Backside illuminated image sensor structure and manufacturing method thereof

Abstract

A back-illuminated image sensor structure includes a substrate structure, a photodetector, and a plurality of hemispherical grains. The substrate structure includes a front side and a back side facing each other. The back side has at least one recess. The photodetector is located in the substrate structure. The photodetector is adjacent to the front side. The plurality of hemispherical grains are located on the surface of the recess.

Description

Technical Field

[0001] This invention relates to a semiconductor structure and a method for manufacturing the same, and more particularly to a back-illuminated image sensor structure and a method for manufacturing the same. Prior Technology

[0002] Currently, back-illuminated image sensors (such as those described in U.S. Patent No. 10,510,799 (US 10,510,799 B2), U.S. Patent Publication No. 2023 / 0317758 (US 2023 / 0317758 A1), and U.S. Patent Publication No. 2022 / 0130881 (US 2022 / 0130881 A1)) are widely used in many modern electronic devices (such as smartphones or digital cameras). However, further improving the quantum efficiency (QE) of back-illuminated image sensors remains a continuous goal of ongoing research. Summary of the Invention

[0003] This invention provides a back-illuminated image sensor structure and its manufacturing method, which can effectively improve the quantum efficiency of the back-illuminated image sensor structure.

[0004] This invention proposes a back-illuminated image sensor structure, including a substrate structure, a photodetector, and a plurality of hemispherical grains (HSGs). The substrate structure includes a front side and a back side facing each other. The back side has at least one recess. The photodetector is located within the substrate structure, adjacent to the front side. The plurality of hemispherical grains are located on the surface of the recess.

[0005] According to an embodiment of the present invention, in the above-described back-illuminated image sensor structure, the material of the hemispherical grains is, for example, doped polycrystalline silicon.

[0006] According to one embodiment of the present invention, in the above-described back-illuminated image sensor structure, the back surface may have multiple recesses. The multiple recesses may have sloping sidewalls. The bottom of the multiple recesses may have pointed tips.

[0007] According to an embodiment of the present invention, in the above-described back-illuminated image sensor structure, the back side may include an inverted pyramid array (IPA) structure.

[0008] According to one embodiment of the present invention, in the above-described back-illuminated image sensor structure, the substrate structure may be a single-layer structure.

[0009] According to one embodiment of the present invention, in the above-described back-illuminated image sensor structure, the substrate structure may be a multi-layer structure.

[0010] According to an embodiment of the present invention, in the above-described back-illuminated image sensor structure, the substrate structure may include a first substrate layer, a second substrate layer, a first bonding layer, and a second bonding layer. The second substrate layer is located on the first substrate layer. The first bonding layer is located between the first substrate layer and the second substrate layer. The second bonding layer is located between the first bonding layer and the second substrate layer.

[0011] This invention proposes a method for manufacturing a back-illuminated image sensor structure, comprising the following steps: Providing a substrate structure. The substrate structure includes a front side and a back side facing each other. Forming a photodetector in the substrate structure. The photodetector is adjacent to the front side. Forming at least one recess on the back side. Forming a plurality of hemispherical grains on the surface of the recess.

[0012] According to an embodiment of the present invention, in the manufacturing method of the back-illuminated image sensor structure described above, the method for forming the recess is, for example, performing a wet etching process on the back side of the substrate structure.

[0013] According to an embodiment of the present invention, in the manufacturing method of the back-illuminated image sensor structure described above, the method for forming the substrate structure may include the following steps: providing a first substrate layer; forming a first bonding layer on the first substrate layer; providing a second substrate layer; forming a second bonding layer on the second substrate layer; and bonding the second bonding layer to the first bonding layer.

[0014] Based on the above, in the back-illuminated image sensor structure and manufacturing method proposed in this invention, multiple hemispherical grains are located on the recessed surface. In this way, incident light can be refracted through the hemispherical grains and enter the photodetector, allowing the photodetector to receive more incident light, thereby effectively improving the quantum efficiency of the back-illuminated image sensor structure and thus improving image quality.

