Image sensor structure

Abstract

The invention discloses an image sensor structure which comprises a substrate and a pixel structure. The substrate includes a front surface and a back surface opposite to each other. The pixel structure includes a gate, a dielectric layer, a light detector and a floating diffusion region. The gate is in the substrate. The gate includes a first surface and a second surface opposite to each other. The first surface is closer to the front surface than the second surface. The width of the first surface is different from that of the second surface. The dielectric layer is located between the gate and the substrate. The light detector is located in the substrate at one side of the grid electrode. The floating diffusion region is located in the substrate between the front surface and the light detector.

Description

Technical Field

[0001] The present invention relates to a semiconductor structure, and in particular to an image sensor structure. Background Art

[0002] Image sensors are currently widely used in many modern electronic devices (e.g., smartphones and digital cameras). However, further improving full well capacity (FWC) and reducing optical crosstalk are ongoing efforts. Summary of the Invention

[0003] The present invention provides an image sensor structure, which can increase full well capacity and reduce optical crosstalk, thereby improving image quality.

[0004] The present invention provides an image sensor structure comprising a substrate and a pixel structure. The substrate includes a front surface and a back surface facing each other. The pixel structure includes a gate, a dielectric layer, a photodetector (PD), and a floating diffusion (FD). The gate is located in the substrate. The gate includes a first surface and a second surface facing each other. The first surface is closer to the front surface than the second surface. The width of the first surface is different from the width of the second surface. The dielectric layer is located between the gate and the substrate. The photodetector is located in the substrate on one side of the gate. The floating diffusion is located in the substrate between the front surface and the photodetector.

[0005] According to an embodiment of the present invention, in the image sensor structure, the cross-section of the gate electrode may be a trapezoid.

[0006] According to an embodiment of the present invention, in the image sensor structure, the gate may extend from the front surface toward the back surface.

[0007] According to an embodiment of the present invention, in the above-mentioned image sensor structure, the image sensor structure may be a backside illuminated image sensor (BSI image sensor) structure, and the back side may be the light incident side.

[0008] According to an embodiment of the present invention, in the above-mentioned image sensor structure, the pixel structure may be a blue pixel structure.

[0009] According to an embodiment of the present invention, in the image sensor structure, the width of the second surface may be greater than the width of the first surface.

[0010] According to an embodiment of the present invention, in the above-mentioned image sensor structure, the image sensor structure may be a back-illuminated image sensor structure, and the back surface may be the light incident surface.

[0011] According to an embodiment of the present invention, in the above-mentioned image sensor structure, the pixel structure may be a green pixel structure.

[0012] According to an embodiment of the present invention, in the image sensor structure, the width of the second surface may be smaller than the width of the first surface.

[0013] According to an embodiment of the present invention, in the above-mentioned image sensor structure, the image sensor structure may be a front side illuminated image sensor (FSI image sensor) structure, and the front side may be the light incident side.

[0014] According to an embodiment of the present invention, in the above-mentioned image sensor structure, the pixel structure may be a blue pixel structure.

[0015] According to an embodiment of the present invention, in the image sensor structure, the width of the first surface may be greater than the width of the second surface.

[0016] According to an embodiment of the present invention, in the above-mentioned image sensor structure, the image sensor structure may be a front-illuminated image sensor structure, and the front side may be the light incident side.

[0017] According to an embodiment of the present invention, in the above-mentioned image sensor structure, the pixel structure may be a green pixel structure.

[0018] According to an embodiment of the present invention, in the image sensor structure, the width of the first surface may be smaller than the width of the second surface.

[0019] According to an embodiment of the present invention, in the image sensor structure, the light detector may have a protrusion protruding toward the front.

[0020] According to an embodiment of the present invention, in the image sensor structure, a top surface of the protrusion may be higher than a bottom surface of the floating diffusion region and may be lower than a top surface of the floating diffusion region.

[0021] According to one embodiment of the present invention, the image sensor structure may further include an isolation structure disposed in the substrate. The photodetector may be disposed between the gate and the isolation structure.

[0022] According to an embodiment of the present invention, in the image sensor structure, the isolation structure may extend from the front surface toward the back surface.

