CN119384057A - Back-illuminated image sensor and method for manufacturing the same - Google Patents
Back-illuminated image sensor and method for manufacturing the same Download PDFInfo
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Abstract
The application discloses a back-illuminated image sensor and a preparation method thereof. The method comprises the steps of providing a substrate, forming a plurality of sacrificial structures with the same space on the substrate, forming side walls on the side walls of the sacrificial structures, removing the sacrificial structures to form transition mask patterns formed by the side walls, removing part of the side walls in the transition mask patterns to obtain first mask patterns, wherein the first mask patterns are provided with a plurality of openings positioned between the side walls, at least one opening is different from the other openings in width, a plurality of grooves are formed in the substrate by taking the first mask patterns as masks, the depths of the grooves corresponding to the openings with different widths are different, removing the first mask patterns, forming isolation structures in the grooves, removing parts of the substrate positioned between the adjacent isolation structures to form a plurality of device accommodating grooves, and forming doped layers in the device accommodating grooves, wherein the doping types of the doped layers are opposite to the doping types of the substrate.
Description
Technical Field
The embodiment of the disclosure relates to the technical field of semiconductors, in particular to a back-illuminated image sensor and a preparation method thereof.
Background
The CMOS backside illuminated image sensor (CMOS Image Sensor BSI) includes a plurality of photodiodes and deep trench isolation structures (DEEP TREND Insolate, DTI) located between the photodiodes. In the advanced process of the CMOS backside illuminated image sensor, the typical deep trench isolation structures between the plurality of photodiodes have the same size, and cannot meet the different isolation requirements between the plurality of photodiodes in the backside illuminated image sensor.
Disclosure of Invention
The embodiment of the disclosure provides a backside illuminated image sensor and a preparation method thereof, which can optimize the size of an isolation structure between photodiodes, and meet different isolation requirements between photodiodes in the backside illuminated image sensor while not affecting the size of the photodiodes.
A method of fabricating a backside illuminated image sensor, comprising:
Providing a substrate;
forming a plurality of sacrificial structures with the same spacing on the substrate;
forming a side wall on the side wall of the sacrificial structure, removing the sacrificial structure, and forming a transition mask pattern formed by the side wall;
Removing part of the side walls in the transition mask pattern to obtain a first mask pattern, wherein the first mask pattern is provided with a plurality of openings positioned between the side walls, and at least one opening has a width different from the widths of other openings;
forming a plurality of grooves in the substrate by taking the first mask pattern as a mask, wherein the grooves corresponding to the openings with different widths have different depths;
removing the first mask pattern;
forming an isolation structure in the groove;
Removing the part of the substrate between the adjacent isolation structures to form a plurality of device accommodating grooves;
And forming a doping layer in the device accommodating groove, wherein the doping type of the doping layer is opposite to that of the substrate.
In one embodiment, the depth of at least two of the device receiving grooves is different, and the depth of any one of the device receiving grooves is less than or equal to the minimum depth of its adjacent isolation structure.
In one embodiment, the depth of each device receiving groove is equal, and the depth of the device receiving groove is less than or equal to the minimum depth of the isolation structure.
In one embodiment, the method for manufacturing the back-illuminated image sensor further includes:
and forming a shading layer on the surface of the isolation structure.
In one embodiment, the opening of the light shielding layer exposes each doped layer, and the method for manufacturing the back-illuminated image sensor further includes:
And forming color filter layers on the surfaces of the doped layers respectively, wherein the color filter layers are filled in the corresponding openings of the shading layers.
In one embodiment, the sacrificial structure and the substrate are made of the same material, an etching protection layer is further formed between the substrate and the sacrificial structure, and after the first mask pattern is removed, the preparation method further comprises the steps of:
and removing the etching protection layer.
In one embodiment, the step of forming a plurality of trenches in the substrate using the first mask pattern as a mask includes:
Etching the substrate at the opening position by taking the first mask pattern as a mask and adopting an isotropic etching process;
Etching the substrate at the opening position by taking the first mask pattern as a mask and adopting a non-isotropic etching process;
wherein the depth of the trench is inversely related to the width of the corresponding opening.
In one embodiment, the process gas of the anisotropic etching process comprises methane and fluoromethane, the bias power is 0, and the process gas of the anisotropic etching process comprises methane and fluoromethane, and the bias power is greater than 0.
