CN111668321A - Packaging structure and method of biometric fingerprint chip - Google Patents

Abstract

The invention discloses a packaging structure and a packaging method for a biometric fingerprint chip. The packaging structure includes: a fingerprint identification chip, the fingerprint identification chip has opposite front and back, and the front has a plurality of pixel points for collecting fingerprint information; A first light-transmitting layer formed on the front side of the fingerprint identification chip, a light-shielding groove is formed on the first light-transmitting layer, and the light-shielding groove encloses a plurality of light-transmitting areas, each of which corresponds to one of the pixels. point; a light-shielding layer covering at least the sidewall surface of the light-shielding groove. In this case, by setting a light-shielding layer around the pixel points, oblique light can be blocked and absorbed, and the interference of oblique light on image forming can be filtered; Low.

Description

Packaging structure and method of biometric fingerprint chip

technical field

The invention belongs to the technical field of semiconductors, and in particular relates to a biological fingerprint identification chip packaging structure and packaging method.

Background technique

With the continuous progress of science and technology, more and more electronic devices are widely used in people's daily life and work, which has brought great convenience to people's daily life and work, and has become an indispensable tool for people today. . With the continuous increase of functions of electronic devices, more and more important information is stored in electronic devices, and the authentication technology of electronic devices has become a main direction of research and development of electronic devices.

Due to the uniqueness and invariance of fingerprints, fingerprint identification technology has many advantages such as good security, high reliability and simple use. Therefore, fingerprint recognition technology has become the mainstream technology for authentication of various electronic devices.

At present, an optical fingerprint identification chip is one of the commonly used fingerprint identification chips in existing electronic devices. It collects the user's fingerprint information through a large number of photosensitive pixels (pixels) in the fingerprint identification area, and each photosensitive pixel is used as a detection. Specifically, when fingerprint recognition is performed, light is irradiated on the user's fingerprint surface and reflected to the photosensitive pixels through the fingerprint surface.

When the existing optical fingerprint identification chip is packaged, a transparent cover plate is generally directly set directly on the photosensitive side. However, since the transparent cover plate is completely transparent, crosstalk will occur between the sensing results of different photosensitive pixels, which will affect the accuracy of fingerprint recognition.

In order to solve this technical problem, Chinese patent application CN111192931A discloses a method for packaging a fingerprint identification chip, which fixes a cover plate with a through-hole structure on the side of the wafer facing the pixels to avoid crosstalk problems. The existing problems at least include: the use of a silicon cover plate as the light-shielding layer has a large thickness and high manufacturing cost.

SUMMARY OF THE INVENTION

An embodiment of the present invention provides a packaging structure and method for a fingerprint identification chip, which are used to solve the technical problems of large thickness and high manufacturing cost in the prior art, including:

A packaging structure of a biometric fingerprint chip, comprising:

Fingerprint identification chip, the fingerprint identification chip has opposite front and back, and the front has a plurality of pixel points for collecting fingerprint information;

A first light-transmitting layer formed on the front side of the fingerprint identification chip, a light-shielding groove is formed on the first light-transmitting layer, and the light-shielding groove encloses a plurality of light-transmitting areas, each of which corresponds to one of the pixels. point;

The light-shielding layer covers at least the sidewall surface of the light-shielding groove.

In one embodiment, the light-transmitting area is a transparent cylinder, or a cylindrical cavity. When it is a cylindrical cavity, the light-shielding layer is formed on the side wall of the cavity (the bottom surface is not laid so that the light can be directly directed to the pixel points). ).

In one embodiment, the light-shielding layer covers the bottom surface of the light-shielding groove.

In one embodiment, the light-shielding layer extends from the sidewall of the light-shielding groove to the top surface of the first light-transmitting layer.

In one embodiment, the light-shielding groove includes a plurality of annular grooves, and each of the pixel points corresponds to a bottom of an area enclosed by the grooves.

