Monolithic Solar Cell Integration on SOI Substrate
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Solution Overview
Problem
The voltage output of standalone silicon-based solar cells is insufficient to drive high-performance transistors, limiting their ability to power advanced CMOS devices, and existing solutions for increasing voltage require additional power or prime silicon real estate.
Innovation Solution
Monolithic integration of solar cells on a silicon-on-insulator substrate with controlled spalling technology to create a thin handle layer, allowing for serial connection of solar cells to increase voltage output while maintaining mechanical support and avoiding prime silicon usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If standalone silicon-based solar cells are used, then the structure is simple, but the voltage output is insufficient to drive high-performance transistors
Solution Approach 1:
The solar cell substrate is divided into multiple segments (first solar cell, second solar cell, third solar cell) connected in series. Each segment generates voltage, and the series connection multiplies the total voltage output, solving the insufficient voltage problem while maintaining reasonable structural complexity
Solution Approach 2:
Multiple solar cell structures are merged into a single integrated device on the silicon-on-insulator substrate. The series connection of multiple solar cells combines their voltage outputs to achieve sufficient power for driving high-performance transistors
2Power
If large area CMOS diodes are used as photovoltaic components, then the power output is sufficient, but the use of advanced CMOS technology is inhibited
Solution Approach 1:
The photovoltaic function is moved from the prime silicon substrate (where CMOS devices should be located) to the handle substrate dimension. This allows advanced CMOS technology to be used on the semiconductor layer while the solar cell structures are formed in the handle substrate, achieving both sufficient power output and CMOS compatibility
3Power
If multiple solar cells are connected in series to increase voltage, then the power output is sufficient, but additional power requirements or prime silicon usage is needed
Solution Approach 1:
The handle substrate, which traditionally serves only as mechanical support, is given a dual function by forming solar cell structures within it. This allows the handle substrate to generate power while the prime silicon substrate is reserved exclusively for CMOS devices, eliminating the need for additional silicon usage
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 efficient monolithic integration of solar cells with integrated circuits, providing sufficient power for low-power CMOS technology and facilitating the isolation and serial connection of solar cells to enhance voltage output, suitable for energy-autonomous devices.
Implementation Method 1
solar cell structures connected in series
Implementation Method 2
cleaving through the handle substrate by exerting a force on the flexible handle layer
Data Source
AI summary
A solar-powered autonomous CMOS circuit structure is fabricated with monolithically integrated photovoltaic solar cells. The structure includes a device layer including an integrated circuit and a solar cell layer. Solar cell structures in the solar cell layer can be series connected during metallization of the device layer or subsequently. The device layer and the solar cell layer are formed using a silicon-on-insulator substrate. Subsequent spalling of the silicon-on-insulator substrate through the handle substrate thereof facilitates production of a relatively thin solar cell layer that can be subjected to a selective etching process to isolate the solar cell structures.