Photoelectric detector and forming method thereof

Abstract

The invention discloses a photoelectric detector and a forming method thereof, and the photoelectric detector comprises a substrate which comprises a plurality of photosensitive regions and isolation regions located between the photosensitive regions; the diode structures are positioned in the photosensitive areas; the deep trench isolation structure is positioned in the isolation region; the protruding part is at least located on the surface of the top of the deep groove isolation structure, the surface of the protruding part protrudes relative to the surface of the substrate, and the center of the protruding part is higher than the edge of the protruding part; the passivation layer is located on the surface of the protruding part, and the refractive index of the material of the passivation layer is larger than that of the material of the protruding part. According to the photoelectric detector and the forming method thereof, the number of photons which can be captured by each pixel unit is increased, so that the photon detection efficiency of a device is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a photoelectric detector and a method for forming the same. Background Art

[0002] Silicon photomultiplier (SiPM) is a new type of photoelectric detection device with the characteristics of high gain, high sensitivity, low bias voltage, insensitivity to magnetic field, and compact structure. Silicon photodiodes detect light signals by absorbing the energy of incident photons and producing the corresponding photoelectric effect. At present, silicon photodiodes are widely used in high energy physics and nuclear medicine (PET), laser detection and measurement, and other fields.

[0003] Silicon photodiodes are composed of multiple single-photon avalanche diodes (SPADs) arranged in different arrays. The pixel units where each SPAD is located work independently of each other, and the final output signal is the superposition of the output signals of multiple pixel units. If the number of photons irradiating each SPAD is greater, the signal amplitude will be greater, the detection efficiency (Photon Detection Efficiency, PDE) of the photons will be higher, the optical sensitivity performance of the device will be better, and the obtained electrical signal will be more comprehensive, so that more detailed ranging and imaging information can be obtained in the end.

[0004] In the prior art, each pixel unit in a silicon photodiode is isolated from each other by a number of deep trench isolation structures to avoid optical crosstalk between different pixel units. However, due to the increase in the working area occupied by the deep trench isolation structure, the effective photosensitive area of ​​the device is reduced, thereby reducing the photon detection efficiency of the device. Summary of the invention

[0005] The technical problem solved by the present invention is to provide a photoelectric detector and a method for forming the same, which increases the number of photons that can be captured by each pixel unit, thereby improving the photon detection efficiency of the device.

[0006] In order to solve the above technical problems, the technical solution of the present invention provides a photodetector, including: a substrate, the substrate including a plurality of photosensitive areas and isolation areas located between the photosensitive areas; a diode structure located in each of the photosensitive areas; a deep trench isolation structure located in the isolation area; a raised portion located at least on the top surface of the deep trench isolation structure, the surface of the raised portion protrudes relative to the surface of the substrate, and the center of the raised portion is higher than the edge of the raised portion; a passivation layer located on the surface of the raised portion, the refractive index of the passivation layer material being greater than the refractive index of the raised portion material.

[0007] Optionally, the raised portion located on the top surface of the deep trench isolation structure has a symmetry plane, the raised portion is axially symmetric about the symmetry plane, the symmetry plane of the raised portion coincides with the symmetry plane of the deep trench isolation structure, and the protruding vertex of the raised portion is located on the symmetry plane.

[0008] Optionally, the cross-sectional shape of the raised portion located on the top surface of the deep trench isolation structure along the first plane direction includes a triangle, one side of the triangle is parallel to the substrate surface, and the first plane direction is perpendicular to the substrate surface and parallel to the arrangement direction of each photosensitive area.

[0009] Optionally, the cross-sectional shape of the raised portion located on the top surface of the deep trench isolation structure along a first plane direction includes a trapezoid, a semicircle or a semi-ellipse, and the first plane direction is perpendicular to the substrate surface and parallel to the arrangement direction of each photosensitive area.

[0010] Optionally, the material of the passivation layer includes silicon nitride; and the material of the protrusion includes silicon oxide.

[0011] Optionally, a top surface of the deep trench isolation structure is flush with a surface of the isolation region.

[0012] Optionally, a top surface of the deep trench isolation structure is higher than a surface of the isolation region, and the deep trench isolation structure includes a first isolation portion located in the isolation region and a second isolation portion located on a surface of the isolation region.

[0013] Optionally, the surface of the deep trench isolation structure also has a composite dielectric layer, and the composite dielectric layer includes: a first dielectric layer located on the top and side wall surface of the second isolation portion, and an intermediate dielectric layer located on the surface of the first dielectric layer, the protrusion is located on the surface of the intermediate dielectric layer, the refractive index of the intermediate dielectric layer material is greater than the refractive index of the first dielectric layer material, and the refractive index of the intermediate dielectric layer material is greater than the refractive index of the protrusion material.

[0014] Optionally, the protrusion is also located on the surface of the intermediate dielectric layer of the side wall of the second isolation portion.

[0015] Optionally, the material of the first dielectric layer includes silicon oxide; the material of the protruding portion includes silicon oxide; and the material of the intermediate dielectric layer includes silicon nitride.

