Photoelectric sensor and its fabrication method
Patent Information
- Application Number
- CN202611046660.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-14
- Publication Date
- 2026-09-22
AI Technical Summary
[0004]然而，现有的体偏置光电二极管MOSFET（PD-MOS）中，光生载流子向源极的迁移效率较低，导致灵敏度较差
本发明的技术方案提供的光电传感器中，通过在光敏掺杂区、浅沟槽隔离结构、掺杂漏区、栅结构和掺杂源区下方的阱区内设置同导电类型的梯度掺杂埋层，并且，自光敏掺杂区向掺杂源区的方向，梯度掺杂埋层的离子掺杂浓度梯度下降，因此，自光敏掺杂区进入阱区的光生载流子会选择进入阻力更小的梯度掺杂埋层，并在其内向浓度梯度下降的方向迁移，也即是说，相当于在阱区内形成建立了用于使光生载流子自光敏掺杂区向源区迁移的迁移通道，从而，减少了光生载流子向各方向的扩散和损失，提高了光生载流子向源极的迁移效率，由此，增加了光电传感器的灵敏度。
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Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a photoelectric sensor and its fabrication method. Background Technology
[0002] Weak light detection is widely used in deep space exploration, medical imaging, and scientific instruments, and its success depends on the performance of the detector.
[0003] In the prior art, a photodiode (PD) is combined with a metal-oxide-semiconductor field-effect transistor (MOSFET). The photosensitive characteristics of the PD are used to absorb photons and generate photogenerated carriers, while the electrical performance of the device is modulated by the bulk bias effect of the MOSFET.
[0004] However, in existing bulk biased photodiode MOSFETs (PD-MOS), the migration efficiency of photogenerated carriers to the source is low, resulting in poor sensitivity. Summary of the Invention
[0005] The technical problem solved by this invention is to provide a photoelectric sensor and its fabrication method to improve the sensitivity of the photoelectric sensor.
[0006] To solve the above-mentioned technical problems, the present invention provides a photoelectric sensor, comprising: a substrate; a well region located within the substrate; a gate structure located on the surface of the well region; a doped source region and a doped drain region located in the well regions on both sides of the gate structure; a photosensitive doped region located in the well region, wherein the gate structure and the photosensitive doped region are located on both sides of the doped drain region, and a shallow trench isolation structure is provided between the photosensitive doped region and the doped drain region; and a gradient-doped buried layer located in the well region below the photosensitive doped region, the shallow trench isolation structure, the doped drain region, the gate structure, and the doped source region, wherein the gradient-doped buried layer has the same conductivity type as the well region, and the ion doping concentration gradient of the gradient-doped buried layer decreases from the photosensitive doped region to the doped source region.
[0007] Optionally, from the photosensitive doped region to the doped source region, the gradient doped buried layer includes multiple regions with the same implanted ions but different ion doping concentrations.
[0008] Optionally, at least the ion doping concentration of the gradient-doped buried layer in the local area below the photosensitive doped region is higher than the ion doping concentration of the well region.
[0009] Optionally, the well region may also have a deep trench isolation structure.
[0010] Optionally, the conductivity type of the well region and the gradient doped buried layer is P-type, and the conductivity type of the doped source region, the doped drain region and the photosensitive doped region is N-type.
[0011] Optionally, it further includes: an oxide layer at least located on the surface of the well region; the gate structure includes a gate oxide layer and a gate located on the surface of the gate oxide layer, wherein the portion of the oxide layer located below the gate serves as the gate oxide layer.
[0012] Accordingly, the present invention also provides a method for fabricating a photoelectric sensor, comprising: providing a substrate; forming a deep trench isolation structure and a shallow trench isolation structure within the substrate; forming a well region within the substrate after forming the deep trench isolation structure and the shallow trench isolation structure; forming a gradient-doped buried layer with the same conductivity type as the well region within the well region; forming a gate structure on the surface of the well region after forming the gradient-doped buried layer; forming a doped source region, a doped drain region, and a photosensitive doped region within the well region after forming the gate structure, wherein the doped source region and the doped drain region are respectively located on both sides of the gate structure, the gate structure and the photosensitive doped region are respectively located on both sides of the doped drain region, the shallow trench isolation structure is located between the photosensitive doped region and the doped drain region, the gradient-doped buried layer is located below the photosensitive doped region, the shallow trench isolation structure, the doped drain region, the gate structure, and the doped source region, and the ion doping concentration gradient of the gradient-doped buried layer decreases from the photosensitive doped region to the doped source region.
