CN107785387B

CN107785387B - Image sensor and method for forming the same

Info

Publication number: CN107785387B
Application number: CN201711004542.6A
Authority: CN
Inventors: 龙海凤; 李天慧; 黄晓橹
Original assignee: Huaian Imaging Device Manufacturer Corp
Current assignee: Huaian Xide Industrial Design Co ltd
Priority date: 2017-10-25
Filing date: 2017-10-25
Publication date: 2020-05-05
Anticipated expiration: 2037-10-25
Also published as: CN107785387A

Abstract

The present disclosure relates to an image sensor and a method for forming the same, wherein an image sensor includes: a substrate having a photodiode formed therein; and a light-condensing portion on the substrate, wherein the light-condensing portion has an inclined surface, and is configured to: so that light to enter a peripheral region of the photodiode enters the light-condensing portion from the slope and refracts the light toward the photodiode. The present disclosure relates to an image sensor and a method for forming the same, which allows more light to enter a region of a photodiode in a substrate, thereby improving light sensitivity of the image sensor.

Description

Image sensor and method for forming the same

Technical Field

The present disclosure relates to the field of semiconductors, and in particular, to an image sensor and a method for forming an image sensor.

Background

The image sensor is used to convert an optical image focused on the image sensor into an electrical signal. The image sensor includes an array of photodiodes, and photons of incident light are absorbed and carriers are generated after reaching the photodiodes, thereby generating an electrical signal.

Therefore, there is a need for a new technique to improve the light sensitivity of the image sensor.

Disclosure of Invention

It is an object of the present disclosure to improve the light sensitivity of an image sensor.

According to an aspect of the present disclosure, there is provided an image sensor including: a substrate having a photodiode formed therein; and a light-condensing portion on the substrate, wherein the light-condensing portion has an inclined surface, and is configured to: so that light to enter a peripheral region of the photodiode enters the light-condensing portion from the slope and refracts the light toward the photodiode.

According to another aspect of the present disclosure, there is provided a method for forming an image sensor, including: providing a substrate, wherein a photodiode is formed in the substrate; forming a first material layer on the substrate; and patterning the first material layer to form a light-condensing portion, wherein the light-condensing portion has a slope, and the light-condensing portion is configured to: so that light to enter a peripheral region of the photodiode enters the light-condensing portion from the slope and refracts the light toward the photodiode.

Other features and advantages of the present disclosure will become apparent from the following detailed description of exemplary embodiments thereof, which proceeds with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description, serve to explain the principles of the disclosure.

The present disclosure may be more clearly understood from the following detailed description, taken with reference to the accompanying drawings, in which:

fig. 1 is a schematic diagram schematically showing a structure of an image sensor in the related art in a sectional view.

Fig. 2 is a schematic diagram schematically showing a transmission path of light split in the middle of the image sensor in fig. 1.

Fig. 3 is a schematic diagram schematically illustrating a structure of an image sensor of one exemplary embodiment of the present disclosure and a transmission path of light thereof in the form of a cross-sectional view.

Fig. 4a is a schematic diagram schematically showing one example of a transmission path of light at the slope B in fig. 3.

Fig. 4b is a schematic view schematically showing one example of the transmission path of light at the interface E in fig. 3.

Fig. 5 is a schematic diagram schematically illustrating a structure of an image sensor of one exemplary embodiment of the present disclosure and a transmission path of light thereof in the form of a cross-sectional view.

Fig. 6 is a schematic diagram schematically illustrating a structure of an image sensor of one exemplary embodiment of the present disclosure and a transmission path of light thereof in the form of a cross-sectional view.

Fig. 7a is a schematic diagram schematically showing one example of a transmission path of light at the slope D in fig. 6.

Fig. 7b is a schematic view schematically showing one example of the transmission path of light at the interface E in fig. 6.

Fig. 8 is a schematic diagram schematically illustrating a structure of an image sensor of one exemplary embodiment of the present disclosure and a transmission path of light thereof in the form of a cross-sectional view.

Fig. 9a to 9f are schematic diagrams respectively showing a cross section of an image sensor at respective steps of one example of a method in forming the image sensor according to one example embodiment of the present disclosure.

Note that in the embodiments described below, the same reference numerals are used in common between different drawings to denote the same portions or portions having the same functions, and a repetitive description thereof will be omitted. In this specification, like reference numerals and letters are used to designate like items, and therefore, once an item is defined in one drawing, further discussion thereof is not required in subsequent drawings.

For convenience of understanding, the positions, sizes, ranges, and the like of the respective structures shown in the drawings and the like do not sometimes indicate actual positions, sizes, ranges, and the like. Therefore, the disclosed invention is not limited to the positions, dimensions, ranges, etc., disclosed in the drawings and the like.

Further, those skilled in the art will appreciate that the transmission paths of light shown in the drawings are illustrative only and do not constitute a limitation on any of the following: angle and position of light incidence, angle of light refraction, direction of light transmission, depth of light incidence, number of light transmission paths, and density of light.

Detailed Description

Fig. 1 shows a structure of an image sensor in the related art. The related art image sensor includes a substrate 10, and a photodiode 11 is formed in the substrate 10, wherein the photodiode 11 senses light. In a peripheral region 12 around the photodiode 11 in the substrate 10, a device and a circuit or the like that converts the sensed light into an electrical signal may be formed. The image sensor may further include an optical shield 30 positioned on the substrate 10 and defining a boundary of each photosensitive device of the image sensor, and the optical shield 30 may form an optical shield between each photosensitive device of the image sensor to reduce interference of incident light with adjacent photosensitive devices.

