TWI851107B - Image sensor and method for manufacturing the same - Google Patents

Abstract

The subject disclosure provides an image sensor, including a photo sensing layer for receiving and detecting an incident light in a wavelength range and generating an optical signal indicative of the incident light, wherein the photo sensing layer has a first surface and a second surface opposite to the first surface; a redistribution layer (RDL) disposed on the first surface of the photo sensing layer, the redistribution layer including a plurality of conductive traces for receiving an electrical signal indicative of the optical signal; and a protection layer disposed on the redistribution layer and opposite to the photo sensing layer, the protection layer configured to reflect the incident light passing through the photo sensing layer and the redistribution layer and to direct a reflected light toward the second surface of the photo sensing layer to depart from the second surface, wherein the protection layer is opaque and reflective with respect to the optical signal within the wavelength range

Description

Image sensor and manufacturing method thereof

The present invention generally relates to image sensors, and more particularly to image sensors that reduce or eliminate ghost images caused by light reflections.

Image sensors with visible and near infrared (NIR) capabilities have been widely used in digital still cameras, cellular phones, security cameras, and medical, automotive, and other applications. Image sensors include an array of pixels with photosensitive elements (e.g., photodiodes) that absorb a portion of the incident image light and generate image charges shortly after absorbing the image light. Such sensors can operate in dual mode, which allows them to perform dual functions in daytime (visible spectrum applications) and night vision (infrared applications). This incorporated infrared capability is made possible by the development and implementation of state-of-the-art enhancements that expand the sensor's spectral light sensitivity to approximately 1050nm (which fits into the near-infrared range of 750-1400nm).

One drawback of this dual-mode capability is that the new sensitivity in the near-IR range has resulted in constructed IR ghosting. In certain cases, IR radiation can be reflected, for example, by the image sensor's redistribution layer (RDL) and then detected by the image sensor. This generates noise that enters the image sensor, thus reducing the image sensor's sensitivity.

The technology used to manufacture image sensors has continued to advance at a rapid pace. The need for higher resolution and lower power consumption has driven further miniaturization and integration of these devices. As the demand for image sensors continues to increase, high packing density and isolation of the pixel cells in image sensors as well as low noise performance have become increasingly challenging.

In order to solve the problem of image sensor detecting ghost images due to reflection and causing noise, the present invention provides an improved sensor element. The present invention mainly improves the stacking structure, and reduces the reflection caused by the redistribution layer (RDL) through an opaque protective layer, thereby reducing the ghost images detected by the image sensor, which can simplify the process and reduce the stress problem of multiple stacking layers, thereby reducing the risk of component failure.

In one or more embodiments, according to one aspect of the present invention, an image sensor includes a photosensitive layer for receiving an incident light in a wavelength range, detecting the incident light, and generating an optical signal representing the incident light, wherein the photosensitive layer has a first surface and a second surface opposite to the first surface; a redistribution layer (RDL) disposed on the first surface of the photosensitive layer, the redistribution layer The distribution layer includes a plurality of conductive tracks for receiving an electrical signal representing the optical signal; and a protective layer disposed on the redistribution layer and opposite to the photosensitive layer, the protective layer being configured to reflect incident light passing through the photosensitive layer and the redistribution layer and direct a reflected light toward the second surface of the photosensitive layer and away from the second surface, wherein the protective layer is opaque to light in the wavelength range.

According to one aspect of the present invention, a method for manufacturing an image sensor includes providing a substrate; forming a photosensitive layer on the substrate for receiving a light signal in a wavelength range, wherein the photosensitive layer has a first surface and a second surface opposite to the first surface; forming a redistribution layer on the first surface of the photosensitive layer, wherein the redistribution layer includes a plurality of conductive tracks for receiving an electrical signal representing the light signal; and forming a protective layer on the redistribution layer and opposite to the photosensitive layer, wherein the protective layer is configured to reflect incident light passing through the photosensitive layer and the redistribution layer, and direct a reflected light toward the second surface of the photosensitive layer and away from the second surface, wherein the protective layer is opaque and reflective to light in the wavelength range.

1: Image sensor

2: Image sensor

3: Image sensor

6: Image sensor

7: Image sensor

12: Light-sensing layer

12s: side surface

14: Color filter

16: Lens

18: Isolation layer

18s: Side surface

20:Redistribute layers

22: Protective layer

22a: Notch

22a1: First arm

22a2: Second arm

22b: Notch

22b1: Notch

22b2: Notch

22b3: Notch

22s: side surface

22s1: Side surface

24: Electrical contacts

26: Window hole

28: Incident light

31: Incident light

32: Reflected light

38: Reflected light

40: Back side metal barrier (BSMG) layer

91: Steps

92: Steps

93: Steps

94: Steps

95: Steps

96: Steps

97: Steps

121: Surface

122: Surface

201: Surface

202: Surface

205: Exposed part

Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like element symbols refer to like parts throughout the various views unless otherwise specified.

