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CN-122002934-A - Method for manufacturing back-illuminated image sensor

CN122002934ACN 122002934 ACN122002934 ACN 122002934ACN-122002934-A

Abstract

The invention provides a manufacturing method of a backside illuminated image sensor, which sequentially etches a dielectric layer exposed in a first opening and a substrate at the bottom of the first opening by taking a patterned first photoresist layer as a mask to form a second opening, and etches the dielectric layer of an exposed logic region to form a grounding hole, namely, the second opening (a growth window for forming a metal bonding pad) and the grounding hole are formed in the same etching step, namely, the second opening and the grounding hole can be formed through one mask layer, thereby saving two masks, reducing masks in the forming process of the metal bonding pad and the grounding structure, and further reducing the process cost. Accordingly, the metal pad and the ground structure can be formed in the same process step, thereby reducing the process steps and further reducing the process cost.

Inventors

  • LIU GUANG

Assignees

  • 上海集成电路装备材料产业创新中心有限公司

Dates

Publication Date
20260508
Application Date
20241105

Claims (10)

  1. 1. A method of manufacturing a backside illuminated image sensor, comprising: Providing a substrate, wherein the substrate is provided with an input/output area, a logic area and a pixel area, the logic area is positioned between the input/output area and the pixel area, a metal interconnection structure is formed in the substrate of the input/output area, and a first opening is formed in the substrate of the input/output area and is positioned above the metal interconnection structure; forming a dielectric layer, wherein the dielectric layer covers the side wall and the bottom of the first opening and covers the substrate; forming a patterned first photoresist layer on the dielectric layer, wherein the patterned first photoresist layer exposes the dielectric layer at the bottom of the first opening and part of the dielectric layer on the logic region; Sequentially etching the dielectric layer exposed in the first opening and the substrate at the bottom of the first opening by taking the patterned first photoresist layer as a mask to form a second opening, wherein part of the metal interconnection structure is exposed by the second opening, the dielectric layer of the exposed logic region is etched to form a grounding hole, and part of the substrate of the logic region is exposed by the grounding hole; Removing the patterned first photoresist layer; And forming a metal bonding pad and a grounding structure, wherein the metal bonding pad fills the second opening and part of the first opening and is electrically connected with the metal interconnection structure, and the grounding structure fills the grounding hole and is electrically connected with the substrate.
  2. 2. The method of manufacturing a backside illuminated image sensor according to claim 1, wherein the method of forming the metal pad and the ground structure comprises: sequentially forming a first metal material layer and a second metal material layer, wherein the first metal material layer covers the side wall and the bottom of the first opening, the side wall of the second opening and the side wall and the bottom of the grounding hole, and covers the substrate, and the second metal material layer covers the first metal material layer; Etching the second metal material layer in the first opening to form the metal pad, wherein a space is formed between the side wall of the metal pad and the first metal material layer of the side wall of the first opening, and removing the second metal material layer on the substrate, and reserving the second metal material layer in the grounding hole to form the grounding structure.
  3. 3. The method of manufacturing a backside illuminated image sensor according to claim 2, wherein the method of etching the second metal material layer in the first opening and removing the second metal material layer on the substrate comprises: Forming a patterned second photoresist layer on the second metal material layer, wherein the patterned second photoresist layer exposes a part of the second metal material layer in the first opening and exposes the second metal material layer on the substrate; etching the second metal material layer exposed in the first opening by using the patterned second photoresist layer as a mask and adopting a dry etching process to remove the second metal material layer on the substrate, and And removing the patterned second photoresist layer.
  4. 4. The method of manufacturing a backside illuminated image sensor according to claim 2, wherein the material of the first metal material layer comprises tungsten, the material of the second metal material layer comprises aluminum, and the material of the dielectric layer comprises silicon oxide.
  5. 5. The method of manufacturing a backside illuminated image sensor according to claim 2, wherein after forming the metal pad and the ground structure, the method of manufacturing a backside illuminated image sensor further comprises: etching the first metal material layer on the substrate of the logic region to form a first metal grid, etching the first metal material layer on the substrate of the pixel region to form a second metal grid, and removing the first metal material layer on the substrate of the input/output region, wherein the grounding structure is electrically connected with the substrate through the first metal grid.
  6. 6. The method of manufacturing a backside illuminated image sensor according to claim 5, wherein the method of etching the first metal material layer comprises: Forming a hard mask layer, wherein the hard mask layer covers the first metal material layer, the metal bonding pad and the grounding structure; Forming a patterned third photoresist layer on the hard mask layer, wherein the patterned third photoresist layer exposes a part of the hard mask layer of the pixel region and exposes the hard mask layer on the substrate of the input/output region; etching the hard mask layer by taking the patterned third photoresist layer as a mask to form a patterned hard mask layer, wherein the patterned hard mask layer exposes part of the first metal material layer of the pixel region and exposes the first metal material layer on the substrate of the input/output region; And etching the exposed first metal material layer by using the patterned third photoresist layer and the patterned hard mask layer as masks through a dry etching process to form the first metal grid and the second metal grid, removing the first metal material layer on the substrate of the input/output region, and removing the patterned third photoresist layer.
  7. 7. The method of manufacturing a backside illuminated image sensor according to claim 5 or 6, wherein a deep trench isolation structure is formed in the substrate of the pixel region, the dielectric layer covers the deep trench isolation structure, and the second metal grid is located above the deep trench isolation structure.
  8. 8. The method of manufacturing a backside illuminated image sensor according to claim 6, wherein after forming the first metal grid and the second metal grid, the method of manufacturing a backside illuminated image sensor further comprises: Forming a patterned fourth photoresist layer, wherein the patterned photoresist layer exposes the patterned hard mask layer on the metal pad; Etching the exposed patterned hard mask layer to expose the top surface of the metal pad by using the patterned fourth photoresist layer as a mask, and And removing the patterned fourth photoresist layer.
  9. 9. The method of manufacturing a backside illuminated image sensor according to claim 1, wherein the dielectric layer is etched using a dry etching process.
  10. 10. The method of manufacturing a backside illuminated image sensor according to claim 1, wherein the substrate comprises a support base, an interlayer dielectric layer and a device base stacked in this order from bottom to top, the metal interconnect structure is formed in the interlayer dielectric layer, wherein the device base has a first surface and a second surface disposed opposite to each other, the interlayer dielectric layer is formed on the second surface of the device base, the dielectric layer is formed on the first surface of the device base, and the first opening is formed in and penetrates the device base.

