CN102903726B - The wafer-level packaging method of imageing sensor - Google Patents

Abstract

The invention provides a wafer-level packaging method of an image sensor. The packaging method comprises the following steps: a. forming a filter film on a glass substrate; b. cutting the glass substrate to obtain separate filter glass sheets, wherein the glass substrate or the filter glass sheets are detected to determine whether there is a defect therein; c. bonding a filter glass with defects less than a predetermined number on the photosensitive surface of the image sensor wafer; d. cutting the image sensor wafer to obtain separated image sensor chips.

Description

Wafer level packaging method for image sensor

technical field

The present invention relates to the technical field of semiconductors, and more particularly, to a wafer-level packaging method for an image sensor.

Background technique

An image sensor is a sensor that senses external light and converts it into an electrical signal. Image sensors are typically chip-fabricated using semiconductor manufacturing processes. After the image sensor chip is manufactured, a series of packaging processes are performed on the image sensor chip to form a packaged image sensor for use in various electronic devices such as digital cameras and digital video cameras.

FIG. 1 shows a packaging structure of an image sensor. As shown in FIG. 1 , the package structure includes: an image sensor chip 11 , a package glass 12 , a filter glass 13 , an optical lens 14 and a bracket 15 . Wherein, the packaging glass 12 is supported on the side of the photosensitive surface of the image sensor chip 11 by the supporting side wall 16 to protect the photosensitive area 17 thereunder. The filter glass 13 and the optical lens 14 are supported above the encapsulation glass 12 through the support 15, so as to perform corresponding optical processing on the light before the light is imaged. Wherein, according to different constituent materials, the filter film on the filter glass 13 can filter light of different wavelengths, such as infrared light, so as to improve the imaging quality of the image sensor chip 11 .

However, the additional filter glass 13 will increase the thickness of the image sensor packaging structure. Especially in the case of today's increasingly miniaturized and portable electronic equipment, this requires the packaged image sensor to be small in size, especially the overall height of the packaging structure can be as small as possible, so as to reduce the electronic equipment integrated with the structure. overall thickness.

In addition, the process yield of the image sensor added with the filter glass 13 is low, which increases its manufacturing cost.

Contents of the invention

Therefore, there is a need for a packaging method of an image sensor that can reduce the volume of the packaging structure of the image sensor and has a lower cost.

The inventors of the present invention found that the filter film of the filter glass used in the traditional image sensor is made by multiple times of physical vapor deposition. Unavoidably, physical vapor deposition will introduce impurity particles into the filter film, thereby creating defects in it, and multiple physical vapor deposition will further amplify such defects. Defects on the filter glass can affect the imaging of the image sensor chip. If the number of defects is too large, the packaged image sensor cannot be used, which reduces the yield of the packaging process and increases the manufacturing cost.

In order to better solve one or more of the above problems, in one aspect of the present invention, a wafer-level packaging method for an image sensor is provided, comprising the following steps: a. forming a filter film on a glass substrate; b. cutting the glass substrate to obtain separate filter glass sheets, wherein the glass substrate or the filter glass sheet is inspected to determine whether there is a defect; c. bonding on the photosensitive surface of the image sensor wafer a filter glass sheet having fewer than a predetermined number of defects; d. dicing said image sensor wafer to obtain separate image sensor chips.

In the above packaging method, the filter glass or glass substrate will be inspected before bonding to the image sensor wafer, so as to remove the filter glass with too many defects in advance, so that it will not meet the requirements due to bonding. The loss of the image sensor chip caused by the filter glass. Therefore, the above packaging method can effectively improve the yield of the packaging process and reduce the manufacturing cost. In addition, in this packaging method, since the photosensitive area of the image sensor is directly protected by the filter glass with the filter film, the packaging glass is no longer needed, which greatly reduces the height of the packaged image sensor, thereby reducing the The volume of the image sensor package structure is increased.

In one embodiment, the step a includes: forming the filter film by physical vapor deposition.

In one embodiment, the step a further includes: alternately depositing multiple layers of titanium oxide and silicon oxide on the glass substrate by means of physical vapor deposition to form the filter film.

In one embodiment, after the step b, the method further includes: cleaning the filter glass.

In one embodiment, the step b includes: scanning the glass substrate or the filter glass to determine defects therein.

In one embodiment, the step of determining the defect further includes: comparing the scanned glass substrate image or filter glass image with a reference image to determine the defect.

In one embodiment, after the step of determining the defect, it further includes: marking the filter glass sheets with not less than a predetermined number of defects.