In order to improve the light sensitivity, the related art image sensor further includes a microlens 40 formed above the photodiode 11 using a material having good light transmittance. The upper surface of the microlens 40 is in an arc shape convex upward so that the transmission path of the incident light is changed to be converged toward the center, thereby allowing more light to enter the region of the photodiode 11.

The inventors of the present application have studied to find that in the image sensor of the related art, even though the microlens 40 has been used to concentrate the incident light toward the center as shown in fig. 2, a part of the light is incident to the peripheral region 12 around the photodiode 11 in the substrate 10, as shown by the transmission paths of the light indicated by the broken lines L21, L22 in fig. 2.

The inventors of the present application have studied and found that as the amount of light received by the photodiode increases, the light sensitivity of the image sensor also improves. Since the surrounding area 12 cannot be used to sense light, it is desirable to further reduce the light entering the surrounding area 12 while increasing the light entering the area of the photodiode 11.

Various exemplary embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, the numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present disclosure unless specifically stated otherwise.

The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses.

Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.

In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.

Reference in the present disclosure to "one embodiment" or "an embodiment" means that a feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrase "in one embodiment" appearing in various places throughout the disclosure are not necessarily all referring to the same embodiment. Furthermore, the features, structures, or characteristics may be combined in any suitable combination and/or sub-combination in one or more embodiments.

Fig. 3, 5, 6, and 8 schematically illustrate the structure of an image sensor of an exemplary embodiment of the present disclosure and a transmission path of light therein, respectively, in the form of cross-sectional views. Although only one photosensitive device is illustrated in the drawings as an example, the image sensor of one exemplary embodiment of the present disclosure includes a plurality of photosensitive devices, and in general, the plurality of photosensitive devices may form an array. Since each photosensitive device in an image sensor may take the same configuration, only one photosensitive device is shown and described herein in order to avoid obscuring the present invention.

As shown in fig. 3, the image sensor includes a substrate 10 and a light-condensing portion 50.

In some embodiments, the substrate 10 may be a semiconductor substrate made of any semiconductor material suitable for semiconductor devices (such as Si, SiC, SiGe, etc.), which may be an intrinsic semiconductor material or a semiconductor material doped with impurities. In other embodiments, the substrate 10 may be a silicon-on-insulator (SOI), silicon germanium-on-insulator (sige-on-insulator (sige-on-insulator) or other composite substrate. It will be understood by those skilled in the art that the substrate is not subject to any limitations, but may be selected according to the actual application. A photodiode 11 is formed in the substrate 10 for sensing light. In the substrate 10, there is also a region 12 (referred to as "surrounding region" in the present disclosure) around the photodiode 11, and devices, circuits, and the like that convert sensed light into an electrical signal are generally formed.

The light-condensing portion 50 is located on the substrate 10 and has a slope, for example, a slope A, B in fig. 3 and a slope C, D in fig. 6. The light-condensing portion 50 is configured to: light to enter the peripheral region 12 around the photodiode 11 is caused to enter the light-condensing portion 50 from the inclined surface A, B or C, D, and is refracted toward the photodiode 11.

In some embodiments, as shown in fig. 3, the light-condensing portion 50 coincides with the photodiode 11 in a plan view parallel to the main surface of the substrate 10. That is, the projection of the light-condensing portion 50 on a plane parallel to the main surface of the substrate 10 and the projection of the photodiode 11 on the plane coincide. As will be appreciated by those skilled in the art, registration includes partial registration and full registration. The slope A, B (i.e., the side surface of the light-concentrating portion 50) slopes downward and outward, i.e., extends downward in the vertical direction from the top surface of the light-concentrating portion 50 (or from the apex or top edge of the light-concentrating portion 50 in the case where the light-concentrating portion 50 does not have a top surface as shown in fig. 3), and outward in the horizontal direction (i.e., in a direction away from the photodiode 11). The bottom edge of ramp A, B is located within the surrounding region 12 and the top edge or apex of ramp A, B is located above the boundary of photodiode 11 or above the region of photodiode 11. It will be understood by those skilled in the art that "inclined surface" refers to an inclined surface, not only a plane surface, but also an inclined surface such as a conical surface. Preferably, the slope of the light-condensing portion 50 in the present disclosure is a straight line in a sectional view of the image sensor.

The light-condensing portion 50 having the above-described structure causes light (refer to transmission paths of light indicated by broken lines L21, L22 in fig. 2) that originally (i.e., when the image sensor does not include the light-condensing portion 50) to enter the surrounding region 12 around the photodiode 11 to enter the light-condensing portion 50 from the inclined surface A, B and refract the light toward the photodiode 11, as indicated by broken lines L31, L32 in fig. 3, so that more light is sensed by the photodiode 11, thereby improving the light sensitivity of the image sensor.

Although the cross-sectional shape of the light-condensing portion 50 shown in fig. 3 is a trapezoid, those skilled in the art will appreciate that the cross-sectional shape of the light-condensing portion 50 may be other polygons (e.g., a triangle), a figure having an arc (e.g., replacing the upper surface of the light-condensing portion 50 shown in fig. 3 with an arc), or the like, as long as the light-condensing portion 50 has an inclined surface and can refract light entering the light-condensing portion 50 from the inclined surface toward the photodiode 11.