In one embodiment, the forming the isolation structure in the trench includes:
Forming an isolation material layer in the groove;
Carrying out chemical mechanical planarization treatment on the isolation material layer to obtain an isolation structure positioned in the groove;
wherein the top surface of the isolation structure is flush with the surface of the substrate.
A back-illuminated image sensor is manufactured by the manufacturing method of the back-illuminated image sensor.
The unexpected technical effects that the application can produce are:
According to the back-illuminated image sensor and the preparation method thereof, the sacrificial structures with the same spacing are formed on the substrate, so that the uniformity of the sizes of the side walls positioned on the side walls of the sacrificial structures is improved, the influence of the spacing between the sacrificial structures on the sizes of the doped layers in the back-illuminated image sensor is eliminated, and the performance of the back-illuminated image sensor is improved. By removing part of the side walls, the widths of the openings between the side walls are different, so that grooves with different depths corresponding to the openings are formed, the sizes of isolation structures in the grooves are different, and different isolation requirements between the subsequently formed photosensitive devices between adjacent isolation structures are met. In addition, the isolation structures are formed firstly and then the doped layers positioned between the isolation structures are formed, the isolation structures serve as self-aligned structures for forming the doped layers, and in the application, the isolation structures are formed firstly and then the doped layers positioned between the isolation structures are formed, so that the shape and position accuracy of the doped layers are improved.
Drawings
In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the related art, the drawings that are required to be used in the embodiments or the related technical descriptions will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present disclosure, and other drawings may be obtained according to the drawings without inventive effort to those of ordinary skill in the art.
FIG. 1 is a flow chart of a method for fabricating a backside illuminated image sensor according to some embodiments;
FIG. 2 is a schematic cross-sectional view of a backside illuminated image sensor after formation of a photoresist pattern in some embodiments;
FIG. 3 is a schematic cross-sectional view of a backside illuminated image sensor after forming a sacrificial layer in some embodiments;
FIG. 4 is a schematic cross-sectional view of a backside illuminated image sensor after forming a sidewall material layer in some embodiments;
FIG. 5 is a schematic cross-sectional view of a backside illuminated image sensor after forming a sidewall in some embodiments;
FIG. 6 is a schematic cross-sectional view of a backside illuminated image sensor after forming a second mask pattern in some embodiments;
FIG. 7 is a schematic cross-sectional view of a backside illuminated image sensor after forming a first mask pattern in some embodiments;
FIG. 8 is a schematic cross-sectional view of a backside illuminated image sensor after forming trenches in some embodiments;
FIG. 9 is a schematic cross-sectional view of a backside illuminated image sensor after forming isolation structures in some embodiments;
FIG. 10 is a schematic cross-sectional view of a backside illuminated image sensor after forming a device receiving trench in some embodiments;
FIG. 11 is a schematic cross-sectional view of a backside illuminated image sensor after a light shielding layer is formed in some embodiments.
Reference numerals illustrate:
The substrate 102, the hard mask layer 104, the metal interconnection structure 106, the etching protection layer 108, the side wall 110, the second mask pattern 112, the first mask pattern 114, the isolation structure 116, the doped layer 118, the light shielding layer 120, the color filter layer 122, the photoresist pattern 202, the sacrificial structure 204, the side wall material layer 206, the opening 208, the trench 210, and the device accommodating groove 212.
Detailed Description
In order to facilitate an understanding of the disclosed embodiments, the disclosed embodiments are described more fully below with reference to the accompanying drawings. Preferred embodiments of the presently disclosed embodiments are shown in the drawings. The disclosed embodiments may, however, be embodied in many different forms and are not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of this disclosure belong. The terminology used in the description of the embodiments of the disclosure herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the embodiments of the disclosure. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
In the description of the embodiments of the present disclosure, it should be understood that the terms "upper," "lower," "vertical," "horizontal," "inner," "outer," and the like indicate orientations or positional relationships based on the methods or positional relationships shown in the drawings, merely to facilitate describing the embodiments of the present disclosure and to simplify the description, and do not indicate or imply that the devices or elements being referred to must have a particular orientation, be configured and operated in a particular orientation, and thus should not be construed as limiting the embodiments of the present disclosure.
