Method of forming backside illuminated image sensor

Abstract

A method for forming a back-illuminated image sensor includes providing a first semiconductor substrate having opposite first and second faces, thinning the second face, forming a plurality of deep trenches in the first semiconductor substrate, filling a flowable material into the deep trenches, and irradiating the flowable material with a UV light curing process to form first isolation structures to fill the deep trenches. By forming a flowable material in the deep trenches, and irradiating the flowable material with a UV light curing process to form first isolation structures to fill the deep trenches. Since the temperature of the UV light curing process is low, damage to device structures formed on the first semiconductor substrate can be reduced. In addition, the flowable material has good filling properties, and can be used to fill deep trenches with a large aspect ratio, so that the density of the finally formed first isolation structures is high, and the isolation effect can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, and in particular, to a forming method of a back-illuminated image sensor. BACKGROUND

[0002] A back-illuminated image sensor is a semiconductor device that converts optical signals into electrical signals. The back-illuminated image sensor is classified into a complementary metal-oxide semiconductor (CMOS) back-illuminated image sensor and a charge-coupled device (CCD) back-illuminated image sensor. The CMOS back-illuminated image sensor has the advantages of simple process, easy integration with other devices, small size, light weight, low power consumption and low cost. Therefore, with the development of image sensing technology, the CMOS back-illuminated image sensor is increasingly replacing the CCD back-illuminated image sensor and is applied to various electronic products. At present, the CMOS back-illuminated image sensor has been widely applied to static digital cameras, digital video cameras, medical imaging devices and vehicle imaging devices.

[0003] The CMOS back-illuminated image sensor includes a front-side-illumination (FSI) back-illuminated image sensor and a back-side-illumination (BSI) back-illuminated image sensor. In the back-illuminated back-illuminated image sensor, light is incident on a light-sensing diode in the back-illuminated image sensor from the back of the back-illuminated image sensor, thereby converting optical energy into electrical energy.

[0004] However, the existing back-illuminated image sensor still has many problems in the forming process. SUMMARY

[0005] The present application solves the technical problem of providing a forming method of a back-illuminated image sensor, which can effectively improve the performance of the back-illuminated image sensor.

[0006] To solve the above problems, the present application provides a forming method of a back-illuminated image sensor, comprising: providing a first semiconductor substrate, the first semiconductor substrate having opposite first and second surfaces; thinning the second surface; forming a plurality of deep trenches in the first semiconductor substrate; filling a flowable material into the deep trenches; using a UV light curing process to irradiate the flowable material to form a first isolation structure to fill the deep trenches.

[0007] Optionally, before the thinning of the second surface, the method further comprises: forming a plurality of second isolation structures and a plurality of photoactive regions in the first semiconductor substrate, each of the second isolation structures extending into the first semiconductor substrate from the first surface, each of the photoactive regions being disposed in the first semiconductor substrate and corresponding to a space between adjacent second isolation structures, the photoactive regions having first ions; and forming a device layer on the first surface; each of the deep trenches corresponding to each of the second isolation structures and extending from the second surface to the first surface and connecting to the corresponding second isolation structure at the bottom.

[0008] Optionally, the process of filling the flowable material into the deep trenches comprises a plasma enhanced chemical vapor deposition process.

[0009] Optionally, the process parameters of the plasma enhanced chemical vapor deposition process comprise: a reactant comprising a silicon precursor, a dopant gas, and a plasma containing gas; and a reaction temperature less than 500 degrees Celsius.

[0010] Optionally, the silicon precursor comprises one or more of ethylsilane, propylsilane, tetrasilane, neopentylsilane, and cyclohexasilane; the plasma containing gas comprises one or more of He, Ar, Kr, H2, N2, O2, O3, and NH3; and the dopant gas comprises one or more of BCl3, B2H6, BF3, PH3, and AsH3.

[0011] Optionally, the flowable material comprises one or both of doped amorphous silicon and doped polysilicon.