Fig. 4a is a schematic diagram schematically showing one example of a transmission path of light at the slope B in fig. 3. In the drawing, a thick black line indicates an interface between two light transmission media (i.e., a slope B shown in fig. 3), a solid line with an arrow indicates a transmission path of light in the two transmission media, a dot-dash line indicates a normal line, and a dotted line is an extension of a transmission direction of incident light. In some embodiments, as shown in fig. 3, in order to achieve the effect of refracting the light entering the light-gathering portion 50 from the inclined surface A, B toward the photodiode 11, it is necessary to make the refractive index of the light-gathering portion 50 (or at least the portion of the light-gathering portion 50 near the inclined surface A, B) greater than the refractive index of the portion above and in contact with the inclined surface A, B. In this way, when light enters the light-gathering part 50 from the inclined plane B and is refracted, as shown in fig. 4a, since the light enters the optically denser medium from the optically thinner medium, the refraction angle r1 is smaller than the incident angle i1, so that the transmission path of the incident light is changed to be deflected inward (i.e., toward the photodiode 11), so that more light enters the photodiode 11, thereby improving the light sensitivity of the image sensor. Although fig. 4a shows only one example of the transmission path of light at the slope B, those skilled in the art will appreciate that the transmission path of light at the slope a is similar to that shown in fig. 4 a.

Fig. 4b is a schematic view schematically showing one example of the transmission path of light at the interface E in fig. 3. In this case, a thick black line indicates an interface between two light transmission media (i.e., interface E shown in fig. 3), a solid line with an arrow indicates a transmission path of light in the two transmission media, a dot-dash line indicates a normal line, and a dotted line is an extension of a transmission direction of incident light. In some embodiments, in order to prevent light entering the substrate 10 from the light-condensing portion 50 from being diffused outward, so that the light sensitivity of the image sensor is further improved, the refractive index of the light-condensing portion 50 (or at least the portion of the light-condensing portion 50 in contact with the substrate 10) is greater than or equal to the refractive index of the substrate 10 (or at least the portion of the substrate 10 in contact with the light-condensing portion 50). If the refractive index of the light-condensing portion 50 is equal to the refractive index of the substrate 10 (or at least the portion of the substrate 10 in contact with the light-condensing portion 50), the transmission path of light is not changed when light enters the substrate 10 from the light-condensing portion 50, i.e., light continues to be transmitted toward the photodiode 11 as described above, as shown in fig. 3. If the refractive index of the light-condensing portion 50 is greater than that of the substrate 10 (or at least the portion of the substrate 10 in contact with the light-condensing portion 50), as shown in fig. 4b, when light enters the substrate 10 from the light-condensing portion 50, since the light enters the optically thinner medium from the optically denser medium, the refraction angle r2 is greater than the incident angle i2, so that the transmission path of the incident light is changed to be deflected inward, and more light can enter the photodiode 11 compared to the image sensor shown in fig. 3, so that the light sensitivity of the image sensor is further improved. Although fig. 4B shows only one example of the transmission path of the light of the portion of the interface E located under the slope B, those skilled in the art will appreciate that the transmission path of the light of each portion of the interface E of the light-concentrating part 50 and the substrate 10 (e.g., the portion of the interface E located under the slope a) is similar to that shown in fig. 4B.

In some embodiments, as shown in fig. 3, the light-gathering portion 50 may be in contact with the substrate 10, that is, there is no other light transmission medium between the light-gathering portion 50 and the substrate 10, so that the light refracted by the light-gathering portion 50 directly passes through the interface E between the light-gathering portion 50 and the substrate 10, and does not pass through the interface of the other two light transmission media, thereby preventing the light refracted by the light-gathering portion 50 toward the photodiode 11 from being subjected to excessive refraction or reflection to change the transmission path of the light.

In some embodiments, the surface of the light-condensing portion 50 may be formed with an anti-reflection coating so that more light can enter the light-condensing portion 50 instead of being reflected off the surface thereof so that more light enters the photodiode 11, thereby enabling the light sensitivity of the image sensor to be further improved.

In some embodiments, as shown in fig. 5, the image sensor may include a filling layer 20 in addition to the substrate 10 and the light-condensing part 50 described in the above embodiments. The filling layer 20 is located above the light-condensing portion 50 and covers the surface of the light-condensing portion 50. As described above, in order to obtain the effect of refracting light entering the light-condensing portion 50 from the inclined surface of the light-condensing portion 50 toward the photodiode 11, the refractive index of the light-condensing portion 50 (or at least the portion of the light-condensing portion 50 near the inclined surface) needs to be larger than the refractive index of the filling layer 20 (or at least the portion of the filling layer 20 in contact with the light-condensing portion 50). In this manner, when light enters the light-condensing portion 50 from the inclined surface of the light-condensing portion 50 and is refracted, the transmission path of the incident light is changed to be deflected inward as shown by the transmission path of the light indicated by the dotted line L51, and thus, more light can be caused to enter the photodiode 11, thereby improving the light sensitivity of the image sensor.

