Method of forming dam for image sensor module

Abstract

A method for forming a dam for an image sensor module. The method comprises the following steps: providing cover glass; laminating the cover glass by using a dry film, wherein the dry film is a photoetching material; aligning an exposure mask to cover the dry film, wherein the exposure mask is parallel to the surface of the cover glass; exposing the exposure mask using ultraviolet light; developing the exposed dry film by a photolithographic process; and curing the dry film subjected to photoetching treatment by heating, wherein the cured dry film forms at least one dam attached to the cover glass.

Description

[0001] This divisional application is for the invention patent application with the application number 202011526274.6 and the invention title "Image Sensor Module and Method for Manufacturing a Dam of an Image Sensor Module" filed on December 22, 2020. Technical Field

[0002] The present invention relates to an image sensor module, and more particularly, to a dam of an image sensor module having a sawtooth pattern and an inclined surface on an inner wall and a method for manufacturing the dam. Background Art

[0003] Recently, cameras have been installed in smart phones, automobiles, medical devices, etc. With the development of technology, the resolution of cameras has increased while the size of cameras has significantly decreased. Cameras are generally manufactured by using (but not limited to) complementary metal oxide semiconductor (CMOS) image sensors. Incident light transmitted through a lens is focused on the image sensor to form an image of an object.

[0004] A camera includes an image sensor module. In the image sensor module, an image sensor is usually enclosed or surrounded by a dam, which serves as a spacer between the image sensor and a cover glass in the image sensor module. Some incident light may be reflected by the inner wall of the dam, causing an unwanted flash on the image detected by the image sensor.

[0005] Therefore, there is a need for an image sensor module that reduces or eliminates the flash on the detected image. Summary of the Invention

[0006] According to one aspect of the present invention, an image sensor module includes: an image sensor having a light sensing area; a cover glass for covering the light sensing area; a dam located between the image sensor and the cover glass, surrounding the light sensing area, having an outer wall and an inner wall, wherein a cross-section of the inner wall parallel to the surface of the light sensing area of the image sensor forms a sawtooth pattern.

[0007] According to another aspect of the present invention, a method for manufacturing a dam of an image sensor module includes: providing a cover glass; laminating a dry film on the cover glass, wherein the dry film is a photolithography material; aligning an exposure mask to cover the dry film, wherein the exposure mask is parallel to the surface of the cover glass; exposing the exposure mask using ultraviolet light; developing the exposed dry film by a photolithography process; curing the dry film subjected to the photolithography process by heating; wherein the cured dry film forms at least one dam attached to the cover glass. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Non - limiting and non - exclusive embodiments of the present invention are described with reference to the following figures, where like reference numerals refer to like components in all the various views unless otherwise specified.

[0009] In several views of the drawings, corresponding reference numerals indicate corresponding components. Those skilled in the art will appreciate that the elements in the figures are shown for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve the understanding of the various embodiments of the present invention.

[0010] Figure 1 An exemplary image sensor module is shown.

[0011] Figure 2 An exemplary cross - section of the dam of the image sensor module in the x - y plane is shown.

[0012] Figure 3 An exemplary cross - section of the dam of the image sensor module in the z - y plane is shown.

[0013] Figure 4 An exemplary cross - section of the dam of the image sensor module according to an embodiment of the present invention in the x - y plane is shown.

[0014] Figure 5 An exemplary cross - section of the dam of the image sensor module according to an embodiment of the present invention in the z - y plane is shown.

[0015] Figure 6 An exemplary image sensor module according to an embodiment of the present invention is shown.

[0016] Figure 7A The first step of a method for manufacturing a dam of an image sensor module according to an embodiment of the present invention is shown, i.e., providing and, if necessary, cleaning a cover glass by plasma.

[0017] Figure 7B The second step of the method according to an embodiment of the present invention is shown, i.e., laminating a dry film on the cover glass.

[0018] Figure 7C The third step of the method according to an embodiment of the present invention is shown, i.e., aligning an exposure mask to cover the dry film.

[0019] Figure 7D The fourth step of the method according to an embodiment of the present invention is shown, i.e., exposing the exposure mask to exposure ultraviolet (UV) light.

