Selective Tungsten Removal Using Oxide-Protected Wet Etching
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Solution Overview
Problem
The semiconductor industry faces challenges in manufacturing processes, particularly in the partial removal of tungsten-including layers during the fabrication of semiconductor devices, where existing methods lack selectivity and can lead to electrical leakage or short circuits.
Innovation Solution
A method involving the directional treatment of tungsten-including layers with O2 plasma to convert surface tungsten into tungsten oxide, followed by a wet etching process using ozonated water, which selectively removes untreated tungsten while retaining tungsten oxide, ensuring precise removal of tungsten from trench sidewalls while maintaining it on trench bottoms and surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching methods are used to remove tungsten, then tungsten removal is achieved, but selectivity is poor leading to electrical leakage and short circuits
Solution Approach 1:
The patent applies preliminary action by performing plasma treatment on the tungsten-including layer before etching to convert surface tungsten into tungsten oxide. This preliminary oxidation step creates a differentiated surface state that enables selective removal: the oxidized surface regions resist etching while non-oxidized regions are selectively removed by the etchant, thereby achieving the required etching selectivity and preventing electrical leakage
Solution Approach 2:
The patent applies parameter changes by altering the chemical state of tungsten through plasma treatment, transforming it from metallic tungsten to tungsten oxide on the surface. This parameter change (oxidation state) creates a differential etch resistance that enables selective etching, improving both manufacturing precision and electrical reliability
2Manufacturing precision
If tungsten is completely removed from all surfaces, then trench sidewalls are cleared, but tungsten oxide layers needed for electrical contact are lost
Solution Approach 1:
The patent applies local quality by creating different surface states in different locations: plasma treatment selectively oxidizes tungsten on horizontal surfaces (trench bottoms and top surfaces) while leaving vertical sidewalls relatively untouched due to plasma directionality. Subsequent etching then removes non-oxidized tungsten from sidewalls while preserving the oxidized tungsten oxide layers on horizontal surfaces, achieving both sidewall clearance and oxide retention
Solution Approach 2:
The patent applies dimensionality change by utilizing the directional nature of plasma treatment to create vertical differentiation in the tungsten layer. The plasma process preferentially treats horizontal surfaces versus vertical surfaces, creating a three-dimensional pattern of oxidized and non-oxidized regions that enables selective removal based on spatial orientation
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 selectivity of tungsten removal, reducing the risk of electrical leakage and short circuits, and allows for the retention of tungsten oxide layers, thereby improving the reliability and performance of semiconductor devices.
Implementation Method 1
performing a treatment on a surface region of the first portion of the tungsten-including layer so as to convert tungsten in the surface region into tungsten oxide
Implementation Method 2
partially removing the tungsten-including layer using an etchant which has a higher etching selectivity to tungsten than tungsten oxide
Data Source
AI summary
A method for selectively removing a tungsten-including layer includes: forming a tungsten-including layer which has a first portion and a second portion; performing a treatment on a surface region of the first portion of the tungsten-including layer so as to convert tungsten in the surface region into tungsten oxide; and partially removing the tungsten-including layer using an etchant which has a higher etching selectivity to tungsten than tungsten oxide such that the second portion of the tungsten-including layer is fully removed, and the first portion of the tungsten-including layer, having the tungsten oxide in the surface region, is at least partially retained.