[0012] Optionally, the process parameters of the UV light curing process comprise: a wavelength of the UV light ranging from 100 nanometers to 400 nanometers; and a curing time ranging from 10 minutes to 4 hours.

[0013] Optionally, the UV light curing process is followed by an annealing process of the flowable material.

[0014] Optionally, the process parameters of the annealing process comprise: an annealing temperature less than 500 degrees Celsius; and an annealing time ranging from 10 minutes to 4 hours.

[0015] Optionally, the deep trenches have an aspect ratio ranging from 5:1 to 40:1.

[0016] Optionally, before the filling of the flowable material into the deep trenches, the method further comprises: forming an optimization layer on the second surface, the sidewalls, and the bottom of the deep trenches; and forming the flowable material on the optimization layer.

[0017] Optionally, the optimization layer comprises a single-layer structure or a double-layer structure.

[0018] Optionally, when the optimization layer is a single layer, the optimization layer comprises a buffer oxide layer.

[0019] Optionally, when the optimization layer is a single layer, the optimization layer comprises an HK material layer.

[0020] Optionally, when the optimization layer is a double layer, the optimization layer comprises an HK material layer and a buffer oxide layer on the HK material layer.

[0021] Optionally, the material of the buffer oxide layer comprises one or more of SiO2, TiO2, ZrO2, Al2O3, La2O3, Pr2O3, CeO2, Nd2O3, Pm2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Lu2O3 and Y2O3.

[0022] Optionally, the material of the HK material layer comprises one or more of HfO2, TiO2, HfZrO, Ta2O3, HfSiO4, ZrO2 and ZrSiO2.

[0023] Optionally, the forming method of the second isolation structure comprises: implanting second ions into the first semiconductor substrate to form the second isolation structure, the second ions being opposite in electrical type to the first ions.

[0024] Optionally, the flowable material also covers the second surface, and after the flowable material is irradiated by using a UV light curing process, an initial first isolation structure is formed, the initial first isolation structure filling the deep trench and covering the second surface; the forming method of the first isolation structure comprises: performing a planarization process on the initial first isolation structure until the buffer oxide layer is exposed, to form the first isolation structure.

[0025] Optionally, before the second surface is thinned, the method further comprises: providing a second semiconductor substrate; covering a bonding layer on the surface of the second semiconductor substrate; and bonding the first semiconductor substrate and the second semiconductor substrate by bonding the bonding layer to the device layer.

[0026] Optionally, after the first isolation structure is formed, the method further comprises: forming a plurality of grid structures, a plurality of color filter layers and a plurality of micro-lens layers on the second surface, the grid structures being located on the first isolation structure, the color filter layers being located between adjacent grid structures, and the micro-lens layers being located on the color filter layers.

[0027] Compared with the prior art, the technical scheme of the present application has the following advantages:

[0028] In the forming method of the technical scheme, the flowable material is formed in the deep trench, the flowable material is irradiated by using a UV light curing process to form a first isolation structure to fill the deep trench. Since the temperature of the UV light curing process is low, damage to a device structure formed on the first semiconductor substrate can be reduced.

[0029] In addition, the flowable material has good filling property, can be used to fill the deep trench with large aspect ratio, and is not affected by complex topography, so that the compactness of the finally formed first isolation structure is high, the isolation effect can be effectively improved, and the performance of the back-illuminated image sensor is improved.

[0030] Further, the reactants of the plasma enhanced chemical vapor deposition process include a doping gas, and the doping gas includes one or more of BCl3, B2H6, BF3, PH3 and AsH3. The flowable material formed includes one or both of doped amorphous silicon and doped polysilicon. By artificially selecting the doping gas, the first isolation structure formed from the flowable material is doped with ions opposite to the first ion, thereby improving the isolation effect of the first isolation structure on the adjacent light-sensitive region.

[0031] Further, the UV light curing process further includes annealing the flowable material at the same time or after the UV light curing process. The first isolation structure formed by the annealing process has better stability, thereby improving the isolation effect.

