CN110379828B - Method for forming image sensor - Google Patents

Method for forming image sensor Download PDF

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CN110379828B
CN110379828B CN201910721462.5A CN201910721462A CN110379828B CN 110379828 B CN110379828 B CN 110379828B CN 201910721462 A CN201910721462 A CN 201910721462A CN 110379828 B CN110379828 B CN 110379828B
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material layer
forming
layer
isolation
groove
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CN110379828A (en
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阿久津良宏
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Huaian Xide Industrial Design Co ltd
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Huaian Imaging Device Manufacturer Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14625—Optical elements or arrangements associated with the device
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/1463—Pixel isolation structures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
    • H01L27/14685—Process for coatings or optical elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
    • H01L27/14687—Wafer level processing

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  • Condensed Matter Physics & Semiconductors (AREA)
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Abstract

A method of forming an image sensor, comprising: providing a substrate, wherein the substrate comprises a first surface and a second surface which are opposite, and the substrate comprises a plurality of photosensitive areas and an isolation area positioned between the adjacent photosensitive areas; forming a groove in the isolation region, wherein an isolation structure is arranged in the groove, and the top surface of the isolation structure is lower than the surface of the second surface of the substrate; forming a grid material layer on the surface of the isolation structure and the surface of the second surface of the substrate, wherein a first groove is formed in the grid material layer on the surface of the isolation region and the surface of the isolation structure; forming a mask structure in the first groove; and etching the grid material layer by taking the mask structure as a mask to form a grid structure on the surface of the second surface of the isolation region. The performance of the image sensor is improved.

Description

Method for forming image sensor
Technical Field
The invention relates to the field of semiconductor manufacturing, in particular to a method for forming an image sensor.
Background
An image sensor is a semiconductor device that converts an optical signal into an electrical signal. Image sensors are classified into Complementary Metal Oxide Semiconductor (CMOS) image sensors and Charge-coupled Device (CCD) image sensors.
The CMOS image sensor has the advantages of simple process, easiness in integration of other devices, small size, light weight, low power consumption, low cost and the like. Therefore, with the development of image sensing technology, CMOS image sensors are increasingly used in various electronic products instead of CCD image sensors. At present, CMOS image sensors have been widely used in still digital cameras, digital video cameras, medical imaging devices, vehicle imaging devices, and the like.
However, the performance of the existing CMOS image sensor still needs to be improved.
Disclosure of Invention
The invention provides a method for forming an image sensor to improve the performance of the image sensor.
In order to solve the above technical problem, an embodiment of the present invention provides a method for forming an image sensor, including: providing a substrate, wherein the substrate comprises a first surface and a second surface which are opposite, and the substrate comprises a plurality of photosensitive areas and an isolation area positioned between the adjacent photosensitive areas; forming a groove in the isolation region, wherein an isolation structure is arranged in the groove, and the top surface of the isolation structure is lower than the surface of the second surface of the substrate; forming a grid material layer on the surface of the isolation structure and the surface of the second surface of the substrate, wherein a first groove is formed in the grid material layer on the surface of the isolation region and the surface of the isolation structure; forming a mask structure in the first groove; and etching the grid material layer by taking the mask structure as a mask to form a grid structure on the surface of the second surface of the isolation region.
Optionally, the first groove has a first projection on the surface of the substrate, and the isolation structure has a second projection on the surface of the substrate, where the second projection is partially or completely coincident with the first projection.
Optionally, the mask structure includes: a hard mask layer; the hard mask layer is made of silicon oxide or silicon nitride.
Optionally, the mask structure further includes: and the photoresist layer is positioned on the hard mask layer.
Optionally, the forming method of the mask structure includes: forming a hard mask material layer on the surface of the grid material layer, wherein the hard mask material layer covers the first groove; and flattening the hard mask material layer until the surface of the grid material layer is exposed, and forming a mask structure in the first groove.
