Method of forming a dam for an image sensor module

Abstract

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

Description

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

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

[0003] Recently, cameras have been installed in smartphones, cars, medical devices, and more. With technological advancements, camera resolution has increased while camera size has significantly decreased. Cameras are typically manufactured using (but not limited to) complementary metal-oxide-semiconductor (CMOS) image sensors. Incident light transmitted through a lens is focused onto the image sensor, thus forming an image of the object.

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

[0005] Therefore, it is necessary to reduce or eliminate flashes in the detected images from the image sensor module. 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 region; a cover glass for covering the light-sensing region; and a dam located between the image sensor and the cover glass, surrounding the light-sensing region, having an outer wall and an inner wall, wherein the cross-section of the inner wall parallel to the surface of the light-sensing region of the image sensor forms a sawtooth pattern.

[0007] According to another aspect of the present invention, a method for manufacturing a dam for an image sensor module includes: providing a cover glass; laminating the cover glass using a dry film, wherein the dry film is a photolithographic 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 using a photolithographic process; and curing the photolithographically treated dry film by heating; wherein the cured dry film forms at least one dam attached to the cover glass. Attached Figure Description

[0008] Non-limiting and non-exclusive embodiments of the invention are illustrated with reference to the following figures, wherein, unless otherwise specified, the same reference numerals refer to the same parts in all various views.

[0009] In the various views of the accompanying drawings, corresponding reference numerals indicate corresponding components. Those skilled in the art will understand 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 elements in the figures may be exaggerated relative to other elements to aid in understanding the various embodiments of the 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 plane xy is shown.

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

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

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

[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 for an image sensor module according to an embodiment of the present invention is to provide and, if necessary, clean the cover glass with plasma.

[0017] Figure 7B The second step of the method according to an embodiment of the present invention is shown, namely, laminating the coverslip with a dry film.

[0018] Figure 7C The third step of the method according to an embodiment of the present invention is shown, namely, aligning the 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, namely exposing the exposure mask to ultraviolet (UV) light.

[0020] Figure 7EThe fifth step of the method according to an embodiment of the present invention is shown, namely developing the dry film by photolithography.

[0021] Figure 7F The sixth step of the method according to an embodiment of the present invention is shown, namely, curing the photolithographically treated dry film by heating.

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

[0023] Figure 7H The eighth step of the method according to an embodiment of the present invention is shown, namely, setting a flipped cover glass, including a dam attached to the cover glass, onto the image sensor.

[0024] [Explanation of Symbols]

[0025] 100, 600: Image sensor modules;

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

[0027] 104, 604: Substrates;

[0028] 106, 606: Wires;

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

[0030] 110, 610, 702: Coverslips;

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

[0032] 114, 614: Solder balls;

[0033] 116, 616: Encapsulation body;

[0034] 120: Incident light;

[0035] 130: Three-dimensional (3D) coordinate system xyz;

[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 to ultraviolet (UV) light. Detailed Implementation

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

[0046] Throughout this specification, the terms "an embodiment" or "embodiment" refer to a specific feature, structure, or characteristic described in connection with at least one embodiment of the invention. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout this specification do not necessarily refer to the same embodiment. Furthermore, in one or more embodiments, the specific feature, structure, or characteristic can 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 a pad on the first side of the substrate 104 via a wire 106. A dam 108 is disposed between the image sensor 102 and a cover glass 110, which encloses or surrounds a light-sensing region 112 of the image sensor 102. The cover glass 110 covers the light-sensing region 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 outside the image sensor module 100. The image sensor 102 is electrically coupled to the solder balls 114 via wires 106. Optionally, an encapsulation 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), can reach the inner wall of the dam 108 and be reflected toward the light-sensing area 112 of the image sensor 102, thereby causing flashes in the image detected by the image sensor 102. The resulting flashes are undesirable and should be reduced or eliminated.

[0049] For clarity, Figure 1The diagram shows a three-dimensional (3D) coordinate system xyz 130. Figure 1 The paper plane is plane zy, which can be considered a perpendicular plane. It is shown on the paper plane xy. Figure 2 The xy plane can be considered a horizontal plane. Figures 2 to 6 The 3D coordinate system xyz 130 is also shown in an appropriate orientation. Figure 1 The surface 132 of the cover glass 110 and the surface 134 of the light-sensing area 112 of the image sensor 102 are shown. Surfaces 132 and 134 are parallel to the plane xy or the horizontal plane and orthogonal to the plane zy or the vertical plane.