It will be understood that the terms "first," "second," and the like, as used in this disclosure, may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another element. For example, a first reticle may be referred to as a second reticle, and similarly, a second reticle may be referred to as a first reticle, without departing from the scope of the present disclosure. Both the first reticle and the second reticle are reticles, but they are not the same reticle.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present disclosure, the meaning of "a plurality" is at least two, such as two, three, etc., unless explicitly specified otherwise. In the description of the present disclosure, the meaning of "several" means at least one, such as one, two, etc., unless specifically defined otherwise.
Fig. 1 is a flow chart of a method for manufacturing a backside-illuminated image sensor according to some embodiments, as shown in fig. 1, in this embodiment, a method for manufacturing a backside-illuminated image sensor is provided, including:
S102, providing a substrate.
Specifically, a substrate is provided, the substrate including a first surface and a second surface disposed opposite to each other, and a sacrificial structure formed later is disposed on the first surface of the substrate. The constituent materials of the substrate include single crystal silicon, silicon-on-insulator (SOI), silicon-on-insulator (SSOI), silicon-germanium-on-insulator (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), germanium-on-insulator (GeOI), gallium arsenide (GaAs), gallium nitride (GaN), silicon carbide (SiC), or any combination thereof. As an example, in the present embodiment, a single crystal silicon is selected as a constituent material of the substrate.
S104, forming a plurality of sacrificial structures with the same spacing on the substrate.
Specifically, a plurality of sacrificial structures are formed on a substrate at intervals, and the spacing between two adjacent sacrificial structures is the same in a plane parallel to the substrate.
And S106, forming a side wall on the side wall of the sacrificial structure, removing the sacrificial structure, and forming a transition mask pattern formed by the side wall.
Specifically, a side wall is formed on the side wall of the sacrificial structure, the side wall is adjacent to the sacrificial structure, the top surface of the side wall away from the substrate is flush with the top surface of the sacrificial structure away from the substrate, the bottom surface of the side wall close to the substrate is flush with the bottom surface of the sacrificial structure close to the substrate, the distance between the two adjacent sacrificial structures is the same, the side walls of the sacrificial structures are the same in size, and the uniformity of the side walls is improved. And then, removing the sacrificial structure by adopting an etching process (such as a dry etching process) to form a transition mask pattern formed by the side walls.
S108, removing part of the side wall in the transition mask pattern to obtain a first mask pattern.
And removing part of the side walls in the positions of the transition mask patterns by adopting photoetching and etching processes to obtain a first mask pattern formed by the residual side walls, wherein the first mask pattern is provided with a plurality of openings positioned between the adjacent side walls, at least one opening has a width different from the width of other openings, the width is the distance between the adjacent side walls in the direction parallel to the substrate, and the width of the opening positioned between the adjacent side walls in the first mask pattern is adjusted by removing part of the side walls in the positions, so that the purpose of adjusting the width of a groove formed subsequently in a plane parallel to the substrate and further adjusting the depth of the groove in the direction perpendicular to the substrate is achieved. And simultaneously, a doping layer is formed at the position covered by the first mask pattern, a photosensitive device positioned between the doping layer and the substrate at the bottom is formed, and the shape and the position of the photosensitive device formed at the later stage in a plane parallel to the substrate and the shape and the position of the isolation structure in the plane parallel to the substrate are defined through the first mask pattern.
S110, forming a plurality of grooves in the substrate by taking the first mask pattern as a mask.
And etching to remove the substrate with partial thickness exposed by the opening by taking the first mask pattern as a mask, so as to form a plurality of grooves in the substrate, wherein the grooves respectively correspond to the openings, and the depths of the grooves corresponding to the openings with different widths in a plane parallel to the substrate are different in the direction perpendicular to the substrate.
S112, removing the first mask pattern.
And S114, forming an isolation structure in the groove.
Specifically, an isolation structure is formed in the groove, the groove is filled with the isolation structure, the top surface of the isolation structure is flush with the first surface of the substrate, the corresponding isolation structures of the grooves with different depths are different in size, and therefore the requirement of different isolation between different light-sensitive devices between adjacent isolation structures formed later is met.
And S116, removing the part of the substrate positioned between the adjacent isolation structures to form a plurality of device accommodating grooves.
Specifically, the substrate with partial thickness between the adjacent isolation structures is removed by etching, and device accommodating grooves are formed between the adjacent isolation structures, the adjacent isolation structures are exposed from the side walls of the device accommodating grooves in the direction perpendicular to the substrate, and the adjacent device accommodating grooves are separated by the isolation structures.