[0020] Figure 7EShows the fifth step of the method according to an embodiment of the present invention, i.e., developing the dry film by a lithography process.

[0021] Figure 7F Shows the sixth step of the method according to an embodiment of the present invention, i.e., curing the lithographically processed dry film by heating.

[0022] Figure 7G Shows the seventh step of the method according to an embodiment of the present invention, i.e., flipping the cover glass so that the dam is located below the cover glass.

[0023] Figure 7H Shows the eighth step of the method according to an embodiment of the present invention, i.e., setting the flipped cover glass including the dam attached to the cover glass on the image sensor.

[0024] [Description of Symbols]

[0025] 100, 600: Image sensor module;

[0026] 102, 602, 712: Image sensor;

[0027] 104, 604: Substrate;

[0028] 106, 606: Lead wire;

[0029] 108, 408, 508, 608, 706A: Dam;

[0030] 110, 610, 702: Cover glass;

[0031] 112, 612, 714: Light sensing area;

[0032] 114, 614: Solder ball;

[0033] 116, 616: Encapsulant;

[0034] 120: Incident light;

[0035] 130: Three-dimensional (3D) coordinate system x - y - z;

[0036] 132, 134, 720, 722: Surface;

[0037] 200, 300, 400, 500: Cross-section;

[0038] 202, 402, 502: Outer wall;

[0039] 204, 404, 504, 624, 716: Inner wall;

[0040] 226, 526, 626, 726: Wall;

[0041] 704: Plasma;

[0042] 706: Dry film;

[0043] 708: Exposure mask;

[0044] 710: Exposure ultraviolet (UV) light. Detailed implementation

[0045] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to those of ordinary skill in the art that practicing the present invention need not employ these specific details. In other instances, well-known materials or methods have not been described in detail to avoid obscuring the present invention.

[0046] Throughout this specification, reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" throughout this specification are not necessarily all referring to the same embodiment. Furthermore, in one or more embodiments, the particular features, structures, or characteristics may be combined in any suitable combination and / or sub-combination.

[0047] Figure 1 An exemplary image sensor module 100 is shown. The image sensor module 100 includes an image sensor 102 attached to a first side of a substrate 104. The image sensor 102 is wire-bonded to pads on the first side of the substrate 104 via wires 106. A dam 108 is disposed between the image sensor 102 and a cover glass 110, and the cover glass 110 encloses or surrounds a light-sensing area 112 of the image sensor 102. The cover glass 110 covers the light-sensing area 112. A plurality of solder balls 114 are attached to a second side of the substrate 104 opposite the first side for electrically coupling the image sensor 102 to outside the image sensor module 100. The image sensor 102 is electrically coupled to the solder balls 114 via wires 106. Optionally, an encapsulant 116 is disposed on the first side of the substrate 104 to cover the wires 106, the substrate 104, and a portion of the image sensor 102 outside the dam 108.

[0048] Incident light 120 transmitted through a lens (not shown in the figure) can reach the inner wall of the dam 108 and can be reflected toward the light-sensing area 112 of the image sensor 102, thereby causing a flash on the image detected by the image sensor 102. The resulting flash is undesirable and should be reduced or eliminated.

[0049] For clarity, in Figure 1A three dimensional (3D) coordinate system x-y-z 130 is shown. The shown Figure 1 plane of the paper is the plane z-y, which can be considered as a vertical plane. Shown on the plane of the paper which is the plane x-y Figure 2 . The plane x-y can be considered as a horizontal plane. In Figures 2 to 6 the 3D coordinate system x-y-z 130 is also shown in a suitable orientation. Figure 1 Shown are the surface 132 of the cover glass 110 and the surface 134 of the light sensing area 112 of the image sensor 102. The surface 132 and the surface 134 are parallel to the plane x-y or the horizontal plane and orthogonal to the plane z-y or the vertical plane.

[0050] Figure 2 Shown is an exemplary cross-section 200 of the dam 108 in the plane x-y. The cross-section 200 is parallel to the horizontal plane or the surface 132 of the cover glass 110 and the surface 134 of the light sensing area 112 of the image sensor 102 (see Figure 1 ). The dam 108 has an outer wall 202 and an inner wall 204. The incident light 120 can reach the inner wall 204 of the dam 108. It should be noted that Figure 2 shown is the projection of the incident light 120 on the plane x-y. The real incident light 120 does not pass through the wall 226 of the dam 108. The incident light 120 can be reflected by the inner wall 204 towards the light sensing area 112, thus causing a flash on the detected image.

