CN114388537A

CN114388537A - Image sensor and forming method thereof

Info

Publication number: CN114388537A
Application number: CN202011130962.0A
Authority: CN
Inventors: 任惠
Original assignee: Semiconductor Manufacturing International Shanghai Corp; Semiconductor Manufacturing International Beijing Corp
Current assignee: Semiconductor Manufacturing International Shanghai Corp; Semiconductor Manufacturing International Beijing Corp
Priority date: 2020-10-21
Filing date: 2020-10-21
Publication date: 2022-04-22

Abstract

The application provides an image sensor and a forming method thereof, wherein the image sensor comprises: the pixel structure comprises a semiconductor substrate, a first pixel region, a second pixel region, a third pixel region and an isolation structure for isolating the first pixel region, the second pixel region and the third pixel region; the dielectric layer is positioned on the surface of the semiconductor substrate and the surface of the isolation structure, wherein the thickness of the dielectric layer in the first pixel region, the thickness of the dielectric layer in the second pixel region and the thickness of the dielectric layer in the third pixel region are different; the metal grids are positioned on the surface of the dielectric layer, and the positions of the metal grids correspond to the positions of the isolation structures; the color filter layer is positioned on the surface of the medium layer and between the adjacent metal grids; and the micro lens is positioned on the color filter layer. The image sensor and the forming method thereof can improve the imaging quality of the image sensor.

Description

Image sensor and forming method thereof

Technical Field

The present disclosure relates to the field of image sensors, and more particularly, to an image sensor and a method for forming the same.

Background

An image sensor, also called a light-sensing element, is a functional device that converts an optical signal (optical image) on a light-sensing surface into an electrical signal using a photoelectric conversion function of an optoelectronic device, and is widely used in digital cameras and other electro-optical devices. Currently, Image sensors are mainly classified into three types, namely, a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor) and a CIS (Contact Image Sensor) Sensor: (1) the special process of the CCD ensures that the CCD has the advantages of good low-illumination effect, high signal-to-noise ratio, strong permeability, good color reduction capability and the like, and is widely applied to high-end technical elements such as camera shooting, transportation, medical treatment and the like; (2) the CMOS sensor adopts the most common CMOS process of a common semiconductor circuit, has the characteristics of high integration level, low power consumption, high speed, low manufacturing cost and the like, is mainly applied to products with lower influence on quality, but along with the continuous improvement of the process technology and the continuous reduction of the price of high-end CMOS, the CMOS sensor also gradually occupies more and more important positions in the fields of security industry, high-definition cameras and the like; (3) the CIS adopts a contact type photosensitive element (photosensitive sensor) to carry out photosensitive, 300-600 red, green and blue three-color LED (light emitting diode) sensors are tightly arranged together at a position 1-2 mm below a scanning platform to generate a white light source during scanning, complex mechanisms such as a CCD array, a lens, a fluorescent tube, a cold cathode ray tube and the like in the CCD scanner are replaced, and the light, the machine and the electricity of the CCD scanner are integrated into a machine and an electricity of the CIS scanner. The scanner made by CIS technology has the advantages of small volume, light weight, low production cost and the like, and is widely applied in the fields of fax machines, scanners, banknote sorting and changing and the like.

For image sensors, the optical transmittance of the pixel area directly affects the quality of the image. The current image sensor still has the problem of low optical transmittance of the pixel region, and therefore, a more effective and reliable technical solution is needed.

Disclosure of Invention

The application provides an image sensor and a forming method thereof, which can improve the optical transmittance of a pixel region of the image sensor so as to improve the imaging quality.

One aspect of the present application provides a method of forming an image sensor, including: providing a semiconductor substrate, wherein the semiconductor substrate comprises a first pixel region, a second pixel region, a third pixel region and an isolation structure for isolating the first pixel region, the second pixel region and the third pixel region; forming dielectric layers on the surface of the semiconductor substrate and the surface of the isolation structure, wherein the optical transmittance of the dielectric layer on the first pixel region to red light reaches a maximum value, the optical transmittance of the dielectric layer on the second pixel region to green light reaches a maximum value, and the optical transmittance of the dielectric layer on the third pixel region to blue light reaches a maximum value; forming a plurality of metal grids on the surface of the dielectric layer, wherein the positions of the metal grids correspond to the positions of the isolation structures; forming a color filter layer positioned between the adjacent metal grids on the surface of the dielectric layer; and forming a micro lens on the color filter layer.

In some embodiments of the present application, a thickness of the dielectric layer in the first pixel region, a thickness of the dielectric layer in the second pixel region, and a thickness of the dielectric layer in the third pixel region are all different.

In some embodiments of the present application, the first pixel region is a red pixel region, the second pixel region is a green pixel region, and the third pixel region is a blue pixel region, wherein a thickness of a dielectric layer of the first pixel region is greater than a thickness of a dielectric layer of the second pixel region, and a thickness of the dielectric layer of the second pixel region is greater than a thickness of the dielectric layer of the third pixel region.

In some embodiments of the present application, a method of forming the dielectric layers of different thicknesses includes: forming dielectric layers on the surface of the semiconductor substrate and the surface of the isolation structure; and etching the dielectric layers of the first pixel area, the second pixel area and the third pixel area to respectively reach the preset thickness.

In some embodiments of the present application, the method of forming an image sensor further includes: determining the dielectric layer thin film material; according to the light interference principle and the transmission principle in the thin film material, the thickness of a preset medium layer in the pixel area is calculated, namely the optimal thickness is calculated, so that the red light transmittance of the first pixel area reaches the maximum peak value, the green light transmittance of the second pixel area reaches the maximum peak value, and the blue light transmittance of the third pixel area reaches the maximum peak value.

In some embodiments of the present application, the dielectric layer of the first pixel region, the dielectric layer of the second pixel region, and the dielectric layer of the third pixel region are made of different materials, and the transmittance of each dielectric layer is calculated according to parameters such as a light refractive index, a light reflectance, and a light absorption rate of each dielectric layer.

In some embodiments of the present application, a method of forming the dielectric layer of different material includes: forming dielectric layers on the surface of the semiconductor substrate and the surface of the isolation structure; and carrying out first modification treatment on the dielectric layer on the first pixel region, such as: a first ion implantation process; and carrying out second modification treatment on the dielectric layer on the second pixel region, such as: a second ion implantation process; and performing third modification treatment on the dielectric layer on the third pixel region, such as: and (3) a third ion implantation process.