[0016] Correspondingly, the technical solution of the present invention also provides a method for forming a photodetector, comprising: providing a substrate, the substrate comprising a plurality of photosensitive areas and isolation areas located between the photosensitive areas; forming a deep trench isolation structure between adjacent photosensitive areas; forming a diode structure in each photosensitive area; forming a protrusion on at least the top surface of the deep trench isolation structure, the surface of the protrusion protrudes relative to the surface of the substrate, and the center of the protrusion is higher than the edge of the protrusion; forming a passivation layer on the surface of the protrusion, the refractive index of the passivation layer material being greater than the refractive index of the protrusion material.

[0017] Optionally, a top surface of the deep trench isolation structure is higher than a surface of the isolation region, and the deep trench isolation structure includes a first isolation portion located in the isolation region and a second isolation portion located on a surface of the isolation region.

[0018] Optionally, a composite dielectric layer is formed on the surface of the deep trench isolation structure, the composite dielectric layer comprising: a first dielectric layer located on the top and side wall surfaces of the second isolation portion, and an intermediate dielectric layer located on the surface of the first dielectric layer on the top and side wall of the second isolation portion, the protrusion is located on the surface of the intermediate dielectric layer, the refractive index of the intermediate dielectric layer material is greater than the refractive index of the first dielectric layer material, and the refractive index of the intermediate dielectric layer material is greater than the refractive index of the protrusion material.

[0019] Optionally, the method for forming the composite dielectric layer and the protruding portion includes: forming a first dielectric layer on the surface of the substrate, the top surface of the second isolation portion, and the side wall surface of the second isolation portion; forming an intermediate material layer on the surface of the first dielectric layer; forming a second material layer on the surface of the intermediate material layer; etching a portion of the second material layer on the isolation region to form a horizontal portion on the intermediate dielectric layer located on the top surface of the second isolation portion; removing the second material layer and the intermediate material layer on the surface of the photosensitive region to form an intermediate dielectric layer on the surface of the first dielectric layer located on the top surface and side wall surface of the second isolation portion and a vertical portion on the surface of the intermediate dielectric layer located on the side wall of the second isolation portion, wherein the horizontal portion and the vertical portion together constitute a protruding portion.

[0020] Optionally, a top surface of the deep trench isolation structure is flush with a surface of the isolation region.

[0021] Optionally, the method for forming the raised portion includes: forming a second material layer on the surface of the substrate and the top surface of the deep trench isolation structure; etching a portion of the second material layer on the isolation area to form a raised portion located on the top surface of the deep trench isolation structure; and removing the second material layer on the surface of the photosensitive area.

[0022] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0023] In the photodetector provided by the technical solution of the present invention, the top surface of the deep trench isolation structure has a raised portion, and the center of the raised portion is higher than the edge of the raised portion, so that the surface formed by the protruding vertex to the edge of the raised portion is inclined relative to the substrate surface, and because the refractive index of the passivation layer is greater than the refractive index of the raised portion, when light is incident on the top of the deep trench isolation structure, at least part of the photons are totally reflected on the inclined surface of the raised portion, and by utilizing its tilt angle, the photons can be reflected into the photosensitive area and captured by the diode structure. Therefore, the scheme of the present invention utilizes the deep trench isolation structure that originally does not have a photosensitivity function, and by providing a raised portion thereon, the photons incident on the top of the deep trench isolation structure can enter the photosensitive area and participate in photosensitivity, thereby increasing the number of photons that can be captured by each pixel unit, thereby improving the photon detection efficiency of the device.

[0024] Furthermore, since the surface of the deep trench isolation structure also has a composite dielectric layer, the composite dielectric layer includes: a first dielectric layer located at the top and side wall surface of the second isolation part, and an intermediate dielectric layer located on the surface of the first dielectric layer, and the protrusion is located on the surface of the intermediate dielectric layer; the refractive index of the intermediate dielectric layer material is greater than the refractive index of the first dielectric layer material and the protrusion material. Therefore, the composite dielectric layer and the protrusion constitute a waveguide structure. After the photons pass through the passivation layer and the protrusion in turn and enter the intermediate dielectric layer, at least part of the photons can be totally reflected back and forth in the intermediate dielectric layer at the top of the second isolation part until they enter the intermediate dielectric layer on the side wall of the second isolation part, thereby changing the incident angle, so that the photons that meet the incident angle less than the critical value at this time can enter the protrusion from the intermediate dielectric layer, and then enter the photosensitive area to be captured by the diode structure, further improving the photon detection efficiency of the device.

[0025] In the method for forming a photodetector provided by the technical solution of the present invention, a protrusion is formed on the top surface of the deep trench isolation structure, and the center of the protrusion is higher than the edge of the protrusion, so that the surface formed by the protruding vertex to the edge of the protrusion is inclined relative to the substrate surface, and because the refractive index of the passivation layer is greater than the refractive index of the protrusion, when light is incident on the top of the deep trench isolation structure, at least part of the photons are totally reflected on the inclined surface of the protrusion, and by utilizing its inclination angle, the photons can be reflected into the photosensitive area and captured by the diode structure. Therefore, the scheme of the present invention utilizes the deep trench isolation structure that originally does not have a photosensitivity function, and by providing a protrusion thereon, the photons incident on the top of the deep trench isolation structure can enter the photosensitive area and participate in photosensitivity, thereby increasing the number of photons that can be captured by each pixel unit, thereby improving the photon detection efficiency of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figures 1 to 8It is a schematic cross-sectional structure diagram of the formation process of the photodetector according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] As described in the background technology, in the prior art, each pixel unit in a silicon photodiode is isolated from each other by a number of deep trench isolation structures to avoid light crosstalk between different pixel units. However, since the deep trench isolation structure does not participate in light sensing, the working area it occupies increases, resulting in a reduction in the effective light sensing area of ​​the device, thereby reducing the photon detection efficiency of the device.

