An enhanced absorption back-illuminated radiation-hardened PPD pixel structure and implementation method thereof

Abstract

The application discloses a back-illumination anti-radiation PPD pixel structure and a realization method thereof. The well injection area, the transmission pipe threshold adjustment injection layer and the PD injection area are arranged on the epitaxial layer. The transmission pipe threshold adjustment injection layer is provided with a gate oxide layer and a gate electrode on one side. The FD area is located inside the well injection area. The high-k dielectric layer covers the device surface. The passivation layer is deposited on the device surface. Through the deposition of the high-k dielectric layer and the reflective metal layer, the work function difference between the metal and the semiconductor is utilized to induce the holes on the surface of the semiconductor PD injection area. The metal layer and the epitaxial layer are connected to the power supply ground, the potential clamping of the PPD surface induced hole layer is realized, the clamping layer of the photodiode surface formed by the high-dose ion implantation is avoided, the defects introduced by the injection damage on the PPD surface are effectively reduced, the recombination of the photoelectron on the surface in the photodiode is reduced, and the quantum efficiency of the pixel unit is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of image sensors, and relates to an enhanced absorption back-illumination anti-radiation PPD pixel structure and an implementation method thereof. BACKGROUND

[0002] Due to the promotion of complementary metal-oxide-semiconductor (CMOS) process technology in very large scale integration (VLSI) manufacturing, CIS (CMOS Image Sensors, CIS) has developed rapidly in recent years, and photoelectric sensing modules and image signal processing modules are integrated on the same chip, thereby greatly reducing the development cost and shortening the development cycle. Pixel units (referred to as pixels) play an important role in the entire sensor system, are responsible for converting optical image signals into electrical signals, are the units that truly realize "sensing", and are the core of image sensors. Therefore, in-depth and sufficient research based on pixel units has great significance and value for the development of image sensors.

[0003] The PPD (Pinned Photodiode) structure has many advantages. First, the PPD structure has good short-wave light charge collection capability, and improves the blue quantum efficiency, because the introduction of the pinning layer moves the light-sensitive collection area of the photodiode upward. + The introduction of the pinning layer moves the light-sensitive collection area of the photodiode upward, has good short-wave light charge collection capability, and improves the blue quantum efficiency; secondly, the photodiode changes from single-junction depletion to double-junction depletion, increases the collection volume of the light-sensitive area, and improves the sensitivity and dynamic range of the pixel; thirdly, the pinning type structure can pin the light-sensitive node to a fixed potential, thereby increasing the potential difference between the charge storage node and the light-sensitive node, and being beneficial to the complete transfer of the charge to the storage node; finally, the design of the buried light-sensitive collection area weakens the influence of the recombination of photoelectrons at the Si-SiO2 interface defects in the photocharge collection process, and greatly reduces the dark current of the pixel. The PPD pixel is paid great attention by researchers due to its superiority in many aspects of performance and the wide range of potential application fields, and therefore has great research significance and value.

[0004] However, the clamping layer in the traditional PPD pixel structure is formed by ion implantation, so that injection damage defects are introduced on the surface of the photodiode in the process of implantation. Although the presence of the clamping layer can inhibit the recombination of photoelectrons on the surface of the photodiode, the injection damage is distributed in a certain direction from the surface to the body, and the recombination effect of the introduced defects on the photoelectrons is difficult to completely inhibit, thereby limiting the quantum efficiency, sensitivity and anode current characteristics of the PPD pixel. Therefore, it is necessary to explore a PPD pixel design that can reduce the defects on the surface of the photodiode, thereby further improving the efficiency of the image sensor. In addition, CIS has important applications in the field of aerospace technology. Artificial satellites are the core of aerospace technology, and image sensors are the "eyes" of artificial satellites. From deep space exploration to ground environment monitoring, image sensors play an important role. However, the space environment is more complex than the daily living environment, and the space is full of various radiation. The space radiation environment mainly comes from cosmic rays, solar flare radiation, inner and outer Van Allen radiation belts around the earth, solar wind, aurora, solar X-rays and electromagnetic radiation with a wide spectrum range. The main components of the above radiation sources are high-energy protons, high-energy electrons and various rays. Space radiation is extremely easy to damage the performance of semiconductor devices, causing different degrees of failure of microelectronic systems, resulting in their inability to work normally. For the precise microelectronic system of CIS, radiation will cause damage to the pixel device, resulting in a significant decrease in imaging quality. Therefore, it is also necessary to explore a pixel reinforcement structure design that can guarantee the excellent performance of CIS while realizing the anti-radiation characteristics. SUMMARY

