LDMOSFET Body Region Layout for Threshold Voltage Tuning
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Solution Overview
Problem
Existing semiconductor devices with LDMOSFETs face challenges in adjusting threshold voltage without increasing manufacturing costs, particularly when forming MISFETs with different threshold voltages on the same substrate, as current methods like channel-dope ion implantation require additional steps and can affect impurity concentration distributions.
Innovation Solution
The semiconductor device incorporates a p-type body region and a p-type body contact region with varying widths in alternating regions of the substrate, allowing for the adjustment of threshold voltage by altering the dimensions of these regions, enabling the formation of LDMOSFETs with different threshold voltages in a single manufacturing step without increasing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If channel-dope ion implantation is used to adjust threshold voltage, then threshold voltage can be adjusted, but manufacturing cost increases and impurity concentration distribution is affected
Solution Approach 1:
The patent applies local quality by creating body regions with different impurity concentrations in specific local areas beneath the gate electrode. By controlling the impurity concentration distribution locally in the body region rather than uniformly across the channel, the threshold voltage can be adjusted without requiring additional ion implantation steps. This local differentiation of impurity concentration achieves threshold voltage control while maintaining manufacturing simplicity.
Solution Approach 2:
The patent implements preliminary action by pre-forming body regions with different impurity concentrations during the substrate preparation phase, before the gate electrode is formed. This preliminary structuring of the body region allows threshold voltage adjustment to be built into the device architecture itself, eliminating the need for subsequent ion implantation steps that would increase manufacturing cost and complexity.
2Adaptability or versatility
If multiple LDMOSFETs with different threshold voltages are formed on the same substrate, then device versatility is improved, but manufacturing complexity increases
Solution Approach 1:
The patent creates multiple LDMOSFETs with different threshold voltages on the same substrate by introducing body regions with different impurity concentrations at different locations. Each LDMOSFET has its body region engineered with specific impurity concentration characteristics that determine its threshold voltage. This local differentiation allows multiple threshold voltage values to coexist on a single substrate without requiring separate manufacturing processes for each device type.
Solution Approach 2:
The patent segments the substrate into multiple regions, each with different body region impurity concentration characteristics. By dividing the substrate into distinct areas with tailored impurity profiles, the patent enables the formation of multiple LDMOSFETs with different threshold voltages. Each segment of the substrate is optimized for a specific threshold voltage requirement, allowing versatile device fabrication in a single manufacturing run.
Data Source
AI summary
In a p-type substrate region of a semiconductor substrate, an n-type source region, an n-type drain region, a p-type body region having an impurity concentration higher than an impurity concentration of the p-type substrate region, a p-type body contact region having an impurity concentration higher than the impurity concentration of the p-type body region, and an n-type drift region having an impurity concentration lower than an impurity concentration of the n-type drain region are formed. A gate electrode is formed on the semiconductor substrate via a gate dielectric film. The semiconductor substrate includes a first region and a second region that are alternately disposed in an extending direction of the gate electrode. A width of the p-type body region overlapping with the gate electrode in the second region is smaller than a width of the p-type body region overlapping with the gate electrode in the first region.