In another embodiment, the light-transmitting area is a cylindrical cavity, and the light-shielding layer is formed on the sidewall of the cavity (the bottom surface is not laid so that the light can be directly directed to the pixels).

In one embodiment, the material of the light shielding layer is black glue.

In one embodiment, it further includes a second light-transmitting layer covering the light-shielding groove and the light-transmitting area.

In one embodiment, it also includes a condensing lens formed on the surface of the second light-transmitting layer,

Each of the condenser lenses corresponds to one of the pixels respectively.

In one embodiment, the first light-transmitting layer and/or the second light-transmitting layer are selected from dry film, inorganic glass or organic glass.

In one embodiment, it further includes a filter formed between the front surface of the fingerprint identification chip and the first light-transmitting layer.

A packaging method for a biometric fingerprint chip, comprising:

A wafer is provided, the wafer has a plurality of fingerprint identification chips, the fingerprint identification chip has opposite front and back, and the front has a plurality of pixel points for collecting fingerprint information;

A first light-transmitting layer is made on the front side of the fingerprint identification chip;

A light-shielding groove is formed on the first light-transmitting layer, the light-shielding groove encloses a plurality of light-transmitting areas, and each of the light-transmitting areas corresponds to one of the pixel points;

A light-shielding layer is formed at least on the sidewall surface of the light-shielding groove;

Through a cutting process, the wafer is cut to form a plurality of single-chip packaging structures.

Compared with the prior art, in this case, the oblique light can be blocked and absorbed by arranging a light-shielding layer around the pixel points, and the interference of the oblique light on the image forming can be filtered; layer, the thickness is thin, and the production cost is low.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments described in this application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

1 is a cross-sectional view of a package structure in Embodiment 1 of the present application;

2 to 9 are schematic diagrams of intermediate structures formed by the packaging structure in Embodiment 1 of the present application.

Detailed ways

The present invention will be more fully understood from the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and for teaching one skilled in the art to vary in virtually any suitable detailed embodiment. The manner adopts the representative basis of the present invention.

This embodiment provides a package structure 10 . Referring to FIG. 1 , the package structure 10 includes a fingerprint identification chip 11 and a cover plate 12 .

The fingerprint identification chip 11 has a front side 111 and a back side 112 opposite to each other, and the front side has a plurality of pixel points 113 for collecting fingerprint information.

The cover plate 12 covers the front surface 111 of the fingerprint identification chip 11 . The front surface 111 includes a sensing area and a non-sensing area surrounding the sensing area. The pixel points 113 are provided in the sensing area; the non-sensing area is provided with pads (not shown) electrically connected to the pixel points 113, and the pads are used for electrical connection with external circuits.

In one embodiment, the cover plate 12 includes a filter layer 121 and a first light-transmitting layer 122 sequentially covering the front surface 111 of the fingerprint identification chip.

The filter layer 121 is used to filter out stray light outside the detection light band, so as to reduce the interference of stray light and improve the precision of fingerprint identification.

The filter layer 121 may only cover the upper portion corresponding to the pixel points 113 , or may cover the entire front surface 111 of the fingerprint identification chip 11 . However, in order to facilitate the fabrication of the first transparent layer 122 and ensure its flatness, the filter layer 121 preferably covers the entire front surface 111 of the fingerprint identification chip 11 .

In one embodiment, the filter layer 121 and the first light-transmitting layer 122 are bonded and fixed by a DAF film. The first transparent layer 122 and the front surface 111 of the fingerprint identification chip 11 are fixed by adhesive.

The first light-transmitting layer 122 covers the front surface 111 of the fingerprint identification chip 11 for protecting the front surface of the fingerprint identification chip 11 to be packaged. Since light needs to pass through the first light-transmitting layer 122 to reach the pixel points 113 , the first light-transmitting layer 122 has high light transmittance and is a light-transmitting material. Both surfaces of the first light-transmitting layer 122 are flat and smooth, and will not scatter or diffusely reflect incident light.

