LDMOS Drain Doped Region for Heat Concentration
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Solution Overview
Problem
Existing laterally diffused metal oxide semiconductor (LDMOS) and field drift metal oxide semiconductor (FDMOS) transistors face challenges in robustness and electrical performance due to inefficient current flow and local heat concentration, which can lead to device shutdown, especially under high voltage conditions.
Innovation Solution
The transistors are designed with a doped region of a first conductive type located under the drain region but not directly below the drain contact, allowing current to flow efficiently to the drain contact while preventing local heat concentration by blocking currents from other parts of the drain region, thereby enhancing device robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If current flows through all parts of the drain region, then current distribution is more uniform, but local heat concentration occurs causing device shutdown
Solution Approach 1:
The patent introduces a doped region with first conductive type in specific areas of the drain region to create non-uniform electrical properties. This doped region has higher conductivity and selectively guides current flow, preventing concentration in specific high-heat areas while maintaining overall current flow. The local modification of electrical properties through doping resolves the contradiction by redirecting current paths to avoid hot spots.
2Reliability
If a doped region is added under the drain region, then current flow efficiency improves and heat concentration is prevented, but device structure becomes more complex
Solution Approach 1:
The doped region is merged with the existing drain region structure, forming an integrated component rather than a separate added element. The doped region shares the same physical space and functional role as the drain region, combining current guiding and heat dissipation functions within a single structural element. This merging approach improves reliability without proportionally increasing device complexity.
3Temperature
If current is concentrated to flow only through the drain region directly below the drain contact, then heat concentration is prevented, but current flow path becomes more restricted
Solution Approach 1:
The doped region acts as an intermediary element that mediates between the drain contact and the bulk drain region. It provides a controlled interface that directs current flow into specific pathways, ensuring efficient current collection at the contact while guiding current away from heat-prone areas. The intermediary doped region maintains current flow efficiency by providing low-resistance paths while preventing harmful concentration effects.
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 design improves the electrical performance and robustness of the devices, enabling higher voltage handling capabilities such as a machine model (MM) value of 800V and human body model (HBM) value of 8 kV, compared to previous designs which typically achieve 300V and 4 kV respectively.
Implementation Method 1
currents flowing from a source region to a drain region can be concentrated in an efficient way. The currents can be concentrated and flow to the drain contact only through the drain region directly below the drain contact
Implementation Method 2
Local heat concentration, which would cause the device to shut down, can be prevented
Data Source
AI summary
A laterally diffused metal oxide semiconductor (LDMOS) is provided. A substrate has a deep well with a second conductive type therein. A gate is disposed on the substrate. A first doped region of a second conductive type and a second doped region of a first conductive type are located in the deep well and at the corresponding two sides of the gate. A drain region of a second conductive type is located in the first doped region. A drain contact is disposed on the drain region. A doped region of a first conductive type is located in the first doped region and under the drain region but not directly below the drain contact. A source region is located in the second doped region. A field drift metal oxide semiconductor (FDMOS) which is similar to the laterally diffused metal oxide semiconductor (LDMOS) is also provided.