Double-Patterned Lithography Interconnects for 28nm Precision
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Solution Overview
Problem
Forming crossovers and desired lateral dimensions in metal interconnects within integrated circuits at technology nodes beyond 28 nanometers using 193 nanometer illumination sources is challenging, requiring multiple pattern steps and affecting fabrication costs and yield.
Innovation Solution
A process involving the formation of first and second interconnect patterns in parallel route tracks, with leads extending to specific points, allowing for metal interconnect line formation with lateral separation that facilitates crossover to adjacent tracks, using photolithography with dipole component illumination sources to achieve desired pitch distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If 193 nanometer illumination sources are used for technology nodes at and beyond 28 nanometers, then fabrication costs may be reduced, but manufacturing precision deteriorates making it difficult to obtain desired first metal interconnect layouts
Solution Approach 1:
The patent applies segmentation by dividing the metal interconnect formation into multiple pattern steps. Instead of attempting to form all metal interconnect features in a single lithography exposure, the process segments the patterning into sequential steps, where each step forms a portion of the final interconnect layout. This allows the use of 193nm illumination sources while achieving sub-28nm precision through cumulative pattern formation.
2Manufacturing precision
If multiple pattern steps are used to achieve desired metal interconnect layouts, then manufacturing precision improves, but device complexity increases
Solution Approach 1:
The patent employs preliminary action by forming mandrel patterns and spacer structures in advance of the final metal interconnect formation. These preliminary structures serve as templates that guide subsequent patterning steps. The mandrels are formed first, then spacers are deposited and patterned around them, creating a predetermined framework that simplifies later processing steps and ensures precise final dimensions.
3Manufacturing precision
If desired lateral dimensions are achieved in metal interconnects, then manufacturing precision improves, but fabrication yield deteriorates due to difficulty in forming crossovers and u-turns
Solution Approach 1:
The patent introduces intermediary structures (mandrels and spacers) that mediate between the lithography process and the final metal interconnect formation. These intermediary elements act as temporary templates that enable precise lateral dimension control while facilitating complex geometries like crossovers and u-turns. The spacers, in particular, serve as intermediaries that define critical dimensions and enable features that would be difficult to form directly through lithography alone.
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 simplifies the formation of metal interconnects, enabling efficient crossover formation and maintaining desired dimensions, thereby improving fabrication yield and reducing costs by using a two-step interconnect pattern process with dipole component illumination.
Implementation Method 1
photolithography processes with illuminations sources having wavelengths more than twice a desired pitch distance
Implementation Method 2
photolithography with dipole component illumination sources to achieve desired pitch distances
Data Source
AI summary
An integrated circuit may be formed by a process of forming a first interconnect pattern in a plurality of parallel route tracks, and forming a second interconnect pattern in the plurality of parallel route tracks. The first interconnect pattern includes a first lead pattern which extends to a first point in an instance of the first plurality of parallel route tracks, and the second interconnect pattern includes a second lead pattern which extends to a second point in the same instance of the plurality of parallel route tracks, such that the second point is laterally separated from the first point by a distance one to one and one-half times a space between adjacent parallel lead patterns in the plurality of parallel route tracks. A metal interconnect formation process is performed which forms metal interconnect lines in an interconnect level defined by the first interconnect pattern and the second interconnect pattern.