In some embodiments, the filling layer 20 has a color filtering function to allow light of a specific wavelength range to pass through to enter the photodiode 11. The filling layer 20 having a color filtering function may be made of a pigment or dye material that allows light of some wavelengths to pass through. In some embodiments, red, blue, or green light may be allowed to pass. In other embodiments, cyan, yellow, or magenta light may be allowed to pass. However, these are only exemplary colors that can be filtered by the filling layer 20 with color filtering function, and those skilled in the art will understand that the filling layer 20 with color filtering function in the present disclosure may also allow other colors of light to pass through. In addition, the filling layer 20 having the color filtering function may be made of other materials, such as a light reflecting material capable of reflecting light of a specific wavelength.

In some embodiments, the fill layer 20 has the function of providing a flat upper surface for the structures located thereon. The filling layer 20 may be formed of a dielectric material, for example, oxide or nitride, etc.

In some embodiments, as shown in fig. 5, the image sensor may include an optical shield 30 in addition to the substrate 10 and the light-condensing portion 50 described in the above embodiments. The optical shielding part 30 is located on the substrate 10 and defines a boundary of each photosensitive device of the image sensor, thereby forming an optical shield between each photosensitive device of the image sensor to reduce interference of incident light to adjacent photosensitive devices. In some embodiments, the optical shield 30 is formed of a light reflective material. In some embodiments, the optical shield 30 may be formed of a metallic material, such as tungsten or copper.

The optical shield portion 30 reflects light (transmission path of light shown by a broken line L52) that reaches its surface (particularly, the side surface of the optical shield portion 30) inward, enabling more light to reach the photodiode 11. Further, with respect to light that has been reflected by the optical shielding portion 30 and still has failed to reach the region of the photodiode 11, the transmission path thereof upon incidence to the light condensing portion 50 is further deflected inward as indicated by the broken line L52, thereby further increasing the possibility that light can reach the photodiode 11. It can be seen that the light-condensing portion 50 can cooperate with the optical shielding portion 30 to allow more light to enter the photodiode 11 than the image sensor shown in fig. 3, thereby further improving the light sensitivity of the image sensor.

In some embodiments, the outer edge of the light gathering portion 50 is in contact with the optical shielding portion 30, as shown in fig. 5. This makes it possible to avoid as much as possible that light to be incident on the peripheral region 12 does not directly enter the substrate 10 through the light condensing portion 50, thereby increasing the possibility that light can reach the photodiode 11, so that more light can be incident on the photodiode 11.

In some embodiments, the height of the light-condensing portion 50 is less than or equal to the height of the optical shielding portion 30, as shown in fig. 5, to ensure the optical shielding effect of the optical shielding portion 30.

In some embodiments, as shown in fig. 5, the image sensor may further include a microlens 40 positioned above the photodiode 11, in addition to the substrate 10 and the light-condensing portion 50 described in the above embodiments. For those light which have passed through the area where the light condensed by the microlens 40 still cannot reach the photodiode 11, the transmission path thereof is further deflected inward upon incidence to the condensing portion 50, as indicated by the transmission path of the light indicated by the broken line L51, thereby further increasing the possibility that the light can reach the photodiode 11. It can be seen that the light-condensing portion 50 may cooperate with the microlens 40, enabling more light to enter the photodiode 11 than the image sensor shown in fig. 3, thereby enabling the light sensitivity of the image sensor to be further improved.

In some embodiments, as shown in fig. 6, the light-condensing portion 50 coincides with the peripheral region 12 in a plan view parallel to the main surface of the substrate 10. That is, the projection of the light-condensing portion 50 on a plane parallel to the main surface of the substrate 10 coincides with the projection of the peripheral region 12 on the plane. As will be appreciated by those skilled in the art, registration includes partial registration and full registration. The slope C, D (i.e., the side surface of the light-concentrating portion 50) slopes downward and inward, i.e., starting from the apex or top edge of the light-concentrating portion 50 (or, in the case where the light-concentrating portion 50 does not have an apex or top edge as shown in fig. 6, from the top surface of the light-concentrating portion 50), extending downward in the vertical direction, and extending inward in the horizontal direction. The bottom edge of ramp C, D is located at the boundary of photodiode 11 (not shown) or within the area of photodiode 11 (as shown in fig. 6), and the top edge or apex of ramp C, D is located above the surrounding area 12. It will be understood by those skilled in the art that "inclined surface" refers to an inclined surface, not only a plane surface, but also an inclined surface such as a conical surface. Preferably, the slope of the light-condensing portion 50 in the present disclosure is a straight line in a sectional view of the image sensor.

The light-condensing portion 50 having the above-described structure causes light (refer to transmission paths of light indicated by broken lines L21, L22 in fig. 2) that originally (i.e., when the image sensor does not include the light-condensing portion 50) to enter the surrounding region 12 around the photodiode 11 to enter the light-condensing portion 50 from the inclined surface C, D and refract the light toward the photodiode 11, as indicated by broken lines L61, L62 in fig. 6, so that more light is sensed by the photodiode 11, thereby improving the light sensitivity of the image sensor.

Although the cross-sectional shape of the light-condensing portion 50 shown in fig. 6 is a triangle, it will be understood by those skilled in the art that the cross-sectional shape of the light-condensing portion 50 may be other polygons (e.g., a trapezoid, etc.), as long as the light-condensing portion 50 has an inclined surface and can refract light entering the light-condensing portion 50 from the inclined surface toward the photodiode 11.

