SADP Mandrel Etching with UV Pretreatment for Linewidth Control
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Solution Overview
Problem
The existing Self-Aligned Double Patterning (SADP) technology faces challenges in accurately controlling linewidth due to pattern load effects during the dry etching process, resulting in deviations in photoresist trench linewidths between dense and sparse pattern areas, caused by photoresist residue and sidewall tilting.
Innovation Solution
A method involving a semiconductor structure with a stack of TEOS, a-Si, and amorphous carbon layers, where photoresist is pretreated using ultraviolet light to eliminate load effects before etching, followed by sequential etching of the hard mask, SOC, and a-Si layers to form a mandrel structure, thereby reducing linewidth deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If photolithography process is used to define trench linewidths in dense and sparse pattern areas, then line density is doubled through SADP technology, but load effect causes photoresist residue and sidewall tilting leading to linewidth deviation
Solution Approach 1:
The patent applies a pretreatment process to the photoresist pattern before etching to eliminate load effects. This preliminary action addresses photoresist residue and sidewall tilting issues in advance, ensuring uniform trench linewidths in both dense and sparse pattern areas before the etching process begins, thereby resolving the linewidth control problem while maintaining high line density through SADP
Solution Approach 2:
The patent modifies process parameters by introducing a pretreatment step that changes the physical or chemical state of the photoresist pattern. This parameter change eliminates the load effect variations between dense and sparse areas, allowing consistent linewidth control across different pattern densities while preserving the line density multiplication benefit of SADP
2Ease of manufacture
If dry etching is applied to hard mask layer and mandrel layer, then mandrel pattern is formed for metal wiring mask, but pattern load effect induces morphology differences between dense and sparse areas
Solution Approach 1:
The pretreatment process is applied before dry etching to eliminate load effects on the photoresist pattern. This preliminary action ensures that both dense and sparse pattern areas have uniform morphology and no residue before etching, preventing the morphology differences that would otherwise occur during dry etching of the mandrel layer
3Productivity
If photoresist development is performed to create trench patterns, then line density is increased through spacer deposition, but photoresist residue defects appear in dense and sparse pattern areas
Solution Approach 1:
The patent converts the harmful photoresist residue issue into a beneficial outcome by applying a targeted pretreatment process. This process specifically addresses and eliminates residue in both dense and sparse areas, transforming the potential defect into an opportunity to achieve uniform, defect-free patterns while maintaining the high line density achieved through SADP
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 or eliminates the load effect, minimizing post-etch trench linewidth deviations and improving linewidth control between dense and sparse pattern areas, enhancing the precision of the SADP process.
Implementation Method 1
pretreating the photoresist trench pattern in the dense pattern area and the sparse pattern area in the photoresist to eliminate the load effect
Implementation Method 2
A dry etch process is applied to a hard mask dielectric antireflection layer, an amorphous carbon layer and a mandrel layer
Data Source
AI summary
A method is disclosed for adjusting linewidth due to load effect in SADP mandrel etching. A semiconductor structure includes a TEOS layer, an a-Si layer, an SOC layer and a hard mask layer stacked from bottom to top. A photolithography process defines photoresist trench patterns on the photoresist, which includes a dense pattern area and a sparse pattern area, and the photoresist pattern of the photoresist dense pattern area and the photoresist pattern of the photoresist sparse pattern area present a load effect. The photoresist pattern is pretreated to eliminate the load effect. The hard mask layer is etched according to the photoresist pattern after the load effect is eliminated to form a hard mask pattern structure. This application, by pretreating the photoresist before etching, reduces or even eliminates the load effect, and reduces the deviation of post-etch trench linewidth from the designed trench linewidth.