[0005] The purpose of the present application is to solve the problem that the clamping layer formed by ion implantation in the prior art introduces injection damage defects on the surface of the photodiode in the process of implantation, and the recombination effect of the damage defects on the photoelectrons is difficult to completely inhibit, thereby limiting the quantum efficiency of the PPD pixel. A back-illuminated anti-radiation PPD pixel structure with enhanced absorption and its implementation method are provided.

[0006] To achieve the above purpose, the following technical solutions are adopted in the present application:

[0007] A back-illuminated anti-radiation PPD pixel structure with enhanced absorption, comprising an epitaxial layer, a well implantation region, a transmission tube threshold adjustment implantation layer, a gate oxide layer, a gate, a PD implantation region, an FD region, a high-k dielectric layer, an FD ohmic contact metal, a reflective metal layer and a passivation layer.

[0008] The well implantation region, the transport pipe threshold adjustment implantation layer and the PD implantation region are arranged on the epitaxial layer, one side of the transport pipe threshold adjustment implantation layer is sequentially provided with a gate oxide layer and a gate electrode, the FD region is located inside the well implantation region, the high-k dielectric layer is arranged on the surface of the epitaxial layer and covers the gate electrode, the PD implantation region and the FD region, the FD ohmic contact metal is in surface contact with the FD region, the reflective metal layer is arranged on the surface of the high-k dielectric layer, and the passivation layer is arranged on the surfaces of the reflective metal layer, the high-k dielectric layer and the FD ohmic contact metal.

[0009] An implementation method of a back-illuminated radiation-resistant PPD pixel structure with enhanced absorption, comprising the following steps:

[0010] Performing shallow trench isolation on an epitaxial layer;

[0011] Implanting ions to form a well implantation region;

[0012] Implanting ions to form a transport pipe threshold adjustment implantation layer;

[0013] Depositing a gate oxide layer and a gate electrode and performing patterning on the gate electrode;

[0014] Forming a PD implantation region and an FD region by self-aligned implantation and performing annealing activation;

[0015] Depositing a high-k dielectric layer to cover the PD implantation region and the surface of the isolation shallow trench;

[0016] Removing the high-k dielectric layer on the surface of the FD region, depositing an ohmic contact metal and performing annealing;

[0017] Depositing a reflective metal layer on the surface of the high-k dielectric layer;

[0018] Depositing a passivation layer on the surface of the device.

[0019] Further improvement of the present application is that:

[0020] The doping concentration of the epitaxial layer is 1×10 15 ~ 5×10 15 cm -3 , and the thickness is 2-5 μm.

[0021] The well implantation region needs several times of boron ion implantation, comprising the following steps:

[0022] First, implant energy is 140-160 keV, and implant dose is 1×10 13 ~ 2×10 13 cm -2 ;

[0023] Then, implant energy is 290-310 keV, and implant dose is 1×10 12 ~ 3×10 12 cm-2 ;

[0024] The final energy injection is 70-90keV, and the injection dose is 1*10 12 -3*10 12 cm -2 .

[0025] The transmission pipe threshold adjustment injection layer is boron ion injection, the injection energy is 5-7keV, and the injection dose is 1*10 12 -3*10 12 cm -2 .

[0026] The material of the gate oxide layer is silicon dioxide, and the thickness is 7-10nm.

[0027] The dopant injected in the PD injection area is arsenic, the injection energy is 60-70keV, and the injection dose is 4*10 12 -6*10 12 cm -2 .

[0028] The dopant injected in the FD area is phosphorus, the injection energy is 18-22keV, and the injection dose is 2*10 12 -3*10 12 cm -2 .

[0029] The thickness of the high-k dielectric layer is 10-15nm, and the high-k dielectric layer is made of one or more of Al2O3, HfO2, TiO2 and Ta2O5.

[0030] The reflective metal layer covers the high-k dielectric layer, the thickness of the reflective metal layer is 200-800nm, and the reflective metal layer is made of one or more of Mg, Sc and Y.

