BEOL Metal Via Geometry for Conformal Deposition
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Solution Overview
Problem
Conventional BEOL metal structures face challenges with defects such as pinholes and surface corrosion due to the bulging of metal materials during deposition, particularly in square or rectangular via openings, leading to yield loss and reliability issues.
Innovation Solution
The BEOL metal structure incorporates a metal via with at least eight sides and a metal wire, both featuring a continuous conformal metal layer, with interior angles of 135° or more, and a passivation layer to prevent corrosion, using a conformal metal deposition process like PVD and CVD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conformal metal deposition process is used to form metal vias and wires, then the metal layer continuity is improved, but metal bulging and divot formation occur leading to pinholes and surface corrosion
Solution Approach 1:
The patent applies curvature by replacing sharp corners with rounded corners in the via openings. The via openings are formed with rounded corners having a radius of curvature of about 0.5 micrometers to 2 micrometers. This curvature prevents metal bulging at the corners during conformal deposition, eliminating divot formation and subsequent pinholes while maintaining continuous metal layer coverage.
2Ease of manufacture
If square or rectangular via openings are used, then the manufacturing process is simpler, but metal bulging at corners causes pinholes and reliability issues
Solution Approach 1:
The patent modifies the via opening geometry from square or rectangular with sharp corners to rounded corners. The rounded corners are formed by depositing a mandrel material and etching, creating via openings with a radius of curvature of about 0.5 micrometers to 2 micrometers. This geometric modification prevents metal bulging during deposition, eliminating the reliability issues associated with sharp-cornered vias while remaining manufacturable.
3Productivity
If conventional metal deposition is used in square via openings, then deposition speed is maintained, but incomplete passivation coverage occurs leading to surface corrosion
Solution Approach 1:
The patent uses rounded corner via openings that enable complete conformal deposition coverage. The curved geometry eliminates sharp corners where metal accumulation and incomplete coverage problems occur. This allows the passivation layer to uniformly cover the entire metal surface including corner regions, ensuring complete protection against surface corrosion while maintaining efficient deposition speeds.
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 configuration prevents bulging and divots, ensuring complete passivation coverage and preventing surface corrosion, thereby enhancing the reliability and yield of BEOL metal structures.
Implementation Method 1
a conformal metal deposition process (e.g., physical vapor deposition (PVD))
Implementation Method 2
a conformal metal deposition process (e.g., physical vapor deposition (PVD)) such that the metal via and the metal wire include respective portions of a continuous conformal metal layer. A passivation layer can subsequently be formed (e.g., by chemical vapor deposition (CVD))
Data Source
AI summary
Disclosed are embodiments of a back end of the line (BEOL) metal structure that includes, within a metal level, a metal via, which has at least eight sides and all interior angles at 135° or more, and a metal wire thereon. The metal wire and via include respective portions of a continuous conformal metal layer. A passivation layer coats the top surface of the metal layer. The metal via and the metal wire thereon can be in an upper metal level and can be made of one metal (e.g., aluminum or an aluminum alloy). The upper metal level can be above a lower metal level that similarly includes a metal via and metal wire thereon, but the metal used can be different (e.g., copper) and/or the shape of the via can be different (e.g., four-sided). Also disclosed herein are method embodiments for forming the above-described BEOL metal structure.