TWI818654B - Image sensor and manufacturing method thereof - Google Patents

Abstract

An image sensor including a substrate, a light sensing element, a storage node and a light blocking structure is provided. The light sensing element is disposed in the substrate. The storage node is disposed in the substrate, located beside the light sensing element, and coupled to the light sensing element. The light blocking structure is disposed on the substrate, and includes a light shielding structure and a light shielding wall. The light shielding structure covers the storage node, and extends along a direction of the substrate to shield a light toward the storage node. The light shielding wall is connected to the light shielding structure, surrounds the light sensing element, and extends along a direction perpendicular to the substrate, so that a light incident toward the light shielding wall is reflected to the light sensing element. A manufacturing method of image sensor is also provided.

Description

Image sensor and manufacturing method thereof

The present invention relates to an image sensor and a manufacturing method thereof, and in particular, to a global shutter type image sensor and a manufacturing method thereof.

Generally speaking, image sensors can be classified into global shutter (GS) or rolling shutter (Rolling Shutter). The sensing principle of the global shutter type image sensor is to expose all pixels at the same time, and then read out the signals stored in the storage nodes column/row to form an image. Since pixels are exposed simultaneously to form an image, the image produced by the global shutter image sensor does not have the problem of exposure time difference between pixels.

Since the signal is temporarily stored in the storage node, the storage node must be shielded during the production of a global shutter type image sensor to reduce noise. However, the shielding structure on the storage node reflects the incident light to the surrounding pixels, thus causing the problem of signal crosstalk between pixels.

The present invention provides an image sensor and a manufacturing method thereof. The image sensor can effectively reduce the problem of signal crosstalk.

An embodiment of the present invention provides an image sensor, which includes a substrate, a light sensing element, a storage node and a light shielding structure. The light sensing element is arranged in the substrate. The storage node is disposed in the substrate, located next to the light sensing element, and coupled with the light sensing element. The light shielding structure is arranged on the substrate and includes a light shielding structure and a light shielding wall. The light shielding structure covers the storage node and extends along a direction parallel to the substrate to shield light toward the storage node. The light-shielding wall is connected to the light-shielding structure, surrounds the light-sensing element and extends along the direction perpendicular to the substrate, so that the light incident toward the light-shielding wall is reflected to the light-sensing element.

An embodiment of the present invention provides a manufacturing method of an image sensor, which includes the following steps. Light sensing elements and storage nodes are formed in the substrate. A first interlayer dielectric layer is formed on the substrate. A patterned first photoresist layer is formed on the first inter-sublayer dielectric layer. An etching process is performed to form an etched first interlayer dielectric layer. The first photoresist layer is removed, and a sub-light shielding structure is formed. A second photoresist layer is formed on the sub-light shielding structure. A first planarization process is performed to remove part of the sub-light shielding structure covering the light sensing element to form a light shielding structure.

Based on the above, in an image sensor and a manufacturing method thereof according to an embodiment of the present invention, a light shielding structure including a light shielding structure and a light shielding wall is formed on a storage node. The light-shielding wall surrounds the light-sensing element and extends along the direction perpendicular to the substrate, so that the light incident toward the light-shielding wall is reflected to the light-sensing element. Therefore, the image sensor can effectively reduce the problem of signal crosstalk and simultaneously improve the image sensor. quantum efficiency.

1A and 1B are respectively a schematic diagram and a top view of a storage gate type image sensor according to the first embodiment of the present invention. Referring to FIGS. 1A and 1B , an embodiment of the present invention provides an image sensor 10 and a manufacturing method thereof. The image sensor 10 includes a substrate 100, a light sensing element 200, a storage node 300 and a light shielding structure 400. The substrate 100 is, for example, a semiconductor substrate. The light sensing element 200 is, for example, a photodiode. The light shielding structure 400 may be made of metal, such as tungsten, aluminum, titanium, tantalum, copper, etc.

