Backside illuminated image sensor and method of forming the same

Abstract

A back-illuminated image sensor and a forming method thereof, wherein the forming method comprises: providing a first substrate, the first substrate comprising a pixel region having first ions therein, the first substrate having opposite first and second faces; forming a plurality of deep trenches in the pixel region; forming an intrinsic epitaxial layer on the sidewalls of the deep trenches; forming a doped epitaxial layer on the surface of the intrinsic epitaxial layer, the doped epitaxial layer having second ions therein; forming a fill layer on the first face, the fill layer sealing the openings of the deep trenches; and forming a device layer on the first face after forming the fill layer, the device layer having a plurality of device structures therein. By forming the intrinsic epitaxial layer and the doped epitaxial layer in the deep trenches first, the sidewall damage of the deep trenches is repaired by the intrinsic epitaxial layer; and then the device layer is formed on the first face. Thus, the problem of melting the device structures due to high temperature during the formation of the intrinsic epitaxial layer and the doped epitaxial layer is effectively avoided, and the performance of the back-illuminated image sensor formed finally is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a back-illuminated image sensor and a method for forming the same. Background Technology

[0002] A back-illuminated image sensor is a semiconductor device that converts light signals into electrical signals. Back-illuminated image sensors are divided into complementary metal-oxide (CMOS) back-illuminated image sensors and charge-coupled device (CCD) back-illuminated image sensors. CMOS back-illuminated image sensors have advantages such as simple manufacturing process, easy integration with other devices, small size, light weight, low power consumption, and low cost. Therefore, with the development of image sensing technology, CMOS back-illuminated image sensors are increasingly replacing CCD back-illuminated image sensors in various electronic products. Currently, CMOS back-illuminated image sensors are widely used in still digital cameras, digital camcorders, medical imaging devices, and automotive imaging devices.

[0003] Deep trench isolation (BDTI) materials in CMOS back-illuminated image sensors typically use oxides or other dielectric materials. They utilize total internal reflection of incident light at a certain angle to prevent optical crosstalk. With continuous technological advancements, the extinction coefficients (K-values) of most metals are much higher than those of dielectric materials. For example, at a wavelength of 600 nm, the K-value of tungsten is 6.04, while the K-value of silicon oxide is close to 0. Therefore, using metals as BDTI deep trench filling materials, such as tungsten, is highly advantageous because tungsten is opaque at any angle, significantly reducing the probability of optical crosstalk.

[0004] However, existing back-illuminated image sensors still have many problems in their fabrication process. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a back-illuminated image sensor and a method for forming the same, thereby improving device performance.

[0006] To address the aforementioned problems, the present invention provides a method for forming a back-illuminated image sensor, comprising: providing a first substrate, the first substrate including a pixel region, the pixel region having a first ion, and the first substrate having a first surface and a second surface opposite to each other; forming a plurality of deep trenches in the pixel region, the deep trenches extending from the first surface to the second surface; forming an intrinsic epitaxial layer on the sidewalls of the deep trenches; forming a doped epitaxial layer on the surface of the intrinsic epitaxial layer, the doped epitaxial layer having a second ion, the second ion having a different electrical type than the first ion; forming a filling layer on the first surface, the filling layer closing the opening of the deep trenches; and after forming the filling layer, forming a device layer on the first surface, the device layer having a plurality of device structures.

[0007] Optionally, the first substrate further includes a marking region; during the formation of the deep trench, the method further includes: forming a marking opening in the marking region, the marking opening extending from the first surface to the second surface; the marking opening having a first depth dimension, the deep trench having a second depth dimension, the second depth dimension being greater than the first depth dimension.

[0008] Optionally, the first depth dimension ranges from 0.5 micrometers to 0.8 micrometers; the second depth dimension ranges from 3 micrometers to 4 micrometers.

[0009] Optionally, the method for forming the marking opening and the deep trench includes: forming a first patterned layer on the first surface, the first patterned layer exposing a portion of the first surface; etching the first substrate using the first patterned layer as a mask to form the marking opening in the marking area and a plurality of initial deep trenches in the pixel area; removing the first patterned layer; forming a sacrificial layer on the first surface, the sacrificial layer covering the marking opening; after forming the sacrificial layer, etching the initial deep trenches to form the deep trenches; and after forming the deep trenches, removing the sacrificial layer.