FIG1 shows a cross-sectional view of an image sensor according to some embodiments of the present invention.

FIG2 shows a bottom view of an image sensor according to some embodiments of the present invention.

FIG3 shows a cross-sectional view of an image sensor according to some embodiments of the present invention.

FIG4 shows a bottom view of an image sensor according to some embodiments of the present invention.

Figure 5 is a cross-sectional view of Figure 4 cut along line A-A.

FIG6 shows a perspective view of an image sensor according to some embodiments of the present invention.

FIG. 7 shows a perspective view of an image sensor according to some embodiments of the present invention.

FIG8A includes an image in which a ghost image is formed.

FIG8B includes a clear image, that is, a contrast image, in which no ghost images are formed.

FIG9 shows a flow chart of a method for manufacturing an image sensor according to the present invention.

Common reference numerals are used throughout the various drawings and detailed descriptions to indicate the same or similar components. The present invention can be best understood based on the following detailed description made in conjunction with the accompanying drawings.

In the following description, many specific details are set forth to provide a thorough understanding of one of the embodiments. However, those skilled in the art will recognize that the techniques described herein may be practiced without one or more of the specific details or may be practiced using other methods, components, materials, etc. In other examples, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring certain aspects.

References to "an example" or "an embodiment" throughout this specification mean that a particular feature, structure, or characteristic described in conjunction with that example is included in at least one example of the invention. Therefore, the phrases "in an example" or "in an embodiment" appearing in various places throughout this specification may not all refer to the same example and embodiment. In addition, the particular features, structures, or characteristics may be combined in any suitable manner in one or more examples and embodiments.

Spatially relative terms such as "below," "beneath," "lower," "below," "above," "upper," and the like may be used herein for ease of explanation to describe the relationship of one element or feature to another element or features illustrated in the figures. It will be understood that these spatially relative terms are intended to cover different orientations of the device when in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is flipped, elements described as being "below" or "beneath" or "below" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "below" and "below" may cover both orientations of above and below. The device may be oriented in other ways (rotated 90 degrees or in other orientations) and the spatially relative descriptors used herein interpreted separately. Additionally, it will be understood that when a layer is referred to as being "between" two layers, it may be the only layer between the two layers, or one or more intervening layers may also be present.

Throughout this specification, several terms are used. These terms will assume their ordinary meaning in the art from which they come, unless otherwise specifically defined herein or the context of their use would clearly imply otherwise. It should be noted that in this document, chemical element names and their symbols are used interchangeably (e.g., Si and silicon); however, both have the same meaning.

FIG. 1 shows a cross-sectional view of an image sensor 1 according to some embodiments of the present invention. As shown in FIG. 1 , the image sensor 1 may be a multi-layer structure. In some embodiments, the image sensor 1 may include a photosensitive layer 12, a color filter 14, a lens 16, an isolation layer 18, a redistribution layer (RDL) 20, a protective layer 22, and electrical contacts 24.

Referring to FIG. 1 , the image sensor 1 may include a photosensitive layer 12, which may include a photosensitive element (e.g., a photodetector). The photosensitive layer 12 may receive and detect a light signal of incident light of a specific wavelength incident on the surface 121. In some embodiments, the photosensitive layer 12 may detect visible light, infrared light (IR), or near infrared light (NIR). The photosensitive layer 12 may be used to receive light with a wavelength of 400 nm to 1000 nm. The photosensitive layer 12 may generate an electrical signal representing the detected light property (e.g., the intensity of the detection light) based on the detected incident light and output the electrical signal. The photosensitive layer 12 may have a surface 121 (also referred to as the second surface) and a surface 122 (also referred to as the first surface) opposite to the surface 121.

In some embodiments, a redistribution layer (RDL) 20 is disposed on the surface 122 of the photosensitive layer 12. The redistribution layer 20 may have a surface 201 and a surface 202 opposite to the surface 201.

In some embodiments, the redistribution layer 20 is a patterned conductive layer including tracks. The redistribution layer 20 may include a patterned conductive metal layer, the material of which may include, for example, gold (Au), silver (Ag), copper (Cu), nickel (Ni), palladium (Pd), solder alloy, or a combination of two or more thereof. The redistribution layer 20 may be used to conduct electrical signals as needed, for example, the electrical signal generated by the photosensitive layer 12 may be electrically communicated with the electrical contact 24 via the redistribution layer 20, and may be electrically communicated with external electronic components via the electrical contact 24.