[0028] In order to solve the above technical problems, the technical solution of the present invention provides a photodetector and a method for forming the same, wherein a protrusion is formed on the top surface of the deep trench isolation structure, the surface of the protrusion protrudes relative to the substrate surface, and the center of the protrusion is higher than the edge of the protrusion, so that the surface formed by the protruding vertex to the edge of the protrusion is inclined relative to the substrate surface, and since the refractive index of the passivation layer is greater than the refractive index of the protrusion, when light is incident on the top of the deep trench isolation structure, at least part of the photons are totally reflected on the inclined surface of the protrusion, and using its inclination angle, the photons can be reflected into the photosensitive area and captured by the diode structure, thereby increasing the number of photons that can be captured by each pixel unit and improving the photon detection efficiency of the device.

[0029] In order to make the above-mentioned objects, features and beneficial effects of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0030] Figures 1 to 8 It is a schematic cross-sectional structure diagram of the formation process of the photodetector according to an embodiment of the present invention.

[0031] Please refer to Figure 1 , providing a substrate 100, wherein the substrate 100 includes a plurality of photosensitive regions I and an isolation region II located between the photosensitive regions I.

[0032] The material of the substrate 100 includes silicon, silicon germanium, silicon carbide, silicon on insulator (SOI), germanium on insulator (GOI), etc. Specifically, in this embodiment, the material of the substrate 100 is silicon.

[0033] In this embodiment, the photosensitive area I provides a platform for the subsequently formed diode structure and becomes a photon absorption area; the isolation area II provides a platform for the subsequently formed deep trench isolation structure, thereby isolating adjacent photosensitive areas I to prevent the occurrence of optical crosstalk.

[0034] Next, a deep trench isolation structure is formed between adjacent photosensitive regions I, and a diode structure is formed in each photosensitive region I. For specific steps, please refer to Figures 2 to 4 .

[0035] Please refer to Figure 2 , forming a first oxide layer 102 on the surface of the substrate 100; etching the isolation region II and the first oxide layer 102 on the isolation region II, forming a deep trench 101 in the isolation region II.

[0036] In this embodiment, the material of the first oxide layer 102 includes silicon oxide.

[0037] The deep trench 101 provides space for a deep trench isolation structure to be formed subsequently.

[0038] Please refer to Figure 3 , forming a second oxide layer 103 on the sidewall and bottom surface of the deep trench 101 ; and forming a deep trench isolation material layer 110 in the deep trench 101 and on the surface of the first oxide layer 102 .

[0039] In this embodiment, the deep trench isolation material layer 110 provides raw materials for a subsequently formed deep trench isolation structure.

[0040] In this embodiment, a top surface of the deep trench isolation material layer 110 is higher than a surface of the first oxide layer 102 .

[0041] In this embodiment, the material of the deep trench isolation material layer 110 includes oxide, polysilicon, and tungsten.

[0042] Please refer to Figure 4 , etching the deep trench isolation material layer 110 on the surface of the photosensitive area I to form a deep trench isolation structure 111 in the deep trench 101, and the top surface of the deep trench isolation structure 111 is higher than the top surface of the first oxide layer 102.

[0043] In this embodiment, the deep trench isolation structure 111 is used to isolate the photosensitive structure in the adjacent photosensitive region I to prevent the occurrence of optical crosstalk. Specifically, the deep trench isolation structure 111 includes a first isolation portion 111a located in the isolation region II and a second isolation portion 111b located on the surface of the isolation region II, and the second isolation portion 111b is located on the surface of the first isolation portion 111a.

[0044] In another embodiment, a top surface of the deep trench isolation structure is flush with a top surface of the first oxide layer.

[0045] In other embodiments, a top surface of the deep trench isolation structure is flush with a surface of the isolation region.

[0046] In this embodiment, after the deep trench isolation structure 111 is formed, a first dielectric layer 120 is formed on the top of the second isolation portion 111 b of the deep trench isolation structure 111 , the sidewall surface, and the surface of the first oxide layer 102 .

[0047] The material of the first dielectric layer 120 includes silicon oxide.

[0048] In other embodiments, the first dielectric layer may also be located only on the sidewalls and the top surface of the second isolation portion.

[0049] In this embodiment, a diode structure 125 is then formed in each photosensitive region I. The diode structure 125 is used to absorb incident photons, thereby generating a photoelectric effect and realizing detection of optical signals.

[0050] In other embodiments, the diode structure may be formed before forming the deep trench isolation structure, or the diode structure may be formed after forming the deep trench isolation structure and before forming the first dielectric layer.

