Buried channel back-illuminated radiation hardened pixel structure and method of fabrication

Abstract

The application discloses a kind of buried channel back-illuminated radiation-hardened pixel reinforcement structures and preparation methods, including epitaxial layer;Epitaxial layer is etched to form STI groove, and well implantation is formed in epitaxial layer to form STI well implantation area and transmission pipe well implantation area, and STI groove is arranged in STI well implantation area;Epitaxial layer is sequentially formed by ion implantation to form P buried layer injection area, N buried channel injection area and transmission pipe threshold adjustment injection area respectively;P buried layer injection area is connected with transmission pipe well implantation area;The lower surface of epitaxial layer is deposited with gate oxide layer and polysilicon gate;Epitaxial layer is formed by self-aligned implantation process to form N-type PD injection area, N-type FD injection area and P-type clamping layer injection area;The lower surface of FD injection area is deposited with FD ohmic contact metal to form ohmic contact;The lower surface of epitaxial layer is deposited with passivation layer outside.Effectively separate actual photoelectron transmission channel and gate oxide layer / semiconductor interface, and improve the anti-radiation capability of pixel.

Description

Technical Field

[0001] This invention belongs to the field of image sensor technology, specifically to a buried trench back-illuminated radiation-resistant pixel reinforcement structure and its preparation method. Background Technology

[0002] CMOS Image Sensors (CIS) have developed rapidly in recent years thanks to the widespread adoption and innovation of CMOS technology in Very Large Scale Integration (VLSI) manufacturing. By integrating photoelectric sensing modules and image signal processing modules onto a single chip, they have significantly reduced development costs and shortened research and development cycles. Pixels play a crucial role in the entire sensor system, responsible for converting optical image signals into electrical signals. They are the true units that realize "sensing" and are the core components of image sensors. Therefore, in-depth and thorough research based on pixel units is of paramount importance and value for the development of image sensors.

[0003] With the urgent need for human exploration of the unknown realms of space, image sensors (CIS) are also being applied in the aerospace technology field. Artificial satellites are the core of aerospace technology, and image sensors are the "eyes" of these satellites, playing a crucial role in deep space exploration and surface environment monitoring. However, the space environment is far more complex than the ground environment, filled with various types of radiation. Space radiation can easily damage the performance of semiconductor devices, causing varying degrees of malfunction in microelectronic systems and rendering them unable to function properly. For the delicate microelectronic system of CIS, radiation will damage its pixel devices, leading to a significant decrease in image quality. Therefore, the exploration of radiation-resistant pixel hardening designs for CIS has significant practical implications.

[0004] When a pixel is exposed to radiation, the incident particle interacts with atoms in the material, transferring some energy to its outer electrons. When the energy gained by the electron exceeds the binding energy, it can break free from the atomic nucleus to form a free electron, creating a positive ion (hole) at its original location, ultimately altering the electrical properties of the material. In silicon dioxide, only a small number of electron-hole pairs recombine; the majority are separated by the electric field applied to the oxide layer. Due to the high electron mobility—the time for electrons to drift out of silicon dioxide at room temperature is only on the order of picoseconds—while the escape time for holes can reach the order of seconds, the main effect of radiation is caused by the trapping of non-equilibrium holes, forming a positive charge in the oxide layer. Holes slowly transition through localized states in silicon dioxide to the silicon / silicon dioxide interface, where they are trapped by interface state defect centers, forming a fixed positive charge in the oxide layer, causing changes in the local band structure and electrical properties of the semiconductor.

[0005] In PPD pixels, the introduction of the transmission tube adds an additional radiation damage mechanism, not only complicating the radiation damage mechanism of PPD pixels but also severely impacting pixel characteristics. In traditional back-illuminated pixel structures, the transmission tube's gate is located below an epitaxial layer or a well. After the photodiode in the pixel completes the collection of photogenerated electrons after exposure, the transmission tube turns on, and the photoelectrons are transported along the channel at the gate oxide / semiconductor interface to the FD injection region to await signal readout. Under the influence of irradiation, defects generated inside the gate oxide layer and at the gate oxide / semiconductor interface are located adjacent to or on the transport channel of photoelectrons, causing recombination of photoelectrons during transport, severely affecting the pixel's conversion gain and limiting photoelectric conversion efficiency. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention provides a buried trench back-illuminated radiation-resistant pixel reinforcement structure and preparation method to solve the above-mentioned problems.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A buried trench back-illuminated radiation-resistant pixel reinforcement structure includes an epitaxial layer;

[0009] STI trenches are etched on the epitaxial layer, and STI well injection and transport tube well injection regions are formed on the epitaxial layer. The STI trenches are disposed in the STI well injection region.

