Electroless Semiconductor Contacts for Leakage Reduction
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Solution Overview
Problem
Current methods for depositing contacts on semiconductor materials like cadmium telluride for high energy physics applications are limited in terms of contact materials available, leading to issues with leakage current and polarization, and do not allow for the deposition of materials with work functions different from gold, platinum, or palladium.
Innovation Solution
A two-stage chemical electroless process is used to deposit and reduce oxides of desired contact materials on semiconductor surfaces, enabling a wider range of contact materials with different work functions, including metals and non-metals, by immersing the semiconductor in specific acidic and basic solutions to form and reduce insoluble oxide layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If physical deposition methods (e.g., sputtering) are used to deposit contacts, then good contact formation is achieved, but the process becomes complex and requires additional annealing steps
Solution Approach 1:
The invention extracts and eliminates the annealing step from the conventional physical deposition process. By using chemical electroless deposition, the contact material is deposited directly in its metallic form with inherent adhesion to the semiconductor substrate, removing the need for subsequent thermal annealing that was required in sputtering methods to achieve good contact formation.
Solution Approach 2:
The invention replaces the physical deposition mechanism (sputtering) with a chemical deposition mechanism (electroless deposition). Instead of using physical sputtering of metal atoms onto the substrate followed by thermal annealing, the process uses chemical reduction of metal ions from solution directly onto the semiconductor surface, achieving both deposition and activation in a single step.
2Ease of manufacture
If standard chemical electroless deposition is used with gold, platinum, or palladium, then simple and quick deposition is achieved, but the range of contact materials is limited
Solution Approach 1:
The invention creates a universal chemical electroless deposition process that can deposit multiple different contact materials (Au, Pt, Pd, Ag, Cu, Al, and their alloys) using a common methodology. The process uses metal salt solutions with appropriate reducing agents, allowing the same basic approach to be applied across different contact materials, thus expanding versatility while maintaining simplicity.
Solution Approach 2:
The invention enables deposition of different contact materials by changing the chemical parameters of the deposition solution - specifically the metal salt precursor and reducing agent combination. Each contact material requires specific solution chemistry (e.g., different pH, different reducing agents), but the overall electroless deposition mechanism remains the same, allowing versatile material selection through parameter adjustment.
3Productivity
If physical vapor phase transport methods are used to grow bulk single crystals, then practical bulk scale production is achieved, but oxide layers may form on the surface
Solution Approach 1:
The invention converts the potentially harmful oxide layer into a beneficial intermediate step. Rather than attempting to prevent oxide formation during crystal growth, the process deliberately allows oxidation during the first electroless deposition stage, then uses this oxide layer as the substrate for subsequent metal deposition. The oxide serves as an anchoring layer that enhances adhesion of the contact material to the semiconductor surface.
4Ease of manufacture
If conventional contacts are used on CdTe detectors, then standard fabrication is maintained, but leakage current increases and polarization effects occur
Solution Approach 1:
The invention applies local quality optimization by creating different contact types (injecting vs. blocking) with specific material selections and deposition conditions tailored to each contact's function. The electroless deposition process allows precise control of contact material properties and interface characteristics, enabling optimization of local contact behavior to minimize leakage current and polarization while maintaining overall detector performance.
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 method allows for the deposition of contacts with improved ohmic behavior and reduced polarization, increasing the range of available contact materials and achieving better performance in high energy radiation detection devices.
Implementation Method 1
the relatively insoluble oxide is formed chemically at the semiconductor surface by oxidation of the semiconductor material at the surface
Implementation Method 2
reducing the oxide via a chemical electroless process to produce a contact of the desired material
Data Source
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AI summary
A method of fabrication of electrical contact structures on a semiconductor material is described comprising the steps of: depositing an oxide of a desired contact material by a chemical electroless process on a face of the semiconductor material; and reducing the oxide via a chemical electroless process to produce a contact of the desired contact material. A method of fabrication of a semiconductor device incorporating such electrical contact structures and a semiconductor device incorporating such electrical contact structures are also described.