In some embodiments of the present application, the method of forming an image sensor further includes: and calculating the light transmittance of the dielectric layers in different pixel regions according to the light refractive index, the light reflectance and the light absorption rate of the dielectric layers, and calculating the ion implantation concentration by combining the thickness of the dielectric layers, thereby realizing the process.

In some embodiments of the present application, a method of forming the dielectric layer of different material includes: forming a first dielectric layer on the surface of the semiconductor substrate and the surface of the isolation structure, carrying out patterning treatment on the first dielectric layer, removing part of the first dielectric layer on the surface of the substrate and the surface of the isolation structure, and only leaving the first dielectric layer with a preset thickness in a first pixel area; forming a second dielectric layer on the surface of the semiconductor substrate, the surface of the isolation structure and the surface of the first pixel region, carrying out patterning treatment on the second dielectric layer, removing part of the second dielectric layer on the surface of the substrate, the surface of the isolation structure and the surface of the first pixel region, and only leaving the second dielectric layer with a preset thickness in the second pixel region; and forming a third dielectric layer on the surface of the semiconductor substrate, the surface of the isolation structure, the surfaces of the first pixel area and the second pixel area, carrying out patterning treatment on the third dielectric layer, removing partial third dielectric layers on the surface of the substrate, the surface of the isolation structure, the surfaces of the first pixel area and the second pixel area, and only leaving the third dielectric layer with a preset thickness in the third pixel area.

In some embodiments of the present application, the dielectric layer is a single layer structure or a multi-layer structure.

In some embodiments of the present application, the material of the dielectric layer includes silicon oxide, silicon nitride, or the like.

In some embodiments of the present application, a method of forming the number of metal grids comprises: forming a metal material layer on the surface of the dielectric layer; and etching the metal material layer to form the plurality of metal grids.

Another aspect of the present application provides an image sensor including: the pixel structure comprises a semiconductor substrate, a first pixel region, a second pixel region, a third pixel region and an isolation structure for isolating the first pixel region, the second pixel region and the third pixel region; the dielectric layer is positioned on the surface of the semiconductor substrate and the surface of the isolation structure, wherein the optical transmittance of the dielectric layer on the first pixel region to red light reaches the maximum value, the optical transmittance of the dielectric layer on the second pixel region to green light reaches the maximum value, and the optical transmittance of the dielectric layer on the third pixel region to blue light reaches the maximum value; the metal grids are positioned on the surface of the dielectric layer, and the positions of the metal grids correspond to the positions of the isolation structures; the color filter layer is positioned on the surface of the medium layer and between the adjacent metal grids; and the micro lens is positioned on the color filter layer.

In some embodiments of the present application, the first pixel region is a red pixel region, the second pixel region is a green pixel region, and the third pixel region is a blue pixel region, wherein an optical transmittance of the dielectric layer on the first pixel region to red light reaches a maximum peak value and is greater than optical transmittances to blue light and green light, an optical transmittance of the dielectric layer on the second pixel region to green light reaches a maximum peak value and is greater than optical transmittances to blue light and red light, and an optical transmittance of the dielectric layer on the third pixel region to blue light reaches a maximum peak value and is greater than optical transmittances to red light and green light.

In some embodiments of the present application, the dielectric layer is a single material or a combination of materials.

According to the image sensor and the forming method thereof, on one hand, different medium layer thicknesses can be designed for different color pixel areas, so that the light rays of the different color pixel areas can reach the optimal optical transmittance, and the imaging quality of the image sensor is improved; on the other hand, the dielectric layers with different refractive indexes can be designed for the pixel regions with different colors, so that the light rays of the pixel regions with different colors can reach the optimal optical transmittance, and the imaging quality of the image sensor is improved.

Drawings

The following drawings describe in detail exemplary embodiments disclosed in the present application. Wherein like reference numerals represent similar structures throughout the several views of the drawings. Those of ordinary skill in the art will understand that the present embodiments are non-limiting, exemplary embodiments and that the accompanying drawings are for illustrative and descriptive purposes only and are not intended to limit the scope of the present application, as other embodiments may equally fulfill the inventive intent of the present application. It should be understood that the drawings are not to scale. Wherein:

FIG. 1 is a schematic diagram of an image sensor;

fig. 2 to 12 are schematic structural diagrams of steps in a method for forming an image sensor according to some embodiments of the present application;

fig. 13 to fig. 24 are schematic structural diagrams of steps in a method for forming an image sensor according to other embodiments of the present application.

Detailed Description

The following description is presented to enable any person skilled in the art to make and use the present disclosure, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present application. Thus, the present application is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the claims.

The technical solution of the present invention will be described in detail below with reference to the embodiments and the accompanying drawings.

Fig. 1 is a schematic diagram of an image sensor.

Referring to fig. 1, the image sensor includes a semiconductor substrate 100, and the semiconductor substrate 100 includes a red pixel region 101, a green pixel region 102, a blue pixel region 103, and an isolation structure 110 for isolating the red pixel region 101, the green pixel region 102, and the blue pixel region 103. Photosensitive elements (not shown) such as photodiodes are formed in the red pixel region 101, the green pixel region 102, and the blue pixel region 103 for photoelectric conversion.

A dielectric layer 120 is formed on the semiconductor substrate 100, and a plurality of metal grids 130 and a color filter layer 140 located between the metal grids 130 are formed on the dielectric layer 120. The color filter layer 140 has a microlens 150 formed thereon.

The color filter layer 140 may be a filter including three types of red/green/blue, which can only transmit light with wavelengths corresponding to red, green, and blue. The presence of the filter structure enables each pixel to sense only one colour. For example, the color filter layer 140 on the red pixel region 101 is composed of a red filter; the color filter layer 140 on the green pixel region 102 is composed of a green filter; the color filter layer 140 on the blue pixel region 103 is composed of a blue filter.

In the image sensor, only light of one color (red, green, blue) enters the photosensitive element in each pixel region for photoelectric conversion due to the presence of the color filter layer 140. The wavelengths of different colors of light are different, the wavelength of red light is 605-700 nm, the wavelength of green light is 500-560 nm, and the wavelength of blue light is 450-480 nm, and the optical transmittances of the different wavelengths of light in different thicknesses or different media are different, so that the optical transmittances of the different wavelengths of light through the dielectric layer 120 are different. The thickness of the dielectric layer 120 is uniform, so that it is difficult to simultaneously make the optical transmittance of light with different wavelengths through the dielectric layer 120 meet the requirement, which may limit the light received by the pixel region, thereby affecting the imaging quality.