[0013] Optionally, the gradient-doped buried layer is formed by ion implantation, wherein the implantation dose gradient of the ion implantation for forming the gradient-doped buried layer decreases, and the implantation dose range of the ion implantation for forming the gradient-doped buried layer is 5 × 10⁻⁶. 13 ions / cm 2 ~1×10 15 ions / cm 2 .
[0014] Optionally, the gradient-doped buried layer includes multiple regions implanted with the same type of ions but with different ion doping concentrations. The ion implantation forming the gradient-doped buried layer includes multiple different ion implantation doses to correspond to multiple different regions of the gradient-doped buried layer. Furthermore, the ion implantation dose decreases sequentially in the multiple different regions of the gradient-doped buried layer from the photosensitive doped region toward the doping source region.
[0015] Optionally, the ion implantation energy is 1500 keV, and the plurality of different ion implantation doses include 5 × 10⁻⁶ keV. 14 ions / cm 2 3×10 14 ions / cm2 and 1×10 14 ions / cm 2 .
[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: In the photoelectric sensor provided by the technical solution of the present invention, a gradient-doped buried layer of the same conductivity type is provided in the photosensitive doped region, the shallow trench isolation structure, the doped drain region, the gate structure, and the well region below the doped source region. Furthermore, the ion doping concentration gradient of the gradient-doped buried layer decreases from the photosensitive doped region to the doped source region. Therefore, photogenerated carriers entering the well region from the photosensitive doped region will selectively enter the gradient-doped buried layer with less resistance and migrate in the direction of decreasing concentration gradient within it. In other words, it is equivalent to forming a migration channel in the well region for photogenerated carriers to migrate from the photosensitive doped region to the source region. This reduces the diffusion and loss of photogenerated carriers in all directions, improves the migration efficiency of photogenerated carriers to the source, and thus increases the sensitivity of the photoelectric sensor. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the cross-sectional structure of a photoelectric sensor; Figures 2 to 9 This is a cross-sectional structural schematic diagram of each step in the fabrication method of the photoelectric sensor according to an embodiment of the present invention; Figure 10 This is a schematic diagram of the migration of photogenerated carriers in the photoelectric sensor according to an embodiment of the present invention.
[0018] Explanation of reference numerals in the attached figures: 100. Substrate; 110. Shallow trench isolation opening; 111. Shallow trench isolation structure; 120. Deep trench isolation opening; 121. Deep trench isolation structure; 130. Well region; 140. Gradient-doped buried layer; 150. Photosensitive doped region; 160. Doped drain region; 170. Doped source region; 180. Gate structure; 181. Oxide layer; 1811. Gate oxide layer; 182. Gate electrode; 210. First mask structure; 211. Opening; 220. Silicon dioxide film. Detailed Implementation
[0019] As described in the background section, in existing bulk-biased photodiode MOSFETs (PD-MOS), the migration efficiency of photogenerated carriers to the source is low, resulting in poor sensitivity. The following section combines... Figure 1 Please provide a detailed explanation.
[0020] Figure 1 This is a schematic diagram of the cross-sectional structure of a photoelectric sensor.
[0021] Please refer to Figure 1 The photoelectric sensor includes: a substrate 31, a photosensitive doped region 32, a PD cathode 321, a doped source region 33, a doped drain region 34, a gate insulating layer 35, an isolation region 36, a deep trench isolation region 37, a passivation layer 43, a source electrode S, a gate electrode G, and a drain electrode D.
[0022] In this process, light L is incident from the photosensitive doped region 32, and photogenerated carriers migrate from the photosensitive doped region 32 toward the doped source region 33.
[0023] However, during this migration, photogenerated carriers diffuse in various directions, such as towards the substrate 31, or in other directions that are not towards the doped source region 33. As a result, the migration efficiency of photogenerated carriers to the source is low, leading to poor sensitivity.
[0024] To address the aforementioned technical problems, the present invention provides a photoelectric sensor and its fabrication method. By setting up well regions of the same conductivity type within the photosensitive doped region, shallow trench isolation structure, doped drain region, gate structure, and well region below the doped source region, and by decreasing the ion doping concentration gradient of the gradient-doped buried layer from the photosensitive doped region towards the doped source region, a dedicated migration channel for photogenerated carriers is formed within the well region. This improves the mobility of photogenerated carriers, thereby enhancing the sensitivity of the photoelectric sensor.
[0025] To make the above-mentioned objectives, features, and beneficial effects of the present invention more apparent and understandable, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0026] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus. Additionally, directional terms such as above, below, up, down, upward, downward, left, right, etc., are used relative to exemplary embodiments as they are shown in the figures, with upward or upper directions pointing towards the top of the corresponding figure and downward or lower directions pointing towards the bottom of the corresponding figure.
