Semiconductor Gate Recess Fluorine Diffusion for Threshold Stability
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Solution Overview
Problem
The existing methods for producing high-power semiconductor devices, such as HEMTs, require additional steps and increase costs due to the need for fluorine implantation after forming the gate recess, leading to unstable threshold voltage fluctuations and reduced uniformity and yield due to trap levels formed between the semiconductor layer and the gate insulating film.
Innovation Solution
A method involving dry etching with fluorine-containing gases to form a gate recess and subsequent heat treatment to diffuse fluorine into the semiconductor layer, creating a fluorine-containing region with varying concentrations to stabilize the threshold voltage and enhance normally-off operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorine implantation is performed after forming the gate recess to achieve normally-off operation, then the threshold voltage can be controlled, but the number of processing steps increases and manufacturing cost rises
Solution Approach 1:
The patent combines the fluorine introduction process with the gate recess formation process by using fluorine-containing etching gas during the recess etching step. This merging of operations eliminates the need for a separate fluorine implantation step, thereby reducing the total number of processing steps while still achieving the desired fluorine concentration in the semiconductor layer for normally-off operation.
Solution Approach 2:
The etching gas serves multiple functions: it removes semiconductor material to form the gate recess while simultaneously introducing fluorine atoms into the semiconductor layer. This multi-functionality allows a single process step to achieve both structural formation and doping, reducing manufacturing complexity.
2Reliability
If fluorine implantation is performed after forming the gate recess to stabilize threshold voltage, then normally-off characteristics improve, but manufacturing cost increases due to additional processing steps
Solution Approach 1:
The patent merges the fluorine introduction function into the gate recess formation process by using fluorine-containing etching gas. This eliminates the need for separate fluorine implantation equipment and processing steps, thereby reducing manufacturing cost while maintaining threshold voltage stability through controlled fluorine incorporation during etching.
3Manufacturing precision
If a gate recess structure is formed to achieve normally-off characteristics, then threshold voltage control improves, but trap levels form at the interface between semiconductor layer and gate insulating film, causing threshold voltage fluctuation
Solution Approach 1:
The patent introduces fluorine atoms into the semiconductor layer during the gate recess formation process, before the gate insulating film is deposited. This preliminary fluorine incorporation passivates potential trap sites at the semiconductor interface, preventing threshold voltage fluctuations that would otherwise occur due to trap level formation when the insulating film is later added.
Solution Approach 2:
By incorporating fluorine during recess formation, the patent creates a protective fluorine-containing region that cushions against the formation of harmful trap levels at the future semiconductor-insulating film interface, thereby stabilizing threshold voltage before the insulating film is even deposited.
4Reliability
If fluorine is introduced into the semiconductor layer to enhance normally-off operation, then device reliability improves, but the number of processing steps increases
Solution Approach 1:
The patent combines fluorine introduction with gate recess formation by using fluorine-containing etching gas, merging two previously separate functions into one process step. This improves productivity by reducing the total number of processing steps while maintaining the reliability benefits of fluorine incorporation for normally-off operation.
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 reduces the number of processing steps, enhances the reliability of normally-off operation, and minimizes electron trapping, resulting in improved uniformity and yield of semiconductor devices by stabilizing the threshold voltage.
Implementation Method 1
forming an opening portion as a recess in the semiconductor layer by dry etching with a gas containing fluorine components
Implementation Method 2
forming a fluorine-containing region by heating the semiconductor layer and thus diffusing, into the semiconductor layer, the fluorine components attached to side surfaces and a bottom surface of the recess
Data Source
AI summary
A method of producing a semiconductor device, includes: forming a semiconductor layer on a substrate; forming an a recess in the semiconductor layer by dry etching with a gas containing fluorine components, the recess having an opening portion on the surface of the semiconductor layer; forming a fluorine-containing region by heating the semiconductor layer and thus diffusing, into the semiconductor layer, the fluorine components attached to side surfaces and a bottom surface of the recess; forming an insulating film on an inner surface of the recess and on the semiconductor layer; and forming an electrode on the insulating film in a region in which the recess is formed.