Fig. 7a is a schematic diagram schematically showing one example of a transmission path of light at the slope D in fig. 6. In this case, a thick black line indicates an interface between two light transmission media (i.e., a slope D shown in fig. 6), a solid line with an arrow indicates a transmission path of light in the two transmission media, a dot-dash line indicates a normal line, and a dotted line is an extension of a transmission direction of incident light. In some embodiments, as shown in fig. 6, in order to achieve the effect of refracting the light entering the light-condensing portion 50 from the inclined surface C, D toward the photodiode 11, it is necessary to make the refractive index of the light-condensing portion 50 (or at least the portion of the light-condensing portion 50 near the inclined surface C, D) smaller than the refractive index of the portion above the inclined surface C, D in contact therewith. In this way, when light enters the light-gathering part 50 from the inclined plane D and is refracted, as shown in fig. 7a, since the light enters the optically thinner medium from the optically denser medium, the refraction angle r3 is larger than the incident angle i3, so that the transmission path of the incident light is changed to be deflected inward, so that more light enters the photodiode 11, thereby improving the light sensitivity of the image sensor. Although fig. 7a shows only one example of the transmission path of light at the slope D, those skilled in the art will appreciate that the transmission path of light at the slope C is similar to that shown in fig. 7 a.

Fig. 7b is a schematic view schematically showing one example of the transmission path of light at the interface E in fig. 6. In this case, a thick black line indicates an interface between two light transmission media (i.e., interface E shown in fig. 6), a solid line with an arrow indicates a transmission path of light in the two transmission media, a dot-dash line indicates a normal line, and a dotted line is an extension of a transmission direction of incident light. In some embodiments, in order to prevent light entering the substrate 10 from the light-condensing portion 50 from being diffused outward, so that the light sensitivity of the image sensor is further improved, the refractive index of the light-condensing portion 50 (or at least the portion of the light-condensing portion 50 in contact with the substrate 10) is greater than or equal to the refractive index of the substrate 10 (or at least the portion of the substrate 10 in contact with the light-condensing portion 50). If the refractive index of the light-condensing portion 50 is equal to the refractive index of the substrate 10 (or at least the portion of the substrate 10 in contact with the light-condensing portion 50), the transmission path of light is not changed when light enters the substrate 10 from the light-condensing portion 50, i.e., light continues to be transmitted toward the photodiode 11 as described above, as shown in fig. 6. If the refractive index of the light-condensing portion 50 is greater than that of the substrate 10 (or at least the portion of the substrate 10 in contact with the light-condensing portion 50), as shown in fig. 7b, when light enters the substrate 10 from the light-condensing portion 50, since the light enters the optically thinner medium from the optically denser medium, the refraction angle r4 is greater than the incident angle i4, so that the transmission path of the incident light is changed to be deflected inward, and more light can enter the photodiode 11 compared to the image sensor shown in fig. 6, so that the light sensitivity of the image sensor is further improved. Although fig. 7b shows only one example of the transmission path of the light of the portion of the interface E located under the slope D, those skilled in the art will appreciate that the transmission path of the light of each portion of the interface E of the light-concentrating part 50 and the substrate 10 (e.g., the portion of the interface E located under the slope C) is similar to that shown in fig. 7 b.

In some embodiments, as shown in fig. 6, the light-gathering portion 50 may be in contact with the substrate 10, that is, there is no other light transmission medium between the light-gathering portion 50 and the substrate 10, so that the light refracted by the light-gathering portion 50 directly passes through the interface E between the light-gathering portion 50 and the substrate 10, and does not pass through the interfaces of the other two light transmission media, thereby preventing the light refracted by the light-gathering portion 50 toward the photodiode 11 from being subjected to excessive refraction or reflection to change the transmission path of the light.

In some embodiments, as shown in fig. 8, the image sensor may include a filling layer 20 in addition to the substrate 10 and the light-condensing part 50 described in the above embodiments. The filling layer 20 is located above the light-condensing portion 50 and covers the surface of the light-condensing portion 50. As described above, in order to obtain the effect of refracting light entering the light-condensing portion 50 from the inclined surface of the light-condensing portion 50 toward the photodiode 11, the refractive index of the light-condensing portion 50 (or at least the portion of the light-condensing portion 50 near the inclined surface) needs to be smaller than the refractive index of the filling layer 20 (or at least the portion of the filling layer 20 in contact with the light-condensing portion 50). In this manner, when light enters the light-condensing portion 50 from the inclined surface of the light-condensing portion 50 and is refracted, the transmission path of the incident light is changed to be deflected inward as shown by the transmission path of the light indicated by the dotted line L81, and thus, more light can be caused to enter the photodiode 11, thereby improving the light sensitivity of the image sensor.

In some embodiments, the filling layer 20 has a color filtering function to allow light of a specific wavelength range to pass through to enter the photodiode 11. In some embodiments, the fill layer 20 has the function of providing a flat upper surface for the structures located thereon. The characteristics of the filling layer 20 having a color filtering function or a function of providing a flat upper surface for a structure located thereon are similar to those described above, and thus a detailed description thereof is omitted herein.

In some embodiments, as shown in fig. 8, the image sensor may include an optical shield 30 in addition to the substrate 10 and the light-condensing portion 50 described in the above embodiments. The position, function, and material of the optical shielding part 30 are similar to those described above, so a detailed description thereof is omitted here.