[0010] The epitaxial layer is sequentially formed by ion implantation into a P-buried layer implantation region, an N-buried layer channel implantation region, and a transport tube threshold adjustment implantation region; the P-buried layer implantation region is connected to the transport tube trap implantation region; the P-buried layer implantation region, the N-buried layer channel implantation region, and the transport tube threshold adjustment implantation region are arranged sequentially from top to bottom.

[0011] The lower surface of the epitaxial layer is deposited with a gate oxide layer and a polysilicon gate, which are arranged from top to bottom.

[0012] The epitaxial layer is formed into an N-type PD injection region, an N-type FD injection region, and a P-type clamping layer injection region through a self-aligned injection process; the N-type PD injection region is located on the side of the transmission tube threshold adjustment injection layer, the clamping layer injection region is located below the PD injection region, and the FD injection region is located within the transmission tube trap injection region.

[0013] An FD ohmic contact metal is deposited on the lower surface of the FD injection region to form an ohmic contact; a passivation layer is deposited on the outer side of the lower surface of the epitaxial layer.

[0014] Preferably, the epitaxial layer is a lightly doped silicon-based P-type epitaxial layer, and the doping concentration of the epitaxial layer is in the range of 1×10⁻⁶. 15 ~5×1015 cm -3 The thickness of the epitaxial layer ranges from 2 to 8 μm.

[0015] Preferably, the STI trap implantation region and the transport tube trap implantation region are formed by multiple boron ion implantations.

[0016] Preferably, the P-buried layer implantation region is formed by boron ion implantation, with an implantation energy range of 60–80 keV and an implantation dose range of 1 × 10⁻⁶. 12 ~2×10 12 cm -2 .

[0017] Preferably, the N-buried trench injection zone is formed by phosphorus injection, with an injection energy range of 15–20 keV and an injection dose range of 8 × 10⁻⁶. 11 ~1×10 12 cm -2 .

[0018] Preferably, the transmission tube threshold adjustment implantation layer is formed by boron ion implantation, with an implantation energy range of 5–7 keV and an implantation dose range of 1 × 10⁻⁶. 12 ~3×10 12 cm -2 .

[0019] Preferably, the dopant in the PD implantation region is arsenic, the implantation energy range is 60–70 keV, and the implantation dose range is 4 × 10⁻⁶. 12 ~6×10 12 cm -2 .

[0020] Preferably, the dopant in the FD implantation region is phosphorus, the implantation energy range is 18–22 keV, and the implantation dose range is 2 × 10⁻⁶. 12 ~3×10 12 cm -2 .

[0021] Preferably, the dopant in the clamping layer implantation region is boron ions, the implantation energy range is 5–7 keV, and the implantation dose range is 8 × 10⁻⁶. 12 ~1×10 13 cm -2 .

[0022] A method for fabricating a buried trench back-illuminated radiation-resistant pixel reinforcement structure includes the following steps:

[0023] Step 1: Perform STI process on the epitaxial layer to etch and form STI trenches and fill them with silicon dioxide;

[0024] Step 2: Perform well injection on the epitaxial layer to simultaneously form an STI well injection region and a transport tube well injection region, with the STI groove located within the STI well injection region.

[0025] Step 3: A P-buried layer implantation region is formed by ion implantation, and the P-buried layer implantation region is connected to the transport tube trap implantation region;

[0026] Step 4: An N-buried trench injection region is formed below the P-buried layer injection region by ion implantation;

[0027] Step 5: A transport tube threshold adjustment injection region is formed below the N-buried layer channel injection region by ion implantation.

[0028] Step 6: Deposit a gate oxide layer on the lower surface of the epitaxial layer;

[0029] Step 7: Deposit a polysilicon gate on the lower surface of the gate oxide layer and pattern the polysilicon gate.

