CdZnTe Radiation Detector Fabrication via Mechanical Polishing
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Solution Overview
Problem
Radiation semiconductor detectors, particularly those using Cadmium Zinc Telluride (CdZnTe), face instability and reduced performance due to chemical wet etching, leading to low energy resolution, sensitivity, and high production costs, caused by tellurium-rich surfaces with low surface resistance and incomplete charge collection.
Innovation Solution
A method involving mechanical polishing and selective etching to create stoichiometric surfaces without chemical wet etching, applying encapsulation layers and photoresist techniques to form pixelated anode electrodes and monolithic cathodes, ensuring complete charge collection and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical wet etching is used to create tellurium-rich surfaces, then Ohmic contacts can be formed, but surface resistance becomes low and unstable leading to reduced detector performance
Solution Approach 1:
The patent changes the surface composition parameter from tellurium-rich (created by chemical etching) to stoichiometric (maintained by mechanical polishing only). This parameter change stabilizes the surface resistance while maintaining Ohmic contact properties, resolving the contradiction between reliability and manufacturing precision.
Solution Approach 2:
The patent extracts the chemical etching step from the fabrication process, removing the source of tellurium enrichment. By eliminating this harmful chemical process and relying solely on mechanical polishing, the patent achieves stable surface resistance without compromising contact quality.
2Object-affected harmful factors
If chemical wet etching is performed to remove mechanical damage, then surfaces are cleaned, but tellurium enrichment occurs causing low surface resistance and instability
Solution Approach 1:
The patent removes the chemical etching step that causes tellurium enrichment. By extracting this harmful process while retaining mechanical polishing, the patent eliminates surface composition instability while still removing mechanical damage effectively.
Solution Approach 2:
The patent replaces the chemical etching system with an enhanced mechanical polishing system. By using carefully controlled mechanical polishing with appropriate slurries and parameters, the patent achieves mechanical damage removal without the harmful side effect of tellurium enrichment.
3Ease of manufacture
If tellurium-rich surfaces are created through chemical etching, then contacts can be applied, but production yield decreases and costs increase
Solution Approach 1:
The patent extracts the chemical etching step that creates production variability. By eliminating this unpredictable chemical process, the patent achieves more consistent results across production batches, thereby improving production yield and reducing costs.
Solution Approach 2:
The patent allows the mechanical polishing process to self-regulate the surface properties needed for contact application. The polishing process inherently creates the appropriate surface condition without requiring subsequent chemical treatment, simplifying the manufacturing process and improving yield.
4Ease of manufacture
If chemical wet etching is used to create surfaces for contacts, then contacts can be formed, but detector performance degrades over time
Solution Approach 1:
The patent removes the chemical etching step that initiates long-term degradation. By eliminating the chemical treatment that creates unstable tellurium-rich surfaces, the patent prevents the onset of performance degradation and extends detector lifetime.
Solution Approach 2:
The patent applies mechanical polishing with controlled parameters to prevent future degradation before it occurs. By creating a stable, stoichiometric surface from the beginning, the patent cushions against long-term performance loss and maintains detector quality throughout its operational life.
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
This approach enhances energy resolution and sensitivity, improves detector reliability and yield, and reduces manufacturing costs by maintaining high surface resistivity and preventing chemical degradation, resulting in higher-quality and more stable radiation detectors.
Implementation Method 1
applying (i) an encapsulation layer on a top of the polished first surface to seal the polished first surface
Implementation Method 2
partially etching the encapsulation layer via the openings in the photoresist layer to partially remove the encapsulation layer and creating undercuts of the encapsulation layer under the photoresist layer
Implementation Method 3
mechanically polishing at least a first surface of a semiconductor wafer using a polishing sequence including a plurality of polishing steps, wherein a last polishing step of the polishing sequence includes polishing with a slurry having a grain size smaller than about 0.1 μm
Implementation Method 4
applying pixelated anode electrodes in the etched regions of the first surface and a monolithic cathode electrode on a second surface of the semiconductor
Data Source
AI summary
Radiation detectors and methods of fabricating radiation detectors are provided. One method includes mechanically polishing at least a first surface of a semiconductor wafer using a polishing sequence including a plurality of polishing steps, wherein a last polishing step of the polishing sequence includes polishing with a slurry having a grain size smaller than about 0.1 μm to create a polished first surface. The method also includes applying (i) an encapsulation layer on a top of the polished first surface to seal the polished first surface and (ii) a photoresist layer on top of the encapsulation layer on the polished first surface. The method further includes creating undercuts of the encapsulation layer under the photoresist layer. The method additionally includes partially etching the polished first surface of the semiconductor via the openings in the photoresist layer and in the encapsulation layer to partially etch the semiconductor creating etched regions.