Selective Cyclic Dry Etching of Dielectric Materials
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Solution Overview
Problem
Conventional etch processes, particularly reactive ion etching (RIE), face challenges in achieving precise control over etch selectivity and uniformity, especially for thin dielectrics (<100 nm) and carbon-containing materials like SiC, SiCN, and SiCOH, where high etch selectivity and uniformity are difficult to maintain.
Innovation Solution
A selective cyclic etch process is developed using chemical atomic layer etching, where a modification layer is formed using a first plasma on a substrate with carbon/nitride surfaces and etched using fluorine or chlorine containing plasmas, allowing for precise control over etch selectivity between carbon/nitride containing and non-containing surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional reactive ion etching (RIE) is used for thin dielectrics, then high etch rate is achieved, but precise control of etch selectivity and uniformity deteriorates
Solution Approach 1:
The continuous RIE process is segmented into discrete cyclic steps: plasma modification step to form a modification layer, followed by etching step to remove the modification layer. This segmentation allows independent optimization of each step, achieving both high etch rate and precise selectivity control for thin dielectric layers.
Solution Approach 2:
The etching process uses periodic cyclic action with alternating plasma modification and etching steps. Each cycle modifies the surface uniformly, then etches the modification layer with high selectivity. This periodic approach maintains uniformity across thin dielectrics while achieving high overall etch rates through multiple cycles.
2Ease of manufacture
If conventional RIE is used for carbon-containing materials, then etching capability is provided, but precise control of etch selectivity deteriorates
Solution Approach 1:
A plasma modification layer is introduced as an intermediary between the carbon-containing material and the etching plasma. The modification layer has enhanced etchability and serves as a selective sacrificial layer, allowing precise control of etch selectivity for carbon-containing materials while maintaining etching capability.
Solution Approach 2:
The process changes the chemical and physical parameters of the material surface through plasma modification before etching. This parameter change creates a modification layer with distinct properties from the underlying carbon-containing material, enabling precise etch selectivity control through the differential etching of the modification layer versus the original material.
3Manufacturing precision
If plasma modification layer is formed and etched cyclically, then high etch selectivity and uniformity are achieved, but process complexity increases
Solution Approach 1:
The plasma modification step serves multiple functions: it prepares the surface for selective etching, creates the modification layer with controlled thickness, and enables uniform etching across different materials. This multi-functionality reduces the need for separate process steps, thereby managing complexity while achieving high precision.
Solution Approach 2:
The cyclic process incorporates feedback control where the modification layer formation and etching steps are iteratively adjusted based on desired outcomes. Process parameters such as plasma power, gas flow, and cycle duration are optimized through feedback to achieve consistent high selectivity and uniformity, managing complexity through controlled iteration rather than uncontrolled process variation.
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 process achieves high selectivity and uniformity in etching, enabling precise control over etch rates and profiles, even for thin dielectric layers, by forming and modifying layers on specific surfaces, thus addressing the limitations of RIE methods.
Implementation Method 1
treating both the first and the second surface with at least one of: a) a plasma assisted process with ions and/or radicals to form a plasma modified layer
Implementation Method 2
c) plasma etching of the modification layer by fluorine or chlorine containing plasma (or by a halogen source generally)
Data Source
AI summary
In some embodiments, a selective cyclic (optionally dry) etching of a first surface of a substrate relative to a second surface of the substrate in a reaction chamber by chemical atomic layer etching comprises forming a modification layer using a first plasma and etching the modification layer. The first surface comprises carbon and/or nitride and the second surface does not comprise carbon and/or nitride.