[0030] Step 8: A PD implantation region is formed on the lower surface of the epitaxial layer by self-aligned ion implantation;

[0031] Step 9: Self-aligned ion implantation is used to form an FD implantation region within the transport tube trap implantation region;

[0032] Step 10: A clamping layer implantation region is formed on the lower surface of the PD implantation region by self-aligned ion implantation;

[0033] Step 11: Deposit FD ohmic contact metal on the lower surface of the FD injection region to form an ohmic contact;

[0034] Step 12: Deposit a passivation layer on the lower surface of the epitaxial layer to complete the buried trench back-illuminated radiation-resistant pixel reinforcement structure.

[0035] Compared with the prior art, the present invention has the following beneficial technical effects:

[0036] This invention provides a buried-channel back-illuminated radiation-resistant pixel hardening structure. By introducing an N-type buried channel above the threshold adjustment injection region of the transmission tube, photoelectrons are transported from the photodiode (PD) to the diode (FD) via this N-type buried channel located at a certain distance above the gate oxide / semiconductor interface of the transmission tube. The threshold adjustment injection region of the P-type transmission tube forms an electron barrier between the N-type buried channel and the gate oxide, hindering the movement of photoelectrons transported in the N-type buried channel towards the gate oxide / semiconductor interface. This achieves separation between the actual photoelectron transport channel and the gate oxide / semiconductor interface, suppressing the recombination effects of radiation within the gate oxide and defects introduced at the gate oxide / semiconductor interface on the photoelectrons flowing through the transmission tube. This effectively hardens the transmission tube and significantly improves the pixel's radiation resistance. However, the introduction of the N-type buried channel creates a distance between the actual channel of the transmission tube and the polysilicon gate, weakening the polysilicon gate's control over the channel and potentially leading to the risk of the N-type buried channel not being completely turned off. To address this issue, the back-illuminated radiation-resistant pixel hardening structure proposed in this invention introduces a P-type buried layer injection region above the N-type buried layer channel. By connecting the P-type buried layer injection region with the transmission tube trap injection region, grounding clamping is achieved. Furthermore, by utilizing the pn junction between the N-type buried layer channel and the P-type buried layer injection region, as well as the pn junction between the N-type buried layer channel and the P-type transmission tube threshold adjustment injection region, the N-type buried layer channel can be effectively turned off when a low level is applied to the polysilicon gate of the transmission tube, thereby reducing the dark current of the pixel.

[0037] In this invention, a three-layer vertical doped structure needs to be formed below the transfer gate: a P-type threshold adjustment injection region, an N-type buried channel, and a P-type buried injection region. First, a high-energy injection is performed to form the uppermost P-type buried injection region. Then, a medium-energy injection is performed to form the middle N-type buried channel. Finally, a low-energy injection is performed to form the P-type threshold adjustment injection region. To achieve effective ground clamping by connecting the P-type buried injection region with the transfer gate injection region, the injection window of the P-type buried injection region needs to overlap with the injection window of the transfer gate injection region, with a lateral overlap size of 2 to 3 times the feature size. The N-type buried channel, as the actual channel, needs to connect the N-type injection region and the FD injection region of the PD when the transfer gate is turned on. Since both the PD and FD injection regions are self-aligned, the injection window design for the N-type buried channel needs to consider the overlap margin with both the N-type and FD injection regions of the PD. The lateral size of the N-type buried channel injection window needs to exceed the polysilicon gate feature size by 2 to 3 times on both sides. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of a back-illuminated radiation-resistant pixel reinforcement structure for buried trenches according to the present invention;

[0039] Figure 2 This is a schematic diagram of the back-illuminated pixel epitaxial layer of the present invention;

[0040] Figure 3 This is a schematic diagram of STI process performed on an epitaxial layer;

[0041] Figure 4 A schematic diagram showing the formation of the STI trap injection region and the transport tube trap injection region;

[0042] Figure 5 Schematic diagram of ion implantation in the P-buried layer implantation region;

[0043] Figure 6 Schematic diagram of ion implantation in the N-buried layer trench injection zone;

[0044] Figure 7 Schematic diagram of the injection area for threshold adjustment of the transmission tube;

[0045] Figure 8 This is a schematic diagram of the deposited gate oxide layer;

[0046] Figure 9 This is a schematic diagram of polysilicon gate molding;

[0047] Figure 10 Schematic diagram of N-type PD injection region formation for self-aligned injection process;

[0048] Figure 11 Schematic diagram of N-type FD injection region formation for self-aligned injection process;

