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CN-115966581-B - Pixel unit and forming method

CN115966581BCN 115966581 BCN115966581 BCN 115966581BCN-115966581-B

Abstract

The invention discloses a pixel unit and a forming method, wherein the pixel unit comprises a photosensitive part of a second conductivity type arranged in a substrate of a first conductivity type; the semiconductor device comprises a substrate, a first conductive type isolation part arranged on two sides of the substrate, a second conductive type first region arranged on the substrate on the front surface of the photosensitive part, a first conductive type second region arranged on the substrate on the front surface of the photosensitive part and the isolation part, a contact part arranged on the front surface of the first region, and a grid electrode arranged on the front surface of the substrate, wherein the inner side and the outer side of the grid electrode respectively form partial overlapping with the first region and the second region in an up-down position. The invention can adjust the response speed and saturation detection current of the device by applying bias voltages with different magnitudes on the grid electrode, realizes the imaging and detection functions which can take into account high speed and large electron flow, and expands the application range.

Inventors

  • SHI PEI

Assignees

  • 上海集成电路研发中心有限公司

Dates

Publication Date
20260505
Application Date
20221222

Claims (9)

  1. 1. A pixel cell, comprising: A substrate of a first conductivity type; a photosensitive portion of a second conductivity type provided in the substrate; Isolation parts of a first conductivity type in the substrate arranged on two sides of the photosensitive part; a first region of a second conductivity type in the substrate provided on the front surface of the light-sensing portion; a second region of the first conductivity type in the substrate provided on the front surfaces of the photosensitive portion and the isolation portion, and surrounding the side surface of the first region; forming a partially pinned photodiode on a front surface of the substrate between the second region, the photosensitive portion, and the first region; a contact portion provided on the front surface of the first region; And the grid electrode surrounds the outside of the side surface of the contact part and is arranged on the front surface of the substrate, and the inner side and the outer side of the grid electrode are respectively overlapped with the part between the first area and the second area in an up-down position.
  2. 2. The pixel cell of claim 1, wherein the gate is configured to control a potential distribution of the pixel cell across the front surface of the substrate.
  3. 3. The pixel cell according to claim 1, wherein the first region includes a third region and a fourth region, the contact portion is provided on a front surface of the third region, the fourth region surrounds on a side surface and a bottom surface of the third region, a portion overlapping in an up-down position is formed between an inner side of the gate electrode and the fourth region, conductivities of the third region, the fourth region, and the photosensitive portion decrease in order, and conductivities of the second region are higher than conductivities of the isolation portion and the photosensitive portion.
  4. 4. The pixel cell of claim 1, further comprising a dielectric layer disposed on the front surface of the substrate and filling between the contact and the gate electrode, and/or a passivation layer disposed on the back surface of the substrate and on the back surfaces of the photosensitive portion and the spacer portion.
  5. 5. A method for forming a pixel cell, comprising: providing a substrate of a first conductivity type; forming a photosensitive portion of a second conductivity type in the substrate; Forming isolation parts of a first conductivity type in the substrate at two sides of the photosensitive part; Forming a second region of the first conductivity type below the front surface of the substrate, positioning the second region on the front surface of the light-sensing portion and the isolation portion, and forming a window on the front surface of the light-sensing portion by the second region; Forming a ring-shaped grid electrode positioned above the window on the front surface of the substrate, and enabling part of the ring-shaped outer side of the grid electrode and the second region to be overlapped in an upper-lower position; forming a first region of a second conductivity type below the substrate front surface of the annular inner side of the gate electrode, positioning the first region on the photosensitive portion front surface to form a partially pinned photodiode between the second region, the photosensitive portion and the first region, and forming a partial overlap in upper and lower positions between the first region and the annular inner side of the gate electrode; A contact is formed on the first region front surface within the loop shape of the gate.
  6. 6. The method of forming a pixel cell of claim 5, further comprising: Forming a fourth region of a second conductivity type below the front surface of the substrate before forming the second region, so that the fourth region is located on the front surface of the light-sensing portion, and then forming the second region around the outside of the side of the fourth region, so that the second region has the window around the outside of the side of the fourth region; And forming a third region of a second conductivity type located within the ring shape of the gate electrode on the front surface of the fourth region after forming the gate electrode, thereby forming the first region composed of the third region and the fourth region, and forming the contact portion on the front surface of the third region.
  7. 7. The method according to claim 6, wherein the first conductivity type and the second conductivity type are formed by ion implantation, and conductivity of the formed third region, fourth region, and photosensitive portion is sequentially decreased, and conductivity of the second region is higher than conductivity of the isolation portion and the photosensitive portion.
  8. 8. The method of forming a pixel cell according to claim 5, wherein forming a contact portion located within a ring shape of the gate electrode on the front surface of the first region, specifically comprises: Forming a dielectric layer on the front surface of the substrate, covering the grid electrode, and flattening; Forming a via hole with a bottom connected to the front surface of the first region on the front surface of the dielectric layer within the ring shape of the gate; And filling conductive materials in the through holes to form the contact parts.
  9. 9. The method of forming a pixel cell of claim 5, further comprising: thinning the back surface of the substrate to expose the back surfaces of the photosensitive part and the isolation part; and forming a passivation layer on the back surface of the thinned substrate, wherein the passivation layer is positioned on the back surfaces of the photosensitive part and the isolation part.