In some embodiments, the image sensor 1 may further include an isolation layer 18 disposed between the photosensitive layer 12 and the redistribution layer 20. The isolation layer 18 may be formed on the surface 122 of the photosensitive layer 12 and in contact with the redistribution layer 20. In some embodiments, the isolation layer 18 is light-transmissive.

A protective layer 22 may be formed on one side of the surface 122 of the photosensitive layer 12. The protective layer 22 may be formed on the isolation layer 18 and in contact with the isolation layer 18. The protective layer 22 may be formed on the redistribution layer 20 and opposite to the photosensitive layer 12. The protective layer 22 may be disposed on the surface 202 of the redistribution layer 20 to protect the conductive traces from external environmental interference, such as moisture and electrical interference. In some embodiments, the protective layer 22 may be formed inside the redistribution layer 20, i.e., between the conductive traces. The protective layer 22 may laterally wrap around the redistribution layer 20 to protect the conductive traces from open circuits or short circuits of the conductive traces.

In some embodiments, the protective layer 22 may be a passivation layer. In some embodiments, the protective layer 22 may be insulating and may include a polymer. The protective layer 22 may include a black solder mask film (BSMF). The protective layer 22 has a thickness less than or equal to 3 micrometers (um). In some embodiments, the protective layer 22 has a transmittance of less than 1% for light with a wavelength of 400nm to 1000nm. Preferably, the protective layer 22 has a transmittance of less than 0.5% for light with a wavelength of 400nm to 1000nm. Further, preferably, the protective layer 22 has a transmittance of less than 0.3% for light with a wavelength of 400nm to 1000nm.

The protective layer 22 is substantially opaque to light within a specific wavelength range, and in some embodiments is reflective. Incident light with a specific wavelength is incident on the surface 121 of the photosensitive layer 12, passes through the redistribution layer 20, is incident on the protective layer 22, is reflected by the protective layer 22, and the reflected light passes through the redistribution layer 20 and is directed toward the surface 121 of the photosensitive layer 12, leaving the image sensor 1.

In some embodiments, the protective layer 22 is substantially opaque to light in a specific wavelength range, has low reflectivity, and can absorb light in a specific wavelength range. In some embodiments, the reflectivity of the protective layer 22 for light with a wavelength of 400nm to 1000nm is less than 5%, and preferably, the reflectivity of the protective layer 22 for light with a wavelength of 400nm to 1000nm is less than 3%. Light with a specific wavelength that is incident on the protective layer 22 through the light sensing layer 12 and the redistribution layer 20, and/or incident light that is incident on the protective layer 22 from the external environment, can be absorbed by the protective layer 22.

The incident light may be reflected back to the photosensitive layer 12 when it enters the RDL layer and/or the protective layer 22 through the photosensitive layer 12, which will produce ghost images caused by reflection. A protective layer that is substantially opaque to light in a specific wavelength range and has a low reflectivity will effectively reduce ghost images caused by reflection.

Incident light 31 from another direction of the image sensor 1 (such as ambient light) incident from the outside toward the image sensor 1 can be reflected by the protective layer 22 to become reflected light 32 and leave the image sensor 1.

In some embodiments, the protective layer 22 is substantially opaque to light of a specific wavelength and has the characteristics of partial absorption and partial reflection. In some embodiments, the protective layer 22 is an infrared light absorption layer or an infrared light reflection layer.

The protective layer 22 may be an insulating material. In one embodiment, the protective layer 22 may be an organic polymer material. In some embodiments, the protective layer 22 may include an organic material, a solder mask, polyimide (PI), an epoxy resin, one or more molding materials, borophosphosilicate glass (BPSG), silicon oxide, silicon nitride, silicon oxynitride, any combination thereof, etc. Examples of molding materials may include, but are not limited to, epoxy resins containing fillers dispersed therein. In some embodiments, the protective layer 22 may include inorganic materials such as silicon, ceramics, etc. In some embodiments, the protective layer 22 may include a material that is the same as or similar to the insulating layer 18.

One or more electrical contacts 24 may be formed on the surface 202 of the redistribution layer 20 and penetrate the protective layer 22 to electrically contact the redistribution layer 20. Referring to FIG. 1 , the electrical contacts 24 may be in the form of conductive solder bumps. That is, the electrical contacts 24 may be a conductive input/output (I/O) pad. The electrical contacts 24 may be formed in the protective layer 22 to contact the redistribution layer 20 and provide electrical connections between external components and the redistribution layer 20. In some embodiments, the electrical contacts 24 may be partially covered laterally by the protective layer 22. The redistribution layer 20 is a patterned metal layer circuit that can be powered from various locations inside the image sensor 1 to the outside through electrical connections of the electrical contacts 24.