Optionally, the process for planarizing the hard mask material layer includes a chemical mechanical polishing process or an anisotropic dry etching process.
Optionally, the forming method of the mask structure includes: forming a hard mask material layer on the surface of the grid material layer, wherein the hard mask material layer is internally provided with a second groove, the second groove is provided with a third projection on the surface of the substrate, the third projection is partially or completely coincided with the second projection, and the third projection is partially or completely coincided with the first projection; forming a photoresist material layer on the surface of the hard mask material layer, wherein the photoresist material layer covers the second groove; flattening the photoresist material layer until the surface of the hard mask material layer is exposed, and forming a photoresist layer in the second groove; and etching the hard mask material layer by taking the photoresist layer as a mask to form the hard mask layer.
Optionally, the process for planarizing the photoresist material layer includes an anisotropic dry etching process.
Optionally, the method for forming the isolation structure includes: forming a patterned layer on the surface of the second surface of the substrate, wherein the patterned layer exposes the surface of the isolation region; etching the substrate by taking the patterning layer as a mask to form a groove in the isolation region; forming an isolation material layer in the groove and on the surface of the second surface of the substrate; and etching back the isolation material layer until the top surface of the isolation material layer is lower than the second surface of the substrate, and forming the isolation structure in the groove.
Optionally, the material of the isolation material layer includes silicon oxide.
Optionally, the process of forming the isolation material layer includes a chemical vapor deposition process, a thermal oxidation process, or an atomic layer deposition process.
Optionally, the process of etching the grid material layer includes an anisotropic dry etching process.
Optionally, the material of the grid material layer comprises a metal; the metal comprises one or more of copper, tungsten, nickel, chromium, titanium, tantalum and aluminum in combination.
Optionally, the method further includes: forming a light filtering structure on the surface of the second surface of the photosensitive area; forming a lens on the filtering structure and the grid structure.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
in the method for forming the image sensor, the top surface of the isolation structure is lower than the second surface of the substrate, so that the grid material layer formed on the surface of the isolation structure and the second surface of the substrate is provided with a first groove, the first groove is positioned in the partial grid material layer on the surface of the isolation region and the surface of the isolation structure, a mask structure is formed in the first groove, the grid material layer is etched by the mask structure to form a grid structure, and the grid structure can be accurately positioned on the second surface of the isolation region, so that the problem that the position of the grid structure on the surface of the isolation region is deviated is avoided. The method enables the grid structure to be self-aligned to the surface of the isolation region, and improves the performance of the image sensor.
Drawings
FIGS. 1 and 2 are schematic cross-sectional structural views of an image sensor forming process according to an embodiment;
FIGS. 3 to 11 are schematic cross-sectional views illustrating an image sensor forming process according to an embodiment of the present invention;
fig. 12 and 13 are schematic cross-sectional structural views of an image sensor forming process in another embodiment of the present invention.
Detailed Description
As described in the background, the performance of the existing image sensor is to be improved, and the analysis is now performed in conjunction with the specific embodiment.
FIGS. 1 and 2 are schematic cross-sectional structural views of an image sensor forming process according to an embodiment;
referring to fig. 1, a substrate 100 is provided, the substrate 100 includes a first side and a second side opposite to each other, the substrate 100 includes a photosensitive area a and an isolation area B; a deep trench isolation structure 102 located within the isolation region B; an anti-reflection layer 101 located on the outer wall of the deep trench isolation structure 102 and the second surface of the substrate 100; a grid material layer 103 located on the surface of the deep trench isolation structure 102 and the surface of the anti-reflection layer 101; a patterned mask layer 104 on the surface of the grid material layer 103, wherein the patterned mask layer 104 exposes a portion of the surface of the grid material layer 103.
Referring to fig. 2, the grid material layer 103 is etched using the patterned mask layer 104 as a mask, and a grid structure 105 is formed on the surface of the deep trench isolation structure 102.