[0049] Figure 12 Schematic diagram of P-type clamping layer injection region formed by self-aligned injection process;

[0050] Figure 13 This is a schematic diagram of the deposited passivation layer;

[0051] In the attached figures: 10 is the epitaxial layer; 11 is the STI trench; 12 is the STI well injection region; 13 is the transfer tube well injection region; 14 is the P buried layer injection region; 15 is the N buried layer channel injection region; 16 is the transfer tube threshold adjustment injection region; 17 is the gate oxide layer; 18 is the gate; 19 is the PD injection region; 20 is the FD injection region; 21 is the clamping layer injection region; 22 is the FD ohmic contact metal; 23 is the passivation layer. Detailed Implementation

[0052] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0053] like Figure 1As shown, the present invention discloses a buried trench back-illuminated radiation-hardened pixel structure. First, a shallow trench is etched and filled with silicon dioxide on a lightly doped epitaxial layer 10 using a surface-to-surface (STI) process. Then, a well implantation process is performed, simultaneously forming an STI well implantation region 12 and a transport tube well implantation region 13. The STI trench 11 is required to be within the STI well implantation region 12. Ion implantation defines a P-type buried layer implantation region 14, an N-type buried trench implantation region 15, and a transport tube threshold adjustment implantation region 16. The N-type buried trench implantation region 15 is required to be below the P-type buried layer implantation region 14 (for back-illuminated structures), and the transport tube threshold adjustment implantation region 16 is required to be below the N-type buried trench implantation region 15 (for back-illuminated structures). Furthermore, the P-type buried layer implantation region 14 and the transport tube well implantation region 13 are required to be connected. A gate oxide layer 17 and a polysilicon gate 18 are deposited, and the gate is patterned. An N-type PD injection region 19, an N-type FD injection region 20, and a P-type clamping layer injection region 21 are formed through a self-aligned implantation process, and then annealed to activate them. The FD injection region 20 is required to be within the transmission well injection region 13. The PD injection region 19 is required to be connected to the N-buried channel injection region 15. The FD injection region 20 is required to be connected to the N-buried channel injection region 15. The P-type clamping layer injection region 21 is required to be connected to the transmission well injection region 13. A contact metal 22 is deposited below the FD injection region 20 (for back-illuminated devices) and annealed to form an effective ohmic contact. Finally, a passivation layer 23 is deposited on the device surface, and interconnection and other processes are completed for back-illuminated process fabrication.

[0054] By introducing an N-type buried channel above the threshold adjustment injection region 16 of the transmission tube (for back-illuminated systems), photoelectrons are transported from the PD to the FD20 via the N-type buried channel 15 located at a certain distance above the gate oxide layer 17 and the semiconductor interface of the transmission tube (for back-illuminated systems). The threshold adjustment injection region 16 of the P-type transmission tube forms an electron potential barrier between the N-type buried channel 15 and the gate oxide layer 17, hindering the movement of photoelectrons transported in the N-type buried channel 15 to the gate oxide / semiconductor interface. This achieves separation of the actual photoelectron transmission channel from the gate oxide / semiconductor interface, suppressing the recombination effect of radiation on the photoelectrons flowing through the transmission tube caused by defects introduced within the gate oxide layer 17 and at the gate oxide / semiconductor interface, effectively reinforcing the transmission tube and significantly improving the radiation resistance of the pixel. Furthermore, the introduction of the N-buried channel 15 creates a certain distance between the actual channel of the transmission transistor and the polysilicon gate 18, which weakens the control capability of the polysilicon gate 18 over the channel, thus posing a risk that the N-buried channel 15 cannot be completely turned off. To address this issue, the back-illuminated radiation-hardened pixel structure proposed in this invention introduces a P-type buried injection region 14 above the N-buried channel 15 (for back-illuminated systems). By connecting the P-type buried injection region 14 to the transmission transistor well injection region 13, grounding clamping is achieved. The pn junction between the N-buried channel 15 and the P-type buried injection region 14, and the pn junction between the N-buried channel 15 and the P-type transmission transistor threshold adjustment injection region 16, effectively turns off the N-buried channel 15 when a low level is applied to the polysilicon gate 18 of the transmission transistor, thereby reducing the pixel's dark current.