S118, forming a doping layer in the device accommodating groove.
Specifically, a doped layer is formed in the device accommodating groove, the doped layer has a first conductivity type, and the substrate has a second conductivity type, namely, the doping type of the doped layer is opposite to the doping type of the substrate. The doping type includes N-type doping and P-type doping, and when the first conductivity type is P-type, the second conductivity type is N-type, and when the first conductivity type is N-type, the second conductivity type is P-type. In this embodiment, the first conductivity type is N-type and the second conductivity type is P-type. Further, a top surface of the doped layer adjacent to the first surface of the substrate is flush with the first surface of the substrate.
According to the back-illuminated image sensor and the preparation method thereof, the sacrificial structures with the same spacing are formed on the substrate, so that the uniformity of the sizes of the side walls of the sacrificial structures is improved, the influence of the spacing between the sacrificial structures on the sizes of the doped layers in the back-illuminated image sensor is eliminated, and the performance of the back-illuminated image sensor is improved. By removing part of the side walls, the widths of the openings between the side walls are different, so that grooves with different depths corresponding to the openings are formed, the sizes of isolation structures in the grooves are different, and different isolation requirements between the subsequently formed photosensitive devices between adjacent isolation structures are met. In addition, the isolation structures are formed firstly and then the doped layers positioned between the isolation structures are formed, the isolation structures serve as self-aligned structures for forming the doped layers, and in the application, the isolation structures are formed firstly and then the doped layers positioned between the isolation structures are formed, so that the shape and position accuracy of the doped layers are improved.
Fig. 2 is a schematic cross-sectional view of the backside illuminated image sensor after forming the photoresist pattern in some embodiments, and fig. 3 is a schematic cross-sectional view of the backside illuminated image sensor after forming the sacrificial layer in some embodiments, as shown in fig. 2 and 3, the step of forming a plurality of sacrificial structures 204 with the same pitch on the substrate includes steps S202-S204.
S202, forming a hard mask layer on the substrate.
And S204, performing patterning treatment on the hard mask layer by adopting the first mask plate to form the sacrificial structure 204.
Specifically, in the first step of steps S202 to S204, the hard mask layer 104 and the photoresist layer are sequentially formed on the first surface of the substrate 102 from the first surface of the substrate 102 to a direction away from the first surface of the substrate 102. The second step of patterning the hard mask layer 104 by using a first mask to form a plurality of sacrificial structures 204 with the same spacing, specifically, the first step is to use the first mask as a mask to perform patterning treatment on the photoresist layer to form a photoresist pattern 202 on the surface of the hard mask layer 104 far away from the substrate 102, and the second step is to use the photoresist pattern 202 mask to etch and remove the hard mask layer 104 exposed by the photoresist pattern 202 to form a plurality of sacrificial structures 204 which are arranged at intervals and are formed by the residual hard mask layer 104 (the hard mask layer 104 covered by the photoresist pattern 202), wherein the spacing L1 between two adjacent sacrificial structures 204 is the same.
It will be appreciated that the photoresist pattern 202 is removed during etching of the hard mask layer 104 where the photoresist pattern 202 is exposed, or that the backside image sensor manufacturing method includes the step of removing the photoresist pattern 202 after the sacrificial structure 204 is formed.
Illustratively, the material of the hard mask layer 104 includes silicon, amorphous silicon, or amorphous carbon, and the hard mask layer 104 may be formed by an epitaxial process, spin-on or spray-on process, or the like. In this embodiment, the material of the hard mask layer 104 is silicon. At this time, the hard mask layer 104 is the same material as the substrate 102.
As shown in fig. 2, a metal interconnect structure 106 is formed on the second surface of the substrate 102, and the metal interconnect structure 106 is used to implement interconnect conduction for devices in the substrate 102. Illustratively, the first surface is the back side of the substrate 102 and the second surface is the back side of the substrate 102.
As shown in fig. 2, the first surface of the substrate 102 is formed with an etching protection layer 108 covering the first surface of the substrate 102, and the hard mask layer 104 is located on a surface of the etching protection layer 108 away from the substrate 102. Illustratively, the material of the etching protection layer 108 includes silicon oxide, and the etching protection layer 108 is formed on the first surface of the substrate 102 by a thermal oxidation process or a chemical vapor deposition process.