In the image sensor, the grid structure 105 is used for isolating optical crosstalk of an adjacent filter layer formed on the surface of the photosensitive area; the deep trench isolation structure 102 is used for isolating optical crosstalk of the adjacent photosensitive area a, which is incident to the photosensitive area a through the filter layer. The grid structure 105 is located on the second side surface of the isolation region B. When light enters the photosensitive area A through the filter layer, more light enters the photosensitive area A, more photoelectrons are converted by the photosensitive structure in the photosensitive area A, and the efficiency of the image sensor is high.
However, as technology nodes decrease, the image sensor becomes smaller in size. In the process of forming the grid structure 105 by using a photolithography process, the accuracy of the existing photolithography technique is limited, so that when a patterned mask layer 104 is formed, the position of the patterned mask layer 104 deviates from a set position, thereby causing the grid structure 105 formed by etching the grid material layer 103 by using the patterned mask layer 104 as a mask, and the position of the grid structure 105 on the second surface of the isolation region B is also shifted, so that part of the grid structure 105 is located on the surface of the photosensitive region a (such as the region Y); then, after the part of the light ray X entering the photosensitive area a through the filter layer is blocked by the deep trench isolation structure 102 and reflected, the part of the light ray X cannot enter the photosensitive area a, so that the amount of the light ray entering the photosensitive area a is reduced, and further the amount of photoelectrons converted by the photosensitive structure is reduced, so that the utilization rate of the light ray is reduced, and the performance of the image sensor is affected.
In order to solve the above problems, an embodiment of the present invention provides a method for forming an image sensor, in which a mask structure is formed in a first groove in a partial grid material layer located on a surface of an isolation region and a surface of an isolation structure, and the grid material layer is etched by using the mask structure to form a grid structure, where the grid structure can be located on a second surface of the isolation region accurately. The method enables the grid structure to be self-aligned to the surface of the isolation region, and improves the performance of the image sensor.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Fig. 3 to 11 are schematic cross-sectional structural diagrams illustrating an image sensor forming process according to an embodiment of the present invention.
Referring to fig. 3, a substrate 200 is provided.
The substrate 200 includes a first surface and a second surface opposite to each other, and the substrate 200 includes a plurality of photosensitive regions I and isolation regions II located between adjacent photosensitive regions I.
The substrate 200 has a photosensitive structure 201 in the photosensitive area I, and the photosensitive structure 201 is exposed on the second side of the substrate 200.
The light sensing area I is used for collecting light and carrying out photoelectric conversion on the collected light. In this embodiment, the photosensitive regions I are used to form a pixel array.
The substrate 200 is used to provide a process foundation for the formation of the photosensitive structure 201.
In this embodiment, the substrate 200 is made of monocrystalline silicon; the substrate 200 may also be polysilicon or amorphous silicon; the substrate 200 may also be made of semiconductor material such as germanium, silicon germanium, gallium arsenide, or the like.
In other embodiments, the substrate may be a silicon-on-insulator substrate, a germanium-on-insulator substrate, a glass substrate, or other types of substrates.
The photosensitive structure 201 is used for absorbing light and performing photoelectric conversion.
In this embodiment, the photosensitive structure 201 is a photodiode. In other embodiments, the photosensitive structure may also be a photosensitive MOS transistor or other components that implement a photoelectric conversion function.
Referring to fig. 4, a trench 203 is formed in the isolation region II.
The first side surface of the substrate 200 exposes the top of the trench 203.
The trench 203 provides structural support for subsequent formation of isolation structures within isolation region II.
The method for forming the groove 203 comprises the following steps: forming a patterned layer 202 on the first surface of the substrate 200, wherein the patterned layer 202 exposes the first surface of the isolation region II; and etching the substrate 200 by using the patterned layer 202 as a mask, and forming the groove 203 in the isolation region II.
The process of etching the substrate 200 includes a dry etching process or a wet etching process. In this embodiment, the process of etching the substrate 200 includes a dry etching process.
