Cadmium telluride detector with separated electron and hole transport channels and preparation method thereof

Abstract

The present invention discloses a method for preparing a cadmium telluride detector with separated electron and hole transmission channels, comprising: providing a substrate, coating a photoresist mask layer on both sides of the substrate; providing a mask plate, the mask plate having an exposure window, using the exposure window to expose the to-be-doped region on both sides of the substrate; injecting doping ions into the to-be-doped regions on both sides of the substrate by an ion implantation device, so as to construct an N-type electron transmission channel in the substrate, forming a periodic PN structure. The present invention constructs an N-type electron transmission channel that penetrates both sides in a P-type cadmium telluride crystal by a double-sided ion implantation method, so that the transmission of electrons and the transmission of holes are separated in space, so as to effectively avoid the problem of carrier recombination, weaken the influence of carrier recombination and hole tailing effect on the attenuation constant, and improve the image quality of the detector.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a cadmium telluride detector with separated electron and hole transmission channels and a preparation method thereof. Background Art

[0002] Given that CdTe / CdZnTe detectors have high resistivity, ideal bandgap width, and are suitable for working at room temperature, they are widely used in space science, environmental monitoring, nuclear medicine, security, industrial non-destructive testing, etc. Especially in the medical field, CdTe / CdZnTe detectors have higher quantum detection efficiency and smaller pixel size compared to other semiconductor detectors, and can achieve higher spatial resolution at a lower dose. Therefore, CdTe / CdZnTe detectors have become one of the key materials for future development in this field.

[0003] In CdTe / CdZnTe crystals, the hole mobility is more than two orders of magnitude smaller than the electron mobility, which greatly increases the probability of hole carriers being captured and recombined. The hole tailing phenomenon seriously affects the detector image quality. To address this problem, a method of increasing the bias voltage to enhance the internal electric field strength is currently provided, thereby simultaneously improving the collection efficiency of electrons and holes to reduce the probability of hole carriers being captured and recombined. The increase in bias voltage alleviates the impact of carrier recombination and hole tailing effects on the attenuation constant to a certain extent. However, excessive bias voltage also leads to an increase in dark current, affecting the detector image quality. Therefore, a method that can solve the hole tailing phenomenon in CdTe / CdZnTe detectors has not yet been proposed. Summary of the invention

[0004] To this end, the technical problem to be solved by the present invention is to overcome the problems existing in the prior art, and a cadmium telluride detector with separated electron and hole transmission channels and a preparation method thereof are proposed. A two-sided through-N-type electron transmission channel is constructed in a P-type cadmium telluride crystal on both sides of a substrate by double-sided ion implantation. On the one hand, a local PNPN... periodic PN structure is generated inside the crystal to improve the efficiency of electron and hole separation and further improve the photon detection sensitivity of the detector; on the other hand, the transmission of electrons and the transmission of holes are separated in space to effectively avoid the problem of carrier recombination, weaken the influence of carrier recombination and hole tailing effect on the attenuation constant, and improve the image quality of the detector.

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a cadmium telluride detector with separated electron and hole transmission channels, comprising:

[0006] Providing a substrate, coating photoresist mask layers on both sides of the substrate;

[0007] Providing a mask having an exposure window, and using the exposure window to expose the areas to be doped on both sides of the substrate;

[0008] Doping ions are implanted into the regions to be doped on both sides of the substrate by ion implantation equipment to construct an N-type electron transmission channel in the substrate to form a periodic PN structure.

[0009] In one embodiment of the present invention, a mask is provided, wherein the mask has an exposure window, and the exposure window is used to expose the areas to be doped on both sides of the substrate, including:

[0010] The exposure window of the mask is aligned with the regions to be doped on both sides of the substrate, and exposure and development treatment is performed to expose the regions to be doped on both sides of the substrate.

[0011] In one embodiment of the present invention, there is at least one region to be doped, and doping ions are implanted into the at least one region to be doped by an ion implantation device to construct an N-type electron transmission channel in the substrate to form a periodic PN structure.

[0012] In one embodiment of the present invention, the regions to be doped on both sides of the substrate are connected.

[0013] In one embodiment of the present invention, the N-type electron transmission channels on both sides of the substrate are connected.

[0014] In one embodiment of the present invention, the substrate is a P-type cadmium telluride crystal.

[0015] In one embodiment of the present invention, the doping ions are elements that can achieve N-type doping of the P-type cadmium telluride crystal.

[0016] In one embodiment of the present invention, the doping ion is any one of Cl, Ga, In, and Sn.

[0017] In one embodiment of the present invention, the substrate is a P-type cadmium zinc telluride crystal.

[0018] In addition, the present invention also provides a cadmium telluride detector with separated electron and hole transport channels, which is prepared by the preparation method of the cadmium telluride detector with separated electron and hole transport channels as described above.

