Infrared Imaging Diode Layout for Lower Minority Carrier Noise
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional infrared solid state imaging devices using silicon PN junction diodes suffer from increased noise due to minority carrier injection and recombination issues, particularly at bent portions of connected PN junction diodes, leading to insufficient sensitivity for infrared detection.
Innovation Solution
The proposed solution involves configuring the infrared solid state imaging device with a specific arrangement of PN junction diodes, where the shortest lengths between junction surfaces within N-type and P-type regions are set to differ, and element isolation regions are provided to reduce noise by enhancing carrier recombination within each region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PN junction diodes are connected in series with bent portions to increase the number of diodes in limited area, then the sensitivity for infrared detection is improved, but noise increases due to minority carrier injection and recombination at bent portions
Solution Approach 1:
The patent applies local quality by creating an asymmetric structure where the N-type region has a longer shortest length than the P-type region at the bent portion. This local differentiation in dimensions针对性地 addresses the noise problem at the bent portion while maintaining the series connection configuration for sensitivity enhancement.
Solution Approach 2:
The patent implements asymmetry by deliberately designing the N-type region with a longer shortest length compared to the P-type region at the bent portion. This asymmetric configuration breaks the symmetry that causes equal and problematic carrier injection from both regions, thereby reducing noise while preserving the series connection benefits.
2Measurement precision
If PN junction diodes are connected in series to improve infrared detection sensitivity, then the temperature change detection capability is enhanced, but the device complexity increases
Solution Approach 1:
The patent merges multiple PN junction diodes into a series connection configuration where they share common regions (the N-type and P-type regions at the bent portion). This merging approach allows multiple diodes to be connected in series while reducing overall structural complexity by eliminating redundant isolation structures between adjacent diodes.
3Ease of manufacture
If the shortest lengths between junction surfaces are made equal in N-type and P-type regions, then the manufacturing process is simplified, but noise increases due to balanced minority carrier injection from both regions
Solution Approach 1:
The patent deliberately introduces asymmetry by setting the shortest length of the N-type region to be longer than that of the P-type region. This asymmetric design breaks the balance in minority carrier injection from both regions, preventing the constructive interference of noise signals while remaining manufacturable through standard semiconductor processes.
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 effectively reduces noise during infrared detection by optimizing carrier recombination, thereby improving the sensitivity of the infrared solid state imaging device.
Implementation Method 1
An infrared solid state imaging device including thermal infrared detection elements as pixels absorbs infrared rays, converts the infrared rays into heat, outputs a temperature change caused by the heat as an electrical signal
Implementation Method 2
converts the infrared rays into heat, outputs a temperature change caused by the heat as an electrical signal
Implementation Method 3
detects a temperature change in the amount of a voltage drop in a forward direction of silicon PN junction diodes
Implementation Method 4
element isolation regions are provided between the first region and the third region, and between the second region and the fourth region
Data Source
Figure 1~2
Figure 3~4
Figure 5(a)~5(e)
AI summary
An infrared solid state imaging device includes: a PN junction diode (D1) that has a region (50) having a first conductivity type, and a region (52) having a second conductivity type which is in contact with the region (50) at a junction surface (70) and which has a first shortest length (Ln) that is a shortest length from the junction surface (70) to a junction surface (72); a PN junction diode (D2) that has a region (54) having the first conductivity type which is in contact with the region (52) at the junction surface (72) and which has a second shortest length (Lp) that is a shortest length from the junction surface (72) to a junction surface (74), the second shortest length being different from the first shortest length, and a region (56) having the second conductivity type which is in contact with the region (54) at the junction surface (74); an insulating film (20) serving as an element isolation region which establishes electrical isolation between the region (50) and the region (56), between the region (50) and the region (54), and between the region (52) and the region (56); and a metal wire provided on the region (52) and the region (54), wherein the PN junction diode (D1) and the PN junction diode (D2) are connected in series.