CN111261650A

CN111261650A - Method for manufacturing optical filter on image sensor wafer

Info

Publication number: CN111261650A
Application number: CN202010090144.6A
Authority: CN
Inventors: 范成至; 周正三
Original assignee: Egis Technology Inc
Current assignee: Egis Technology Inc
Priority date: 2019-09-23
Filing date: 2020-02-13
Publication date: 2020-06-09
Also published as: CN211184079U; CN211087275U; TWI715439B; TW202113665A; CN211555889U; TWM596974U; TW202114190A; CN110911434A; WO2021056961A1; TWM597018U; CN111163255A; CN111163254A; TW202114184A; WO2021056960A1; TWM596975U; CN211089753U; WO2021056950A1; TWM596898U; TW202113949A

Abstract

The invention provides a method for manufacturing a filter on an image sensor wafer, which comprises the following steps: providing an image sensor wafer, wherein the image sensor wafer comprises a plurality of sensing areas and non-sensing areas between and around the sensing areas; forming a patterned sacrificial layer on the non-sensing region; forming a filter layer on the whole surface, wherein a first part of the filter layer covers the patterned sacrificial layer, and a second part of the filter layer covers the sensing regions; and removing the patterned sacrificial layer. When the patterned sacrificial layer is removed, the first portion is also removed, and the remaining second portions form a plurality of filters respectively located on the sensing regions.

Description

Method for manufacturing optical filter on image sensor wafer

Technical Field

The present invention relates to a method for fabricating an optical assembly, and more particularly, to a method for fabricating a filter on an image sensor wafer.

Background

With the progress of the photoelectric technology, the image sensor has been widely used and replaced the traditional photosensitive film. The image sensor can be applied to the occasions of taking pictures generally, and can also be applied to the purposes of taking the biological characteristics (such as fingerprints, palm prints, pupils or vein prints and the like) of the user and further being used for identity recognition.

In order to solve the problem that the image sensor is prone to overexposure when used in outdoor sunlight, an infrared cut-off filter (infrared cut-off filter) is generally added to a module of the image sensor to block infrared light, so as to avoid overexposure. However, the addition of the infrared cut filter on the module is liable to make the thickness of the module too thick, which is not favorable for the miniaturization of the electronic device.

Disclosure of Invention

The invention aims at a method for manufacturing an optical filter on an image sensor wafer (wafer), an image sensing module with a thinner thickness can be manufactured by the method, and the problem of stress generated when an optical filter process (process) is integrated into a wafer process can be effectively solved.

An embodiment of the present invention provides a method for fabricating a filter on an image sensor wafer, including: providing an image sensor wafer, wherein the image sensor wafer comprises a plurality of sensing areas and non-sensing areas between and around the sensing areas; forming a patterned sacrificial layer on the non-sensing region; forming a filter layer on the whole surface, wherein a first part of the filter layer covers the patterned sacrificial layer, and a second part of the filter layer covers the sensing regions; and removing the patterned sacrificial layer. When the patterned sacrificial layer is removed, the first portion is also removed, and the remaining second portions form a plurality of filters respectively located on the sensing regions.

In the method for manufacturing the optical filter on the image sensor wafer in the embodiment of the invention, the filter layer is patterned by adopting the method for forming the patterned sacrificial layer in advance, so that when the whole surface of the filter layer is formed on the image sensor wafer, the height difference generated by the patterned sacrificial layer causes the filter layer to have discontinuous parts due to disconnection, and further, the stress generated on the wafer when the filter layer is formed is reduced. Therefore, the filter process can be integrated into the wafer process without generating stress problem. Therefore, the method for manufacturing the optical filter on the image sensor wafer can effectively reduce the thickness of the image sensing module manufactured at the rear end, solve the problem of stress generated when the optical filter process is integrated into the wafer process, and effectively improve the yield of the image sensor.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

Fig. 1 to 5 are schematic cross-sectional views illustrating a process of fabricating a filter on an image sensor wafer according to an embodiment of the invention.

