A czt multilayer composite electrode based on electroless plating and a preparation method thereof

Abstract

The application provides a CZT multilayer composite electrode based on chemical plating and a preparation method thereof, wherein the multilayer composite electrode comprises a substrate, an interface regulation layer, a conductive layer and a protective layer; the substrate is used for absorbing radiation and generating an electric charge signal; the interface regulation layer is used for chemically passivating surface defects and reducing an interface state density; the conductive layer is used for providing a low-resistance conductive channel; and the protective layer is used for isolating environmental influences, blocking intermetallic diffusion and inhibiting surface leakage current; the substrate comprises a CZT wafer; the interface regulation layer comprises Pt; the conductive layer comprises Au; and the protective layer comprises Pd or Ni. The application constructs a multilayer or composite electrode structure through chemical plating, introduces a gradient layer and process window control, and realizes the effects of interface state reduction, electrode adhesion force improvement and electrical performance optimization.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to a CZT multilayer composite electrode based on chemical plating and its preparation method. Background Technology

[0002] CZT (CdZnTe) semiconductor materials have been widely used in high-end fields such as X-ray and gamma-ray detectors and nuclear medicine imaging due to their excellent room-temperature radiation detection capabilities. However, electrode fabrication, as a core step in device manufacturing, directly determines the final performance of the detector.

[0003] Currently, the industry and laboratories often use vacuum evaporation to deposit gold electrodes or chemical plating to deposit a single metal layer to prepare electrodes, but both of these technical routes have obvious shortcomings.

[0004] First, the high interface defect state density between the electrode and the CZT crystal surface not only triggers severe carrier recombination but also directly leads to large leakage current, severely impacting the detection energy resolution. Second, due to the poor adhesion between the metal plating and the semiconductor substrate, the electrode is prone to peeling or detachment during subsequent packaging or long-term operation, causing device failure. More critically, a single metal layer structure makes it difficult to flexibly and synergistically control the characteristics of Schottky or Ohmic contacts, failing to effectively balance the electrode's conductivity and interface barrier. These challenges prevent existing electrode technologies from meeting the stringent requirements of high-performance detectors for low noise, high resolution, and long-term high reliability. Therefore, there is an urgent need to develop a novel electrode with controllable structure and superior performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a CZT multilayer composite electrode based on electroless plating and its preparation method, thereby solving the problems mentioned in the background art. The present invention constructs a multilayer or composite electrode structure through electroless plating and introduces a gradient layer and process window control to achieve the effects of reducing interface states, improving electrode adhesion, and optimizing electrical performance.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: a CZT multilayer composite electrode based on chemical plating, the multilayer composite electrode comprising a substrate, an interface control layer, a conductive layer, and a protective layer, wherein the substrate is used to absorb radiation and generate charge signals; the interface control layer is used to chemically passivate surface defects and reduce interface state density; the conductive layer is used to provide low-resistance conductive channels; and the protective layer is used to isolate environmental influences, block interlayer diffusion of metals, and suppress surface leakage current.

[0007] Furthermore, the substrate includes a CZT wafer; the interface control layer includes Pt; the conductive layer includes Au; and the protective layer includes Pd or Ni.

[0008] Furthermore, the thickness of the interface control layer is 5-50 nm; the thickness of the conductive layer is 100-400 nm; and the thickness of the protective layer is 10-100 nm.

[0009] A method for preparing the above-mentioned multilayer composite electrode includes the following steps: S1, CZT substrate pretreatment; S2. An interface control layer is deposited using the first chemical plating solution; S3. A conductive layer is deposited using a second chemical plating solution; S4. A protective layer is deposited using a third chemical plating solution.

[0010] Furthermore, in S1, CZT wafers are selected, which are mechanically polished, etched with bromine-methanol solution, cleaned with deionized water, and dried.

[0011] Furthermore, in S2, a configuration containing 4wt% The solution is mixed with a complexing agent, and the pH and temperature are adjusted before electroless plating to form a Pt layer.

[0012] Furthermore, the 4wt% The solvent for the solution is methanol:DMF = 1:1, and the complexing agent used is citric acid.

[0013] Furthermore, in step S3, the sample is transferred into... Sodium sulfite is added to the electroless plating solution as a complexing agent and sodium bisulfite as a stabilizer. After adjusting the pH and temperature, an Au layer is formed.

[0014] Furthermore, in S4, in Chemical plating is performed in the solution, with ammonia added as a complexing agent and formaldehyde as a reducing agent. The pH and temperature are adjusted to allow the reaction to form a Pd layer.

