Image sensor manufacturing method and image sensor

Abstract

The present invention provides a method for preparing an image sensor and an image sensor. The image sensor comprises: an active passivation layer containing a charge storage region; a transparent conductive film covering the active passivation layer; an insulating layer covering the sidewalls of the active passivation layer; and a metal conductor electrically connecting the transparent conductive film to a control circuit. This technical solution allows the active passivation layer to capture and store electrons, making it difficult for photogenerated electrons to reach the light-incident surface of the image sensor, thereby reducing surface dark current and significantly improving the image quality of the image sensor. Furthermore, the electrical connection between the transparent conductive film and the control circuit enables periodic active control of the passivation layer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductors, and in particular to a method for preparing an image sensor and the image sensor. Background Art

[0002] For image sensors, the newly exposed silicon surface after backside thinning can contain defects, dangling bonds, and damage, which can generate surface dark current. This can dramatically increase image sensor noise, significantly degrade image quality, and even make effective imaging impossible. Therefore, reducing surface dark current is crucial for image sensor applications. Summary of the Invention

[0003] The technical problem to be solved by the present invention is dark current on the surface of an image sensor, and a method for preparing an image sensor and the image sensor are provided.

[0004] The present invention provides a method for preparing an image sensor, comprising the following steps: depositing an active passivation layer on a light-incident surface of the image sensor, the active passivation layer comprising a charge storage region; growing a transparent conductive film on the surface of the active passivation layer; patterning the active passivation layer and removing a corresponding portion of the transparent conductive film to expose a control circuit disposed within the image sensor; and forming a metal wire for electrically connecting the transparent conductive film and the control circuit.

[0005] The present invention also provides an image sensor, comprising: an active passivation layer, the active passivation layer including a charge storage area; a transparent conductive film covering the active passivation layer; an insulating layer, the insulating layer covering the sidewalls of the active passivation layer; and a metal wire, the metal wire electrically connecting the transparent conductive film and a control circuit.

[0006] This technical solution uses an active passivation layer to capture and store electrons, preventing photogenerated electrons from reaching the light-entering surface of the image sensor. This reduces surface dark current and significantly improves image quality. Furthermore, the electrical connection between the transparent conductive film and the control circuit enables periodic active control of the passivation layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Attachment Figure 1 Shown is a schematic diagram of the steps described in a specific embodiment of the present invention.

[0008] Attachment Figures 2A-2H The attached Figure 1 Schematic diagram of the process of steps S11-S14.

[0009] Attachment Figure 3 FIG. 1 is a schematic diagram of the steps of forming the active passivation layer according to a specific embodiment of the present invention.

[0010] Attachment Figure 4 FIG. 1 is a schematic diagram of steps for forming metal conductive lines according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0011] The specific implementation of a method for preparing an image sensor provided by the present invention is described in detail below with reference to the accompanying drawings.

[0012] Attachment Figure 1 FIG2 is a schematic diagram of the steps of a specific embodiment of the present invention, including: step S11, depositing an active passivation layer on the light-incident surface of the image sensor, wherein the active passivation layer includes a charge storage area; step S12, growing a transparent conductive film on the surface of the active passivation layer; step S3, patterning the active passivation layer and removing a corresponding portion of the transparent conductive film to expose a control circuit disposed inside the image sensor; and step S14, forming a metal wire for electrically connecting the transparent conductive film and the control circuit.

[0013] Attachment Figures 2A-2C As shown, referring to step S11, an active passivation layer is deposited on the incident surface of the image sensor 202, and the active passivation layer includes a charge storage area. In a specific embodiment of the present invention, the formation of the active passivation layer can be carried out by the following method, and with reference to the attached Figure 3 The following steps are shown:

[0014] Attachment Figure 2A As shown, referring to step S31, a first dielectric layer 204 is grown on the light incident surface of the image sensor 202. The image sensor 202 includes a control circuit 201 and a through-silicon via 203. In one embodiment, the first dielectric layer 204 is made of silicon dioxide or silicon oxynitride, and has a thickness of 1 nm to 20 nm.

[0015] Attachment Figure 2B As shown, referring to step S32, a second dielectric layer 205 is grown on the surface of the first dielectric layer 204. In one embodiment, the second dielectric layer 205 is made of silicon nitride, and the thickness of the second dielectric layer 205 is 5 nm to 40 nm.

[0016] Attachment Figure 2C As shown, referring to step S33, a third dielectric layer 206 is grown on the surface of the second dielectric layer 205. In one embodiment, the third dielectric layer 206 is made of silicon dioxide or silicon oxynitride, and has a thickness of 1 nm to 40 nm.