[0032] Further, before filling the flowable material into the deep trench, an optimization layer is formed on the second surface, the sidewall and the bottom of the deep trench, and the flowable material is formed on the optimization layer. The optimization layer includes a single-layer structure or a double-layer structure. When the optimization layer is a single layer, the optimization layer includes a buffer oxide layer or an HK material layer. When the optimization layer is a double layer, the optimization layer includes an HK material layer and a buffer oxide layer on the HK material layer. The HK material layer can passivate and repair defects on the sidewall and bottom surface of the deep trench, thereby improving the performance of the formed image sensor. The buffer oxide layer can reduce optical crosstalk when the image sensor is working.

[0033] Further, the flowable material also covers the second surface, and after the flowable material is irradiated by using a UV light curing process, an initial first isolation structure is formed, which fills the deep trench and covers the second surface; the forming method of the first isolation structure comprises: performing a planarization treatment on the initial first isolation structure until the buffer oxide layer is exposed, so as to form the first isolation structure. The buffer oxide layer not only can reduce the optical crosstalk of the image sensor during operation, but also can be used as a stop layer for the planarization treatment, so as to effectively simplify the process and improve the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 and Figure 2 is a schematic structural diagram of each step of a forming method of a back-illuminated image sensor;

[0035] Figures 3 to 10 is a schematic structural diagram of each step of a forming method of a back-illuminated image sensor in an embodiment of the present application. DETAILED DESCRIPTION

[0036] As described in the background, the existing back-illuminated image sensor still has many problems in the forming process. The following will be specifically described with reference to the drawings.

[0037] Please refer to Figure 1 , a first semiconductor substrate 100 is provided, which has opposite first and second surfaces 101 and 102; a plurality of first isolation structures 103 and a plurality of light-sensitive regions 104 are formed in the first semiconductor substrate 100, and a device layer 105 is formed on the first surface 101; each first isolation structure 103 extends into the first semiconductor substrate 100 from the first surface 101; each light-sensitive region 104 is arranged in the first semiconductor substrate 100 and corresponds to the adjacent first isolation structure 103; the light-sensitive region 104 has a first ion.

[0038] Please refer to Figure 2 , a plurality of deep trenches (not labeled) are formed in the first semiconductor substrate 100, which extend from the second surface 102 to the first surface 101 and expose the surface of the first isolation structure 104.

[0039] Please continue to refer to Figure 2 , a second isolation structure 106 is formed in the deep trench.

[0040] In one embodiment, the second isolation structure 106 is formed by using a P-type silicon material by epitaxial growth method. However, due to the high temperature in the process of epitaxial growth, the device structure is easily damaged.

[0041] In another embodiment, the second isolation structure 106 can also be formed by an atomic layer deposition (ALD) process. However, the ALD process has weak filling capability for some complex-shaped trenches (such as cross-shaped intersection trenches), and the resulting second isolation structure 106 has low compactness, which affects the isolation effect.

[0042] On this basis, the application provides a forming method of a back-illuminated image sensor, which fills a deep trench by forming a flowable material in the deep trench and irradiating the flowable material by a UV light curing process to form a first isolation structure.

[0043] In order to make the above objectives, characteristics and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the drawings.

[0044] Figures 3 to 10 is a schematic structural diagram of each step of a forming method of a back-illuminated image sensor in an embodiment of the present application.

[0045] Please refer to Figure 3 , a first semiconductor substrate 200 is provided, which has opposite first and second surfaces 201 and 202.

[0046] In this embodiment, the material of the first semiconductor substrate 200 is silicon; in other embodiments, the material of the first semiconductor substrate can also be germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium.

[0047] Please continue to refer to Figure 3 , a plurality of second isolation structures 203 and a plurality of light-sensitive regions 204 are formed in the first semiconductor substrate 200, and a device layer 205 is formed on the first surface 201.

[0048] In this embodiment, each of the second isolation structures 203 extends into the first semiconductor substrate 200 from the first surface 201, each of the light-sensitive regions 204 is arranged in the first semiconductor substrate 200 and corresponds to the adjacent second isolation structures 203, and the light-sensitive region 204 has a first ion.

