Semiconductor Fine Pattern Formation Using Double Patterning
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Solution Overview
Problem
Current methods for forming fine patterns in semiconductor devices using polysilicon hard mask patterns face challenges due to reduced etching rates and asymmetric sidewall profiles caused by polysilicon exposure in harsh etching environments, limiting the ability to achieve desired pitch sizes.
Innovation Solution
A method involving the formation of an etch film, a protection film, and multiple mask patterns is used, where the polysilicon mask patterns are removed before etching, allowing the etch film to be etched using hard mask patterns as an etch mask, thereby preventing rate reduction and achieving desirable vertical sidewall profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polysilicon is used as an etch mask material for forming hard mask patterns, then the hard mask patterns can be formed, but the etching rate is reduced and the sidewall profile becomes inclined with large angle of inclination
Solution Approach 1:
The patent removes the polysilicon mask material before performing the tungsten etching process. This extraction eliminates the harmful interaction between fluoride atoms and silicon atoms, preventing the reduction in etching rate and the formation of inclined sidewall profiles. The polysilicon is completely removed, leaving only the hard mask pattern for the etching process.
Solution Approach 2:
The patent performs the removal of polysilicon mask material as a preliminary action before the tungsten etching process. By removing the polysilicon in advance, the system prevents the chemical reaction between fluoride etchant and silicon that would otherwise occur during etching, thereby maintaining high etching rates and vertical sidewall profiles.
2Manufacturing precision
If polysilicon mask patterns remain on hard mask pattern, then the hard mask pattern is formed, but asymmetric sidewall profile is formed due to etchant scattering
Solution Approach 1:
The patent extracts and removes the polysilicon mask material before the critical etching process. This removal eliminates the source of etchant scattering that causes asymmetric sidewall profiles. The polysilicon is completely extracted from the structure, ensuring uniform etching and symmetric sidewall formation.
Solution Approach 2:
The patent performs polysilicon removal as a preliminary action before etching the substrate to form device isolation trenches. This preliminary removal prevents etchant scattering at the edges of polysilicon films, thereby avoiding asymmetric sidewall profiles in the formed trenches.
3Length of moving object
If double patterning is used to form fine patterns with smaller pitch, then the pitch size is reduced below photolithography resolution limits, but polysilicon exposure causes reduced etching rate and poor sidewall profiles
Solution Approach 1:
The patent removes the polysilicon mask material before performing etching processes in the double patterning sequence. This extraction eliminates the harmful effects of polysilicon exposure to fluoride-based etchants, maintaining both the reduced pitch dimensions and high-quality vertical sidewall profiles in the fine patterns.
Solution Approach 2:
The patent performs polysilicon removal as a preliminary action before each etching step in the double patterning process. This preliminary removal ensures that subsequent etching processes achieve both the desired fine pitch dimensions and the required sidewall profile quality without interference from residual polysilicon.
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 the formation of fine patterns with improved sidewall profiles and increased etching rates, overcoming the limitations of polysilicon hard mask patterns in achieving smaller pitch sizes beyond photolithography resolution restrictions.
Implementation Method 1
some fluoride (F) atoms of the etchant used for etching the tungsten (W) film are lost due to a chemical reaction between fluoride (F) atoms of the etchant and silicon (Si) atoms of the polysilicon
Data Source
AI summary
A method for forming fine patterns of a semiconductor device is disclosed. The method includes forming an etch film on a substrate, forming a protection film on the etch film, forming a hard mask layer on the protection film, and forming a plurality of first mask patterns characterized by a first pitch on the hard mask layer. The method further comprises forming a plurality of second mask patterns, forming hard mask patterns exposing portions of the protection film by etching the hard mask layer using the first and second mask patterns as an etch mask, and removing the first and second mask patterns. The method still further comprises exposing portions of the etch film and forming a plurality of fine patterns characterized by a second pitch equal to half of the first pitch by etching the etch film using at least the hard mask patterns as an etch mask.