Avalanche Photodiode Fill Factor via Backside Quenching
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Solution Overview
Problem
The fill factor of semiconductor light detection elements is limited due to the arrangement of quenching resistors on the light incident surface, which restricts the increase in pixel size and number, and in back-illuminated elements, quenching resistors often need to be placed outside active regions, further reducing the fill factor.
Innovation Solution
The quenching circuits are relocated from the semiconductor substrate to a mounting substrate, allowing avalanche photodiodes to be formed without considering space for quenching circuit arrangement, and electrodes are used to connect the photodiodes to quenching circuits through bump electrodes, reducing interconnection distances and improving fill factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If quenching resistors are arranged on the light incident surface of the semiconductor substrate, then the quenching function is achieved, but the fill factor is decreased due to space occupied by quenching resistors
Solution Approach 1:
The quenching circuits are relocated from the two-dimensional plane of the light incident surface to the back surface of the semiconductor substrate, utilizing the third dimension (depth/vertical space) to resolve the space conflict. This allows the quenching circuits to be positioned outside the active pixel regions without occupying light-receiving area, thereby maintaining high fill factor while ensuring proper quenching function.
Solution Approach 2:
Bump electrodes are introduced as intermediary connection elements between the first electrodes on the light incident surface and the second electrodes on the back surface. These bump electrodes enable electrical connection through the semiconductor substrate thickness, allowing quenching circuits to be positioned on the back surface while maintaining functional connection to the avalanche photodiodes on the front surface.
2Quantity of substance
If the number of pixels is increased in back-illuminated semiconductor light detection element, then pixel size can be reduced, but quenching resistors must be arranged outside active regions, further decreasing fill factor
Solution Approach 1:
By moving quenching circuits to the back surface of the semiconductor substrate, the invention utilizes the vertical dimension to position quenching components outside the active pixel regions. This allows high-density pixel arrangements on the light incident surface without requiring additional lateral space for quenching resistors, thus maintaining high fill factor even when increasing the number of pixels.
3Ease of manufacture
If quenching circuits are arranged on the semiconductor substrate, then direct connection is achieved, but interconnection distance and resistance/capacitance influence increase
Solution Approach 1:
Bump electrodes serve as compact intermediary connection elements that provide direct electrical pathways between the avalanche photodiodes and quenching circuits. Although positioned on the back surface, the bump electrodes create short vertical connections through the substrate thickness, minimizing interconnection distance and reducing the influence of resistance and capacitance compared to lateral connections on the surface.
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 significantly enhances the fill factor of the light detection device, improving temporal resolution by minimizing the influence of resistance and capacitance in both front-illuminated and back-illuminated semiconductor light detection elements.
Implementation Method 1
a plurality of avalanche photodiodes operating in Geiger mode and formed in the semiconductor substrate
Implementation Method 2
the first electrodes and the second electrodes corresponding to the first electrodes are connected through bump electrodes
Data Source
AI summary
A light detection device 1 has a semiconductor light detection element having a semiconductor substrate, and a mounting substrate arranged as opposed to the semiconductor light detection element. The semiconductor light detection element includes a plurality of avalanche photodiodes operating in Geiger mode and formed in the semiconductor substrate, and electrodes electrically connected to the respective avalanche photodiodes and arranged on a second principal surface side of the semiconductor substrate. The mounting substrate includes a plurality of electrodes arranged corresponding to the respective electrodes on a third principal surface side, and quenching resistors electrically connected to the respective electrodes and arranged on the third principal surface side. The electrodes and the electrodes are connected through bump electrodes.