High-Voltage NFET Doping Structure for ON Current and Breakdown Voltage
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Solution Overview
Problem
High-voltage NFET devices face a challenge in improving performance without degrading breakdown voltage, as increasing doping concentration in the N field well affects the breakdown voltage of high-voltage MOS devices operated above 38V.
Innovation Solution
A method for forming a high-voltage metal-oxide-semiconductor transistor device involves forming a semiconductor substrate with a trench isolation region, performing ion implantation to create a well region and an extended doped region with specific doping concentrations, and forming a gate that overlaps with these regions, using phosphorous as dopants and a tilt-angle ion implantation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the doping concentration of the high-voltage N field well is increased to improve the ON current performance, then the ON current ION is improved, but the breakdown voltage VBD of the high-voltage NFET devices is degraded
Solution Approach 1:
The patent applies local quality by creating an extended doped region with a specific doping concentration that is lower than the well region but higher than the drift region. This localized doping structure allows the well region to maintain high doping concentration for high ON current while the extended doped region provides a gradual transition to preserve breakdown voltage. The resist pattern with controlled dimensions (2.25 micrometers thickness, 1.5 micrometers opening width) enables precise spatial control of this doping profile.
Solution Approach 2:
The patent utilizes parameter changes by implementing a multi-stage ion implantation process with varying doping concentrations. The first ion implantation creates the well region with high doping concentration, while the second ion implantation creates the extended doped region with intermediate doping concentration. This parameter variation in doping concentration across different regions resolves the contradiction between high ON current (requiring high doping) and high breakdown voltage (requiring low doping).
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 ON current of high-voltage NFET devices while maintaining or improving the breakdown voltage, allowing for improved performance without degrading the device's high-voltage operation.
Implementation Method 1
A first ion implantation process is performed to implant first dopants into the semiconductor substrate through the opening, thereby forming a well region having a second conductivity type in the semiconductor substrate. A second ion implantation process is performed to implant second dopants into the semiconductor substrate through the opening, thereby forming an extended doped region having the second conductivity type and being contiguous with the well region.
Data Source
AI summary
A semiconductor substrate is provided. A trench isolation region is formed in the semiconductor substrate. A resist pattern having an opening exposing the trench isolation region and partially exposing the semiconductor substrate is disposed adjacent to the trench isolation region. A first ion implantation process is performed to implant first dopants into the semiconductor substrate through the opening, thereby forming a well region in the semiconductor substrate. The trench isolation region is within the well region. A second ion implantation process is performed to implant second dopants into the semiconductor substrate through the opening, thereby forming an extended doped region contiguous with the well region. The resist pattern is then removed. After removing the resist pattern, a gate dielectric layer is formed on the semiconductor substrate. A gate is then formed on the gate dielectric layer. The gate overlaps with the extended doped region.