Deep Trench Isolation for RF IC Substrate Loss Reduction
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Solution Overview
Problem
The formation of a low-resistance layer between a high-resistance substrate and a buried oxide layer in integrated circuits leads to degradation of radio frequency performance due to eddy-current losses and unacceptable insertion losses, affecting the quality factor of inductors and transmission lines.
Innovation Solution
A deep trench is formed through the low-resistance layer, accompanied by the creation of an implant region and a polysilicon layer beneath the trench to block electron migration, thereby reducing insertion losses and eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a low-resistance layer is formed between the substrate and buried oxide layer, then manufacturing compatibility is improved, but radio frequency performance deteriorates due to eddy-current losses and insertion losses
Solution Approach 1:
The low-resistance layer is segmented by forming deep trenches that divide it into isolated regions. This segmentation prevents continuous electron migration paths, reducing eddy-current losses while maintaining the layer's overall presence for manufacturing compatibility.
Solution Approach 2:
portions of the low-resistance layer are removed through deep trench formation to eliminate the harmful eddy-current paths. The extracted regions are replaced with high-resistance material, preserving the layer's manufacturing benefits while removing its harmful RF effects.
2Reliability
If a deep trench is formed through the low-resistance layer, then radio frequency performance is improved by reducing eddy currents, but device complexity increases
Solution Approach 1:
Deep trenches are formed only in specific local regions where RF performance is critical, rather than uniformly across the entire low-resistance layer. This localized approach improves RF performance where needed while minimizing the increase in overall device complexity.
3Reliability
If an implant region and polysilicon layer are formed to block electron migration, then insertion losses are reduced, but manufacturing process complexity increases
Solution Approach 1:
The implant region and polysilicon layer are formed in advance during the manufacturing process to pre-establish electron migration barriers. This preliminary action ensures RF performance requirements are met before final device assembly, integrating the solution into the existing manufacturing flow.
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 solution effectively decreases unexpected insertion losses and eddy currents, improving the radio frequency performance of integrated circuits by blocking electron migration and enhancing the isolation between the substrate and RF devices.
Implementation Method 1
an implant region and a polysilicon layer are formed beneath the trench to block electron migration
Data Source
AI summary
A method for forming a radio frequency area of an integrated circuit are provided. The method includes forming a buried oxide layer over a substrate, and an interface layer is formed between the substrate and the buried oxide layer. The method also includes etching through the buried oxide layer and the interface layer to form a deep trench, and a bottom surface of the deep trench is level with a bottom surface of the interface layer. The method further includes forming an implant region directly below the deep trench and forming an interlayer dielectric layer in the deep trench.