The photosensitive layer 12 may have a side surface 12s, which may be aligned with a side surface 18s of the isolation layer 18. The protective layer 22 may have a side surface 22s, which may be aligned with the side surface 18s of the isolation layer 18. In some embodiments, the side surface 22s of the protective layer 22 may be aligned with the side surface 12s of the photosensitive layer 12. In some embodiments, the side surface 22s of the protective layer 22 may be coplanar with the side surface 12s of the photosensitive layer 12. In another embodiment, the side surface 12s of the photosensitive layer 12, the side surface 18s of the isolation layer 18, and the side surface 22s of the protective layer 22 may be coplanar.

The color filter 14 may include various patterns formed on the side of the surface 121 of the light sensing layer 12. In some embodiments, the color filter 14 may be configured as an array. For example, an RGB (red, green and blue) filter of a Bayer pattern. The color filter 14 may include a full-color filter, that is, a clear filter.

In some embodiments, the lens 16 may be disposed on the color filter 14 and relative to the photosensitive layer 12. The color filter 14 may be disposed between the pixel lens 16 and the photosensitive layer 12. Each lens 16 may be formed on a respective color filter 14 to guide incident light through the respective color filter 14 to reach the photosensitive layer 12. In some embodiments, the lens 16 may be a microlens or a pixel lens. Corresponding to the color filter 14, the lens 16 may be configured as an array. As shown in FIG. 1 , the incident light 28 enters the photosensitive layer 12 of the image sensor 1 through the lens 16 and the filter 14 in the window 26 and is sensed by the photosensitive layer 12.

In the current implementation, incident light 31 (e.g., infrared light or near-infrared light) may enter the image sensor 1 through the back side of the image sensor 1 (i.e., the side opposite to the side where the color filter 14 is located). It may pass through the protective layer 22, the redistribution layer 20, and the isolation layer 18 and enter the photosensitive layer 12, thereby generating a ghost image of the redistribution layer 20.

However, the protective layer 22 disposed on the back (or bottom) of the image sensor 1 provided in the present case can be reflective to infrared light or near-infrared light. Therefore, the incident light 31 (for example, infrared light, near-infrared light or other light of a specific wavelength range that can cause ghosting) incident from the back will be reflected by the protective layer 22 to become reflected light 32, thereby preventing the light from penetrating into the image sensor 1. In this way, the incident light 31 from the back cannot cause ghosting.

According to the present invention, the protective layer 22 can protect the conductive track (such as the redistribution layer 20) from being disturbed by the external environment, and can reflect and/or absorb unwanted light. The protective layer 22 having at least these two functions eliminates the need to add an additional layer structure to the image sensor 1, simplifies the manufacturing process, and avoids stress problems caused by multiple layers of film, such as warping or deformation of the component due to thermal stress during the manufacturing process or operation.

In some embodiments, the material of the protective layer 22 and the material of the insulating layer 18 can be substantially the same. In some embodiments, the coefficient of thermal expansion (CTE) of the protective layer 22 and the coefficient of thermal expansion of the insulating layer 18 can be close to or substantially the same, so that deformation or warping during the manufacturing process and/or operation of the image sensor can be reduced.

FIG. 2 shows a bottom view of an image sensor 1 according to some embodiments of the present invention. FIG. 2 shows a bottom view of the image sensor 1 in FIG. 1 , i.e., a top view of one side with electrical contacts 24. Referring to FIG. 2 , the image sensor 1 includes a plurality of electrical contacts 24 disposed on a protective layer 22. For a detailed description of the protective layer 22 and the electrical contacts 24, please refer to the relevant paragraphs of FIG. 1 .

The electrical contacts 24 may be configured as an array, which may have one or more rows or one or more columns. As shown in FIG. 2 , the array of electrical contacts 24 may have ten rows. In some embodiments, the array of electrical contacts 24 may have less than or more than ten rows. The array of electrical contacts 24 may have seven columns. In some embodiments, the array of electrical contacts 24 may have less than or more than seven columns. In some embodiments, each row may have the same or different number of electrical contacts 24. For example, a row may have 1, 2, 3, 4, 5, 6, or 7 electrical contacts 24. Each column may have the same or different number of electrical contacts 24. For example, a row may have 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 electrical contacts 24. In some embodiments, the orientation of the image sensor 1 may not be confirmed because the protective layer 22 is opaque. The array of asymmetric electrical contacts 24 can be used to confirm the orientation of the image sensor 1, thereby improving the production yield in subsequent manufacturing processes.

FIG. 3 shows a cross-sectional view of an image sensor 2 according to some embodiments of the present invention. Referring to FIG. 3 , various components of the image sensor 2 are the same as the corresponding components of the image sensor 1 described above in FIG. 1 and FIG. 2 . These similar components are represented by similar reference numerals. The detailed description of these similar components will not be repeated. Compared with the image sensor 1 of FIG. 1 , the image sensor 2 includes a back side metal grid (BSMG) layer 40.