[0051] Figure 3 Shown is an exemplary cross-section 300 of the dam 108 in the plane z-y, which is similar to Figure 1 . The cross-section 300 is parallel to the vertical plane or orthogonal to the surface 132 of the cover glass 110 and the surface 134 of the light sensing area 112 of the image sensor 102. The dam 108 has an outer wall 202 and an inner wall 204. The dam 108 is located between the image sensor 102 and the cover glass 110. The incident light 120 can reach the inner wall 204 of the dam 108. The incident light 120 can be reflected by the inner wall 204 towards the light sensing area 112 of the image sensor 102, thus causing a flash on the image detected by the image sensor 102.

[0052] Figure 4 Shown is an exemplary cross-section 400 of the dam 408 according to an embodiment of the present invention in the plane x-y. The cross-section 400 is parallel to the horizontal plane or the surface 132 of the cover glass 110 and the surface 134 of the light sensing area 112 of the image sensor 102 (see Figure 1 ). The dam 408 has an outer wall 402 and an inner wall 404. The cross-section 400 of the inner wall 404 forms a serrated pattern. The serrated pattern of the inner wall 404 can be in Figure 4As shown, and may be other serrated patterns. When the incident light 120 reaches the inner wall 404, the inner wall 404 with a serrated pattern may not reflect the incident light 120 towards the light sensing area 112, and thus will not cause a flash on the detected image. The inner wall 404 with a serrated pattern reduces or eliminates the incident light reflected towards the light sensing area 112. The dam 408 may or may not completely enclose the light sensing area 112.

[0053] Figure 5 An exemplary cross-section 500 of the dam 508 in the plane z-y according to an embodiment of the present invention is shown. The cross-section 500 is parallel to the vertical plane or orthogonal to the surface 132 of the cover glass 110 and the surface 134 of the light sensing area 112 of the image sensor 102. The dam 508 has an outer wall 502 and an inner wall 504. The cross-section 500 of the wall 526 of the dam 508 has a wider portion near the cover glass 110 and a narrower portion near the image sensor 102. Therefore, the outer wall 502 and the inner wall 504 have inclined and / or curved surfaces. The cross-section 500 of the inner wall 504 forms an inclined surface. The dam 508 is located between the image sensor 102 and the cover glass 110. When the incident light 120 reaches the inner wall 504, the inner wall 504 with inclined and / or curved surfaces may not reflect the incident light 120 towards the light sensing area 112 of the image sensor 102, and thus will not cause a flash on the image detected by the image sensor 102. The inner wall 504 with inclined and / or curved surfaces reduces or eliminates the incident light reflected towards the light sensing area of the image sensor 102.

[0054] The inner wall 504 may have an inclined surface, as seen from Figure 5 the cross-section 500 shown in the plane z-y or in the vertical plane orthogonal to the surface 132 of the cover glass 110 and the surface 134 of the light sensing area 112 of the image sensor 102, and may also have a serrated pattern, as seen from Figure 4 the cross-section 400 shown in the plane x-y or in the horizontal plane parallel to the surface 132 of the cover glass 110 and the surface 134 of the light sensing area 112 of the image sensor 102 (see Figure 1 ).

[0055] Figure 6An exemplary image sensor module 600 according to an embodiment of the present invention is shown. The image sensor module 600 includes an image sensor 602, which is attached to a first side of a substrate 604. The image sensor 602 is wire-bonded to pads on the first side of the substrate 604 through wires 606. A dam 608 is disposed between the image sensor 602 and a cover glass 610, and the cover glass 610 encloses or surrounds a light-sensing area 612 of the image sensor 602. For example, the dam 608 is directly located between the image sensor 602 and the cover glass 610. The cover glass 610 covers the light-sensing area 612. A plurality of solder balls 614 are attached to a second side of the substrate 604 opposite to the first side for electrically coupling the image sensor 602 to outside the image sensor module 600. The image sensor 602 is electrically coupled to the solder balls 614 through the wires 606. Optionally, an encapsulant 616 is disposed on the first side of the substrate 604 to cover the wires 606, the substrate 604, and a part of the image sensor 602 outside the dam 608. For example, the encapsulant 616 is black.