[0015] Furthermore, the process for implementing the gradient layer is also included: during the electroless plating process, a Pt layer is first deposited, followed by a thin Au layer. In the plating solution at 70°C, Au diffuses into Pt, and Pt diffuses into Au to form a quasi-gradient layer.

[0016] The beneficial effects of this invention are: This invention utilizes a platinum interface control layer deposited via electroless plating. The chemical passivation effect of platinum on the CZT surface effectively eliminates surface dangling bonds and oxide defects, solving the problems of high interface defect state density and poor adhesion, while significantly suppressing leakage current. The introduction of a conductive layer ensures a stable current transmission channel with low resistance, eliminates interlayer stress, and achieves effective regulation of the Schottky / Ohmic contact. The outermost palladium protective layer suppresses carrier injection and external environmental erosion on the electrode surface, ensuring long-term reliability. Furthermore, it works synergistically with the inner layers to further reduce surface leakage current. This multi-layer synergistic mechanism reduces device leakage current, improves energy resolution, significantly improves adhesion, and lowers process costs.

[0017] This invention can improve the environmental stability of electrodes and suppress element diffusion between metal layers, thereby improving the long-term reliability of electrodes; at the same time, by regulating the work function of the electrode surface and improving the interfacial electrical properties, leakage current is reduced and device performance is improved.

[0018] In this invention, the surface defect state density of CZT is significantly reduced, thereby decreasing interfacial carrier recombination and leakage current. The dense structure and high work function of the palladium protective layer suppress carrier injection at the electrode surface and environmental influences, further reducing leakage current and improving signal stability. The synergistic effect of each layer significantly improves the device's energy resolution. Attached Figure Description

[0019] Figure 1 A schematic diagram of the multilayer composite electrode provided by the present invention; Figure 2 This is a comparison diagram of IV characteristics in a CZT multilayer composite electrode based on electroless plating according to the present invention. Detailed Implementation

[0020] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0021] Please see Figures 1 to 2 The present invention provides the following technical solution: a CZT multilayer composite electrode based on chemical plating, the multilayer composite electrode comprising a substrate, an interface control layer, a conductive layer and a protective layer, wherein the substrate is used to absorb radiation and generate charge signals; the interface control layer is used to chemically passivate surface defects and reduce interface state density; the conductive layer is used to provide low-resistance conductive channels; and the protective layer is used to isolate environmental influences, block interlayer diffusion of metals and suppress surface leakage current.

[0022] The substrate includes CZT wafers; The interface control layer includes Pt with a thickness of 5-50 nm; The conductive layer comprises Au and has a thickness of 100-400 nm; The protective layer includes Pd or Ni, with a thickness of 10-100 nm.

[0023] This embodiment also provides a method for preparing the above-mentioned CZT multilayer composite electrode based on chemical plating, including the following steps: 1) CZT substrate pretreatment; 2) An interface control layer (platinum layer) is deposited using the first chemical plating solution; 3) A conductive layer (gold layer) is deposited using a second chemical plating solution; 4) A protective layer (nickel or palladium layer) is deposited using a third chemical plating solution. Each layer is formed sequentially through a step-by-step chemical plating process.

[0024] 1. Substrate treatment: CZT wafers were selected, mechanically polished, etched with bromine-methanol solution for 30 seconds, rinsed with deionized water and dried; 2. Interface layer deposition (Pt): The mixture contains 4 wt% A solution (solvent: methanol / DMF=1:1), complexing agent: 5 g / L citric acid, pH: about 3-4, was electroless plated at 60℃ for 10 min to form a Pt layer of about 20 nm. The platinum interface layer reduces surface dangling bonds and oxide defects by chemically passivating the CZT surface, while utilizing its high work function to modulate the interface band structure, thereby reducing the interface state density and suppressing leakage current.

[0025] 3. Conductive layer deposition (Au): The sample is transferred into a 3 g / L solution... In the chemical plating solution, the complexing agent is sodium sulfite (Na2SO3): 20 g / L, the stabilizer is sodium bisulfite 5 g / L, the pH is 7-8, and the reaction is carried out at 70℃ for 15 min to form an Au layer of about 300 nm. 4. Protective layer deposition (Pd): in a solution containing 1 g / L Chemical plating is performed in solution, with ammonia as the complexing agent (forming Pd(NH3)4). 2+ (Complex), reducing agent: formaldehyde 5 mL / L, pH: 8-9, at 60℃ for 5 min, a Pd layer of about 50 nm is formed.

