Removable Blocking Layer for Uniform Etching of Inner Spacers
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Solution Overview
Problem
Conventional etching processes face challenges in simultaneously etching structures of differing dimensionality without introducing additional process steps, leading to uneven etching and undesirable damage to underlying structures due to overetching, which decreases throughput and yield.
Innovation Solution
The formation of a blocking layer using ammonia gas and fluorine-containing gases on inner spacers inhibits etchant gas diffusion, followed by removal at elevated temperatures, allowing etching of structures with varying dimensionality without additional steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If additional mask formation steps are introduced to protect each type of structure, then etching uniformity is improved, but manufacturing complexity and process time increase
Solution Approach 1:
A protective layer is formed on the substrate surface before the etching process begins. This preliminary protective layer prevents etchant access to sensitive regions during etching, eliminating the need for additional mask formation steps while maintaining etching uniformity across structures of different dimensionalities
Solution Approach 2:
The protective layer acts as an intermediary between the etchant and the substrate structures. It selectively blocks etchant diffusion to sensitive materials while allowing etching to proceed on target structures, thereby simplifying the overall process by replacing multiple masking operations with a single protective layer formation
2Manufacturing precision
If etching time is extended to complete etching of larger structures, then etching completeness is improved, but damage to smaller structures increases
Solution Approach 1:
The protective layer is applied in advance to counteract the harmful effect of overetching. It preemptively blocks etchant access to sensitive materials and structures that would be damaged by extended etching times, allowing the etching process to run long enough to complete etching of larger structures without causing damage to smaller or more sensitive features
3Object-affected harmful factors
If etching time is reduced to protect smaller structures, then overetching damage is reduced, but etching completeness of larger structures decreases
Solution Approach 1:
The protective layer serves as a mediator that decouples the etching time requirements of different structure sizes. By blocking etchant access to sensitive regions, it allows the etching process to run for the longer duration needed to complete etching of larger structures, while the protective layer prevents damage to smaller structures that would otherwise require shorter etching times
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 increases overetch margin, reducing structural damage and improving device yield and performance by preventing etchant diffusion into sensitive materials, while maintaining pristine material surfaces post-removal.
Implementation Method 1
The blocking layer inhibits diffusion of the etchant gas into the second material
Implementation Method 2
removing the blocking layer from the oxygen-containing material by exposing the vertical stack to a temperature of at least 80° C.
Data Source
AI summary
A method of etching a target material of a substrate includes selectively forming a blocking layer on an oxygen-containing material using ammonia gas and at least one fluorine-containing gas, etching the target material using an etchant gas, and removing the blocking layer from the oxygen-containing material by exposing the vertical stack to a temperature of at least 80° C. The substrate also includes a vertical stack of layers of a first material suspended between structures of a second material. The oxygen-containing material covers surfaces of the second material in openings between the layers of the first material. The blocking layer inhibits diffusion of the etchant gas into the second material.