Impurity Diffusion Method for Semiconductor Gate Electrodes
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Solution Overview
Problem
The miniaturization of transistors has led to increased variations in the work function and resistance value of gate electrodes due to impurity loss during surface oxidation or etching processes, necessitating a faster method for compensating for these losses without degrading throughput.
Innovation Solution
An impurity diffusion method involving a substrate processing apparatus that raises the temperature of a thin film to a vapor diffusion temperature and supplies an impurity-containing gas along with an inert gas and an impurity diffusion acceleration gas to accelerate impurity diffusion, or a reducing gas to reduce native oxide films, allowing for higher concentration impurity diffusion within a shorter time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If vapor diffusion is used to diffuse impurities into polysilicon or amorphous silicon to compensate for impurity loss, then the work function and resistance value of the gate electrode can be controlled, but the process takes a long time which degrades throughput
Solution Approach 1:
The patent changes the chemical parameters of the diffusion environment by introducing a reducing gas (H2, B2H6, or SiH4) to create a reduced atmosphere. This parameter change in the gas composition enables faster impurity diffusion kinetics while maintaining precise control over the final impurity concentration, thereby achieving both high manufacturing precision and improved throughput
Solution Approach 2:
The patent uses a composite gas mixture consisting of an impurity-containing gas (BCl3 or B2H6) combined with a reducing gas (H2, B2H6, or SiH4). This composite gas system provides both the impurity source and the reducing environment simultaneously, enabling accelerated diffusion that maintains precision while reducing process time and improving throughput
2Speed
If a reducing gas is supplied to reduce native oxide films on the thin film surface, then impurity diffusion can be accelerated, but the process complexity increases
Solution Approach 1:
The patent merges two separate functions into a single gas supply step: the reducing function (to remove native oxide) and the impurity supply function (to provide dopant atoms). By combining these functions in one composite gas mixture and one diffusion step, the process complexity does not increase significantly while achieving accelerated diffusion speed
Solution Approach 2:
The reducing gas components (H2, B2H6, SiH4) serve multiple functions: they reduce native oxide films on the surface, create a reducing atmosphere that accelerates diffusion kinetics, and in some cases (B2H6, SiH4) also serve as additional impurity sources. This multi-functionality achieves fast diffusion without adding significant process 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
This method enables the rapid diffusion of impurities at higher concentrations, effectively compensating for losses during manufacturing and maintaining throughput, while ensuring in-plane uniformity and boron intensity within acceptable ranges.
Implementation Method 1
raising a temperature of the object to a vapor diffusion temperature in the processing chamber; and supplying an impurity-containing gas that contains the impurities into the processing chamber together with an inert gas and diffusing the impurities into the thin film formed on the object of which the temperature is raised to the vapor diffusion temperature
Implementation Method 2
an impurity diffusion acceleration gas for accelerating the diffusion of the impurities into the thin film, is supplied into the processing chamber, together with the impurity-containing gas and the inert gas
Implementation Method 3
a reducing gas having a reducing function is supplied into the processing chamber, together with the inert gas so that a native oxide film existing on a surface of the thin film that is formed on the object is reduced while raising the temperature of the object
Data Source
AI summary
The impurity diffusion method includes: transferring an object on which the thin film is formed into a processing chamber (operation 1); raising a temperature of the object to a vapor diffusion temperature in the processing chamber (operation 3); and supplying an impurity-containing gas that contains the impurities into the processing chamber, together with an inert gas and diffusing the impurities in the thin film formed on the object of which the temperature is raised to the vapor diffusion temperature (operation 4), wherein in the operation 4, an impurity diffusion acceleration gas for accelerating the diffusion of the impurities into the thin film is supplied into the processing chamber, together with the impurity-containing gas and the inert gas.