[0055] In this invention, a three-layer vertical doped structure needs to be formed below the transmission gate, consisting of a P-type threshold adjustment injection region 16, an N-type buried channel 15, and a P-type buried injection region 14. First, a higher energy injection is performed to form the uppermost (for back-illuminated systems) P-type buried injection region 14. Then, a medium energy injection is performed to form the middle N-type buried channel 15. Finally, a low energy injection is performed to form the P-type threshold adjustment injection region 16. To ensure effective grounding clamping by connecting the P-type buried injection region 14 to the transmission gate injection region 13, the injection window of the P-type buried injection region 14 must overlap with the injection window of the transmission gate injection region 13, with a lateral overlap size of 2 to 3 times the feature size. When the transmission tube is turned on, the N-type buried channel 15, which is the actual channel, needs to connect the N-type injection region 19 of the PD and the FD injection region 20. Since both the injection in the PD region 19 and the injection in the FD injection region 20 are self-aligned injections, the injection window design for the N-type buried channel 15 needs to consider the overlap margin with the N-type injection region 19 and the FD injection region 20 of the PD respectively. The horizontal dimension of the injection window of the N-type buried channel 15 needs to exceed the feature size of the polysilicon gate 18 by 2 to 3 times on both sides.

[0056] It should be noted that this invention is specifically designed for N-type injection PDs and N-channel transmission transistors, but it also applies to P-type injection PDs and P-channel transmission transistors.

[0057] In traditional back-illuminated pixel structures, the area above the gate of the N-channel transport diode (for back-illuminated systems) is an epitaxial layer or a P-type semiconductor formed by well implantation. After the photodiode in the pixel has collected photogenerated electrons through exposure, the transport diode turns on, and the photoelectrons are transported along the channel at the gate oxide / semiconductor interface of the transport diode to the FD implantation region to await signal readout. Under the influence of irradiation, a large number of defects will be generated inside the gate oxide layer and at the gate oxide / semiconductor interface. These defects are close to the transport channel of photoelectrons or are on the transport path, which will cause recombination of photoelectrons during transport, seriously affecting the conversion gain of the pixel and limiting the photoelectric conversion efficiency. The back-illuminated radiation-hardened pixel structure proposed in this invention introduces an N-type buried channel 15 above the threshold adjustment injection region 16 of the transmission tube (for back-illuminated systems). This allows photoelectrons to transfer through the N-type buried channel 15, separating the actual photoelectron transmission channel from the gate oxide / semiconductor interface. This suppresses the recombination effect of radiation on photoelectrons flowing through the transmission tube caused by defects introduced within the gate oxide layer 17 and at the gate oxide / semiconductor interface, thereby improving the pixel's radiation resistance. Furthermore, this invention also introduces a P-type buried channel 14 above the N-type buried channel (for back-illuminated systems), enabling effective turn-off of the N-type buried channel 15 when a low level is applied to the polysilicon gate 18, thus reducing the pixel's dark current.

[0058] Example

[0059] The present invention discloses a method for preparing a buried trench back-illuminated radiation-resistant pixel reinforcement structure, comprising the following steps.

[0060] like Figure 2 As shown, epitaxial layer 10 is a back-illuminated pixel epitaxial layer, which is a lightly doped silicon-based P-type epitaxial layer. Preferably, the doping concentration is 1×10⁻⁶. 15 ~5×10 15 cm -3 The thickness is 2-8 μm.

[0061] like Figure 3 and Figure 4 As shown, the STI well implantation region 12 and the transport tube well implantation region 13 are disposed on the epitaxial layer 10, and the STI trench 11 is disposed within the STI well implantation region 12. Preferably, the conditions for forming the required multiple boron ion implantation are as follows: implantation energy 140-160 keV, implantation dose 1×10⁻⁶. 13 ~2×10 13 cm -2Injection energy 290–310 keV, injection dose 1 × 10⁻⁶ 12 ~3×10 12 cm -2 Injection energy 70–90 keV, injection dose 1 × 10⁻⁶ 12 ~3×10 12 cm -2 .

[0062] like Figure 5 As shown, the P-buried implantation region 14 is disposed on the epitaxial layer 10. Preferably, the implantation conditions are boron ion implantation, with an implantation energy of 60-80 keV and an implantation dose of 1×10⁻⁶. 12 ~2×10 12 cm -2 .

