CN118315396A - Photomultiplier and preparation method thereof - Google Patents

Abstract

The invention relates to a photomultiplier and a preparation method thereof. A photomultiplier tube comprising a semiconductor substrate having opposed upper and lower surfaces; an insulating layer is arranged on the upper surface of the semiconductor substrate; the upper surface of the insulating layer is provided with a plurality of P-type doped semiconductor layers which are distributed at intervals, and the upper surface of the P-type doped semiconductor layer is sequentially stacked with an N-type doped semiconductor layer and a first electrode layer from bottom to top; a second electrode layer is arranged on the lower surface of the semiconductor substrate; the P-type doped semiconductor layers and the second electrode layers are electrically connected through a plurality of contact plugs in a one-to-one correspondence mode, and the contact plugs penetrate through the insulating layer and the semiconductor substrate. The invention solves the problem of increasing the crosstalk between pixels when the detection area of the pixels is increased on a plane structure.

Description

Photomultiplier tube and preparation method thereof

Technical Field

The present invention relates to the field of semiconductor devices, and in particular to a photomultiplier tube and a preparation method thereof.

Background technique

At present, silicon photomultiplier tubes based on single-photon avalanche photodiode structures have high sensitivity and can realize single-photon detection, but the photoelectric detection efficiency needs to be improved, and crosstalk between pixels is also an important reason affecting the detection results. Photon detection efficiency (PDE) is the most important characteristic of photomultiplier tubes. It is defined as the ratio of the number of detected photons to the number of incident photons. It is used to measure the ability of photomultiplier tubes to detect light power. PDE is the product of the device filling factor FF, quantum efficiency QE, and avalanche probability PT. The filling factor FF refers to the ratio of the effective photon detection area to the total area of the silicon photomultiplier tube. The increase of the filling factor FF can effectively improve the photon detection efficiency. To obtain a larger filling factor, it is necessary to increase the effective photon detection area of the silicon photomultiplier tube as much as possible on the basis of keeping the total area of the silicon photomultiplier tube unchanged. However, if the detection area of each pixel is increased in the planar structure, the crosstalk between pixels will increase at the same time due to the reduction of the pixel spacing.

To this end, the present invention is proposed.

Summary of the invention

The main purpose of the present invention is to provide a photomultiplier tube and a method for preparing the same, so as to solve the problem of increased crosstalk between pixels when increasing the pixel detection area on a planar structure.

In order to achieve the above objectives, the present invention provides the following technical solutions.

A first aspect of the present invention provides a photomultiplier tube, comprising a semiconductor substrate having an upper surface and a lower surface opposite to each other;

An insulating layer is provided on the upper surface of the semiconductor substrate; a plurality of P-type doped semiconductor layers are provided on the upper surface of the insulating layer and are distributed at intervals, and an N-type doped semiconductor layer and a first electrode layer are sequentially stacked on the upper surface of the P-type doped semiconductor layer from bottom to top;

A second electrode layer is provided on the lower surface of the semiconductor substrate;

The plurality of P-type doped semiconductor layers are electrically connected to the second electrode layer in a one-to-one correspondence via a plurality of contact plugs, and the contact plugs penetrate the insulating layer and the semiconductor substrate.

Therefore, the present invention vertically stacks the P-type doped semiconductor layer and the N-type doped semiconductor layer to form an avalanche multiplication region, and sets the two electrode layers and the avalanche multiplication region to be vertically stacked, thereby obtaining a photomultiplier tube with a three-dimensional structure, which can effectively increase the area of the device's photon absorption region, thereby improving the photon absorption efficiency and reducing the pixel area of the silicon photomultiplier tube, which is conducive to realizing the high integration of the silicon photomultiplier tube.

In addition, since the second electrode layer is a continuous layer on the surface of the semiconductor substrate, the anode of each pixel area only needs one contact point to be led out together, which simplifies the wiring difficulty.

On this basis, the layer structure of the photomultiplier tube or the materials used in each layer can be further improved, as listed below.

