Multilayer Stack Plasma Etching for Vertical and Lateral CD Control
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Solution Overview
Problem
Current plasma etch technologies face challenges in patterning nanoscale features in complex multilayer stacks for 3D semiconductor devices, particularly in achieving precise critical dimension (CD) control at an atomic scale.
Innovation Solution
A plasma etch process involving a first plasma generated from a carbon-containing halogen-based gas and an oxidizing gas to extend recesses through a middle layer, followed by a second plasma using a carbon-free halogen-based gas and an oxidizing gas for lateral etching, to control the critical dimensions of lines in the multilayer stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single plasma etch process is used to pattern multilayer stacks, then the etching speed is maintained, but the critical dimension control at different vertical positions deteriorates
Solution Approach 1:
The patent divides the single plasma etch process into two distinct plasma etching steps: a first plasma etching step using a carbon-containing halogen-based gas to etch through the middle layer, and a second plasma etching step using a carbon-free halogen-based gas to perform lateral etching. This segmentation allows each step to be optimized for different functions, resolving the contradiction between maintaining etching speed and achieving precise critical dimension control at different vertical positions in the multilayer stack.
Solution Approach 2:
The patent applies different plasma chemistries (carbon-containing vs. carbon-free halogen-based gases) to different spatial regions and depths of the etching process. The first plasma with carbon-containing gas provides bulk etching capability, while the second plasma with carbon-free gas provides precise lateral etching control near the surface. This local quality differentiation enables both high productivity and precision critical dimension control.
2Length of moving object
If recesses are extended deeply through the middle layer to expose the bottom layer, then the etching depth is achieved, but the lateral dimension control of lines deteriorates
Solution Approach 1:
The patent segments the etching process into a first vertical etching step that achieves the required etching depth through the middle layer, and a second lateral etching step that precisely controls the lateral dimensions. This segmentation allows the vertical and lateral etching to be independently controlled, resolving the contradiction between achieving deep etching and maintaining lateral dimension control.
Solution Approach 2:
The patent changes the plasma chemistry parameters between the two etching steps by switching from a carbon-containing halogen-based gas to a carbon-free halogen-based gas. This parameter change enables transition from bulk vertical etching to precise lateral etching, allowing both deep etching and accurate lateral dimension control to be achieved in sequence.
3Productivity
If a carbon-containing halogen-based gas is used for etching, then the etching rate is maintained, but the lateral etching precision deteriorates
Solution Approach 1:
The patent segments the plasma gas usage into two distinct phases: the first phase uses carbon-containing halogen-based gas for high-rate vertical etching, and the second phase uses carbon-free halogen-based gas for precise lateral etching. This temporal segmentation of gas usage allows each gas type to be optimized for its specific function, resolving the contradiction between etching rate and lateral etching precision.
Solution Approach 2:
The patent changes the chemical composition parameter of the plasma gas from carbon-containing to carbon-free between the two etching steps. This parameter change enables the system to switch from high-rate etching mode to high-precision lateral etching mode, resolving the contradiction between maintaining etching rate and achieving lateral etching precision.
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 effectively controls the width of lines at different vertical positions in the multilayer stack, achieving a desired difference between top and bottom critical dimensions, thereby enhancing the precision and reliability of 3D semiconductor device fabrication.
Implementation Method 1
exposing the substrate to a first plasma to extend the recesses through the second layer to expose a surface of the third layer, the first plasma being generated from a first halogen based gas and a first oxidizing gas
Implementation Method 2
laterally etching the recesses in the second layer using a second plasma, the second plasma being generated from a second halogen based gas and a second oxidizing gas
Implementation Method 3
the first plasma being generated from a first halogen based gas and a first oxidizing gas, the second plasma being generated from a second halogen based gas and a second oxidizing gas
Data Source
AI summary
A method for patterning includes having a substrate including a first layer, a second layer to-be-patterned disposed under the first layer, and a third layer disposed under the second layer, the first layer including a plurality of lines, each of the plurality of lines being separated by a recess, a bottom of the recess exposing a surface of the second layer; exposing the substrate to a first plasma to extend the recesses through the second layer to expose a surface of the third layer, the first plasma being generated from a first halogen based gas and a first oxidizing gas, the first halogen based gas including a carbon-containing halogen based gas; and laterally etching the recesses in the second layer using a second plasma, the second plasma being generated from a second halogen based gas and a second oxidizing gas, the second halogen based gas being a carbon-free halogen based gas.