In view of the above problems, the present application provides an image sensor and a method for forming the same, which designs different dielectric layers for different color pixel regions, so that light rays of the different color pixel regions can achieve optimal optical transmittance, thereby improving the imaging quality of the image sensor. The optical transmittance of the dielectric layer for light depends on the thickness of the dielectric layer and the intrinsic characteristics (including refractive index, reflectivity, light absorption, etc.), so that the optical transmittance can be adjusted by adjusting the thickness of the dielectric layer and adjusting the intrinsic characteristics of the dielectric layer (e.g., using different materials or performing modification processes, respectively).

An embodiment of the present application provides a method of forming an image sensor, including: providing a semiconductor substrate, wherein the semiconductor substrate comprises a first pixel region, a second pixel region, a third pixel region and an isolation structure for isolating the first pixel region, the second pixel region and the third pixel region; forming dielectric layers on the surface of the semiconductor substrate and the surface of the isolation structure, wherein the optical transmittance of the dielectric layer on the first pixel region to red light reaches a maximum value, the optical transmittance of the dielectric layer on the second pixel region to green light reaches a maximum value, and the optical transmittance of the dielectric layer on the third pixel region to blue light reaches a maximum value; forming a plurality of metal grids on the surface of the dielectric layer, wherein the positions of the metal grids correspond to the positions of the isolation structures; forming a color filter layer positioned between the adjacent metal grids on the surface of the dielectric layer; and forming a micro lens on the color filter layer.

Fig. 2 to 12 are schematic structural diagrams of steps in a method for forming an image sensor according to some embodiments of the present application. A method for forming an image sensor according to an embodiment of the present application is described in detail below with reference to the accompanying drawings.

The refractive index can be adjusted by adjusting the thickness of the dielectric layer and the refractive index of the dielectric layer. In some embodiments of the present application, the optical transmittance of the dielectric layers of the different color pixel regions to the light of the corresponding color can reach a theoretical maximum value by adjusting the thicknesses of the dielectric layers of the different color pixel regions in a targeted manner.

Referring to fig. 2, a semiconductor substrate 200 is provided, and the semiconductor substrate 200 includes a first pixel region 201, a second pixel region 202, a third pixel region 203, and an isolation structure 210 for isolating the first pixel region 201, the second pixel region 202, and the third pixel region 203.

In some embodiments of the present application, the material of the semiconductor substrate 200 includes (i) an elemental semiconductor, such as silicon or germanium; (ii) a compound semiconductor such as silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, or the like; (iii) alloy semiconductors such as silicon germanium carbide, silicon germanium, gallium arsenide phosphide, or gallium indium phosphide, or the like; or (iv) combinations of the foregoing. In addition, the semiconductor substrate 200 may be doped (e.g., a P-type substrate or an N-type substrate). In some embodiments of the present application, the semiconductor substrate 200 may be doped with a P-type dopant (e.g., boron, indium, aluminum, or gallium) or an N-type dopant (e.g., phosphorus or arsenic).

In some embodiments of the present application, the semiconductor substrate 200 is divided into different pixel regions, for example, a red pixel region, a green pixel region, and a blue pixel region, as required.

In some embodiments of the present application, the first pixel region 201 is a red pixel region, the second pixel region 202 is a green pixel region, and the third pixel region 203 is a blue pixel region.

In each of the pixel regions, a photosensitive element (not shown) for converting a received optical signal into an electrical signal is formed.

In some embodiments of the present application, the photosensitive element may include a structure capable of performing photoelectric conversion, including but not limited to a photodiode. In some embodiments of the present application, the photodiodes are arranged in an array in the semiconductor substrate 200 for converting received optical signals into electrical signals. For example: the photodiodes are arranged in a Bayer (Bayer) array in the semiconductor substrate, but may be arranged in any other array as desired. In order to meet the requirement of thinning the total thickness of the semiconductor substrate 200, the photodiodes are located at substantially the same depth in the semiconductor substrate 200.

In some embodiments of the present application, the photodiode may be formed by performing an ion implantation process more than once in the semiconductor substrate 200. The doping type of the photodiode is opposite to that of the semiconductor substrate 200, for example, when the semiconductor substrate 200 is P-type doped, the photodiode is N-type doped.

In some embodiments of the present application, the isolation structure 210 is formed by filling an insulating material (e.g., silicon dioxide or silicon nitride, etc.) in a trench. The isolation structures 210 isolate adjacent pixel regions, so that light rays in the adjacent pixel regions are prevented from crosstalk, and further photon detection efficiency of each pixel region is improved.

Referring to fig. 3 and fig. 6 to 10, a dielectric layer 220 is formed on the surface of the semiconductor substrate 200 and the surface of the isolation structure 210, wherein the thickness of the dielectric layer 220 on the first pixel region 201, the thickness of the dielectric layer 220 on the second pixel region 202, and the thickness of the dielectric layer 220 on the third pixel region 203 are different.

In order to maximize the optical transmittance of light passing through the dielectric layer 220, in the method for forming the image sensor according to the embodiment of the application, different dielectric layer thicknesses are specially designed for different color pixel regions, so that the light of the different color pixel regions can reach the optimal optical transmittance, thereby improving the imaging quality of the image sensor. Specifically, the thicknesses of the dielectric layers in the pixel regions of different colors can be calculated according to the thin film interference principle and the fresnel formula, and the related calculation process will be described in detail later.

In some embodiments of the present disclosure, the first pixel region 201 is a red pixel region, the second pixel region 202 is a green pixel region, and the third pixel region 203 is a blue pixel region, wherein a thickness of the dielectric layer 220 on the first pixel region 201 is greater than a thickness of the dielectric layer 220 on the second pixel region 202, and a thickness of the dielectric layer 220 on the second pixel region 202 is greater than a thickness of the dielectric layer 220 on the third pixel region 203.

In other embodiments of the present application, the thicknesses of the dielectric layers on different pixel regions may have other size relationships, and the result is obtained according to the calculation result, and the selection may be determined according to actual situations.