Fig. 4 is a schematic cross-sectional view of the backside illuminated image sensor after forming the sidewall material layer in some embodiments, and fig. 5 is a schematic cross-sectional view of the backside illuminated image sensor after forming the sidewall in some embodiments, as shown in fig. 4 and 5, in which in one embodiment, the step of forming the sidewall 110 on the sidewall of the sacrificial structure 204 includes steps S302-S304.
And S302, forming a side wall material layer 206 on the top surface of the sacrificial structure 204, wherein the side wall material layer 206 extends onto the substrate 102 along the side wall of the sacrificial structure 204.
S304, removing the side wall material layer 206 on the top surface of the sacrificial structure 204 and a part of the side wall material layer 206 on the substrate 102, and reserving the side wall material layer 206 on the side wall of the sacrificial structure 204 as the side wall 110.
In step S302-S304, firstly, a chemical vapor deposition process or an atomic layer deposition process is adopted to form a sidewall material layer 206 on the top surface of the sacrificial structure 204, where the sidewall material layer covers the sidewall of the sacrificial structure 204 and extends along the sidewall of the sacrificial structure 204 to cover the substrate 102, and the spacing L1 between two adjacent sacrificial structures 204 is the same, so that the dimension L2 of the sidewall material layer 206 on the sidewall of the sacrificial structure 204 in the direction parallel to the substrate 102 (the direction in the plane of the first direction X and the second direction Z) is the same, thereby improving the uniformity of the subsequently formed sidewall 110. Next, the top surface of the sacrificial structure 204 and a portion of the sidewall material layer 206 on the substrate 102 are etched and removed, and the sidewall material layer 206 on the sidewall of the sacrificial structure 204 is reserved as the sidewall 110, where the etching protection layer 108 may be used as an etching stop layer for etching a portion of the sidewall material layer 206 on the substrate 102.
Illustratively, the material of the sidewall 110 includes one or more of silicon oxide (e.g., silicon dioxide), silicon nitride (e.g., silicon oxynitride), and nitride (e.g., silicon nitride). In this embodiment, the material of the sidewall 110 is silicon nitride.
As shown in fig. 6, the method of fabricating a backside illuminated image sensor further includes a step of removing the sacrificial structure 204.
Fig. 6 is a schematic cross-sectional view of the backside illuminated image sensor after forming the second mask pattern in some embodiments, and fig. 7 is a schematic cross-sectional view of the backside illuminated image sensor after forming the first mask pattern in some embodiments, as shown in fig. 6 and fig. 7, in which in one embodiment, the step of removing a portion of the sidewall 110 in the transition mask pattern to obtain the first mask pattern includes steps S402-S404.
S402, forming a second mask pattern 112 on the substrate 102, wherein the second mask pattern 112 covers the side wall 110 in the first mask pattern.
And S404, etching to remove the exposed side wall 110 by taking the second mask pattern as a 112 mask, so as to form the first mask pattern.
In step S402-S404, first, a second mask material layer is formed on the substrate 102, and a second mask pattern 112 formed by the remaining second mask material layer is formed by performing a patterning process on the second mask material layer by using a second mask, where the second mask pattern 112 covers the sidewall 110 to be remained and exposes the sidewall 110 to be removed, and exemplary materials of the second mask material layer include photoresist, nitride (silicon nitride), amorphous silicon or amorphous carbon. Next, the second mask pattern 112 is used as a mask, and the exposed sidewall 110 of the second mask pattern 112 is etched to form a first mask pattern 114 formed by the remaining sidewall 110, where the etching protection layer 108 may be used as an etching stop layer for removing the exposed sidewall 110. The first mask pattern 114 has a plurality of openings 208 between adjacent side walls 110, where at least one opening 208 has a width W1 different from the width W2 of the other openings 208, and the width is a distance between adjacent side walls 110 in a direction parallel to the substrate 102 (in any direction in a plane of the first direction X and the second direction Z), and the width of the opening 208 between the adjacent side walls 110 in the first mask pattern 114 is adjusted by removing a portion of the side walls 110.
Fig. 8 is a schematic cross-sectional view of the backside illuminated image sensor after forming the trenches in some embodiments, as shown in fig. 8, in one embodiment, the step of forming the plurality of trenches 210 in the substrate 102 using the first mask pattern 114 as a mask includes S502-S504.
