Non-Uniform Doping Gate Electrodes for HVMOS Leakage Reduction
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Solution Overview
Problem
Conventional high-voltage metal-oxide-semiconductor (HVMOS) devices suffer from soft breakdown and high leakage currents when operated at high drain-source voltages, necessitating a reduction in on-state resistances and leakage currents.
Innovation Solution
The semiconductor structure features a gate electrode with distinct impurity concentrations in different portions, where a first portion has a lower impurity concentration than a second portion, and includes a semiconductor substrate with high-voltage well regions of opposite conductivity types, a gate dielectric extending between these regions, and a drain region heavily doped with a p-type impurity, along with an insulation region and source region, to reduce leakage currents and on-state resistances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional symmetric or asymmetric HVMOS device structure is used, then the device can operate at high drain-source voltages, but soft breakdown occurs and leakage currents increase
Solution Approach 1:
The gate electrode is divided into two portions with different doping concentrations: a first portion with lower doping concentration and a second portion with higher doping concentration. This local differentiation allows the gate electrode to simultaneously reduce leakage current (through the lightly-doped first portion) and maintain good ohmic contact with the source and drain regions (through the heavily-doped second portion), thereby resolving the contradiction between reliability and harmful leakage effects.
2Reliability
If conventional HVMOS device structures are used, then high voltage operation is achieved, but on-state resistances are high
Solution Approach 1:
The gate electrode employs non-uniform doping with a first portion having lower doping concentration and a second portion having higher doping concentration. The heavily-doped second portion provides low resistance path for current flow, reducing on-state resistance, while the overall gate structure maintains high voltage sustaining capability through the underlying well region design.
Solution Approach 2:
The doping concentration parameter of the gate electrode is changed from uniform to non-uniform distribution. By varying the doping concentration across different portions of the gate electrode, the invention optimizes both the on-state resistance (through higher doping in the second portion) and the voltage sustaining capability (through the structured well regions), resolving the contradiction between these two parameters.
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 leakage currents and on-state resistances, preventing soft breakdown and enhancing the overall performance of HVMOS devices by optimizing the impurity concentrations and well region structures.
Implementation Method 1
The gate electrode includes a first portion directly over the second well region, and a second portion directly over the first well region. The first portion has a first impurity concentration lower than a second impurity concentration of the second portion.
Data Source
AI summary
A semiconductor structure includes a semiconductor substrate; a first high-voltage well (HVW) region of a first conductivity type overlying the semiconductor substrate; a second well region of a second conductivity type opposite the first conductivity type overlying the semiconductor substrate and laterally adjoining the first well region; a gate dielectric extending from over the first well region to over the second well region; a drain region in the second well region; a source region on an opposite side of the gate dielectric than the drain region; and a gate electrode on the gate dielectric. The gate electrode includes a first portion directly over the second well region, and a second portion directly over the first well region. The first portion has a first impurity concentration lower than a second impurity concentration of the second portion.