[0031] Compared with the prior art, the present application has the following beneficial effects:

[0032] By depositing the high-k dielectric layer and the reflective metal layer with a small work function, the work function difference between the metal and the semiconductor is utilized to induce holes on the surface of the semiconductor PD injection area, and by connecting the metal layer and the epitaxial layer to the power supply ground together, the potential clamping of the PPD surface induced hole layer is realized, thereby avoiding the formation of the clamping layer on the surface of the photodiode by high-dose ion injection, effectively reducing the defects introduced by injection damage on the surface of the PPD, reducing the recombination of photoelectrons on the surface of the photodiode, and improving the quantum efficiency of the pixel unit.

[0033] Further, in the PPD structure, the thickness of the high-k dielectric layer covering the photodiode and the isolation shallow trench surface is only 10-15 nm, so the amount of charges generated in the oxide layer by the irradiation effect is greatly reduced, and the irradiation effect is well inhibited.

[0034] Further, for incident light with a longer wavelength, the transmission path after entering the back-illuminated pixel is longer, and it is easy to pass through the entire epitaxial layer to reach the metal interconnection layer. The reflective metal layer can cause the incident light with a longer wavelength to be reflected at the reflective metal layer after passing through the entire photodiode, and the reflected incident light enters the photodiode again and can be fully absorbed, greatly improving the quantum efficiency of the back-illuminated pixel. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0036] Figure 1 A schematic diagram of a hole accumulation layer induced by a pixel structure in the present application;

[0037] Figure 2 A schematic diagram of a pixel structure in the present application reflecting incident light to enhance absorption;

[0038] Figures 3-13 A schematic diagram of a pixel structure in the present application reflecting incident light to enhance absorption;

[0039] Wherein: 10-epitaxial layer, 11-well implantation region, 12-transmission tube threshold adjustment implantation layer, 13-gate oxide layer, 14-gate, 15-PD implantation region, 16-FD region, 17-high-k dielectric layer, 18-FD ohmic contact metal, 19-reflective metal layer, 20-passivation layer, 21-induced inversion layer. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, not all. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the application provided in the accompanying drawings is not intended to limit the scope of the application claimed, but merely represents selected embodiments of the application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the application, without making creative efforts, fall within the scope of the application.

[0042] It should be noted that similar reference numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it need not be further defined and explained in subsequent drawings.

[0043] In the description of the embodiments of the application, it should be noted that if the terms "upper", "lower", "horizontal", "inner", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed, and are merely for the convenience of describing the application and simplifying the description, and therefore, cannot be understood as indicating or implying that the device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore, cannot be understood as limiting the application. In addition, the terms "first", "second", and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0044] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0045] In the description of the embodiments of the application, it should also be noted that unless otherwise explicitly specified and limited, if the terms "arrangement", "installation", "connection", "connection" appear, they should be understood in a broad sense, for example, they can be fixedly connected, or detachably connected, or integrally connected; can be mechanically connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium; can be the communication between two elements inside. For those of ordinary skill in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0046] The application will be described in further detail below with reference to the accompanying drawings:

[0047] Reference should be made to Figure 1For the hole accumulation layer induced by the pixel structure in the application, it includes epitaxial layer 10, well implantation area 11, transmission tube threshold adjustment implantation layer 12, gate oxide layer 13, gate 14, PD implantation area 15, FD area 16, high-k dielectric layer 17, FD ohmic contact metal 18, reflective metal layer 19 and passivation layer 20. First, shallow trench isolation is performed on the lightly doped epitaxial layer 10, and the formed isolation shallow trench is not filled temporarily; then ion implantation is performed to form the well implantation area 11 and define the transmission tube area; ion implantation is performed to form the transmission tube threshold adjustment implantation layer 12; then the gate oxide layer 13 and the gate 14 are deposited and the gate is patterned; the PD implantation area 15 and the FD area 16 are formed by self-aligned implantation process respectively, and annealing is performed for activation; the high-k dielectric layer 17 is deposited to cover the device surface, including the PD implantation area 15 and the isolation shallow trench; the thin oxide layer on the surface of the FD area 16 is removed, the ohmic contact metal 18 is deposited and annealing is performed; then the reflective metal layer 19 with a smaller work function is deposited under the high-k dielectric layer 17; and the passivation layer 20 is deposited on the surface of the device. By depositing the high-k dielectric layer 17 and the reflective metal layer 19 on the surface of the PD implantation area 15 and the isolation shallow trench, the work function difference between the metal and the semiconductor is utilized to induce holes on the surface of the semiconductor PD, forming a surface hole accumulation layer similar to the traditional PPD, and by connecting the reflective metal layer 19 and the epitaxial layer 10 to the power supply ground together, the potential clamping of the PPD surface induced hole layer is realized. Compared with the traditional PPD structure, the PPD pixel structure proposed by the application avoids forming the clamping layer on the surface of the photodiode by high-dose ion implantation, thereby reducing the defects introduced by implantation damage on the surface of the PPD, reducing the recombination of photoelectrons on the surface of the photodiode, improving the quantum efficiency of the pixel unit, and utilizing the work function difference between the filled isolation shallow trench metal and the semiconductor to generate induced holes to form a potential barrier between the PD and the isolation shallow trench, avoiding the recombination center introduced by high-energy isolation well implantation, which is beneficial to improve the conversion efficiency. In addition, since the high-k dielectric layer 17 covering the surface of the photodiode and the isolation shallow trench in the PPD structure proposed by the application is very thin, the amount of charges generated by the irradiation effect in the oxide layer is greatly reduced, which also means that the structure has a good inhibitory effect on the irradiation effect, especially on the total dose effect. At the same time, the hole accumulation layer induced on the surface of the photodiode by the gold semi-work function is similar to the clamping layer on the surface of the traditional PPD, which is a potential barrier on the path of photoelectrons moving to the surface in the photodiode, which can effectively reduce the recombination of photoelectrons on the surface, further inhibiting the influence of the irradiation effect on the charges introduced in the surface oxide layer. Generally, in the process of depositing the high-k dielectric layer 17, it is easy to form electron traps therein, which become negative centers after trapping electrons, which also helps to induce a hole accumulation layer on the surface of the PD.

[0048] Referring to Figure 2As shown in Fig. 2, the schematic diagram of the reflection of the incident light by the pixel structure of the present application and the enhancement of the absorption, the reflective metal layer 19 is not only the key to the PPD forming the clamping layer in the anti-radiation pixel, but also the reflective layer for the incident light of the back-illuminated pixel. Especially for the incident light with longer wavelength, the transmission path in the back-illuminated pixel is longer, and the incident light can easily pass through the whole epitaxial layer to reach the metal interconnection layer, so that the collection of the incident light by the photodiode in the epitaxial layer will be limited. The introduction of the reflective metal layer 19 makes the incident light with longer wavelength reflect at the reflective metal layer 19 after passing through the whole photodiode, and then the reflected incident light enters the photodiode again, so that the incident light can be fully absorbed to further improve the quantum efficiency.

[0049] After the shallow trench etching in the shallow trench isolation (STI) process, the epitaxial layer 10 is not directly isolated and filled in the shallow trench, but the transmission tube threshold adjustment implantation 12, the gate preparation (including the patterning of the gate oxide layer 13 and the gate 14), and the PD implantation region 15 and the FD region 16 are first completed, and then the isolation shallow trench is filled when the high-k dielectric layer 17 and the reflective metal layer 19 are deposited on the surface of the PD. The high-k dielectric layer 17 covers the whole device surface by ALD, including the PD implantation region 15, the gate 14, and the isolation shallow trench, and the high-k dielectric layer 17 covering the ohmic contact and the gate contact hole is selectively removed in the subsequent process. The main function of the high-k dielectric layer 17 is to avoid the direct contact between the reflective metal layer 19 and the photodiode surface to form a leakage, and the thin layer design not only ensures the effective generation of holes by the reflective metal layer 19 on the semiconductor surface, but also effectively reduces the number of charges introduced by the radiation effect in the oxide layer. The material of the metal layer 19 deposited below the high-k dielectric layer 17 (for the back-illuminated) needs to be selected as a single element metal or an alloy with a work function at least E g / 2 lower than the work function of the PD surface semiconductor, and needs to cover below the high-k dielectric layer 17 (for the back-illuminated) and fill the isolation shallow trench. In addition, considering the process conditions and design redundancy, the reflective metal layer 19 has an overlapping design on the gate 14, and the overlapping length is required to be 1 / 3-1 / 2 of the length of the gate 14.