Referring to FIG. 3 , the back metal barrier layer 40 may be disposed on one side of the photosensitive layer 12, relative to the redistribution layer 20. In some embodiments, the back metal barrier layer 40 may be disposed in the photosensitive layer 12. In some embodiments, the back metal barrier layer 40 may be disposed adjacent to the color filter 14. The back metal barrier layer 40 may be disposed between the photosensitive layers 12. That is, after the incident light 28 passes through the lens 16 and the color filter 14, it penetrates through the gap of the back metal barrier layer 40 and is received by the photosensitive layer 12.

In some embodiments, the back metal barrier layer 40 may include a plurality of vertical lines and a plurality of horizontal lines that intersect each other perpendicularly (in a top view). Therefore, the back metal barrier layer 40 may include a plurality of gaps defined by vertical lines and horizontal lines that are perpendicular to each other. In some embodiments, each gap of the back metal barrier layer 40 corresponds to each color filter 14. In other words, the gap of the back metal barrier layer 40 can be aligned with the color filter 14.

The back metal barrier layer 40 can be made of various types of metals to reflect light. For example, the back metal barrier layer 40 can be made of aluminum (Al), copper (Cu), tungsten (W) or other metals. In some embodiments, the vertical and horizontal lines of the back metal barrier layer 40 can have a width of about 0.1 microns to 0.3 microns.

The incident light 28 incident on the image sensor 2 can be reflected by the redistribution layer 20 or the protective layer 22, and further reflected in the photosensitive layer 12 through the back metal barrier layer 40 to become the reflected light 38. The reflected light 38 can be reflected again at any interface between the layers and end up being collected by a neighboring pixel. The image sensor 2 with the back metal barrier layer 40 can improve the reflection problem in the image sensor. The reflected light 38 reduces the ghost problem by consuming light intensity in the optical path.

FIG. 4 shows a bottom view of an image sensor 3 according to some embodiments of the present invention. Referring to FIG. 4 , various components of the image sensor 3 are identical to the corresponding components of the image sensor 1 described above in FIGS. 1 and 2 . These similar components are represented by similar reference numerals. The detailed description of these similar components will not be repeated. The image sensor 3 may include a plurality of electrical contacts 24 disposed on the protective layer 22 .

In some embodiments, the protective layer 22 may be patterned to form a recess 22a at a first position and one or more recesses 22b at a second position, wherein the recess 22a and/or one or more recesses 22b may be used to indicate the orientation of the image sensor. In some embodiments, the recess 22a may be formed at a position corresponding to a component active area of the image sensor 3, and the recess 22b may be formed at a corner position of the component active area of the image sensor.

FIG5 is a cross-sectional view of FIG4 along the A-A line. The protective layer 22 is patterned so that a notch 22a is formed near the middle to expose an exposed portion 205 of the redistribution layer 20. Since the etchant has different etching speeds for the redistribution layer 20 and the protective layer 22 including a conductive material (e.g., metal), the depth of the notch 22a may be different. The etchant may stop etching the protective layer 22 in the protective layer 22, or may stop at the interface between the protective layer 22 and the isolation layer 18, or may stop at the isolation layer 18. In some embodiments, the notch 22a may expose a portion of the isolation layer 18. Since the exposed portion 205 is subjected to the action of the etchant, the thickness of the exposed portion 205 may be less than the thickness of other conductive tracks of the redistribution layer 20. In some embodiments, based on the selectivity of the etchant used for the conductive material, the exposed portion 205 may have substantially the same thickness as other conductive tracks of the redistribution layer 20.

In some embodiments, the protective layer 22 is substantially opaque to visible light, while the redistribution layer 20 is reflective to visible light, so when the recess 22a is viewed from the direction of the electrical contact 24, the reflection of the exposed portion 205 of the redistribution layer 20 can be seen, and the orientation of the image sensor 3 can be determined by the exposed portion 205.

The protective layer 22 that is opaque to a specific wavelength (e.g., visible light) can not only isolate the redistribution layer 20 having conductive tracks from interference from the environment (e.g., moisture), but also protect the image sensor from unwelcome light interference, for example. In the known component structure, the protective layer that isolates the redistribution layer from moisture and the light-shielding layer that isolates ambient light are different layers. On the contrary, in the present invention, the protective layer 22 has the function of isolating moisture and the function of light-shielding, which can reduce the process of stacking layers, reduce the complexity of etching to form the notch, and further reduce the warping and deformation caused by stress, thereby reducing the risk of component failure.