The optical shield portion 30 reflects light (transmission path of light shown by a broken line L82) that reaches its surface (particularly, the side surface of the optical shield portion 30) inward, enabling more light to reach the photodiode 11. Further, for those light that still cannot reach the region of the photodiode 11 by refraction by the light-condensing portion 50, the light is reflected inward upon reaching the surface of the optical shielding portion 30 to further deflect its transmission path inward as shown by the broken line L82, thereby further increasing the possibility that the light can reach the photodiode 11. It can be seen that the light-condensing portion 50 can cooperate with the optical shielding portion 30 to allow more light to enter the photodiode 11 than the image sensor shown in fig. 6, thereby allowing the light sensitivity of the image sensor to be further improved.

In some embodiments, the outer edge of the light gathering portion 50 is in contact with the optical shielding portion 30, as shown in fig. 8. This makes it possible to avoid as much as possible that light to be incident on the peripheral region 12 does not directly enter the substrate 10 through the light condensing portion 50, thereby increasing the possibility that light can reach the photodiode 11, so that more light can be incident on the photodiode 11.

In some embodiments, the height of the light-condensing portion 50 is less than or equal to the height of the optical shielding portion 30, as shown in fig. 8, to ensure the optical shielding effect of the optical shielding portion 30.

In some embodiments, as shown in fig. 8, the image sensor may further include a microlens 40 positioned above the photodiode 11, in addition to the substrate 10 and the light-condensing portion 50 described in the above embodiments. For those light which have passed through the area where the light condensed by the microlens 40 still cannot reach the photodiode 11, the transmission path thereof is further deflected inward upon incidence to the condensing portion 50, as indicated by the transmission path of the light indicated by the broken line L81, thereby further increasing the possibility that the light can reach the photodiode 11. It can be seen that the light-condensing portion 50 may cooperate with the microlens 40 to allow more light to enter the photodiode 11 than the image sensor shown in fig. 6, thereby allowing the light sensitivity of the image sensor to be further improved.

In some embodiments, the image sensor shown in FIG. 5 may be formed in the following manner. This is described in detail below in conjunction with fig. 9a to 9 f. It will be appreciated by those skilled in the art that the steps in the following description are merely illustrative, and that one or more steps or processes may be omitted or added depending on the application.

As shown in fig. 9a, in some embodiments, a method for forming an image sensor includes providing a substrate 10 having a photodiode 11. The structure and type of the photodiode 11 are not limited, and the photodiode 11 may be a PN junction type photodiode, for example. A peripheral region 12 is also formed around the photodiode 11 in the substrate 10, and devices, circuits, and the like that convert light sensed by the photodiode 11 into an electrical signal may be formed in the peripheral region 12.

As shown in fig. 9b, an optical shield 30 is formed on the substrate 10 at the boundary defining each photosensitive device in the image sensor. In some embodiments, the optical shielding 30 may be a metal grid formed of a metal material. In some embodiments, the metal grid may be formed by patterning a deposited metal layer. In other embodiments, the metal grid may be formed by patterning a deposited or grown non-metal layer (e.g., a layer of semiconductor material or a layer of dielectric material) and then forming a metal film on the side surfaces (at least the side surfaces, and possibly also the top surface) of the patterned non-metal layer.

As shown in fig. 9c, a first material layer 51 is formed on the substrate 10. The first material is capable of transmitting light (e.g., the first material may be Si, SiO)₂Etc.) and the refractive index of the first material is largeIs equal to or higher than the refractive index of the portion of the substrate 10 in contact therewith. The first material layer 51 may be formed by, for example, Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD), Atomic Layer Deposition (ALD), or other suitable techniques. In order to avoid or mitigate adverse effects on the already-formed optical shield 30 or other portions of the image sensor when the first material layer 51 is formed, the process temperature is controlled to be less than or equal to 700 degrees celsius at the time of the process of forming the first material layer 51.

As shown in fig. 9d, the first material layer 51 is patterned to form the light-condensing portion 50, and the height of the formed light-condensing portion 50 is less than or equal to the height of the optical shielding portion 50. In some embodiments, patterning the first material layer 51 to form the light-condensing portion 50 is performed by an etching process. Wherein the light condensing portion 50 has a slope, and the light condensing portion 50 is configured to: light entering the peripheral region 12 around the photodiode 11 is caused to enter the light-condensing portion 50 from the inclined surface, and is refracted in the direction of the photodiode 11. After the light-condensing portion 50 is formed, an anti-reflection coating (not shown) may also be formed on the surface of the light-condensing portion 50.

As shown in fig. 9e, the filling layer 20 is formed on the light-condensing portion 50 such that the filling layer 20 covers the surface of the light-condensing portion 50. The fill layer 20 may be formed by, for example, Chemical Vapor Deposition (CVD), Physical Vapor Deposition (PVD), Atomic Layer Deposition (ALD), or other suitable techniques. The filling layer 20 is capable of transmitting light so as to allow incident light to enter the light-condensing portion 50. The material of the filling layer 20 can be selected and the thickness of the filling layer 20 can be controlled to make the filling layer 20 transparent. In some embodiments, the fill layer 20 may have a color filtering function. In other embodiments, the fill layer 20 may be formed of a dielectric material. In the case of the configuration of the light-condensing portion 50 as illustrated in fig. 9e, 3, and 5, the material of the filling layer 20 is selected so that the refractive index of the filling layer 20 is smaller than the refractive index of the light-condensing portion 50. In the case of the configuration of the light-condensing portion 50 as illustrated in fig. 6 and 8, the material of the filling layer 20 is selected such that the refractive index of the filling layer 20 is larger than the refractive index of the light-condensing portion 50.

