Raster Structure of a Back-Illuminated Image Sensor and Method for Manufacturing the Same

Abstract

The present invention provides a grid structure of a back-illuminated image sensor and a manufacturing method thereof. By removing a stop layer, a barrier layer, and a metal layer formed on the back surface of a substrate when filling through holes or trenches, and reforming a new barrier layer and a new metal layer, and using the new barrier layer as a stop layer for etching the new metal layer in subsequent steps, it not only ensures etching uniformity but also reduces the distance from the bottom of the metal layer in the formed grid structure to the back surface of the substrate, thereby improving the anti-optical crosstalk performance of the grid structure and improving the imaging quality of the back-illuminated image sensor.

Description

Technical Field

[0001] The present invention relates to the field of image sensors, and particularly to a grid structure of a back-illuminated image sensor and a manufacturing method thereof. Background Art

[0002] As a device unit for converting optical signals into digital electrical signals, CMOS image sensors are widely used in various emerging fields such as smart phones, tablet computers, automobiles, and medical applications. A typical image sensor converts incident photons into electrons or holes through a pixel array. When an integration period is completed, the collected charges are converted into digital signals through analog and digital circuits and transmitted to the output terminal of the sensor.

[0003] Traditional image sensors use front-illuminated incidence. That is, for incident photons to reach the photodiode and be successfully absorbed, they need to pass through an optical path channel composed of multiple dielectric layers and / or a metal interconnection layer. At the same time, some incident photons will be reflected by the interface of the metal interconnection layer and bounce back into the air or even crosstalk to other pixel units, resulting in a decrease in the sensitivity of the image sensor and / or color distortion.

[0004] With the continuous development of image sensor technology, the pixel unit size has been reduced from 1.75 μm to 1.12 μm or even lower. The optical path channel of the dielectric layer that photons need to pass through will be reduced synchronously, resulting in serious deterioration of performance such as sensitivity and low-light performance. At this time, the back-illuminated image sensor can fundamentally solve the above problems due to its unique structure. In a back-illuminated image sensor, incident photons enter from the back of the image sensor. On the one hand, it avoids energy loss when passing through the dielectric layer and / or the metal interconnection layer. On the other hand, there is no need to balance the area ratio of the photodiode and the metal interconnection layer, which facilitates device design, thereby significantly improving the performance of the image sensor such as sensitivity and low-light performance.

[0005] In current back-illuminated image sensors, a grid structure capable of reflecting light is usually provided on the back surface (i.e., the light incident surface) of the semiconductor substrate to reduce the optical crosstalk between adjacent pixel units in the image sensor and improve the imaging quality of the image sensor.

[0006] The grid structure generally adopts a composite structure including an insulating layer and a metal layer. From the perspective of optical simulation and the actual performance of the product, the closer the metal layer in the grid structure is to the back surface of the substrate, the better the anti-optical crosstalk performance. On the contrary, the farther the metal layer is from the back surface of the substrate, the worse the anti-optical crosstalk performance.

[0007] Figures 1-3The present invention shows a method for manufacturing a grid structure of a back-illuminated image sensor in the prior art, wherein light is incident from above, that is, the upper surface of the semiconductor substrate 100 is the back surface, and the lower surface is the front surface. A metal interconnection structure 101 is formed on the front surface of the substrate 100, and a metal layer 107 is formed on the back surface of the substrate 100. The metal layer 107 is used to form a back metal trace or pad. A through hole or groove 105 passes through the substrate 100 and is used to connect the metal interconnection structure 101 located on the front surface of the substrate 100 with the metal trace or pad structure located on the back surface of the substrate 100. When the through hole or groove 105 is formed, the metal interconnection structure 101 is formed on the back surface of the substrate 100. When the trench 105 is deep, a barrier layer 106 and a metal layer 107 are generally formed by chemical vapor deposition to ensure good filling capacity. However, due to the characteristics of chemical vapor deposition, the surface of the formed metal layer 107 has problems of consistency and roughness. Therefore, when etching the metal layer 107 to form the grid structure 109, there is an inconsistency in etching speed, which leads to the problem of height difference of the grid structure 109. Therefore, it is necessary to preset a stop layer 103 in the insulating layers 102 and 104 under the metal layer 107 to ensure etching uniformity. However, due to the existence of the stop layer 103, the thickness of the insulating layers 102 and 104 under the metal layer 107 is relatively large, and the distance between the bottom of the metal layer 107 and the back of the substrate 100 is correspondingly increased, so that the anti-optical crosstalk performance of the grid structure 109 is limited, thereby affecting the imaging quality of the image sensor. Summary of the invention

[0008] The object of the present invention is to provide a grid structure of a back-illuminated image sensor and a manufacturing method thereof, so as to improve the anti-optical crosstalk performance of the grid structure and the imaging quality of the back-illuminated image sensor.

