Plasma Etching Sequence With Tungsten Sidewall Coating
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Solution Overview
Problem
Existing etching methods for silicon-containing films in manufacturing electronic devices, such as NAND flash memory, result in the formation of carbon deposits on masks, leading to mask protection issues and side wall bending during the etching of multilayers with inclined boundaries, which affects the precision and integrity of the recess shape.
Innovation Solution
An etching method involving multiple plasma processes using different gases and pressures to form tungsten-containing layers on the side walls of the recess, which helps in maintaining the intended shape by reducing charge imbalance and directing ions more linearly, thereby minimizing side wall bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single plasma etching process is used to etch silicon-containing films, then the etching speed is maintained, but the side walls of the recess bend and the mask protection is compromised due to carbon deposit formation
Solution Approach 1:
The etching process is divided into multiple sequential steps: first etching to form the recess, then supplying tungsten-containing plasma to deposit tungsten on side walls, and finally second etching to complete the recess formation. This segmentation allows each step to optimize for its specific function, preventing side wall bending while maintaining etching efficiency.
Solution Approach 2:
Tungsten plasma is supplied before the second etching step to pre-coat the side walls with tungsten. This preliminary action creates a protective layer that prevents charge accumulation and side wall bending during the subsequent etching process, ensuring the recess maintains its intended shape.
2Reliability
If carbon-containing plasma is used to protect the mask during etching, then mask protection is improved, but carbon deposits form on the mask and side walls causing bending and shape distortion
Solution Approach 1:
Tungsten plasma acts as an intermediary layer between the carbon-containing etching plasma and the side walls. The tungsten deposit on the side walls prevents direct interaction with carbon species, eliminating carbon deposit formation and side wall bending while allowing the etching process to continue effectively.
Solution Approach 2:
The process changes the material composition parameter by introducing tungsten-containing plasma between etching steps. This parameter change transforms the side wall surface from silicon-containing material to tungsten-coated material, which has different interaction properties with carbon species, preventing unwanted carbon deposition.
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 achieves a recess with a precise, less-bending side wall structure, reducing defects and ensuring accurate formation of features in the silicon-containing films, particularly in three-dimensional structures like NAND flash memory.
Implementation Method 1
etching the first region with first plasma generated from a first process gas to form a recess
Implementation Method 2
supplying second plasma generated from a second process gas containing tungsten to the substrate
Data Source
AI summary
An etching method and a plasma processing apparatus form a recess with an intended shape. The etching method includes (a) providing a substrate including a silicon-containing film and a mask on the silicon-containing film. The silicon-containing film including a first region and a second region having a boundary therebetween as viewed in cross section in a direction perpendicular to a plane direction of the substrate. The boundary includes a slope extending in a direction inclined with respect to the plane direction. The method further includes (b) etching, after (a), the first region with first plasma generated from a first process gas to form a recess, (c) supplying, after (b), second plasma generated from a second process gas containing tungsten to the substrate, and (d) etching, after (c), the recess with third plasma generated from a third process gas. The recess crosses the slope in the cross section after (d).