Description

Pixel unit and forming method Technical Field The present invention relates to the field of semiconductor integrated circuit technology, and more particularly, to a pixel unit and a forming method thereof. Background The silicon-based photodiode can be used for detecting and imaging low-energy secondary electron flows of 1-10 keV, for example, so as to be used in the fields of scanning electron microscopy and the like. At present, the existing pixel unit based on the silicon-based partially pinned photodiode has the advantages of low cost, convenient integration and the like, but has the problems of response speed and maximum electron current intensity detection in the practical device design, so that the application range of the device is limited. Disclosure of Invention The present invention is directed to overcoming the above-mentioned drawbacks of the prior art and providing a pixel unit and a forming method thereof. In order to achieve the above purpose, the technical scheme of the invention is as follows: the present invention provides a pixel unit including: A substrate of a first conductivity type; a photosensitive portion of a second conductivity type provided in the substrate; Isolation parts of a first conductivity type in the substrate arranged on two sides of the photosensitive part; a first region of a second conductivity type in the substrate provided on the front surface of the light-sensing portion; A second region of the first conductivity type in the substrate provided on the front surfaces of the photosensitive portion and the isolation portion, and surrounding the side surface of the first region; a contact portion provided on the front surface of the first region; And the grid electrode surrounds the outside of the side surface of the contact part and is arranged on the front surface of the substrate, and the inner side and the outer side of the grid electrode are respectively overlapped with the part between the first area and the second area in an up-down position. Further, a partially pinned photodiode is formed on a front surface of the substrate between the second region, the photosensitive portion, and the first region. Further, the gate is used to control the potential distribution of the pixel cell over the front surface of the substrate. Further, the first region includes a third region and a fourth region, the contact portion is disposed on the front surface of the third region, the fourth region surrounds the side surface and the bottom surface of the third region, a partial overlap is formed between the inner side of the gate and the fourth region in an up-down position, the conductivities of the third region, the fourth region and the photosensitive portion decrease in sequence, and the conductivities of the second region are higher than the conductivities of the isolation portion and the photosensitive portion. Further, the semiconductor device further comprises a dielectric layer which is arranged on the front surface of the substrate and is filled between the contact part and the grid electrode, and/or a passivation layer which is arranged on the back surface of the substrate and is positioned on the back surfaces of the photosensitive part and the isolation part. The invention also provides a pixel unit forming method, which comprises the following steps: providing a substrate of a first conductivity type; forming a photosensitive portion of a second conductivity type in the substrate; Forming isolation parts of a first conductivity type in the substrate at two sides of the photosensitive part; Forming a second region of the first conductivity type below the front surface of the substrate, positioning the second region on the front surface of the light-sensing portion and the isolation portion, and forming a window on the front surface of the light-sensing portion by the second region; Forming a ring-shaped grid electrode positioned above the window on the front surface of the substrate, and enabling part of the ring-shaped outer side of the grid electrode and the second region to be overlapped in an upper-lower position; forming a first region of a second conductivity type below the substrate front surface of the annular inner side of the gate electrode, positioning the first region on the photosensitive portion front surface to form a partially pinned photodiode between the second region, the photosensitive portion and the first region, and forming a partial overlap in upper and lower positions between the first region and the annular inner side of the gate electrode; A contact is formed on the first region front surface within the loop shape of the gate. Further, the method further comprises the following steps: Forming a fourth region of a second conductivity type below the front surface of the substrate before forming the second region, so that the fourth region is located on the front surface of the light-sensing portion, and then forming the second region around