[0009] Based on the above considerations, one aspect of the present invention provides a method for manufacturing a grid structure of a back-illuminated image sensor, comprising: forming a through hole or a groove on the back side of a semiconductor substrate for connecting to the front side of the substrate; removing the first stop layer, the first barrier layer and the first metal layer formed on the back side of the substrate when filling the through hole or the groove; forming a second barrier layer and a second metal layer on the back side of the substrate, and using the second barrier layer as a second stop layer for subsequent etching of the second metal layer to reduce the distance from the bottom of the second metal layer in the formed grid structure to the back side of the substrate, thereby improving the anti-optical crosstalk performance of the grid structure.

[0010] Preferably, when the back side of the substrate is covered with a high dielectric constant dielectric layer, the distance from the second metal layer to the high dielectric constant dielectric layer is less than 150nm; when the back side of the substrate is not covered with a high dielectric constant dielectric layer, the distance from the second metal layer to the back side of the substrate is less than 150nm.

[0011] Preferably, a semiconductor substrate having a front side and a back side is provided; a front-side process of the image sensor is completed to form a metal interconnect structure; vias or trenches are formed on the back side of the substrate to expose a part of the metal interconnect structure formed by the front-side process, and a first insulating layer, a first stop layer, and a second insulating layer are formed on the back side of the substrate; a first barrier layer and a first metal layer are formed in the vias or trenches and on the back side of the substrate, and the first metal layer in the vias or trenches is electrically connected to the metal interconnect structure on the front side of the substrate; the first metal layer, the first barrier layer, and the second insulating layer on the back side of the substrate are sequentially removed, stopping at the first stop layer; the first stop layer is removed, stopping at the first insulating layer; a second barrier layer, a second metal layer, and a third insulating layer are sequentially formed on the back side of the substrate; the third insulating layer, the second metal layer, and the second barrier layer are etched to form a grid structure, wherein the second barrier layer serves as a second stop layer for etching the second metal layer.

[0012] Preferably, the etching selectivity of the second metal layer relative to the second barrier layer is greater than 5:1, and the etching selectivity of the second barrier layer relative to the first insulating layer is greater than 5:1.

[0013] Preferably, the material of the second barrier layer is any one or a combination of titanium, titanium nitride, tantalum, and tantalum nitride.

[0014] Preferably, the second barrier layer is formed by physical vapor deposition or chemical vapor deposition.

[0015] Preferably, the method for manufacturing the grid structure of the back-illuminated image sensor further includes forming a hard mask layer on the third insulating layer, and the hard mask layer serves as a part of the grid structure.

[0016] Preferably, the first metal layer, the first barrier layer, the second insulating layer, and the first stop layer are removed by dry etching.

[0017] Preferably, the first barrier layer is formed by chemical vapor deposition.

[0018] Preferably, the material of the first stop layer is silicon nitride, silicon oxynitride, or silicon carbonitride.

[0019] Preferably, the materials of the first metal layer and the second metal layer are tungsten or aluminum.

[0020] Preferably, the materials of the first insulating layer, the second insulating layer, and the third insulating layer are silicon oxide or silicon oxynitride.

[0021] Preferably, the vias or trenches are stepped vias or stepped trenches, and before forming the third insulating layer, a third metal layer is formed on the second metal layer in the stepped vias or stepped trenches, and the material of the third metal layer is aluminum.

[0022] Another aspect of the present invention provides a grid structure for a back-illuminated image sensor. The grid structure located on the back of the semiconductor substrate sequentially includes a second barrier layer, a second metal layer, and a third insulating layer from bottom to top. When a high-k dielectric layer covers the back of the substrate, the distance from the second metal layer to the high-k dielectric layer is less than 150 nm. When the back of the substrate is not covered with a high-k dielectric layer, the distance from the second metal layer to the back of the substrate is less than 150 nm.