[0010] Optionally, after forming the doped epitaxial layer, the method further includes forming a marker structure within the marker opening.

[0011] Optionally, the material of the marking structure is different from the material of the first substrate; the material of the marking structure includes silicon oxide.

[0012] Optionally, the method for forming the filling layer includes: forming a barrier structure in the deep trench, the barrier structure covering the bottom surface and part of the sidewall of the doped epitaxial layer, and the top surface of the barrier structure being lower than the top surface of the doped epitaxial layer; forming an initial filling layer on the exposed sidewall of the doped epitaxial layer and the first surface using a sampling epitaxial growth process; and planarizing the initial filling layer to form the filling layer.

[0013] Optionally, after forming the device layer, the method further includes: providing a second substrate; forming a bonding layer on the surface of the second substrate; and positioning the bonding layer opposite to the device layer to bond the first substrate and the second substrate.

[0014] Optionally, the device structure includes one or more of the following: transistor structure, capacitor structure, resistor structure, inductor structure, and electrical interconnection structure.

[0015] Optionally, after bonding the first substrate and the second substrate, the method further includes: thinning the second surface and exposing the deep trench from the second surface to the first surface.

[0016] Optionally, the thickness of the intrinsic epitaxial layer is 80 nanometers to 120 nanometers.

[0017] Optionally, the thickness of the doped epitaxial layer is 40 nanometers to 80 nanometers.

[0018] Accordingly, the present invention also provides a back-illuminated image sensor, comprising: a first substrate, the first substrate including a pixel region, the pixel region having a first ion, the first substrate having a first surface and a second surface opposite to each other; a plurality of deep trenches located in the pixel region, the deep trenches penetrating the first substrate from the first surface to the second surface; an intrinsic epitaxial layer located on the sidewall of the deep trench; a doped epitaxial layer located on the surface of the intrinsic epitaxial layer, the doped epitaxial layer having a second ion, the second ion having a different electrical type than the first ion; a filling layer located on the first surface, the filling layer closing the opening of the deep trench; and a device layer located on the first surface, the device layer having a plurality of device structures.

[0019] Optionally, the first substrate further includes a marking area; the back-illuminated image sensor further includes: a marking opening located within the marking area, the marking opening extending from the first surface to the second surface; and a marking structure located within the marking opening.

[0020] Optionally, the material of the marking structure is different from the material of the first substrate; the material of the marking structure includes silicon oxide.

[0021] Optionally, it further includes: a second substrate; and a bonding layer located on the surface of the second substrate, the bonding layer being opposite to the device layer to bond the first substrate and the second substrate.

[0022] Optionally, the device structure includes one or more of the following: transistor structure, capacitor structure, resistor structure, inductor structure, and electrical interconnection structure.

[0023] Optionally, the thickness of the intrinsic epitaxial layer is 80 nanometers to 120 nanometers.

[0024] Optionally, the thickness of the doped epitaxial layer is 40 nanometers to 80 nanometers.

[0025] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0026] In the method for forming a back-illuminated image sensor according to the technical solution of the present invention, an intrinsic epitaxial layer and a doped epitaxial layer are first formed in a deep trench, and the intrinsic epitaxial layer is used to repair the sidewall damage of the deep trench; then, a device layer is formed on the first surface. Therefore, the problem of the device structure melting due to the high temperature during the formation of the intrinsic epitaxial layer and the doped epitaxial layer can be effectively avoided, thereby effectively improving the performance of the finally formed back-illuminated image sensor.