In some embodiments of the present application, the method of forming the dielectric layer 220 with different thickness includes: forming a dielectric layer 220 on the surface of the semiconductor substrate 200 and the surface of the isolation structure 210; and etching the dielectric layer 220 of the first pixel region 201, the second pixel region 202 and the third pixel region 203 to reach a predetermined thickness respectively.

Referring to fig. 3, a dielectric layer 220 is formed on the surface of the semiconductor substrate 200 and the surface of the isolation structure 210.

In some embodiments of the present application, the method for forming the dielectric layer 220 includes a chemical vapor deposition process or a physical vapor deposition process.

In some embodiments of the present application, the material of the dielectric layer 220 includes silicon oxide or silicon nitride.

In some embodiments of the present application, the dielectric layer 220 is a single material or a combination of materials.

Referring to fig. 4 and 5, a plurality of metal grids 230 are formed on the surface of the dielectric layer 220, and the positions of the metal grids 230 correspond to the positions of the isolation structures 210. The positional correspondence means that a projection of the metal grid 230 in a vertical direction substantially coincides with a projection of the isolation structure 210 in the vertical direction.

Referring to fig. 4, a metal material layer 230a is formed on the surface of the dielectric layer 220.

In some embodiments of the present application, a method of forming the metal material layer 230a includes a chemical vapor deposition process or a physical vapor deposition process.

In some embodiments of the present application, the material of the metal material layer 230a includes aluminum or tungsten.

Referring to fig. 5, the metal material layer 230a is etched to form the metal grids 230. The metal grids 230 may prevent crosstalk of light rays in adjacent color filter layers, increase the amount of light rays entering a pixel region, and improve image quality.

In some embodiments of the present application, the etching includes dry etching or wet etching.

Referring to fig. 6, a first photoresist layer 241 is formed on the dielectric layer 220 on the first pixel region 201 and the third pixel region 203. Referring to fig. 7, the dielectric layer 220 on the second pixel region 202 is etched such that the thickness of the dielectric layer 220 on the second pixel region 202 is smaller than the thickness of the dielectric layer 220 on the first pixel region 201.

Referring to fig. 8, the first photoresist layer 241 is removed, and a second photoresist layer 242 is formed on the dielectric layer 220 on the first pixel region 201 and the second pixel region 202. Referring to fig. 9, the dielectric layer 220 on the third pixel region 203 is etched such that the thickness of the dielectric layer 220 on the third region 203 is smaller than the thickness of the dielectric layer 220 on the second pixel region 202. Referring to fig. 10, the second photoresist layer 242 is removed.

Referring to fig. 11, a color filter layer 240 is formed on the surface of the dielectric layer 220 between adjacent metal grids 230. The color filter layer 240 corresponds to positions of different pixel regions, and is used for passing light of a specific wavelength range to enter the photosensitive element. When the color filter layer 240 corresponds to pixel regions of different colors, the color filter layer 240 may be sequentially formed as needed.

In some embodiments of the present application, a red color filter layer may be sequentially formed on the first pixel region 201, a green color filter layer may be formed on the second pixel region 202, and a blue color filter layer may be sequentially formed on the third pixel region 203, respectively, according to division of corresponding pixel regions in the semiconductor substrate 200.

In some embodiments of the present application, the color filter layer 240 is formed of a resin to which an organic pigment is added inside. In addition, the color filter layer 240 may be made of other materials, such as a reflective material capable of reflecting light with a specific wavelength.

Referring to fig. 12, a microlens 250 is formed on the color filter layer 240. The micro lens 250 corresponds to a position of the color filter layer 240 and is disposed right above the color filter layer 240.

The microlens 250 is used to collect light for each pixel unit, and is made of, for example, a polystyrene resin, an acrylic resin, or a copolymer resin of these resins. The process for forming the microlens 250 may be any one of the existing microlens manufacturing processes, and is not described herein.

In some embodiments of the present application, the method of forming an image sensor further includes: determining the dielectric layer 220 thin film material; according to the light interference principle and the transmission principle in the thin film material, the thickness of a preset medium layer in the pixel area is calculated, namely the optimal thickness is calculated, so that the red light transmittance of the first pixel area reaches the maximum peak value, the green light transmittance of the second pixel area reaches the maximum peak value, and the blue light transmittance of the third pixel area reaches the maximum peak value. The calculation method of the optimal thickness of the dielectric layer corresponding to the pixel regions of different colors is described in detail below.

According to the thin film interference principle, the optical path difference between the reflected light passing through the dielectric layer and the reflected light on the surface of the dielectric layer is as follows:

δ＝2n₁d

wherein n is₁Is the refractive index of the dielectric layer and d is the thickness of the dielectric layer.

According to the thin film interference principle, the conditions for enhancing and weakening the interference are as follows:

when strengthened, delta is 2n₁d+(λ/2)＝kλ，(k＝1，2，3…)

When weakened, δ is 2n₁d+(λ/2)＝(2k-1)λ/2，(k＝1，2，3…)

Where λ is the wavelength of the incident light. Whether (lambda/2) is added to the formula depends on whether or not there is a half-wave loss. (lambda/2) is added when there is half-wave loss, and (lambda/2) is not added when there is no half-wave loss.

According to the Fresnel formula, the reflectivity of light entering the medium layer perpendicularly can be calculated:

wherein n is₀Is the refractive index, n, of the preceding layer of the incident light entering the dielectric layer₁Is the refractive index of the dielectric layer, n₂The refractive index of a layer after incident light enters the dielectric layer.

Is the phase difference of adjacent reflected beams.

Can be derived from δ:

according to the law of conservation of energy, the optical transmittance T can be obtained:

T＝1-R

according to the formula, the maximum optical transmittance of the light with different wavelengths in different media can be calculated. According to the formula, the maximum optical transmittance and the refractive index n of the medium layer can be found₁Refractive index n of color filter layer₀A refractive index n of the semiconductor substrate₂There is a relationship. Therefore, selection of appropriate dielectric layer materials, color filter materials, and semiconductor substrate materials can improve the optical transmittance of light.

The thickness of the medium at which the optical transmittance is highest can be obtained according to the following formula.

When no half-wave loss occurs:

minimum optical transmittance

Maximum optical transmittance

When half-wave loss occurs:

maximum optical transmittance

Minimum optical transmittance

In the embodiment of the application, the color filter layer material is PMMA, and the semiconductor substrate material is silicon as an example, so as to calculate the thickness of the dielectric layer in the pixel regions with different colors.

