CN-121985608-A - Image sensor isolation structure forming method and image sensor

Abstract

The invention discloses a method for forming an isolation structure of an image sensor and the image sensor, comprising the steps of S1, providing a substrate, forming a blanket type N-well layer in the substrate, S2, arranging a pixel region, a protection ring region and a peripheral region on the blanket type N-well layer along the same plane, wherein the protection ring region is arranged outside the pixel region in a surrounding manner, the peripheral region is arranged outside the protection ring region in a surrounding manner, S3, etching to form a silicon through hole isolation structure between the peripheral region and the protection ring region and/or between the protection ring region and the pixel region, and the silicon through hole isolation structure penetrates through the blanket type N-well layer and extends to the upper surface of the substrate. The silicon through hole isolation structure isolates the blanket type N well layer into two or more sub-wells, so that transverse leakage paths of electrons migrating between different functional areas through the blanket type N well layer are fundamentally cut off, and electrical isolation or optical isolation between different functional areas is realized while high full well capacity is ensured.

Inventors

• WANG RUIJIA
• ZHENG ZHAN

Assignees

• 格科微电子（上海）有限公司

Dates

Publication Date

20260505

Application Date

20260113

Claims (10)

1. 1. The method for forming the isolation structure of the image sensor is characterized by at least comprising the following steps: step S1, providing a substrate, and forming a blanket type N well layer in the substrate; Step S2, arranging a pixel region, a protection ring region and a peripheral region on the blanket type N well layer along the same plane, wherein the protection ring region is arranged outside the pixel region in a surrounding manner, and the peripheral region is arranged outside the protection ring region in a surrounding manner; And S3, etching to form a silicon through hole isolation structure between the peripheral area and the guard ring area and/or between the guard ring area and the pixel area, wherein the silicon through hole isolation structure penetrates through the blanket type N well layer and extends to the upper surface of the substrate.
2. 2. The method of claim 1, wherein in step S1, the blanket N-well layer is formed by any one of ion implantation and epitaxial growth.
3. 3. The method of claim 1, wherein the upper surface of the substrate is further formed with a shallow trench isolation structure, an interlayer dielectric layer, a metal interconnect layer, the through silicon via isolation structure extending through the blanket N-well layer and to the shallow trench isolation structure, or to the interlayer dielectric layer, or to the metal interconnect layer.
4. 4. The method of claim 3, wherein a depth of the through silicon via isolation structure is equal to or greater than a depth of the substrate or equal to or greater than a difference between the substrate depth and a shallow trench isolation structure depth.
5. 5. The method of claim 1, wherein a layer of insulating material is deposited on sidewall surfaces of the through-silicon via isolation structure for isolation from the substrate.
6. 6. The method of claim 5, wherein an interior of the through silicon via isolation structure is filled with a metal fill layer for metal interconnection, enhanced optical isolation, or thermal isolation.
7. 7. The method of claim 6, wherein the metal fill layer is selected from any one of tungsten, titanium, copper, and aluminum.
8. 8. The method of claim 5, wherein the through-silicon via isolation structure is internally hollow or filled with an insulating material for enhanced light or thermal isolation.
9. 9. The method of claim 1, wherein the blanket N-well layer has a depth of 0.5 μm to 6 μm.
10. 10. An image sensor, characterized in that it is formed by the method of any one of claims 1-9.

Description

Image sensor isolation structure forming method and image sensor Technical Field The present invention relates to the field of image sensors, and in particular, to a method for forming an isolation structure of an image sensor and an image sensor. Background In the field of design and manufacturing of small-pixel image sensors, the full-well capacity of pixels directly determines the dynamic range and image acquisition quality of the image sensor, and improving the full-well capacity of pixels is one of the core requirements for optimizing the performance of devices. In order to improve the full well capacity of the pixel, a blanket type N well layer is generally introduced into a semiconductor substrate in industry, and is generally prepared through high-energy ion implantation, epitaxial growth and other mature processes, and the blanket type N well layer covers the pixel region, the guard ring region, the peripheral region and other functional regions. The blanket type N well layer expands the charge storage area from a local N type area with a shallow junction to a global N type layer with a deep N type area, so that the physical volume of charge storage is remarkably increased, and the uniform doping concentration of the blanket type N well layer forms a wide and gentle potential well, so that charges can be uniformly distributed, and the utilization efficiency of a storage space is greatly improved. Although the blanket type N-well layer can improve the full well capacity, the blanket type N-well layer has the defect that all N-type doped regions (such as an N-type region of a photodiode, an N-type region of a guard ring and an N-type region of a peripheral transistor in a pixel unit) of the same type in the covered region of the blanket type N-well layer form electrical short circuits, so that necessary electrical isolation among the pixel region, the guard ring region and the peripheral region is directly damaged, and various performance hidden hazards are introduced to devices. For example, the blanket N-well layer provides multiple paths for current leakage, severely affecting the performance stability and reliability of the image sensor. One leakage path is that electrons migrate from the heavily doped N-type region of the peripheral region to the PN junction of the protection ring region through the blanket type N-well layer and then enter the P-type region to flow to the heavily doped P-type region, and the standby power consumption of the image sensor can be obviously increased and the energy efficiency of the device can be reduced. The other leakage path is that electrons are directly leaked from the blanket type N well layer to the semiconductor substrate, and the process can increase substrate noise, so that the fixed mode noise of the image sensor is aggravated, the dark current level is increased, and further the problems of impurity points, image quality reduction and the like are caused during image acquisition. Aiming at the defects, the traditional method mostly adopts a Deep Trench Isolation (DTI) structure to carry out structural improvement, but the DTI structure is limited by the etching depth, and when the depth of a blanket type N well layer exceeds the etching depth of the DTI or the semiconductor substrate is of an N type, the DTI still cannot realize effective electrical isolation. The statements herein merely provide background information related to the present disclosure and may not necessarily constitute prior art. Disclosure of Invention The invention aims to isolate a blanket type N well layer into two or more sub-wells by introducing a silicon through hole isolation structure penetrating the blanket type N well layer, so that a transverse leakage path of electrons migrating between different functional areas through the blanket type N well layer is fundamentally cut off, the high full well capacity is ensured, and meanwhile, the true and effective electrical isolation or optical isolation between the different functional areas is realized, thereby optimizing the performance of an image sensor. In order to achieve the above object, the present invention provides a method for forming an isolation structure of an image sensor, at least comprising the following steps: step S1, providing a substrate, and forming a blanket type N well layer in the substrate; Step S2, arranging a pixel region, a protection ring region and a peripheral region on the blanket type N well layer along the same plane, wherein the protection ring region is arranged outside the pixel region in a surrounding manner, and the peripheral region is arranged outside the protection ring region in a surrounding manner; And S3, etching to form a silicon through hole isolation structure between the peripheral area and the guard ring area and/or between the guard ring area and the pixel area, wherein the silicon through hole isolation structure penetrates through the blanket type N well layer and extends to the