[0027] Furthermore, the first substrate also includes a marking region; during the formation of the deep trench, the process further includes: forming a marking opening within the marking region, the marking opening extending from the first surface to the second surface; after forming the doped epitaxial layer, the process further includes: forming a marking structure within the marking opening. Since the marking opening is formed simultaneously during the formation of the deep trench, it avoids the need for a separate photomask etching process to form the marking opening, thereby effectively reducing process steps and lowering manufacturing costs. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structural steps in the formation of a back-illuminated image sensor;

[0029] Figures 2 to 13 This is a schematic diagram of the structure of each step in the method for forming a back-illuminated image sensor in an embodiment of the present invention. Detailed Implementation

[0030] As described in the background section, existing back-illuminated image sensors still have many problems in their fabrication process. These will be explained in detail below with reference to the accompanying drawings.

[0031] Figure 1 This is a schematic diagram of the structural steps in the formation of a back-illuminated image sensor.

[0032] Please refer to Figure 1A first substrate 100 is provided, the first substrate 100 having a first ion, and the first substrate 100 having a first surface 101 and a second surface 102 opposite to each other; a first isolation structure 103 is formed in the first substrate 100, the first isolation structure 103 extending from the first surface 101 to the second surface 102; a device layer 104 is formed on the first surface 101, the device layer 104 having a plurality of device structures (not shown); the second surface 102 is thinned; after the thinning process, a plurality of deep trenches (not shown) are formed in the first substrate 100, the deep trenches extending from the second surface 102 to the first surface 101; an intrinsic epitaxial layer 105 is formed on the sidewall of the deep trenches; a doped epitaxial layer 106 is formed on the surface of the intrinsic epitaxial layer 105, the doped epitaxial layer 106 having a second ion, the second ion having a different electrical type than the first ion, to form a photodiode.

[0033] In this embodiment, a device layer 104 is first formed on the first surface 101, and then an intrinsic epitaxial layer 105 and a doped epitaxial layer 106 are formed in the deep trench. The intrinsic epitaxial layer 104 is used to repair sidewall damage caused during the etching of the deep trench. However, both the formation of the intrinsic epitaxial layer 105 and the doped epitaxial layer 106 involve high-temperature processing, which can easily melt the metal in the formed device structure, thereby affecting the performance of the final back-illuminated image sensor.

[0034] Based on this, the present invention provides a method for forming a back-illuminated image sensor. This method involves first forming an intrinsic epitaxial layer and a doped epitaxial layer within a deep trench, using the intrinsic epitaxial layer to repair sidewall damage in the deep trench; then forming a device layer on the first surface. This effectively avoids the problem of the high temperatures during the formation of the intrinsic epitaxial layer and the doped epitaxial layer melting the metal in the device structure, thereby effectively improving the performance of the final back-illuminated image sensor.

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0036] Figures 2 to 13 This is a schematic diagram of the structure of each step in the method for forming a back-illuminated image sensor in an embodiment of the present invention.

[0037] Please refer to Figure 2 A first substrate 200 is provided, the first substrate 200 includes a pixel region I, the pixel region I has a first ion, and the first substrate 200 has a first surface 201 and a second surface 202 opposite to each other.

[0038] In this embodiment, the material of the first substrate 200 is silicon; in other embodiments, the material of the first substrate may also be germanium, silicon germanide, silicon carbide, gallium arsenide or indium gallium.

[0039] In this embodiment, the first ion is an N-type ion.

[0040] The N-type ion includes either phosphorus ions or arsenic ions. In this embodiment, the N-type ion is a phosphorus ion.

[0041] In this embodiment, the first substrate 200 further includes a marking region II. The pixel region I is used to form pixel units, and the marking region II is used to form a marking structure, which serves to align the pixel units during the formation process.

[0042] In this embodiment, after providing the first substrate 200, the method further includes: forming a plurality of deep trenches within the pixel region I, the deep trenches extending from the first surface 201 to the second surface 202; during the formation of the deep trenches, the method further includes: forming a marking opening within the marking region II, the marking opening extending from the first surface 201 to the second surface 202. For the specific formation process of the deep trenches and the marking openings, please refer to [reference needed]. Figures 3 to 5 .

[0043] Please refer to Figure 3 A mask structure 203 is formed on the first surface 201.

[0044] In this embodiment, the mask structure 203 includes: a first mask layer, a second mask layer located on the first mask layer, and a third mask layer (not shown) located on the second mask layer.