Description

Method for manufacturing back-illuminated image sensor Technical Field The invention relates to the technical field of semiconductors, in particular to a manufacturing method of a back-illuminated image sensor. Background CMOS (Complementary Metal Oxide Semiconductor ) image sensors are further converted into digitized signals by converting optical signals into electrical signals and via readout circuitry. In the conventional backside illuminated image sensor, it is necessary to form a metal pad in the substrate of the input/output area of the backside illuminated image sensor to electrically connect the metal interconnection structure, and form a ground via structure on the substrate of the logic area to electrically connect the metal grid (METAL GRID) with the substrate, thereby realizing the ground. However, in the process of forming the metal pad and the ground via structure, a first mask (mask) is generally used to form a metal pad opening (a growth window for forming the metal pad) in the substrate of the input/output region, then a metal material layer is deposited and etched to form the metal pad in the metal pad opening, then a protective layer (e.g., silicon oxide) is deposited to cover the metal pad and the substrate of the logic region, the thickness difference of the surface of the protective layer is large due to the existence of the metal pad opening, and therefore, the protective layer on the substrate needs to be thinned by using a second mask to facilitate the subsequent chemical mechanical polishing process, then a chemical mechanical polishing process is performed on the protective layer, then a ground hole is formed in the protective layer above the substrate of the logic region by using a third mask, and then the metal material layer is deposited in the ground hole and etched to form the ground structure in the ground hole. In the manufacturing method, three masks are needed to form the metal pad opening and the grounding through hole in the process of forming the metal pad opening and the grounding through hole, so that the process steps are complex and the cost is high. Disclosure of Invention The invention aims to provide a manufacturing method of a backside illuminated image sensor, which is used for reducing masks in the formation process of a metal bonding pad and a grounding structure. In order to achieve the above object, the present invention provides a method for manufacturing a backside illuminated image sensor, comprising: Providing a substrate, wherein the substrate is provided with an input/output area, a logic area and a pixel area, the logic area is positioned between the input/output area and the pixel area, a metal interconnection structure is formed in the substrate of the input/output area, and a first opening is formed in the substrate of the input/output area and is positioned above the metal interconnection structure; forming a dielectric layer, wherein the dielectric layer covers the side wall and the bottom of the first opening and covers the substrate; forming a patterned first photoresist layer on the dielectric layer, wherein the patterned first photoresist layer exposes the dielectric layer at the bottom of the first opening and part of the dielectric layer on the logic region; Sequentially etching the dielectric layer exposed in the first opening and the substrate at the bottom of the first opening by taking the patterned first photoresist layer as a mask to form a second opening, wherein part of the metal interconnection structure is exposed by the second opening, the dielectric layer of the exposed logic region is etched to form a grounding hole, and part of the substrate of the logic region is exposed by the grounding hole; Removing the patterned first photoresist layer; And forming a metal bonding pad and a grounding structure, wherein the metal bonding pad fills the second opening and part of the first opening and is electrically connected with the metal interconnection structure, and the grounding structure fills the grounding hole and is electrically connected with the substrate. Optionally, the method for forming the metal pad and the grounding structure includes: sequentially forming a first metal material layer and a second metal material layer, wherein the first metal material layer covers the side wall and the bottom of the first opening, the side wall of the second opening and the side wall and the bottom of the grounding hole, and covers the substrate, and the second metal material layer covers the first metal material layer; Etching the second metal material layer in the first opening to form the metal pad, wherein a space is formed between the side wall of the metal pad and the first metal material layer of the side wall of the first opening, and removing the second metal material layer on the substrate, and reserving the second metal material layer in the grounding hole to form the grounding structure. Optionally, the method of etching the