[0023] Preferably, the material of the second barrier layer is any one or a combination of titanium, titanium nitride, tantalum, and tantalum nitride.

[0024] Preferably, the grid structure of the back-illuminated image sensor further includes a hard mask layer located on the third insulating layer.

[0025] The grid structure of the back-illuminated image sensor of the present invention and its manufacturing method remove the stop layer, barrier layer, and metal layer formed on the back of the substrate when filling vias or trenches, and then form a new barrier layer and a new metal layer again. Using the new barrier layer as the stop layer for etching the new metal layer in subsequent steps not only ensures etching uniformity but also reduces the distance from the bottom of the metal layer in the formed grid structure to the back of the substrate, thereby improving the anti-optical crosstalk performance of the grid structure and improving the imaging quality of the back-illuminated image sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features, objects, and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0027] Figures 1-3 FIG. is a process schematic diagram of a manufacturing method of a grid structure of a back-illuminated image sensor in the prior art;

[0028] Figures 4-9 FIG. is a process schematic diagram of a manufacturing method of a grid structure of a back-illuminated image sensor according to Embodiment 1 of the present invention;

[0029] Figures 10-16 FIG. is a process schematic diagram of a manufacturing method of a grid structure of a back-illuminated image sensor according to Embodiment 2 of the present invention.

[0030] In the figures, throughout the different views, the same or similar reference numerals denote the same or similar devices (modules) or steps. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] To solve the problems in the above-mentioned prior art, the present invention provides a grid structure of a back-illuminated image sensor and a manufacturing method thereof. By removing the stop layer, barrier layer, and metal layer formed on the back surface of the substrate when filling through-holes or trenches, and forming a new barrier layer and a new metal layer again, and using the new barrier layer as the stop layer for etching the new metal layer in subsequent steps, it not only ensures the etching uniformity but also reduces the distance from the bottom of the metal layer in the formed grid structure to the back surface of the substrate, thereby improving the anti-optical crosstalk performance of the grid structure and the imaging quality of the back-illuminated image sensor.

[0032] In the following detailed description of the preferred embodiments, reference will be made to the accompanying drawings which form a part of the present invention. The accompanying drawings illustrate, by way of example, specific embodiments capable of implementing the present invention. The example embodiments are not intended to exhaust all embodiments according to the present invention. It can be understood that other embodiments can be utilized and structural or logical modifications can be made without departing from the scope of the present invention. Therefore, the following detailed description is not restrictive, and the scope of the present invention is defined by the appended claims.

[0033] The present invention provides a manufacturing method of a grid structure of a back-illuminated image sensor, including: forming through-holes or trenches for connecting the front surface of the substrate on the back surface of the semiconductor substrate; removing the first stop layer, the first barrier layer, and the first metal layer formed on the back surface of the substrate when filling the through-holes or trenches; forming a second barrier layer and a second metal layer on the back surface of the substrate, and using the second barrier layer as the second stop layer for etching the second metal layer in subsequent steps to reduce the distance from the bottom of the second metal layer in the formed grid structure to the back surface of the substrate, thereby improving the anti-optical crosstalk performance of the grid structure.

[0034] The following is a detailed elaboration with specific embodiments.

[0035] Embodiment 1

[0036] Figures 4-10 A process schematic diagram showing the manufacturing method of the grid structure of the back-illuminated image sensor according to Embodiment 1 of the present invention is shown.

[0037] See Figure 4, a substrate 200 made of semiconductor material is provided. In the figure, the upper surface of the substrate 200 is the back surface (i.e., the surface where light enters), and the lower surface is the front surface. Preferably, the back surface of the substrate 200 may be covered with a high-k dielectric layer (not shown). The high-k dielectric layer is usually a material with a dielectric constant higher than that of silicon oxide, such as hafnium oxide, aluminum oxide, or tantalum oxide, etc. The front process of the image sensor is completed to form a metal interconnect structure 201. Through holes or trenches 205 are formed on the back surface of the substrate 200 to expose a part of the metal interconnect structure 201 formed by the front process, and a first insulating layer 202, a first stop layer 203, and a second insulating layer 204 are formed on the back surface of the substrate 200. Among them, the materials of the first insulating layer 202 and the second insulating layer 204 are preferably silicon oxide or silicon oxynitride, and the material of the first stop layer 203 is preferably silicon nitride, silicon oxynitride, or silicon carbonitride.