In one embodiment, the step c includes: making a support side wall on the photosensitive surface side of the image sensor wafer; bonding the filter glass to the support side wall and an adhesive The photosensitive side of the image sensor wafer.

In one embodiment, before the step d, further comprising: connecting the output pins of the image sensor wafer to the pads on the back side of the image sensor wafer.

The foregoing has presented the features of the present disclosure in a generalized rather than broad sense. Additional features of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. Those skilled in the art should also understand that these equivalent structures do not depart from the spirit and scope of the present invention described in the appended claims.

Description of drawings

For a more complete understanding of the present disclosure, together with its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, in which:

Fig. 1 shows the packaging structure of a traditional image sensor;

FIG. 2 shows the flow of a wafer-level packaging method 100 for an image sensor according to an embodiment of the present invention;

3 to 9 show schematic cross-sectional views of an example of the packaging method 100 in FIG. 2 ;

10 to 12 illustrate another optional output pin connection mode of the packaging method 100 .

Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated. The drawings are drawn to clearly illustrate aspects of the embodiments of the present disclosure and are not necessarily drawn to scale. To more clearly illustrate certain embodiments, a reference number may be followed by a letter indicating variations of the same structure, material, or process step.

detailed description

The making and using of the embodiments are discussed in detail below. It should be understood, however, that the specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.

FIG. 2 shows the flow of a wafer-level packaging method 100 for an image sensor according to an embodiment of the present invention.

As shown in FIG. 2, the packaging method 100 includes: performing step S102, forming a filter film on a glass substrate; performing step S104, cutting the glass substrate to obtain separate filter glass sheets, wherein the glass substrate or filter glass The sheet is detected to determine whether there is a defect therein; step S106 is performed, and a filter glass sheet having a defect less than a predetermined number is bonded on the photosensitive surface of the image sensor wafer; step S108 is performed, and the image sensor wafer is cut to obtain separated image sensors chip.

It can be seen that due to the addition of the step S104 of detecting defects, the filter glass with too many defects will not be bonded to the image sensor wafer, thus will not cause unnecessary loss of image sensor chips. Therefore, the above packaging method can effectively improve the yield of the packaging process and reduce the manufacturing cost. In addition, in this packaging method, since the filter glass with the filter film is directly bonded on the photosensitive area of the image sensor, the packaging glass is no longer needed, which greatly reduces the overall height of the packaged image sensor. and volume.

3 to 9 show schematic cross-sectional views of an example of using the packaging method 100 of FIG. 2 . Next, the packaging method of the present invention will be described in detail with reference to FIG. 2 and FIG. 3 to FIG. 9 .

As shown in FIG. 3 , an image sensor wafer 201 is provided, and a plurality of image sensors 203 are formed in the image sensor wafer 201, and dicing lines (not shown) are also formed between the plurality of image sensors 203, so as to Different image sensors 203 are isolated. Each image sensor 203 includes a photosensitive array for sensing external light, which are commonly distributed on one side of the image sensor wafer 201 , that is, the photosensitive surface 205 . Generally, each image sensor 203 also includes a signal processing circuit (not shown in the figure), and the signal processing circuit is distributed around the photosensitive array and adjacent to the scribe line. In practical applications, a dielectric layer and an interconnection layer (not shown) in the dielectric layer are also formed on the photosensitive surface 205 of the image sensor, so as to lead out the circuit elements formed in the image sensor, wherein the interconnection Layer also includes output pin 207 .

A glass substrate 209 is also provided, which may have the same or different dimensions as the image sensor wafer 201 . Next, a filter film 211 is formed on the glass substrate 209 . In some examples, the filter film 211 is a film for filtering infrared light. Correspondingly, multiple layers of titanium oxide and silicon oxide may be alternately deposited on the glass substrate 209 by means of physical vapor deposition to form the filter film 211 . The formed filter film 211 has a laminated structure of multiple layers alternated with each other. The physical vapor deposition method includes but is not limited to evaporation coating, sputtering coating or ion coating, and so on. It can be understood that, in some other examples, required thin layer materials can also be formed on the glass substrate 209 in other suitable ways to form the filter film 211 .