[0051] Please refer to Figure 5 , an intermediate material layer 124 is formed on the surface of the first dielectric layer 120 ; and a second material layer 122 is formed on the surface of the intermediate material layer 124 .

[0052] In this embodiment, the intermediate material layer 124 provides raw materials for the intermediate dielectric layer to be formed subsequently; and the second material layer 122 provides raw materials for the protrusions to be formed subsequently.

[0053] Specifically, in this embodiment, the intermediate material layer 124 is located on the surface of the first dielectric layer 120 on the surface of the second isolation portion 111b, and the intermediate material layer 124 is also located on the surface of the first dielectric layer 120 on the surface of the photosensitive area I; the second material layer 122 is located on the surface of the intermediate material layer 124 on the surface of the second isolation portion 111b, and the second material layer 122 is also located on the surface of the intermediate material layer 124 on the surface of the photosensitive area I.

[0054] Please refer to Figure 6, etching a portion of the second material layer 122 on the isolation region II to form a horizontal portion 123a on the intermediate dielectric layer 121 located on the top surface of the second isolation portion 111b; removing the second material layer 122 and the intermediate material layer 124 on the surface of the photosensitive region I to form an intermediate dielectric layer 121 on the surface of the first dielectric layer 120 located on the top and side walls of the second isolation portion 111b and a vertical portion 123b on the surface of the intermediate dielectric layer 121 located on the side walls of the second isolation portion 111b, wherein the horizontal portion 123a and the vertical portion 123b together constitute a protruding portion 123, the surface of the protruding portion 123 protrudes relative to the surface of the substrate 100, and the center of the protruding portion 123 is higher than the edge of the protruding portion 123.

[0055] In this embodiment, the raised portion 123 (i.e., the horizontal portion 123a) located on the top surface of the deep trench isolation structure 111 has a symmetry plane, the raised portion 123 is axially symmetric about the symmetry plane, the symmetry plane of the raised portion 123 coincides with the symmetry plane of the deep trench isolation structure 111, and the protruding vertex of the raised portion 123 is located on the symmetry plane.

[0056] Specifically, in the present embodiment, the cross-sectional figure of the raised portion 123 (i.e., the horizontal portion 123a) located on the top surface of the deep trench isolation structure 111 along the first plane direction includes a triangle, one side of the triangle is parallel to the surface of the substrate 100, and the first plane direction is perpendicular to the surface of the substrate 100 and parallel to the arrangement direction P of each photosensitive area I.

[0057] In another embodiment, the cross-sectional shape of the raised portion (i.e., horizontal portion) located on the top surface of the deep trench isolation structure along the first plane direction includes a trapezoid, a semicircle, or a semi-ellipse, and the first plane direction is perpendicular to the substrate surface and parallel to the arrangement direction of each photosensitive area.

[0058] In this embodiment, the surface of the protrusion 123 protrudes relative to the surface of the substrate 100, and the center of the protrusion 123 is higher than the edge of the protrusion 123, so that the surface formed by the protruding vertex of the protrusion 123 to the edge of the protrusion 123 is inclined relative to the surface of the substrate 100, and the inclined surface faces the photosensitive area I. Therefore, when light is incident on the top of the deep trench isolation structure 111, the inclined surface can use its inclination angle to reflect photons into the photosensitive area I and be captured by the diode structure 125, thereby increasing the number of photons that can be captured by each pixel unit where the photosensitive area I is located.

[0059] Furthermore, the raised portion 123 located on the top surface of the deep trench isolation structure 111 has a symmetry plane, the raised portion 123 is axially symmetrical about the symmetry plane, and the symmetry plane of the raised portion 123 coincides with the symmetry plane of the deep trench isolation structure 111, so the top of the raised portion 123 has two symmetrical inclined surfaces, which respectively face the two photosensitive regions I on both sides of the isolation region II where the raised portion 123 is located. When light is incident on the top of the deep trench isolation structure 111, the two inclined surfaces can reflect photons into the corresponding photosensitive regions I, so that the photons are captured by the diode structure 125, further increasing the number of photons that can be captured by the pixel unit where each photosensitive region I is located.

[0060] In this embodiment, the first dielectric layer 120 located on the top and side wall surface of the second isolation portion 111b and the intermediate dielectric layer 121 located on the surface of the first dielectric layer 120 located on the top and side wall of the second isolation portion 111b together constitute a composite dielectric layer, and the protrusion 123 is located on the surface of the intermediate dielectric layer 121.

[0061] The refractive index of the intermediate dielectric layer 121 material is greater than the refractive index of the first dielectric layer 120 material, and the refractive index of the intermediate dielectric layer 121 material is greater than the refractive index of the protrusion 123 material. The composite structure composed of the first dielectric layer 120, the intermediate dielectric layer 121 and the protrusion 123 located on the top and sidewall surface of the second isolation portion 111b can reflect or refract more photons incident to the isolation region II to the photosensitive region I, so that they are captured by the diode structure 125, thereby increasing the number of photons that can be captured by the pixel unit where each photosensitive region I is located.

