Oxide Semiconductor Etching Using Protective Conductive Film
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Solution Overview
Problem
The etching of oxide semiconductor layers in transistor manufacturing often results in uneven thickness, leading to variations in transistor characteristics and reduced reliability, as the oxide semiconductor layer is inadvertently etched during the etching process of the conductive layer, using halogen-based gases.
Innovation Solution
A manufacturing method involving a protective conductive film is used, where the etching process is divided into two steps with different gas combinations (chlorine-based and mixed chlorine-fluorine-based gases) to selectively etch the conductive layer and then the protective film, ensuring the oxide semiconductor layer is not etched, with high etching selectivity conditions to control the etching accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a halogen-based gas is used to etch the conductive layer, then the etching process is effective, but the oxide semiconductor layer is inadvertently etched together, causing thickness variation
Solution Approach 1:
A protective conductive film is introduced as an intermediary layer between the oxide semiconductor layer and the conductive layer. This protective film has selective etching properties: it is more resistant to halogen-based etching gas than the conductive layer, yet more easily etched than the oxide semiconductor layer. During etching, the halogen-based gas selectively removes the conductive layer while the protective film prevents etching of the oxide semiconductor layer, thereby maintaining thickness uniformity.
Solution Approach 2:
The etching process parameters are changed by using different etching gases for different layers. The patent specifies using a halogen-based gas (such as CF4, CCl4, BCl3, or SiCl4) for etching the conductive layer, which provides high etching efficiency while the protective film's selective resistance prevents damage to the oxide semiconductor layer.
2Productivity
If the protective conductive film is made thinner to reduce etching time, then productivity increases, but the film may not adequately protect the oxide semiconductor layer
Solution Approach 1:
The protective conductive film thickness is optimized within a specific range (5 nm to 50 nm, preferably 10 nm to 30 nm). This thickness parameter provides sufficient protection against halogen-based etching gas while minimizing etching time. The film is thin enough to be quickly removed in the second etching step but thick enough to serve as an effective barrier during the first etching step.
3Manufacturing precision
If a two-step etching process is used with high selectivity, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The etching process is segmented into two distinct steps: (1) etching the conductive layer using halogen-based gas until the protective film is exposed, and (2) etching the protective film using the same or different etching conditions until the oxide semiconductor layer is exposed. This segmentation allows precise control over which layer is etched at each stage, achieving high manufacturing precision through systematic process division.
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 reduces the etching of the oxide semiconductor layer, maintains its thickness uniformity, and enhances the reliability and performance of the transistors by preventing excessive etching and residue formation.
Implementation Method 1
The etching process including two steps includes a first etching step in which the conductive layer is etched and a second etching step in which the protective conductive film is etched
Data Source
AI summary
An object is to provide a technique by which a semiconductor device including a high-performance and high-reliable transistor is manufactured. A protective conductive film which protects an oxide semiconductor layer when a wiring layer is formed from a conductive layer is formed between the oxide semiconductor layer and the conductive layer, and an etching process having two steps is performed. In a first etching step, an etching is performed under conditions that the protective conductive film is less etched than the conductive layer and the etching selectivity of the conductive layer to the protective conductive film is high. In a second etching step, etching is performed under conditions that the protective conductive film is more easily etched than the oxide semiconductor layer and the etching selectivity of the protective conductive film to the oxide semiconductor layer is high.