Multilayer Contact Etch Stop for Semiconductor Device
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Solution Overview
Problem
In semiconductor processing, removing metal oxide from metal gates after etching contact holes is challenging, as it often results in the undesired removal of material from the bottom of the contact hole, degrading the semiconductor device's performance.
Innovation Solution
A contact etch stop layer comprising a first silicon nitride layer, a silicon oxide layer, and a second silicon nitride layer is used to protect the active area during etching and metal oxide removal, with specific thicknesses and processes like sputtering and SiCoNi pre-clean to minimize material loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal oxide is removed from the metal gate using conventional methods, then the metal oxide is removed, but material at the bottom of the contact hole is undesirably removed, degrading device performance
Solution Approach 1:
The patent divides the protective layer into multiple segments: a first silicon nitride layer (200-400 Å thick) and a second silicon nitride layer (50-100 Å thick), separated by a silicon oxide layer (50-100 Å thick). This segmented structure allows differential protection during etching processes, where each layer serves specific functions in protecting different regions during sequential etching steps to remove metal oxide while preserving contact hole bottom material
Solution Approach 2:
The patent applies different material properties and thicknesses at different locations. The first silicon nitride layer is thicker (200-400 Å) to provide robust protection during contact hole etching, while the second silicon nitride layer is thinner (50-100 Å) for metal oxide removal protection. The silicon oxide layer in between provides selective etching resistance, creating locally optimized protection qualities for different process stages
2Loss of substance
If a protective layer is applied to prevent material loss at the contact hole bottom, then material loss is reduced, but the process complexity increases
Solution Approach 1:
The patent applies the multi-layer contact etch stop structure before the metal oxide removal process. By pre-configuring the first silicon nitride layer, silicon oxide layer, and second silicon nitride layer in advance, the system establishes protective barriers that automatically function during subsequent etching and sputtering processes, preventing material loss without requiring real-time intervention or complex in-process adjustments
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 reduces the loss of surface material at the bottom of the contact hole, improving the semiconductor device's performance by protecting the active area and maintaining the integrity of the metal silicide region.
Implementation Method 1
The removing of the metal oxide on the metal gate can comprise a sputtering process. The sputtering process may include a physical vapor deposition process
Implementation Method 2
removing a portion of the second silicon nitride layer that is disposed at the bottom of the contact hole by a SiCoNi pre-clean process
Data Source
AI summary
A method for manufacturing a semiconductor device includes forming a contact etch stop layer on an active area of a substrate that has a gate stack formed thereon. The gate stack includes a metal gate and a metal oxide. The contact etch stop layer includes a silicon oxide layer sandwiched between a first silicon nitride layer and a second silicon nitride layer that is disposed on the active area. The method further includes forming a contact hole extending through an interlayer dielectric layer on the first silicon nitride layer using the first silicon nitride layer as a protection for the active area, removing a portion of the first silicon nitride layer disposed at the bottom of the contact hole using the silicon oxide layer as a protection for the active area, and removing the metal oxide using the second silicon nitride layer as a protection for the active area.