[0017] The charge storage region includes a charge storage interface formed of two heterogeneous materials, each of which is independently selected from any one of silicon oxide, silicon nitride, silicon oxynitride, zinc oxide, hafnium oxide, aluminum oxide, or lanthanum oxide. In other specific embodiments, multiple second dielectric layers 205 can be separated by the first dielectric layer 204 or the third dielectric layer 206 to form multiple charge storage regions. The charge storage region enables the active passivation layer to capture and store electrons, resulting in a higher energy level at the light incident surface of the image sensor 202, making it difficult for photogenerated electrons to reach the surface, thereby reducing the dark current on the surface of the image sensor 202 and providing a basis for periodically actively controlling the function of the active passivation layer.

[0018] Attachment Figure 2D As shown, referring to step S12, a transparent conductive film 207 is grown on the surface of the active passivation layer. The material of the transparent conductive film is graphene or black phosphorus.

[0019] Attachment Figure 2E As shown, referring to step S13 , the active passivation layer is patterned, and a corresponding portion of the transparent conductive film 207 is removed to expose the control circuit disposed inside the image sensor.

[0020] Attachment Figures 2F-2H As shown, referring to step S14, a metal wire 209 is formed for electrically connecting the transparent conductive film 207 and the control circuit 201. In a specific embodiment of the present invention, the metal wire 209 can be formed by the following method, and refer to the attached Figure 4 The following steps are shown:

[0021] Attachment Figure 2F As shown, referring to step S41 , the sidewalls of the active passivation layer are covered with an insulating layer 208 . The insulating layer 208 covers the sidewalls of the active passivation layer and the surface of the transparent conductive film 207 .

[0022] Attachment Figure 2G As shown, referring to step S42 , a connection window is opened on the insulating layer 208 .

[0023] Attachment Figure 2H As shown, referring to step S43, a metal wire 209 is formed in the connection window of the insulating layer to electrically connect the transparent conductive film 207 and the control circuit 201. The material of the metal wire 209 is selected from copper, aluminum, tungsten, titanium or nickel. The control circuit 201 is a clock circuit.

[0024] Next, a specific embodiment of the image sensor obtained after the above steps are implemented is given in conjunction with the accompanying drawings. The structure of the image sensor is: Figure 2H Shown, including:

[0025] An active passivation layer comprising a charge storage region; a transparent conductive film 207 covering the active passivation layer; an insulating layer 208 covering the sidewalls of the active passivation layer; and a metal wire 209 electrically connecting the transparent conductive film 207 to the control circuit 201. The control circuit 201 periodically applies voltage to the transparent conductive film 207 to achieve periodic active control of the passivation layer.

[0026] The above description is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an image sensor, characterized in that: The steps include: Depositing an active passivation layer on the light incident surface of the image sensor, the active passivation layer comprising a charge storage region using three layers of heterogeneous materials, the charge storage region including a first dielectric layer, a second dielectric layer, and a third dielectric layer, wherein the first dielectric layer is made of silicon oxide or silicon oxynitride, the second dielectric layer is made of silicon nitride, and the third dielectric layer is made of silicon oxide or silicon oxynitride; Growing a transparent conductive film on the surface of the active passivation layer; Patterning the active passivation layer and removing a corresponding portion of the transparent conductive film to expose a control circuit disposed inside the image sensor; A metal wire is formed to electrically connect the transparent conductive film and the control circuit.

2. The method according to claim 1, wherein The thickness of the first dielectric layer is 1 nm-20 nm, the thickness of the second dielectric layer is 5 nm-40 nm, and the thickness of the third dielectric layer is 1 nm-40 nm.

3. The method according to claim 1, wherein The material of the transparent conductive film is graphene or black phosphorus.

4. The method according to claim 1, wherein The material of the metal wire is selected from copper, aluminum, tungsten, titanium or nickel.

5. The method according to claim 1, wherein The control circuit is a clock circuit.

6. The method according to claim 1, wherein The step of forming the metal wire further comprises: Covering the sidewalls of the active passivation layer with an insulating layer; A metal wire is made in the connection window of the insulating layer to electrically connect the transparent conductive film and the control circuit.

7. An image sensor, characterized in that: include: an active passivation layer, the active passivation layer comprising a charge storage region using three layers of heterogeneous materials, the charge storage region including a first dielectric layer, a second dielectric layer, and a third dielectric layer, the first dielectric layer being made of silicon oxide or silicon oxynitride, the second dielectric layer being made of silicon nitride, and the third dielectric layer being made of silicon oxide or silicon oxynitride; a transparent conductive film covering the active passivation layer; an insulating layer, the insulating layer covering the sidewalls of the active passivation layer; A metal wire electrically connects the transparent conductive film and the control circuit.

8. The image sensor according to claim 7, wherein: The thickness of the first dielectric layer is 1 nm-20 nm.

9. The image sensor according to claim 7, wherein: The thickness of the second dielectric layer is 5 nm-40 nm.

10. The image sensor according to claim 7, wherein: The thickness of the third dielectric layer is 1 nm-40 nm.

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