[0023] According to an embodiment of the present invention, the image sensor structure may include a plurality of pixel structures, and the plurality of pixel structures may share a gate.

[0024] Based on the above, in the image sensor structure proposed by the present invention, since the gate is located in the substrate, it can effectively increase the full well capacity, thereby improving image quality. Furthermore, the gate includes a first surface and a second surface that oppose each other, with the first surface being closer to the front surface than the second surface, and the first surface having a different width than the second surface. Therefore, for specific pixel structures (e.g., blue pixel structures or green pixel structures), optical crosstalk can be reduced by adjusting the width relationship between the first and second gate surfaces, thereby improving image quality.

[0025] In order to make the above features and advantages of the present invention more clearly understood, embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A top view of an image sensor structure according to some embodiments of the present invention;

[0027] Figure 2 For some embodiments of the present invention along Figure 1 The cross-sectional view along the section line I-I';

[0028] Figure 3 For other embodiments of the present invention, Figure 1 The cross-sectional view along the section line I-I';

[0029] Figure 4 For other embodiments of the present invention, Figure 1 The cross-sectional view along the section line I-I';

[0030] Figure 5 For other embodiments of the present invention, Figure 1 Sectional view along section line I-I'.

[0031] Explanation of symbols

[0032] 10: Image sensor structure

[0033] 100: Base

[0034] 102: Gate

[0035] 104: dielectric layer

[0036] 106: Light Detector

[0037] 108: floating diffusion area

[0038] 110: Isolation Structure

[0039] D1: Direction

[0040] P1: protrusion

[0041] PS1: Pixel structure

[0042] S1: Front

[0043] S2: Back

[0044] S3: Side 1

[0045] S4: Side 2

[0046] S5, S7: top surface

[0047] S6: bottom

[0048] W1, W2: width DETAILED DESCRIPTION

[0049] The following examples are illustrated in detail with accompanying drawings, but the examples provided are not intended to limit the scope of the present invention. For ease of understanding, identical components will be designated by the same reference numerals throughout the following description. Furthermore, the drawings are for illustrative purposes only and are not drawn to scale. Furthermore, features in the top views are not drawn to the same scale as those in the cross-sectional views. Indeed, the dimensions of various features may be arbitrarily increased or decreased for clarity.

[0050] Figure 1 FIG. 1 is a top view of an image sensor structure according to some embodiments of the present invention. Figure 2 According to some embodiments of the present invention Figure 1 The cross-section of the I-I' section line. Figure 1 in, omit Figure 2 To clearly illustrate some of the components in Figure 1 The relationship between components in the setting. Figure 3 According to some other embodiments of the present invention Figure 1 Sectional view along section line I-I'. Figure 4 According to some other embodiments of the present invention Figure 1 Sectional view along section line I-I'. Figure 5 According to some other embodiments of the present invention Figure 1 Sectional view along section line I-I'.

[0051] Please refer to Figure 1 and Figure 2Image sensor structure 10 includes a substrate 100 and a pixel structure PS1. Substrate 100 includes a front surface S1 and a back surface S2 facing each other. Substrate 100 can be a single-layer structure or a multi-layer structure. In some embodiments, substrate 100 can be a semiconductor substrate. In some embodiments, substrate 100 can be a silicon substrate, an epitaxial layer, or a combination thereof.

[0052] Pixel structure PS1 includes a gate 102, a dielectric layer 104, a photodetector 106, and a floating diffusion region 108. Gate 102 is located within substrate 100. Because gate 102 is located within substrate 100, it effectively increases full well capacity, thereby improving image quality. In some embodiments, gate 102 may extend in a direction D1 from front surface S1 toward back surface S2. In some embodiments, gate 102 may have a trapezoidal cross-section. Gate 102 may have a single-layer structure or a multi-layer structure. In some embodiments, gate 102 may be made of a conductive material, such as titanium nitride (TiN).

[0053] The gate 102 includes a first surface S3 and a second surface S4 facing each other. The first surface S3 is closer to the front surface S1 than the second surface S4. The width W1 of the first surface S3 is different from the width W2 of the second surface S4. In this embodiment, Figure 2 As shown, the width W2 of the second surface S4 may be greater than the width W1 of the first surface S3, but the present invention is not limited thereto. In other embodiments, such as Figure 3 As shown, the width W2 of the second surface S4 may be smaller than the width W1 of the first surface S3.