TABLE 1

	Blue light	Green light	Red light
				Wavelength/nm	450-480	500-560	605-700
Median wavelength/nm	460	530	650
				PMMA	1.4996	1.4938	1.4881
Silicon	4.5766	4.1602	3.8515

Table 1 shows the refractive index data for different materials in different colors of light.

TABLE 2

	Blue light	Green light	Red light
				Silicon oxide	1.4648	1.4608	1.4565
Minimum optical transmittance	72.58％	76.11％	78.87％
				Maximum optical transmittance	74.36％	77.76％	80.41％

Table 2 shows the refractive index of silicon oxide in light of different colors when the dielectric layer is silicon oxide, and the maximum optical transmittance and the minimum optical transmittance of light of different colors when PMMA passes through silicon oxide and enters silicon. The maximum optical transmittance and the minimum optical transmittance can be calculated by the thin film interference principle.

TABLE 3

	Blue light	Green light	Red light
				Silicon nitride	2.0751	2.0563	2.0374
Minimum optical transmittance	74.36％	77.76％	80.41％
				Maximum optical transmittance	94.74％	96.38％	97.44％

Table 3 shows the refractive index of silicon nitride in different colors of light when the dielectric layer is silicon nitride, and the maximum and minimum optical transmittances of different colors of light from PMMA through silicon nitride into silicon. The maximum optical transmittance and the minimum optical transmittance can be calculated by the thin film interference principle.

From the data in tables 2 and 3, it was found that the use of silicon nitride as the dielectric layer enables a greater optical transmittance of light than when silicon oxide is used.

Taking silicon nitride as an example, the thicknesses of the dielectric layers corresponding to the maximum optical transmittances of the different colors of light are calculated. In addition, a group of comparison groups are arranged, and the thicknesses of the dielectric layers of the pixel regions with different colors are consistent.

TABLE 4

Table 4 shows the corresponding thickness of the dielectric layer when the different pixel regions have the maximum optical transmittance, and the optical transmittance of the different regions when the thicknesses of the dielectric layers are the same. Referring to table 4, it can be seen that when the material of the dielectric layer is silicon nitride, the thickness of the dielectric layer corresponding to each pixel region of different color is selected as follows when the maximum optical transmittance is achieved. For example, when the thicknesses of the silicon nitride layers corresponding to the blue light, the green light and the red light are 3879A, 3222A and 2393A, respectively, the optical transmittances can reach 94.76%, 96.38% and 97.44%, respectively.

In addition, compared with the control group, if the thicknesses of the silicon nitride in different pixel areas are the same and are 277.1nm, the optical transmittances of blue light, green light and red light are 94.76%, 80.99% and 88.80%, respectively, and the optical transmittances of the green light and the red light are obviously lower. The silicon nitride with the same thickness can only ensure that the optical transmittance of the pixel region of one color reaches the optimum, and the optical transmittance of the pixel regions of other two colors is influenced.

It can be further found from table 4 that the thickness of the dielectric layer is not unique when the optical transmittance of light of each color reaches the maximum, and there may be several choices, for example, when the optical transmittance of blue light reaches 94.76%, the thicknesses of the dielectric layers may be 55.42nm, 166.26nm, 277.1nm and 387.93nm, and the optimal thickness of the dielectric layer may be chosen according to actual needs.

According to the forming method of the image sensor, different medium layer thicknesses are designed for the pixel areas with different colors, so that light rays of the pixel areas with different colors can achieve the optimal optical transmittance, and the imaging quality of the image sensor is improved.

An embodiment of the present application also provides an image sensor, referring to fig. 12, including: a semiconductor substrate 200, wherein the semiconductor substrate 200 comprises a first pixel region 201, a second pixel region 202, a third pixel region 203, and an isolation structure 210 for isolating the first pixel region 201, the second pixel region 202, and the third pixel region 203; a dielectric layer 220 located on the surface of the semiconductor substrate 200 and the surface of the isolation structure 210, wherein the thickness of the dielectric layer 220 on the first pixel region 201, the thickness of the dielectric layer 220 on the second pixel region 202, and the thickness of the dielectric layer 220 on the third pixel region 203 are different; a plurality of metal grids 230 located on the surface of the dielectric layer 220, wherein the positions of the metal grids 230 correspond to the positions of the isolation structures 210; a color filter layer 240 on the surface of the dielectric layer 220 and between adjacent metal grids 230; and a micro lens 250 on the color filter layer 240.

Referring to fig. 12, the semiconductor substrate 200 includes a first pixel region 201, a second pixel region 202, a third pixel region 203, and an isolation structure 210 for isolating the first pixel region 201, the second pixel region 202, and the third pixel region 203.

With reference to fig. 12, a dielectric layer 220 is formed on the surface of the semiconductor substrate 200 and the surface of the isolation structure 210, wherein the thickness of the dielectric layer 220 on the first pixel region 201, the thickness of the dielectric layer 220 on the second pixel region 202, and the thickness of the dielectric layer 220 on the third pixel region 203 are different.

In order to maximize the optical transmittance of light passing through the dielectric layer 220, in the image sensor according to the embodiment of the present application, different dielectric layer thicknesses are specially designed for different color pixel regions, so that the light of the different color pixel regions can reach the optimal optical transmittance, thereby improving the imaging quality of the image sensor. Specifically, the thicknesses of the dielectric layers of the pixel regions of different colors may be calculated according to the thin film interference principle and the fresnel formula.

With continued reference to fig. 12, a plurality of metal grids 230 are formed on the surface of the dielectric layer 220, and the positions of the metal grids 230 correspond to the positions of the isolation structures 210. The positional correspondence means that a projection of the metal grid 230 in a vertical direction substantially coincides with a projection of the isolation structure 210 in the vertical direction. The metal grids 230 may prevent crosstalk of light rays in adjacent color filter layers, increase the amount of light rays entering a pixel region, and improve image quality.

In some embodiments of the present application, the material of the metal grid 240 includes aluminum or tungsten, etc.

With continued reference to fig. 12, a color filter layer 240 is formed on the surface of the dielectric layer 220 between adjacent metal grids 230. The color filter layer 240 corresponds to positions of different pixel regions, and is used for passing light of a specific wavelength range to enter the photosensitive element. When the color filter layer 240 corresponds to pixel regions of different colors, the color filter layer 240 may be sequentially formed as needed.