[0050] Referring to Figures 3-13 As shown in Fig. 3, the flowchart of the preparation method of the pixel structure of the present application, for the back-illuminated image sensor, the epitaxial layer 10 is a lightly doped silicon-based P-type epitaxial layer with a doping concentration of 1×10 15 ~5×10 15 cm -3 and a thickness of 2-5 μm; the well implantation region 11 is arranged on the epitaxial layer 10, and the boron ion needs to be implanted multiple times, and the implantation conditions are as follows: the implantation energy is 140-160 keV, and the implantation dose is 1×10 13 ~2×10 13 cm-2 ; implantation energy 290-310 keV, implantation dose 1x1013-3x1013cm-2 12 12 -2 ; implantation energy 70-90 keV, implantation dose 1x1013-3x1013cm-2 12 12 -2 ; transmission tube threshold adjustment implantation layer 12 is arranged on the epitaxial layer 10 and partially located in the well implantation area 11, implantation conditions are boron ion implantation, implantation energy 5-7 keV, implantation dose 1x1013-3x1013cm-2 12 12 -2 ; gate oxide layer 13 and gate 14 are sequentially arranged below the transmission tube threshold adjustment implantation layer 12, the gate oxide layer 13 is arranged on the surface of the epitaxial layer 10, the gate oxide layer can be selected as silicon dioxide, and the thickness is 7-10 nm; the gate 14 is arranged below the gate oxide layer 13, the length and thickness of the gate 14 can be flexibly determined according to specific process nodes; the PD implantation area 15 is arranged on the epitaxial layer 10 and formed by self-aligned ion implantation, located on the left side of the transmission tube threshold adjustment implantation layer 12, implantation conditions are arsenic implantation, implantation energy 60-70 keV, implantation dose 4x1013-6x1013cm-2 12 12 -2 ; the FD area 16 is arranged on the epitaxial layer 10 and located in the well implantation area 11, formed by self-aligned ion implantation, located on the right side of the transmission tube threshold adjustment implantation layer 12, implantation conditions are phosphorus implantation, implantation energy 18-22 keV, implantation dose 2x1013-3x1013cm-2 12 12 -2 ​​​​​​​​​​, annealing temperature is 1050 DEG C, 10s; high-k dielectric layer 17 is arranged on the lower surface of the epitaxial layer 10, covering the PD, the isolation shallow trench and the transmission gate, etc., the high-k material is a combination of one or more of Al2O3, HfO2, TiO2 or Ta2O5, etc., the thickness is 10-15nm; the FD ohmic contact metal 18 is arranged on the lower surface of the FD region 16, the direct interface between the FD ohmic contact metal 18 and the FD region 16 is an ohmic contact interface, the FD ohmic contact metal 18 can be selected as Ni metal, the thickness is 50-100nm, the annealing temperature is 600 DEG C, 30s; the reflective metal layer 19 is arranged on the lower surface of the high-k dielectric layer 17, covering the PD and the isolation shallow trench, and overlapping with the gate 14, the material can be one or alloy combination of Mg, Sc and Y with smaller work function, the thickness is 200-800nm, and the overlapping length with the gate 14 is 1 / 3-1 / 2 of the length of the gate 14. The passivation layer 20 is arranged on the lower surface of the reflective metal layer 19, the gate 14 and the FD ohmic contact metal 18, the material can be a combination of silicon nitride and silicon oxide, the thickness is 0.5-1um.

[0051] The present application is introduced for N-type injection PD and N-channel transmission tube, but for P-type injection PD and P-channel transmission tube also belongs to the scope of the present application.

[0052] The above only for the preferred embodiments of the present application, and not for limiting the present application, for those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application, should be included in the protection scope of the present application.

