CdTe Radiation Detector Electrodes With Te-Oxide Insulation
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Solution Overview
Problem
Existing radiation detecting elements using CdTe-based crystals face issues with inadequate insulation between electrodes, leading to leakage currents and reduced spatial resolution, especially when electrode distances are narrowed, resulting in defective elements and blurred images.
Innovation Solution
A method is developed where the substrate is processed without acidic etching, and electrode portions are formed through electroless plating with controlled plating time, preventing penetration of the plating solution and formation of poor-insulating oxides, ensuring high adhesion and insulation between electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the distance between electrode portions is reduced to achieve high-definition imaging, then the spatial resolution is improved, but leakage current between electrodes increases due to inadequate insulation
Solution Approach 1:
An intermediate layer containing Te oxide is introduced between the substrate and electrode portions. This intermediate layer serves as a mediator that improves adhesion between the substrate and electrodes while the insulating portion maintains electrical isolation. The intermediate layer allows the electrodes to be formed closer together without compromising insulation, thereby enabling high-definition imaging while preventing leakage current.
Solution Approach 2:
The resistivity of the insulating portion is controlled to be 10^7 Ωcm or more, and the thickness of the intermediate layer is optimized. By changing these parameters, the insulation performance is enhanced while maintaining good adhesion. This allows reduced electrode spacing without increasing leakage current, thus achieving high spatial resolution while maintaining reliability.
2Duration of action of stationary object
If an intermediate layer containing Te oxide is formed to improve adhesion between substrate and electrode, then the durability and life are extended, but the process complexity increases
Solution Approach 1:
The formation of the intermediate layer containing Te oxide is merged with the electrode formation process. The intermediate layer is formed as part of the same plating process that creates the electrode portions, eliminating the need for a separate intermediate layer deposition step. This reduces process complexity while still achieving improved adhesion and extended element life.
Solution Approach 2:
The plating solution automatically forms the intermediate layer containing Te oxide during the electrode formation process. The Te oxide forms in situ as part of the plating reaction, without requiring separate deposition steps. This self-organizing behavior simplifies the manufacturing process while ensuring durable adhesion between substrate and electrodes.
3Manufacturing precision
If acidic etching is performed to remove damaged layer on substrate surface, then the surface quality is improved, but adhesion between electrode and substrate deteriorates
Solution Approach 1:
The acidic etching step is completely removed from the manufacturing process. Instead of etching the substrate surface before electrode formation, the process directly forms electrodes on the as-polished surface. The intermediate layer that forms during plating provides sufficient adhesion without requiring acid etching, thus maintaining surface quality while improving electrode-substrate bonding strength.
Solution Approach 2:
The potentially harmful effect of omitting acid etching (reduced surface quality) is compensated by the beneficial formation of the intermediate layer during plating. This intermediate layer not only provides adhesion but also creates a favorable surface for electrode bonding. The process converts what could be a disadvantage into an advantage by using the plating process itself to create the ideal bonding interface.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enhances electrode-substrate adhesion, reduces element defects, and maintains high-definition imaging capabilities by minimizing leakage currents, improving the yield and performance of radiation detectors.
Implementation Method 1
electrode portions are formed through electroless plating with controlled plating time
Implementation Method 2
converting incidence of the radiation into a current signal by a (internal) photoelectric effect generated when the radiation is incident upon the crystal material
Data Source
Figure 1
Figure 2
Figure 3(a)~3(g)
AI summary
Provided is a radiation detecting element that has high adhesion between electrode portions and a substrate and does not suffer from performance failures due to insufficient insulation between the electrode portions, even if a distance between the electrode portions is narrower in order to obtain a high-definition radiation drawn image. The radiation detecting element includes: a plurality of electrode portions; and an insulating portion provided between the electrode portions on a surface of a substrate made of a compound semiconductor crystal containing cadmium telluride or cadmium zinc telluride, wherein an intermediate layer containing tellurium oxide is present between each of the electrode portions and the substrate, and wherein tellurium oxide is present on an upper portion of the insulating portion, and the tellurium oxide on the upper portion of the insulating portion has a maximum thickness of 30 nm or less.