In this embodiment, the material of the patterned layer 202 includes photoresist. In other embodiments, the patterned layer includes a hard mask layer and a photoresist on the hard mask layer.
After the trench 203 is formed, the patterned layer 202 is removed.
In the present embodiment, the process of removing the patterned layer 202 includes an ashing process.
Next, an isolation structure is formed in the trench 203, wherein a top surface of the isolation structure is lower than the substrate second surface.
Referring to fig. 5, an anti-reflection layer 204 is formed in the trench 203 and on the second surface of the substrate 200, and an isolation material layer 205 is formed on the surface of the anti-reflection layer 204.
The antireflection layer 204 positioned on the inner wall of the groove 203 can absorb the reflected light in the adjacent photosensitive area I, so as to avoid optical crosstalk caused by the reflected light in the adjacent photosensitive area I; the antireflection layer 204 on the second surface of the photosensitive area I can increase the transmittance of light entering the photosensitive area I through the filter layer on the second surface of the photosensitive area I, so that the light entering the photosensitive area I is increased, and the performance of the image sensor is improved.
In other embodiments, the anti-reflective layer can not be formed.
The layer of isolation material 205 provides a layer of material for subsequent formation of isolation structures within the trench 203.
In the present embodiment, the material of the anti-reflection layer 204 includes tantalum oxide.
The process of forming the anti-reflective layer 204 includes a chemical vapor deposition process, a physical vapor deposition process, or an atomic layer deposition process.
In the present embodiment, the process of forming the anti-reflection layer 204 includes a chemical vapor deposition process. The chemical vapor deposition process can quickly form the anti-reflection layer 204 with uniform thickness and dense structure.
In the present embodiment, the material of the isolation material layer 205 includes silicon oxide.
The process of forming the isolation material layer 205 includes a chemical vapor deposition process, a thermal oxidation process, or an atomic layer deposition process.
In the present embodiment, the process of forming the isolation material layer 205 includes a chemical vapor deposition process. The chemical vapor deposition process can rapidly form the isolation material layer 205 with uniform thickness and dense structure.
Referring to fig. 6, the isolation material layer 205 is etched back until the top surface of the isolation material layer 205 is lower than the second surface of the substrate 200, and the isolation structure 206 is formed in the trench 203.
The top surface of the isolation structure 206 is lower than the second surface of the substrate 200, and then a first groove is formed in the grid material layer formed on the surface of the isolation structure 206 and the second surface of the substrate 200, and the first groove is located in the isolation region surface and a part of the grid material layer on the isolation structure surface, so as to provide a position support for the self-alignment of the grid structure on the isolation region surface.
The isolation material layer 205 and the anti-reflection layer 204 have a high etching selection ratio, so that the anti-reflection layer 204 is less damaged in the process of etching back the isolation material layer 205 to form the isolation structure.
Referring to fig. 7, a grid material layer 207 is formed on the surface of the isolation structure 206 and the second surface of the substrate 200, and a first groove 208 is formed in a portion of the grid material layer on the surface of the isolation region II and the surface of the isolation structure 206.
The first groove 208 provides a position for a mask structure to be formed later, so that when the grid material layer 207 is etched by using the mask structure as a mask to form a grid structure, the grid structure is located on the second surface of the isolation region, and self-alignment of the grid structure is achieved.
The grid material layer 207 provides a material layer for the grid structure.
The material of the grid material layer 207 comprises a metal; the metal comprises one or more of copper, tungsten, nickel, chromium, titanium, tantalum and aluminum in combination.
In this embodiment, the material of the grid material layer 207 includes tungsten.
The process of forming the grid material layer 207 includes a physical vapor deposition process or an electroplating process.
In the present embodiment, the process of forming the grid material layer 207 includes a physical vapor deposition process. The physical vapor deposition process enables rapid deposition of a dense grid material layer 207 having a uniform thickness.
