Alignment Key Capping Layer for Semiconductor Etch Protection
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Solution Overview
Problem
Conventional methods for forming dual gate oxide layers in semiconductor devices result in reduced step height differences of alignment keys due to wet etch processes, leading to potential misalignment issues during subsequent fabrication processes.
Innovation Solution
A method of forming an alignment key with a capping layer that maintains a step height difference without additional mask formation processes, using a capping layer composed of materials with etch selectivity to protect the alignment key during subsequent wet etch processes, thereby preventing wear and maintaining precise alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a wet etch process is used to remove the first thermal oxide layer in the lower voltage region, then the dual gate oxide layer structure is formed, but the step height difference of the alignment key is reduced due to oxide layer wear
Solution Approach 1:
A capping layer is formed on the alignment key before the wet etch process that removes the first thermal oxide layer. This preliminary protective action prevents the oxide layer wear that would otherwise reduce the step height difference and compromise alignment precision in subsequent processes.
Solution Approach 2:
The capping layer acts as an intermediary protective element between the wet etch process and the alignment key's oxide layer. It selectively protects the alignment key region during etching while allowing the etch process to proceed in other regions, thereby maintaining the step height difference without requiring additional mask formation steps.
2Ease of manufacture
If the first thermal oxide layer is removed by wet etching to form the dual gate oxide layer, then the lower voltage region gate oxide is formed, but the alignment key oxide layer is worn down substantially
Solution Approach 1:
The capping layer is deposited on the alignment key before the wet etch process begins. This preliminary protective measure ensures that when the first thermal oxide layer is removed to form the dual gate oxide structure, the alignment key's oxide layer remains intact and maintains its step height difference.
Solution Approach 2:
The capping layer serves as a protective intermediary during the wet etch process. It allows the etching to proceed efficiently for forming the dual gate oxide layer while simultaneously protecting the alignment key from excessive oxide layer removal, thus maintaining alignment key integrity without complicating the manufacturing process.
3Productivity
If repeated wet etch processes are performed, then the fabrication steps are completed, but the alignment key becomes level with the substrate surface due to oxide layer removal
Solution Approach 1:
The capping layer is formed on the alignment key before any wet etch processes are performed. This preliminary protection ensures that even when multiple wet etch steps are conducted to complete the fabrication sequence, the alignment key maintains its step height difference and does not become level with the substrate surface.
Solution Approach 2:
The capping layer acts as a persistent protective intermediary throughout the repeated wet etch processes. It enables high fabrication throughput by allowing multiple etching steps to proceed efficiently while simultaneously preventing the cumulative oxide layer wear that would otherwise eliminate the alignment key's step height.
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 ensures accurate alignment by maintaining the step height difference of the alignment key, simplifying the fabrication process and preventing misalignment, without the need for additional mask formation steps.
Implementation Method 1
using a capping layer composed of materials with etch selectivity to protect the alignment key during subsequent wet etch processes
Data Source
AI summary
A method of forming an alignment key with a capping layer in a semiconductor device without an additional mask formation process, and a method of fabricating a semiconductor device using the same, may be provided. The method of forming an alignment key may include forming an isolation layer confining an active region in a chip region of a semiconductor substrate, and forming an alignment key having a step height difference with respect to the surface of the semiconductor substrate in a scribe lane. An at least one formation layer for forming an element may be formed on the substrate, and patterned, to form an element-forming pattern on the semiconductor substrate in the chip region, and a capping layer capping the alignment key on the semiconductor substrate in the scribe lane.