Description of the reference numerals

100: an image sensor wafer;

110: a sensing region;

120: a non-sensing region;

122: a conductive pad;

200: patterning the sacrificial layer;

210: a photoresist layer;

212. 214: a moiety;

300: a filter layer;

310: a first portion;

320: a second portion.

Detailed Description

Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the description to refer to the same or like parts.

Fig. 1 to 5 are schematic cross-sectional views illustrating a process of fabricating a filter on an image sensor wafer according to an embodiment of the invention. Referring to fig. 1 to 5, the method for fabricating a filter on an image sensor wafer of the present embodiment includes the following steps. First, as shown in fig. 1, an image sensor wafer 100 is provided, wherein the image sensor wafer 100 includes a plurality of sensing regions 110 and non-sensing regions 120 between and around the sensing regions 110. In the embodiment, the image sensor chip 100 is, for example, a Complementary Metal Oxide Semiconductor (CMOS) image sensor Chip (CIS) chip, but the invention is not limited thereto. In other embodiments, the image sensor wafer 100 may also be a Charge Coupled Device (CCD) wafer. Each sensing region 110 is a photosensitive region for sensing an image in the image sensor, and includes a plurality of pixels arranged in an array for sensing an image, and when the process is completed, the sensing regions 110 may be separated into a plurality of image sensor chips (chips) by cutting the image sensor wafer 100. The non-sensing region 120 may include a plurality of conductive pads 122 or other peripheral circuits. In fig. 1, only two sensing regions 110 are illustrated, but in practice, one image sensor wafer 100 usually has a plurality (e.g., more than 3) of sensing regions 110 arranged in an array (e.g., a two-dimensional array) so as to cut out a plurality of image sensor chips at the completion of the process.

Next, referring to fig. 2 and fig. 3, in the present embodiment, a photoresist layer 210 is formed on the entire surface of the image sensor wafer 100, for example, the photoresist layer 210 is spin-coated on the image sensor wafer 100. Then, the photoresist layer 210 is subjected to a patterned exposure. For example, as shown in fig. 2, when the photoresist layer 210 is a negative photoresist material (although the present invention is not limited thereto), the portion 212 of the photoresist layer 210 on the non-sensing region 120 can be exposed, and the portion 214 of the photoresist layer 210 on the sensing region 110 can be unexposed by the mask 50. Next, the patterned and exposed photoresist layer 210 is developed to leave a portion 212 of the photoresist layer 210 on the non-sensing region 120, so as to form a patterned sacrificial layer 200, as shown in fig. 3.

Then, as shown in fig. 4, a filter layer 300 is formed on the entire surface, and the filter layer process may be sputtering (sputter) or other Physical Vapor Deposition (PVD), such that a first portion 310 of the filter layer 300 covers the patterned sacrificial layer 200, and a second portion 320 of the filter layer 300 covers the sensing region 110. In the present embodiment, the filter layer 300 is formed on the entire surface by, for example, sputtering the filter layer 300 on the patterned sacrificial layer 200 and the sensing regions 110. In the present embodiment, the filter layer 300 is a multilayer film, for example, a multilayer film that filters light by applying the principle of thin film interference. In addition, the filter layer 300 is, for example, an infrared light cut filter layer.

After that, as illustrated in fig. 5, the patterned sacrificial layer 200 is removed. When the patterned sacrificial layer 200 is removed, the first portion 310 is also removed, and the remaining second portions 320 form a plurality of filters respectively located on the sensing regions 110. Thus, the filter is fabricated on the image sensor wafer 100. In this embodiment, the filters are, for example, infrared light cut filters formed by the infrared light cut filter layer. In addition, in the present embodiment, the step of removing the patterned sacrificial layer 200 is to wash away the patterned sacrificial layer 200 by using a solvent, for example.

