closed packaging structure includes first wafer 110, second wafer 120 and third wafer 130. In the first wafer 110, the thermopile film 112 and the metal pad 113 are disposed on the front surface of the first substrate 111, and the first cavity 114 is opposite to the thermopile film 112 and extends to the thermopile film 112 on the back surface of the first substrate 111; the second wafer 120 is bonded to the first wafer 110, and the second wafer 120 is located on the front surface of the first substrate 111; the third wafer 130 is bonded to the first wafer 110, and the third wafer 130 is located on the back surface of the first substrate 111, and the third wafer 130 includes a second substrate 131 and a second cavity 132 disposed on the second substrate 131 and opposite to the thermopile film 112. Thus, the utility model provides an integrated thermopile infrared detector's packaging structure can adopt the method of wafer level encapsulation, has avoided the process of TO metal tube shell encapsulation, very big reduction thermopile infrared sensor's manufacturing cost, provide production efficiency, reduced the device size. The reduced cost and reduced device size also provide the user with ease of use and increased range of applications.

In the present invention, the terms "connected", "connecting", and the like denote electrical connections, and, unless otherwise specified, may denote direct or indirect electrical connections.

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, but all equivalent modifications or changes made by those skilled in the art according to the present invention should be included in the protection scope of the claims.

Claims

1. A packaging structure of an integrated thermopile infrared detector is characterized by comprising:

the first wafer comprises a first substrate, a thermopile film, a metal pad and a first cavity, wherein the thermopile film and the metal pad are arranged on the front surface of the first substrate, and the first cavity is opposite to the thermopile film and extends to the thermopile film from the back surface of the first substrate;

the second wafer is bonded with the first wafer and is positioned on the front surface of the first substrate;

and the third wafer is bonded with the first wafer and is positioned on the back surface of the first substrate, and the third wafer comprises a second substrate and a second cavity which is arranged on the second substrate and is opposite to the thin film.

2. The package structure of an integrated thermopile infrared detector of claim 1, further comprising: and the metal wire is led out from the metal bonding pad and redistributed to the surface, far away from the first wafer, of the third wafer.

3. The package structure of integrated thermopile infrared detector according to claim 1,

the thermopile thin film comprises a thermopile functional layer and a supporting layer;

the material of the second wafer is glass, silicon or other organic or inorganic materials that can have sufficient transparency in the infrared wavelength range.

4. The package structure of integrated thermopile infrared detector according to claim 1,

an infrared filtering coating is arranged on one surface, far away from the first wafer, of the second wafer;

and a reflective coating is arranged on one surface of the third wafer, which is far away from the second wafer, or a reflective coating is arranged at the bottom of the second cavity.

5. The package structure of integrated thermopile infrared detector according to claim 2,

the metal wire is led out from the metal bonding pad in the following mode: performing sidewall lead or through hole lead through the third wafer;

and a getter is arranged in the first cavity and/or the second cavity.

6. The package structure of integrated thermopile infrared detector according to claim 1,

the thickness of the thermopile film is 2-10 micrometers;

the depth of the second cavity is 50-800 microns.