[0015] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings for detailed explanation. Simple Explanation of the Diagram

[0016] Figures 1A to 1K are cross-sectional views illustrating the manufacturing process of a back-illuminated image sensor structure according to some embodiments of the present invention. Implementation

[0017] The following description provides detailed examples and accompanying drawings, but these examples are not intended to limit the scope of the invention. For ease of understanding, the same components will be designated with the same symbols in the following description. Furthermore, the drawings are for illustrative purposes only and are not drawn to their original dimensions. In fact, the dimensions of various features may be arbitrarily increased or decreased for clarity of explanation.

[0018] Figures 1A to 1K are cross-sectional views illustrating the manufacturing process of a back-illuminated image sensor structure according to some embodiments of the present invention.

[0019] Referring to FIG1A, a substrate layer 100 is provided. The substrate layer 100 may have a first surface S1 and a second surface S2 opposite to each other. In some embodiments, the substrate layer 100 may be a semiconductor substrate layer, such as a silicon substrate layer. In some embodiments, the material of the substrate layer 100 is, for example, epitaxial silicon. In some embodiments, an isolation structure 102 may be formed in the substrate layer 100. The isolation structure 102 is adjacent to the first surface S1. In some embodiments, the isolation structure 102 is, for example, a shallow trench isolation (STI) structure. In some embodiments, the material of the isolation structure 102 is, for example, a dielectric material such as an oxide (e.g., silicon oxide).

[0020] Furthermore, a photodetector 104 may be formed in the substrate layer 100. The photosensitive element 104 may be adjacent to the first surface S1. In some embodiments, the photodetector 104 is, for example, a photodiode. Additionally, a component layer 106 may be formed on the first surface S1. In some embodiments, the component layer 106 may include necessary components such as active elements (e.g., transistor elements), dielectric layers, and / or interconnect structures, the description of which is omitted here.

[0021] Referring to Figure 1B, the substrate layer 100 can be thinned from the second surface S2. In some embodiments, the thinning process is, for example, a chemical mechanical polishing process.

[0022] Next, a bonding layer 108 may be formed on the substrate layer 100. The bonding layer 108 may be formed on the second surface S2. In some embodiments, the material of the bonding layer 108 is, for example, a dielectric material such as an oxide (e.g., silicon oxide). In some embodiments, the bonding layer 108 may be formed by, for example, thermal oxidation or chemical vapor deposition.

[0023] Referring to Figure 1C, a substrate layer 110 may be provided. The substrate layer 100 may have a third surface S3 and a fourth surface S4 opposite to each other. In some embodiments, the substrate layer 110 may be a semiconductor substrate layer, such as a silicon substrate layer. In some embodiments, the material of the substrate layer 110 is, for example, epitaxial silicon.

[0024] Next, a bonding layer 112 may be formed on the substrate layer 110. The bonding layer 112 may be formed on the third surface S3. In some embodiments, the material of the bonding layer 112 is, for example, a dielectric material such as an oxide (e.g., silicon oxide). In some embodiments, the bonding layer 112 may be formed by, for example, thermal oxidation or chemical vapor deposition.

[0025] Referring to FIG1D, bonding layer 112 may be bonded to bonding layer 108. In some embodiments, the method of bonding layer 112 to bonding layer 108 is, for example, fusion bonding.

[0026] Referring to Figure 1E, the substrate layer 110 can be thinned from the fourth surface S4. In some embodiments, the thinning process is, for example, a chemical mechanical polishing process.

[0027] By means of the above method, a substrate structure 114 can be provided, and a photodetector 104 can be formed in the substrate structure 114. In this embodiment, the substrate structure 114 may include a substrate layer 100, a substrate layer 110, a bonding layer 108, and a bonding layer 112. The substrate layer 110 is located on the substrate layer 100. The bonding layer 108 is located between the substrate layer 100 and the substrate layer 110. The bonding layer 112 is located between the bonding layer 108 and the substrate layer 110. The substrate structure 114 includes a front surface FS1 and a back surface BS1 opposite to each other. The photodetector 104 is adjacent to the front surface FS1. In some embodiments, the front surface FS1 of the substrate structure 114 may be the first surface S1 of the substrate layer 100, and the back surface BS1 of the substrate structure 114 may be the fourth surface S4 of the substrate layer 110. In this embodiment, the substrate structure 114 may be a multilayer structure, but the present invention is not limited thereto. In other embodiments, the substrate structure 114 may be a single-layer structure including only the substrate layer 100.