[0056] The dam 608 can be Figure 4 the dam 408 shown. The inner wall 624 is similar to the inner wall 404 having a sawtooth pattern Figure 4 to reduce or eliminate incident light (not shown in the figure) reflected toward the light-sensing area 612 of the image sensor 602. In addition, the inner wall 624 can also have inclined and / or curved surfaces like the inner wall 504 Figure 5 shown to further reduce or eliminate incident light reflected toward the light-sensing area 612 of the image sensor 602. Therefore, the dam 608 can be Figure 5 the dam 508 shown, having a wall 626 similar to the wall Figure 5 526 shown. The cross-section of the wall 626 of the dam 608 in the plane z-y has a wider portion near the cover glass 610 and a narrower portion near the image sensor 602. However, to further reduce or eliminate incident light reflected toward the light-sensing area 612 of the image sensor 602, the thickness of the dam 608 is less than 40 μm.

[0057] Figures 7A to 7G An exemplary method for manufacturing at least one dam (e.g., the dam 608) attached to a cover glass (e.g., the cover glass 610) according to an embodiment of the present invention is shown, and the method includes eight main steps. Figure 7A A first step is shown, in which a cover glass 702 is provided, and optionally, the cover glass 702 is cleaned by a plasma 704. The cover glass 702 can be a glass wafer. Figure 7B A second step is shown, in which the cover glass 702 is laminated with a dry film 706. The dry film 706 is a lithographic material. Figure 7CShows the third step, in which the exposure mask 708 is aligned to cover the dry film 706. The exposure mask 708 is parallel to the surface 720 of the cover glass 702.

[0058] Figure 7D Shows the fourth step, in which the exposure mask 708 is exposed to exposure ultraviolet (UV) light 710. Figure 7E Shows the fifth step, after removing the exposure mask 708, the dry film 706 is developed by a photolithography process. A pattern of the dry film 706 is formed corresponding to the pattern of the exposure mask 708. The formed pattern of the dry film 706 includes at least one pre-cured dam 706A. The dam 706A can be Figure 4 The shown dam 408, in which the inner wall of the dam has a serrated pattern. The dam 706A of the dry film 706 is formed, and the cross-section of the inner wall 716 of the dam 706A parallel to the surface 720 of the cover glass 702 forms a serrated pattern corresponding to the pattern of the exposure mask 708.

[0059] Figure 7F Shows the sixth step, in which the lithographically processed dry film 706 including the dam 706A is cured by heating. The cured dry film 706 forms at least one post-cured dam 706A attached to the cover glass 702. For simplicity, both the pre-cured and post-cured dams 706A are identified as the dam 706A. Heating causes the dry film of the dam 706A to overflow on the surface 720 of the cover glass 702. The cover glass 702 is located below the dam 706A. After the overflow cools, the cross-section of the wall 726 of the dam 706A orthogonal to the surface 720 of the cover glass 702 has a wider portion near the cover glass 702 and a narrower portion away from the cover glass 702 due to the overflow. Therefore, the cross-section of the inner wall 716 of the dam 706A orthogonal to the surface 720 of the cover glass 702 forms an inclined surface.

[0060] Figure 7G Shows the seventh step, in which the cover glass 702 is flipped so that the dam 706A is located below the cover glass 702. In this position, the upper portion of the wall 726 of the dam 706A is wider than the bottom portion of the wall 726 of the dam 706A. Figure 7H Shows the eighth step, in which the flipped cover glass 702 including the dam 706A attached to the cover glass 702 is disposed on the image sensor 712 including the light sensing region 714. The dam 706A surrounds the light sensing region 714. The surface 722 of the light sensing region 714 of the image sensor 712 is parallel to the surface 720 of the cover glass 702. A necessary adhesive can be applied between the dam 706A and the image sensor 712 to mount the dam 706A to the image sensor 712.