[0063] like Figure 6 As shown, the N-buried layer trench injection region 15 is disposed on the epitaxial layer 10 and below the P-buried layer injection region 14 (for back-illuminated systems). Preferably, the injection conditions are phosphorus injection, with an injection energy of 15–20 keV and an injection dose of 8 × 10⁻⁶. 11 ~1×10 12 cm -2 .

[0064] like Figure 7 As shown, the transmission tube threshold adjustment injection layer 16 is disposed on the epitaxial layer 10 and is located below the N-buried layer trench injection region 15 (for back-illuminated systems). Preferably, the injection conditions are boron ion implantation, with an implantation energy of 5–7 keV and an implantation dose of 1 × 10⁻⁶. 12 ~3×10 12 cm -2 .

[0065] like Figure 8 As shown, the gate oxide layer 17 is disposed on the surface of the epitaxial layer 10 and is located below the transmission tube threshold adjustment injection layer 12 (for back-illuminated type). Preferably, the gate oxide layer can be silicon dioxide with a thickness of 7-10 nm.

[0066] like Figure 9 As shown, the polysilicon gate 18 is disposed below the gate oxide layer 17, and the length and thickness of the polysilicon gate 18 can be flexibly determined according to the specific process node.

[0067] like Figure 10 As shown, the PD implantation region 19 is disposed on the epitaxial layer 10 and is formed by self-aligned ion implantation. It is located to the left of the transmission tube threshold adjustment implantation layer 16. Preferably, the implantation conditions are arsenic implantation, with an implantation energy of 60-70 keV and an implantation dose of 4 × 10⁻⁶. 12 ~6×10 12 cm -2 .

[0068] like Figure 11 As shown, the FD implantation region 20 is disposed on the epitaxial layer 10 and within the transport tube implantation region 13. It is formed by self-aligned ion implantation and is located to the right of the transport tube threshold adjustment implantation layer 16. Preferably, the implantation conditions are phosphorus implantation, with an implantation energy of 18–22 keV and an implantation dose of 2 × 10⁻⁶. 12 ~3×10 12 cm -2 .

[0069] like Figure 12 As shown, the clamping layer implantation region 21 is disposed on the epitaxial layer 10, formed by self-aligned ion implantation, and is located below the PD implantation region 19 (for back-illuminated ion implantation). Preferably, the implantation conditions are boron ion implantation, with an implantation energy of 5-7 keV and an implantation dose of 8 × 10⁻⁶. 12 ~1×10 13 cm -2 The annealing temperature was 1050℃ for 10 seconds.

[0070] like Figure 13 As shown, the FD ohmic contact metal 22 is disposed on the lower surface of the FD injection region 20 (for back-illuminated type). The interface between the FD ohmic contact metal 22 and the FD injection region 20 is an ohmic contact interface. Preferably, the FD ohmic contact metal 22 can be Ni metal with a thickness of 50-100 nm and an annealing temperature of 600 °C for 30 s.

[0071] like Figure 1 As shown, the passivation layer 23 is disposed on the lower surface of the pixel (for back-illuminated type), and the material can be a combination of silicon nitride and silicon oxide, with a thickness of 0.5 to 1 μm.

Claims

1. A back-illuminated radiation-resistant pixel reinforcement structure for buried trenches, characterized in that, Including the epitaxial layer (10); STI trenches (11) are etched on the epitaxial layer (10), and STI well injection regions (12) and transport tube well injection regions (13) are formed on the epitaxial layer (10). The STI trenches (11) are disposed in the STI well injection regions (12). Ion implantation is performed from the lower surface of the epitaxial layer (10) to form a P-buried layer implantation region (14), an N-buried layer channel implantation region (15), and a transport tube threshold adjustment implantation region (16) in sequence; the P-buried layer implantation region (14) is connected to the transport tube trap implantation region (13); The lower surface of the epitaxial layer (10) is deposited with a gate oxide layer (17) and a polysilicon gate (18), which are arranged from top to bottom. The epitaxial layer (10) is formed with an N-type PD injection region (19), an N-type FD injection region (20), and a P-type clamping layer injection region (21) by a self-aligned injection process; the N-type PD injection region (19) is located on the side of the transmission tube threshold adjustment injection region (16), and the clamping layer injection region (21) is located below the PD injection region (19); the FD injection region (20) is located inside the transmission tube trap injection region (13); The lower surface of the FD injection region (20) is deposited with FD ohmic contact metal (22) to form an ohmic contact; a passivation layer (23) is deposited on the outer side of the lower surface of the epitaxial layer (10).

