LDMOS Field Oxide Depth Variation for Breakdown Voltage
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Solution Overview
Problem
Conventional LDMOS devices face a trade-off between breakdown voltage and on-resistance, where increasing breakdown voltage through field plate structures is limited by the thickness of the field oxide layer and the electric field strength, leading to potential breakdown issues.
Innovation Solution
A semiconductor device with a field oxidation layer and a gate region and field plate integrated structure, where contact holes penetrate into the field oxide layer with varying depths to enhance depletion and optimize breakdown voltage and on-resistance without reducing the field oxide layer thickness infinitely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the field oxide layer is reduced to enhance depletion of the drift region, then the breakdown voltage is improved, but the electric field strength between drain and gate increases causing breakdown risk
Solution Approach 1:
The patent applies local quality by creating different oxide thicknesses at different locations: a first oxide layer with greater thickness at the drain region and a second oxide layer with lesser thickness at the gate region. This spatial variation in oxide thickness allows the drain region to benefit from enhanced depletion (improving breakdown voltage) while the gate region maintains lower electric field stress (preventing breakdown), thus resolving the contradiction locally at different positions.
2Power
If the doping concentration of the drift region is increased to reduce on-resistance, then the driving capability is improved, but the breakdown voltage is reduced
Solution Approach 1:
The patent changes the parameter of oxide layer thickness to control the depletion region characteristics. By adjusting the thickness of the field oxide layer (making it thinner in the gate region compared to conventional designs), the patent modifies the electric field distribution and depletion extent, thereby optimizing both breakdown voltage and on-resistance without relying solely on doping concentration changes.
3Reliability
If the thickness of the field oxide layer is reduced infinitely to maximize depletion enhancement, then the breakdown voltage continues to increase, but the manufacturing precision and control become difficult
Solution Approach 1:
The patent segments the oxide layer into two distinct parts: a first oxide layer at the drain region and a second oxide layer at the gate region, each with different thicknesses. This segmentation allows independent optimization of each region's oxide thickness according to its specific requirements, avoiding the need for infinite thinning while maintaining manufacturing controllability and achieving the desired breakdown voltage enhancement.
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 solution effectively increases breakdown voltage and optimizes on-resistance by controlling the effective thickness of the field oxide layer, enhancing depletion and preventing breakdown, while maintaining production cost efficiency.
Implementation Method 1
the depletion of the drift region is mainly increased by using a field plate structure
Implementation Method 2
the lower the doping concentration of the drift region, the more the drift region is depleted, the higher the breakdown voltage
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, a field oxide layer, a gate region and field plate integrated structure and a plurality of contact holes. A body region and a drift region are formed in the semiconductor substrate. An active region is formed in the body region, and a drain region is formed in the drift region. A field oxide layer is located on the drift region and the drift region surrounds a part of the field oxide layer. An integrated structure including a gate region and a field plate, the integrated structure extending from above the field oxide layer to above the body region. A depth of a contact hole closer to the source region penetrating into the field oxide layer is greater than a depth of a contact hole closer to the drain region penetrating into the field oxide layer.