Specifically, the material of the first light-transmitting layer 122 may be dry film, inorganic glass, plexiglass or other light-transmitting materials with specific strength, and the transmittance needs to reach more than 92%.

In this embodiment, considering the optical properties and adhesive properties of the first light-transmitting layer 122 comprehensively, the thickness of the first light-transmitting layer 122 is preferably 5-20 μm.

In this case, the filter layer 121 is optional, and in one embodiment, the filter layer may not be provided.

In order to realize that the light received by the pixels 113 can only be direct light, to ensure the clarity of the image, and to filter the oblique light that interferes with the image forming, a light-shielding groove 123 is formed on the first light-transmitting layer 122, and the light-shielding groove 123 is surrounded by a plurality of light-transmitting grooves. Each of the light-transmitting regions 124 corresponds to one of the pixel points 113, and the sidewall surface of the light-shielding groove 123 is covered with a light-shielding layer 125 for shielding oblique light.

In the direction perpendicular to the front surface 111 , the projection of the light-transmitting area 124 on the front surface 111 at least partially overlaps the projection of the corresponding pixel point 113 on the front surface 111 . In order to ensure the accuracy of fingerprint recognition, the projection of the light-transmitting area 124 on the front side 111 can be set to completely cover the projection of the corresponding pixel points 113 on the front side 111 . Preferably, the projection of the light-transmitting area 124 on the front surface 111 can be set to completely coincide with the projection of the corresponding pixel points 113 on the front surface 111 .

In order to facilitate one-time molding of the light-shielding layer 125 and achieve a complete light-shielding effect, the light-shielding layer 125 is filled in the light-shielding groove 123 and covers the bottom thereof. In one embodiment, the light-shielding layer 125 may also extend from the sidewall of the light-shielding groove 123 to the top surface of the first light-transmitting layer 122

The light-shielding groove 123 includes a plurality of annular grooves, each annular groove respectively encloses a light-transmitting area 124 , each light-transmitting area 124 is composed of a transparent cylinder, and each pixel point 113 corresponds to at the bottom of one of the cylinders.

The material of the light-shielding layer 122 is a black light-shielding material, preferably BKL black glue.

The light-shielding groove 123 may penetrate the first light-transmitting layer 122 up and down, or may be recessed on one side surface (upper surface or lower surface) of the first light-transmitting layer 122 . When the lower surface (for penetration), the light-shielding layer needs to be pre-fabricated on the first light-transmitting layer, and then the first light-transmitting layer and the light-shielding layer are integrally fabricated on the front side of the chip.

In one aspect of this case, by arranging the light-shielding layer 125 around the pixel points, oblique light can be blocked and absorbed, and the interference of the oblique light on the image forming can be filtered; Thin and low cost.

In one embodiment, the fingerprint identification chip 11 is a capacitive fingerprint identification chip or an optical fingerprint identification chip.

If the fingerprint identification chip 11 is a capacitive fingerprint identification chip, when fingerprint identification is performed, the pixel point 113 detects the capacitance value and converts the capacitance value into an electrical signal. The external circuit can obtain fingerprint information according to the electrical signal, perform identity identification, and transmit light. The area 124 is used to expose the pixels, and the light shielding layer 125 has a lower dielectric constant, which can reduce the problem of crosstalk between adjacent pixels and improve the accuracy of fingerprint identification.

If the fingerprint identification chip 11 is an optical fingerprint identification chip, when performing fingerprint identification, the pixel 113 collects fingerprint information in a preset area opposite to the transparent area 124 through the corresponding transparent area 124 . Since each pixel point 113 collects the fingerprint information of its own relative collection area through the corresponding light-transmitting area 124, the mutual crosstalk between the preset areas corresponding to different pixel points is avoided, thereby avoiding the distortion of the fingerprint image, and further improving the fingerprint quality. recognition accuracy.