[0038] See Figure 5 , a first barrier layer 206 and a first metal layer 207 are formed in the through holes or trenches 205 and on the back surface of the substrate 200. The first metal layer 207 in the through holes or trenches 205 is electrically connected to the metal interconnect structure 201 on the front surface of the substrate 200. Preferably, the first barrier layer 206 and the first metal layer 207 are formed by chemical vapor deposition to have a good filling ability for the through holes or trenches 205. The material of the first barrier layer 206 is preferably tungsten nitride, and the material of the first metal layer 207 is preferably tungsten or aluminum.

[0039] See Figure 6 , Figure 7 , the first metal layer 207, the first barrier layer 206, and the second insulating layer 204 on the back surface of the substrate 200 are removed in sequence, stopping at the first stop layer 203; the first stop layer 203 is removed, stopping at the first insulating layer 202. Preferably, the first metal layer 207, the first barrier layer 206, the second insulating layer 204, and the first stop layer 203 are removed by dry etching. By providing the first stop layer 203 between the first insulating layer 202 and the second insulating layer 204, the etching uniformity is ensured.

[0040] See Figure 8, a second barrier layer 210, a second metal layer 211, and a third insulating layer 208 are sequentially formed on the back surface of the substrate 200. Preferably, the second barrier layer 210 and the second metal layer 211 are formed by physical vapor deposition or chemical vapor deposition. After the second metal layer 211 is formed, a surface treatment process, such as chemical mechanical polishing, can be selectively added according to the surface roughness condition to improve the surface roughness of the second metal layer 211. Subsequently, backside metal traces or pad structures are formed according to the circuit design, and the third insulating layer 208 is covered on the back surface of the substrate 200. If necessary, chemical mechanical polishing can also be performed on the third insulating layer 208 to further improve the surface roughness. Preferably, the material of the second barrier layer 210 is any one or a combination of titanium, titanium nitride, tantalum, and tantalum nitride; the material of the second metal layer 211 is tungsten or aluminum; and the material of the third insulating layer 208 is silicon oxide or silicon oxynitride.

[0041] In other embodiments, a hard mask layer (not shown) can also be formed on the third insulating layer 208 for consumption during subsequent grid etching and as part of the finally formed grid structure to ensure the final height of the grid structure. The material of the hard mask layer is preferably silicon nitride.

[0042] See Figure 9 , etch the third insulating layer 208, the second metal layer 211, and the second barrier layer 210 to form a grid structure 209. Among them, the second barrier layer 210 serves as the second stop layer for etching the second metal layer 211, that is, first etch the third insulating layer 208 and the second metal layer 211, and stop at the second barrier layer 210; then etch the second barrier layer 210 and stop at the first insulating layer 202. Preferably, the etching selectivity of the second metal layer 211 relative to the second barrier layer 210 is greater than 5:1, and the etching selectivity of the second barrier layer 210 relative to the first insulating layer 202 is greater than 5:1 to better control the etching rate and uniformity.

[0043] In the prior art, the distance D1 from the bottom of the metal layer 107 in the grid structure 109 to the back surface of the substrate 100 is generally about 300 nm. In this embodiment, by removing the first stop layer 203, the first barrier layer 206, and the first metal layer 207 formed on the back surface of the substrate 200 when filling the vias or trenches 205, and forming a second barrier layer 210 and a second metal layer 211 on the back surface of the substrate 200, and using the second barrier layer 210 as the second stop layer for subsequent etching of the second metal layer 211, not only the etching uniformity is ensured, but also the distance D2 from the bottom of the second metal layer 211 in the grid structure 209 to the back surface of the substrate 200 is reduced. Preferably, when the back surface of the substrate 200 is covered with a high-k dielectric layer, the distance from the second metal layer 211 to the high-k dielectric layer is less than 150 nm. When the back surface of the substrate 200 is not covered with a high-k dielectric layer, the distance from the second metal layer 211 to the back surface of the substrate 200 is less than 150 nm, thereby greatly improving the anti-optical crosstalk performance of the grid structure 209 and improving the imaging quality of the back-illuminated image sensor.