[0027] Figures 2 to 9 This is a cross-sectional structural schematic diagram of each step in the fabrication method of the photoelectric sensor according to an embodiment of the present invention.
[0028] Please refer to Figure 2 Provides a base of 100.
[0029] In this embodiment, the substrate 100 may be a silicon substrate.
[0030] In this embodiment, the surface of the substrate 100 has a silicon dioxide film 220.
[0031] Next, a shallow trench isolation structure 111 is formed within the substrate 100.
[0032] Please refer to the specific steps for forming the shallow trench isolation structure. Figure 3 and Figure 4 .
[0033] Please refer to Figure 3 A patterned first mask structure 210 is formed on the surface of the substrate 100, the first mask structure 210 having a plurality of openings 211 that expose the substrate 100.
[0034] Specifically, the first mask structure 210 is a composite layer structure.
[0035] Furthermore, the composite layer structure may include a Si3N4 layer and a SiON layer located on the surface of the Si3N4 layer.
[0036] In this embodiment, the method for forming a patterned first mask structure 210 on the surface of the substrate 100 includes: forming a first mask material layer (not shown) on the surface of a silicon dioxide film; and etching the first mask material layer by photolithography until the surface of the substrate 100 is exposed to form a patterned first mask structure 210.
[0037] Please continue to refer to this. Figure 3 Using the first mask structure 210 as a mask, the substrate 100 is etched to form shallow trench isolation openings 110 and deep trench isolation openings 120 within the substrate 100, thereby defining shallow trench isolation structures 111 and deep trench isolation structures 121 accordingly.
[0038] Specifically, the substrate 100 can be etched using either a dry etching process or a wet etching process.
[0039] Please refer to Figure 4 A shallow trench isolation structure 111 is formed within the shallow trench isolation opening 110, and a deep trench isolation structure 121 is formed within the deep trench isolation opening 120.
[0040] Specifically, an isolation structure material layer is deposited in the shallow trench isolation opening 110, the deep trench isolation opening 120, and on the surface of the first mask structure 210. Then, the isolation structure material layer is planarized by chemical mechanical polishing until the surface of the first mask structure 210 is exposed.
[0041] Furthermore, the materials for the shallow trench isolation structure 111 and the deep trench isolation structure 121 can be silicon dioxide.
[0042] Please refer to Figure 5 In this embodiment, after the shallow trench isolation structure 111 is formed, the first mask structure 210 is removed.
[0043] Please refer to Figure 6 After forming the shallow trench isolation structure 111, a trap region 130 is formed within the substrate 100.
[0044] Specifically, the well region 130 can be formed using an ion implantation process.
[0045] Specifically, the implantation dose range for the ion implantation process forming the well region 130 can be 10. 12 ions / cm 2 ~10 13 ions / cm 2 .
[0046] The conductivity type of the well region 130 can be P-type.
[0047] Furthermore, the ions doped in well region 130 may include boron (B).
[0048] In some other embodiments, the ions doped in the well region 130 may also include at least one of aluminum (Al), gallium (Ga), and indium (In).
[0049] In this embodiment, after the shallow trench isolation structure 111 is formed and before the well region 130 is formed, an oxide layer 181 is formed on the surface of the substrate 100.
[0050] Please refer to Figure 7 A gradient-doped buried layer 140 is formed within the well region 130.
[0051] The gradient doped buried layer 140 is located below the shallow trench isolation structure 111, the photosensitive doped region 150 (to be formed later), the doped drain region 160 (to be formed later), the gate structure 180 (to be formed later), and the doped source region 170 (to be formed later).
[0052] The gradient-doped buried layer 140 has the same conductivity type as the well region 130.
[0053] Specifically, the conductivity type of the gradient-doped buried layer 140 can be P-type.
[0054] From the photosensitive doped region 150 to the doped source region 170, the ion doping concentration gradient of the gradient doped buried layer 140 decreases.
[0055] Specifically, an ion implantation method can be used to form a gradient-doped buried layer 140. Furthermore, the implantation dose gradient of the ion implantation method for forming the gradient-doped buried layer 140 decreases, thereby reducing the ion doping concentration gradient of the gradient-doped buried layer 140.
[0056] Specifically, the ion doping concentration of the locally gradient-doped buried layer 140 under the photosensitive doped region 150 is higher than that of the well region 130, so as to achieve the formation of migration channels.
[0057] Specifically, the ion implantation dose range for forming the gradient-doped buried layer 140 can be 5 × 10⁻⁶. 13 ions / cm 2 ~1×10 15 ions / cm 2 .