In some embodiments, the width of the notch 22a may be substantially equal to the width of the exposed portion 205 of the redistribution layer 20. In some embodiments, the width of the notch 22a may be greater than the width of the exposed portion 205 of the redistribution layer 20.

The notch 22a may be located in an element active area of the image sensor 3. In some embodiments, the notch 22a may be substantially located at or near the middle of the image sensor 3.

Referring to FIG. 4 , the notch 22a can be patterned into an L-shaped notch. In some embodiments, the L-shaped notch 22a has two arms substantially perpendicular to each other, including a first arm 22a1 and a second arm 22a2. The two arms are substantially parallel to the rows and columns of the electrical contacts 24 forming the array, for example, the first arm 22a1 is substantially parallel to the X direction of the electrical contact array, and the second arm 22a2 is substantially parallel to the Y direction of the electrical contact array.

To facilitate directional reading, the lengths of the two substantially perpendicular arms of the L-shaped notch 22a may be different, for example, the length of the first arm 22a1 may be longer than the length of the second arm 22a2, and vice versa. In some embodiments, the widths of the two substantially perpendicular arms of the L-shaped notch 22a may be different, for example, the width of the first arm 22a1 may be greater than the width of the second arm 22a2, and vice versa.

The orientation of the image sensor can be determined based on the direction of the arm of the L-shaped notch 22a. Taking Figure 4 as an example, based on the intersection of the first arm 22a1 and the second arm 22a2, the first arm 22a1 extends along the -X direction, and the second arm 22a2 extends along the -Y direction. In other embodiments, the first arm 22a1 can extend along the X direction. In some embodiments, the second arm 22a2 can extend along the Y direction.

In some embodiments, the notch 22a is configured to be located between adjacent electrical contacts 24. The notch 22a may be aligned with a row of electrical contacts 24. For example, the notch 22a may be aligned with the electrical contacts 24 in the X direction. In some embodiments, the notch 22a may be aligned with the electrical contacts 24 in the Y direction. In some embodiments, the notch 22a may not be aligned with the electrical contacts 24 (horizontally or vertically).

Since the protective layer 22 is opaque, it is difficult to know the orientation of the image sensor from its appearance. The conductive track layout of the RDL layer cannot be seen from the appearance of the image sensor, which may cause errors in the subsequent manufacturing process when the electrical contacts are electrically coupled with external components. We can use the special pattern of the notch 22a and the reflection of the RDL layer to determine the orientation of the image sensor and then determine the correct connection of each electrical contact.

In some embodiments, the notch 22b may be located around the component active area of the image sensor 3. In some embodiments, the notch 22b may be formed at a corner position of the component active area.

Referring to FIG. 4 , the image sensor 3 includes four notches 22b. By etching, the protective layer 22 forms notches 22b at four corners of the component active area of the image sensor 3. In some embodiments, the number of notches 22b may be greater than 4. For example, the notches 22b may be located at least one edge of the image sensor 3, thereby outlining the edge of the image sensor 3. In some embodiments, the notches 22b may surround the component active area of the image sensor 3.

The notch 22b can be patterned into a rectangular notch. In some embodiments, the notch 22b can be patterned into a long strip notch. In some embodiments, the notch 22b can be formed by asymmetrically patterning around the element active area of the image sensor 3 to help determine the element orientation of the image sensor 3.

Since the protective layer 22 is opaque, the conductive track layout of the RDL layer cannot be seen from the appearance of the image sensor, so it is difficult to determine the range of the component active area of the image sensor 3. By configuring the notch 22b, the range of the component active area of the image sensor 3 can be observed and confirmed in a visible light environment, which is helpful for subsequent processes (such as singulation processes).

In some embodiments, the depth of the notch 22a may be the same as the depth of the notch 22b. In some embodiments, the depth of the notch 22a may be different from the depth of the notch 22b. In some embodiments, the depth of the notch 22b may penetrate the protective layer 22 by etching. In some embodiments, etching is performed by an etchant, so that the etching stops at the protective layer 22. In some embodiments, the etching stops at the isolation layer 18, or the etching stops at the interface between the protective layer 22 and the isolation layer 18, so that the isolation layer 18 is exposed. In some embodiments, the etching stops at the redistribution layer 20, so that the conductive material of the redistribution layer 20 is exposed.

In some embodiments, the notch 22b is formed at the outermost periphery of the element, so that the protective layer 22 may have an outer surface 22s1 that is recessed from the outer surface 18s of the isolation layer 18. In other words, the protective layer 22 may have a width smaller than the width of the isolation layer 18. In some embodiments, the side surface 22s1 of the protective layer 22 may be recessed from the side surface 12s of the photosensitive layer 12.