[0044] Another aspect of the present invention also provides a grid structure of a back-illuminated image sensor, as Figure 9 shown, the grid structure 209 located on the back surface of the substrate 200 sequentially includes a second barrier layer 210, a second metal layer 211, and a third insulating layer 208 from bottom to top. When the back surface of the substrate 200 is covered with a high-k dielectric layer, the distance from the second metal layer 211 to the high-k dielectric layer is less than 150 nm. When the back surface of the substrate 200 is not covered with a high-k dielectric layer, the distance from the second metal layer 211 to the back surface of the substrate is less than 150 nm.

[0045] Preferably, the material of the second barrier layer 210 is any one or a combination of titanium, titanium nitride, tantalum, and tantalum nitride.

[0046] Preferably, the grid structure 209 further includes a hard mask layer (not shown) located on the third insulating layer 208.

[0047] Embodiment 2

[0048] Figures 10-16 A process schematic diagram showing a manufacturing method of a grid structure of a back-illuminated image sensor according to Embodiment 2 of the present invention.

[0049] See Figure 10, a semiconductor substrate 300 is provided. In the figure, the upper surface of the substrate 300 is the back surface (i.e., the surface where light enters), and the lower surface is the front surface. Preferably, the back surface of the substrate 300 may be covered with a high-k dielectric layer (not shown). The high-k dielectric layer is usually a material with a dielectric constant higher than that of silicon oxide, such as hafnium oxide, aluminum oxide, or tantalum oxide, etc. The front process of the image sensor is completed to form the metal interconnect structure 301. Through holes or trenches 305 are formed on the back surface of the substrate 300 to expose a part of the metal interconnect structure 301 formed by the front process. Different from the first embodiment, the through holes or trenches 305 in this embodiment are stepped. In subsequent processes, back metal traces or pad structures can be formed in the stepped through holes or trenches 305 to reduce the height difference on the back surface of the substrate and reduce the influence on the morphology of the color filters and microlenses at the edge of the pixel array in subsequent processes. Similar to the first embodiment, a first insulating layer 302, a first stop layer 303, and a second insulating layer 304 are formed on the back surface of the substrate 300. Among them, the materials of the first insulating layer 302 and the second insulating layer 304 are preferably silicon oxide or silicon oxynitride, and the material of the first stop layer 303 is preferably silicon nitride, silicon oxynitride, or silicon carbonitride.

[0050] See Figure 11 , a first barrier layer 306 and a first metal layer 307 are formed in the through holes or trenches 305 and on the back surface of the substrate 300. The first metal layer 307 in the through holes or trenches 305 is electrically connected to the metal interconnect structure 301 on the front surface of the substrate 300. Preferably, the first barrier layer 306 and the first metal layer 307 are formed by chemical vapor deposition to have a good filling ability for the through holes or trenches 305. The material of the first barrier layer 306 is preferably tungsten nitride, and the material of the first metal layer 307 is preferably tungsten or aluminum.

[0051] See Figure 12 , Figure 13 , the first metal layer 307, the first barrier layer 306, and the second insulating layer 304 on the back surface of the substrate 300 are sequentially removed, stopping at the first stop layer 303; the first stop layer 303 is removed, stopping at the first insulating layer 302. Preferably, the first metal layer 307, the first barrier layer 306, the second insulating layer 304, and the first stop layer 303 are removed by dry etching. By providing the first stop layer 303 between the first insulating layer 302 and the second insulating layer 304, the etching uniformity is ensured.

[0052] See Figure 14 , Figure 15, a second barrier layer 310 and a second metal layer 311 are sequentially formed on the back surface of the substrate 300. Preferably, the second barrier layer 310 and the second metal layer 311 are formed by physical vapor deposition or chemical vapor deposition. After the second metal layer 311 is formed, a surface treatment process, such as chemical mechanical polishing, can be selectively added according to the surface roughness condition to improve the surface roughness of the second metal layer 311. Subsequently, back metal traces or pad structures are formed according to the circuit design. For example, a third metal layer 313 can be formed on the second metal layer 311 in the stepped vias or trenches 305 as the back metal traces or pad structures. Since the metal traces or pad structures are accommodated in the stepped vias or trenches 305, the height difference on the back surface of the substrate 300 can be reduced, and the influence on the morphology of the color filters and microlenses at the edge of the pixel array in the subsequent process can be minimized. Subsequently, a third insulating layer 308 is covered on the back surface of the substrate 300. If necessary, chemical mechanical polishing can also be performed on the third insulating layer 308 to further improve the surface roughness. Preferably, the material of the second barrier layer 310 is any one or a combination of titanium, titanium nitride, tantalum, and tantalum nitride; the material of the second metal layer 311 is tungsten or aluminum; the material of the third metal layer 313 is generally aluminum; and the material of the third insulating layer 308 is silicon oxide or silicon oxynitride.

