Oxide Semiconductor Device Impurity Removal
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Solution Overview
Problem
Semiconductor devices with oxide semiconductors face reliability issues due to shape defects and degradation of electric characteristics caused by impurities from etching gases, such as chlorine and boron, which can lead to oxygen vacancies and parasitic channels.
Innovation Solution
A method for manufacturing semiconductor devices involves forming a gate electrode layer, gate insulating film, and island-shaped oxide semiconductor film, followed by plasma treatment using a halogen-containing etching gas to create source and drain electrode layers, and subsequent impurity-removing treatments to reduce chlorine and boron concentrations on the oxide semiconductor film surface to ≤5×10^18 atoms/cm^3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma treatment using halogen-containing etching gas is used to form source and drain electrode layers, then the manufacturing process is simplified and productivity is improved, but impurities such as chlorine and boron remain on the oxide semiconductor film surface causing reliability degradation
Solution Approach 1:
The manufacturing process is divided into distinct stages: first performing plasma treatment with halogen-containing etching gas to form source and drain electrode layers, then performing a separate impurity-removing treatment specifically targeted at the oxide semiconductor film surface. This segmentation allows each process to optimize for its specific function while avoiding the trade-off between productivity and reliability.
Solution Approach 2:
The harmful impurities (chlorine, boron) are selectively extracted from the oxide semiconductor film surface through a dedicated impurity-removing treatment step. This extraction process specifically targets and removes the problematic elements without affecting the previously formed electrode layers or other device structures.
2Adaptability or versatility
If multiple thin films are complicatedly stacked to form the semiconductor device, then device functionality is enhanced, but shape defects and electric characteristic degradation occur due to manufacturing process impurities
Solution Approach 1:
An insulating layer is introduced as an intermediary between the oxide semiconductor film and the source/drain electrode layers. This intermediary layer serves multiple functions: it prevents direct contact that would cause impurity contamination, it maintains the complex multi-layer structure needed for device functionality, and it provides a buffer that protects the oxide semiconductor film from manufacturing-induced defects.
3Ease of manufacture
If elements from etching gas remain on the oxide semiconductor film surface, then the manufacturing process is simpler, but oxygen vacancies and parasitic channels are formed degrading electric characteristics
Solution Approach 1:
The halogen-containing etching gas, which initially appears harmful due to impurity deposition, is utilized in the plasma treatment step to effectively form the source and drain electrode layers. The subsequent impurity-removing treatment then converts the potential harm into a benefit by selectively removing the deposited impurities, allowing the etching gas to perform its useful function without compromising 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 enhances the reliability of semiconductor devices by minimizing impurity-induced defects and maintaining stable electric characteristics, improving the overall performance and yield of oxide semiconductor-based transistors.
Implementation Method 1
processing the conductive film by plasma treatment using an etching gas containing a halogen element
Implementation Method 2
performing impurity-removing treatment on the exposed oxide semiconductor film to remove the element contained in the etching gas
Data Source
AI summary
A highly reliable semiconductor device and a method for manufacturing the semiconductor device are provided. In a semiconductor device including a bottom-gate transistor in which an insulating layer functioning as a channel protective film is provided over an oxide semiconductor film, elements contained in an etching gas can be prevented from remaining as impurities on a surface of the oxide semiconductor film by performing impurity-removing process after formation of an insulating layer provided over and in contact with the oxide semiconductor film and/or formation of source and drain electrode layers. The impurity concentration in the surface of the oxide semiconductor film is lower than or equal to 5×1018 atoms/cm3, preferably lower than or equal to 1×1018 atoms/cm3.