The shape of the light-transmitting area 124 may be circular, square or triangular. Specifically, the shape of the light-transmitting area 124 can be set as a circular cylinder with the same top and bottom, or a square cylinder with the same top and bottom, or a triangular cylinder with the same top and bottom, or other structures with the top and bottom The same polygonal cylinder.

It is easy to think that the shape of the light-transmitting area 124 can also be set as a circular cylinder with different top and bottom, or a square cylinder with different top and bottom, or a triangular cylinder with different top and bottom, or Other structures are polygonal cylinders whose tops are not the same as their bottoms.

In one embodiment, the light-shielding groove 123 and the light-transmitting area 124 are also covered with a second light-transmitting layer 126 for shielding the opening of the light-shielding groove 123 . When the light-shielding layer extends to the upper surface of the first light-transmitting layer 126, The second light-transmitting layer 126 can also press the light-shielding layer to avoid separation between the light-shielding layer and the surface of the first light-transmitting layer. Since light needs to pass through the second light-transmitting layer 126 to reach the pixels 113 , the second light-transmitting layer 126 has high light transmittance and is a light-transmitting material. Both surfaces of the second light-transmitting layer 126 are flat and smooth, and will not scatter or diffusely reflect incident light.

Specifically, the material of the second light-transmitting layer 126 may be dry film, inorganic glass, plexiglass or other light-transmitting materials with specific strength, and the transmittance needs to reach more than 92%.

In this embodiment, considering the optical properties and the adhesive properties of the second light-transmitting layer 126, the thickness of the second light-transmitting layer 126 is preferably 5-20 μm.

In one embodiment, the second transparent layer 126 and the first transparent layer 122 are fixed by adhesive.

A plurality of condensing lenses 127 are disposed on the side of the second light-transmitting layer 126 away from the front surface 111 of the fingerprint identification chip 11 . Pixel 113 surface.

In one embodiment, the condensing lens 127 can be fabricated by photolithography and baking molding. In another embodiment, the condensing lens 127 can also be formed on the surface of the second light-transmitting layer 126 by embossing.

Correspondingly, an embodiment of the present invention provides a packaging method for forming a packaging structure as shown in FIG. 1 . Please refer to FIG. 2 to FIG. 9 , which are schematic diagrams of intermediate structures formed during the packaging process of the packaging method according to the embodiment of the present invention.

Step s1 : Referring to FIGS. 2 and 3 , a wafer to be packaged 100 is provided, wherein FIG. 2 is a schematic top view of the wafer to be packaged 100 , and FIG. 3 is a cross-sectional view of FIG. 2 along A-A.

The wafer 100 to be packaged has a front side 111 and a back side 112 opposite to the front side 111 . The wafer 100 includes a plurality of fingerprint identification chips 11 arranged in an array. Each adjacent fingerprint identification chip 11 has a plurality of pixel points 13 for collecting fingerprint information. The pixel point 13 is located on the front side 111 . There is a cutting channel 120 between adjacent fingerprint identification chips 11 to facilitate cutting processing in the subsequent cutting process.

The first surface 111 includes a sensing area and a non-sensing area surrounding the sensing area. The pixel points 113 are arranged in the sensing area, and a pad (not shown in the figure) is set in the non-sensing area. The pad is electrically connected to the pixel point 113. for electrical connection with external circuits.

It should be noted that the cutting channel 120 between two adjacent fingerprint identification chips 11 is only a blank area reserved between the two fingerprint identification chips 11 for cutting, and the cutting channel 120 is connected to the fingerprints on both sides. There is no actual boundary line between the identification chips 11 .

Step s2 : referring to FIG. 4 , cover the filter layer 121 on the front surface 111 of the wafer 100 to be packaged. In this step, the filter layer 121 is fixed on the surface of the wafer 100 to be packaged by adhesive.

Step s3 : referring to FIG. 5 , cover the surface of the filter layer 121 with the first light-transmitting layer 122 .

