Avalanche Photodiode Anode Electrode with Uniform CVD Doping
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Solution Overview
Problem
Imaging devices using avalanche photodiodes face challenges in forming uniform anode electrodes due to variations in impurity concentration during ion implantation, leading to non-uniform resistance values and deteriorated device characteristics.
Innovation Solution
The use of a P-type semiconductor with a refractive index of 1.8 or larger and an optical bandgap of 1.9 eV or larger, such as P-type amorphous silicon carbide or polysilicon carbide, for the anode electrode, formed by chemical vapor deposition with in-situ doping, ensures uniform impurity concentration and reduced resistance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If multistage ion implantation is used to form the anode electrode, then the anode electrode can be formed in the semiconductor, but the impurity concentration becomes non-uniform, causing resistance value variation and characteristic deterioration
Solution Approach 1:
The patent changes the formation method of the anode electrode from ion implantation to in-situ doped film formation by CVD. This parameter change in the manufacturing process enables uniform impurity concentration distribution throughout the film thickness, resolving the contradiction between ease of manufacture and manufacturing precision.
Solution Approach 2:
The patent replaces the mechanical ion implantation process with a chemical vapor deposition process for forming the anode electrode. This substitution eliminates the depth-directional variation in impurity concentration that occurs with ion implantation, achieving uniform impurity distribution while maintaining manufacturing feasibility.
2Ease of manufacture
If ion implantation is used for anode electrode formation, then the electrode can be created, but resistance value varies due to non-uniform impurity concentration, deteriorating imaging device characteristics
Solution Approach 1:
The patent changes the formation method from ion implantation to in-situ doped CVD film formation. This parameter change ensures uniform impurity concentration in the anode electrode, which stabilizes resistance values and improves the reliability and consistency of imaging device characteristics across multiple pixels.
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 the uniformity of the anode electrode's resistance, stabilizes the imaging device's characteristics, and improves sensitivity by maintaining a consistent impurity concentration across pixels.
Implementation Method 1
a light absorbing region (photoelectric conversion region) provided closer to the light incident surface than the P-type semiconductor region
Implementation Method 2
An avalanche amplification region is formed on a PN junction surface between the N-type semiconductor region and the P-type semiconductor region described above. Electrons generated by photoelectric conversion in the light absorbing region propagate to the avalanche amplification region and are subjected to avalanche amplification.
Data Source
AI summary
Provided are an imaging device and an electronic device capable of suppressing deterioration in characteristic. An imaging device is provided with an N-type first semiconductor region, a P-type second semiconductor region in contact with one surface of the first semiconductor region, a light absorbing region provided on a side opposite to the first semiconductor region across the second semiconductor region, and an anode electrode provided at a position facing the second semiconductor region across the light absorbing region. The anode electrode includes a P-type semiconductor having a refractive index of 1.8 or larger and an optical bandgap of 1.9 eV or larger.