SiC Sensor Packaging With Intermediate Bonding Layers
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Solution Overview
Problem
Current packaging methodologies for high-temperature semiconductor-based sensors and electronics, such as those using silicon carbide (SiC), face reliability issues due to weak bond strength, thermomechanical stress, and limitations in multifunctional applications, which hinder their operational reliability and commercialization in harsh environments like jet engines and automobiles.
Innovation Solution
A modular apparatus with a substrate made of dielectric materials like aluminum nitride, featuring a square recess with cavities and voltage input/output holes, and a housing configuration that allows for the integration of pressure, temperature, and signal conditioning sensors, along with buried thermocouples and acoustic impedance channels, providing environmental protection and reducing thermal expansion mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If electrostatic bonding method is used to bond SiC sensor and cover member, then bonding process is simple, but bond strength is very weak leading to debonding during thermal cycling
Solution Approach 1:
The patent introduces an intermediate bonding layer comprising a metal layer (such as platinum, palladium, or rhodium) and an oxide layer between the SiC sensor and cover member. This intermediate layer acts as a mediator that provides strong chemical bonding to both SiC surfaces while withstanding thermal cycling stresses, thereby resolving the contradiction between simple bonding process and strong bond strength.
2Ease of manufacture
If glass frits are used as adhesion material between SiC cover member and sensor wafer, then bonding is achieved, but aperture creation is necessary for outgassing which increases sealant slipping risk into reference cavity
Solution Approach 1:
The patent replaces glass frits with an intermediate bonding layer consisting of metal and oxide layers that provide adequate outgassing pathways during bonding without requiring aperture creation. This intermediate layer bonds the SiC cover member and sensor wafer while maintaining hermetic seal integrity, thereby resolving the contradiction between bonding capability and hermetic seal reliability.
3Reliability
If SiC cover member is heavily oxidized to create thick oxide envelope for preventing electrical conduction at high temperature, then electrical insulation is achieved, but oxidation process takes up to twenty-four hours and may break down during current or voltage surge
Solution Approach 1:
The patent applies a thin protective oxide layer (such as silicon dioxide) on the SiC cover member surface as a preliminary protective measure before final assembly. This thin pre-formed oxide layer provides sufficient electrical insulation at high temperatures without requiring lengthy oxidation processes, thereby resolving the contradiction between electrical insulation reliability and oxidation process time.
4Adaptability or versatility
If multiple components are coupled together in conventional packaging, then device functionality is achieved, but thermomechanically-induced stress on sensor degrades performance gradually
Solution Approach 1:
The patent employs materials with matched thermal expansion coefficients throughout the packaging structure, including the SiC sensor, cover member, and intermediate bonding layers. This material homogeneity in terms of thermal properties minimizes thermomechanical stress during temperature variations, thereby resolving the contradiction between device functionality and sensor performance stability.
5Temperature
If conventional semiconductor devices are used in high temperature environments above 300°C, then device operation is limited, but material properties and packaging constraints prevent reliable operation
Solution Approach 1:
The patent utilizes silicon carbide (SiC) as the base material for sensors and electronics, which inherently possesses superior high-temperature stability compared to conventional silicon-based semiconductors. Combined with the composite packaging structure featuring SiC cover members and specialized intermediate bonding layers, this enables reliable operation beyond 300°C by resolving the contradiction between operating temperature limit and device reliability.
Data Source
AI summary
A modular apparatus for attaching sensors and electronics is disclosed. The modular apparatus includes a square recess including a plurality of cavities and a reference cavity such that a pressure sensor can be connected to the modular apparatus. The modular apparatus also includes at least one voltage input hole and at least one voltage output hole operably connected to each of the plurality of cavities such that voltage can be applied to the pressure sensor and received from the pressure sensor.