As shown in fig. 9f, a microlens 40 is formed for each photosensitive device of the image sensor. The microlens 40 is located above the photodiode 11. Although fig. 9f shows a photosensitive device of an image sensor in which the microlenses 40 are formed over the filling layer 20 and the optical shielding part 30, those skilled in the art will appreciate that the microlenses 40 may be formed over the light-condensing part 50 or over the substrate 10 in the case where the image sensor does not include the filling layer 20 or the optical shielding part 30, such as the case shown in fig. 3 or 6.

Although the above methods are described and illustrated in connection with fig. 9 a-9 f for the image sensor shown in fig. 5, it is understood that image sensors having other configurations, such as the image sensors shown in fig. 3, 6, or 8, may be formed by methods similar to the above methods.

Although the structure of the image sensor of the pixel region is schematically illustrated in the drawings of the present disclosure in the form of a cross-sectional view, a person skilled in the art can obtain the structure and the forming method of the entire image sensor related to the present disclosure based on the content of the present disclosure.

In the specification and claims, the word "a or B" includes "a and B" and "a or B" rather than exclusively including only "a" or only "B" unless specifically stated otherwise.

The terms "front," "back," "top," "bottom," "over," "under," and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the disclosure described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.

As used herein, the word "exemplary" means "serving as an example, instance, or illustration," and not as a "model" that is to be replicated accurately. Any implementation exemplarily described herein is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, the disclosure is not limited by any expressed or implied theory presented in the preceding technical field, background, brief summary or the detailed description.

As used herein, the term "substantially" is intended to encompass any minor variation resulting from design or manufacturing imperfections, device or component tolerances, environmental influences, and/or other factors. The word "substantially" also allows for differences from a perfect or ideal situation due to parasitic effects, noise, and other practical considerations that may exist in a practical implementation.

The above description may indicate elements or nodes or features being "connected" or "coupled" together. As used herein, unless expressly stated otherwise, "connected" means that one element/node/feature is directly connected to (or directly communicates with) another element/node/feature, either electrically, mechanically, logically, or otherwise. Similarly, unless expressly stated otherwise, "coupled" means that one element/node/feature may be mechanically, electrically, logically, or otherwise joined to another element/node/feature in a direct or indirect manner to allow for interaction, even though the two features may not be directly connected. That is, coupled is intended to include both direct and indirect joining of elements or other features, including connection with one or more intermediate elements.

In addition, certain terminology may also be used in the following description for the purpose of reference only, and thus is not intended to be limiting. For example, the terms "first," "second," and other such numerical terms referring to structures or elements do not imply a sequence or order unless clearly indicated by the context.

It will be further understood that the terms "comprises/comprising," "includes" and/or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

In the present disclosure, the term "providing" is used broadly to encompass all ways of obtaining an object, and thus "providing an object" includes, but is not limited to, "purchasing," "preparing/manufacturing," "arranging/setting," "installing/assembling," and/or "ordering" the object, and the like.

Those skilled in the art will appreciate that the boundaries between the above described operations merely illustrative. Multiple operations may be combined into a single operation, single operations may be distributed in additional operations, and operations may be performed at least partially overlapping in time. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in various other embodiments. However, other modifications, variations, and alternatives are also possible. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

In addition, embodiments of the present disclosure may also include the following examples:

1. an image sensor, comprising:

a substrate having a photodiode formed therein; and

a light-condensing portion on the substrate, wherein the light-condensing portion has an inclined surface, and the light-condensing portion is configured to: so that light to enter a peripheral region of the photodiode enters the light-condensing portion from the slope and refracts the light toward the photodiode.

2. The image sensor according to claim 1,

the light-condensing portion and the photodiode coincide in a plan view parallel to the main surface of the substrate,

the bevel is inclined downward and outward, the bottom edge of the bevel is located in the surrounding area, and the top edge or vertex of the bevel is located above the boundary of the photodiode or above the area of the photodiode.

3. The image sensor according to claim 2, further comprising:

a filling layer located above the light-condensing portion and covering a surface of the light-condensing portion,

wherein the refractive index of the filling layer is smaller than that of the light-condensing portion.

4. The image sensor according to claim 1,

the light-condensing portion and the peripheral region coincide in a plan view parallel to the main surface of the substrate,

the bevel slopes downward and inward, the bottom edge of the bevel being located at the boundary of the photodiode or within the area of the photodiode, and the top edge or apex of the bevel being located above the surrounding area.

5. The image sensor of claim 4, further comprising:

wherein the refractive index of the filling layer is greater than that of the light-condensing portion.

6. The image sensor according to claim 3 or 5, wherein the filling layer has a color filtering function.

7. The image sensor according to claim 1, wherein a refractive index of the light-condensing portion is greater than or equal to a refractive index of a portion of the substrate in contact therewith.

8. The image sensor according to claim 1, wherein an antireflection coating is formed on a surface of the light-condensing portion.

9. The image sensor according to claim 1, further comprising:

an optical shielding portion located on the substrate and defining a boundary of each photosensitive device in the image sensor,

wherein an outer edge of the light-condensing portion is in contact with the optical shielding portion.

