Film Stack Patterning via Directional Etching for Dimension Control
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Solution Overview
Problem
The microloading effect in photolithography leads to variations in etch dimensions between high and low feature density regions, resulting in deformation and poor pattern transfer during the patterning of material layers in integrated circuits, as the etching rates differ due to insufficient selectivity among material layers.
Innovation Solution
A directional etching process is employed, using a gas mixture comprising an inert gas to laterally reduce the dimensions of features in a film stack, with specific etching processes altering the etching rate to maintain precise dimension control and improve selectivity, allowing for the transfer of features with desired profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional optical lithography is used for patterning, then the manufacturing process is simple and cost-effective, but the manufacturing precision deteriorates at 45 nanometer node and below due to microloading effect
Solution Approach 1:
The patent divides the single patterning process into multiple sequential etching steps (first etching process and second etching process), where each step removes a portion of the lower layer to achieve the desired final pitch. This segmentation allows precise control of etch dimensions by managing feature density variations across different etching stages, resolving the microloading effect that plagues conventional single-step lithography at 45nm node and below.
Solution Approach 2:
The first etching process is performed as a preliminary step to remove between 40-95% of the lower layer exposed by the photoresist, creating intermediate features with a first pitch. This preliminary action prepares the structure for the second etching process, allowing the system to achieve final high-precision dimensions (second pitch shorter than first pitch) while managing the microloading effect that would otherwise prevent accurate patterning at advanced nodes.
2Manufacturing precision
If multiple patterning technique is used to enhance feature density, then the manufacturing precision improves, but the device complexity increases due to multiple etching processes
Solution Approach 1:
The patent applies different etching conditions and parameters to different regions of the substrate during the multi-step etching process. The first etching process targets regions with varying feature densities differently, removing 40-95% of the lower layer to compensate for microloading effects. The second etching process then refines the features to achieve the final second pitch. This local quality approach allows precise dimension control in both high and low feature density regions without requiring excessively complex process equipment.
Solution Approach 2:
The patent changes etching parameters between the first and second etching processes to achieve different outcomes. The first process uses parameters optimized for removing the majority of the lower layer with controlled selectivity, while the second process uses different parameters to achieve the final precise pitch. This parameter changes strategy enables high manufacturing precision through multiple steps while avoiding the need for overly complex equipment or materials.
3Manufacturing precision
If etching selectivity among material layers is insufficient, then the ease of manufacture is maintained with simpler processes, but the manufacturing precision deteriorates due to deformation in high and low feature density regions
Solution Approach 1:
The first etching process is designed as a preliminary step that removes between 40-95% of the lower layer, creating a controlled intermediate state that prevents deformation before the second etching process. This preliminary action establishes a foundation that maintains structural integrity across high and low feature density regions, ensuring critical dimension control without requiring excessively selective or complex etching chemistries in subsequent steps.
Solution Approach 2:
The patent changes etching parameters between steps to optimize both precision and manufacturability. The first etching process uses parameters that provide sufficient selectivity to prevent deformation while removing the majority of the lower layer, and the second process uses different parameters to achieve the final precise dimensions. This parameter changes approach balances manufacturing simplicity with the precision needed to avoid microloading-induced deformation.
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 and dimension control, enabling precise feature transfer and reducing deformation in high and low feature density regions, thereby improving the accuracy and reliability of patterned features in integrated circuits.
Implementation Method 1
A directional etching process is employed, using a gas mixture comprising an inert gas to laterally reduce the dimensions of features in a film stack
Data Source
AI summary
Methods for patterning a film stack are provided. In one embodiment, a method for patterning a film stack disposed on a substrate includes performing a first etching process to etch a film stack disposed on a substrate, wherein the film stack includes a patterned photoresist layer disposed on an upper layer on a lower layer disposed on the substrate, wherein the patterned photoresist layer comprises openings defined between features and the features have a first pitch, wherein the first etching process removes between about 40 percent and about 95 percent of the lower layer exposed by the patterned photoresist layer from the film stack, performing a second etching process on the film stack, and upon completion of the second etching process, transferring the features into the upper or lower layer in the film stack having a second pitch, wherein the second pitch is shorter than the first pitch.