FIG. 6 shows a perspective view of an image sensor 6 according to some embodiments of the present invention. The conductive line pattern of the redistribution layer 20 shown in FIG. 6 is only an example and is not intended to limit the scope of the present invention. The protective layer 22 is omitted in FIG. 6 to clearly show the redistribution layer 20. The image sensor 6 includes an RDL layer 20 and an electrical contact 24 overlapping the conductive track of the RDL 20. The notch 22a with an L-shaped pattern helps us determine the orientation of the image sensor 6. The notch 22a is formed in the component active area, and the notch 22a exposes a portion of the RDL layer. The notches 22b1, 22b2 and 22b3 are located at the corners of the component active area, which helps to determine the range of the component active area of the image sensor 6. In some embodiments, the notches 22b1, 22b2 may be formed adjacent to the conductive material of the redistribution layer 20 without exposing the conductive material of the redistribution layer 20. In some embodiments, the notch 22b3 may at least partially expose the conductive material of the redistribution layer 20. The asymmetric configuration of the notches 22b1, 22b2, and 22b3 also helps us determine the orientation of the image sensor 6.

The electrical contact 24 is formed on the redistribution layer 20 and is electrically coupled to the redistribution layer 20. In some embodiments, the electrical contact 24 is in electrical contact with the redistribution layer 20. The electrical contact 24 is used to provide an electrical connection between an external component and the redistribution layer 20.

FIG. 7 shows a perspective view of an image sensor 7 according to some embodiments of the present invention. The protective layer 22 is omitted in FIG. 7 to clearly show the redistribution layer 20. Referring to FIG. 7, the image sensor 7 may include a redistribution layer 20 having a conductive circuit pattern, a plurality of electrical contacts 24, a notch 22a, and a notch 22b. In some embodiments, the electrical contacts 24 are disposed on and in contact with the redistribution layer 20 to provide an electrical connection between an external component and the redistribution layer 20.

Referring to the embodiment of FIG. 7 , the notch 22a is disposed at a position close to the center of the component function of the image sensor, and the notch 22a exposes the redistribution layer 20. In some embodiments, the exposed portion of the redistribution layer 20 exposed by the notch 22a is an electrical signal communication line. In some embodiments, the redistribution layer 20 exposed by the notch 22a is independent of the electrical signal communication line, is not electrically connected to the photosensitive layer 12, and/or is not electrically connected to the electrical contact 24.

The notch 22b may be disposed at an edge (e.g., a corner position) of the image sensor 7. In some embodiments, the notch 22b may be formed adjacent to the conductive material of the redistribution layer 20 without exposing the conductive material of the redistribution layer 20. In some embodiments, the notch 22b may at least partially expose the conductive material of the redistribution layer 20.

FIG. 8A includes an image that includes ghost images, such as ghost images caused by reflections from the RDL layer, or ghost images caused by ambient light. FIG. 8B includes a clear image, i.e., a contrast image, in which no ghost images are formed. As can be clearly seen in FIG. 8A , an image of the redistribution layer 20 showing its conductive lines and pads is generated within the clear image of the area being viewed. For example, incident light 31 incident from the back side carries information about the shape of the redistribution layer 20 and adds it to the information used to generate the image of FIG. 8A . As described above, such a result is highly undesirable because it reduces the sensitivity of the image sensor and reduces the quality of the image generated by the image sensor. The images in FIGS. 8B and 8A are generated by an image sensor operating in the wavelength range of λ=400~1000nm. In some embodiments, other wavelength ranges may also be applicable and fall within the scope of this disclosure.

FIG. 9 is a flow chart of a method for manufacturing an image sensor according to the present invention. In step 91, a substrate is provided. In step 92, a photosensitive layer is formed on the substrate. In some embodiments, the photosensitive layer can be used to receive a light signal in a specific wavelength range. The photosensitive layer (e.g., photosensitive layer 12) has a first surface (e.g., surface 122) and a second surface (e.g., surface 121) opposite to the first surface. In step 93, an isolation layer (e.g., isolation layer 18) is formed on the photosensitive layer and opposite to the substrate. In step 94, a redistribution layer (e.g., redistribution layer 20) is formed on the photosensitive layer, wherein the redistribution layer includes a plurality of conductive tracks for receiving an electrical signal representing the light signal. In step 95, a protective layer (e.g., protective layer 22) is formed on the redistribution layer and opposite to the photosensitive layer. The protective layer is opaque and reflective to light in the specific wavelength range. In operation 96, the protective layer is patterned so that a first notch (e.g., notch 22a or notch 22b) is formed at a first position. In step 97, a plurality of electrical contacts (e.g., electrical contacts 24) are formed on the redistribution layer and through the protective layer. The detailed description of the image sensor manufactured by these steps is similar to that in Figures 1 to 7 and is omitted for brevity.