[0045] In this embodiment, the first mask layer and the third mask layer are both made of silicon oxide, and the second mask layer is made of silicon nitride.

[0046] Please refer to Figure 4 A first patterned layer (not shown) is formed on the first surface 201, exposing a portion of the first surface 201; the first substrate 200 is etched using the first patterned layer as a mask, the mark opening 204 is formed in the mark area II, and a plurality of initial deep trenches 205 are formed in the pixel area I; the first patterned layer is removed.

[0047] In this embodiment, the first patterning layer is made of photoresist.

[0048] In this embodiment, the process of removing the first patterned layer is an ashing process.

[0049] Please refer to Figure 5 A sacrificial layer (not shown) is formed on the first surface 201, the sacrificial layer covering the marking opening 204; after forming the sacrificial layer, the initial deep trench 205 is etched to form the deep trench 206; after forming the deep trench 206, the sacrificial layer is removed.

[0050] In this embodiment, since the marking opening 204 is formed simultaneously during the formation of the deep trench 206, it is possible to avoid forming the marking opening 204 separately using a photomask etching process, thereby effectively reducing process steps and lowering manufacturing costs.

[0051] In this embodiment, the marking opening 204 has a first depth dimension d1, and the deep groove 206 has a second depth dimension d2, the second depth dimension d2 being greater than the first depth dimension d1.

[0052] In this embodiment, the range of the first depth dimension d1 is 0.5 micrometers to 0.8 micrometers; the range of the second depth dimension d2 is 3 micrometers to 4 micrometers.

[0053] In this embodiment, after forming the deep trench, the method further includes removing the third mask layer.

[0054] Please refer to Figure 6 An intrinsic epitaxial layer 207 is formed on the sidewall of the deep trench 206.

[0055] In this embodiment, the intrinsic epitaxial layer 207 is formed using an epitaxial growth process. The intrinsic epitaxial layer 207 is used to repair the etching damage caused to the sidewalls of the deep trench 206 during the etching process of forming the deep trench 206.

[0056] In this embodiment, the thickness of the intrinsic epitaxial layer 207 is 80 nanometers to 120 nanometers.

[0057] Please refer to Figure 7 A doped epitaxial layer 208 is formed on the surface of the intrinsic epitaxial layer 207. The doped epitaxial layer 208 contains a second ion, which has a different electrical type from the first ion.

[0058] In this embodiment, the doped epitaxial layer 208 is formed using an epitaxial growth process.

[0059] In this embodiment, the second ion is a P-type ion.

[0060] The P-type ion includes boron ions or indium ions. In this embodiment, the P-type ion is a boron ion.

[0061] Because the first ion and the second ion have different electrical types, both will diffuse to a certain extent, thus forming a photodiode structure within the intrinsic epitaxial layer 207. Subsequently, light shines from the second surface 202 onto the first substrate 200, causing the first substrate 200 to emit electrons. The photodiode structure is used to convert the emitted electrons into an electrical signal.

[0062] In this embodiment, the thickness of the doped epitaxial layer 208 is 40 nanometers to 80 nanometers.

[0063] In this embodiment, since a global process is used, during the formation of the intrinsic epitaxial layer 207 and the doped epitaxial layer 208, the intrinsic epitaxial layer 207 and the doped epitaxial layer 208 are also formed on the sidewall and bottom surface of the marked opening 204.

[0064] After forming the doped epitaxial layer 208, the process further includes: forming a filling layer on the first surface 201, the filling layer sealing the opening of the deep trench 207. For the specific formation process of the filling layer, please refer to [reference needed]. Figures 8 to 9 .

[0065] Please refer to Figure 8 A barrier structure 209 is formed within the deep trench 206. The barrier structure 209 covers the bottom surface and part of the sidewalls of the doped epitaxial layer 208, and the top surface of the barrier structure 209 is lower than the top surface of the doped epitaxial layer 208.

[0066] In this embodiment, the blocking structure 209 includes: a first blocking layer and a second blocking layer (not shown) located on the first blocking layer.

