Tri-Layer Photoresist for Selective Etching
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Solution Overview
Problem
The complexity of semiconductor device manufacturing increases as feature sizes decrease, making it challenging to form reliable semiconductor devices at smaller sizes due to difficulties in fabrication processes.
Innovation Solution
A tri-layer photoresist layer is used, comprising a bottom layer, a silicon-containing middle layer with a carbon backbone and hydrophilic side chains, and a top layer, which improves etching selectivity and solubility, allowing for precise patterning and removal of layers without damaging the substrate or material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single-layer photoresist and etching processes are used, then the manufacturing process is simpler, but the etching selectivity is insufficient and harmful chemicals like diluted hydrofluoric acid must be used
Solution Approach 1:
The photoresist system is divided into three distinct layers: a bottom layer (e.g., silicon oxide), a middle layer (silicon-containing polymer with hydrophilic groups), and a top layer (organic photoresist). This segmentation allows each layer to perform its specific function - the bottom layer provides etch selectivity, the middle layer provides solubility control and pattern transfer, and the top layer provides lithographic patterning. This resolves the contradiction by achieving high etching selectivity through layer differentiation rather than relying on harmful chemicals.
Solution Approach 2:
The middle layer is composed of a silicon-containing polymer with a carbon backbone and hydrophilic side chains (such as poly(silyrene-co-silyl acrylate) or poly(silyl methacrylate-co-silyl acrylate)). This composite material structure combines the benefits of silicon content (for etch selectivity) with hydrophilic groups (for controlled solubility in base solutions). This composite approach achieves both high etching selectivity and controlled removal without requiring diluted hydrofluoric acid.
2Productivity
If feature sizes are reduced to increase device density, then more devices can be manufactured on a single wafer, but the fabrication process becomes more difficult and reliability decreases
Solution Approach 1:
Different regions of the photoresist system have different local properties optimized for specific functions. The bottom layer has high silicon content for etch selectivity, the middle layer has controlled silicon content with hydrophilic groups for solubility control, and the top layer has standard photoresist properties for patterning. This local quality differentiation allows precise control at smaller feature sizes, maintaining fabrication reliability while enabling higher device density.
Solution Approach 2:
The invention changes the chemical parameters of the photoresist system by introducing a middle layer with specific silicon content (providing etch selectivity) and hydrophilic groups (providing solubility control). This parameter change allows the etching process to be highly selective and the removal process to be controlled using benign base solutions, thereby maintaining fabrication reliability even as feature sizes decrease and device density increases.
3Ease of manufacture
If harmful etching solutions like diluted hydrofluoric acid are used, then etching can be performed, but the process becomes hazardous and requires special handling
Solution Approach 1:
The middle layer acts as an intermediary between the bottom layer and the etching/removal process. It is designed to be soluble in base solutions (such as ammonium hydroxide, sodium hydroxide, or potassium hydroxide) while providing the necessary pattern transfer function. This intermediary layer allows the use of benign base solutions instead of harmful hydrofluoric acid, eliminating chemical hazards while maintaining ease of manufacture.
Solution Approach 2:
The invention converts the potential harm of using strong etchants into a benefit by designing a middle layer that is specifically soluble in mild base solutions. The silicon-containing polymer with hydrophilic groups is engineered to be easily removed by benign chemicals, thereby converting what would have been a harmful process (requiring strong etchants) into a safe and easy manufacturing 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 approach enables efficient and precise patterning and etching of semiconductor structures, enhancing the reliability and accuracy of semiconductor device fabrication at smaller scales by improving etching selectivity and reducing the need for harmful etching solutions like diluted hydrofluoric acid.
Implementation Method 1
the middle layer has a carbon backbone and a side chain, and the side chain has a hydrophilic group. The middle layer is soluble in base solution by the hydrophilic group.
Data Source
AI summary
A method for forming a semiconductor device structure is provided. The method includes forming a bottom layer over a substrate and forming a middle layer over the bottom layer. The middle layer includes a carbon backbone and a first side chain bonded to the carbon backbone, and the first side chain has a hydrophilic group. The method includes forming a top layer over the middle layer and patterning the top layer to form a patterned top layer. The method includes patterning the middle layer by using the patterned top layer as a mask to form a patterned middle layer. The method includes patterning the bottom layer to form a patterned bottom layer. The method also includes removing the patterned middle layer by a base solution, and the middle layer is soluble in the base solution by the hydrophilic group.