[0050] Figure 2 An exemplary cross-section 200 of the retaining wall 108 in the plane xy is shown. 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 [reference]). Figure 1 The dam 108 has an outer wall 202 and an inner wall 204. Incident light 120 can reach the inner wall 204 of the dam 108. It should be noted that... Figure 2 The projection of incident light 120 onto the plane xy is shown. The actual 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 toward the light-sensing area 112, thereby causing a flash on the detected image.

[0051] Figure 3 This illustrates an exemplary cross-section 300 of the retaining dam 108 in the plane zy, which is consistent with... Figure 1 Similar. The cross-section 300 is parallel to 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. Incident light 120 can reach the inner wall 204 of the dam 108. The incident light 120 can be reflected from the inner wall 204 toward the light-sensing area 112 of the image sensor 102, thereby causing a flash on the image detected by the image sensor 102.

[0052] Figure 4 An exemplary cross-section 400 of the retaining wall 408 according to an embodiment of the present invention is shown in the plane xy. 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 [link]). Figure 1 The retaining wall 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... Figure 4As shown, and may be other serrated patterns. When incident light 120 reaches the inner wall 404, the serrated inner wall 404 may not reflect the incident light 120 toward the photosensing area 112, and therefore will not cause flashes on the detected image. The serrated inner wall 404 reduces or eliminates incident light reflected toward the photosensing area 112. The dam 408 may or may not completely enclose the photosensing area 112.

[0053] Figure 5 An exemplary cross-section 500 of a dam 508 according to an embodiment of the present invention is shown in a plane zy. The cross-section 500 is parallel to a 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 incident light 120 reaches the inner wall 504, the inclined and / or curved surface of the inner wall 504 prevents the incident light 120 from reflecting toward the light-sensing area 112 of the image sensor 102, and therefore does not cause flash in the image detected by the image sensor 102. The inner wall 504, with its inclined and / or curved surface, reduces or eliminates incident light reflected toward the light-sensing area of ​​the image sensor 102.

[0054] The inner wall 504 may have an inclined surface, such as from Figure 5 The cross-section 500 shown is in a plane or a 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 surface 134 of the light-sensing area 112 of the image sensor 102, shown in the xy plane, is either on the surface 132 of the cover glass 110 or on the surface 134 of the light-sensing area 112 of the image sensor 102 (see [reference]). Figure 1 The cross-section 400 is seen in a parallel horizontal plane.

[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 attached to a first side of a substrate 604. The image sensor 602 is wire-bonded to a pad on the first side of the substrate 604 via a wire 606. A dam 608 is disposed between the image sensor 602 and a cover glass 610, the cover glass 610 enclosing or surrounding a photosensitive area 612 of the image sensor 602. For example, the dam 608 is located directly between the image sensor 602 and the cover glass 610. The cover glass 610 covers the photosensitive 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 outside the image sensor module 600. The image sensor 602 is electrically coupled to the solder balls 614 via wires 606. If necessary, an encapsulation 616 is disposed on a first side of the substrate 604 to cover the wires 606, the substrate 604, and a portion of the image sensor 602 outside the barrier 608. For example, the encapsulation 616 is black.

[0056] Dam 608 can be Figure 4 The dam 408 is shown. The inner wall 624 has a serrated pattern. Figure 4 Similar to the inner wall 404 shown, it reduces or eliminates incident light (not shown) reflected towards the light-sensing area 612 of the image sensor 602. Furthermore, the inner wall 624 may also be as follows: Figure 5 The inner wall 504 shown also has inclined and / or curved surfaces to further reduce or eliminate incident light reflected towards the light-sensing area 612 of the image sensor 602. Therefore, the dam 608 can be... Figure 5 The dam 508 shown has the same characteristics as... Figure 5 The wall 626 shown is similar to wall 526. The cross-section of wall 626 of dam 608 in plane zy has a wider portion near cover glass 610 and a narrower portion near image sensor 602. However, in order to further reduce or eliminate incident light reflected toward the photosensitive area 612 of image sensor 602, the thickness of dam 608 is less than 40 μm.