Since the top surface of the isolation structure 206 in the trench 203 is lower than the second surface of the substrate 200, the grid material layer 207 has a better thickness uniformity during the formation of the grid material layer 207 by using a physical vapor deposition process, so that a first groove 208 is formed in a portion of the grid material layer 207 on the surface of the isolation region II and the surface of the isolation structure 206.
The first recess 208 has a first projection on the surface of the substrate 200 and the isolation structure 206 has a second projection on the surface of the substrate 200, which second projection partially or completely coincides with the first projection.
In this embodiment, the second projection and the first projection all coincide.
The second projection is partially or completely overlapped with the first projection, so that after a mask structure is formed in the first groove 208 subsequently, when the grid material layer 207 is etched by taking the mask structure as a mask to form a grid structure, the grid structure can be accurately positioned on the second surface of the isolation region, and the self-alignment of the grid structure is realized.
Next, a mask structure is formed in the first recess 208.
In this embodiment, the mask structure includes: the mask comprises a hard mask layer and a photoresist layer positioned on the hard mask layer.
In other embodiments, the mask structure comprises: a hard mask layer.
Referring to fig. 8, a hard mask material layer 209 is formed on the surface of the grid material layer 207, the hard mask material layer has a second recess (not labeled), a photoresist material layer 210 is formed on the surface of the hard mask material layer 209, and the photoresist material layer 210 covers the second recess.
The second groove provides position support for the photoresist layer.
The second groove has a third projection on the surface of the substrate 200, the third projection partially or completely coincides with the second projection, and the third projection partially or completely coincides with the first projection.
In this embodiment, the third projection and the second projection all coincide, and the third projection and the first projection all coincide.
The third projection is partially or completely overlapped with the second projection, and the third projection is partially or completely overlapped with the first projection, so that the grid structure can be accurately positioned on the second surface of the isolation region when the grid material layer 207 is etched by taking the mask structure as a mask to form the grid structure, and the self-alignment of the grid structure is realized.
The hard mask material layer 209 and the photoresist material layer 210 provide material layers for the hard mask layer and a photoresist layer on the hard mask layer, respectively.
The material of the hard mask material layer 209 includes silicon oxide or silicon nitride.
In the present embodiment, the material of the hard mask material layer 209 includes silicon nitride.
The process of forming the hard mask material layer 209 includes a chemical vapor deposition process or an atomic layer deposition process.
In the present embodiment, the process of forming the hard mask material layer 209 includes a chemical vapor deposition process. The chemical vapor deposition process can efficiently form the hard mask material layer 209 with uniform thickness and dense film layer.
Since the grid material layer 207 has the first groove 208 therein, in the process of forming the hard mask material layer 209 by using the chemical vapor deposition process, the chemical vapor deposition process is controlled so that the thickness uniformity of the hard mask material layer 209 is better, and thus, the hard mask material layer 209 formed on the surface of the grid material layer 207 has the second groove therein.
The process of forming the photoresist material layer 210 includes a spin coating process or a spray coating process.
In the present embodiment, the process of forming the photoresist material layer 210 includes a spin coating process. The photoresist material is in a flowing state during spin coating, so that the photoresist material can cover the second groove, and the cured surface of the photoresist material layer 210 is in a planar state.
The photoresist material layer 210 covers the second groove, so that a photoresist layer can be formed in the second groove after the photoresist material layer 210 is planarized.
Referring to fig. 9, the photoresist material layer 210 is planarized until the surface of the hard mask material layer 209 is exposed, and a photoresist layer 211 is formed in the second recess; and etching the hard mask material layer 209 by using the photoresist layer 211 as a mask to form the hard mask layer 212.
In the present embodiment, the process of planarizing the photoresist material layer 210 includes an anisotropic dry etching process.
In this embodiment, the process of etching the hard mask material layer 209 by using the photoresist layer 211 as a mask includes an anisotropic dry etching process.
In other embodiments, the mask structure comprises: a hard mask layer.
