Silicon UV Photodiode Junction Depth for Filterless Wavelength Selectivity
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Solution Overview
Problem
Conventional silicon ultraviolet photodiodes face challenges in sensitivity and efficiency due to broad wavelength sensitivity and the need for additional filters to block visible light, leading to reduced UV light transmission and increased manufacturing costs.
Innovation Solution
A silicon ultraviolet photodiode design with controlled N-type region depth and multiple PN junctions at different depths to enhance UV sensitivity, eliminating the need for filters and improving UV light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a filter is added to block visible light in silicon photodiodes, then wavelength selectivity is improved, but UV light transmission is reduced
Solution Approach 1:
The invention changes the physical parameter of the PN junction depth to less than 10 nm, creating an ultra-shallow junction that selectively detects UV light through direct bandgap transitions while naturally rejecting visible light without requiring additional filters, thus maintaining high UV transmission
Solution Approach 2:
The invention segments the detection function by creating separate regions: an ultra-shallow PN junction for UV detection and a deeper N-type conductive channel for visible light current drainage, allowing each region to specialize in its wavelength range without interfering with the other
2Productivity
If deeper PN junctions are used to increase light absorption, then detection efficiency is improved, but UV sensitivity is reduced
Solution Approach 1:
The invention optimizes the PN junction depth parameter to be ultra-shallow (less than 10 nm), which is the critical depth where UV photons are absorbed through direct bandgap transitions, maximizing UV sensitivity while the separate deep N-type channel handles visible light detection to maintain overall detection efficiency
3Measurement precision
If high band gap semiconductor materials are used for UV sensors, then UV sensitivity is improved, but compatibility with silicon circuit substrates is lost
Solution Approach 1:
The invention applies local quality by creating an ultra-shallow PN junction region with specific doping characteristics optimized for UV detection, while the rest of the substrate remains standard silicon compatible with existing CMOS circuit fabrication processes, achieving both UV sensitivity and substrate compatibility
Solution Approach 2:
The invention changes the depth parameter of the PN junction to ultra-shallow (less than 10 nm), which enables silicon to exhibit direct bandgap-like behavior for UV detection while maintaining the indirect bandgap properties for visible light rejection, all within the standard silicon substrate ecosystem
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
Enhances UV light sensitivity and efficiency by distinguishing UV light from other wavelengths without filters, allowing for high sensitivity and specificity in applications requiring precise UV detection.
Implementation Method 1
an N-type region 23 formed beneath and in contact with an upper surface of a silicon substrate 21; a P+ region 24 formed beneath and in contact with the N-type region 23
Implementation Method 2
a depth of the N-type region 23 is controlled to a predetermined depth to enhance an ultraviolet sensitivity by compensating N-type dopant impurities of an N-type implantation region by out-diffused P-type dopant impurities of a P+ implantation region through a thermal process step
Implementation Method 3
an N-type conductive channel 25, which is connected to the deep N-well region 22, and is configured to operably drain a non-ultraviolet current caused by electron-hole pairs generated by the incident light LT1
Data Source
AI summary
The present invention provides a silicon ultraviolet photodiode and a manufacturing method thereof. The silicon ultraviolet photodiode includes: an N-type region formed beneath and in contact with an upper surface of a silicon substrate; a P+ region formed beneath and in contact with the N-type region; a deep N-well region formed beneath and in contact with the P+ region; and an N-type conductive channel, which is connected to the deep N-well region, and is configured to operably drain a non-ultraviolet current caused by electron-hole pairs formed in the deep N-well region; wherein a depth of the N-type region is controlled to a predetermined depth to enhance an ultraviolet sensitivity by compensating N-type dopant impurities of an N-type implantation region by out-diffused P-type dopant impurities of a P+ implantation region through a thermal process step.