OMOM Stack Etching Selectivity and Contamination Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for etching high aspect ratio features in semiconductor devices, particularly in 3D flash memory devices, face challenges in achieving high selectivity and preventing contamination and structure collapse during the etching process.
Innovation Solution
A method involving the formation of an OMOM stack with alternating layers of silicon oxide and metal-containing materials, followed by the creation of patterned hardmasks, including carbon or silicon oxide and metal hardmasks, which are then etched using specific gas chemistries and plasma processes to enhance selectivity and prevent redeposition contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used for high aspect ratio features, then the etching process can be completed, but selectivity is low and contamination and structure collapse occur
Solution Approach 1:
The patent segments the etching process into multiple selective etching steps, each targeting specific layers (oxide layers, metal layers, hardmask layers) with different etch chemistries and parameters. This segmentation allows high selectivity for each layer while maintaining overall structure integrity during the complete etching sequence.
Solution Approach 2:
The patent introduces intermediate hardmask layers (carbon-based and metal-based) that act as protective intermediaries during etching. These hardmasks prevent direct plasma exposure to underlying structures, reducing contamination and preventing structure collapse while enabling precise pattern transfer.
2Productivity
If aggressive etching is used to increase productivity, then etching speed increases, but faceting and contamination increase
Solution Approach 1:
The patent employs periodic alternation between aggressive etching steps (for speed) and gentle passivation steps (for geometry control). This periodic action allows high productivity while preventing excessive faceting and contamination through intermittent process modulation.
Solution Approach 2:
The patent dynamically changes etching parameters (gas composition, power, pressure, temperature) between different etching steps to optimize both speed and precision. Parameter adjustments enable transition between high-speed removal and controlled, clean etching as needed for different process stages.
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 significantly increases both vertical and radial selectivity of the etching process, reducing faceting and contamination, and allows for the precise formation of high aspect ratio features without structure collapse, thereby improving the packing density and reliability of semiconductor devices.
Implementation Method 1
etched using specific gas chemistries and plasma processes
Implementation Method 2
The OMOM stack is etched through the hardmask
Data Source
AI summary
A method for etching features in an OMOM stack with first layer of silicon oxide, a second layer of a metal containing material over the first layer, a third layer of silicon oxide over the second layer, and a fourth layer of a metal containing material over the third layer is provided. A hardmask is formed over the stack. The hardmask is patterned. The OMOM stack is etched through the hardmask.