Conductive Plate Strained LDMOSFET for Breakdown and On-Resistance
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Solution Overview
Problem
Existing LDMOSFETs face challenges in achieving high breakdown voltage and low on-resistance due to increased ILD layer thickness, which reduces the RESURF electric field strength and increases power loss.
Innovation Solution
The integration of a conductive plate below the ILD layer in strained LDMOSFETs generates a RESURF electric field, increasing the breakdown voltage and reducing on-resistance by controlling the distance between the conductive plate and the diffusion region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the ILD layer thickness is increased, then the breakdown voltage is improved, but the RESURF electric field strength is reduced and on-resistance increases
Solution Approach 1:
A conductive plate is introduced as an intermediary element between the ILD layer and the diffusion region. This conductive plate generates a RESURF electric field that maintains high breakdown voltage while preventing the increase in on-resistance that would otherwise result from thicker ILD layers. The conductive plate acts as a mediator that decouples the conflicting requirements of high breakdown voltage and low on-resistance.
Solution Approach 2:
The invention changes the electrical parameters of the structure by introducing a conductive plate with specific conductivity properties at a controlled distance from the diffusion region. By adjusting the conductivity, position, and geometry of the conductive plate, the electric field distribution is optimized to achieve both high breakdown voltage and low on-resistance simultaneously, resolving the parameter trade-off.
2Strength
If the ILD layer thickness is increased, then the breakdown voltage is improved, but power loss increases
Solution Approach 1:
The conductive plate serves as an intermediary that enables the use of thicker ILD layers for higher breakdown voltage without the penalty of increased power loss. By generating the necessary RESURF electric field, the conductive plate eliminates the direct coupling between ILD thickness and power loss, allowing independent optimization of both parameters.
3Strength
If the distance between the conductive plate and diffusion region is reduced, then the RESURF electric field strength is increased, but the breakdown voltage control becomes more difficult
Solution Approach 1:
The invention utilizes parameter changes in the conductive plate's position, geometry, and conductivity to optimize the RESURF electric field strength. By carefully controlling these parameters, the design achieves strong electric field generation while maintaining manageable breakdown voltage characteristics through systematic parameter optimization rather than ad-hoc adjustments.
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 conductive plate enhances the breakdown voltage and reduces on-resistance, effectively addressing the power/voltage level demands of high-voltage power devices while simplifying fabrication and reducing costs.
Implementation Method 1
The conductive plate can cause a RESURF electric field between the conductive plate and the second diffusion region. The RESURF electric field can generate a depletion region in the second diffusion region, which can increase the breakdown voltage
Implementation Method 2
The conductive plate can cause between about 0.1 GPa and about 3 GPa compressive and/or tensile stress in the drift region and the channel region. The strains and the stresses in the drift region and the channel region can increase carrier mobility, such as electron mobility and hole mobility
Data Source
AI summary
The present disclosure describes a structure with a conductive plate and a method for forming the structure. The structure includes a gate structure disposed on a diffusion region of a substrate, a protective layer in contact with the diffusion region and covering a sidewall of the gate structure and a portion of a top surface of the gate structure, and a first insulating layer in contact with the gate structure and the protective layer. The structure further includes a conductive plate in contact with the first insulating layer, where a first portion of the conductive plate laterally extends over a horizontal portion of the protective layer, and where a second portion of the conductive plate extends over a sidewall portion of the protective layer covering the sidewall of the gate structure. The structure further includes a second insulating layer in contact with the conductive plate.