[0054] In some embodiments, as Figure 2 As shown, the image sensor structure 10 can be a back-illuminated image sensor structure, the back surface S2 can be the light incident surface, the pixel structure PS1 can be a blue pixel structure, and the width W2 of the second surface S4 can be greater than the width W1 of the first surface S3, thereby reducing optical crosstalk and improving image quality.

[0055] In other embodiments, Figure 2 As shown, the image sensor structure 10 can be a front-illuminated image sensor structure, the front surface S1 can be a light incident surface, the pixel structure PS1 can be a green pixel structure, and the width W1 of the first surface S3 can be smaller than the width W2 of the second surface S4, thereby reducing optical crosstalk and improving image quality.

[0056] In some embodiments, as Figure 3 As shown, the image sensor structure 10 can be a back-illuminated image sensor structure, the back surface S2 can be the light incident surface, the pixel structure PS1 can be a green pixel structure, and the width W2 of the second surface S4 can be smaller than the width W1 of the first surface S3, thereby reducing optical crosstalk and improving image quality.

[0057] In other embodiments, Figure 3 As shown, the image sensor structure 10 can be a front-illuminated image sensor structure, the front surface S1 can be a light incident surface, the pixel structure PS1 can be a blue pixel structure, and the width W1 of the first surface S3 can be greater than the width W2 of the second surface S4, thereby reducing optical crosstalk and improving image quality.

[0058] Dielectric layer 104 is located between gate 102 and substrate 100. In some embodiments, dielectric layer 104 is made of a dielectric material such as aluminum oxide (Al2O3). Photodetector 106 is located in substrate 100 on one side of gate 102. In some embodiments, photodetector 106 can be a photodiode. Floating diffusion region 108 is located in substrate 100 between front surface S1 and photodetector 106. In some embodiments, floating diffusion region 108 can be a doped region.

[0059] In other embodiments, compared to Figure 2 Image sensor structure 10, Figure 4 The light detector 106 in the image sensor structure 10 may have a protrusion P1 protruding toward the front surface S1, thereby further increasing the full well capacity. Figure 3 Image sensor structure 10, Figure 5 The light detector 106 in the image sensor structure 10 may have a protrusion P1 protruding toward the front surface S1, thereby further increasing the full well capacity. Figure 4 and Figure 5 In the embodiment, a top surface S5 of the protrusion P1 may be higher than a bottom surface S6 of the floating diffusion region 108 and may be lower than a top surface S7 of the floating diffusion region 108 .

[0060] Please refer to Figure 1 and Figure 2 Image sensor structure 10 may further include isolation structure 110. Isolation structure 110 is located in substrate 100. Photodetector 106 may be located between gate 102 and isolation structure 110. In some embodiments, isolation structure 110 may extend in a direction D1 from front surface S1 toward back surface S2. In some embodiments, isolation structure 110 may be a deep trench isolation (DTI) structure, a shallow trench isolation (STI) structure, or a combination thereof. In some embodiments, isolation structure 110 may be a continuous structure or a discontinuous structure. In some embodiments, isolation structure 110 may be made of silicon oxide.

[0061] In some embodiments, as Figure 1As shown, the image sensor structure 10 may include multiple pixel structures PS1. The multiple pixel structures PS1 may share a gate 102. In some embodiments, the multiple pixel structures PS1 may all be blue pixel structures. In some embodiments, the multiple pixel structures PS1 may all be green pixel structures. In some embodiments, the multiple pixel structures PS1 may all be red pixel structures. In some embodiments, the multiple pixel structures PS1 may be any combination of blue pixel structures, green pixel structures, and red pixel structures. In some embodiments, as Figure 1 As shown, the top view shape of the gate 102 may include a cross.

[0062] In addition, Figures 2 to 5 In the semiconductor structure 10, identical or similar components are denoted by identical reference numerals, and their descriptions are omitted. Furthermore, although not shown in the figure, the image sensor structure 10 may include necessary components such as a color filter layer, a microlens, and / or a desired doped region, and their descriptions are omitted here.

