Photodiode Substrate Extensions With Sidewall Spacers for Defect Control
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Solution Overview
Problem
The challenge in manufacturing photodiodes is forming defect-free non-silicon photo-absorption structures within silicon substrates, as silicon substrates often combine with non-silicon materials, leading to trench imperfections and incomplete filling, which limits design flexibility and efficiency in light to electrical signal conversion across various wavelengths.
Innovation Solution
The approach involves forming a full layer of photo-absorption material on a substrate base, patterning it into a photodiode, and growing substrate extensions between the non-silicon photodiode, with sidewall spacers preventing silicon extension combination with non-silicon material, allowing for flexible placement of readout circuitry and avoiding trench-related issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-silicon photo-absorption structures are formed within silicon substrates using traditional trench methods, then light to electrical signal conversion can be achieved, but substrate and non-silicon material combine leading to trench imperfections and incomplete filling
Solution Approach 1:
The structure is segmented into distinct regions: a silicon substrate base, non-silicon photo-absorption material layers formed thereon, and silicon substrate extensions grown laterally between the photodiodes. This segmentation prevents the problematic combination of silicon substrate with non-silicon material in trench structures, as the silicon extensions are grown after photodiode formation rather than forming trenches to contain the non-silicon material.
Solution Approach 2:
Instead of forming trenches in the silicon substrate to contain non-silicon photo-absorption material (traditional approach), the invention inverts the sequence: a full layer of photo-absorption material is formed on the substrate, photodiodes are patterned, and then silicon substrate extensions are grown laterally between the photodiodes. This inversion eliminates trench-related defects while achieving the same functional separation.
2Adaptability or versatility
If silicon substrates are used for photodiodes, then manufacturing is straightforward, but light wavelength range is limited to 190nm-1100nm
Solution Approach 1:
The photodetector structure uses composite materials: non-silicon photo-absorption material (such as InGaAs, Ge, or PbS) is formed in layers on the silicon substrate base. These non-silicon materials enable detection beyond the silicon wavelength limit of 1100nm, while the silicon substrate base and lateral extensions provide mechanical support and electrical connectivity. This composite approach maintains manufacturing advantages of silicon while expanding wavelength adaptability.
3Adaptability or versatility
If substrate extensions are grown to enable additional devices, then design flexibility is enhanced, but risk of silicon extension combination with non-silicon material increases
Solution Approach 1:
Sidewall spacers are formed on the photodiodes before the silicon substrate extensions are grown. These spacers act as preliminary barriers that prevent the silicon extensions from combining with the non-silicon photo-absorption material during the extension growth process. This preliminary action ensures reliable interface separation while allowing the extensions to provide the desired design flexibility for additional devices.
Solution Approach 2:
Sidewall spacers serve as intermediary structures between the photodiodes and the laterally grown silicon substrate extensions. These spacers mediate the interface, preventing direct contact and potential defect formation between silicon and non-silicon materials, while still allowing the extensions to be grown for additional device functionality.
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 consistently forms defect-free photodiodes with enhanced design flexibility, preventing substrate and non-silicon material co-planarity issues, thus improving light to electrical signal conversion efficiency across a broader range of wavelengths.
Implementation Method 1
Light (photons) can alter the electrical characteristics of photodiodes, and this allows photodiodes to convert optical signals into electrical signals
Implementation Method 2
grow a substrate extension from an exposed portion of the substrate base in processing that fills the opening with the substrate extension
Data Source
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AI summary
A structure (100) comprising a substrate (101) comprising a substrate base (102) and a substrate extension (104) grown on the substrate base; a photodiode (112) contacting the substrate base, wherein the substrate extension is adjacent the photodiode; an additional device (120) contacting the substrate extension; and a sidewall spacer (114, 116) between the photodiode and the substrate extension, wherein the additional device includes conductive elements (130, 132) within the substrate extension adjacent the sidewall spacer.