[0058] Furthermore, the gradient-doped buried layer 140 includes multiple regions implanted with the same type of ions but with different ion doping concentrations. The ion implantation forming the gradient-doped buried layer 140 includes multiple different ion implantation doses to correspond to multiple different regions of the gradient-doped buried layer 140. Moreover, from the photosensitive doped region 150 to the doped source region 170, the ion implantation dose in the multiple different regions of the gradient-doped buried layer decreases sequentially.
[0059] Preferably, the ion implantation energy can be 1500 keV, and multiple different ion implantation doses include 5 × 10⁻⁶ keV. 14 ions / cm 2 3×10 14 ions / cm 2 and 1×10 14 ions / cm 2 .
[0060] Please refer to Figure 8 After forming a gradient-doped buried layer 140, a gate structure 180 is formed on the surface of the well region 130.
[0061] Specifically, the gate structure 180 includes a gate oxide layer 1811 and a gate 182 located on the surface of the gate oxide layer 1811, wherein the portion of the oxide layer 181 located below the gate 182 serves as the gate oxide layer 1811.
[0062] Furthermore, the method for forming the gate structure 180 includes: depositing a gate material layer (not shown) on the surface of the oxide layer 181; forming a patterned gate mask layer (not shown) on the surface of the gate material layer; and etching the gate material layer until the oxide layer 181 is exposed using the gate mask layer as a mask to form the gate 182.
[0063] Specifically, the material of the gate 182 can be polycrystalline silicon.
[0064] Please refer to Figure 9 After the gate structure 180 is formed, a doped source region 170, a doped drain region 160, and a photosensitive doped region 150 are formed in the well region 130.
[0065] The doped source region 170 and the doped drain region 160 are located on both sides of the gate structure 180, the gate structure 180 and the photosensitive doped region 150 are located on both sides of the doped drain region 160, and the shallow trench isolation structure 111 is located between the photosensitive doped region 150 and the doped drain region 160.
[0066] In this embodiment, the conductivity type of the doped source region 170, the doped drain region 160, and the photosensitive doped region 150 can all be N-type.
[0067] Accordingly, this invention also provides a photoelectric sensor formed using the above-described preparation method. Please refer to [link / reference needed]. Figure 9 The photoelectric sensor includes: a substrate 100, a well region 130, a gate structure 180, a doped source region 170, a doped drain region 160, a photosensitive doped region 150, and a gradient doped buried layer 140.
[0068] The well region 130 is located within the substrate 100.
[0069] The gate structure 180 is located on the surface of the well region 130.
[0070] The doped source region 170 and the doped drain region 160 are located in the well regions 130 on both sides of the gate structure 180.
[0071] The photosensitive doped region 150 is located within the well region 130.
[0072] The gate structure 180 and the photosensitive doped region 150 are located on both sides of the doped drain region 160, and a shallow trench isolation structure 111 is provided between the photosensitive doped region 150 and the doped drain region 160.
[0073] The gradient-doped buried layer 140 is located in the well region 130 below the photosensitive doped region 150, the shallow trench isolation structure 111, the doped drain region 160, the gate structure 180, and the doped source region 170. The gradient-doped buried layer 140 has the same conductivity type as the well region 130, and the ion doping concentration gradient of the gradient-doped buried layer 140 decreases from the photosensitive doped region 150 to the doped source region 170.
[0074] In this embodiment of the invention, a gradient-doped buried layer 140 of the same conductivity type is provided in the well region 130 below the photosensitive doped region 150, the shallow trench isolation structure 111, the doped drain region 160, the gate structure 180, and the doped source region 170. Furthermore, the ion doping concentration gradient of the gradient-doped buried layer 140 decreases from the photosensitive doped region 150 towards the doped source region 170. Therefore, as... Figure 10 As shown, photogenerated carriers entering the well region 130 from the photosensitive doped region 150 will selectively enter the gradient-doped buried layer 140 with less resistance and migrate in the direction of decreasing concentration gradient within it. That is to say, a migration channel for photogenerated carriers to migrate from the photosensitive doped region 150 to the source region is formed in the well region 130, thereby reducing the diffusion and loss of photogenerated carriers in all directions, improving the migration efficiency of photogenerated carriers to the source, and thus increasing the sensitivity of the photoelectric sensor.
[0075] Furthermore, in the direction from the photosensitive doped region to the doped source region, the gradient doped buried layer 140 includes multiple regions with the same implanted ions but different ion doping concentrations.
[0076] Specifically, the ion doping concentration of the locally gradient-doped buried layer 140 under the photosensitive doped region 150 is higher than that of the well region 130, so as to achieve the formation of migration channels.