10. The image sensor of claim 9, wherein the height of the light-condensing portion is less than or equal to the height of the optical shielding portion.

11. The image sensor according to claim 1, further comprising:

a microlens located above the photodiode.

12. A method for forming an image sensor, comprising:

providing a substrate, wherein a photodiode is formed in the substrate;

forming a first material layer on the substrate; and

patterning the first material layer to form a light-condensing portion, wherein the light-condensing portion has a slope, and the light-condensing portion is configured to: so that light to enter a peripheral region of the photodiode enters the light-condensing portion from the slope and refracts the light toward the photodiode.

13. The method of claim 12, wherein the patterning of the first material layer to form the light concentrating portions is performed by an etching process.

14. The method of claim 13, wherein the first and second portions of the substrate are separated,

15. The method of claim 14, further comprising, after forming the light-concentrating portion:

forming a filling layer on the light-condensing portion, the filling layer covering a surface of the light-condensing portion,

wherein the filling layer has a refractive index less than that of the first material layer.

16. The method of claim 12, wherein the first and second portions of the substrate are separated,

17. The method of claim 16, further comprising, after forming the light-concentrating portion:

wherein the filling layer has a refractive index greater than that of the first material layer.

18. A method according to claim 15 or 17, wherein the fill layer has a colour filtering function.

19. The method of claim 12, wherein the first material layer has a refractive index greater than or equal to a refractive index of a portion of the substrate in contact therewith.

20. The method according to claim 12, further comprising, after forming the light-condensing portion:

and forming an anti-reflection coating on the surface of the light-gathering part.

21. The method of claim 12, further comprising, prior to forming the first material layer:

forming an optical shield on the substrate, the optical shield defining a boundary of each photosensitive device in the image sensor,

22. The method of claim 21, wherein the height of the light-gathering portion is less than or equal to the height of the optical shielding portion.

23. The method of claim 21, wherein the temperature at which the first material layer is formed is less than or equal to 700 degrees celsius.

24. The method of claim 12, further comprising forming a microlens over the photodiode after forming the light collection portion.

Although some specific embodiments of the present disclosure have been described in detail by way of example, it should be understood by those skilled in the art that the foregoing examples are for purposes of illustration only and are not intended to limit the scope of the present disclosure. The various embodiments disclosed herein may be combined in any combination without departing from the spirit and scope of the present disclosure. It will also be appreciated by those skilled in the art that various modifications may be made to the embodiments without departing from the scope and spirit of the disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. An image sensor, comprising:

a substrate having a photodiode formed therein;

a light-condensing portion on the substrate, wherein the light-condensing portion has an inclined surface, and the light-condensing portion is configured to: causing light to enter a surrounding area of the photodiode to enter the light-condensing portion from the slope; and

a filling layer that is located above the light-condensing portion and covers a surface of the light-condensing portion, and that has a color filtering function, wherein refractive indices of the filling layer and the light-condensing portion are configured to: so that the light entering the light-condensing portion from the inclined surface is deflected toward the photodiode.

2. The image sensor of claim 1,

3. The image sensor of claim 2, wherein the filling layer has a refractive index smaller than a refractive index of the light-condensing portion.

4. The image sensor of claim 1,

5. The image sensor of claim 4, wherein the filling layer has a refractive index greater than a refractive index of the light-condensing portion.

6. The image sensor according to claim 1, wherein a refractive index of the light-condensing portion is greater than or equal to a refractive index of a portion of the substrate in contact therewith.

7. The image sensor according to claim 1, wherein a surface of the light-condensing portion is formed with an antireflection coating.

8. The image sensor of claim 1, further comprising:

9. The image sensor of claim 8, wherein the height of the light-condensing portion is less than or equal to the height of the optical shielding portion.

10. The image sensor of claim 1, further comprising:

a microlens located above the photodiode.

11. A method for forming an image sensor, comprising:

providing a substrate, wherein a photodiode is formed in the substrate;

forming a first material layer on the substrate;

patterning the first material layer to form a light-condensing portion, wherein the light-condensing portion has a slope, and the light-condensing portion is configured to: causing light to enter a surrounding area of the photodiode to enter the light-condensing portion from the slope; and

forming a filling layer on the light-condensing portion, the filling layer covering a surface of the light-condensing portion and having a color filtering function, wherein refractive indexes of the filling layer and the light-condensing portion are configured to: so that the light entering the light-condensing portion from the inclined surface is deflected toward the photodiode.

12. The method of claim 11, wherein the patterning of the first material layer to form the light concentrating portions is performed by an etching process.

13. The method of claim 12,

14. The method of claim 13, wherein the filler layer has a refractive index less than a refractive index of the first material layer.

15. The method of claim 11,

16. The method of claim 15, wherein the filler layer has a refractive index greater than a refractive index of the first material layer.

17. The method of claim 11, wherein the first material layer has a refractive index greater than or equal to a refractive index of a portion of the substrate in contact therewith.

18. The method of claim 11, further comprising, after forming the light-concentrating portion:

19. The method of claim 11, further comprising, prior to forming the first material layer:

20. The method of claim 19, wherein the height of the light-concentrating portion is less than or equal to the height of the optical shielding portion.

21. The method of claim 19, wherein the temperature at which the first material layer is formed is less than or equal to 700 degrees celsius.

22. The method of claim 11, further comprising forming a microlens over the photodiode after forming the light collection portion.