Pitch-Halving IC Process for Dense Conductive Lines
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Solution Overview
Problem
The existing photolithography processes struggle to form dense conductive lines and their contact pads beyond lithographic resolution, particularly in high-density memory arrays like DRAM, due to limitations in pitch reduction and contact pad formation at line ends.
Innovation Solution
A pitch-halving IC process is developed, where parallel base line patterns are formed with alternately arranged hammerhead patterns, trimmed, and spacers are created on their sidewalls. The base line patterns are removed, leaving derivative line patterns and loop patterns that form contact pads, allowing for sufficient spacing and high die-area utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If spacer forming technique is used to reduce pitch beyond lithographic resolution, then conductive line density is improved, but contact pad formation becomes difficult due to insufficient spacing
Solution Approach 1:
The patent segments the contact pad formation process by creating separate contact hole patterns through a second lithography step after the spacer-formed conductive lines are established. This allows contact pads to be formed independently at optimized dimensions and spacing, decoupling the contact pad geometry from the conductive line pitch constraints.
Solution Approach 2:
The patent introduces a vertical dimension by forming contact holes through the spacer structures and underlying layers. This third dimension (depth) allows contact pads to be positioned at specific depths while maintaining sufficient lateral spacing, resolving the conflict between high-density line spacing and adequate contact pad separation.
2Reliability
If contact pads are formed with sufficient width for electrical contact, then electrical connectivity is improved, but spacing between contact pads increases reducing die-area utilization
Solution Approach 1:
The patent nests the contact hole formation within the spacer structures, where the spacers serve as both the conductive interconnects and the sidewall definitions for contact hole placement. This nesting allows contact pads to be precisely positioned at the spacer ends with minimal lateral offset, maximizing die-area utilization while ensuring adequate contact dimensions.
Solution Approach 2:
The patent replaces traditional lateral contact pad definition with vertical contact hole formation through the spacer structures. Instead of defining contact pads purely in the lateral plane (which conflicts with line density), the contact access is achieved through the vertical dimension, allowing sufficient contact width for reliability while maintaining compact lateral footprint for high die-area utilization.
3Manufacturing precision
If hammerhead patterns are arranged densely to increase line density, then conductive line spacing is improved, but overlay registration difficulty increases
Solution Approach 1:
The patent performs preliminary trimming of the hammerhead patterns and spacers before final contact hole formation. This preliminary action establishes precise reference dimensions and positions that guide subsequent lithography steps, improving overlay registration by providing well-defined alignment targets even at high densities.
Solution Approach 2:
The patent changes the critical parameters from lateral dimensions to vertical dimensions for contact hole definition. By using the spacer height and depth as the primary control parameter for contact pad positioning rather than lateral hammerhead pattern dimensions, the method maintains overlay registration accuracy while achieving higher lateral line density.
Data Source
AI summary
A pitch-halving IC process is described. Parallel base line patterns are formed over a substrate, each being connected with a hammerhead pattern at a first or second side of the base line patterns, wherein the hammerhead patterns are arranged at the first side and the second side alternately, and the hammerhead patterns at the first or second side are arranged in a staggered manner. The above patterns are trimmed. A spacer is formed on the sidewalls of each base line pattern and the corresponding hammerhead pattern, including a pair of derivative line patterns, a loop pattern around the hammerhead pattern, and a turning pattern at the other end of the base line pattern. The base line patterns and the hammerhead patterns are removed. A portion of each loop pattern and at least a portion of each turning pattern are removed to disconnect each pair of derivative line patterns.