[0019] The above technical solution of the present invention has the following advantages compared with the prior art:

[0020] 1. The present invention constructs a two-sided through-N-type electron transmission channel in a P-type cadmium telluride crystal by double-sided ion implantation on both sides of the substrate, so that the transmission of electrons and the transmission of holes are separated in space, so as to effectively avoid the problem of carrier recombination, weaken the influence of carrier recombination and hole tailing effect on the attenuation constant, and improve the image quality of the detector;

[0021] 2. The present invention constructs an N-type electron transmission channel that penetrates both sides in a P-type cadmium telluride crystal by double-sided ion implantation on both sides of the substrate, so that a local PNPN... periodic PN structure is generated inside the crystal to improve the efficiency of electron-hole separation and further improve the photon detection sensitivity of the detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 A schematic diagram of the process for preparing a cadmium telluride detector with separated electron and hole transport channels provided by the present invention.

[0024] Figure 2 A schematic flow chart of a method for preparing a cadmium telluride detector with separated electron and hole transport channels provided by the present invention.

[0025] Figure 3 This is a schematic diagram of the energy level structure of pure cadmium telluride provided by the present invention.

[0026] Figure 4 This is a schematic diagram of the energy level structure of chlorine-doped cadmium telluride provided by the present invention.

[0027] Figure 5 This is a schematic diagram of the energy level structure of gallium-doped cadmium telluride provided by the present invention.

[0028] Figure 6 This is a schematic diagram of the energy level structure of indium-doped cadmium telluride provided by the present invention.

[0029] Figure 7 This is a schematic diagram of the structure of a cadmium telluride detector with separated electron and hole transmission channels provided by the present invention.

[0030] The reference numerals are described as follows: 10, substrate; 20, photoresist mask layer; 30, region to be doped; DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but only represents the selected embodiments of the present invention. Based on the embodiments of the present invention, those skilled in the art should understand that: it is still possible to modify the technical solutions of each embodiment, or to replace some of the technical features therein by equivalent; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of each embodiment of the present invention, and all other embodiments obtained without making creative work belong to the scope of protection of the present invention.

[0032] Figure 1 The figure shows the process schematic diagram of the ion implantation method of CdTe / CdZnTe crystal. Since the saturated vapor pressure of cadmium is much greater than the saturated vapor pressure of tellurium at the same temperature, the CdTe / CdZnTe crystals prepared by conventional processes often have a large number of cadmium vacancies and exhibit the properties of a P-type semiconductor. Therefore, please refer to Figure 2 As shown, an embodiment of the present invention provides a method for preparing a cadmium telluride detector with separated electron and hole transmission channels, which specifically includes the following steps:

[0033] S100: providing a substrate, and coating photoresist mask layers on both sides of the substrate;

[0034] S200: providing a mask having an exposure window, and using the exposure window to expose the areas to be doped on both sides of the substrate;

[0035] S300: implanting doping ions into the to-be-doped regions on both sides of the substrate by means of an ion implantation device, so as to construct an N-type electron transmission channel in the substrate and form a periodic PN structure.

[0036] In a method for preparing a cadmium telluride detector with separated electron and hole transmission channels disclosed in an embodiment of the present invention, the present invention constructs an N-type electron transmission channel that penetrates both sides in a P-type cadmium telluride crystal on both sides of a substrate by double-sided ion implantation, so that the transmission of electrons and the transmission of holes are separated in space, so as to effectively avoid the problem of carrier recombination, weaken the influence of carrier recombination and hole tailing effect on the attenuation constant, and improve the image quality of the detector.

[0037] In a method for preparing a cadmium telluride detector with separated electron and hole transmission channels disclosed in an embodiment of the present invention, the present invention constructs an N-type electron transmission channel that penetrates both sides in a P-type cadmium telluride crystal by double-sided ion implantation on both sides of a substrate, so that a local PNPN... periodic PN structure is generated inside the crystal to improve the efficiency of electron and hole separation and further improve the photon detection sensitivity of the detector.

[0038] In a method for preparing a cadmium telluride detector with separated electron and hole transport channels disclosed in an embodiment of the present invention, for S100 of the above-mentioned implementation, the substrate may be a P-type cadmium telluride crystal or a P-type cadmium zinc telluride crystal.

[0039] In a method for preparing a cadmium telluride detector with separated electron and hole transport channels disclosed in an embodiment of the present invention, for S200 of the above-mentioned embodiment, a mask is provided, wherein the mask has an exposure window, and the exposure window is used to expose the areas to be doped on both sides of the substrate, including: aligning the exposure window of the mask with the areas to be doped on both sides of the substrate, performing exposure and development treatment to expose the areas to be doped on both sides of the substrate.