In detail, in this embodiment, the light sensing element 200 is disposed in the substrate 100 . The storage node 300 is disposed in the substrate 100, is located next to the light sensing element 200, and is coupled with the light sensing element 200. The light shielding structure 400 is disposed on the substrate 100 and includes a light shielding structure 410 and a light shielding wall 420 . The light shielding structure 410 covers the storage node 300 and extends in a direction parallel to the substrate 100 to shield the light L1 toward the storage node 300 . The light-shielding wall 420 is connected to the light-shielding structure 410 , surrounds the light-sensing element 200 and extends along the direction perpendicular to the substrate 100 , so that the light L2 incident toward the light-shielding wall 420 is reflected to the light-sensing element 200 . The light-shielding wall 420 surrounds the light sensing element 200 to form an opening O so that the light sensing element 200 is exposed.

In this embodiment, the light shielding structure 410 and the light shielding wall 420 are integrally formed. For example, the light shielding structure 410 and the light shielding wall 420 are formed in the same process, as shown in FIGS. 3C to 3F.

In this embodiment, the image sensor 10 further includes a storage gate 500 . The storage gate 500 is provided on the storage node 300 . The storage node 300 is coupled to the light sensing element 200 through the storage gate 500 . The light shielding structure 410 covers both the storage gate 500 and the storage node 300 .

In this embodiment, in the direction D1 of the substrate 100 toward the storage gate 500, the height t1 of the light-shielding wall 420 is greater than the height t2 of the storage gate 500. Therefore, the problem of signal crosstalk is better avoided, so that the light L2 can be The efficiency of absorption by the sensing element 200 is improved.

In this embodiment, the image sensor 10 further includes a first interlayer dielectric (ILD) layer 600 and an interconnect structure 700 . The material of the first interlayer dielectric layer 600 may be an oxide, such as silicon oxide. The material of the interconnect structure 700 may be metal. The first interlayer dielectric layer 600 is disposed on the substrate 100 , wherein the light shielding structure 400 is disposed within the first interlayer dielectric layer 600 . The interconnect structure 700 is disposed on the first interlayer dielectric layer 600 , where the first interlayer dielectric layer 600 is located between the substrate 100 and the interconnect structure 700 .

In this embodiment, the shortest distance d between the end of the light-shielding wall 420 away from the substrate 100 and the interconnection structure 700 falls within the range of 0.05 microns (μm) to 0.1 μm. That is to say, the light-shielding wall 420 is brought close to the interconnect structure 700 to shorten the distance d between the two, thereby better avoiding the problem of signal crosstalk and improving the efficiency of light L2 being absorbed by the light sensing element 200 .

In this embodiment, the image sensor 10 further includes a contact etch stop layer (CESL) 12 and a spacer 14 . The contact etch stop layer 12 is located between the substrate 100 and the first interlayer dielectric layer 600 , and the contact etch stop layer 12 is located between the storage gate 500 and the first interlayer dielectric layer 600 . In addition, the spacer 14 is located between the storage gate 500 and the contact etch stop layer 12 .

In this embodiment, the image sensor 10 further includes a transfer gate 1200 and a floating diffusion layer 1300. The transfer gate 1200 is located next to the storage node 300 and is disposed between the storage node 300 and the floating diffusion layer 1300 . Among them, the light sensing element 200 absorbs the light L2 and converts the light energy into charges, and the charges are sequentially transferred from the storage gate 500, the storage node 300, and the transfer gate 1200 to the floating diffusion layer 1300.

FIG. 2 is a flow chart of a manufacturing method of an image sensor according to an embodiment of the present invention. 3A to 3G illustrate a schematic diagram of the manufacturing process of the image sensor of FIG. 1A.

Please refer to FIG. 2 and FIG. 3A to FIG. 3G. The manufacturing method of the image sensor 10 according to the embodiment of the present invention includes the following steps. Step S100 to step S200: Form the light sensing element 200 and the storage node 300 in the substrate 100, and then form the first inter-layer dielectric layer 20 on the substrate 100, as shown in FIG. 3A. Step S300 to step S400: Form a patterned first photoresist layer 30 on the first inter-layer dielectric layer 20, and then perform an etching process to form the etched first inter-layer dielectric layer 20', as shown in FIG. 3B shown. Step S500: Remove the first photoresist layer 30, and form a sub-light shielding structure 400', as shown in Figure 3C. Step S600: Form a second photoresist layer 40 on the sub-light shielding structure 400', as shown in Figure 3D. Step S700: Perform a first flattening process to remove part of the sub-light shielding structure covering the light sensing element 200 to form the light shielding structure 400 (while forming the planarized second inter-layer dielectric layer 20' ''), as shown in Figure 3E.

