Low-Temperature Oxide Removal for InGaAs Semiconductors
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Solution Overview
Problem
The existing methods for removing natural oxide films from semiconductor layers containing indium and other elements, such as InGaAs, require high temperatures, which can damage the semiconductor device and result in incomplete oxide removal, especially when using hydrogen chloride or hydrogen fluoride gases, and do not effectively address the interface state density issues.
Innovation Solution
A method using β-diketone gases, such as hexafluoroacetylacetone, to selectively remove indium oxide at lower temperatures, followed by hydrogen chloride and hydrogen fluoride gases to remove gallium and arsenic oxides, within a controlled etching device to maintain the semiconductor layer at a low temperature and prevent reoxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrogen chloride gas or hydrogen fluoride gas is used to remove the natural oxide film, then the oxide removal capability is improved, but the required temperature becomes relatively high which may damage the semiconductor device wirings
Solution Approach 1:
The patent changes the chemical parameters of the etching gas by introducing Hfac gas (hexafluoroacetylacetone) as a new etching agent that can remove indium oxide at lower temperatures (50-300°C) compared to traditional hydrogen chloride or hydrogen fluoride gases which require 500-900°C. This parameter change in the etching chemistry enables effective oxide removal without subjecting the semiconductor device to damaging high temperatures that could harm the wirings.
Solution Approach 2:
The patent introduces Hfac gas as an intermediary substance that mediates the etching process. Hfac gas acts as a intermediate etching agent that selectively removes indium oxide through a different chemical mechanism, forming volatile complexes at lower temperatures. This intermediary approach bypasses the need for high-temperature direct etching with traditional gases, thus protecting the semiconductor device while achieving complete oxide removal.
2Temperature
If wet etching process is used to remove the natural oxide film, then the process temperature can be kept low, but the oxide removal may not be sufficient and reoxidation may occur
Solution Approach 1:
The patent replaces the wet etching process (liquid-based) with a gas-phase etching process using Hfac gas. This substitution transitions from a liquid chemical environment to a gaseous one, enabling the process to be performed in a vacuum or controlled atmosphere that prevents reoxidation. The gas-phase etching maintains low temperature operation while achieving superior oxide removal completeness through the formation of volatile indium-Hfac complexes.
Solution Approach 2:
The patent performs the Hfac gas etching process in a vacuum or inert atmosphere environment, which prevents reoxidation of the InGaAs layer surface after oxide removal. This inert environment protection ensures that the completely removed oxide surface remains oxide-free until the next processing step, combining the benefits of low temperature processing with complete and stable oxide removal.
3Manufacturing precision
If high temperature is applied to generate InF3 or GaF3 compounds for oxide removal, then the etching capability is improved, but the heat resistance limit of the device may be exceeded
Solution Approach 1:
The patent fundamentally changes the temperature parameter of the etching process by using Hfac gas chemistry that enables effective indium oxide removal at 50-300°C, compared to the 900°C+ required for InF3 formation with hydrogen fluoride gas. This parameter change in reaction temperature protects the semiconductor device wirings and other heat-sensitive components from thermal damage while maintaining effective oxide removal capability.
Solution Approach 2:
The patent uses Hfac gas as a consumable etching agent that reacts with indium oxide to form volatile complexes that are easily removed. This approach uses a temporary, easily decomposed chemical intermediate (the Hfac-indium complex) that sublimes at low temperature, eliminating the need for sustained high-temperature processing that would compromise device reliability.
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 allows for effective removal of natural oxide films at lower temperatures, reducing the risk of device damage and ensuring complete oxide removal while maintaining the semiconductor layer's integrity, thereby enhancing the performance of semiconductor devices by reducing interface state density.
Implementation Method 1
supplying a first etching gas which is β-diketone to the semiconductor layer and heating the semiconductor layer to remove an oxide of the indium constituting the natural oxide film
Implementation Method 2
supplying a second etching gas to the semiconductor layer and heating the semiconductor layer to remove an oxide of the element other than indium constituting the natural oxide film
Implementation Method 3
it is considered that the natural oxide film of the InGaAs layer is removed using, for example, a hydrogen chloride gas or a hydrogen fluoride gas as an etching gas
Implementation Method 4
In order to generate such compounds, it is necessary to heat the wafer at a relatively high temperature. For example, the generation of InF3 requires heating the wafer at a temperature of 900 degrees C. or higher
Data Source
AI summary
A technique capable of removing a natural oxide film formed on a surface of a semiconductor layer which contains a compound of indium and an element other than indium as a main ingredient, without making a temperature of the semiconductor layer relatively high. The technique includes supplying a first etching gas which is β-diketone to the semiconductor layer and heating the semiconductor layer to remove an oxide of the indium constituting the natural oxide film; and supplying a second etching gas to the semiconductor layer and heating the semiconductor layer to remove an oxide of the element constituting the natural oxide film. By using the first etching gas, it is possible to remove the indium oxide even if the temperature of the semiconductor layer is relatively low. This eliminates the need to increase the temperature to a relatively high level when removing the natural oxide film.