Memory Hole Etching with Selective Oxidation and Silylation
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Solution Overview
Problem
Existing etching methods for semiconductor memory devices face challenges in forming memory holes with a wide bottom diameter and high aspect ratio while maintaining processing accuracy, particularly in three-dimensional memory devices.
Innovation Solution
The method involves forming a precursor film on the inner wall of a recess using a silicon-containing precursor, followed by oxidation and silylation processes to control the etching depth, allowing for precise formation of a memory hole with a wide bottom diameter and high aspect ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to form memory holes, then the etching process can be completed, but the processing accuracy deteriorates and uniform cross-sectional dimensions cannot be achieved
Solution Approach 1:
A precursor film is formed on the inner wall surface of the recess before the etching process. This preliminary action creates a foundation for selective oxidation that will later control the etching rate, enabling uniform cross-sectional dimensions and high processing accuracy in the final memory hole structure.
Solution Approach 2:
The oxidation process selectively modifies the upper region of the precursor film while leaving the lower region relatively unoxidized. This local quality difference creates a gradient in etching resistance along the depth direction, allowing the upper portion to resist etching and maintain uniform cross-sectional dimensions while the lower portion allows controlled etching to achieve the desired aspect ratio.
2Length of moving object
If the recess depth is increased to achieve high aspect ratio, then the aspect ratio improves, but unnecessary etching at the top surface increases
Solution Approach 1:
The precursor film is selectively oxidized in its upper region while the lower region remains relatively unoxidized. This creates a spatial gradient in chemical composition and etching resistance, where the oxidized upper portion resists etching attacks that would otherwise cause unnecessary etching at the top surface, while allowing the recess to be etched to the required depth for high aspect ratio.
Solution Approach 2:
The oxidation process is applied in advance to the upper region of the precursor film to create a protective characteristic before the etching process begins. This preliminary anti-action prevents the harmful effect of unnecessary etching at the top surface during subsequent etching steps, allowing the recess to be deepened without compromising top surface integrity.
3Manufacturing precision
If the precursor film is fully oxidized to suppress top surface etching, then processing accuracy improves, but the etching depth is reduced
Solution Approach 1:
Instead of fully oxidizing the precursor film, the oxidation process is selectively applied to only the upper region. This creates a gradient structure where the oxidized upper portion provides protection against unnecessary etching (improving processing accuracy), while the unoxidized lower portion maintains its reactivity and allows the etching process to proceed to the required depth (maintaining etching depth and high aspect ratio).
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 enables the formation of memory holes with improved processing accuracy and uniform cross-sectional dimensions, enhancing the depth and aspect ratio of the recess while suppressing unnecessary etching at the top surface, thus ensuring high precision in semiconductor memory device manufacturing.
Implementation Method 1
forming a precursor film on the inner wall surface of a recess by supplying a precursor including silicon
Implementation Method 2
oxidizing an upper region of the first film on the inner wall surface by an oxidation process, thereby forming an oxidized portion in the upper region
Implementation Method 3
silylating the oxidized portion by supplying a silylating agent to the recess
Data Source
AI summary
According to one embodiment, an etching method includes forming a first film on the inner wall surface of the recess by supplying a precursor including silicon to the recess. The etching method includes oxidizing an upper region of the first film on the inner wall surface by an oxidation process, thereby forming an oxidized portion in the upper region. The etching method includes silylating the oxidized portion by supplying a silylating agent to the recess and etching the recess after supplying the silylating agent to increase the depth of the recess.