[0062] In this embodiment, the process of etching a portion of the second material layer 122 on the isolation region II to form a horizontal portion 123a on the intermediate dielectric layer 121 located on the top surface of the second isolation portion 111b is an anisotropic dry etching process. Specifically, the anisotropic dry etching process includes an anisotropic reactive ion dry etching (RIE) process. In the etching process, the etching rate of the second material layer 122 in the horizontal direction parallel to the substrate 100 is a first rate, and the etching rate of the second material layer 122 in the vertical direction perpendicular to the substrate 100 is a second rate, and the second rate is greater than the first rate, so that the top surface of the horizontal portion 123a can be made into an inclined surface.

[0063] Wherein, the etching process parameters include: the etching gases used include CF4, CH2F2, CH4, O2, Ar, and the flow rate is 10sccm to 100sccm.

[0064] In the present embodiment, the etching process used for etching part of the second material layer 122 on the isolation region II is an etching process commonly used in the sidewall process of a CMOS gate. Therefore, the process conditions are relatively mature and the cost is relatively low.

[0065] In this embodiment, the angle between the two top sides of the triangular cross-section of the horizontal portion 123a ranges from 0 degrees to 180 degrees; the height from the vertex to the bottom of the triangular cross-section ranges from 1 nanometer to 3 micrometers; the height from the top of the vertical portion 123b to the bottom of the vertical portion 123b ranges from 1 angstrom to 1000 nanometers; the thickness of the intermediate dielectric layer 121 ranges from 1 angstrom to 1000 nanometers; the height from the top of the intermediate dielectric layer 121 to the bottom of the intermediate dielectric layer 121 ranges from 1 angstrom to 1000 nanometers; the thickness of the first dielectric layer 120 ranges from 1 angstrom to 1000 nanometers.

[0066] Please refer to Figure 7 , a first interlayer dielectric layer 130 is formed on the surface of the second oxide layer 103; a passivation layer 131 is formed on the first interlayer dielectric layer 130, and the passivation layer 131 is also located on the top surface of the protrusion 123; the refractive index of the passivation layer 131 material is greater than the refractive index of the protrusion 123 material.

[0067] In this embodiment, the passivation layer 131 is used to protect the photosensitive area I, the deep trench isolation structure 111 and the protrusion 123.

[0068] In this embodiment, after the passivation layer 131 is formed, a second interlayer dielectric layer 132 is formed on the surface of the passivation layer 131 .

[0069] In this embodiment, the refractive index of the passivation layer 131 material is greater than the refractive index of the protrusion 123 material, so that part of the photons are totally reflected on the inclined surface of the protrusion 123, thereby utilizing the inclination angle of the top surface of the protrusion 123 to enable the photons to be reflected into the photosensitive area I.

[0070] In other embodiments, interlayer dielectric layers and passivation layers are alternately formed on the surface of the second oxide layer, wherein at least one passivation layer is also located on the surface of the protrusion, and the refractive index of the passivation layer material located on the surface of the protrusion is greater than the refractive index of the protrusion material.

[0071] In this embodiment, after forming the first interlayer dielectric layer 130 , an electrical connection structure 140 is further formed in the first interlayer dielectric layer 130 , and the electrical connection structure 140 is electrically connected to the diode structure 125 ; the passivation layer 131 surrounds the electrical connection structure 140 .

[0072] Please refer to Figure 8 ,in, Figure 8 yes Figure 7 A partial enlarged view of the A region in the middle. When the photodetector is working, the diode structure 125 in the photosensitive region I is used to capture incident light photons, thereby converting the optical signal into an electrical signal. The deep trench isolation structure 111 in the isolation region II is used to isolate adjacent photosensitive regions I to prevent the occurrence of optical crosstalk.

[0073] In this embodiment, the composite structure consisting of the first dielectric layer 120, the intermediate dielectric layer 121 and the raised portion 123 located on the top and side wall surface of the second isolation portion 111b in the deep trench isolation structure 111 can reflect or refract more photons incident on the isolation region II to the photosensitive region I, thereby being captured by the diode structure 125, thereby increasing the number of photons that can be captured by the pixel units where each photosensitive region I is located.

[0074] Specifically, a protrusion 123 is provided on the top surface of the deep trench isolation structure 111, and a surface formed by a protruding vertex to an edge of a horizontal portion 123a of the protrusion 123 is inclined relative to the surface of the substrate 100, and the inclined surface faces the photosensitive area I. Since the refractive index of the passivation layer 131 material is greater than the refractive index of the protrusion 123 material, when light is incident on the top of the deep trench isolation structure 111 (as shown at X1), some photons that meet the incident angle greater than the critical angle of total reflection can be totally reflected on the inclined surface of the horizontal portion 123a, thereby utilizing the inclination angle of the inclined surface of the horizontal portion 123a to enable the photons to be reflected into the photosensitive area I (as shown at X2) and captured by the diode structure 125.