Claims

1. A back-illuminated radiation-resistant PPD pixel structure with enhanced absorption, characterized in that, It includes an epitaxial layer (10), a well injection region (11), a transmission tube threshold adjustment injection layer (12), a gate oxide layer (13), a gate (14), a PD injection region (15), an FD region (16), a high-k dielectric layer (17), an FD ohmic contact metal (18), a reflective metal layer (19), and a passivation layer (20). The well injection region (11), the transmission tube threshold adjustment injection layer (12) and the PD injection region (15) are disposed on the epitaxial layer (10). A gate oxide layer (13) and a gate (14) are disposed sequentially on one side of the transmission tube threshold adjustment injection layer (12). The FD region (16) is located inside the well injection region (11). The high-k dielectric layer (17) is disposed on the surface of the epitaxial layer (10) and covers the gate (14), the PD injection region (15) and the FD region (16). The FD ohmic contact metal (18) is in contact with the surface of the FD region (16). The reflective metal layer (19) is disposed on the surface of the high-k dielectric layer (17). The passivation layer (20) is disposed on the surface of the reflective metal layer (19), the high-k dielectric layer (17) and the FD ohmic contact metal (18). The work function of the material of the reflective metal layer (19) is lower than that of the epitaxial layer (10). The difference in work function induces a hole accumulation layer on the surface of the PD implantation region (15), thereby replacing the clamping layer formed by ion implantation.

2. A method for implementing a back-illuminated radiation-resistant PPD pixel structure with enhanced absorption, characterized in that, Includes the following steps: Shallow trench isolation is performed on the epitaxial layer (10); Ion implantation forms a trap implantation region (11); Ion implantation forms a transport tube threshold adjustment implantation layer (12). A gate oxide layer (13) and a gate (14) are deposited, and the gate (14) is patterned. The PD injection region (15) and FD region (16) are formed by self-aligned injection and then activated by annealing. A high-k dielectric layer (17) is deposited to cover the PD injection region (15) and the surface of the isolation trench; Remove the high-k dielectric layer (17) from the surface of the FD region (16), deposit the ohmic contact metal (18) and anneal it; A reflective metal layer (19) is deposited on the surface of the high-k dielectric layer (17); A passivation layer (20) is deposited on the device surface.

3. The method for implementing a back-illuminated radiation-resistant PPD pixel structure with enhanced absorption as described in claim 2, characterized in that, The doping concentration of the epitaxial layer (10) is 1×10⁻⁶. 15 ~5×10 15 cm -3 The thickness is 2~5μm.

4. The method for implementing a back-illuminated radiation-resistant PPD pixel structure with enhanced absorption as described in claim 2, characterized in that, The trap implantation region (11) requires several boron ion implantations, including the following steps: The initial injection energy is 140~160keV, and the injection dose is 1×10⁻⁶. 13 ~2×10 13 cm -2 ; Then, the energy injected is 290~310 keV, and the injection dose is 1×10⁻⁶. 12 ~3×10 12 cm -2 ; The final injection energy was 70~90 keV, and the injection dose was 1×10⁻⁶. 12 ~3×10 12 cm -2 .

5. The method for implementing a back-illuminated radiation-resistant PPD pixel structure with enhanced absorption as described in claim 2, characterized in that, The threshold adjustment injection layer (12) of the transmission tube is implanted with boron ions at an injection energy of 5-7 keV and an injection dose of 1×10⁻⁶. 12 ~3×10 12 cm -2 .

6. The method for implementing a back-illuminated radiation-resistant PPD pixel structure with enhanced absorption as described in claim 2, characterized in that, The gate oxide layer (13) is made of silicon dioxide and has a thickness of 7~10nm.

7. The method for implementing a back-illuminated radiation-resistant PPD pixel structure with enhanced absorption as described in claim 2, characterized in that, The dopant implanted in the PD implantation region (15) is arsenic, the implantation energy is 60~70keV, and the implantation dose is 4×10⁻⁶. 12 ~6×10 12 cm -2 .

8. The method for implementing a back-illuminated radiation-resistant PPD pixel structure with enhanced absorption as described in claim 2, characterized in that, The dopant implanted in the FD region (16) is phosphorus, the implantation energy is 18~22keV, and the implantation dose is 2×10⁻⁶. 12 ~3×10 12 cm -2 .

9. A method for implementing a back-illuminated radiation-resistant PPD pixel structure with enhanced absorption as described in claim 2, characterized in that, The thickness of the high-k dielectric layer (17) is 10~15nm, and the high-k dielectric layer (17) is made of one or more of Al2O3, HfO2, TiO2 and Ta2O5.

10. The method for implementing a back-illuminated radiation-resistant PPD pixel structure with enhanced absorption as described in claim 2, characterized in that, The reflective metal layer (19) covers the high-k dielectric layer (17), the thickness of the reflective metal layer (19) is 200~800nm, and the reflective metal layer (19) is made of one or more of Mg, Sc and Y.

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