Integrated Germanium Photodiode Domed Structure for Light Focusing
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Solution Overview
Problem
Conventional photodiodes with separate light focusing elements suffer from inefficient light coupling and increased cross-talk due to non-absorbing optical paths, leading to reduced signal-to-noise ratio and higher costs in manufacturing.
Innovation Solution
A trench photodiode with an integrated domed structure and doped material having a concave underside surface, where the doped material extends to the side of the photodiode, allowing for self-aligned light focusing without blocking light entry, and contacts are formed on the side to avoid obstructing light, using semiconductor materials like germanium and polysilicon.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a separate microlens is used to focus light into the photodiode, then light focusing capability is improved, but light loss and degradation occur due to non-absorbing optical paths
Solution Approach 1:
The patent merges the microlens structure directly with the photodiode absorber by forming the domed structure from the same semiconductor material (germanium) as the photodiode. This integration eliminates the non-absorbing optical path between separate components, allowing light to be focused and absorbed continuously without loss at material interfaces.
2Area of moving object
If the photodiode active area is reduced to achieve smaller pixel size, then pixel density is improved, but cross-talk increases and signal-to-noise ratio deteriorates
Solution Approach 1:
The domed structure is integrated directly with the photodiode absorber, creating a unified optical path that efficiently channels light into the active area. This integration improves light coupling efficiency, which enhances the signal-to-noise ratio and reduces cross-talk by ensuring that light is precisely directed into the intended photodiode pixel, even when pixels are closely spaced.
3Illumination intensity
If a separate microlens structure is implemented, then light focusing is improved, but manufacturing complexity and cost increase due to extra fabricating steps
Solution Approach 1:
The patent combines the microlens domed structure and photodiode absorber into a single integrated component made from the same germanium material. This eliminates the need for separate fabrication steps for mounting and aligning a discrete microlens, thereby reducing manufacturing complexity and cost while maintaining effective light focusing capability.
4Reliability
If germanium photodiode material is used to improve absorption, then light absorption capability is improved, but smaller pitch leads to increased cross-talk
Solution Approach 1:
The integrated domed structure made from germanium material works in unison with the germanium photodiode absorber to create a unified optical system. This integration ensures that the high absorption capability of germanium is fully utilized while the domed shape directs light precisely into the active area, reducing cross-talk even at smaller pitches.
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 configuration enhances the signal-to-noise ratio and reduces cross-talk, enabling smaller active area pixel arrays with improved light focusing and reduced manufacturing complexity and cost.
Implementation Method 1
A microlens can be used to focus light into the photodiode material
Implementation Method 2
A photodiode is a semiconductor device that converts light into an electrical current
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to a photodiode with an integrated, light focusing elements and methods of manufacture. The structure includes: a trench photodiode comprising a domed structure; and a doped material on the domed structure, the doped material having a concave underside surface.