S502, etching the substrate 102 at the position of the opening 208 by using the first mask pattern 114 as a mask and adopting an isotropic etching process.
S504, etching the substrate 102 at the position of the opening 208 by using the first mask pattern 114 as a mask and adopting a non-isotropic etching process.
In the steps S502 to S504, the first mask pattern 114 is used as a mask, an isotropic etching process and a non-isotropic etching process are used to etch the substrate 102 at the position of the opening 208, so as to form a trench 210 located in the substrate 102, where the depth D of the trench 210 is inversely related to the width W of the opening 208, that is, the depth of the trench 210 corresponding to the opening 208 with a large width is small, the depth of the trench 210 corresponding to the opening 208 with a small width is large, and the direction of the depth D is perpendicular to the third direction Y of the substrate 102. It will be appreciated that when the etching protection layer 108 is provided on the substrate 102, the substrate 102 is etched after the etching protection layer 108 exposed by the opening 208 is etched.
Illustratively, when the ratio of the depth of the trench 210 to the width of the opening 208 is greater than or equal to 1:5 and less than or equal to 1:1, the isotropic etching process is performed after the anisotropic etching process is performed during the formation of the trench 210, when the ratio of the depth of the trench 210 to the width of the opening 208 is greater than or equal to 1:10 and less than 1:5, the isotropic etching process is performed after the anisotropic etching process is performed during the formation of the trench 210, and when the ratio of the depth of the trench 210 to the width of the opening 208 is less than 1:10, the order of the isotropic etching process and the anisotropic etching process is not limited.
In one embodiment, the process gas of the anisotropic etching process comprises methane and fluoromethane, the bias power is 0, and the process gas of the anisotropic etching process comprises methane and fluoromethane, and the bias power is greater than 0.
Illustratively, the flow rate of methane gas in the isotropic etching process is greater than or equal to 100sccm and less than or equal to 150sccm, the flow rate of fluoromethane gas is greater than or equal to 60sccm and less than or equal to 100sccm, and the process time of the isotropic etching process is greater than or equal to 15s and less than or equal to 30s. The flow rate of methane gas in the anisotropic etching process is greater than or equal to 100sccm and less than or equal to 150sccm, the flow rate of fluoromethane gas is greater than or equal to 60sccm and less than or equal to 100sccm, the process time of the anisotropic etching process is greater than or equal to 15s and less than or equal to 30s, and the bias power in the anisotropic etching process is 100W.
In one embodiment, after the removing the first mask pattern 110 and before the forming the isolation structure in the trench 210, the method for manufacturing the backside illuminated image sensor further includes removing the etching protection layer 108.
Fig. 9 is a schematic cross-sectional view of the backside illuminated image sensor after forming the isolation structure in some embodiments, as shown in fig. 9, wherein in one embodiment, the forming the isolation structure 116 in the trench 210 includes steps S602-S604.
S602, an isolation material layer is formed in the trench 210.
And S604, performing chemical mechanical planarization treatment on the isolation material layer to obtain the isolation structure 116 in the groove 210.
In step S602-S604, an isolation material layer is formed in the trench 210 by a chemical vapor deposition process or an atomic layer deposition process, and fills the trench 210 and extends to the surface of the substrate 102 along the sidewall of the trench 210. Then, a chemical mechanical planarization process is adopted to planarize the isolation material layer, the isolation material layer higher than the surface of the substrate 102 is removed, the isolation structure 116 located in the trench 210 is formed, the top surface of the isolation structure 116 is flush with the surface (first surface) of the substrate 102, the corresponding isolation structures 116 of the trenches 210 with different depths D have different sizes, so that the isolation structures 116 between the subsequently formed photosensitive devices are different, the requirement of the photosensitive devices on isolation is met, and meanwhile, the isolation structures 116 define the position and shape of the photosensitive devices and play an alignment role in the process of forming the photosensitive devices.
Illustratively, the constituent material of the isolation structure 116 includes one or more of silicon oxide (e.g., silicon dioxide), silicon nitride (e.g., silicon oxynitride), and nitride (e.g., silicon nitride), and in this embodiment, the constituent material of the isolation structure 116 is silicon dioxide.