[0075] In addition, since the top and sidewall surface of the second isolation part 111b of the deep trench isolation structure 111 have the first dielectric layer 120, the intermediate dielectric layer 121 located on the surface of the first dielectric layer 120, and the protrusion 123 located on the surface of the intermediate dielectric layer 121, and the refractive index of the material of the intermediate dielectric layer 121 is greater than the refractive index of the material of the first dielectric layer 120 and the material of the protrusion 123, the first dielectric layer 120, the intermediate dielectric layer 121 and the protrusion 123 on the second isolation part 111b constitute a waveguide structure, when the photons sequentially pass through the passivation layer 131, the protrusion 123 and enter the intermediate dielectric layer 121, After the dielectric layer 121 (as shown at Y1), some photons whose incident angle is greater than the critical angle of total reflection can be totally reflected back and forth in the intermediate dielectric layer 121 located at the top of the deep trench isolation structure 111 (as shown at B), until entering the intermediate dielectric layer 121 on the side wall of the deep trench isolation structure 111, thereby changing the incident angle, so that the photons whose incident angle is less than the critical value at this time can enter the vertical portion 123b from the intermediate dielectric layer 121 (as shown at C), and the photons then enter the photosensitive area I and are captured by the diode structure 125 (as shown at Y2), further improving the photon detection efficiency of the device.

[0076] Therefore, the present invention utilizes the deep trench isolation structure 111 which originally has no photosensitivity function, and sets a raised portion 123 with an inclined surface thereon, and combines the waveguide structure formed by the first dielectric layer 120, the intermediate dielectric layer 121 and the raised portion 123 on the surface of the second isolation portion 111b of the deep trench isolation structure 111 to adjust the reflection or refraction direction of photons incident on the top of the deep trench isolation structure 111, guide them into the photosensitive area I, and thus participate in photosensitivity, thereby increasing the number of photons that can be captured by the pixel units in each photosensitive area I, thereby improving the photon detection efficiency of the device.

[0077] In this embodiment, the material of the passivation layer 131 includes silicon nitride; the material of the protrusion 123 includes silicon oxide.

[0078] In other embodiments, the passivation layer and the protrusion may also be other materials satisfying that the refractive index of the passivation layer is greater than the refractive index of the protrusion.

[0079] In this embodiment, the material of the first dielectric layer 120 includes silicon oxide; the material of the protrusion 123 includes silicon oxide; and the material of the intermediate dielectric layer 121 includes silicon nitride.

[0080] In other embodiments, the material of the first dielectric layer further includes silicon nitride, oxide, polysilicon, copper, aluminum, tungsten or germanium; the material of the protrusion further includes silicon nitride, oxide, polysilicon, copper, aluminum, tungsten or germanium; the material of the intermediate dielectric layer further includes silicon nitride, oxide, polysilicon, copper, aluminum, tungsten or germanium. The material of the first dielectric layer can be the same as or different from the material of the protrusion; the materials of the first dielectric layer, the protrusion, and the intermediate dielectric layer need to satisfy: the refractive index of the material of the intermediate dielectric layer is greater than the refractive index of the material of the first dielectric layer, and the refractive index of the material of the intermediate dielectric layer is greater than the refractive index of the material of the protrusion, so that the first dielectric layer, the protrusion, and the intermediate dielectric layer constitute a waveguide structure.

[0081] In this embodiment, the top surface of the deep trench isolation structure 111 is higher than the surface of the isolation region II, and the deep trench isolation structure 111 includes a first isolation portion 111a located in the isolation region II and a second isolation portion 111b located on the surface of the isolation region II; the side wall and top surface of the second isolation portion 111b have a first dielectric layer 120, an intermediate dielectric layer 121 and a protruding portion 123.

[0082] In another embodiment, the top surface of the deep trench isolation structure is flush with the surface of the isolation region. The top surface of the deep trench isolation structure is in direct contact with the protrusion, the surface of the protrusion is protruding relative to the substrate surface, and the center of the protrusion is higher than the edge of the protrusion, so that the surface formed by the protruding vertex of the protrusion to the edge of the protrusion is inclined relative to the substrate surface, and the inclined surface faces the photosensitive area. Wherein, the protrusion is only located on the top surface of the deep trench isolation structure.

[0083] Specifically, the method for forming the raised portion includes: forming a second material layer on the surface of the substrate and the top surface of the deep trench isolation structure; etching a portion of the second material layer on the isolation area to form a raised portion located on the top surface of the deep trench isolation structure; and removing the second material layer on the surface of the photosensitive area.

[0084] In other embodiments, the protrusion is also in direct contact with the top surface and the sidewall surface of the deep trench isolation structure.

[0085] Correspondingly, an embodiment of the present invention further provides a photodetector formed by the above method.

[0086] Please continue to refer to Figure 7 and Figure 8The photodetector comprises: a substrate 100, wherein the substrate 100 comprises a plurality of photosensitive regions I and an isolation region II between the photosensitive regions I; a diode structure 125 located in each of the photosensitive regions I; a deep trench isolation structure 111 located in the isolation region II; a raised portion 123 located at least on the top surface of the deep trench isolation structure 111, wherein the surface of the raised portion 123 is raised relative to the surface of the substrate 100, and the center of the raised portion 123 is higher than the edge of the raised portion 123; and a passivation layer 131 located on the surface of the raised portion 123, wherein the refractive index of the material of the passivation layer 131 is greater than the refractive index of the material of the raised portion 123.

