LDMOS Drift-Region Workfunction Metal Layout for Low Leakage
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Solution Overview
Problem
LDMOS devices face challenges in achieving high drain-source breakdown voltage (BVDSS) and reducing leakage current, which limits their performance in high-power applications such as RF power amplifiers.
Innovation Solution
Incorporating a gate structure with a first n-type workfunction metal in the channel region and a second p-type workfunction metal in the trench of the drift region, along with a sidewall spacer, to enhance the electric field accumulation and current handling capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LDMOS fabrication with ion implantation is used, then the drift region can withstand high electric fields, but leakage current increases and breakdown voltage decreases
Solution Approach 1:
The patent applies different workfunction metals to different regions: n-type workfunction metal in the channel region and p-type workfunction metal in the drift region trench. This local differentiation optimizes each region's electrical characteristics, reducing leakage current while maintaining high breakdown voltage capability.
Solution Approach 2:
The p-type workfunction metal in the drift region acts as an intermediary that accumulates electric field in a controlled manner, preventing harmful leakage paths while maintaining the high electric field withstand capability needed for high-power operation.
2Reliability
If higher breakdown voltage is achieved through ion implantation, then electric field withstand capability improves, but current handling capability decreases
Solution Approach 1:
By placing n-type workfunction metal specifically in the channel region, the patent enhances current handling capability where needed, while the p-type metal in the drift region maintains electric field withstand capability. This localized optimization resolves the trade-off between voltage and current handling.
Solution Approach 2:
The gate structure combines n-type and p-type workfunction metals in a composite configuration, leveraging the complementary properties of each material type to simultaneously achieve high breakdown voltage and high current handling capability.
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 proposed structure improves drain-source breakdown voltage and reduces leakage current, enabling LDMOS devices to handle higher currents with lower breakdown voltage, making them suitable for high-power applications like RF power amplifiers.
Implementation Method 1
a gate structure with a first n-type workfunction metal in the channel region and a second p-type workfunction metal in the trench of the drift region
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to a device with workfunction metal in a drift region and methods of manufacture. The structure includes: a gate structure having at least a first workfunction metal in a channel region and a second workfunction metal, which is different from the first workfunction metal, in a trench in a drift region; and a sidewall spacer adjacent to the gate structure within the trench in the drift region.