[0026] The protective layer is a nickel or palladium layer, which is used to improve the environmental stability of the electrode and suppress element diffusion between metal layers, thereby improving the long-term reliability of the electrode. At the same time, by adjusting the work function of the electrode surface and improving the interfacial electrical characteristics, leakage current is reduced and device performance is improved.

[0027] In this embodiment, a multilayer or composite electrode structure is constructed through electroless plating, and a gradient layer and process window control are introduced to achieve interface state reduction, electrode adhesion improvement, and electrical performance optimization (CZT / Pt / Au / Pd). Specifically, during the electroless plating process, a Pt layer (20 nm) is first deposited, followed by a thin Au layer (300 nm, of which 10-50 nm are in contact with Pt). In the plating bath at 70°C, Au diffuses towards Pt, and Pt diffuses towards Au, forming a quasi-gradient layer. Therefore, the gradient layer is formed by adjusting the diffusion method during the electroless plating process, allowing for continuous changes in composition between the interface layer and the conductive layer, thereby reducing interface resistance and alleviating stress concentration. This embodiment also provides the following specific experimental data to further explain the above technical solution.

[0028] Table 1: Experimental Data

[0029] (Low temperature and low concentration) Pt: H2PtCl62 wt%, 55℃, 12 min Au: HAuCl41 g / L, 65℃, 20 min Pd: PdCl20.5 g / L, 55℃, 8 min (High temperature and high concentration) Pt: H2PtCl66 wt%, 70℃, 8 min Au: HAuCl45 g / L, 75℃, 10 min Pd: PdCl22 g / L, 65℃, 5 min (Wide pH adjustment) Pt: pH 2.5 Au: pH 7.5 Pd: pH 8.5 Table 2: Experimental Data II

[0030] Experimental results show that, compared with a single-layer Au electrode, the introduction of a platinum interface layer significantly reduces the surface defect state density of the CZT, thereby reducing interfacial carrier recombination and leakage current. Further introduction of a palladium protective layer, through its dense structure and high work function, suppresses carrier injection at the electrode surface and environmental influences, further reducing leakage current and improving signal stability. The synergistic effect of each layer significantly improves the device's energy resolution. Ultimately, leakage current is reduced by 30–60%, and energy resolution is improved by 15–30%. Simultaneously, adhesion is improved and processing costs are reduced.

[0031] The foregoing has shown and described the basic principles and main features of the present invention and its advantages. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0032] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a CZT multilayer composite electrode based on electroless plating, characterized in that: Includes the following steps: S1, CZT substrate pretreatment; S2. An interface control layer is deposited using the first chemical plating solution; S3. A conductive layer is deposited using a second chemical plating solution; S4. A protective layer is deposited using a third chemical plating solution; the substrate is used to absorb radiation and generate charge signals; the interface control layer is used to chemically passivate surface defects and reduce interface state density. The conductive layer is used to provide a low-resistance conductive channel; The protective layer is used to isolate environmental influences, block interlayer diffusion of metals, and suppress surface leakage current. In step S1, CZT wafers are selected, mechanically polished, etched with bromine-methanol solution, cleaned with deionized water, and dried; in step S2, a solution containing 4 wt% is prepared. The solution, after adding a complexing agent and adjusting the pH and temperature, is subjected to chemical plating to form a Pt layer; the 4wt% The solvent for the solution is methanol:DMF = 1:1, and the complexing agent used is citric acid; in step S3, the sample is transferred into... In the electroless plating solution, sodium sulfite is added as a complexing agent and sodium bisulfite as a stabilizer. After adjusting the pH and temperature, an Au layer is formed; in step S4, in... Chemical plating is carried out in the solution, with ammonia water added as a complexing agent and formaldehyde as a reducing agent, and the pH and temperature are adjusted to react and form a Pd layer. It also includes the implementation process of the gradient layer: during the chemical plating process, a Pt layer is first deposited, followed by a thin Au layer. In the plating solution at 70°C, Au diffuses to Pt, and Pt diffuses to Au to form a quasi-gradient layer.

2. A CZT multilayer composite electrode based on electroless plating prepared using the method of claim 1, characterized in that: The multilayer composite electrode includes a substrate, an interface control layer, a conductive layer, and a protective layer. The substrate includes a CZT wafer; the interface control layer includes Pt; the conductive layer includes Au; and the protective layer includes Pd.

3. The CZT multilayer composite electrode based on electroless plating according to claim 2, characterized in that: The thickness of the interface control layer is 5-50 nm; the thickness of the conductive layer is 100-400 nm; and the thickness of the protective layer is 10-100 nm.

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