Active Matrix Substrate Contact Hole Formation via Mixed Gas Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing RIE dry etching methods using fluorine gas alone, such as CF4 or SF6, face challenges in controlling contact resistance and maintaining desirable contact hole shapes due to ion damage and isotropic etching, leading to increased contact resistance and potential disconnection of the transparent conductive film in active matrix substrates.
Innovation Solution
A production method using a mixed gas of CHF3, CF4, and O2 for dry etching, followed by oxygen ashing, to form contact holes in a one-mask process, which reduces ion damage and promotes anisotropic etching, resulting in lower contact resistance and desirable forward tapered shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If RIE dry etching using fluorine gas alone (CF4 or SF6) is performed, then contact holes are formed in silicon insulating layers, but contact resistance increases between Cr/Al film electrodes and transparent conductive film
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas from pure fluorine gas (CF4 or SF6) to a mixed gas containing CHF3, CF4, and O2. This parameter change modifies the etching chemistry to reduce ion damage to the electrode surface while maintaining effective silicon insulating layer removal, thereby lowering contact resistance between the Cr/Al film and transparent conductive film.
Solution Approach 2:
The patent uses a composite gas mixture (CHF3, CF4, and O2) instead of a single fluorine gas. This composite approach combines the benefits of different gases: CHF3 provides controlled etching, CF4 contributes to fluorine-based silicon removal, and O2 helps reduce ion damage and improve surface conditions, achieving both good contact hole formation and low contact resistance.
2Reliability
If gas pressure is increased to decrease self-bias voltage and reduce contact resistance, then contact resistance decreases, but isotropic etching occurs causing wedge-shaped over-etching at interfaces
Solution Approach 1:
The patent changes multiple parameters simultaneously: gas composition (to mixed gas), pressure (optimized range), and power (optimized range). These combined parameter changes enable the process to achieve low contact resistance without excessive isotropic etching, maintaining desirable contact hole shapes with forward tapering rather than wedge-shaped over-etching.
Solution Approach 2:
The patent optimizes the dynamic balance between isotropic and anisotropic etching components by adjusting process parameters. The mixed gas composition and optimized pressure/power conditions create a dynamic etching environment where the anisotropic component maintains vertical profile control while the isotropic component sufficiently reduces contact resistance, achieving both goals simultaneously.
3Manufacturing precision
If RIE dry etching is performed to reach electrodes at different depth positions, then contact holes are formed to multiple electrodes, but shallower electrodes suffer more ion damage and contact resistance becomes extremely high
Solution Approach 1:
The patent changes the etching gas composition to a mixed gas (CHF3, CF4, O2) with optimized ratios, along with adjusting pressure and power parameters. This parameter optimization reduces ion damage to shallow electrodes during the etching process, ensuring that contact resistance remains low for both deep and shallow contact holes formed in the same process.
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 effectively reduces contact resistance between Cr or Al films and transparent conductive films, stabilizes contact resistance, and maintains desirable etching shapes, even with varying self-bias voltage, while minimizing ion damage and over-etching issues.
Implementation Method 1
RIE dry etching using mixed gas of CHF3, CF4 and O2
Implementation Method 2
dry etching using mixed gas of CHF3, CF4 and O2 to form the plurality of contact holes
Implementation Method 3
subjecting the plurality of contact holes to oxygen ashing
Data Source
AI summary
The invention provides a production method for an active matrix substrate in which a plurality of contact holes are formed by a one-mask process so as to reach metal films which are present at different depth positions in an insulating layer and are not evaporated by dry etching using a fluorine-containing gas. The method includes a step of performing dry etching using mixed gas of CHF3, CF4 and O2 to form the plurality of contact hole, a step of subjecting the plurality of contact holes to oxygen ashing, and a step of forming a transparent conductive film in the plurality of contact holes.