In addition, it can be seen from FIG. 3 that in the process of forming the filter film 211, due to the mixing of impurity particles or the instability of the coating process, etc., some positions in the formed filter film 211 have defects 213, which for example show To have a thickness or transmittance etc. significantly different from the surrounding area. The defect 213 can affect the imaging of the photosensitive array of the image sensor 203 . Different defects 213 may have different sizes. Therefore, it is necessary to inspect the glass substrate 209 formed with the filter film 211 to determine whether there is a defect therein. In some examples, optical inspection equipment may be used to scan glass substrate 209 to determine defects 213 thereon. For example, a camera with an optical lens can be used to scan the glass substrate 209 to generate an image reflecting the defect 213 of the glass substrate 209 (including the filter film 211 ), especially the position and size of the defect in the filter film 211 . Next, the scanned image is compared with the reference image to determine the location and size of the defect 213 . Alternatively, some image processing algorithms may be directly used to process the image generated by scanning to detect whether there is a defect 213 therein. Through this inspection step, the number, size and location of defects 213 on the glass substrate 209 can be determined. Since the size of the defect 213 has different effects on the light sensitivity of the image sensor, according to different application requirements, only points on the glass substrate 209 whose size (such as area, side length or diameter) exceeds a certain threshold can be defined as defects 213 .

As shown in FIG. 4 , in some examples, after the defects on the glass substrate 209 are determined, the step of cutting the glass substrate 209 is performed to divide the glass substrate 209 into a plurality of separate filter glass pieces. Wherein, the size of each filter glass basically matches the size of the photosensitive array on the image sensor wafer 201 . In other examples, the step of cutting the glass substrate 209 may also be performed first; and after the glass substrate 209 is divided into a plurality of separate filter glass pieces, the filter glass pieces are tested separately to determine whether There are defects 213, and the number, size, etc. of the defects 213 in each filter glass. On the other hand, in practical applications, it is also possible to mark the filter glass, for example, mark the filter glass with defects not less than a predetermined number, to indicate the number of defects, quality grades, etc. of the filter glass, and then Indicates whether it can be subsequently bonded to the image sensor.

Cutting the glass substrate 209 may adopt laser cutting or mechanical cutting, or other suitable cutting methods. For the cutting method that is easy to form cutting slag, such as mechanical cutting, the filter glass can be cleaned after the step of cutting the glass substrate 209, so as to remove the cutting slag attached to the filter glass, so as to avoid its influence on the filter glass. The quality of the light glass sheet.

After the separated filter glass pieces are obtained, it is necessary to bond the filter glass pieces with less than a predetermined number of bonding defects on the photosensitive surface of the image sensor wafer 201 . Wherein, a filter glass is bonded above each photosensitive array.

Specifically, as shown in FIG. 5 , a supporting side wall 217 may be fabricated on the side of the photosensitive surface of the image sensor wafer 201 . The supporting sidewall 217 is formed outside the photosensitive array, for example, to cover the position of the cutting line. In some examples, the supporting sidewall 217 may be formed by screen printing. In other examples, a layer of organic polymer material with photosensitive properties may also be coated on the image sensor wafer 201 first. For example, the organic polymer material has the characteristic of molecular adhesion and curing after being exposed to light. Next, photolithography is performed on a part of the coated organic polymer material to pattern the organic polymer material. In this way, a structure supporting the side wall 217 is formed outside the photosensitive array.

Afterwards, an adhesive (not shown) is coated on the supporting sidewall 217, so that the filter glass 215 is bonded to the photosensitive surface of the image sensor wafer 201 through the supporting sidewall 217 and the adhesive. side. In this way, the filter glass 215 carrying the filter film 211 is supported on the photosensitive array and does not directly contact with the photosensitive array. In the example shown in FIG. 6 , the side of the filter glass 215 with the filter film 211 is set away from the image sensor wafer 201 , and in other examples, the filter glass 215 has one side of the filter film 211 . The side may also be disposed close to the image sensor wafer 201 .

Optionally, after the filter glass 215 is bonded, the back surface opposite to the photosensitive surface of the image sensor wafer 201 can also be thinned, for example, the image sensor wafer 201 can be thinned to a predetermined thickness by a back grinding process. Below, for example below 200 microns.

Next, as shown in FIG. 7 , after bonding the filter glass 215 , the output pin 207 of the image sensor wafer 201 is further connected to the pad 221 on the back of the image sensor wafer 201 .

In the example shown in FIG. 7 , output pin 207 is connected to pad 221 through via 223 . For example, the bonding pad area of the image sensor wafer 201 may be etched from the backside of the image sensor wafer 201 to form the through hole 223 penetrating through the image sensor wafer 201 . Then, the through hole 223 is filled with a metal material, such as copper, so that the output pin 207 is electrically drawn out from the back surface of the image sensor wafer 201 through the metal material. Next, solder material, such as tin balls, is formed on the pad area to form the pad 221 on the pad area.

Next, as shown in FIG. 8 , the image sensor wafer 201 is diced to obtain separated image sensor chips 225 . The front side of the image sensor chip 225 is covered with the filter glass 215 , and the back side is also provided with soldering pads 221 .