[0040] There is at least one region to be doped, and doping ions are implanted into the at least one region to be doped by an ion implantation device to construct an N-type electron transmission channel in the substrate to form a periodic PN structure.

[0041] It should be noted that the regions to be doped on both sides of the P-type cadmium telluride crystal / P-type cadmium zinc telluride crystal are simultaneously implanted with doping ions by an ion implantation device, that is, a double-sided ion implantation method is used to construct an N-type electron transmission channel that penetrates both sides in the P-type cadmium telluride crystal / P-type cadmium zinc telluride crystal.

[0042] Furthermore, the regions to be doped on both sides of the substrate are connected, and the regions to be doped that are connected on both sides constitute the regions to be doped on the P-type cadmium telluride crystal / P-type cadmium zinc telluride crystal for implanting doping ions.

[0043] As a preferred embodiment, the number of regions to be doped on the above-mentioned P-type cadmium telluride crystal / P-type cadmium zinc telluride crystal can be three, and the three regions to be doped are evenly distributed on the P-type cadmium telluride crystal / P-type cadmium zinc telluride crystal. At this time, the mask has three corresponding exposure windows, and the three exposure windows of the mask are aligned with the three regions to be doped of the substrate, and exposure and development treatment are performed to expose the three regions to be doped of the substrate. The three regions to be doped are implanted with doping ions through ion implantation equipment to construct an N-type electron transmission channel in the substrate to form a periodic PN structure.

[0044] In a method for preparing a cadmium telluride detector with separated electron and hole transport channels disclosed in an embodiment of the present invention, for S300 in the above embodiment, the doping ions are elements that can achieve N-type doping of the P-type cadmium telluride crystal. Preferably, the doping ions include but are not limited to Cl, Ga, In and Sn.

[0045] Specifically, Figure 3 , Figure 4 , Figure 5 as well as Figure 6 Schematic diagrams of the energy level structures of pure cadmium telluride, chlorine-doped cadmium telluride, gallium-doped cadmium telluride and indium-doped cadmium telluride. By comparing the energy level structures of doped cadmium telluride and pure cadmium telluride, it is found that chlorine-, gallium- and indium-doped cadmium telluride exhibit N-type conductivity.

[0046] In summary, the present invention constructs an N-type electron transmission channel that penetrates both sides in a P-type cadmium telluride crystal by a double-sided ion implantation method on both sides of the substrate. On the one hand, a local PNPN... periodic PN structure is generated inside the crystal to improve the efficiency of electron-hole separation and further improve the photon detection sensitivity of the detector; on the other hand, the transmission of electrons and the transmission of holes are separated in space to effectively avoid the problem of carrier recombination, weaken the influence of carrier recombination and hole tailing effect on the attenuation constant, and improve the image quality of the detector.

[0047] Based on the above method embodiment, the present invention uses a specific embodiment to explain in more detail the preparation method of the cadmium telluride detector with separated electron and hole transport channels.

[0048] Example 1

[0049] S100: providing a substrate, wherein the substrate is a P-type cadmium telluride crystal, and coating a photoresist mask layer on both sides of the P-type cadmium telluride crystal;

[0050] S200: providing a mask having an exposure window, and using the exposure window to expose the to-be-doped regions on both sides of the P-type cadmium telluride crystal;

[0051] S300: implanting doping ions Ga into the to-be-doped regions on both sides of the P-type cadmium telluride crystal by ion implantation equipment, so as to construct an N-type electron transmission channel in the P-type cadmium telluride crystal and form a periodic PN structure.

[0052] Example 2

[0053] S100: providing a substrate, wherein the substrate is a P-type cadmium telluride crystal, and coating a photoresist mask layer on both sides of the P-type cadmium telluride crystal;

[0054] S200: providing a mask having an exposure window, and using the exposure window to expose the to-be-doped regions on both sides of the P-type cadmium telluride crystal;

[0055] S300: injecting doping ions Cl into the to-be-doped regions on both sides of the P-type cadmium telluride crystal by ion implantation equipment, so as to construct an N-type electron transmission channel in the P-type cadmium telluride crystal and form a periodic PN structure.

[0056] Example 3

[0057] S100: providing a substrate, wherein the substrate is a P-type cadmium telluride crystal, and coating a photoresist mask layer on both sides of the P-type cadmium telluride crystal;

[0058] S200: providing a mask having an exposure window, and using the exposure window to expose the to-be-doped regions on both sides of the P-type cadmium telluride crystal;

[0059] S300: implanting doping ions In into the to-be-doped regions on both sides of the P-type cadmium telluride crystal by means of an ion implantation device, so as to construct an N-type electron transmission channel in the P-type cadmium telluride crystal and form a periodic PN structure.