In this embodiment, the material of the first interlayer dielectric layer 20 may be an oxide, such as silicon oxide.

In this embodiment, the contact etch stop layer 12 is formed on the substrate 100 before forming the first interlayer dielectric layer 20 in the above step S200, as shown in FIG. 3A. The etching process in step S400 uses the first photoresist layer 30 as a mask to remove part of the first inter-layer dielectric layer 20 and stops contacting the etching stop layer 12 .

In this embodiment, after the first photoresist layer 30 is removed in step S500, a second interlayer dielectric layer is formed on the etched first interlayer dielectric layer 20' and the contact etch stop layer 12. 20'', then a sub-light shielding structure 400' is formed on the second sub-layer dielectric layer 20'', as shown in FIGS. 3B to 3C. The second inter-layer dielectric layer 20 ″ is formed by, for example, depositing the same material as the first inter-layer dielectric layer 20 using a deposition process.

In this embodiment, the manufacturing method of the image sensor 10 further includes the following steps. The planarized second photoresist layer 40' is removed, as shown in Figures 3E to 3F. Next, a deposition process is performed and then a second planarization process is performed to form an interlayer dielectric layer 600, as shown in FIGS. 3F to 3G. In FIG. 3G , the same material as the first interlayer dielectric layer 20 can be deposited on the structure of FIG. 3F to form the interlayer dielectric layer 600 .

In this embodiment, the manufacturing method of the image sensor 10 further includes the following steps. An interconnect structure 700 is formed on the interlayer dielectric layer 600, as shown in FIGS. 3G to 1A. Wherein, the shortest distance d between the light shielding structure 400 and the interconnection structure 700 in the direction perpendicular to the substrate 100 falls within the range of 0.05 microns to 0.1 microns.

Based on the above, in the image sensor 10 and its manufacturing method according to an embodiment of the present invention, the light shielding structure 400 including the light shielding structure 410 and the light shielding wall 420 is formed on the storage node 300. The light shielding structure 410 can shield the light L1 directed toward the storage node 300, thereby reducing the system noise of the image sensor 10 and improving the signal-to-noise ratio (SNR). The light-shielding wall 420 surrounds the light-sensing element 200, so that the light L2 incident on the light-shielding wall 420 is reflected to the light-sensing element 200. Therefore, the problem of signal crosstalk is better avoided and the light L2 can be absorbed by the light-sensing element 200 more efficiently. Improve, and at the same time improve the quantum efficiency (QE) of the image sensor 10 .

In addition, since the light-shielding structure 410 and the light-shielding wall 420 are integrally formed, in addition to reducing the manufacturing steps in the process and thus reducing the cost, the connection between the light-shielding structure 410 and the light-shielding wall 420 is smoother, and also improves the The quantum efficiency of the image sensor 10 is improved.

4A and 4B are respectively a schematic diagram and a top view of a storage node type image sensor according to a second embodiment of the present invention. Please refer to FIG. 4A and FIG. 4B. The image sensor 10A of this embodiment is similar to the image sensor 10 of FIG. 1A. The main difference is that the image sensor 10A further includes another transfer gate 800 instead of the image sensor 10 of FIG. 1A storage gate 500. The storage node 300 is coupled to the light sensing element 200 through the transfer gate 800 . The light shielding structure 410 covers both the transfer gate 800 and the storage node 300 .

In this embodiment, in the direction D2 from the substrate 100 to the transfer gate 800, the height t1 of the light-shielding wall 420 is greater than the height t3 of the transfer gate 800. Therefore, the problem of signal crosstalk is better avoided, so that the light L2 can be The efficiency of absorption by the sensing element 200 is improved. The remaining advantages of the image sensor 10A of this embodiment are similar to the image sensor 10 of FIG. 1A and will not be described again here.