The above description of the illustrated examples of the present invention, including those described in the Abstract, is not intended to be exhaustive or to be limiting to the precise form disclosed. Although specific embodiments and examples of the present invention are described herein for illustrative purposes, various equivalent modifications may be made without departing from the broader spirit and scope of the present invention. Indeed, it should be understood that specific example voltages, currents, frequencies, power range values, times, etc. are provided for illustrative purposes and other values may be used in other embodiments and examples according to the teachings of the present invention.

In light of the above detailed description, such modifications may be made to the examples of the present invention. The terms used in the following claims should not be interpreted as limiting the present invention to the specific embodiments disclosed in the specification and claims. Rather, the scope will be determined entirely by the following claims, which will be understood in accordance with the established principles of the claim interpretation. Therefore, this specification and the drawings should be regarded as illustrative rather than restrictive.

1: Image sensor

12: Light-sensing layer

12s: side surface

14: Color filter

16: Lens

18: Isolation layer

18s: Side surface

20:Redistribute layers

22: Protective layer

22s: side surface

24: Electrical contacts

26: Window hole

28: Incident light

31: Incident light

32: Reflected light

121: Surface

122: Surface

201: Surface

202: Surface

Claims (20)

An image sensor comprises: a photosensitive layer for receiving an incident light in a wavelength range, detecting the incident light, and generating a light signal representing the incident light, wherein the photosensitive layer has a first surface and a second surface opposite to the first surface; a redistribution layer layer; RDL), which is disposed on the first surface of the photosensitive layer, the redistribution layer includes a plurality of conductive tracks for receiving an electrical signal representing the optical signal; and a protective layer, which is disposed on the redistribution layer and relative to the photosensitive layer, the protective layer contacts the redistribution layer and laterally covers the redistribution layer, the protective layer is configured to reflect incident light passing through the photosensitive layer and the redistribution layer, and guide a reflected light toward the second surface of the photosensitive layer and leave the second surface, wherein the protective layer is opaque to light in the wavelength range. In the image sensor of claim 1, the protective layer is patterned so that a first notch is formed at a first position to expose the redistribution layer. An image sensor as claimed in claim 1, wherein the protective layer has a thickness greater than or equal to 3 micrometers. As in claim 1, the image sensor, wherein the protective layer comprises an organic polymer material. An image sensor as claimed in claim 2, wherein the first position is located in an element active area. An image sensor as claimed in claim 2, wherein the protective layer is further patterned to form a second notch at a second location. An image sensor as claimed in claim 6, wherein the second notch extends to the RDL. An image sensor as claimed in claim 6, wherein the second notch is located around an active area of a component. An image sensor as claimed in claim 2, wherein the first notch is patterned into an L-shaped notch. An image sensor as claimed in claim 6, wherein the second notch is patterned into a rectangular notch. An image sensor as claimed in claim 6, wherein the first notch has a first depth, the second notch has a second depth, and the second depth is greater than or equal to the first depth. An image sensor as claimed in claim 6, wherein the image sensor has at least two second notches, and the at least two second notches are located at corners of an active area of a component. An image sensor as claimed in claim 1, wherein the transmittance of the protective layer to light with a wavelength of 400nm to 1000nm is less than 1%. An image sensor as claimed in claim 2, wherein the first notch is configured to be located between adjacent electrical contacts and aligned with a row of electrical contacts. An image sensor as claimed in claim 14, wherein the first notch is further configured to align with a row of electrical contacts. The image sensor of claim 1 further comprises an isolation layer disposed between the photosensitive layer and the RDL. The image sensor of claim 1 further comprises a back side metal grid (BSMG) layer, wherein the back side metal grid layer is located on the second side of the photosensitive layer, opposite to the redistribution layer. An image sensor as claimed in claim 17, wherein the light signal is reflected by the protective layer toward the second surface of the photosensitive layer, and further reflected by the back metal barrier layer in the photosensitive layer. A method for manufacturing an image sensor includes: providing a substrate; forming a photosensitive layer on the substrate for receiving a light signal in a wavelength range, wherein the photosensitive layer has a first surface and a second surface opposite to the first surface; forming a redistribution layer (RDL) on the first surface of the photosensitive layer, wherein the redistribution layer includes a plurality of electrical signals for receiving an electrical signal representing the light signal; Conductive tracks; and forming a protective layer on the redistribution layer and opposite to the photosensitive layer, the protective layer is in contact with the redistribution layer and laterally covers the redistribution layer, the protective layer is configured to reflect incident light passing through the photosensitive layer and the redistribution layer, and direct a reflected light toward the second surface of the photosensitive layer and away from the second surface, wherein the protective layer is opaque to light in the wavelength range. The method of claim 19 further comprises patterning the protective layer so as to form a first notch at a first position.

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