[0087] The surface formed by the protruding apex of the protrusion 123 to the edge of the protrusion 123 is inclined relative to the surface of the substrate 100 , and the inclined surface faces the photosensitive area I.

[0088] In this embodiment, the raised portion 123 located on the top surface of the deep trench isolation structure 111 has a symmetry plane, the raised portion 123 is axially symmetric about the symmetry plane, the symmetry plane of the raised portion 123 coincides with the symmetry plane of the deep trench isolation structure 111, and the protruding vertex of the raised portion 123 is located on the symmetry plane.

[0089] In this embodiment, the cross-sectional figure of the raised portion 123 located on the top surface of the deep trench isolation structure 111 along the first plane direction includes a triangle, one side of the triangle is parallel to the surface of the substrate 100, and the first plane direction is perpendicular to the surface of the substrate 100 and parallel to the arrangement direction P of each photosensitive area I.

[0090] In other embodiments, the cross-sectional shape of the raised portion located on the top surface of the deep trench isolation structure along the first plane direction includes a trapezoid, a semicircle or a semi-ellipse, and the first plane direction is perpendicular to the substrate surface and parallel to the arrangement direction of each photosensitive area.

[0091] In this embodiment, the material of the passivation layer 131 includes silicon nitride; the material of the protrusion 123 includes silicon oxide.

[0092] In this embodiment, the top surface of the deep trench isolation structure 111 is higher than the surface of the isolation region II. The deep trench isolation structure 111 includes a first isolation portion 111 a located in the isolation region II and a second isolation portion 111 b located on the surface of the isolation region II.

[0093] In this embodiment, the surface of the deep trench isolation structure 111 also has a composite dielectric layer, and the composite dielectric layer includes: a first dielectric layer 120 located on the top and side wall surface of the second isolation portion 111b, and an intermediate dielectric layer 121 located on the surface of the first dielectric layer 120, the protrusion 123 is located on the surface of the intermediate dielectric layer 121, the refractive index of the material of the intermediate dielectric layer 121 is greater than the refractive index of the material of the first dielectric layer 120, and the refractive index of the material of the intermediate dielectric layer 121 is greater than the refractive index of the material of the protrusion 123.

[0094] The protrusion 123 is also located on the surface of the intermediate dielectric layer 121 on the side wall of the second isolation portion 111 b.

[0095] In this embodiment, the material of the first dielectric layer 120 includes silicon oxide; the material of the protrusion 123 includes silicon oxide; and the material of the intermediate dielectric layer 121 includes silicon nitride.

[0096] In another embodiment, a top surface of the deep trench isolation structure is flush with a surface of the isolation region.

[0097] In this embodiment, since the top surface of the deep trench isolation structure 111 has a protrusion 123, the surface formed by the protruding vertex to the edge of the protrusion 123 is inclined relative to the surface of the substrate 100, and the inclined surface faces the photosensitive area I. Since the refractive index of the passivation layer 131 is greater than the refractive index of the protrusion 123, when light is incident on the top of the deep trench isolation structure 111, at least part of the photons are totally reflected on the inclined surface of the protrusion 123. By utilizing the inclination angle, the photons can be reflected into the photosensitive area I and captured by the diode structure 125. Therefore, the scheme of the present invention utilizes the deep trench isolation structure 111 that originally does not have a photosensitivity function, and by providing the protrusion 123 thereon, the photons incident on the top of the deep trench isolation structure 111 can enter the photosensitive area I and participate in photosensitivity, thereby increasing the number of photons that can be captured by each pixel unit, thereby improving the photon detection efficiency of the device.

[0098] Furthermore, since the surface of the deep trench isolation structure 111 also has a composite dielectric layer, the composite dielectric layer includes: a first dielectric layer 120 located on the top and sidewall surface of the second isolation portion 111b, and an intermediate dielectric layer 121 located on the surface of the first dielectric layer 120, and the protrusion 123 is located on the surface of the intermediate dielectric layer 121; the refractive index of the material of the intermediate dielectric layer 121 is greater than the refractive index of the material of the first dielectric layer 120 and the material of the protrusion 123, therefore, the composite dielectric layer and the protrusion 123 constitute a waveguide Structure, after the photons pass through the passivation layer 131 and the protrusion 123 in sequence and enter the intermediate dielectric layer 121, at least part of the photons can be totally reflected back and forth in the intermediate dielectric layer 121 at the top of the second isolation portion 111b until they enter the intermediate dielectric layer 121 on the side wall of the second isolation portion 111b, thereby changing the incident angle, so that the photons that meet the incident angle less than the critical value at this time can enter the vertical portion 123b from the intermediate dielectric layer 121, and then enter the photosensitive area I to be captured by the diode structure 125, further improving the photon detection efficiency of the device.

[0099] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A photoelectric detector, characterized in that: include: A substrate, the substrate comprising a plurality of photosensitive regions and isolation regions between the photosensitive regions; A diode structure located in each of the photosensitive regions; a deep trench isolation structure located in the isolation region; a raised portion at least located on the top surface of the deep trench isolation structure, wherein the surface of the raised portion is raised relative to the substrate surface, and the center of the raised portion is higher than the edge of the raised portion; A passivation layer is located on the surface of the protrusion, and the refractive index of the material of the passivation layer is greater than the refractive index of the material of the protrusion.