Step s4: Referring to FIG. 6, using the photolithography technology of high-transmittance materials, photolithography of light-shielding grooves 123 is performed on the first light-transmitting layer 122. Corresponding to one pixel point 113 .

Step s5 : Referring to FIG. 7 , a light-shielding layer 125 is formed on the bottom surface and sidewalls of the light-shielding groove 123 , and the light-shielding layer 125 is made of an opaque or low light-transmitting black organic material, such as black glue. The black organic material is a photosensitive material, which can be patterned by a photolithography process. Specifically, the method for forming the light-shielding layer 125 includes: forming a black photosensitive organic material layer on the bottom surface, sidewalls and the top surface of the first light-transmitting layer of the light-shielding groove 123 by spin coating, spraying or sticking; The positive and negative development characteristics of the material, the black photosensitive organic material layer is exposed to the area where the light transmission window (light transmission area 124) is to be formed, or the area outside the window to be formed is exposed; finally, the black photosensitive organic material layer is baked. The hardened film is baked to enhance the mechanical strength of the black photosensitive organic material layer and the adhesion to the first light-transmitting layer. In some embodiments, the thickness of the black photosensitive organic material is 10 μm˜50 μm, preferably, it may be 15 μm, 20 μm, and the like.

Step s6 : Referring to FIG. 8 , cover the second light-transmitting layer 126 over the first light-transmitting layer 122 . In this step, the second light-transmitting layer 126 is fixed on the surface of the first light-transmitting layer 122 by adhesive.

Step s7 : Referring to FIG. 9 , a plurality of condensing lenses 127 are fabricated on the surface of the second light-transmitting layer 126 , and each condensing lens 127 corresponds to one pixel point 113 respectively.

Step s8 : dividing the wafer 100 , the filter layer 121 , the first light-transmitting layer 122 , and the second light-transmitting layer 126 by a cutting process, and cutting along the direction of the cutting channel 120 during cutting to form a plurality of fingerprints The package structure 10 of the chip 11 is identified. Cutting can be done with a slicing knife or laser cutting, and a slicing knife can be cut with a metal knife or a resin knife.

The entire packaging process may also include processes such as wafer thinning, pad fabrication, and wiring layer fabrication, which will not be repeated in this case.

In addition, after the wafer to be packaged is packaged, the chip package structure obtained by subsequent cutting can be connected to an external circuit through external bumps (not shown).

The aspects, embodiments, features, and examples of the present invention are to be considered in all respects illustrative and not intended to limit the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

The use of headings and sections in this application is not meant to limit the invention; each section is applicable to any aspect, embodiment or feature of the invention.

Throughout this application, where a composition is described as having, comprising or including particular components, or where a process is described as having, comprising or including particular process steps, it is contemplated that the compositions of the present teachings will also be substantially The above consists of or consists of the recited components, and the processes taught herein also consist essentially of, or consist of, the recited process steps.

In this application, where an element or component is referred to as being included in and/or selected from a list of recited elements or components, it is to be understood that the element or component can be any of the recited elements or components and The group may be selected from two or more of the recited elements or components. Furthermore, it should be understood that the elements and/or features of the compositions, apparatuses or methods described herein may be combined in various ways, whether expressly or implicitly herein, without departing from the spirit and scope of the present teachings. Instructions included.

The use of the terms "include, includes, including," "have, has, or having" should generally be understood to be open-ended and not limiting unless specifically stated otherwise.

The use of the singular herein includes the plural (and vice versa) unless specifically stated otherwise. Also, the singular forms "a (a, an)" and "the (the)" include the plural forms unless the context clearly dictates otherwise. Additionally, where the use of the term "about" precedes a magnitude, the teachings of the present invention also include the particular magnitude itself, unless specifically stated otherwise.

It should be understood that the order of the steps or the order in which the particular actions are performed is not critical so long as the present teachings remain operable. Furthermore, two or more steps or actions may be performed simultaneously.