In the method for fabricating a filter on an image sensor wafer of the present embodiment, since the filter layer 300 is patterned by using the method for forming the patterned sacrificial layer 200 in advance, when the entire surface of the filter layer 300 is formed on the image sensor wafer 100, the filter layer 300 may be disconnected and discontinuous (for example, the first portion 310 and the second portion 320 are disconnected) due to a height difference generated by the patterned sacrificial layer 200, thereby reducing stress generated on the wafer when the filter layer 300 is formed. Therefore, the filter process can be integrated into the wafer process without generating stress problem. Therefore, the method for manufacturing the optical filter on the image sensor wafer according to the embodiment can effectively reduce the thickness of the image sensing module manufactured at the rear end (because the optical filter is integrated with the wafer), and can effectively improve the yield of the image sensor. The integrated structure of the optical filter and the image sensor chip cut out after the optical filter is integrated with the image sensor wafer 100 of the present embodiment can be used to assemble an optical fingerprint sensing module (for example, an in-screen fingerprint sensing module) or a general camera module.

In the present embodiment, the range of the formed filter can cover and is slightly larger than the range of the sensing region 110, so as to prevent the infrared light from obliquely entering the sensing region 110 from the edge of the filter. Therefore, when forming the patterned sacrificial layer 200, the edge of the patterned sacrificial layer 200 and the sensing region 110 may be kept at a suitable fine distance, so that the second portion 320 covering and slightly larger than the sensing region 110 can be formed in the step of fig. 4, and then the filter covering and slightly larger than the sensing region 110 is formed in the step of fig. 5. However, the invention is not limited thereto, and in other embodiments, the edge of the filter may be aligned with the edge of the sensing region 110.

In summary, in the method for fabricating the optical filter on the image sensor wafer according to the embodiments of the invention, since the filter layer is patterned by using the method for forming the patterned sacrificial layer in advance, when the entire filter layer is formed on the image sensor wafer, the height difference generated by the patterned sacrificial layer causes the filter layer to have discontinuous portions due to disconnection, thereby reducing the stress generated on the wafer when the filter layer is formed. Therefore, the filter process can be integrated into the wafer process without generating stress problem. Therefore, the method for manufacturing the optical filter on the image sensor wafer can effectively reduce the thickness of the image sensing module manufactured at the rear end, effectively solve the problem of stress generated when the optical filter process is integrated into the wafer process, and improve the yield of the image sensor.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a filter on an image sensor wafer, comprising:

providing an image sensor wafer, wherein the image sensor wafer comprises a plurality of sensing areas and non-sensing areas between and around the sensing areas;

forming a patterned sacrificial layer on the non-sensing region;

forming a filter layer on the whole surface, wherein a first part of the filter layer covers the patterned sacrificial layer, and a second part of the filter layer covers the sensing areas; and

and removing the patterned sacrificial layer, wherein when the patterned sacrificial layer is removed, the first part is also removed, and the remaining second parts form a plurality of optical filters respectively positioned on the plurality of sensing regions.

2. The method of claim 1, wherein the step of forming the patterned sacrificial layer on the non-sensing region comprises:

forming a photoresist layer on the whole surface of the image sensor wafer;

carrying out patterning exposure on the photoresist layer; and

and developing the patterned and exposed photoresist layer to leave a part of the photoresist layer on the non-sensing area so as to form the patterned sacrificial layer.

3. The method of claim 2, wherein removing the sacrificial patterned layer comprises washing away the sacrificial patterned layer with a solvent.

4. The method of claim 2, wherein forming the photoresist layer over the image sensor wafer comprises spin coating the photoresist layer on the image sensor wafer.

5. The method of claim 1, wherein the filter layer is a multilayer film.

6. The method of claim 1, wherein the plurality of filters are infrared cut filters.

7. The method of claim 1, wherein forming the filter layer over the entire surface of the wafer comprises sputtering the filter layer on the sacrificial patterned layer and the sensing regions.

8. The method as claimed in claim 1, wherein the non-sensing region comprises a plurality of conductive pads.