Microbolometer CMOS Integration via Substrate Cavity
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Solution Overview
Problem
Microbolometer devices integrated with CMOS and BiCMOS technologies face challenges in achieving efficient thermal isolation and integration without the need for additional Readout Integrated Circuit (ROIC), limiting their performance and manufacturing complexity.
Innovation Solution
The method involves forming a damaged region on a substrate, depositing infrared (IR) absorbing material, and creating a cavity underneath to isolate the material, allowing for electrical connection and integration with CMOS technologies, thereby eliminating the need for a separate ROIC and enhancing both active and passive device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If microbolometer devices are integrated with CMOS and BiCMOS technologies, then manufacturing complexity is reduced and device performance is improved, but thermal isolation becomes more difficult to achieve
Solution Approach 1:
The substrate is segmented into a sensor region and a common region, with the sensor region further divided into multiple unit cells. Each unit cell contains an IR absorbing material on a damaged region with a cavity underneath, creating localized thermal isolation zones that maintain thermal independence while enabling CMOS integration.
Solution Approach 2:
A sacrificial material layer is introduced as an intermediary during fabrication. This sacrificial layer is deposited over the IR absorbing material, then removed through vias to create cavities. The sacrificial material serves as a temporary mediator that enables precise cavity formation and thermal isolation, which would be difficult to achieve directly in integrated CMOS processing.
2Ease of operation
If a separate Readout Integrated Circuit (ROIC) is used, then readout functionality is provided, but device complexity and manufacturing steps increase
Solution Approach 1:
The sensor region is merged with the common region on the same substrate, eliminating the need for a separate ROIC chip. The common region contains shared circuitry that serves all unit cells in the sensor region, integrating readout functionality directly into the microbolometer device structure and reducing overall system complexity.
Solution Approach 2:
The common region provides universal readout functionality for all unit cells in the sensor region. This multi-functional area handles signal processing and readout for the entire array, eliminating the need for individual readout circuits for each pixel and reducing the overall number of components required.
3Ease of manufacture
If IR absorbing material is deposited directly on the substrate, then manufacturing is simplified, but thermal isolation performance deteriorates
Solution Approach 1:
The substrate is pre-damaged in the sensor region before depositing the IR absorbing material. This preliminary damage creates a distinct region that defines where the IR material will be deposited and establishes the boundaries for subsequent cavity formation, ensuring proper thermal isolation is built into the structure from the beginning of the fabrication process.
Solution Approach 2:
The sacrificial material is selectively removed through vias to extract material and create cavities underneath the IR absorbing material. This extraction process creates the necessary void space for thermal isolation, separating the IR absorbing material thermally from the substrate while maintaining a relatively simple fabrication sequence.
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 improved performance of microbolometer devices by providing thermal isolation and integrating IR absorbing materials with CMOS technologies, simplifying manufacturing and eliminating the need for additional readout circuits, thus enhancing both passive and active device performance.
Implementation Method 1
forming infrared (IR) absorbing material on the damaged region
Implementation Method 2
isolating the IR absorbing material by forming a cavity underneath the IR absorbing material
Data Source
AI summary
A microbolometer device integrated with CMOS and BiCMOS technologies and methods of manufacture are disclosed. The method includes forming a microbolometer unit cell, comprises damaging a portion of a substrate to form a damaged region. The method further includes forming infrared (IR) absorbing material on the damaged region. The method further includes isolating the IR absorbing material by forming a cavity underneath the IR absorbing material.