Fig. 10 is a schematic cross-sectional view of a backside illuminated image sensor after forming device accommodating grooves in some embodiments, as shown in fig. 10, etching away portions of the substrate 102 between adjacent isolation structures 116 to form a plurality of device accommodating grooves 212, exposing the adjacent isolation structures 116 on the sidewalls of the device accommodating grooves 212, and illustratively, etching away portions of the substrate 102 between adjacent isolation structures 116 by using a dry etching process to form device accommodating grooves 212, forming photosensitive devices between the substrate 102 between doped layers formed in subsequent device accommodating grooves 212, and isolating structures 116 between the device accommodating grooves 212 isolating photoelectrons generated by the photosensitive devices from flowing to adjacent photosensitive devices.
In one embodiment, the depth D of at least two of the device accommodating grooves 212 is different, and the depth D of any one of the device accommodating grooves 212 is less than or equal to the minimum depth of the adjacent isolation structures 116, which is set such that the photosensitive devices formed between the doped layer formed in the device accommodating groove 212 and the substrate 102 at the bottom of the device accommodating groove 212 are different in depth.
In one embodiment, the depth D of each device accommodating groove 212 is equal, and the depth D of the device accommodating groove 212 is smaller than or equal to the minimum depth of the isolation structure 116, so that the process of forming the device accommodating groove 212 is simple, and the isolation effect of the isolation structure 116 on the photo-electrons is improved.
Fig. 11 is a schematic cross-sectional view of the backside illuminated image sensor after forming the light shielding layer in some embodiments, as shown in fig. 11, a doped layer 118 is formed in the device accommodating groove 212, and the doping type of the doped layer 118 is opposite to that of the substrate 102, wherein the doped layer 118 fills the device accommodating groove 212. Illustratively, the doped layer 118 is formed in the device accommodating recess 212 using an in-situ doping process. In other embodiments, the doped layer 118 may be formed by deposition and ion implantation.
In one embodiment, as shown in fig. 11, the method for manufacturing the backside illuminated image sensor further includes forming a light shielding layer 120 on the surface of the isolation structure 116. Specifically, a chemical vapor deposition process or an atomic layer deposition process is adopted to form a light shielding material layer covering the doped layer 118 and the isolation structure 116, and then the light shielding material layer on the surface of the doped layer 118 is etched and removed to form a light shielding layer 120 on the surface of the isolation structure 116, wherein the openings of the light shielding layer 120 expose the doped layers 118. Illustratively, the constituent material of the light shielding material layer includes metallic aluminum.
In some embodiments, the light shielding material layer is patterned by using a second mask plate to form the light shielding layer 120 on the surface of the isolation structure 116, that is, the same mask plate is used to form the first mask pattern and the light shielding layer 120, so that the number of mask plates is reduced, and the manufacturing cost of the back-illuminated image sensor is reduced.
In one embodiment, as shown in fig. 11, the method further includes forming color filter layers 122 on the surfaces of the doped layers 118, respectively, where the color filter layers 122 are filled in the openings of the light shielding layer 120. The color filter layer 122 is used for filtering light to match the imaging color of the photosensitive device formed by the corresponding doped layer 118 and the substrate 102, and the color filter layer 122 on the surface of any doped layer 118 can be one of a red filter layer, a green filter layer or a blue filter layer to realize color imaging. Illustratively, the top surface of the color filter layer 122 away from the substrate 102 is flush with the top surface of the light shielding layer 120 away from the substrate 102. It will be appreciated that the light shielding layer 120 between the color filter layers 122 and the isolation structure 116 at the bottom of the light shielding layer 120 also have the function of filtering and blocking the transmission of light.
The disclosure also provides a back-illuminated image sensor, which is manufactured by adopting the preparation method of the back-illuminated image sensor.
It should be understood that, although the steps in the flowchart of fig. 1 are shown in sequence as indicated by the arrows, the steps are not necessarily performed in sequence as indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in fig. 1 may include multiple sub-steps or stages that are not necessarily performed at the same time, but may be performed at different times, nor do the order in which the sub-steps or stages are performed necessarily performed in sequence, but may be performed alternately or alternately with at least a portion of other steps or sub-steps of other steps.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples merely represent a few implementations of the disclosed examples, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made to the disclosed embodiments without departing from the spirit of the disclosed embodiments.
Claims (10)
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