2. The photodetector according to claim 1, wherein: The raised portion on the top surface of the deep trench isolation structure has a symmetry plane. The raised portion is axially symmetric about the symmetry plane. The symmetry plane of the raised portion coincides with the symmetry plane of the deep trench isolation structure. The protruding apex of the raised portion is located on the symmetry plane.

3. The photodetector according to claim 2, wherein: The cross-sectional figure of the raised portion located on the top surface of the deep trench isolation structure along the first plane direction includes a triangle, one side of the triangle is parallel to the substrate surface, and the first plane direction is perpendicular to the substrate surface and parallel to the arrangement direction of each photosensitive area.

4. The photodetector according to claim 2, wherein: The cross-sectional shape of the protrusion located on the top surface of the deep trench isolation structure along the first plane direction includes a trapezoid, a semicircle or a semi-ellipse, and the first plane direction is perpendicular to the substrate surface and parallel to the arrangement direction of each photosensitive area.

5. The photodetector according to claim 1, wherein: The material of the passivation layer includes silicon nitride; the material of the protrusion includes silicon oxide.

6. The photodetector according to claim 1, wherein: The top surface of the deep trench isolation structure is flush with the surface of the isolation region.

7. The photodetector according to claim 1, wherein: The top surface of the deep trench isolation structure is higher than the surface of the isolation region. The deep trench isolation structure includes a first isolation portion located in the isolation region and a second isolation portion located on the surface of the isolation region.

8. The photodetector according to claim 7, wherein: The surface of the deep trench isolation structure also has a composite dielectric layer, which includes: a first dielectric layer located on the top and side wall surface of the second isolation portion, and an intermediate dielectric layer located on the surface of the first dielectric layer, the protrusion is located on the surface of the intermediate dielectric layer, the refractive index of the intermediate dielectric layer material is greater than the refractive index of the first dielectric layer material, and the refractive index of the intermediate dielectric layer material is greater than the refractive index of the protrusion material.

9. The photodetector according to claim 8, wherein: The protrusion is also located on the surface of the intermediate dielectric layer of the side wall of the second isolation portion.

10. The photodetector according to claim 8, wherein: The material of the first dielectric layer includes silicon oxide; the material of the protruding portion includes silicon oxide; and the material of the intermediate dielectric layer includes silicon nitride.

11. A method for forming a photodetector, characterized in that: include: Providing a substrate, the substrate comprising a plurality of photosensitive regions and isolation regions between the photosensitive regions; forming a deep trench isolation structure between adjacent photosensitive regions; forming a diode structure in each photosensitive region; forming a protrusion on at least the top surface of the deep trench isolation structure, wherein the surface of the protrusion is protruding relative to the surface of the substrate, and the center of the protrusion is higher than the edge of the protrusion; A passivation layer is formed on the surface of the protrusion, and the refractive index of the material of the passivation layer is greater than the refractive index of the material of the protrusion.

12. The method for forming a photodetector according to claim 11, wherein: The top surface of the deep trench isolation structure is higher than the surface of the isolation region. The deep trench isolation structure includes a first isolation portion located in the isolation region and a second isolation portion located on the surface of the isolation region.

13. The method for forming a photodetector according to claim 12, wherein: A composite dielectric layer is formed on the surface of the deep trench isolation structure, the composite dielectric layer comprising: a first dielectric layer located on the top and sidewall surfaces of the second isolation portion, and an intermediate dielectric layer located on the top and sidewall surfaces of the first dielectric layer, the protrusion is located on the surface of the intermediate dielectric layer, the refractive index of the material of the intermediate dielectric layer is greater than the refractive index of the material of the first dielectric layer, and the refractive index of the material of the intermediate dielectric layer is greater than the refractive index of the material of the protrusion.

14. The method for forming a photodetector according to claim 13, wherein: The method for forming the composite dielectric layer and the protruding portion includes: forming a first dielectric layer on the surface of the substrate, the top surface of the second isolation portion, and the side wall surface of the second isolation portion; forming an intermediate material layer on the surface of the first dielectric layer; forming a second material layer on the surface of the intermediate material layer; etching a portion of the second material layer on the isolation region to form a horizontal portion on the intermediate dielectric layer located on the top surface of the second isolation portion; removing the second material layer and the intermediate material layer on the surface of the photosensitive region to form an intermediate dielectric layer on the surface of the first dielectric layer located on the top surface and the side wall surface of the second isolation portion and a vertical portion on the surface of the intermediate dielectric layer located on the side wall of the second isolation portion, wherein the horizontal portion and the vertical portion together constitute a protruding portion.

15. The method for forming a photodetector according to claim 11, wherein: The top surface of the deep trench isolation structure is flush with the surface of the isolation region.

16. The method for forming a photodetector according to claim 15, wherein: The method for forming the raised portion includes: forming a second material layer on the surface of the substrate and the top surface of the deep trench isolation structure; etching a portion of the second material layer on the isolation area to form a raised portion located on the top surface of the deep trench isolation structure; and removing the second material layer on the surface of the photosensitive area.

Images