[0053] In other embodiments, a hard mask layer (not shown) can be further formed on the third insulating layer 308 for consumption during the subsequent grid etching process and as part of the finally formed grid structure to ensure the final height of the grid structure. The material of the hard mask layer is preferably silicon nitride.

[0054] See Figure 16 , the third insulating layer 308, the second metal layer 311, and the second barrier layer 310 are etched to form a grid structure 309. Among them, the second barrier layer 310 serves as the second stop layer for etching the second metal layer 311, that is, first, the third insulating layer 308 and the second metal layer 311 are etched and stopped at the second barrier layer 310; then, the second barrier layer 310 is etched and stopped at the first insulating layer 302. Preferably, the etching selectivity of the second metal layer 311 relative to the second barrier layer 310 is greater than 5:1, and the etching selectivity of the second barrier layer 310 relative to the first insulating layer 302 is greater than 5:1 to better control the etching rate and uniformity.

[0055] In the prior art, the distance D1 from the bottom of the metal layer 107 in the grid structure 109 to the back surface of the substrate 100 is generally about 300 nm. In this embodiment, by removing the first stop layer 303, the first barrier layer 306, and the first metal layer 307 formed on the back surface of the substrate 300 when filling the stepped through holes or trenches 305, and forming a second barrier layer 310 and a second metal layer 311 on the back surface of the substrate 300, and using the second barrier layer 310 as the second stop layer for etching the second metal layer 311 in subsequent steps, both the etching uniformity is ensured and the distance D3 from the bottom of the second metal layer 311 in the grid structure 309 to the back surface of the substrate 300 is reduced. Preferably, when the back surface of the substrate 300 is covered with a high-k dielectric layer, the distance from the second metal layer 311 to the high-k dielectric layer is less than 150 nm. When the back surface of the substrate 300 is not covered with a high-k dielectric layer, the distance from the second metal layer 311 to the back surface of the substrate 300 is less than 150 nm. Thereby, the anti-optical crosstalk performance of the grid structure 309 is greatly improved, and the imaging quality of the back-illuminated image sensor is improved.

[0056] Another aspect of the present invention also provides a grid structure of a back-illuminated image sensor, as Figure 16 shown. The grid structure 309 located on the back surface of the semiconductor substrate 300 sequentially includes a second barrier layer 310, a second metal layer 311, and a third insulating layer 308 from bottom to top. When the back surface of the substrate 300 is covered with a high-k dielectric layer, the distance from the second metal layer 311 to the high-k dielectric layer is less than 150 nm. When the back surface of the substrate 300 is not covered with a high-k dielectric layer, the distance from the second metal layer 311 to the back surface of the substrate is less than 150 nm.

[0057] Preferably, the material of the second barrier layer 310 is any one or a combination of titanium, titanium nitride, tantalum, and tantalum nitride.

[0058] Preferably, the grid structure 309 further includes a hard mask layer (not shown) located on the third insulating layer 308.

[0059] In summary, for the grid structure of the back-illuminated image sensor and its manufacturing method of the present invention, by removing the stop layer, the barrier layer, and the metal layer formed on the back surface of the substrate when filling the through holes or trenches, and forming a new barrier layer and a new metal layer again, and using the new barrier layer as the stop layer for etching the new metal layer in subsequent steps, both the etching uniformity is ensured and the distance from the bottom of the metal layer in the formed grid structure to the back surface of the substrate is reduced. Thereby, the anti-optical crosstalk performance of the grid structure is improved, and the imaging quality of the back-illuminated image sensor is improved.

[0060] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, in any case, the embodiments should be regarded as exemplary and non-limiting. In addition, obviously, the word "including" does not exclude other elements and steps, and the wording "a" does not exclude a plurality. A plurality of elements recited in the apparatus claims can also be implemented by one element. The words first, second, etc. are used to denote names and do not denote any particular order.

