Partitioned Photodetector Isolation via Potential Barrier
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Solution Overview
Problem
Existing semiconductor photodetectors for optical disks have high manufacturing costs and impaired high-speed responsiveness due to increased capacitance at junction areas and complex epitaxial growth processes.
Innovation Solution
A semiconductor device with a light receiving portion divided into partitions, featuring an intermediate semiconductor region with low impurity concentration, a lower semiconductor region with higher impurity concentration, and a boundary semiconductor region forming a potential barrier to suppress crosstalk and improve photoelectric conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation regions are formed to reach the bottom surface of the i layer in existing photodetectors, then crosstalk between light receiving elements is suppressed, but manufacturing cost increases and high-speed responsiveness is impaired due to increased capacitance at junction areas
Solution Approach 1:
The invention extracts the isolation function from the deep junction structure and relocates it to the i layer level. By forming isolation regions that extend only into the i layer rather than through to the bottom surface, the patent separates the light receiving elements at the point where optical charge carriers are generated, eliminating the need for deep isolating structures while maintaining crosstalk suppression.
Solution Approach 2:
The i layer serves as an intermediary medium that provides both optical charge carrier generation and element isolation functions. By utilizing the intrinsic semiconductor properties of the i layer, the patent creates a natural barrier between adjacent light receiving elements without requiring additional deep junction structures, thereby reducing manufacturing complexity and capacitance.
2Reliability
If isolation regions are formed to reach the bottom surface of the i layer in existing photodetectors, then crosstalk between light receiving elements is suppressed, but high-speed responsiveness is impaired due to increased capacitance at junction areas
Solution Approach 1:
The invention extracts the isolation function from the deep junction structure and relocates it to the i layer level. By forming isolation regions that extend only into the i layer rather than through to the bottom surface, the patent separates the light receiving elements at the point where optical charge carriers are generated, eliminating the need for deep isolating structures while maintaining crosstalk suppression.
Solution Approach 2:
The invention changes the depth parameter of the isolation regions from extending to the bottom surface to extending only into the i layer. This parameter modification reduces the junction area and associated capacitance, thereby improving high-speed responsiveness while maintaining effective crosstalk suppression through the intrinsic properties of the i layer.
3Manufacturing precision
If complex epitaxial growth processes are used in existing photodetectors, then precise control of impurity concentration is achieved, but manufacturing cost increases
Solution Approach 1:
The invention merges the functions of light receiving element formation and element isolation into a single epitaxial growth process. By forming both the i layer and the isolation regions simultaneously during one growth cycle, the patent eliminates the need for separate processing steps, thereby reducing manufacturing cost while maintaining precise control of impurity concentration profiles.
Solution Approach 2:
The invention performs preliminary action by pre-defining the isolation region structures within the i layer during epitaxial growth, before any subsequent processing steps. This preliminary formation of isolation structures with controlled impurity concentrations simplifies the overall manufacturing process and reduces the number of high-precision steps required.
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
The solution reduces manufacturing costs and enhances high-speed responsiveness by minimizing crosstalk and capacitance, while maintaining high photoelectric conversion efficiency and precise detection across partitions.
Implementation Method 1
the boundary semiconductor region and the lower semiconductor region, in accordance with the second voltage, form a potential barrier against a movement of the signal electric charges between the partitions
Implementation Method 2
each of the upper semiconductor regions and the lower semiconductor region are made in a reverse bias state owing to the first voltage and the third voltage to form a depletion region in the intermediate semiconductor region
Implementation Method 3
a semiconductor device receiving a reflected light image divided into a plurality of partitions is used
Data Source
AI summary
A four-division photodetector where a formation process of an element isolation structure is simplified is provided. On a P-sub layer that is a common anode of PIN photodiodes (PIN-PD) for every partition, a high resistivity epitaxial layer that is an i layer of the PIN-PD is grown. At a boundary of the partitions, ion implantation is applied from a substrate surface to form an isolation region that is a P+ region. When a cathode region formed for every partition and the P-sub layer are reverse-biased to operate the PIN-PD, the isolation region is set at a ground potential together with the P-sub layer to operate as an anode. As a result, in the epitaxial layer at a position sandwiched between the isolation region and the P-sub layer, a potential barrier to electrons is formed. As a result, electrons generated owing to light absorption in the respective partitions can be inhibited from moving to adjacent partitions and element isolation can thus be realized.