[0057] Figures 7A to 7G An exemplary method for manufacturing at least one dam (e.g., dam 608) attached to a coverslip (e.g., coverslip 610) according to an embodiment of the present invention is shown, the method comprising eight main steps. Figure 7A The first step is shown, in which a coverslip 702 is provided and, if necessary, cleaned by plasma 704. The coverslip 702 may be a glass wafer. Figure 7B The second step is shown, in which a cover glass 702 is laminated using a dry film 706. The dry film 706 is a photolithography material. Figure 7CThe third step is shown, 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 coverslip 702.

[0058] Figure 7D The fourth step is shown, in which the exposure mask 708 is exposed to exposure ultraviolet (UV) light 710. Figure 7E The fifth step is shown: after removing the exposure mask 708, the dry film 706 is developed using 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-curing dam 706A. The dam 706A may be... Figure 4 The dam 408 shown has a serrated pattern on its inner wall. A dam 706A forms a dry film 706, and the cross-section of the inner wall 716 of the dam 706A, which is 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 The sixth step is shown, in which a photolithographically treated dry film 706, including a dam 706A, is cured by heating. The cured dry film 706 forms at least one cured dam 706A attached to a coverslip 702. For simplicity, both the uncured and cured dam 706A are identified as dam 706A. Heating causes the dry film of the dam 706A to overflow onto the surface 720 of the coverslip 702. The coverslip 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 coverslip 702, has a wider portion closer to the coverslip 702 and a narrower portion farther from the coverslip 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 coverslip 702, forms an inclined surface.

[0060] Figure 7G The seventh step is shown, in which the coverslip 702 is flipped so that the dam 706A is located below the coverslip 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 The eighth step is illustrated, in which a flipped coverslip 702, including a dam 706A attached to the coverslip 702, is placed on an image sensor 712 including a 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 coverslip 702. A necessary adhesive may 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 used as Figure 6The cover glass 610, the barrier 608, and the image sensor 602 are shown. The barrier 706A is made of dry film 706. The cured dry film 706 forms at least one barrier 706A attached to the cover glass 702. The image sensor 712 may be one of at least one image sensors on a substrate wafer.

[0062] Although the invention has been set forth herein with reference to exemplary embodiments and the best mode for practicing the invention, it will be apparent to those skilled in the art that many refinements, modifications, and sub-combinations, as well as various alterations and variations, can be made to the invention with respect to the various embodiments without departing from the spirit and scope of the invention.

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

Claims

1. A method for forming a dam for an image sensor module, comprising: Provide cover glass; The cover glass is laminated with a dry film, wherein the dry film is a photolithographic material; The exposure mask is aligned 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. The exposure mask is exposed using ultraviolet light; The exposed dry film is developed using a photolithography process; as well as The photolithographically treated dry film is cured by heating; The cured dry film forms at least one dam attached to the coverslip. The heating process that cures the photolithographically processed dry film causes the dry film to overflow onto the surface of the cover glass. After the overflow cools, the cross-section of the inner wall of the formed dam, which is orthogonal to the surface of the cover glass, has a wider portion closer to the cover glass and a narrower portion farther away from the cover glass due to the overflow.

2. The method according to claim 1 further includes plasma cleaning of the coverslip before laminating the coverslip with the dry film.

3. The method of claim 1, further comprising, after curing the photolithographically treated dry film: Flip the cover glass over; and An inverted cover glass, including a dam attached to the cover glass, is placed on an image sensor that includes a light-sensing area, wherein the dam surrounds the light-sensing area.

4. The method of claim 3, further comprising applying an adhesive between the image sensor and the barrier to mount the barrier to the image sensor before placing the flipped cover glass, which includes the barrier attached to the cover glass, onto the image sensor.

5. The method of 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 of claim 3, wherein the image sensor is at least one of the image sensors on the substrate wafer.

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

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

9. The method of claim 1, wherein the cross-section of the inner wall of the formed dam, orthogonal to the surface of the cover glass, forms an inclined surface.

10. The method of claim 9, wherein the formed dam includes the inner wall having 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 of claim 1, wherein the formed dam includes 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 near the cover glass and a narrower portion away from the cover glass.

12. The method of claim 1, wherein the cover glass is a glass wafer.

13. The method of claim 1, wherein the cross-section of the inner wall of the formed dam, orthogonal to the surface of the cover glass, forms a curved surface.

14. The method of claim 13, wherein the formed dam includes 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.

Images