Referring to fig. 10, the grid material layer 207 is etched using the mask structure as a mask, and a grid structure 213 is formed on the second surface of the isolation region II.
In this embodiment, the process of etching the grid material layer 207 includes an anisotropic dry etching process.
Therefore, the formed grid structure 213 is accurately located on the surface of the isolation region II, so that the problem that the grid structure 213 is offset at the surface of the isolation region II is solved, and the performance of the image sensor is improved.
After the grid structure 213 is formed, the mask structure is removed.
The process for removing the hard mask layer 212 includes a wet etching process or a dry etching process.
The process of removing the photoresist layer 211 includes an ashing process.
Referring to fig. 11, a filter structure 214 is formed on the second surface of the photosensitive region II; a lens 215 is formed on the filtering structure 214 and the grid structure 213.
The material of the filtering structure 214 is an organic material that can transmit monochromatic light. The filter structure 214 includes a red filter layer, a green filter layer, and a blue filter layer.
The lens 215 is used for converging light rays, so that the light rays enter the filtering structure 214 and the photosensitive structure 201 along a specific light path.
The grid structure 213 is accurately located on the surface of the isolation region II, so that the situation that partial light entering the photosensitive structure 201 from the light filtering structure 214 is blocked due to the deviation of the grid structure 213 on the surface of the isolation region II is avoided, the loss of the light entering the photosensitive structure 201 from the light filtering structure 214 is reduced, the light utilization rate is improved, and the performance of the image sensor is improved.
Fig. 12 and 13 are schematic cross-sectional structural views of an image sensor forming process in another embodiment of the present invention.
On the basis of fig. 7, please continue to refer to fig. 12, a mask structure, which is a hard mask layer 312, is formed in the first recess 208.
The forming method of the mask structure comprises the following steps: forming a hard mask material layer (not shown) on the surface of the grid material layer 207, wherein the hard mask material layer covers the first groove 208; the hard mask material layer is planarized until the surface of the grid material layer 207 is exposed, and a mask structure is formed in the first groove 208.
The material of the hard mask material layer comprises silicon oxide or silicon nitride.
In this embodiment, the material of the hard mask material layer includes silicon nitride.
The process for forming the hard mask material layer comprises a chemical vapor deposition process or an atomic layer deposition process.
In this embodiment, the process of forming the hard mask material layer includes a chemical vapor deposition process. The chemical vapor deposition process can efficiently form a hard mask material layer with a compact film layer.
Since the grid material layer 207 is provided with the first groove 208 therein, in the process of forming the hard mask material layer by using a chemical vapor deposition process, the chemical vapor deposition process is controlled so that the surface flatness of the hard mask material layer is high, so that the thick hard mask material is deposited in the first groove 208, the surface of the formed hard mask material layer is in a planar state, and after the hard mask material layer is planarized, the hard mask layer 312 can be formed in the first groove 208.
The process for planarizing the hard mask material layer comprises a chemical mechanical polishing process or an anisotropic dry etching process.
In this embodiment, the process of planarizing the hard mask material layer includes a chemical mechanical polishing process.
Referring to fig. 13, the grid material layer 207 is etched using the mask structure as a mask, and a grid structure 313 is formed on the second surface of the isolation region II.
In this embodiment, the process of etching the grid material layer 207 includes an anisotropic dry etching process.
Therefore, the formed grid structure 313 is accurately positioned on the surface of the isolation region II, so that the problem that the grid structure 313 deviates at the position of the surface of the isolation region II is solved, and the performance of the image sensor is improved.
In this embodiment, after the grid structure 313 is formed, the mask structure is subsequently removed.
The process for removing the hard mask layer 312 includes a wet etching process or a dry etching process.