2. The buried trench back-illuminated radiation-resistant pixel reinforcement structure according to claim 1, characterized in that, The epitaxial layer (10) is a lightly doped silicon-based P-type epitaxial layer, and the doping concentration of the epitaxial layer (10) ranges from 1×10⁻⁶. 15 ~5×10 15 cm -3 The thickness of the epitaxial layer (10) ranges from 2 to 8 μm.

3. The buried trench back-illuminated radiation-resistant pixel reinforcement structure according to claim 1, characterized in that, The STI trap injection region (12) and the transport tube trap injection region (13) are formed by multiple boron ion implantations.

4. The buried trench back-illuminated radiation-resistant pixel reinforcement structure according to claim 1, characterized in that, The P-buried layer implantation region (14) is formed by boron ion implantation, with an implantation energy range of 60~80keV and an implantation dose range of 1×10⁻⁶. 12 ~2×10 12 cm -2 .

5. The buried trench back-illuminated radiation-resistant pixel reinforcement structure according to claim 1, characterized in that, The N-buried trench injection zone (15) is formed by phosphorus injection, with an injection energy range of 15~20keV and an injection dose range of 8×10⁻⁶. 11 ~1×10 12 cm -2 .

6. The buried trench back-illuminated radiation-resistant pixel reinforcement structure according to claim 1, characterized in that, The threshold adjustment injection region (16) of the transmission tube is formed by boron ion implantation, with an implantation energy range of 5~7keV and an implantation dose range of 1×10⁻⁶. 12 ~3×10 12 cm -2 .

7. The buried trench back-illuminated radiation-resistant pixel reinforcement structure according to claim 1, characterized in that, The dopant in the PD implantation region (19) is arsenic, the implantation energy range is 60~70keV, and the implantation dose range is 4×10⁻⁶. 12 ~6×10 12 cm -2 .

8. The buried trench back-illuminated radiation-resistant pixel reinforcement structure according to claim 1, characterized in that, The dopant in the FD implantation region (20) is phosphorus, the implantation energy range is 18~22keV, and the implantation dose range is 2×10⁻⁶. 12 ~3×10 12 cm -2 .

9. The buried trench back-illuminated radiation-resistant pixel reinforcement structure according to claim 1, characterized in that, The dopant in the clamping layer implantation region (21) is boron ions, with an implantation energy range of 5~7 keV and an implantation dose range of 8×10⁻⁶. 12 ~1×10 13 cm -2 .

10. A method for preparing a buried trench back-illuminated radiation-resistant pixel reinforcement structure, characterized in that, Includes the following steps, Step 1: Perform STI process on epitaxial layer (10), etch to form STI trench (11) and fill with silicon dioxide; Step 2: STI well injection is performed on the epitaxial layer (10) to form an STI well injection region (12) and a transfer tube well injection region (13). The STI groove (11) is located in the STI well injection region (12). Step 3: A P-buried layer implantation region (14) is formed by ion implantation, and the P-buried layer implantation region (14) is connected to the transport tube trap implantation region (13); Step 4: An N-buried trench injection region (15) is formed below the P-buried layer injection region (14) by ion implantation. Step 5: A transport tube threshold adjustment injection region (16) is formed below the N-buried layer channel injection region (15) by ion implantation. Step 6: Deposit a gate oxide layer (17) on the lower surface of the epitaxial layer (10). Step 7: Deposit a polysilicon gate (18) on the lower surface of the gate oxide layer (17) and pattern the polysilicon gate (18); Step 8: Self-aligned ion implantation is used to form a PD implantation region (19) on the lower surface of the epitaxial layer (10). Step 9: Self-aligned ion implantation is used to form an FD implantation region (20) in the transport tube trap implantation region (13). Step 10: Self-aligned ion implantation is used to form a clamped layer implantation region (21) on the lower surface of the PD implantation region (19). Step 11: Deposit FD ohmic contact metal (22) on the lower surface of the FD injection region (20) to form an ohmic contact; Step 12: Deposit a passivation layer (23) on the lower surface of the epitaxial layer (10) to complete the buried trench back-illuminated radiation-resistant pixel reinforcement structure.

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