Claims

1. A manufacturing method of a grid structure of a back-illuminated image sensor, characterized in that, Comprising: Providing a semiconductor substrate having a front side and a back side; Completing the front-side process of the image sensor to form a metal interconnect structure; Forming vias or trenches on the back side of the substrate to expose a part of the metal interconnect structure formed by the front-side process, and a first insulating layer, a first stop layer, and a second insulating layer are formed on the back side of the substrate; Forming a first barrier layer and a first metal layer in the vias or trenches and on the back side of the substrate, and the first metal layer in the vias or trenches is electrically connected to the metal interconnect structure on the front side of the substrate; sequentially removing the first metal layer, the first barrier layer, and the second insulating layer on the back side of the substrate, and stopping at the first stop layer; Removing the first stop layer and stopping at the first insulating layer; Sequentially forming a second barrier layer, a second metal layer, and a third insulating layer on the back side of the substrate; Etching the third insulating layer, the second metal layer, and the second barrier layer to form a grid structure, wherein the second barrier layer serves as a second stop layer for etching the second metal layer to reduce the distance from the bottom of the second metal layer in the formed grid structure to the back side of the substrate, thereby improving the anti-optical crosstalk performance of the grid structure.

2. The manufacturing method of the grid structure of the back-illuminated image sensor according to claim 1, characterized in that, When the back side of the substrate is covered with a high-k dielectric layer, the distance from the second metal layer to the high-k dielectric layer is less than 150 nm; when the back side of the substrate is not covered with a high-k dielectric layer, the distance from the second metal layer to the back side of the substrate is less than 150 nm.

3. The manufacturing method of the grid structure of the back-illuminated image sensor according to claim 1, characterized in that, The etching selectivity of the second metal layer relative to the second barrier layer is greater than 5:1, and the etching selectivity of the second barrier layer relative to the first insulating layer is greater than 5:

1.

4. The manufacturing method of the grid structure of the back-illuminated image sensor according to claim 1, wherein, The material of the second barrier layer is any one or a combination of titanium, titanium nitride, tantalum, and tantalum nitride.

5. The manufacturing method of the grid structure of the back-illuminated image sensor according to claim 1, characterized in that, The second barrier layer is formed by physical vapor deposition or chemical vapor deposition.

6. The manufacturing method of the grid structure of the back-illuminated image sensor according to claim 1, characterized in that, Further comprising forming a hard mask layer on the third insulating layer, and the hard mask layer serves as a part of the grid structure.

7. The manufacturing method of the grid structure of the back-illuminated image sensor according to claim 1, wherein, Removing the first metal layer, the first barrier layer, the second insulating layer, and the first stop layer by dry etching.

8. The manufacturing method of the grid structure of the back-illuminated image sensor according to claim 1, characterized in that, Forming the first barrier layer by chemical vapor deposition.

9. The manufacturing method of the grid structure of the back-illuminated image sensor according to claim 1, characterized in that, The material of the first stop layer is silicon nitride, silicon oxynitride, or silicon carbonitride.

10. The manufacturing method of the grid structure of the back-illuminated image sensor according to claim 1, characterized in that, The materials of the first metal layer and the second metal layer are tungsten or aluminum.

11. The manufacturing method of the grid structure of the back-illuminated image sensor according to claim 1, characterized in that, The materials of the first insulating layer, the second insulating layer, and the third insulating layer are silicon oxide or silicon oxynitride.

12. The manufacturing method of the grid structure of the back-illuminated image sensor according to claim 1, wherein The vias or trenches are stepped vias or stepped trenches, and a third metal layer made of aluminum is formed on the second metal layer in the stepped vias or stepped trenches before forming the third insulating layer.

13. A grid structure of a back-illuminated image sensor, characterized in that The grid structure located on the back side of the semiconductor substrate sequentially includes a second barrier layer, a second metal layer, and a third insulating layer from bottom to top. When the back side of the substrate is covered with a high-k dielectric layer, the distance from the second metal layer to the high-k dielectric layer is less than 150 nm; when the back side of the substrate is not covered with a high-k dielectric layer, the distance from the second metal layer to the back side of the substrate is less than 150 nm.

14. The grid structure of the back-illuminated image sensor according to claim 13, characterized in that, The material of the second barrier layer is any one or a combination of titanium, titanium nitride, tantalum, and tantalum nitride.

15. The grid structure of the back-illuminated image sensor according to claim 13, characterized in that, Further comprising a hard mask layer located on the third insulating layer.

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