[0049] In the embodiment, the method for forming the light sensing region 204 includes: forming a first patterning layer (not shown) on the first surface 201, the first patterning layer exposes part of the first surface 201; implanting the first ions into the first semiconductor substrate 200 with the first patterning layer as a mask to form the light sensing region 204.

[0050] In the embodiment, the method for forming the second isolation structure 203 includes: forming a second patterning layer (not shown) on the first surface 201, the second patterning layer covers the light sensing region 204 and exposes part of the first surface 201; implanting second ions into the first semiconductor substrate 300 with the second patterning layer as a mask to form the second isolation structure 203, the second ions are opposite to the first ions in electrical type.

[0051] In the embodiment, the first ions are N-type ions. In other embodiments, the first ions can also be P-type ions.

[0052] In the embodiment, the second ions are P-type ions. In other embodiments, when the first ions are P-type ions, the second ions are N-type ions.

[0053] The P-type ions include boron ions or indium ions. The N-type ions include phosphorus ions or arsenic ions.

[0054] In the embodiment, the first semiconductor substrate 200 is doped with a P-type well region (not shown) due to the N-type ions doped in the light sensing region 204. Therefore, in the first semiconductor substrate 200, a photodiode structure is formed at the junction of the light sensing region 204 and the P-type well region. Subsequently, the photodiode structure is used to form an electrical signal from the excited electrons by irradiating light onto the light sensing region 204 from the second surface 202.

[0055] In the embodiment, the second isolation structure 203 is formed by an ion implantation process. In other embodiments, the second isolation structure can also be a trench filling structure.

[0056] The second isolation structure 203 isolates adjacent light sensing regions, thereby reducing optical and electrical crosstalk between the light sensing regions 204.

[0057] In the embodiment, the device layer 205 includes a device structure and an electrical interconnection layer (not shown) electrically connected to the device structure.

[0058] The device structure includes one or more of a transistor structure, a capacitor structure, an inductor structure, and a resistor structure.

[0059] Please refer to Figure 4 , a second semiconductor substrate 300 is provided; a bonding layer 301 is formed on the surface of the second semiconductor substrate 300; the bonding layer 301 is opposite to the device layer 205 to bond the first semiconductor substrate 200 and the second semiconductor substrate 300.

[0060] In the embodiment, the material of the second semiconductor substrate 300 is silicon. In other embodiments, the material of the second semiconductor substrate can also be germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium.

[0061] In the embodiment, the bonding layer 301 is a silicon layer; in other embodiments, the bonding layer can also be an oxide layer, and the material of the oxide layer includes silicon dioxide, silicon oxynitride or silicon oxynitride.

[0062] In the embodiment, the silicon layer is a film layer formed additionally on the second semiconductor substrate 300; in other embodiments, the silicon layer can also be a part of the silicon substrate of the second semiconductor substrate.

[0063] Please refer to Figure 5 , the second surface 202 is thinned.

[0064] Since the initial thickness of the first semiconductor substrate 200 is large, in order to reduce the distance of external light incident from the second surface 200 to the photosensitive area 204, thereby improving the sensitivity of the back-illuminated image sensor, the first semiconductor substrate 200 needs to be thinned.

[0065] The process of thinning the second surface 202 includes a physical and mechanical polishing process, a chemical and mechanical polishing process or a wet etching process. In the embodiment, the process of thinning the second surface 202 adopts a chemical and mechanical polishing process.

[0066] Please refer to Figure 6 , a plurality of deep trenches 206 are formed in the first semiconductor substrate 200.

[0067] In the embodiment, each of the deep trenches 206 corresponds to each of the second isolation structures 203, extends from the second surface 202 to the first surface 201, and the bottom is connected to the corresponding second isolation structure 203.

