Stacked APD Temperature Sensing for Accurate Bias Compensation
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Solution Overview
Problem
Existing photoelectric conversion apparatuses face challenges in optimizing the characteristics of avalanche photodiodes (APDs) due to the need for additional processes like forming metal oxide semiconductor field effect transistors (MOSFETs) for temperature compensation, which complicates the manufacturing and affects the APD's output characteristics.
Innovation Solution
A photoelectric conversion apparatus with a stacked substrate configuration, where the temperature detection unit is integrated into one substrate and the temperature value generating circuit is in a separate substrate, allowing for accurate temperature compensation without requiring MOSFET formation on the APD substrate, thus optimizing the APD characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a temperature detection circuit is integrated on the same substrate as the APD array, then temperature compensation can be achieved, but the manufacturing process becomes more complex due to the need for MOSFET formation
Solution Approach 1:
The patent divides the device into two separate substrates: a first substrate containing the APD array and a second substrate containing the temperature detection unit and MOSFETs. This segmentation allows each substrate to be optimized for its specific function and manufactured using appropriate processes, then combined through stacking to achieve both temperature compensation and simplified manufacturing.
Solution Approach 2:
The patent introduces a substrate stacking structure as an intermediary solution that physically separates the APD array from the temperature detection circuitry while maintaining functional integration. The stacked configuration allows the temperature detection unit to measure temperature changes and the control circuit to adjust bias voltage, achieving temperature compensation without requiring MOSFET formation on the APD substrate.
2Reliability
If MOSFET formation process is added to the substrate for temperature detection, then temperature compensation is enabled, but the APD characteristics cannot be optimized due to unnecessary manufacturing steps
Solution Approach 1:
The patent segments the device functionality so that the APD array on the first substrate can be manufactured using optimized APD fabrication processes without MOSFET formation steps, while the temperature detection and control functions are implemented on a separate second substrate that includes the necessary MOSFETs and circuitry.
Solution Approach 2:
The patent extracts the temperature detection unit and control circuitry from the APD substrate and places them on a separate substrate. This extraction removes the unnecessary MOSFET formation process from the APD manufacturing flow, allowing the APDs to be manufactured with optimized characteristics while still enabling temperature compensation through the separated components.
3Area of stationary object
If temperature detection and signal processing are integrated on the same substrate, then device size is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent transitions from planar integration to three-dimensional stacking, placing the temperature detection unit and control circuitry on a second substrate stacked above or beside the first substrate containing the APD array. This vertical arrangement maintains a compact device footprint while simplifying manufacturing by allowing each substrate to be processed independently before assembly.
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 approach enables easier optimization and improved accuracy in temperature compensation for APDs, reducing manufacturing complexity and enhancing the apparatus's performance by separating temperature detection and signal processing, thereby improving the APD's output characteristics.
Implementation Method 1
avalanche photodiodes (APD) are known that utilize avalanche (electron avalanche) multiplication to enable detection of faint light at a single photon level
Implementation Method 2
a temperature detection unit arranged in at least one of the first substrate and the second substrate and having an output characteristic depending on a temperature
Data Source
AI summary
A photoelectric conversion apparatus includes: a first substrate including an avalanche photodiode; and a second substrate, in which the first substrate and the second substrate are stacked on each other, and further includes: a temperature detection unit arranged in at least one of the first substrate and the second substrate and having an output characteristic depending on a temperature; and a temperature value generating circuit arranged outside the first substrate and configured to convert output from the temperature detection unit into a temperature value signal that is a signal indicating temperature information.