It should be understood that the figures and descriptions of the present invention have been simplified to illustrate elements relevant to a clear understanding of the present invention, while other elements have been eliminated for clarity. However, one skilled in the art will recognize that these and other elements may be desirable. However, since such elements are well known in the art, and since they do not facilitate a better understanding of the present invention, no discussion of such elements is provided herein. It should be understood that the figures are presented for illustrative purposes and not as construction drawings. Omitted details and modifications or alternative embodiments are within the scope of those skilled in the art.

It will be appreciated that, in certain aspects of the invention, a single component may be replaced by a plurality of components and a plurality of components may be replaced by a single component to provide an element or structure or to perform a given function or functions. Except where such substitutions would not operate to practice specific embodiments of the invention, such substitutions are considered to be within the scope of the invention.

Although the present invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions and/or additions and the like may be made without departing from the spirit and scope of the invention Effects replace elements of the described embodiments. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is not intended herein to limit the invention to the particular embodiments disclosed for carrying out the invention, but it is intended that this invention include all embodiments falling within the scope of the appended claims. Furthermore, unless specifically stated, any use of the terms first, second, etc. does not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.

Claims (10)

1. a packaging structure of biometric fingerprint chip, is characterized in that, comprises: Fingerprint identification chip, the fingerprint identification chip has opposite front and back, and the front has a plurality of pixel points for collecting fingerprint information; A first light-transmitting layer formed on the front side of the fingerprint identification chip, a light-shielding groove is formed on the first light-transmitting layer, and the light-shielding groove encloses a plurality of light-transmitting areas, each of which corresponds to one of the pixels. point; The light-shielding layer covers at least the sidewall surface of the light-shielding groove. 2 . The packaging structure of the biometric fingerprint chip according to claim 1 , wherein the light shielding layer covers the bottom surface of the light shielding groove. 3 . 3 . The packaging structure of the biometric fingerprint chip according to claim 1 , wherein the light shielding layer extends from the sidewall of the light shielding groove to the top surface of the first light-transmitting layer. 4 . 4 . The packaging structure of the biometric fingerprint chip according to claim 1 , wherein the light-shielding groove comprises a plurality of annular grooves, and each pixel point corresponds to one of the grooves. 5 . into the bottom of the area. 5 . The packaging structure of the biometric fingerprint chip according to claim 1 , wherein the material of the light shielding layer is black glue. 6 . 6 . The packaging structure of the biometric fingerprint chip according to claim 1 , further comprising a second light-transmitting layer covering the light-shielding groove and the light-transmitting area. 7 . 7 . The packaging structure of the biometric fingerprint chip according to claim 6 , further comprising a condensing lens formed on the surface of the second light-transmitting layer, 8 . Each of the condenser lenses corresponds to one of the pixels respectively. 8 . The packaging structure of a biometric fingerprint chip according to claim 6 , wherein the first light-transmitting layer and/or the second light-transmitting layer are selected from dry film, inorganic glass or organic glass. 9 . 9 . The packaging structure of the biometric fingerprint chip according to claim 1 , further comprising a filter formed between the front surface of the fingerprint identification chip and the first light-transmitting layer. 10 . 10. A method for encapsulating a biometric fingerprint chip, comprising: A wafer is provided, the wafer has a plurality of fingerprint identification chips, the fingerprint identification chip has opposite front and back, and the front has a plurality of pixel points for collecting fingerprint information; A first light-transmitting layer is made on the front side of the fingerprint identification chip; A light-shielding groove is formed on the first light-transmitting layer, the light-shielding groove encloses a plurality of light-transmitting areas, and each of the light-transmitting areas corresponds to one of the pixel points; A light-shielding layer is formed at least on the sidewall surface of the light-shielding groove; Through a cutting process, the wafer is cut to form a plurality of single-chip packaging structures.

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