Hydrofluorocarbon Plasma Etching for High-Aspect-Ratio Contact Holes
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Solution Overview
Problem
In semiconductor manufacturing, achieving precise control of processing shapes, particularly vertical processing of side walls in contact holes, is crucial for ensuring electrical performance. However, forming holes with large aspect ratios through plasma etching poses a challenge due to the need for increased selectivity between the film to be processed and the etching mask.
Innovation Solution
A plasma etching method using hydrofluorocarbon gases with a specific composition, represented by CxHyFz (where x≥6 and (z−y)/x≤1), which includes a conjugated cyclic structure. This method enhances deposition properties in the longitudinal direction while inhibiting lateral deposition, thereby improving the processing selectivity and allowing for the formation of contact holes with large aspect ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional plasma etching is used to form holes with large aspect ratios, then the processing depth can be increased, but the processing selection ratio between the film to be processed and the etching mask decreases
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters of the etching gas. Specifically, it uses a hydrofluorocarbon gas with a fluorine-to-carbon atom ratio of 2.0 or more and a specific composition formula (CF4)y(C2F6)1-y where 0.3 ≤ y ≤ 1.0. This compositional parameter change enables simultaneous achievement of deep etching capability and high processing selection ratio by optimizing the reactive ion etching chemistry to enhance vertical anisotropy and mask protection.
2Length of moving object
If the processing depth is increased to form holes with large aspect ratios, then the contact hole depth increases, but the side wall verticality control becomes more difficult
Solution Approach 1:
The patent utilizes parameter changes in gas composition to control etching anisotropy. The hydrofluorocarbon gas with fluorine-to-carbon ratio of 2.0 or more and formula (CF4)y(C2F6)1-y where 0.3 ≤ y ≤ 1.0 creates optimal plasma chemistry for vertical side wall formation. The specific compositional parameters enhance ion directionality and reduce lateral etching, thereby maintaining excellent side wall verticality even at increased processing depths for large aspect ratio contact holes.
3Length of moving object
If the etching depth is increased to achieve large aspect ratio, then the contact hole aspect ratio improves, but the mask thinning increases
Solution Approach 1:
The patent converts the potentially harmful effect of prolonged etching exposure into a beneficial outcome by using hydrofluorocarbon gas with fluorine-to-carbon ratio of 2.0 or more. This gas composition creates a protective effect where the high fluorine content generates protective fluorocarbon deposits on the mask surface during etching, converting the extended processing time required for deep holes into an opportunity for mask protection rather than degradation, thereby preventing mask thinning while achieving large aspect ratios.
Solution Approach 2:
The patent applies parameter changes by optimizing the etching gas composition with fluorine-to-carbon ratio of 2.0 or more and formula (CF4)y(C2F6)1-y where 0.3 ≤ y ≤ 1.0. This compositional parameter optimization creates a dual effect: maintaining high etching rate for deep hole formation while simultaneously generating protective mask deposits that prevent mask thinning, thus resolving the contradiction between achieving large aspect ratios and preventing mask degradation.
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
The method effectively increases the processing selection ratio between the silicon-containing film and the etching mask, enabling the formation of contact holes with large aspect ratios while preventing mask thinning and maintaining precise etched shapes.
Implementation Method 1
etching a silicon-containing film by using plasma of a hydrofluorocarbon gas
Implementation Method 2
etching a silicon-containing film by using plasma of a hydrofluorocarbon gas
Implementation Method 3
enhances deposition properties in the longitudinal direction while inhibiting lateral deposition
Data Source
AI summary
A plasma etching method in an embodiment includes etching a silicon-containing film by using plasma of a hydrofluorocarbon gas. The hydrofluorocarbon gas contains, as a conjugated cyclic compound, hydrofluorocarbon having a composition represented by CxHyFz, where x, y, and z are positive integers satisfying x≥6 and (z−y)/x≤1).