[0068] In the embodiment, the forming method of the plurality of deep trenches 206 includes: forming a third patterned layer (not shown) on the second surface 202, which exposes part of the second surface 202; etching the first semiconductor substrate 200 with the third patterned layer as a mask until the surface of the second isolation structure 203 is exposed, thereby forming a plurality of deep trenches 206.

[0069] In the embodiment, the etching process is a dry etching process. In other embodiments, the etching process can also be a wet etching process.

[0070] In the embodiment, the deep trench 206 has a depth-to-width ratio of 5:1-40:1.

[0071] Please refer to Figure 7 After forming the deep trenches 206, an optimization layer 207 is formed on the second surface 202, the sidewalls and the bottom of the deep trenches 206.

[0072] In the embodiment, the optimization layer 207 has a double-layer structure, and the optimization layer 207 includes an HK material layer and a buffer oxide layer on the HK material layer.

[0073] The HK material layer can passivate and repair defects on the sidewalls and the bottom of the deep trenches 206, thereby improving the performance of the formed image sensor. The buffer oxide layer can reduce optical crosstalk during the operation of the image sensor.

[0074] In other embodiments, the optimization layer can also have a single-layer structure, and the optimization layer includes a buffer oxide layer or an HK material layer.

[0075] The material of the buffer oxide layer includes one or more of SiO2, TiO2, ZrO2, Al2O3, La2O3, Pr2O3, CeO2, Nd2O3, Pm2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Lu2O3, and Y2O3.

[0076] The material of the HK material layer includes one or more of HfO2, TiO2, HfZrO, Ta2O3, HfSiO4, ZrO2, and ZrSiO2.

[0077] Please refer to Figure 8 After forming the optimization layer 207, a flowable material 208 is filled into the deep trenches 206.

[0078] In the embodiment, the flowable material 208 has good filling properties and can be used to fill the deep trenches 206 with a large depth-to-width ratio without being affected by complex topography. The first isolation structure formed subsequently has high compactness, which can effectively improve the isolation effect and thereby improve the performance of the back-illuminated image sensor.

[0079] In the embodiment, the process of filling the flowable material 208 into the deep trench 206 includes a plasma enhanced chemical vapor deposition process.

[0080] In the embodiment, the process parameters of the plasma enhanced chemical vapor deposition process include: the reactants include: a silicon precursor, a doping gas, a plasma containing plasma gas; the reaction temperature is less than 500 degrees Celsius.

[0081] The silicon precursor includes one or more of ethylsilane, propylsilane, tetrasilane, neopentasilane and cyclohexasilane.

[0082] The plasma gas includes one or more of He, Ar, Kr, H2, N2, O2, O3 and NH3.

[0083] The doping gas includes one or more of BC l3 , B2H6, BF3, PH3 and AsH3. So that the flowable material 208 formed includes one or both of doped amorphous silicon and doped polysilicon. Through artificial selection of the doping gas, the first isolation structure subsequently formed by the flowable material 208 is doped with ions opposite to the first ion, thereby improving the isolation effect of the first isolation structure on the adjacent light sensing region.

[0084] In the embodiment, since the first ion is an N-type ion. Therefore, the doping gas is selected from one or more of BC l3 , B2H6 and BF3.

[0085] In other embodiments, if the first ion is a P-type ion, the doping gas is selected from one or more of PH3 and AsH3.

[0086] In the embodiment, the flowable material 208 also covers the second surface 202. In other embodiments, the flowable material can also only fill the deep trench.

[0087] Please refer to Figure 9 , the flowable material 208 is irradiated by a UV light curing process to form a first isolation structure 209 to fill the deep trench 206.

[0088] By forming a flowable material 208 in the deep trench, the flowable material 208 is irradiated by a UV light curing process to form a first isolation structure 209 to fill the deep trench. Since the temperature of the UV light curing process is low, it can reduce the damage to the device structure formed on the first semiconductor substrate 200, thereby improving the performance of the back-illuminated image sensor.

[0089] In the embodiment, the process parameters of the UV light curing process include: the wavelength of the UV light is 100-400 nm; the curing time is 10 min-4 h.

