Reduced Height M1 Metal Lines Using Low Mean Free Path Materials
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Solution Overview
Problem
Conventional M1 metal lines in semiconductor devices face challenges in shrinking size due to increased RC delay and electromigration reliability issues, as reducing their height to lower capacitance compromises current density and reliability.
Innovation Solution
Forming M1 metal lines from materials with a lower mean free path than Copper, such as Tungsten, Molybdenum, or Ruthenium, which allows for reduced height and length while maintaining high electromigration reliability and lowering RC delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the height of M1 metal lines is reduced to lower capacitance and RC delay, then the RC delay is reduced, but the current density increases and electromigration reliability deteriorates
Solution Approach 1:
The patent changes the material parameter (mean free path) by selecting materials with lower mean free path than copper, such as tungsten, molybdenum, or ruthenium. This material substitution enables the metal line height to be reduced below conventional minimums while maintaining acceptable electromigration reliability, as these materials tolerate higher current densities better than copper. The parameter change in material selection resolves the contradiction by allowing simultaneous reduction in RC delay and maintenance of reliability.
Solution Approach 2:
The patent employs composite material structures by combining the low-mean-free-path metal material with specific dielectric materials and processing techniques. The use of materials like tungsten or molybdenum in conjunction with optimized dielectric layers creates a composite interconnection structure that achieves both low capacitance (through reduced height) and high reliability (through material properties resistant to electromigration).
2Productivity
If the size of M1 metal lines is reduced to enable scaling, then the device density is improved, but the RC delay increases due to increased resistance and capacitance
Solution Approach 1:
The patent changes the physical parameter of metal line height to a value below conventional minimums by using materials with lower mean free path. This parameter change allows the metal lines to be made thinner while maintaining electrical performance, thereby reducing capacitance and RC delay even as device density increases. The material substitution enables continued scaling without the usual RC delay penalty.
3Reliability
If conventional design rules are followed to ensure electromigration reliability, then the reliability is maintained, but the minimum size restrictions prevent further scaling
Solution Approach 1:
The patent fundamentally changes the material parameter by selecting metals with lower mean free path than copper. This parameter change in material selection allows the design rules to be relaxed, enabling metal line dimensions to be reduced below conventional minimums while maintaining electromigration reliability. The new material properties permit continued layout scaling that would otherwise be prohibited by traditional copper-based design rules.
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 enables the scaling of M1 metal lines to smaller sizes than conventional Copper-based lines, achieving lower capacitance and RC delays without compromising electromigration reliability, thus improving the layout scaling of semiconductor devices.
Implementation Method 1
a reduced height M1 metal line formed of a material with lower mean free path than Copper
Data Source
AI summary
Systems and methods are directed to an integrated circuit comprising a reduced height M1 metal line formed of an exemplary material with lower mean free path than Copper, for local routing of on-chip circuit elements of the integrated circuit, wherein the height of the reduced height M1 metal line is lower than a minimum allowed or allowable height of a conventional M1 metal line formed of Copper. The exemplary materials for forming the reduced height M1 metal line include Tungsten (W), Molybdenum (Mo), and Ruthenium (Ru), wherein these exemplary materials also exhibit lower capacitance and lower RC delays than Copper, while providing high electromigration reliability.