Furthermore, it also includes a passivation layer covering the first electrode layer.

Furthermore, the passivation layer is silicon nitride.

Furthermore, the insulating layer is silicon oxide.

Furthermore, the semiconductor substrate is a silicon substrate.

Furthermore, the contact plug is made of tungsten.

Furthermore, the first electrode layer and the second electrode layer are made of aluminum.

A second aspect of the present invention provides a method for preparing a photomultiplier tube, comprising:

Providing a substrate, the substrate comprising a semiconductor back layer, a buried oxide layer and a semiconductor top layer stacked in sequence from bottom to top;

Injecting P-type ions into the semiconductor top layer and performing etching to form a plurality of P-type doped semiconductor layers distributed at intervals;

Performing N-type ion implantation on a superficial layer of the P-type doped semiconductor layer to convert the superficial layer into an N-type doped semiconductor layer;

forming a plurality of contact holes penetrating the semiconductor back layer and the buried oxide layer, wherein one end of the contact hole contacts one of the P-type doped semiconductor layers;

Filling the contact hole with a conductive material to form a contact plug;

A conductive metal layer is formed on the surface of the semiconductor back layer and the surface of the N-type doped semiconductor layer, and the conductive metal layer on the surface of the N-type doped semiconductor layer is photolithographically processed to separate the conductive metal layer on the surface of each N-type doped semiconductor layer as a first electrode layer.

Thus, the present invention obtains a three-dimensional photomultiplier tube through multiple steps of layer-by-layer formation, and the operation of each step is simple and compatible with existing processes. Therefore, the overall preparation method is simple and has high production efficiency.

Among them, the conductive metal layer on the surface of the semiconductor back layer and the surface of the N-type doped semiconductor layer can be formed simultaneously, further improving the efficiency.

Furthermore, the method further includes: forming a passivation layer on the surface of the first electrode layer.

Furthermore, the method further comprises: performing photolithography on the passivation layer to expose at least a portion of the surface of the first electrode layer.

In summary, compared with the prior art, the present invention achieves the following technical effects:

(1) The photomultiplier tube of the present invention has a three-dimensional structure, which increases the photon absorption area of the device and improves the photon absorption efficiency of the device compared to conventional planar devices;

(2) The present invention uses a back electrode (i.e., the second electrode) to reduce the distance between pixels and improve pixel integration;

(3) The present invention fully isolates each pixel through the insulating layer structure on the semiconductor substrate, thereby reducing crosstalk between pixels.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention.

FIG1 is a schematic structural diagram of a photomultiplier tube provided by the present invention;

2 to 6 are schematic diagrams of structures obtained in each step of a method for preparing a photomultiplier tube provided by the present invention;

Reference numerals:

1-second electrode layer, 2-semiconductor back layer, 2'-semiconductor substrate, 3-insulating layer, 4-passivation layer,

5-N-type doped semiconductor layer, 6-first electrode layer, 7-P-type doped semiconductor layer, 8-contact plug.

Detailed ways

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

Various structural schematic diagrams according to embodiments of the present disclosure are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may further design regions/layers with different shapes, sizes, and relative positions according to actual needs.

In the context of the present disclosure, when a layer/element is referred to as being "on" another layer/element, the layer/element may be directly on the other layer/element or an intervening layer/element may exist between them. In addition, if a layer/element is "on" another layer/element in one orientation, the layer/element may be "below" the other layer/element when the orientation is reversed.

When the pixel detection area is increased on a planar structure, the crosstalk between pixels will increase, thereby affecting the photoelectric detection result. Based on this, the present invention proposes a photomultiplier tube as shown in FIG1 .