[0028] Referring to Figure 1F, at least one recess R1 is formed on the back side BS1. In some embodiments, the back side BS1 may have multiple recesses R1. The multiple recesses R1 may form an inverted pyramid array structure on the back side BS1. In some embodiments, the method for forming the recesses R1 is, for example, performing a wet etching process on the back side BS1 of the substrate structure 114. In some embodiments, the etchant used in the wet etching process is, for example, tetramethylammonium hydroxide (TMAH).

[0029] Referring to Figure 1G, a silicon material layer 116 can be formed on the surfaces of the back side BS1 and the recess R1. The material of the silicon material layer 116 is, for example, polycrystalline silicon. The method for forming the silicon material layer 116 is, for example, chemical vapor deposition.

[0030] Referring to Figure 1H, a thermal process can be performed on the silicon material layer 116 to form a plurality of hemispherical grains 116a. In the above thermal process, the bonding layer 108 and bonding layer 112 can have a heat-insulating effect to prevent damage to the components in the component layer 106 due to high temperatures. In some embodiments, the material of the hemispherical grains 116a can be doped, that is, the material of the hemispherical grains 116a can be doped silicon material. In some embodiments, the material of the hemispherical grains 116a is, for example, doped polycrystalline silicon (e.g., phosphorus-doped polycrystalline silicon). In some embodiments, the thermal process is, for example, a tempering process.

[0031] Referring to Figure 1I, hemispherical grains 116a located on the outside of the recess R1 can be removed. This allows multiple hemispherical grains 116a to be formed on the surface of the recess R1. In some embodiments, the method for removing the hemispherical grains 116a located on the outside of the recess R1 is, for example, chemical mechanical polishing.

[0032] Referring to Figure 1J, a deep trench T1 can be formed in the substrate structure 114. In some embodiments, the substrate structure 114 can be patterned by photolithography and etching processes to form the deep trench T1.

[0033] Next, a substrate 118 is conformally formed on the back surface BS1 and the hemispherical grain 116a, as well as in the deep trench T1. The substrate 118 may be a single-layer or multi-layer structure. In some embodiments, the material of the substrate 118 is, for example, an oxide (e.g., silicon oxide), a high dielectric constant material, or a combination thereof. In some embodiments, the substrate 118 is formed by, for example, atomic layer deposition.

[0034] Then, a filler layer 120 may be formed on the liner 118. The material of the filler layer 120 is, for example, an oxide (e.g., silicon oxide). In some embodiments, the filler layer 120 is formed by, for example, chemical vapor deposition. The filler layer 120 may then undergo a planarization process. In some embodiments, the planarization process is, for example, a chemical mechanical polishing process.

[0035] Using the method described above, a deep trench isolation structure D1 can be formed in the substrate structure 114. The deep trench isolation structure D1 may include a portion 120a of the filler layer 120 located in the deep trench T1. In some embodiments, the deep trench isolation structure D1 may further include a portion 118a of the liner layer 118 located in the deep trench T1.

[0036] Referring to Figure 1K, a color filter layer 122 can be formed on the filler layer 120. In some embodiments, the color filter layer 122 may be a red filter layer, a green filter layer, or a blue filter layer. Next, a microlens layer 124 can be formed on the color filter layer 122. The methods for forming the color filter layer 122 and the microlens layer 124 are well known to those skilled in the art and their description is omitted here.

[0037] Hereinafter, the back-illuminated image sensor structure 10 of this embodiment will be described with reference to FIG1K. Furthermore, although the method for forming the back-illuminated image sensor structure 10 is described using the method described above as an example, the present invention is not limited thereto.

[0038] Referring to Figure 1K, the back-illuminated image sensor structure 10 includes a substrate structure 114, a photodetector 104, and a plurality of hemispherical dies 116a. The substrate structure 114 includes a front surface FS1 and a back surface BS1 facing each other. The back surface BS1 has at least one recess R1. In some embodiments, the back surface BS1 may have multiple recesses R1. In some embodiments, the multiple recesses R1 may have sloping sidewalls SW1. In some embodiments, the bottom of the multiple recesses R1 may have a tip P1. In some embodiments, the back surface BS1 may include an inverted pyramid array structure. The photodetector 104 is located in the substrate structure 114. The photodetector 104 is adjacent to the front surface FS1. The plurality of hemispherical dies 116a are located on the surface of the recesses R1.