With continued reference to fig. 12, a microlens 250 is formed on the color filter layer 240. The micro lens 250 corresponds to a position of the color filter layer 240 and is disposed right above the color filter layer 240.

The microlens 250 is used to collect light for each pixel unit, and is made of, for example, a polystyrene resin, an acrylic resin, or a copolymer resin of these resins.

According to the image sensor, different medium layer thicknesses are designed for different color pixel areas, so that light rays of the different color pixel areas can reach the optimal optical transmittance, and the imaging quality of the image sensor is improved.

Similarly, the optical transmittance can be adjusted by adjusting the thickness of the dielectric layer and adjusting the intrinsic characteristics of the dielectric layer. Therefore, in other embodiments of the present application, the optical transmittance of the dielectric layers in the pixel regions of different colors for the light of corresponding colors can also reach the theoretical maximum by specifically adjusting the intrinsic characteristics of the dielectric layers in the pixel regions of different colors (using different materials or performing modification treatment, etc.).

Fig. 13 to fig. 24 are schematic structural diagrams of steps in a method for forming an image sensor according to other embodiments of the present application. In this embodiment, the different ion implantation processes performed on the dielectric layer are only used as an exemplary embodiment, but this is not a limitation to the present application.

Referring to fig. 13, a semiconductor substrate 300 is provided, wherein the semiconductor substrate 300 includes a first pixel region 301, a second pixel region 302, a third pixel region 303, and an isolation structure 310 for isolating the first pixel region 301, the second pixel region 302, and the third pixel region 303.

In some embodiments of the present application, the semiconductor substrate 300 is divided into different pixel regions, for example, a red pixel region, a green pixel region, and a blue pixel region, as required.

In some embodiments of the present application, the first pixel region 301 is a red pixel region, the second pixel region 302 is a green pixel region, and the third pixel region 303 is a blue pixel region.

Referring to fig. 14 and 17 to 22, a dielectric layer 320 is formed on the surface of the semiconductor substrate 300 and the surface of the isolation structure 310, wherein the dielectric layer 320 on the first pixel region 301, the dielectric layer 320 on the second pixel region 302, and the dielectric layer 320 on the third pixel region 303 are made of different materials, and the optical transmittance of each dielectric layer is calculated according to parameters such as the optical refractive index, the optical reflectance, and the optical absorption of each dielectric layer.

In order to maximize the optical transmittance of light passing through the dielectric layer 320, in the forming method of the image sensor according to the embodiment of the application, the dielectric layers with different intrinsic characteristics are specially designed for the pixel regions with different colors, so that the light of the pixel regions with different colors can reach the optimal optical transmittance, and the imaging quality of the image sensor is improved.

Referring to fig. 14, a dielectric layer 320 is formed on the surface of the semiconductor substrate 300 and the surface of the isolation structure 310.

In some embodiments of the present application, the method for forming the dielectric layer 320 includes a chemical vapor deposition process or a physical vapor deposition process.

In some embodiments of the present application, the material of the dielectric layer 320 includes silicon oxide or silicon nitride.

In some embodiments of the present application, the dielectric layer 320 is a single material or a combination of materials.

Referring to fig. 15 and 16, a plurality of metal grids 330 are formed on the surface of the dielectric layer 320, and the positions of the metal grids 330 correspond to the positions of the isolation structures 310. The positional correspondence means that a projection of the metal grid 330 in a vertical direction substantially coincides with a projection of the isolation structure 310 in the vertical direction.

Referring to fig. 15, a metal material layer 330a is formed on the surface of the dielectric layer 320.

In some embodiments of the present application, a method of forming the metal material layer 330a includes a chemical vapor deposition process or a physical vapor deposition process.

In some embodiments of the present application, the material of the metal material layer 330a includes aluminum or tungsten, etc.

Referring to fig. 16, the metal material layer 330a is etched to form the metal grids 330. The metal grids 330 may prevent crosstalk of light rays in adjacent color filter layers, increase the amount of light rays entering a pixel region, and improve image quality.

Referring to fig. 17, a first photoresist layer 341 is formed on the dielectric layer 320 on the second pixel region 302 and the third pixel region 303. Referring to fig. 18, a first ion implantation process is performed on the dielectric layer 320 on the first pixel region 301 to change the intrinsic characteristics thereof.

Referring to fig. 19, the first photoresist layer 341 is removed, and a second photoresist layer 342 is formed on the dielectric layer 320 over the first pixel region 301 and the third pixel region 303. Referring to fig. 20, a second ion implantation process is performed on the dielectric layer 320 on the second pixel region 302 to change the intrinsic characteristics thereof.

Referring to fig. 21, the second photoresist layer 342 is removed, and a third photoresist layer 343 is formed on the dielectric layer 320 on the first pixel region 301 and the second pixel region 302. Referring to fig. 22, a third ion implantation process is performed on the dielectric layer 320 in the third pixel region 303 to change the intrinsic characteristics thereof, and then the third photoresist layer 343 is removed.

The refractive index of the dielectric layers on different pixel regions can be controlled by controlling the ion implantation concentration in each ion implantation process. Specifically, the ion implantation concentration can be calculated as needed.

In other embodiments of the present application, a method of forming the dielectric layer of different material includes: forming a first dielectric layer on the surface of the semiconductor substrate and the surface of the isolation structure, carrying out patterning treatment on the first dielectric layer, removing part of the first dielectric layer on the surface of the substrate and the surface of the isolation structure, and only leaving the first dielectric layer with a preset thickness in a first pixel area; forming a second dielectric layer on the surface of the semiconductor substrate, the surface of the isolation structure and the surface of the first pixel region, carrying out patterning treatment on the second dielectric layer, removing part of the second dielectric layer on the surface of the substrate, the surface of the isolation structure and the surface of the first pixel region, and only leaving the second dielectric layer with a preset thickness in the second pixel region; and forming a third dielectric layer on the surface of the semiconductor substrate, the surface of the isolation structure, the surfaces of the first pixel area and the second pixel area, carrying out patterning treatment on the third dielectric layer, removing partial third dielectric layers on the surface of the substrate, the surface of the isolation structure, the surfaces of the first pixel area and the second pixel area, and only leaving the third dielectric layer with a preset thickness in the third pixel area. Namely, a modification treatment mode is not adopted, and different materials are directly used for forming different dielectric layers.