The photomultiplier tube of the present invention is introduced in conjunction with FIG1, which includes a semiconductor substrate 2', and the semiconductor substrate 2' has a relative upper surface and a lower surface. An insulating layer 3 is provided on the upper surface of the semiconductor substrate 2'. A plurality of P-type doped semiconductor layers 7 are provided on the upper surface of the insulating layer 3, and an N-type doped semiconductor layer 5 and a first electrode layer 6 are stacked on the upper surface of the P-type doped semiconductor layer 7 from bottom to top. A second electrode layer 1 is provided on the lower surface of the semiconductor substrate 2'. The plurality of P-type doped semiconductor layers 7 are electrically connected to the second electrode layer 1 in a one-to-one correspondence through a plurality of contact plugs 8, and the contact plugs 8 penetrate the insulating layer 3 and the semiconductor substrate 2'.

In the above-mentioned photomultiplier tube, on the one hand, a plurality of P-type doped semiconductor layers 7 and N-type doped semiconductor layers 5 are vertically stacked to form an avalanche multiplication zone. Since each P-type doped semiconductor layer 7 is arranged at intervals on the insulating layer 3, the corresponding avalanche multiplication zone is also arranged at intervals, so that each pixel is fully isolated and the crosstalk between pixels is reduced. On the other hand, the second electrode layer 1 of the present invention is arranged on the lower surface (i.e., the back side) of the substrate, which can reduce the spacing between pixels and improve the pixel integration. On the other hand, each doped layer and the two electrode layers are vertically stacked. This three-dimensional structure can effectively increase the area of the device's photon absorption region, which not only improves the photon absorption efficiency, but also reduces the pixel area of the silicon photomultiplier tube, which is conducive to achieving a high degree of integration of the silicon photomultiplier tube.

On the other hand, since the second electrode layer 1 is a continuous layer on the surface of the semiconductor substrate 2', the anode of each pixel area only needs one contact point to be led out together, which simplifies the wiring difficulty.

In the above photomultiplier tube provided by the present invention, the semiconductor substrate 2' can be any substrate for carrying semiconductor integrated circuit components known to those skilled in the art, such as silicon-on-insulator (SOI), bulk silicon, silicon carbide, germanium, silicon germanium, gallium arsenide or germanium on insulator, etc., and the corresponding top semiconductor material is silicon, germanium, silicon germanium or gallium arsenide, etc. The substrate 2' can also be a stacked structure of multiple layers of semiconductor materials. The substrate 1 can also be doped.

In the above photomultiplier tube, a passivation layer 4 may also be provided on the surface of the first electrode layer 6 to provide isolation and protection. Usually, an opening is provided on the passivation layer 4 so that the first electrode layer 6 exposed at the opening can be connected to a power source. The material of the passivation layer 4 can be any insulating material. In some embodiments, the passivation layer is silicon nitride.

The doping concentrations of the P-type doped semiconductor layer 7 and the N-type doped semiconductor layer 5 can be appropriately adjusted according to actual needs.

The insulating layer 3 may be made of silicon oxide, silicon oxynitride, oxynitride, and the like. In some embodiments, the insulating layer is made of silicon oxide. The contact plug, the first electrode layer, and the second electrode layer may each independently be made of a conductive metal material such as tungsten, aluminum, silver, cobalt, and nickel. In some embodiments, the contact plug is made of tungsten, and the first electrode layer and the second electrode layer are made of aluminum.

The present invention also provides a method for preparing the photomultiplier tube of FIG. 1 , which mainly includes the following steps (introduced with reference to FIGS. 2 to 6 ).

First, a substrate is provided, which includes a semiconductor back layer 2, a buried oxide layer (i.e., an insulating layer 3) and a semiconductor top layer stacked in sequence from bottom to top. This substrate can be directly made of an existing substrate such as SOI, or can be obtained by gradually depositing an oxide layer and a semiconductor layer on the surface of a single-layer semiconductor.

Next, P-type ions are implanted into the semiconductor top layer of the substrate and etched to form a plurality of P-type doped semiconductor layers 7 that are spaced apart from each other, as shown in FIG. 2 .

Then, N-type ions are implanted into the shallow layer of each P-type doped semiconductor layer 7 to convert the shallow layer into an N-type doped semiconductor layer 5. In order to convert it into an N region with greater distinction, heavy doping is usually required, as shown in FIG. 3 .