[0067] In this embodiment, the first barrier layer is made of silicon oxide; the second barrier layer is made of silicon nitride.

[0068] In this embodiment, since the filling layer only needs to partially fill the deep trench 206, and does not need to completely fill the deep trench 206, the formed barrier structure 209 needs to cover the bottom surface and part of the sidewall of the doped epitaxial layer 208, and the top surface of the barrier structure 209 is lower than the top surface of the doped epitaxial layer 208.

[0069] Please refer to Figure 9 The sampling epitaxial growth process forms an initial filling layer (not shown) on the exposed sidewalls of the doped epitaxial layer 209 and the first surface 201; the initial filling layer is planarized to form the filling layer 210.

[0070] Since epitaxial growth can be performed on the surface of semiconductor materials, the doped epitaxial layer 208 covered by the barrier structure 209 does not grow the filling layer, thus enabling the filling layer to partially fill the deep trench 206.

[0071] In this embodiment, since a global process is used, the filling layer 210 is also formed on the sidewall and bottom surface of the marking opening 204 during the formation of the filling layer 210.

[0072] Please refer to Figure 10 After the filling layer 210 is formed, a marking structure 211 is formed within the marking opening 204.

[0073] In this embodiment, the method for forming the marking structure 211 includes: forming a marking material layer (not shown) inside the marking opening 204 and on the first surface 201; and planarizing the marking material layer until the top surface of the second mask layer is exposed, thereby forming the marking structure 211.

[0074] In this embodiment, the material of the marking structure 211 is different from the material of the first substrate 200; the material of the marking structure 211 is silicon oxide.

[0075] Please continue to refer to this. Figure 10 In this embodiment, after the marking structure 211 is formed, the first mask layer and the second mask layer are removed; the marking structure 211 and the filling layer 210 are planarized until the first surface 201 is exposed.

[0076] In this embodiment, the planarization process employs a chemical mechanical polishing process.

[0077] Please refer to Figure 11 After planarization, a device layer 212 is formed on the first surface 201, and the device layer 212 has a plurality of device structures (not shown).

[0078] In this embodiment, an intrinsic epitaxial layer 207 and a doped epitaxial layer 208 are first formed within the deep trench 206, and the intrinsic epitaxial layer 207 is used to repair sidewall damage to the deep trench 206; then, a device layer 212 is formed on the first surface 201. Therefore, the problem of the device structure melting due to the high temperature during the formation of the intrinsic epitaxial layer 207 and the doped epitaxial layer 208 can be effectively avoided, thereby effectively improving the performance of the final back-illuminated image sensor.

[0079] In this embodiment, the device structure includes one or more of the following: transistor structure, capacitor structure, resistor structure, inductor structure, and electrical interconnection structure.

[0080] Please refer to Figure 12 After forming the device layer 212, a second substrate 300 is provided; a bonding layer 301 is formed on the surface of the second substrate 300; the bonding layer 301 is positioned opposite the device layer 212 to bond the first substrate 200 and the second substrate 300.

[0081] In this embodiment, the material of the second substrate 300 is silicon. In other embodiments, the material of the second substrate may also be germanium, silicon germanide, silicon carbide, gallium arsenide, or indium gallium ionide.

[0082] In this embodiment, the bonding layer 301 is a silicon layer; in other embodiments, the bonding layer may also be an oxide layer, and the material of the oxide layer includes silicon dioxide, silicon oxynitride, or silicon oxynitride.

[0083] In this embodiment, the bonding layer 301 is an additional film layer formed on the second substrate 300; in other embodiments, the bonding layer may also be part of the silicon substrate of the second substrate.

[0084] Please refer to Figure 13 After bonding the first substrate 200 and the second substrate 300, the second surface 202 is thinned, and the deep trench 206 is exposed from the second surface 202 to the first surface 201.

[0085] In this embodiment, since the initial thickness of the first substrate 200 is relatively large, in order to improve the sensitivity of the back-illuminated image sensor, the first substrate 200 needs to be thinned.