Afterwards, as shown in FIG. 9 , the image sensor chip 225 can be further installed on the printed circuit board 227, and the optical lens 231 can be installed on the photosensitive surface side of the image sensor chip 225 through the bracket 229, thereby completing the camera module assembly.

In the embodiments shown in FIGS. 3 to 9 , the output pin 207 of the image sensor chip 225 is connected to the bonding pad 221 through the via 223 . In practical applications, the image sensor chip 225 may also be packaged in other suitable connection manners, so as to electrically lead out the output pin 207 thereof. Figures 10 to 12 show another alternative output pin connection.

As shown in FIG. 10 , after the filter glass 315 is bonded to the image sensor wafer 301 . Partial areas of the backside of the image sensor wafer 301 are etched until the interconnection layer is exposed, so as to form grooves 341 on the backside thereof. Generally, the etched area is the middle connection part of each photosensitive array in the image sensor wafer 301 , that is, the dicing line area to expose the output pin 307 therein, wherein the dicing plane is usually slightly inclined.

Then, as shown in FIG. 11 , an insulating layer (not shown in the figure) is deposited on the backside of the etched image sensor wafer 301 . The insulating layer can be formed, for example, by coating an organic material; or can be formed by depositing a dielectric material, such as silicon oxide. Afterwards, a metal material is deposited on the insulating layer to form the metal layer 343 , for example, copper or aluminum is deposited on the insulating layer by a physical vapor deposition process such as sputtering. The metal layer 343 also covers the sidewall and bottom of the groove 341 .

Subsequently, as shown in FIG. 12 , the metal layer is partially etched to form a plurality of conductive leads 345 . The conductive leads 345 respectively extend from the back of the image sensor wafer 301 to the photosensitive surface of the image sensor wafer 301 through the cutting surface of the groove 341, so as to lead each output pin 307 to a predetermined area on the back of the image sensor wafer 301. The predetermined area is used as a pad area for setting pads. Next, solder material, such as solder balls, is formed on the pad area to form the pad 321 on the pad area.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative and exemplary and not restrictive; the invention is not limited to the foregoing embodiments.

Other changes to the disclosed embodiments can be understood and effected by those of ordinary skill in the art, by studying the specification, the disclosure, the drawings and the appended claims. In the claims, the word "comprising" does not exclude other elements and steps, and the words "a", "an" do not exclude a plurality. In the actual application of the invention, one component may perform the functions of multiple technical features cited in the claims. Any reference signs in the claims should not be construed as limiting the scope.

Claims (8)

1. a wafer-level packaging method for imageing sensor, is characterized in that, comprises the steps:

A. filter coating is formed on the glass substrate;

B. cut described glass substrate to obtain the light-filtering glass be separated, wherein, described glass substrate or described light-filtering glass are detected to determine wherein whether have defect;

C. the light-filtering glass of predetermined quantity is less than at the photosurface bonding defect of imageing sensor wafer;

D. described imageing sensor wafer is cut to obtain the image sensor chip be separated;

Wherein, the size of each described light-filtering glass is mated with the size of the photosensitive array on described imageing sensor wafer;

Described step c also comprises:

Make in the photosurface side of described imageing sensor wafer and support side wall; By described support side wall and adhesive, described light-filtering glass is bonded to the photosurface side of described imageing sensor wafer, wherein, described light-filtering glass is supported on described photosensitive array, and described photosensitive array of getting along well directly contacts.

2. wafer-level packaging method according to claim 1, is characterized in that, described step a comprises: adopt physical vapour deposition (PVD) mode to form described filter coating.

3. wafer-level packaging method according to claim 2, is characterized in that, described step a comprises further: adopt physical vapour deposition (PVD) mode on described glass substrate alternately deposit multilayer titanium oxide and silica to form described filter coating.

4. wafer-level packaging method according to claim 1, is characterized in that, after described step b, described method also comprises: clean described light-filtering glass.

5. wafer-level packaging method according to claim 1, is characterized in that, described step b comprises:

Scan described glass substrate or described light-filtering glass to determine defect wherein.

6. wafer-level packaging method according to claim 5, is characterized in that, describedly determines that the step of defect comprises further: scanned glass substrate image or light-filtering glass image are compared to determine defect with reference to image.

7. wafer-level packaging method according to claim 5, is characterized in that, described determine the step of defect after, also comprise: marking of defects is no less than the light-filtering glass of predetermined quantity.

8. wafer-level packaging method according to claim 1, is characterized in that, before described steps d, also comprises:

The output pin of described imageing sensor wafer is connected to the pad of described imageing sensor wafer rear.