Next, a plurality of contact holes are formed through the semiconductor back layer 2 and the insulating layer 3. One end of the contact hole contacts a P-type doped semiconductor layer 7, and the other end can be connected to an electrode layer formed later on the back layer. The contact holes are usually formed through steps such as masking, photolithography, and mask removal.

Then, a conductive material is filled in the contact hole to form a contact plug 8 , as shown in FIG. 4 .

Afterwards, a conductive metal layer is formed on the surface of the semiconductor back layer 2 and the surface of the N-type doped semiconductor layer 5, which can be formed simultaneously. The conductive metal layer on the surface of the N-type doped semiconductor layer 5 is then photolithographically processed to separate the conductive metal layer on the surface of each N-type doped semiconductor layer as the first electrode layer 6, as shown in FIG5, and the conductive metal layer on the surface of the semiconductor back layer is used as the second electrode layer 1.

After completing the above steps, as shown in FIG. 6 , a passivation layer 4 may be formed on the surface of the first electrode layer 6 , and the passivation layer 4 is usually photolithographically processed to expose at least part of the surface of the first electrode layer 6 so as to connect the electrode to a power source.

Thus, the present invention obtains a three-dimensional photomultiplier tube through multiple steps of layer-by-layer formation, and the operation of each step is simple and compatible with existing processes. Therefore, the overall preparation method is simple and has high production efficiency.

The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, a person skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims (10)

1. A photomultiplier tube comprising a semiconductor substrate having opposed upper and lower surfaces;

An insulating layer is arranged on the upper surface of the semiconductor substrate; the upper surface of the insulating layer is provided with a plurality of P-type doped semiconductor layers which are distributed at intervals, and the upper surface of the P-type doped semiconductor layer is sequentially stacked with an N-type doped semiconductor layer and a first electrode layer from bottom to top;

A second electrode layer is arranged on the lower surface of the semiconductor substrate;

The P-type doped semiconductor layers and the second electrode layers are electrically connected through a plurality of contact plugs in a one-to-one correspondence mode, and the contact plugs penetrate through the insulating layer and the semiconductor substrate.

2. The photomultiplier tube of claim 1, further comprising a passivation layer overlying the first electrode layer.

3. The photomultiplier tube of claim 2, wherein the passivation layer is silicon nitride.

4. The photomultiplier tube of claim 1, wherein the insulating layer is silicon oxide.

5. The photomultiplier tube of claim 1, wherein the semiconductor substrate is a silicon substrate.

6. The photomultiplier tube of claim 1, wherein the contact plug is tungsten.

7. The photomultiplier tube of claim 1 or 6, wherein the first and second electrode layers are aluminum.

8. A method of manufacturing a photomultiplier tube, comprising:

Providing a substrate, wherein the substrate comprises a semiconductor back layer, a buried oxide layer and a semiconductor top layer which are stacked in sequence from bottom to top;

Injecting P-type ions into the semiconductor top layer, and etching to form a plurality of P-type doped semiconductor layers distributed at intervals;

Performing N-type ion implantation on the shallow surface layer of the P-type doped semiconductor layer to convert the shallow surface layer into an N-type doped semiconductor layer;

Forming a plurality of contact holes penetrating through the semiconductor back layer and the buried oxide layer, wherein one end of each contact hole is contacted with one P-type doped semiconductor layer;

filling conductive material in the contact hole to form a contact plug;

And forming a conductive metal layer on the surface of the semiconductor back layer and the surface of the N-type doped semiconductor layer, and photoetching the conductive metal layer on the surface of the N-type doped semiconductor layer so as to separate the conductive metal layers on the surface of each N-type doped semiconductor layer to serve as a first electrode layer.

9. The method of manufacturing a photomultiplier tube of claim 8, further comprising: and forming a passivation layer on the surface of the first electrode layer.

10. The method of manufacturing a photomultiplier tube of claim 9, further comprising: and carrying out photoetching treatment on the passivation layer to expose at least part of the surface of the first electrode layer.