LDMOS Gate and STI Structure for Reduced Current Crowding
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Solution Overview
Problem
Existing high-voltage integrated circuits, such as power amplifiers, require specialized device technology capable of withstanding high voltages, and laterally-diffused metal-oxide-semiconductor transistors need improved structures to enhance voltage-handling capability.
Innovation Solution
A structure for a laterally-diffused metal-oxide-semiconductor transistor is designed with a semiconductor substrate, including a drain, source, and a gate that surrounds a shallow trench isolation region, with specific dopant concentrations and dimensions to enhance voltage handling, and a method of forming this structure is employed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional transistor structures are used in high-voltage integrated circuits, then the device can operate at high voltages, but current crowding occurs and voltage-handling capability is limited
Solution Approach 1:
The patent applies local quality by creating a laterally-diffused drain structure where the drain region is extended laterally beneath the gate with specific dopant concentrations. This localized modification of the drain structure creates an extended drain that distributes current more evenly, reducing current crowding at the drain edge while maintaining high voltage handling capability. The shallow trench isolation structure is also locally optimized to control electric field distribution in specific regions.
Solution Approach 2:
The patent transitions from a conventional vertically-oriented drain structure to a laterally-diffused drain structure that extends in the lateral dimension beneath the gate. This dimensional change allows the drain to extend further laterally, creating a longer current path that reduces current density and crowding effects while maintaining the vertical electric field necessary for high voltage operation.
2Reliability
If the drain structure is extended to reduce current crowding, then voltage-handling capability improves, but device breakdown characteristics worsen
Solution Approach 1:
The patent employs parameter changes by carefully controlling the dopant concentration profile in the laterally-diffused drain region and the shallow trench isolation structure. By optimizing these parameters, the electric field distribution is modified to reduce peak fields that cause breakdown while maintaining the extended drain structure needed for voltage handling. The dopant concentration is specifically tailored to balance current distribution and breakdown resistance.
Solution Approach 2:
The shallow trench isolation structure serves as a protective element that cushions against device breakdown by controlling electric field distribution at critical interfaces. The isolation structure is designed beforehand to prevent field concentration that would lead to premature breakdown, providing a protective effect that enables the extended drain to function without compromising device strength.
3Reliability
If shallow trench isolation structure is added to control electric field, then voltage handling improves, but device complexity increases
Solution Approach 1:
The patent merges the shallow trench isolation structure with the laterally-diffused drain structure into an integrated configuration. The isolation trenches are positioned to work in conjunction with the extended drain, creating a unified structure that achieves voltage handling improvement without requiring completely separate components. This merging reduces overall device complexity compared to adding independent isolation structures.
Data Source
AI summary
Structures for a laterally-diffused metal-oxide-semiconductor device and methods of forming a structure for a laterally-diffused metal-oxide-semiconductor device. The structure comprises a drain and a source in a semiconductor substrate. The source includes a source region having a first terminating end, a second terminating end, and a length between the first terminating end and the second terminating end. The structure further comprises a shallow trench isolation region in the semiconductor substrate. The shallow trench isolation region surrounds the drain. The structure further comprises a gate that surrounds the shallow trench isolation region and the drain. The gate has a side section between the drain and the source region, the side section of the gate has a width, and the gate has a length in a direction transverse to the width. The length of the source region is substantially equal to the length of the gate.