LDMOS Drift Well Doping Modification for Breakdown Voltage
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Solution Overview
Problem
The miniaturization of LDMOS transistor fabrication poses challenges due to decreased geometry size, particularly in forming a semiconductor structure with sufficient breakdown voltage and maintaining the complexity of integrated circuit processing and manufacturing.
Innovation Solution
A method involving the formation of a drift well with a doping modification region in the LDMOS transistor, where the top portion of the drift well is doped with P-type dopants at a lower concentration than N-type dopants, and an oblique angle implantation process is used to reduce the net doping concentration, allowing for increased breakdown voltage and improved semiconductor structure performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the geometry size is decreased to increase functional density, then the integration level is improved, but the fabrication difficulty of LDMOS transistor increases
Solution Approach 1:
The patent applies local quality by creating a doping modification region with different doping characteristics within the drift well. Specifically, the top portion of the drift well receives additional P-type doping at an oblique angle, creating a localized region with modified net doping concentration. This local modification allows the structure to achieve sufficient breakdown voltage in miniaturized geometries without compromising overall device performance or requiring complex manufacturing changes across the entire device.
2Reliability
If the breakdown voltage is increased through doping modification, then the reliability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent employs dimensionality change by introducing oblique angle implantation at approximately 45 degrees relative to the wafer surface. This angular approach creates a doping modification region that extends laterally beneath the isolation structure, effectively utilizing the lateral dimension to achieve vertical electric field control. The oblique implantation geometry allows breakdown voltage enhancement without requiring additional processing steps or complex three-dimensional structures, thereby improving reliability while maintaining manufacturing simplicity.
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 approach enhances the breakdown voltage and overall performance of the semiconductor structure by achieving charge balance and reducing the electric field near the isolation structure, while maintaining manufacturing efficiency.
Implementation Method 1
The drift well is doped with P-type dopants at a lower concentration than N-type dopants, and an oblique angle implantation process is used to reduce the net doping concentration
Data Source
AI summary
A method of forming a semiconductor structure including: forming a drift well in a substrate, in which the drift well includes first dopants having a first conductivity type; forming an isolation structure over the drift well; forming a well region in the drift well and spaced apart from the isolation structure, such that a top portion of the drift well is between the well region and the isolation structure; doping the top portion with second dopants having a second conductivity type different from the first conductivity type, such that a doping concentration of the second dopants in the top portion is lower than a doping concentration of the first dopants in the top portion after doping the top portion; and forming a gate structure extending from the isolation structure to the well region and covering the top portion of the drift well.