FIG. 5 is a schematic diagram of an image sensor according to a third embodiment of the invention. Please refer to FIG. 5 . The image sensor 10B of this embodiment is similar to the image sensor 10 of FIG. 1A . The main differences are as follows. The image sensor 10B further includes a second interlayer dielectric layer 900, a filter layer 1000 and a microlens layer 1100. The second interlayer dielectric layer 900 is disposed on the first interlayer dielectric layer 600 , wherein the first interlayer dielectric layer 600 is located between the second interlayer dielectric layer 900 and the substrate 100 , and the second interlayer dielectric layer 900 The material of may be the same as the first interlayer dielectric layer 600 . The interconnect structure 700 is disposed in the second interlayer dielectric layer 900 . The filter layer 1000 is disposed on the second interlayer dielectric layer 900. The microlens layer 1100 is disposed on the filter layer 1000 , where the filter layer 1000 is located between the second interlayer dielectric layer 900 and the microlens layer 1100 . The advantages of the image sensor 10B of this embodiment are similar to those of the image sensor 10 of FIG. 1A , and will not be described again here.

In summary, in an image sensor and a manufacturing method thereof according to an embodiment of the present invention, a light shielding structure including a light shielding structure and a light shielding wall is formed on a storage node. The light-shielding wall surrounds the light-sensing element, so that the light incident on the light-shielding wall is reflected to the light-sensing element, thereby better avoiding the problem of signal crosstalk, increasing the efficiency of light energy being absorbed by the light-sensing element, and simultaneously improving the image quality. The quantum efficiency of the detector.

10, 10A, 10B: Image sensor 12: Contact etch stop layer 14: spacer 20, 20’: first interlayer dielectric layer 20’’, 20’’’: second sub-layer dielectric layer 30: First photoresist layer 40, 40’: Second photoresist layer 100:Substrate 200:Light sensing element 300:Storage node 400:Light shielding structure 400’: Sub-light shielding structure 410:Light shielding structure 420:Light-shading wall 500: Storage gate 600, 900: Interlayer dielectric layer 700: Internal wiring structure 800, 1200: transfer gate 1000: filter layer 1100: Microlens layer 1300: Floating diffusion layer d: distance D1, D2: direction L1, L2: light O: Open your mouth S100, S200, S300, S400, S500, S600, S700: Steps t1, t2: height

1A and 1B are respectively a schematic diagram and a top view of a storage gate image sensor according to the first embodiment of the present invention. FIG. 2 is a flow chart of a manufacturing method of an image sensor according to an embodiment of the present invention. 3A to 3G illustrate a schematic diagram of the manufacturing process of the image sensor of FIG. 1A. 4A and 4B are respectively a schematic diagram and a top view of a storage node image sensor according to a second embodiment of the present invention. FIG. 5 is a schematic diagram of an image sensor according to a third embodiment of the invention.

10:Image sensor

12: Contact etch stop layer

14: spacer

100:Substrate

200:Light sensing element

300:Storage node

400:Light shielding structure

410:Light shielding structure

420:Light-shading wall

500: Storage gate

600: Interlayer dielectric layer

700: Internal wiring structure

d: distance

D1: direction

L1, L2: light

O: Open your mouth

t1, t2: height

Claims (5)

A method of manufacturing an image sensor, including: forming a light sensing element and a storage node in a substrate; forming a first inter-sub-layer dielectric layer on the substrate; and forming a first inter-sub-layer dielectric layer on the substrate. Form a patterned first photoresist layer; perform an etching process to form the etched first interlayer dielectric layer; remove the first photoresist layer, and form a sub-light shielding structure; in the sub-layer dielectric layer A second photoresist layer is formed on the light shielding structure; and a first planarization process is performed to remove a portion of the sub-light shielding structure covering the light sensing element to form a light shielding structure. The manufacturing method of an image sensor as claimed in claim 1, wherein a contact etch stop layer is formed on the substrate before forming the first interlayer dielectric layer, and the etching process uses the first photoresist layer as a The mask removes portions of the first interlayer dielectric layer and stops at the contact etch stop layer. The manufacturing method of an image sensor as claimed in claim 2, wherein after removing the first photoresist layer, a layer is formed on the etched first inter-sub-layer dielectric layer and the contact etch stop layer. The second inter-layer dielectric layer is then formed on the second inter-layer dielectric layer. The manufacturing method of the image sensor as described in claim 1 further includes: removing the planarized second photoresist layer; and performing a deposition process and then a second planarization process to form a layer between layers. dielectric layer. The manufacturing method of an image sensor as claimed in claim 4, further comprising: forming an interconnect structure on the interlayer dielectric layer, wherein the light shielding structure and the interconnect structure are in a direction perpendicular to the substrate. The shortest distance falls in the range of 0.05 micron to 0.1 micron.

Images