阅读说明：本技术 一种双保护环结构的新型spad探测器 (Novel SPAD detector with double-protection-ring structure ) 是由 毛成 卜晓峰 孔祥顺 吴俊辉 于 2018-07-25 设计创作，主要内容包括：本发明公开了一种双保护环结构的新型SPAD探测器,采用p+层和n-type层之间形成的pn结作为反应结,p+层四周设计pwell阱作为第一保护环；同时,pwell保护环上方设计一层poly层,与pn结阴极相连施加高电位,作为第二保护环。第一保护环和第二保护环共同作用,能有效降低边缘电场,减小暗计数。(The invention discloses a novel SPAD detector with a double-protection-ring structure, which adopts a pn junction formed between a p + layer and an n-type layer as a reaction junction, and designs a pwell well around the p + layer as a first protection ring; meanwhile, a poly layer is designed above the pwell guard ring, and a high potential is applied to the p-n junction cathode to be used as a second guard ring. The first protective ring and the second protective ring act together, so that the fringe electric field can be effectively reduced, and the dark count is reduced.)

1. The novel SPAD detector with the double-protection-ring structure is characterized in that a pn junction formed between a p + layer and an n-type layer is used as a reaction junction, a pwell well is used as a first protection ring on the periphery of the p + layer, a poly layer is designed above the pwell protection ring and is used as a second protection ring, and the poly layer is overlapped with the pwell layer and is not overlapped with the p + layer.

2. The SPAD detector of claim 1, further characterized in that a dnw layer separates the individual detector from the P-sub substrate, the n + layer serves as a contact hole to transmit high potential into the dnw layer to form the cathode of the SPAD detector, and the P + layer serves as the anode of the SPAD detector and is connected to low potential.

3. A SPAD detector according to claims 1 and 2, further characterized in that the poly layer is directly connected to the n + layer, and the same potential is applied.

Technical Field

The invention relates to a novel SPAD detector with a double-protection-ring structure, which is used as a photosensitive unit, belongs to the field of photoelectric detection, and particularly relates to the field of single photon detection based on a silicon-based semiconductor technology.

Background

The single photon detection technology is a detection technology based on single photons, can detect extremely weak light signals and is a new detection technology. The single photon detection technology has wide application, and comprises the fields of medical diagnosis, astronomical observation, spectral measurement, quantum communication and the like. Single Photon Avalanche Diodes (SPADs) operate in geiger mode and are one of the most promising Single photon detectors.

In a Geiger mode, the applied reverse bias voltage of the single photon avalanche diode is higher than avalanche voltage, and the single photon avalanche diode has extremely high current gain and can be used for single photon detection. The specific working principle is as follows: when a photon enters the SPAD photosensitive region, the photon is absorbed by the depletion region with a certain probability and generates an electron-hole pair, and the electron-hole pair can rapidly generate a large number of carriers through a multiplication effect under the action of a strong electric field in the depletion region, namely triggering one-time avalanche breakdown.

The structural design of the single photon avalanche diode is the core of the SPAD detector, the parameters mainly considered in the design are the depth, the concentration, the avalanche breakdown point voltage and other basic parameters of a pn junction, and meanwhile, performance parameters such as detection efficiency, duty ratio, dark count and the like also need to be considered, and the optimization of the performance of the dark count is always important.

At present, in the prior art, the structural forms of SPAD detectors are numerous, the adopted reaction junction forms are various, and the SPAD detectors comprise a p + layer and an nwell layer, a pwell layer and a dnw layer, and a series of novel innovative structures.

Disclosure of Invention

The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention provides the novel SPAD detector with the double-protection-ring structure, which can effectively inhibit the generation of dark counts and control the dark counts within a certain range.

The technical scheme is as follows: in order to achieve the purpose, the technical scheme of the invention is as follows:

the utility model provides a novel SPAD detector of two guard ring structures, adopts the pn knot that forms between p + layer and the n-type layer as the reaction junction, and the p + layer is by pwell well as first guard ring all around, and pwell guard ring top designs the poly layer of one deck, as the second guard ring, the overlap of poly layer and pwell layer is not overlapped with the p + layer.

And a dnw layer is adopted to separate the single detector from the P-sub substrate, the n + layer is used as a contact hole to transmit high potential into the dnw layer to form a cathode of the SPAD detector, and the P + layer is used as an anode of the SPAD detector and is connected with low potential. The poly layer is directly connected with the n + layer, the same high potential is applied, the voltage difference between the pwell and the bottom dnw layer is reduced through the partial pressure of the oxide layer, the electric field intensity of the p + edge is effectively reduced, and therefore the generation of dark counts is reduced.

Has the advantages that: compared with the prior art, the SPAD detector with the double-protection-ring structure has obvious advantages, and particularly, the double-protection-ring structure of the pwell well and the poly layer can effectively reduce the fringe electric field of the reaction junction, so that the dark count of the SPAD detector is reduced.

Drawings

FIG. 1 is a schematic structural diagram of a novel SPAD detector with a double-guard ring structure provided by the invention;

fig. 2 is a plan layout of the novel SPAD detector with a double guard ring structure provided by the invention.

Detailed Description

The invention will be further described with reference to the accompanying drawings.

Fig. 1 is a schematic structural diagram of a novel SPAD detector with a double-guard ring structure provided by the present invention, which is from bottom to top: 1. the p-sub layer represents a p-type substrate of a wafer, the 2, dnw layers represent n-type wells with deeper implantation depth, the 3, n-type layers represent n-type implantation layers with lower concentration relative to the dnw layers, the 4, annular pwell represents p-type wells, the p-type wells surround the p + layers and serve as first protection rings, the 5, p + layers represent p-type implantation layers with shallower implantation depth and higher concentration, junctions between the p + layers and the n-type layers below are reaction junctions, the 6, annular poly layers represent polycrystalline silicon layers formed above the silicon wafer and serve as second protection rings, and the function of the p-sub layer comprises the following steps: a) the poly is formed before the p + injection, so that the p + injection can be avoided under the poly, the p + cannot be connected to the STI region with more impurities, the concentration of the region under the poly stops at the concentration of a pwell, and the fringe electric field can be reduced when high voltage is applied; b) when the voltage divider works, poly is connected with a pn junction cathode, and high potential is applied, so that the voltage difference between the p + voltage and the n-type voltage is smaller than that between the p + voltage and the n-type voltage on pwell below the poly after voltage division, and the fringe electric field is also reduced. In the structure of fig. 1, the silicon wafer surface from the middle to both sides except the p + layer and pwell layer are: 1. the STI region is used for shallow trench isolation and mainly used for isolation, and the 2 and n + layers are used for an n-type injection layer with shallow injection depth and high concentration and are mainly used for contact hole connection, and high potential is transmitted into the dnw layer through ohmic contact.

Fig. 2 shows a planar layout of the novel SPAD detector with a double guard ring structure according to the present invention. In the figure, the loop formed between 1 and 3 is the region of pwell layer, which is the first protective loop; the circle 2 is a p + region, and the periphery of the p + region is surrounded by a pwell ring; the area within circle 3 is also an AA area, namely an active area; a poly layer is arranged above the ring formed between the two layers 2 and 3 and is a second protection ring; the ring formed between 3 and 4 is an STI region; the ring formed between 4 and 5 is an n + region; the ring formed between 5 and 6 is an STI region; the dnw area is located below the circle 6.