Hard Mask Removal on SOI Substrates via Selective Wet Etching
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Solution Overview
Problem
Conventional methods for removing hard mask material from SOI substrates, such as CMP processes, result in thickness variations and recess depth issues, leading to leakage current and substrate warpage, which are not suitable for 22 nm technology and beyond due to the presence of the BOX layer.
Innovation Solution
A method involving the deposition of a blocking layer on the hard mask and trench sidewalls, followed by a selective wet etching process to remove the hard mask material without using CMP, ensuring controlled recess depth and preventing BOX layer damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a CMP process is used to remove hard mask material on an SOI substrate, then the hard mask material can be removed, but thickness variation and recess depth variation occur leading to leakage current and substrate warpage
Solution Approach 1:
The patent segments the hard mask removal process into multiple controlled steps: depositing a first material layer, forming a patterned mask, etching through the hard mask, depositing a second material layer, and selectively removing materials. This segmentation allows precise control over removal depth and prevents uniformity issues associated with CMP processes
Solution Approach 2:
The patent performs preliminary actions by depositing the first material layer and forming the patterned mask before etching the hard mask. This preliminary structuring enables controlled and uniform hard mask removal without the need for CMP, thereby maintaining substrate integrity while achieving consistent thickness
2Ease of manufacture
If a wet process is used to remove hard mask material, then the process is simple and cost-effective, but the BOX layer in SOI substrates prevents effective hard mask removal
Solution Approach 1:
The patent introduces an intermediary patterned mask structure formed from the first material layer that enables selective access to the hard mask. This intermediary structure allows the etch process to remove hard mask material effectively through the mask openings while being protected elsewhere, overcoming the BOX layer barrier without requiring complex CMP equipment
Solution Approach 2:
The patent applies local quality by creating a patterned mask with specific openings that target only the regions where hard mask removal is needed. This localized approach allows effective hard mask removal in specific areas while maintaining the BOX layer integrity in other regions, achieving both process simplicity and removal efficiency
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 effectively removes the hard mask material while maintaining the integrity of the SOI substrate, reducing the risk of recess depth variation and substrate warpage, thereby improving the yield of embedded DRAM devices.
Implementation Method 1
depositing a blocking layer on a top surface of the hard mask layer
Implementation Method 2
depositing a blocking layer on a top surface of the hard mask layer
Implementation Method 3
selective wet etch process to remove the hard mask material
Data Source
AI summary
A hard mask material is removed from an SOI substrate without using a chemical mechanical polish (CMP) process. A blocking material is deposited on a hard mask material after a deep trench reactive ion etch (RIE) process. The blocking material on top of the hard mask material is removed. A selective wet etching process is used to remove the hard mask material. Trench recess depth is effectively controlled.