Referring to fig. 23, a color filter layer 340 is formed on the surface of the dielectric layer 320 between adjacent metal grids 330. The color filter layer 340 corresponds to different positions of the pixel regions, and is used for allowing light of a specific wavelength range to enter the photosensitive element through the light of the specific wavelength range. When the color filter layer 340 corresponds to pixel regions of different colors, the color filter layer 340 may be sequentially formed as needed.

Referring to fig. 24, a microlens 350 is formed on the color filter layer 340. The micro lenses 350 correspond to positions of the color filter layer 340 and are disposed right above the color filter layer 340.

The microlens 350 is used to collect light for each pixel unit, and is made of, for example, a polystyrene resin, an acrylic resin, or a copolymer resin of these resins.

According to the forming method of the image sensor, the dielectric layers with different intrinsic characteristics are designed for the pixel regions with different colors, so that the light rays of the pixel regions with different colors can achieve the optimal optical transmittance, and the imaging quality of the image sensor is improved.

An embodiment of the present application further provides an image sensor, referring to fig. 24, including: the pixel structure comprises a semiconductor substrate, a first pixel region, a second pixel region, a third pixel region and an isolation structure for isolating the first pixel region, the second pixel region and the third pixel region; the dielectric layer is positioned on the surface of the semiconductor substrate and the surface of the isolation structure, wherein the dielectric layer on the first pixel region, the dielectric layer on the second pixel region and the dielectric layer on the third pixel region are made of different materials; the metal grids are positioned on the surface of the dielectric layer, and the positions of the metal grids correspond to the positions of the isolation structures; the color filter layer is arranged between the surface of the medium layer and the adjacent metal grids; and the micro lens is positioned on the color filter layer.

Referring to fig. 24, the semiconductor substrate 300 includes a first pixel region 301, a second pixel region 302, a third pixel region 303, and an isolation structure 310 for isolating the first pixel region 301, the second pixel region 302, and the third pixel region 303.

In some embodiments of the present application, the isolation structure 310 is formed by filling an insulating material (e.g., silicon dioxide or silicon nitride, etc.) in the trench. The isolation structure 310 isolates adjacent pixel regions, so that light rays in the adjacent pixel regions are prevented from crosstalk, and further photon detection efficiency of each pixel region is improved.

With reference to fig. 24, a dielectric layer 320 is formed on the surface of the semiconductor substrate 300 and the surface of the isolation structure 310, wherein the dielectric layer 320 on the first pixel region 301, the dielectric layer 320 on the second pixel region 302, and the dielectric layer 320 on the third pixel region 303 are made of different materials.

In order to maximize the optical transmittance of light passing through the dielectric layer 320, in the image sensor according to the embodiment of the present application, the dielectric layers with different intrinsic characteristics are specially designed for the pixel regions with different colors, so that the light in the pixel regions with different colors can reach the optimal optical transmittance, thereby improving the imaging quality of the image sensor.

With continued reference to fig. 24, a plurality of metal grids 330 are formed on the surface of the dielectric layer 320, and the positions of the metal grids 330 correspond to the positions of the isolation structures 310. The positional correspondence means that a projection of the metal grid 330 in a vertical direction substantially coincides with a projection of the isolation structure 310 in the vertical direction. The metal grids 330 may prevent crosstalk of light rays in adjacent color filter layers, increase the amount of light rays entering a pixel region, and improve image quality.

In some embodiments of the present application, the material of the metal grid 340 includes aluminum or tungsten, etc.

With continued reference to fig. 24, a color filter layer 340 is formed on the surface of the dielectric layer 320 between adjacent metal grids 330. The color filter layer 340 corresponds to different positions of the pixel regions, and is used for allowing light of a specific wavelength range to enter the photosensitive element through the light of the specific wavelength range. When the color filter layer 340 corresponds to pixel regions of different colors, the color filter layer 340 may be sequentially formed as needed.

In some embodiments of the present application, a red color filter layer may be sequentially formed on the first pixel region 301, a green color filter layer may be formed on the second pixel region 302, and a blue color filter layer may be sequentially formed on the third pixel region 303, respectively, according to division of corresponding pixel regions in the semiconductor substrate 300.

In some embodiments of the present application, the color filter layer 340 is formed of a resin to which an organic pigment is added inside. In addition, the color filter layer 340 may be made of other materials, such as a reflective material capable of reflecting light with a specific wavelength.

With continued reference to fig. 24, microlenses 350 are formed on the color filter layer 340. The micro lenses 350 correspond to positions of the color filter layer 340 and are disposed right above the color filter layer 340.

According to the image sensor, the dielectric layers with different refractive indexes are designed for the pixel regions with different colors, so that the light rays of the pixel regions with different colors can reach the optimal optical transmittance, and the imaging quality of the image sensor is improved.

According to the image sensor and the forming method thereof, on one hand, different medium layer thicknesses can be designed for different color pixel areas, so that the light rays of the different color pixel areas can reach the optimal optical transmittance, and the imaging quality of the image sensor is improved; on the other hand, the dielectric layers with different intrinsic characteristics can be designed for the pixel regions with different colors, so that the light rays of the pixel regions with different colors can reach the optimal optical transmittance, and the imaging quality of the image sensor is improved.

In view of the above, it will be apparent to those skilled in the art upon reading the present application that the foregoing application content may be presented by way of example only, and may not be limiting. Those skilled in the art will appreciate that the present application is intended to cover various reasonable variations, adaptations, and modifications of the embodiments described herein, although not explicitly described herein. Such alterations, modifications, and variations are intended to be within the spirit and scope of the exemplary embodiments of this application.

It is to be understood that the term "and/or" as used herein in this embodiment includes any and all combinations of one or more of the associated listed items. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present.

Similarly, it will be understood that when an element such as a layer, region or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, the term "directly" means that there are no intervening elements. It will be further understood that the terms "comprises," "comprising," "includes" or "including," when used in this specification, 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.

It will be further understood that, although the terms first, second, third, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. Thus, a first element in some embodiments may be termed a second element in other embodiments without departing from the teachings of the present application. The same reference numerals or the same reference characters denote the same elements throughout the specification.

Further, the present specification describes example embodiments with reference to idealized example cross-sectional and/or plan and/or perspective views. Accordingly, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an etched region shown as a rectangle will typically have rounded or curved features. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of exemplary embodiments.

