Rounded Mask Corners for Void-Free Interconnect Filling
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Solution Overview
Problem
The reduction of feature sizes in semiconductor devices poses challenges for interconnect fabrication, particularly with the use of low dielectric constant materials, which can lead to void formation and adverse effects due to undercut formation in dielectric layers during the fabrication of metal interconnects.
Innovation Solution
The method involves forming mask layers with rounded corners to improve filling characteristics of openings in dielectric layers, using specific materials and etch processes to avoid undercut formation and enhance the filling of interconnect structures, thereby reducing voids and improving the reliability of interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If low dielectric constant materials are used as insulating materials between interconnects, then the dielectric constant is reduced, but useful material properties required for interconnect fabrication deteriorate
Solution Approach 1:
The patent applies parameter changes by modifying the etch process parameters (chemistry, temperature, pressure) to achieve selective etching that rounds mask corners without damaging the low-k dielectric material. This allows the use of low-dielectric-constant materials while maintaining fabrication reliability through optimized process parameters.
Solution Approach 2:
The patent implements local quality by creating different surface profiles at different locations: sharp corners in the opened regions for good conductive fill, and rounded corners at mask boundaries to prevent undercut formation. This localized differentiation allows simultaneous achievement of low dielectric constant and good fabrication properties.
2Productivity
If conventional etch processes are used to form openings in dielectric layers, then openings are formed efficiently, but undercut formation occurs leading to voids in interconnect structures
Solution Approach 1:
The patent applies preliminary action by pre-rounding the mask layer corners before forming the openings in the dielectric layer. This preliminary modification of the mask geometry prevents undercut formation during etching, eliminating voids in the final interconnect structures while maintaining efficient opening formation.
Solution Approach 2:
The patent implements preliminary anti-action by using a specially designed etch process that counteracts the tendency to form undercuts. The etch chemistry and parameters are optimized to etch vertically without lateral erosion, preventing the harmful undercut effect before it can occur.
3Measurement precision
If mask layers with sharp corners are used, then opening definition is precise, but filling characteristics of openings deteriorate due to undercut formation
Solution Approach 1:
The patent applies local quality by differentiating the corner geometry of mask layers based on location: corners that will define opening positions are kept sharp for precise opening definition, while corners at mask boundaries are rounded to prevent undercut formation and improve filling characteristics. This localized differentiation resolves the contradiction between precision and fillability.
Solution Approach 2:
The patent implements spheroidality by rounding specific mask corners with a controlled radius of curvature. This curvature modification at critical locations prevents the formation of undercuts and improves conductive material filling, while maintaining sharp edges where precise opening definition is required.
Data Source
AI summary
Semiconductor devices and methods of forming the same are disclosed. A dielectric layer is formed over an underlying layer. A first mask layer and a second mask layer are formed on the dielectric layer such that the first mask layer is interposed between the second mask layer and the dielectric layer. An opening is formed in the first mask layer, the second mask layer and the dielectric layer. Subsequently, the second mask layer is removed. The opening is extended and corners of the first mask layer are rounded. A conductive feature is formed in the extended opening.