Low-k Dielectric Barrier Etching via Carbon-Free Gas Mixture
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Solution Overview
Problem
Current methods for etching low-k dielectric barrier layers in semiconductor manufacturing, particularly those using carbon fluoride processes, often result in defects such as faceting, micro-trenching, and sidewall roughness, which degrade device performance and increase costs due to the need for aggressive cleaning and short queue times.
Innovation Solution
A non-carbon based etching process is introduced, involving a treatment gas mixture to modify the low-k barrier layer, followed by a chemical etching gas mixture containing ammonium and nitrogen trifluoride, which reduces corner faceting and prevents polymer residue formation, allowing for less aggressive processing and improved selectivity between the low-k dielectric barrier layer and underlying metal films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If carbon fluoride process gases are used to etch low-k barrier layers, then etching capability is achieved, but etching defects such as faceting, micro-trenching, and sidewall roughness occur
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas from carbon fluoride-based to a carbon-free mixture (NF3, NH3, H2, He). This parameter change fundamentally alters the etching chemistry to eliminate carbon-containing polymer deposits that cause sidewall roughness, faceting, and micro-trenching, while maintaining effective etching capability through the fluorine and hydrogen chemistry.
2Reliability
If aggressive cleaning processes are used to remove etching defects, then defect removal is achieved, but processing time increases and throughput decreases
Solution Approach 1:
The patent converts the harmful effect of carbon fluoride chemistry (which creates polymer residues requiring aggressive cleaning) into a beneficial carbon-free chemistry that inherently prevents polymer formation. By eliminating carbon from the etching gas mixture, the process self-cleans without requiring additional aggressive cleaning steps, thus maintaining reliability while improving throughput.
3Speed
If high RF bias powers are used to achieve high etch rates, then etching speed increases, but sidewall passivation and mask selectivity deteriorate
Solution Approach 1:
The patent changes the chemical composition of the etching gas to eliminate carbon-containing species that form sidewall-passivating polymers. The carbon-free chemistry (NF3, NH3, H2, He) achieves etching through different mechanisms that do not rely on carbon polymer formation, allowing high etch rates to be maintained without the trade-off of sidewall roughness and faceting that plagues traditional carbon fluoride processes.
4Manufacturing precision
If complex etchant gas mixtures are used to achieve high selectivity, then selectivity between layers is improved, but process complexity and hardware settings requirements increase
Solution Approach 1:
The patent uses a composite gas mixture of NF3, NH3, H2, and He that works synergistically to achieve high etch selectivity and performance. The NF3 provides fluorine for chemical etching, NH3 provides nitrogen for sidewall protection and etch product removal, H2 helps control polymer formation and improve etch uniformity, and He acts as a buffer gas to control plasma chemistry and ion energy distribution. This composite approach achieves high selectivity without requiring extremely complex hardware settings.
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 enhances etching selectivity, reduces damage to low-k dielectric barrier layers, and improves throughput by maintaining a soft landing on underlying metal films, preventing undercut and corrosion, while maintaining high profile control and selectivity.
Implementation Method 1
exposing a surface of the low-k barrier layer to a treatment gas mixture to modify at least a portion of the low-k barrier layer
Implementation Method 2
chemically etching the modified portion of the low-k barrier layer by exposing the modified portion to a chemical etching gas mixture
Data Source
AI summary
Implementations described herein generally relate to semiconductor manufacturing and more particularly to methods for etching a low-k dielectric barrier layer disposed on a substrate using a non-carbon based approach. In one implementation, a method for etching a barrier low-k layer is provided. The method comprises (a) exposing a surface of the low-k barrier layer to a treatment gas mixture to modify at least a portion of the low-k barrier layer and (b) chemically etching the modified portion of the low-k barrier layer by exposing the modified portion to a chemical etching gas mixture, wherein the chemical etching gas mixture includes at least an ammonium gas and a nitrogen trifluoride gas or at least a hydrogen gas and a nitrogen trifluoride gas.