Hermetic Cavity Integrated Circuit Reduces Parasitic Coupling
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Solution Overview
Problem
The use of silicon-on-insulator (SOI) MOS transistors in RF switches for RF FEMs leads to increased parasitic capacitive coupling, which affects switching performance and is difficult to eliminate, thereby impacting the overall performance of the integrated circuit.
Innovation Solution
The integration of a hermetic cavity between the gate electrodes of adjacent transistors reduces parasitic coupling capacitance by providing a low dielectric constant between the drain and gate electrodes, improving the performance of the integrated circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If SOI MOS transistors are used to replace GaAs semiconductor transistors in RF switches, then manufacturing and packaging costs are reduced, but parasitic capacitive coupling between electrodes and substrate increases
Solution Approach 1:
The patent introduces a hermetic cavity as an intermediary structure between the drain electrode and gate electrode. This cavity is formed by removing a sacrificial dielectric layer and sealing the resulting space, creating a physical separation that reduces parasitic capacitive coupling. The hermetic cavity acts as a mediator that maintains the benefits of SOI MOS technology while mitigating its parasitic effects.
Solution Approach 2:
The patent changes the dielectric parameter between the drain and gate electrodes by replacing the solid dielectric material with a hermetic cavity (air or vacuum). This parameter change from high dielectric constant material to low dielectric constant medium (air/vacuum) directly reduces the parasitic capacitive coupling, improving RF switch performance while maintaining cost advantages of silicon-based technology.
2Object-generated harmful factors
If hermetic cavities are introduced to reduce parasitic capacitance, then parasitic capacitive coupling is reduced, but device structure and manufacturing process become more complex
Solution Approach 1:
The hermetic cavity is formed during the transistor fabrication process itself, before final device assembly. A sacrificial dielectric layer is removed and the cavity is sealed using the same processing steps employed for transistor formation. This preliminary action integrates the parasitic reduction feature into the base manufacturing flow, avoiding the need for separate post-fabrication cavity formation and sealing operations.
Solution Approach 2:
The patent merges the hermetic cavity formation process with the existing transistor fabrication process. The sacrificial dielectric layer removal, cavity formation, and sealing steps are combined with standard CMOS or SOI processing steps. This merging approach allows the complex hermetic cavity structure to be implemented using conventional manufacturing equipment and processes, reducing the actual increase in device complexity.
3Object-generated harmful factors
If hermetic cavities are introduced to reduce parasitic capacitance, then parasitic capacitive coupling is reduced, but manufacturing process steps increase
Solution Approach 1:
The hermetic cavity is formed during the transistor fabrication process itself, before final device assembly. A sacrificial dielectric layer is removed and the cavity is sealed using the same processing steps employed for transistor formation. This preliminary action integrates the parasitic reduction feature into the base manufacturing flow, avoiding the need for separate post-fabrication cavity formation and sealing operations.
Solution Approach 2:
The manufacturing process is designed to form hermetic cavities using the same equipment and material layers already present in the transistor fabrication sequence. The sacrificial dielectric layer that is removed during transistor formation is reused as the cavity sealant material, allowing the process to be self-sufficient without requiring additional specialized equipment or materials. This self-service approach minimizes the impact on manufacturing productivity.
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
The implementation of hermetic cavities between the gate electrodes of transistors in the integrated circuit effectively reduces parasitic capacitive coupling, enhancing the performance of RF switches and the overall RF FEM by minimizing signal distortion and maintaining high signal fidelity.
Implementation Method 1
A low dielectric can be obtained between the drain electrode and the gate electrode using the hermetic cavities. Accordingly, the parasitic coupling capacitance between the drain electrode and the gate electrode can be reduced
Data Source
AI summary
An integrated circuit includes a semiconductor substrate, and at least two transistors connected in series on the semiconductor substrate, wherein each transistor shares a source electrode or a drain electrode with an adjacent transistor. The integrated circuit also includes a hermetic cavity disposed on the source electrode and the drain electrode, between gate electrodes of adjacent transistors. The source electrode disposed at a first end portion of the series of transistors is in direct contact with a source interconnect, and the drain electrode disposed at a second end portion of the series of transistors is in direct contact with a drain interconnect.