Claims

1. A method of forming an image sensor, comprising:

providing a semiconductor substrate, wherein the semiconductor substrate comprises a first pixel region, a second pixel region, a third pixel region and an isolation structure for isolating the first pixel region, the second pixel region and the third pixel region;

forming dielectric layers on the surface of the semiconductor substrate and the surface of the isolation structure, wherein the optical transmittance of the dielectric layer on the first pixel region to red light reaches a maximum value, the optical transmittance of the dielectric layer on the second pixel region to green light reaches a maximum value, and the optical transmittance of the dielectric layer on the third pixel region to blue light reaches a maximum value;

forming a plurality of metal grids on the surface of the dielectric layer, wherein the positions of the metal grids correspond to the positions of the isolation structures;

forming a color filter layer positioned between the adjacent metal grids on the surface of the dielectric layer;

and forming a micro lens on the color filter layer.

2. The method of claim 1, wherein a thickness of the dielectric layer in the first pixel region, a thickness of the dielectric layer in the second pixel region, and a thickness of the dielectric layer in the third pixel region are different.

3. The method as claimed in claim 2, wherein the first pixel region is a red pixel region, the second pixel region is a green pixel region, and the third pixel region is a blue pixel region, wherein a thickness of the dielectric layer of the first pixel region is greater than a thickness of the dielectric layer of the second pixel region, and the thickness of the dielectric layer of the second pixel region is greater than a thickness of the dielectric layer of the third pixel region.

4. The method of forming an image sensor of claim 3, wherein forming the dielectric layer comprises:

forming dielectric layers on the surface of the semiconductor substrate and the surface of the isolation structure;

and etching the dielectric layers of the first pixel area, the second pixel area and the third pixel area to respectively reach the preset thickness.

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

determining the material of the dielectric layer;

according to the light interference principle and the transmission principle in the thin film material, the thickness of a preset medium layer in the pixel area is calculated, namely the optimal thickness is calculated, so that the red light transmittance of the first pixel area reaches the maximum peak value, the green light transmittance of the second pixel area reaches the maximum peak value, and the blue light transmittance of the third pixel area reaches the maximum peak value.

6. The method as claimed in claim 1, wherein the dielectric layer on the first pixel region, the dielectric layer on the second pixel region, and the dielectric layer on the third pixel region are made of different materials, and the transmittance of each dielectric layer is calculated according to parameters of optical refractive index, optical reflectivity, and optical absorption of each dielectric layer.

7. The method of forming an image sensor of claim 6, wherein forming the dielectric layer comprises:

carrying out first modification treatment on the dielectric layer on the first pixel region, wherein the first modification treatment comprises a first ion implantation process;

performing second modification treatment on the dielectric layer on the second pixel region, wherein the second modification treatment comprises a second ion implantation process;

and carrying out third modification treatment on the dielectric layer on the third pixel region, wherein the third modification treatment comprises a third ion implantation process.

8. The method of forming an image sensor of claim 7, further comprising:

and calculating the light transmittance of the dielectric layers in different pixel regions according to the light refractive index, the light reflectance and the light absorption rate of the dielectric layers, and calculating the ion implantation concentration by combining the thickness of the dielectric layers, thereby realizing the process.

9. The method of claim 6, wherein forming the dielectric layer of a different material comprises:

forming a first dielectric layer on the surface of the semiconductor substrate and the surface of the isolation structure, carrying out patterning treatment on the first dielectric layer, removing part of the first dielectric layer on the surface of the substrate and the surface of the isolation structure, and only leaving the first dielectric layer with a preset thickness in a first pixel area;

forming a second dielectric layer on the surface of the semiconductor substrate, the surface of the isolation structure and the surface of the first pixel region, carrying out patterning treatment on the second dielectric layer, removing part of the second dielectric layer on the surface of the substrate, the surface of the isolation structure and the surface of the first pixel region, and only leaving the second dielectric layer with a preset thickness in the second pixel region;

and forming a third dielectric layer on the surface of the semiconductor substrate, the surface of the isolation structure, the surfaces of the first pixel area and the second pixel area, carrying out patterning treatment on the third dielectric layer, removing partial third dielectric layers on the surface of the substrate, the surface of the isolation structure, the surfaces of the first pixel area and the second pixel area, and only leaving the third dielectric layer with a preset thickness in the third pixel area.

10. The method of claim 1, wherein the dielectric layer is a single material or a combination of materials.

11. The method of claim 1, wherein the dielectric layer comprises silicon oxide or silicon nitride.

12. The method of forming an image sensor of claim 1, wherein the method of forming the plurality of metal grids comprises:

forming a metal material layer on the surface of the dielectric layer;

and etching the metal material layer to form the plurality of metal grids.

13. An image sensor, comprising:

the pixel structure comprises a semiconductor substrate, a first pixel region, a second pixel region, a third pixel region and an isolation structure for isolating the first pixel region, the second pixel region and the third pixel region;

the dielectric layer is positioned on the surface of the semiconductor substrate and the surface of the isolation structure, wherein the optical transmittance of the dielectric layer on the first pixel region to red light reaches the maximum value, the optical transmittance of the dielectric layer on the second pixel region to green light reaches the maximum value, and the optical transmittance of the dielectric layer on the third pixel region to blue light reaches the maximum value;

the metal grids are positioned on the surface of the dielectric layer, and the positions of the metal grids correspond to the positions of the isolation structures;

the color filter layer is positioned on the surface of the medium layer and between the adjacent metal grids;

and the micro lens is positioned on the color filter layer.

14. The image sensor of claim 13, wherein the first pixel region is a red pixel region, the second pixel region is a green pixel region, and the third pixel region is a blue pixel region, wherein an optical transmittance of the dielectric layer on the first pixel region to red light reaches a maximum peak and is greater than an optical transmittance to blue light and green light, an optical transmittance of the dielectric layer on the second pixel region to green light reaches a maximum peak and is greater than an optical transmittance to blue light and red light, and an optical transmittance of the dielectric layer on the third pixel region to blue light reaches a maximum peak and is greater than an optical transmittance to red light and green light.

15. The image sensor of claim 13, wherein the dielectric layer is a single layer structure or a multi-layer structure.

16. The image sensor of claim 13, wherein the material of the dielectric layer comprises silicon oxide or silicon nitride.