[0090] In the embodiment, the UV light curing process is followed by an annealing process of the flowable material 208. The annealing process makes the first isolation structure 209 more stable, thus improving the isolation effect.

[0091] In the embodiment, the process parameters of the annealing process include: the annealing temperature is less than 500 °C; the annealing time is 10 min-4 h.

[0092] In the embodiment, after the flowable material 208 covers the second surface and is irradiated by the UV light, an initial first isolation structure (not shown) is formed, which fills the deep trench 206 and covers the second surface 202. The first isolation structure 209 is formed by planarizing the initial first isolation structure until the buffer oxide layer is exposed.

[0093] In the embodiment, the buffer oxide layer not only reduces the optical crosstalk of the image sensor during operation, but also serves as a stop layer for the planarization process, thus effectively simplifying the process and improving the production efficiency.

[0094] In the embodiment, the planarization process adopts a chemical mechanical polishing process.

[0095] Please refer to Figure 10 After the first isolation structure 209 is formed, a plurality of grid structures 210, a plurality of color filter layers 211 and a plurality of micro-lens layers 212 are formed on the second surface 202. The grid structures 210 are located on the first isolation structure 209, the color filter layers 211 are located between adjacent grid structures 210, and the micro-lens layers 212 are located on the color filter layers 211.

[0096] In the embodiment, the grid structure 210 is formed by: depositing a grid film (not shown) on the second surface 202; forming a fourth patterned layer (not shown) on the surface of the grid film, which exposes part of the surface of the grid film; using the fourth patterned layer as a mask to etch the grid film until the second surface 202 is exposed, thus forming a plurality of grid structures 210.

[0097] In the embodiment, the material of the grid structure 210 includes tungsten, titanium or aluminum.

[0098] In the embodiment, the grid structure 210 is used to cause optical crosstalk between adjacent color filter layers 211.

[0099] In the embodiment, the color filter layer 211 includes a red filter layer, a green filter layer or a blue filter layer, and a color filter layer 211 of one color is formed above a photosensitive region 204. Incident light is filtered by the color filter layer 211 of one color to become monochromatic light (red light, green light or blue light) and then irradiated onto the photosensitive region 204, so that the photosensitive region 204 generates electrons.

[0100] In the embodiment, the microlens layer 212 is used to focus incident light and converge the incident light onto the photosensitive region 204.

[0101] Although the present application has been disclosed with reference to the above embodiments, the present application is not limited to the above embodiments. Any person skilled in the art can make various modifications and changes without departing from the spirit and scope of the present application, and the scope of protection of the present application should be defined by the scope of claims.

Claims

1. A method for forming a back-illuminated image sensor, characterized in that, include: A first semiconductor substrate is provided, the first semiconductor substrate having opposing first and second surfaces; The second surface is thinned. Several deep trenches are formed within the first semiconductor substrate; Fill the deep trench with a flowable material; The flowable material is irradiated using a UV curing process to form a first insulating structure to fill the deep trench; wherein... A plurality of photosensitive areas are formed in the first semiconductor substrate, and the photosensitive areas contain first ions; The process of filling the deep trench with a flowable material is performed using plasma-enhanced chemical vapor deposition. The process parameters of the plasma-enhanced chemical vapor deposition process include: reactants including: silicon precursor, dopant gas, and plasma containing plasma gas, wherein the dopant gas causes the first isolation structure to be doped with ions that are inversely related to the first ions, so as to improve the isolation effect of the first isolation structure on the adjacent photosensitive areas.

2. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, Before thinning the second surface, the method further includes: forming a plurality of second isolation structures and a plurality of photosensitive areas in the first semiconductor substrate, and forming a device layer on the first surface, wherein each second isolation structure extends from the first surface into the first semiconductor substrate, and each photosensitive area is disposed in the first semiconductor substrate and is correspondingly disposed between adjacent second isolation structures. Each of the deep trenches corresponds to each of the second isolation structures, extends from the second surface to the first surface, and is connected at the bottom to the corresponding second isolation structure.

3. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, The process parameters of the plasma-enhanced chemical vapor deposition process also include: a reaction temperature of less than 500 degrees Celsius.

4. The method for forming a back-illuminated image sensor as described in claim 3, characterized in that, The silicon precursor includes one or more of the following: silane, propane, tetrasilane, neopentyl silane, and cyclohexyl silane; the plasma gas includes one or more of the following: He, Ar, Kr, H2, N2, O2, O3, and NH3; the doping gas includes: BCl3, B2H6, and BF2. 3、 One or more of PH3 and AsH3.

5. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, The fluid material includes one or both of doped amorphous silicon and doped polycrystalline silicon.

6. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, The process parameters of the UV curing process include: the wavelength of the UV light is 100 nanometers to 400 nanometers; the curing time is 10 minutes to 4 hours.

7. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, The UV curing process may be performed simultaneously with or after the annealing of the flowable material.

8. The method for forming a back-illuminated image sensor as described in claim 7, characterized in that, The annealing process parameters include: annealing temperature less than 500 degrees Celsius; annealing time of 10 minutes to 4 hours.

9. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, The depth-to-width ratio of the deep trench is 5:1 to 40:

1.

10. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, Before filling the deep trench with a flowable material, the method further includes: forming an optimization layer on the second surface, the sidewalls of the deep trench, and the bottom; the flowable material is formed on the optimization layer.

11. The method for forming a back-illuminated image sensor as described in claim 10, characterized in that, The optimization layer includes a single-layer structure or a double-layer structure.

12. The method for forming a back-illuminated image sensor as described in claim 11, characterized in that, When the optimization layer is a single layer, the optimization layer includes: a buffer oxide layer.

13. The method for forming a back-illuminated image sensor as described in claim 11, characterized in that, When the optimization layer is a single layer, the optimization layer includes: an HK material layer.

14. The method for forming a back-illuminated image sensor as described in claim 11, characterized in that, When the optimization layer is a two-layer structure, the optimization layer includes: an HK material layer and a buffer oxide layer located on the HK material layer.

15. The method for forming a back-illuminated image sensor as described in claim 12 or 14, characterized in that, The materials of the buffer oxide layer include one or more of the following: SiO2, TiO2, ZrO2, Al2O3, La2O3, Pr2O3, CeO2, Nd2O3, Pm2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, Lu2O3, and Y2O3.

16. The method for forming a back-illuminated image sensor as described in claim 13 or 14, characterized in that, The materials of the HK material layer include one or more of HfO2, TiO2, HfZrO, Ta2O3, HfSiO4, ZrO2, and ZrSiO2.

17. The method for forming a back-illuminated image sensor as described in claim 2, characterized in that, The method for forming the second isolation structure includes: implanting a second ion into the first semiconductor substrate to form the second isolation structure, wherein the second ion has the opposite electrical type to the first ion.

18. The method for forming a back-illuminated image sensor as described in claim 12 or 14, characterized in that, The fluid material also covers the second surface. After the fluid material is irradiated with a UV curing process, an initial first isolation structure is formed. The initial first isolation structure fills the deep trench and covers the second surface. The method for forming the first isolation structure includes: planarizing the initial first isolation structure until the buffer oxide layer is exposed, thereby forming the first isolation structure.

19. The method for forming a back-illuminated image sensor as described in claim 2, characterized in that, Before thinning the second surface, the method further includes: providing a second semiconductor substrate; covering the surface of the second semiconductor substrate with a bonding layer; and aligning the bonding layer with the device layer to bond the first semiconductor substrate and the second semiconductor substrate.

20. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, After forming the first isolation structure, the method further includes: forming a plurality of grid structures, a plurality of color filter layers, and a plurality of micro-convex lens layers on the second surface, wherein the grid structures are located on the first isolation structure, the color filter layers are located between adjacent grid structures, and the micro-convex lens layers are located on the color filter layers.

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