[0063] Based on the above embodiments, it can be seen that in the image sensor structure 10, since the gate 102 is located in the substrate 100, it can effectively increase the full well capacity, thereby improving image quality. Furthermore, the gate 102 includes a first surface S3 and a second surface S4 that are opposite each other. The first surface S3 is closer to the front surface S1 than the second surface S4, and the width W1 of the first surface S3 is different from the width W2 of the second surface S4. Therefore, for a specific pixel structure PS1 (e.g., a blue pixel structure or a green pixel structure), optical crosstalk can be reduced by adjusting the width relationship between the first surface S3 and the second surface S4 of the gate 102, thereby improving image quality.

[0064] In summary, in the image sensor structure of the above embodiment, since the gate is located in the substrate, it effectively increases the full well capacity, thereby improving image quality. Furthermore, the gate includes a first surface and a second surface that oppose each other, with the first surface being closer to the front surface than the second surface, and the first surface having a different width than the second surface. Therefore, for specific pixel structures (e.g., blue or green pixel structures), optical crosstalk can be reduced by adjusting the width relationship between the first and second gate surfaces, thereby improving image quality.

[0065] Although the present invention has been disclosed above with reference to the embodiments, they are not intended to limit the present invention. Any person skilled in the art may make slight changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the definition of the appended claims.

Claims

1. An image sensor structure, comprising: a substrate, comprising a front side and a back side facing each other; as well as Pixel structure, including: a gate disposed in the substrate and comprising a first surface and a second surface opposite to each other, wherein the first surface is closer to the front surface than the second surface, and a width of the first surface is different from a width of the second surface; a dielectric layer located between the gate and the substrate; a light detector located in the substrate on one side of the gate; and A floating diffusion region is located in the substrate between the front surface and the light detector.

2. The image sensor structure of claim 1, wherein a cross-sectional shape of the gate comprises a trapezoid. 3 . The image sensor structure of claim 1 , wherein the gate extends in a direction from the front surface toward the back surface. 4 . The image sensor structure as claimed in claim 1 , wherein the image sensor structure is a back-illuminated image sensor structure, and the back surface is a light incident surface. 5 . The image sensor structure as claimed in claim 4 , wherein the pixel structure is a blue pixel structure. The image sensor structure as claimed in claim 5 , wherein a width of the second surface is greater than a width of the first surface. 7 . The image sensor structure as claimed in claim 1 , wherein the image sensor structure is a back-illuminated image sensor structure, and the back surface is a light incident surface.

8. The image sensor structure as claimed in claim 7, wherein the pixel structure is a green pixel structure. 9 . The image sensor structure of claim 8 , wherein a width of the second surface is smaller than a width of the first surface. 10 . The image sensor structure as claimed in claim 1 , wherein the image sensor structure is a front-illuminated image sensor structure, and the front surface is a light incident surface. The image sensor structure as claimed in claim 10 , wherein the pixel structure is a blue pixel structure. 12 . The image sensor structure of claim 11 , wherein a width of the first surface is greater than a width of the second surface. 13 . The image sensor structure as claimed in claim 1 , wherein the image sensor structure is a front-illuminated image sensor structure, and the front surface is a light incident surface.

14. The image sensor structure as claimed in claim 13, wherein the pixel structure is a green pixel structure. 15 . The image sensor structure of claim 14 , wherein a width of the first surface is smaller than a width of the second surface.

16. The image sensor structure of claim 1, wherein the light detector has a protrusion protruding toward the front surface. 17 . The image sensor structure of claim 16 , wherein a top surface of the protrusion is higher than a bottom surface of the floating diffusion region and lower than a top surface of the floating diffusion region.

18. The image sensor structure according to claim 1, further comprising: An isolation structure is located in the substrate, wherein the photodetector is located between the gate and the isolation structure.

19. The image sensor structure of claim 18, wherein the isolation structure extends in a direction from the front surface toward the back surface. 20 . The image sensor structure as claimed in claim 1 , comprising a plurality of the pixel structures, wherein the plurality of pixel structures share the gate.

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