[0086] The thinning process for the second surface 202 includes physical mechanical polishing (PMP), chemical mechanical polishing (CMP), or wet etching. In this embodiment, the thinning process for the second surface 202 is CMP.

[0087] In this embodiment, after the thinning process, the process further includes removing the blocking structure 209.

[0088] Accordingly, an embodiment of the present invention also provides a back-illuminated image sensor, please refer to [link / reference needed]. Figure 13The system includes: a first substrate 200, which includes a pixel region I containing a first ion, and the first substrate 200 having a first surface 201 and a second surface 202 opposite to each other; a plurality of deep trenches 206 located in the pixel region I, the deep trenches 206 penetrating the first substrate 200 from the first surface 201 to the second surface 202; an intrinsic epitaxial layer 207 located on the sidewall of the deep trenches 206; a doped epitaxial layer 208 located on the surface of the intrinsic epitaxial layer 207, the doped epitaxial layer containing a second ion, the second ion having a different electrical type from the first ion; a filling layer 210 located on the first surface 201, the filling layer 210 closing the opening of the deep trenches 206; and a device layer 212 located on the first surface 201, the device layer 212 having a plurality of device structures.

[0089] In this embodiment, the first substrate 200 further includes a marking region II; the back-illuminated image sensor further includes: a marking opening 204 located in the marking region II, the marking opening 204 extending from the first surface 201 to the second surface 202; and a marking structure 211 located in the marking opening 204.

[0090] In this embodiment, the material of the marking structure 211 is different from the material of the first substrate 200; the material of the marking structure 211 includes silicon oxide.

[0091] In this embodiment, it further includes: a second substrate 300; and a bonding layer 301 located on the surface of the second substrate 300, wherein the bonding layer 301 is opposite to the device layer 212 to bond the first substrate 200 and the second substrate 300.

[0092] In this embodiment, the device structure includes one or more of the following: transistor structure, capacitor structure, resistor structure, inductor structure, and electrical interconnection structure.

[0093] In this embodiment, the thickness of the intrinsic epitaxial layer 207 is 80 nanometers to 120 nanometers.

[0094] In this embodiment, the thickness of the doped epitaxial layer 208 is 40 nanometers to 80 nanometers.

[0095] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for forming a back-illuminated image sensor, characterized in that, include: A first substrate is provided, the first substrate including a pixel region having a first ion therein, the first substrate having a first surface and a second surface opposite to each other; A plurality of deep trenches are formed within the pixel area, and the deep trenches extend from the first surface to the second surface; An intrinsic epitaxial layer is formed on the sidewall of the deep trench; A doped epitaxial layer is formed on the surface of the intrinsic epitaxial layer, and the doped epitaxial layer contains a second ion, the second ion having a different electrical type from the first ion; A filling layer is formed on the first surface, the filling layer only sealing the opening of the deep trench, the inside of the deep trench still being a cavity structure; After the filling layer is formed, a device layer is formed on the first surface, the device layer having a plurality of device structures; wherein, The first ion and the second ion diffuse toward the intrinsic epitaxial layer to form a photodiode within the intrinsic epitaxial layer, and the formed photodiode surrounds the deep trench. The second surface is thinned, and the deep trench is exposed from the second surface to the first surface to increase the amount of light entering and improve the sensitivity of the back-illuminated image sensor.

2. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, The first substrate further includes a marking region; in the process of forming the deep trench, the process further includes: forming a marking opening in the marking region, the marking opening extending from the first surface to the second surface; the marking opening having a first depth dimension, the deep trench having a second depth dimension, the second depth dimension being greater than the first depth dimension.

3. The method for forming a back-illuminated image sensor as described in claim 2, characterized in that, The first depth dimension ranges from 0.5 micrometers to 0.8 micrometers; the second depth dimension ranges from 3 micrometers to 4 micrometers.