[0039] Furthermore, the remaining components in the back-illuminated image sensor structure 10 can be described with reference to the above embodiments. In addition, the details of each component in the back-illuminated image sensor structure 10 (e.g., materials and formation methods) have been described in detail in the above embodiments, and will not be described again here.

[0040] As can be seen from the above embodiments, in the back-illuminated image sensor structure 10 and its manufacturing method, a plurality of hemispherical grains 116a are located on the surface of the recess R1. In this way, incident light can be refracted through the hemispherical grains 116a into the photodetector 104, so that the photodetector 104 receives more incident light, thereby effectively improving the quantum efficiency of the back-illuminated image sensor structure 10 and thus improving image quality.

[0041] In summary, in the back-illuminated image sensor structure and its manufacturing method described in the above embodiments, the back-illuminated image sensor structure includes a substrate structure, a photodetector, and a plurality of hemispherical grains. The substrate structure includes a front side and a back side facing each other. The back side has at least one recess. The photodetector is located in the substrate structure. The photodetector is adjacent to the front side. The plurality of hemispherical grains are located on the surface of the recess. In this way, incident light can be refracted through the hemispherical grains into the photodetector, allowing the photodetector to receive more incident light, thereby effectively improving the quantum efficiency of the back-illuminated image sensor structure and thus improving image quality.

[0042] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0043] 10: Back-illuminated image sensor structure 100, 110: Basal layer 102: Isolation Structure 104: Light Detector 106: Component Layer 108, 112: Bonding layer 114: Base Structure 116: Silicon material layer 116a: Hemispherical grains 118: Lining 120: Fill layer 118a, 120a: Partial 122: Color Filter Layer 124: Microlens layer SW1: Sidewall D1: Deep Ditch Isolation Structure BS1: Back FS1: Front P1: Tip R1: Depression S1: First Page S2: Second side S3: Third Side S4: Fourth Page T1: Deep Ditch

Claims

1. A back-illuminated image sensor structure, comprising: A base structure comprising a front side and a back side opposite to each other, wherein the back side has at least one recess; A photodetector is located in the substrate structure and adjacent to the front side; and a plurality of hemispherical grains are located on the recessed surface.

2. The back-illuminated image sensor structure as claimed in claim 1, wherein the material of the hemispherical grain comprises doped polycrystalline silicon.

3. The back-illuminated image sensor structure as claimed in claim 1, wherein the back surface has a plurality of said recesses, the plurality of said recesses having sloping sidewalls, and the bottom of the plurality of said recesses having a pointed tip.

4. The back-illuminated image sensor structure as described in claim 1, wherein the back side includes an inverted pyramid array structure.

5. The back-illuminated image sensor structure as claimed in claim 1, wherein the substrate structure comprises a single-layer structure.

6. The back-illuminated image sensor structure as claimed in claim 1, wherein the substrate structure comprises a multilayer structure.

7. The back-illuminated image sensor structure as claimed in claim 1, wherein the substrate structure comprises: First basal layer; The second base layer is located on the first base layer; The first bonding layer is located between the first base layer and the second base layer; And a second bonding layer, located between the first bonding layer and the second base layer.

8. A method for manufacturing a back-illuminated image sensor structure, comprising: A substrate structure is provided, wherein the substrate structure includes a front side and a back side opposite to each other; A photodetector is formed in the substrate structure, wherein the photodetector is adjacent to the front side; at least one recess is formed on the back side; and a plurality of hemispherical grains are formed on the surface of the recess.

9. A method of manufacturing a back-illuminated image sensor structure as claimed in claim 8, wherein the method of forming the recess includes performing a wet etching process on the back side of the substrate structure.

10. A method for manufacturing a back-illuminated image sensor structure as described in claim 8, wherein the method for forming the substrate structure includes: Provide a first base layer; A first bonding layer is formed on the first base layer; Provide a second base layer; A second bonding layer is formed on the second base layer; And to bond the second bonding layer to the first bonding layer.

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