[0061] The cover glass 702, the dam 706A, and the image sensor 712 can be Figure 6A cover glass 610, a dam 608, and an image sensor 602 as shown. The dam 706A is made of a dry film 706. The cured dry film 706 forms at least one dam 706A attached to the cover glass 702. The image sensor 712 can be one of at least one image sensor on a substrate wafer.

[0062] Although the present invention has been described herein with reference to exemplary embodiments and the best mode for practicing the invention, it will be apparent to those of ordinary skill in the art that many modifications, improvements, and sub-combinations of various embodiments, as well as various changes and variations, can be made to the invention without departing from the spirit and scope of the invention.

[0063] The terms used in the following claims should not be construed as limiting the invention to the specific embodiments disclosed in the specification and claims. Rather, the scope should be determined entirely by the following claims, which are to be construed in accordance with established claim interpretation rules. The specification and the figures should accordingly be regarded as illustrative rather than restrictive.

Claims

1. A method for forming a dam for an image sensor module, comprising: Providing a cover glass; Laminating the cover glass with a dry film, wherein the dry film is a photolithography material; Aligning an exposure mask to cover the dry film, wherein the exposure mask is parallel to the surface of the cover glass, and wherein the exposure mask has a serrated pattern; Exposing the exposure mask using ultraviolet light; Developing the exposed dry film by a photolithography process; And Curing the dry film that has been subjected to photolithography by heating; Wherein the cured dry film forms at least one dam attached to the cover glass.

2. The method according to claim 1, further comprising plasma cleaning the cover glass before laminating the cover glass with the dry film.

3. The method according to claim 1, further comprising, after curing the dry film that has been subjected to photolithography: Flipping the cover glass; and Setting the flipped cover glass including the dam attached to the cover glass on an image sensor including a light sensing region, wherein the dam surrounds the light sensing region.

4. The method according to claim 3, further comprising applying an adhesive between the image sensor and the dam before setting the flipped cover glass including the dam attached to the cover glass on the image sensor to mount the dam to the image sensor.

5. The method according to claim 3, wherein the surface of the light sensing region of the image sensor is parallel to the surface of the cover glass.

6. The method according to claim 3, wherein the image sensor is one of at least one image sensor on a substrate wafer.

7. The method according to claim 1, wherein after developing the exposed dry film by a photolithography process, a pattern of the dry film is formed corresponding to the pattern of the exposure mask.

8. The method according to claim 1, wherein a cross-section of an inner wall of the formed dam that is parallel to the surface of the cover glass forms a serrated pattern corresponding to the pattern of the exposure mask.

9. The method according to claim 1, wherein heating to cure the dry film that has been subjected to photolithography causes the dry film to overflow on the surface of the cover glass, and after the overflow cools, a cross-section of an inner wall of the formed dam that is orthogonal to the surface of the cover glass forms an inclined surface.

10. The method according to claim 9, wherein the formed dam includes the inner wall, and the inner wall has the serrated pattern parallel to the surface of the cover glass and the inclined surface orthogonal to the surface of the cover glass.

11. The method according to claim 1, wherein heating to cure the dry film that has been subjected to photolithography causes the dry film to overflow on the surface of the cover glass, and after the overflow cools, a cross-section of an inner wall of the formed dam that is orthogonal to the surface of the cover glass has a wider portion closer to the cover glass and a narrower portion farther from the cover glass due to the overflow.

12. The method according to claim 11, wherein the formed dam includes the inner wall, the inner wall having the serrated pattern parallel to the surface of the cover glass and the cross-section orthogonal to the surface of the cover glass, the cross-section having a wider portion closer to the cover glass and a narrower portion farther from the cover glass.

13. The method according to claim 1, wherein the cover glass is a glass wafer.

14. The method according to claim 1, wherein heating for curing the photolithographically processed dry film causes overflow of the dry film on the surface of the cover glass, and after the overflow cools, the cross-section of the inner wall of the formed dam orthogonal to the surface of the cover glass forms a curved surface.

15. The method according to claim 14, wherein the formed dam includes the inner wall, the inner wall having the serrated pattern parallel to the surface of the cover glass and the curved surface orthogonal to the surface of the cover glass.

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