4. The method for forming a back-illuminated image sensor as described in claim 2, characterized in that, The method for forming the marker opening and the deep trench includes: forming a first patterned layer on the first surface, the first patterned layer exposing a portion of the first surface; etching the first substrate using the first patterned layer as a mask to form the marker opening in the marker area and a plurality of initial deep trenches in the pixel area; removing the first patterned layer; forming a sacrificial layer on the first surface, the sacrificial layer covering the marker opening; after forming the sacrificial layer, etching the initial deep trenches to form the deep trenches; and after forming the deep trenches, removing the sacrificial layer.

5. The method for forming a back-illuminated image sensor as described in claim 2, characterized in that, After forming the doped epitaxial layer, the method further includes forming a marker structure within the marker opening.

6. The method for forming a back-illuminated image sensor as described in claim 5, characterized in that, The material of the marking structure is different from the material of the first substrate; the material of the marking structure includes silicon oxide.

7. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, The method for forming the filling layer includes: forming a barrier structure in the deep trench, the barrier structure covering the bottom surface and part of the sidewall of the doped epitaxial layer, and the top surface of the barrier structure being lower than the top surface of the doped epitaxial layer; forming an initial filling layer on the exposed sidewall of the doped epitaxial layer and the first surface using a sampling epitaxial growth process; and planarizing the initial filling layer to form the filling layer.

8. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, After forming the device layer, the method further includes: providing a second substrate; forming a bonding layer on the surface of the second substrate; and bonding the bonding layer to the device layer to bond the first substrate and the second substrate.

9. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, The device structure includes one or more of the following: transistor structure, capacitor structure, resistor structure, inductor structure, and electrical interconnection structure.

10. The method for forming a back-illuminated image sensor as described in claim 8, characterized in that, After bonding the first substrate and the second substrate, the method further includes: thinning the second surface and exposing the deep trench from the second surface to the first surface.

11. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, The thickness of the intrinsic epitaxial layer is 80 nanometers to 120 nanometers.

12. The method for forming a back-illuminated image sensor as described in claim 1, characterized in that, The thickness of the doped epitaxial layer is 40 nanometers to 80 nanometers.

13. A back-illuminated image sensor, characterized in that, include: A first substrate, the first substrate including a pixel region having a first ion in the pixel region, the first substrate having a first surface and a second surface opposite to each other; A plurality of deep trenches located within the pixel area, the deep trenches extending from the first surface to the second surface and penetrating the first substrate; The intrinsic epitaxial layer located on the sidewall of the deep trench; A doped epitaxial layer located on the surface of the intrinsic epitaxial layer, wherein the doped epitaxial layer contains a second ion, the second ion having a different electrical type from the first ion; The filling layer located on the first surface only seals the opening of the deep trench, and the inside of the deep trench remains a cavity structure; The device layer is located on the first surface, and the device layer has a plurality of device structures; wherein, The first ion and the second ion diffuse toward the intrinsic epitaxial layer to form a photodiode within the intrinsic epitaxial layer, and the photodiode surrounds the deep trench. The second surface exposes the deep trench to the first surface to increase the amount of light entering and improve the sensitivity of the back-illuminated image sensor.

14. The back-illuminated image sensor as described in claim 13, characterized in that, The first substrate further includes a marking area; the back-illuminated image sensor further includes: a marking opening located within the marking area, the marking opening extending from the first surface to the second surface; and a marking structure located within the marking opening.

15. The back-illuminated image sensor as described in claim 14, characterized in that, The material of the marking structure is different from the material of the first substrate; the material of the marking structure includes silicon oxide.

16. The back-illuminated image sensor as claimed in claim 13, characterized in that, Also includes: Second substrate; A bonding layer located on the surface of the second substrate, the bonding layer being opposite to the device layer to bond the first substrate and the second substrate.

17. The back-illuminated image sensor as described in claim 13, characterized in that, The device structure includes one or more of the following: transistor structure, capacitor structure, resistor structure, inductor structure, and electrical interconnection structure.

18. The back-illuminated image sensor as claimed in claim 13, characterized in that, The thickness of the intrinsic epitaxial layer is 80 nanometers to 120 nanometers.

19. The back-illuminated image sensor as described in claim 13, characterized in that, The thickness of the doped epitaxial layer is 40 nanometers to 80 nanometers.

Images