[0060] Example 4

[0061] S100: providing a substrate, wherein the substrate is a P-type cadmium zinc telluride crystal, and coating a photoresist mask layer on both sides of the P-type cadmium zinc telluride crystal;

[0062] S200: providing a mask having an exposure window, and using the exposure window to expose the to-be-doped regions on both sides of the P-type cadmium zinc telluride crystal;

[0063] S300: injecting doping ions Ga into the to-be-doped regions on both sides of the P-type CdZnTe crystal by ion implantation equipment, so as to construct an N-type electron transmission channel in the P-type CdZnTe crystal and form a periodic PN structure.

[0064] Example 5

[0065] S100: providing a substrate, wherein the substrate is a P-type cadmium zinc telluride crystal, and coating a photoresist mask layer on both sides of the P-type cadmium zinc telluride crystal;

[0066] S200: providing a mask having an exposure window, and using the exposure window to expose the to-be-doped regions on both sides of the P-type cadmium zinc telluride crystal;

[0067] S300: injecting doping ions Cl into the to-be-doped regions on both sides of the P-type CdZnTe crystal by ion implantation equipment, so as to construct an N-type electron transmission channel in the P-type CdZnTe crystal and form a periodic PN structure.

[0068] Example 6

[0069] S100: providing a substrate, wherein the substrate is a P-type cadmium zinc telluride crystal, and coating a photoresist mask layer on both sides of the P-type cadmium zinc telluride crystal;

[0070] S200: providing a mask having an exposure window, and using the exposure window to expose the to-be-doped regions on both sides of the P-type cadmium zinc telluride crystal;

[0071] S300: implanting doping ions In into the to-be-doped regions on both sides of the P-type CdZnTe crystal by ion implantation equipment, so as to construct an N-type electron transmission channel in the P-type CdZnTe crystal and form a periodic PN structure.

[0072] Corresponding to the above method embodiment, the present invention provides an embodiment of a cadmium telluride detector with separated electron and hole transport channels, see Figure 7 As shown, in this embodiment, a cadmium telluride detector with separated electron and hole transmission channels is prepared by the preparation method of the cadmium telluride detector with separated electron and hole transmission channels described above, and its structure specifically includes:

[0073] A substrate having a region to be doped;

[0074] A photoresist mask layer coated on both sides of the substrate;

[0075] Wherein, the region to be doped on the above substrate is exposed on both sides of the substrate through an exposure window on a provided mask, and the region to be doped is exposed on both sides of the substrate.

[0076] In a cadmium telluride detector with separated electron and hole transmission channels disclosed in an embodiment of the present invention, the present invention constructs an N-type electron transmission channel that penetrates both sides in a P-type cadmium telluride crystal on both sides of a substrate by a double-sided ion implantation method, so that the transmission of electrons and the transmission of holes are separated in space, so as to effectively avoid the problem of carrier recombination, weaken the influence of carrier recombination and hole tailing effect on the attenuation constant, and improve the image quality of the detector.

[0077] In a cadmium telluride detector with separated electron and hole transmission channels disclosed in an embodiment of the present invention, the present invention constructs an N-type electron transmission channel that penetrates both sides in a P-type cadmium telluride crystal by double-sided ion implantation on both sides of a substrate, so that a local PNPN... periodic PN structure is generated inside the crystal to improve the efficiency of electron and hole separation and further improve the photon detection sensitivity of the detector.

[0078] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0079] The above is a detailed introduction to a cadmium telluride detector with separated electron and hole transport channels and a preparation method thereof provided by the present invention. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a cadmium telluride detector with separated electron and hole transport channels, characterized in that: include: Providing a substrate, coating photoresist mask layers on both sides of the substrate; Providing a mask having an exposure window, aligning the exposure window of the mask with the regions to be doped on both sides of the substrate, and performing exposure and development processing to expose the regions to be doped on both sides of the substrate; Injecting doping ions into at least one of the regions to be doped by an ion implantation device to construct an N-type electron transmission channel in the substrate to form a periodic PN structure; Wherein, the substrate is a P-type cadmium telluride crystal or a P-type cadmium zinc telluride crystal, the regions to be doped on both sides of the substrate are connected, and the N-type electron transmission channels on both sides of the substrate are connected; The regions to be doped are uniformly distributed on the P-type cadmium telluride crystal / P-type cadmium zinc telluride crystal.

2. The method for preparing the cadmium telluride detector with separated electron and hole transport channels as claimed in claim 1, characterized in that: The doping ions are elements that can achieve N-type doping of the P-type cadmium telluride crystal.

3. The method for preparing the cadmium telluride detector with separated electron and hole transport channels as claimed in claim 2, characterized in that: The doping ion is any one of Cl, Ga, In, and Sn.

4. A cadmium telluride detector with separated electron and hole transport channels, characterized in that: The detector is prepared by the method for preparing a cadmium telluride detector with separated electron and hole transport channels as described in any one of claims 1 to 3.

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