Split-Gate LDMOS Structure for Higher Breakdown Voltage
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Solution Overview
Problem
The reliability of lateral diffused metal-oxide semiconductor (LDMOS) devices is compromised by hot carriers and high leakage current, particularly due to impact ionization at the corner of the gate structure and isolation structure, leading to breakdown under high drain to source voltage.
Innovation Solution
A novel design for the LDMOS device incorporating a split gate structure with a protruding portion to enhance the distribution of electric field, reducing impact ionization and increasing the drain to source breakdown voltage (Vbd).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional gate structure is used in LDMOS devices, then the device can be easily integrated with low voltage circuitry, but hot carriers and high leakage current degrade reliability under high voltage conditions
Solution Approach 1:
The gate structure is divided into two separate gates: a first gate structure disposed over the semiconductor substrate and a second gate structure disposed on an isolation structure. This segmentation allows independent optimization of each gate's function, with the first gate controlling channel formation and the second gate managing electric field distribution at the isolation structure corner, thereby reducing hot carrier effects and improving reliability under high voltage conditions.
Solution Approach 2:
The isolation structure serves as an intermediary element between the semiconductor substrate and the second gate structure. By positioning the second gate on the isolation structure rather than directly on the substrate, the patent creates a mediated configuration that enables better electric field control at the corner region, reducing impact ionization and leakage current while maintaining integration capability.
2Ease of manufacture
If the gate structure is simplified for easy integration, then manufacturing is easier, but the electric field distribution concentrates at the corner causing breakdown under high voltage
Solution Approach 1:
The gate is segmented into two independent gate structures that can be formed using separate processing steps. The first gate structure is formed over the semiconductor substrate using standard integration techniques, while the second gate structure is formed on the isolation structure. This segmentation maintains ease of manufacture through modular fabrication while distributing the electric field to prevent corner concentration and breakdown.
Solution Approach 2:
The second gate structure is positioned in a different spatial dimension - on top of the isolation structure rather than in the same plane as the first gate. This dimensional change allows the electric field to be controlled at the isolation structure corner without interfering with the primary gate operation, thereby increasing breakdown voltage while maintaining compatibility with standard integration processes.
3Device complexity
If a single gate structure is used, then the device structure is simpler, but impact ionization at the corner of the gate and isolation structure reduces breakdown voltage
Solution Approach 1:
The single gate structure is divided into two separate gates: the first gate structure over the semiconductor substrate and the second gate structure on the isolation structure. This segmentation adds complexity to the device architecture but directly addresses the impact ionization problem by enabling independent control of the electric field at the isolation structure corner, thereby improving breakdown voltage and reliability.
Solution Approach 2:
The isolation structure acts as an intermediary platform for the second gate, allowing it to be positioned strategically at the corner region where impact ionization occurs. This intermediary configuration enables the second gate to control and distribute the electric field effectively, reducing impact ionization and improving breakdown voltage despite the increased structural complexity.
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 split gate structure effectively broadens the electric field distribution, enhancing the breakdown voltage and improving the operational reliability of LDMOS devices under high voltage conditions.
Implementation Method 1
enhance the distribution of electric field
Implementation Method 2
impact ionization at the corner of the gate structure and isolation structure
Data Source
AI summary
A semiconductor device including a semiconductor substrate, an isolation structure, a first gate structure and a second gate structure is provided. The semiconductor substrate includes a source doped region and a drain doped region laterally spaced apart from the source doped region. The isolation structure is embedded in the semiconductor substrate, and the isolation structure is disposed between the source doped region and the drain doped region. The first gate structure is disposed over a region of the semiconductor substrate, and the region of the semiconductor substrate is between the isolation structure and the source doped region. The second gate structure is disposed on the isolation structure, wherein the second gate structure is laterally spaced apart from the first gate structure, and the second gate structure includes a main portion and at least one protruding portion extending from the main portion toward the drain doped region.