Protective Layer Hard Mask Etching for High-Aspect-Ratio Profiles
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Solution Overview
Problem
Conventional techniques for etching features with high aspect ratios in semiconductor devices often result in pattern defects such as corner erosion and bowing, which can lead to unintended modifications of the critical dimension and vertical profile of the features.
Innovation Solution
A cyclic etch process is employed, which alternates between depositing a silicon-containing protective layer over the etch mask and the hard mask layer, and etching the hard mask layer using a plasma with oxygen to form incremental portions of the recess, thereby reducing or eliminating pattern defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional etching process is used to form high aspect ratio features, then the etching speed and productivity are improved, but pattern defects such as corner erosion and bowing occur, degrading manufacturing precision
Solution Approach 1:
The etching process is divided into multiple cycles, each consisting of a protective layer deposition step followed by an etching step. This segmentation allows the process to build up protection incrementally while etching, preventing corner erosion and bowing that would occur in a single continuous etching step.
Solution Approach 2:
A protective layer is deposited on the mask and feature surfaces before the etching step in each cycle. This preliminary protective action prevents the harmful effects of direct plasma exposure during etching, maintaining critical dimension accuracy while still allowing the etch to proceed at reasonable speeds.
2Manufacturing precision
If the etching process is extended to reduce pattern defects, then manufacturing precision is improved, but the process time increases, reducing productivity
Solution Approach 1:
The etching process uses periodic cycles of protective layer deposition followed by etching steps. This periodic action maintains precision by repeatedly applying protection during the etching sequence, achieving better vertical profile control than a single long etch while being more efficient than continuous protection deposition.
Solution Approach 2:
The cyclic process maintains continuous progress toward the etching goal by alternating between protection and etching steps. Each cycle advances the etch depth while maintaining feature integrity, ensuring that the useful etching action continues without unnecessary interruptions or excessive protection deposition time.
3Manufacturing precision
If a protective layer is deposited over the mask layer, then pattern defects are reduced, but the device complexity increases due to additional process steps
Solution Approach 1:
The process changes the physical and chemical parameters by using different plasma chemistries for deposition and etching. The protective layer is deposited using a silicon-containing plasma, then etched using an oxygen-containing plasma, leveraging parameter changes to achieve protection and removal at different stages of the same cyclic process.
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 cyclic etch process effectively reduces pattern defects, preserves the intended critical dimension and vertical profile of the features, and improves the aspect ratio of the etched features, particularly in high aspect ratio contact holes.
Implementation Method 1
depositing, using a first plasma, a silicon-containing protective layer over the etch mask layer and the hard mask layer
Implementation Method 2
etching, using a second plasma that comprises oxygen, the hard mask layer to form an incremental portion of the recess
Data Source
AI summary
In certain embodiments, a method of forming a semiconductor device includes receiving a substrate having an etch mask layer that includes features for preserving corresponding portions of an underlying hard mask layer to be etched during an etching process. The method includes patterning the hard mask layer using the etch mask layer to gradually form a recess in the hard mask layer, the recess having a depth greater than a width of a top surface of a first feature of the etch mask layer, by performing the etching process. The etching process includes alternating between: depositing, using a first plasma, a silicon-containing protective layer over the etch mask layer and the hard mask layer such that the protective layer covers exposed surfaces of the hard mask layer; and subsequently etching, using a second plasma that comprises oxygen, the hard mask layer to form an incremental portion of the recess.