[0077] Specifically, the conductivity type of the well region 130 and the gradient doped buried layer 140 can both be P-type, while the conductivity type of the doped source region 170, the doped drain region 160 and the photosensitive doped region 160 can all be N-type.
[0078] Specifically, the gate structure 180 includes a gate oxide layer 1811 and a gate 182 located on the surface of the gate oxide layer 1811, wherein the portion of the oxide layer 181 located on the surface of the well region 130 below the gate 182 is used as the gate oxide layer 1811.
[0079] Furthermore, the well area 130 is also surrounded by a deep trench isolation structure 121.
[0080] The materials, forming process, working principle, specific implementation method and beneficial effects of the photoelectric sensor in the embodiments of the present invention can be found in the preparation method of the photoelectric sensor in the embodiments of the present invention, and will not be repeated here.
[0081] 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 photoelectric sensor, characterized in that, include: Base; The well region is located within the substrate; A gate structure is located on the surface of the well region; The doped source region and the doped drain region are located in the well regions on both sides of the gate structure, respectively; A photosensitive doped region is located within the well region. The gate structure and the photosensitive doped region are located on opposite sides of the doped drain region, and a shallow trench isolation structure exists between the photosensitive doped region and the doped drain region. A gradient-doped buried layer is located in a well region below the photosensitive doped region, the shallow trench isolation structure, the doped drain region, the gate structure, and the doped source region. The gradient-doped buried layer has the same conductivity type as the well region, and the ion doping concentration gradient of the gradient-doped buried layer decreases from the photosensitive doped region to the doped source region.
2. The photoelectric sensor according to claim 1, characterized in that, From the photosensitive doped region toward the doped source region, the gradient doped buried layer includes multiple regions implanted with the same type of ions but with different ion doping concentrations.
3. The photoelectric sensor according to claim 1, characterized in that, At least locally beneath the photosensitive doped region, the ion doping concentration of the gradient-doped buried layer is higher than that of the well region.
4. The photoelectric sensor according to claim 1, characterized in that, The well area is also surrounded by a deep trench isolation structure.
5. The photoelectric sensor according to claim 1, characterized in that, The conductivity type of the well region and the gradient doped buried layer is P-type, while the conductivity type of the doped source region, the doped drain region, and the photosensitive doped region is N-type.
6. The photoelectric sensor according to claim 1, characterized in that, Also includes: An oxide layer at least located on the surface of the well region; the gate structure includes a gate oxide layer and a gate located on the surface of the gate oxide layer, wherein the portion of the oxide layer located below the gate serves as the gate oxide layer.
7. A method for fabricating a photoelectric sensor, characterized in that, include: Provide a base; Deep trench isolation structures and shallow trench isolation structures are formed within the substrate; After forming the deep trench isolation structure and the shallow trench isolation structure, a well region is formed in the substrate; A gradient-doped buried layer with the same conductivity type as the well region is formed within the well region; After the gradient-doped buried layer is formed, a gate structure is formed on the surface of the well region; After the gate structure is formed, a doped source region, a doped drain region, and a photosensitive doped region are formed within the well region. The doped source region and the doped drain region are located on opposite sides of the gate structure, and the gate structure and the photosensitive doped region are located on opposite sides of the doped drain region. The shallow trench isolation structure is located between the photosensitive doped region and the doped drain region. The gradient doped buried layer is located below the photosensitive doped region, the shallow trench isolation structure, the doped drain region, the gate structure, and the doped source region. Furthermore, the ion doping concentration gradient of the gradient doped buried layer decreases from the photosensitive doped region towards the doped source region.
8. The method for fabricating a photoelectric sensor according to claim 7, characterized in that, The gradient-doped buried layer is formed by ion implantation, with the implantation dose gradient decreasing as the ion implantation occurs. The implantation dose range for forming the gradient-doped buried layer is 5 × 10⁻⁶. 13 ions / cm 2 ~1×10 15 ions / cm 2 .
9. The method for fabricating a photoelectric sensor according to claim 8, characterized in that, The gradient-doped buried layer includes multiple regions implanted with the same type of ions but with different ion doping concentrations. The ion implantation forming the gradient-doped buried layer includes multiple different ion implantation doses to correspond to the multiple different regions of the gradient-doped buried layer. Furthermore, the ion implantation dose decreases sequentially in the multiple different regions of the gradient-doped buried layer from the photosensitive doped region toward the doped source region.
10. The method for fabricating a photoelectric sensor according to claim 9, characterized in that, The ion implantation energy is 1500 keV, and the multiple different ion implantation doses include 5 × 10⁻⁶ keV. 14 ions / cm 2 3×10 14 ions / cm 2 and 1×10 14 ions / cm 2 .