After the mask structure is removed, a light filtering structure is formed on the surface of the second surface of the photosensitive area II; lenses are formed on the filtering structure and the grid structure 313. Please refer to fig. 11 and the related description for a specific forming process of the filtering structure and the lens, which are not repeated herein.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (14)

1. A method of forming an image sensor, comprising:
providing a substrate, wherein the substrate comprises a first surface and a second surface which are opposite, and the substrate comprises a plurality of photosensitive areas and an isolation area positioned between the adjacent photosensitive areas;
forming a groove in the isolation region, wherein an isolation structure is arranged in the groove, and the top surface of the isolation structure is lower than the surface of the second surface of the substrate;
forming a grid material layer on the surface of the isolation structure and the surface of the second surface of the substrate, wherein a first groove is formed in the grid material layer on the surface of the isolation region and the surface of the isolation structure;
forming a mask structure in the first groove;
and etching the grid material layer by taking the mask structure as a mask to form a grid structure on the surface of the second surface of the isolation region.
2. The method of claim 1, wherein the first recess has a first projection on the surface of the substrate, and the isolation structure has a second projection on the surface of the substrate, the second projection being partially or fully coincident with the first projection.
3. The method of forming an image sensor of claim 2, wherein the mask structure comprises: a hard mask layer; the hard mask layer is made of silicon oxide or silicon nitride.
4. The method of forming an image sensor of claim 3, wherein the mask structure further comprises: and the photoresist layer is positioned on the hard mask layer.
5. The method of forming an image sensor as claimed in claim 3, wherein the method of forming the mask structure comprises: forming a hard mask material layer on the surface of the grid material layer, wherein the hard mask material layer covers the first groove; and flattening the hard mask material layer until the surface of the grid material layer is exposed, and forming a mask structure in the first groove.
6. The method of claim 5, wherein the process of planarizing the hard mask material layer comprises a chemical mechanical polishing process or an anisotropic dry etching process.
7. The method of forming an image sensor as claimed in claim 4, wherein the method of forming the mask structure comprises: forming a hard mask material layer on the surface of the grid material layer, wherein the hard mask material layer is internally provided with a second groove, the second groove is provided with a third projection on the surface of the substrate, the third projection is partially or completely coincided with the second projection, and the third projection is partially or completely coincided with the first projection; forming a photoresist material layer on the surface of the hard mask material layer, wherein the photoresist material layer covers the second groove; flattening the photoresist material layer until the surface of the hard mask material layer is exposed, and forming a photoresist layer in the second groove; and etching the hard mask material layer by taking the photoresist layer as a mask to form the hard mask layer.
8. The method of claim 7, wherein the process of planarizing the photoresist material layer comprises an anisotropic dry etch process.
9. The method of forming an image sensor as claimed in claim 1, wherein the method of forming the isolation structure comprises: forming a patterned layer on the surface of the second surface of the substrate, wherein the patterned layer exposes the surface of the isolation region; etching the substrate by taking the patterning layer as a mask to form a groove in the isolation region; forming an isolation material layer in the groove and on the surface of the second surface of the substrate; and etching back the isolation material layer until the top surface of the isolation material layer is lower than the second surface of the substrate, and forming the isolation structure in the groove.
10. The method of claim 9, wherein the material of the spacer material layer comprises silicon oxide.
11. The method of claim 9, wherein the process of forming the spacer material layer comprises a chemical vapor deposition process, a thermal oxidation process, or an atomic layer deposition process.
12. The method of claim 1, wherein the process of etching the grid material layer comprises an anisotropic dry etching process.
13. The method of forming an image sensor of claim 1, wherein the material of the grid material layer comprises a metal; the metal comprises one or more of copper, tungsten, nickel, chromium, titanium, tantalum and aluminum in combination.
14. The method of forming an image sensor of claim 1, further comprising: forming a light filtering structure on the surface of the second surface of the photosensitive area; forming a lens on the filtering structure and the grid structure.
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CN106531750A (en) * 2015-09-10 2017-03-22 台湾积体电路制造股份有限公司 CMOS image sensor structure with crosstalk improvement
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