Oversized Local Contact Faraday Shield for RF Isolation
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Solution Overview
Problem
As semiconductor device dimensions shrink, existing Faraday shields in RF power amplifiers, such as LDMOS devices, struggle to provide effective shielding while maintaining cost-efficiency and timely manufacturing, leading to inadequate mitigation of hot carrier injection and reverse transfer capacitance.
Innovation Solution
The implementation of an oversized local contact as a Faraday shield, positioned above the source region conductor and gate electrode, with a drain-side edge extending beyond the gate electrode, coupled to a primary metallization layer, effectively reduces the electric field and reverse transfer capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional Faraday shield dimensions are used, then manufacturing cost and timing are improved, but shielding effectiveness deteriorates
Solution Approach 1:
The patent changes the dimensional parameters of the Faraday shield by extending its drain-side edge beyond the gate electrode's drain-side edge. This parameter modification increases the shield's overlap with the gate, improving shielding effectiveness against hot carrier injection and reverse transfer capacitance without requiring complete redesign of the manufacturing process
Solution Approach 2:
The patent addresses shielding effectiveness in the lateral dimension by extending the Faraday shield's width beyond the gate electrode. This dimensional extension creates additional overlap area that enhances the shield's ability to mitigate electric field effects while maintaining compatibility with existing manufacturing processes
2Reliability
If Faraday shield is extended to improve shielding, then hot carrier injection mitigation is improved, but device complexity increases
Solution Approach 1:
The patent merges the Faraday shield function with the existing local contact structure. By forming the Faraday shield as an extension of the local contact that connects to the source region, the design combines two functional elements into a single integrated structure, reducing overall device complexity while achieving improved shielding
Solution Approach 2:
The extended Faraday shield structure serves multiple functions simultaneously: it provides hot carrier injection mitigation, reduces reverse transfer capacitance, and maintains electrical connection to the source region. This multi-functionality reduces the need for separate structures, thereby reducing overall device complexity
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 configuration significantly reduces the electric field at the drain-side of the gate electrode and decreases reverse transfer capacitance by over 73%, enhancing RF performance and manufacturing efficiency.
Implementation Method 1
a Faraday shield positioned above the source region conductor and the gate electrode
Implementation Method 2
to reduce the reverse transfer capacitance (Cgd—gate to drain capacitance), thereby improving RF performance
Data Source
AI summary
This application is directed to a semiconductor device with an oversized local contact as a Faraday shield, and methods of making such a semiconductor device. One illustrative device disclosed herein includes a transistor comprising a gate electrode and a source region, a source region conductor that is conductively coupled to the source region, a Faraday shield positioned above the source region conductor and the gate electrode and a first portion of a first primary metallization layer for an integrated circuit device positioned above and electrically coupled to the Faraday shield.