Variable Pitch Semiconductor Fin Formation via Dual Mandrel SIT
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Solution Overview
Problem
The process window for cutting unwanted semiconductor fins is narrow at tight pitches, making it difficult to remove unwanted fins without affecting adjacent devices due to process variation and small lithographic margins, especially in integrated circuits with varying device densities.
Innovation Solution
A method involving the formation of semiconductor fins with variable pitches using a combination of first and second mandrel structures in a sidewall image transfer (SIT) process, where the second mandrel structures overlap and fill spaces between the first mandrel structures, allowing for the formation of spacers with arbitrary values, thereby expanding the process window for fin cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single set of mandrel structures is used in SIT process, then the manufacturing process is simple, but the process window for cutting unwanted fins is narrow at tight pitches
Solution Approach 1:
The patent divides the mandrel structure formation into two separate sets: first mandrel structures formed at a constant pitch, and second mandrel structures formed to fill spaces between selected first mandrels. This segmentation allows independent optimization of each set's pitch and spacing, creating larger process windows for fin cutting while maintaining manufacturing feasibility through sequential formation steps
2Productivity
If the pitch of semiconductor fins is decreased to increase density, then the device density increases, but the process window for removing unwanted fins decreases
Solution Approach 1:
The patent applies different pitch characteristics to different regions: first mandrel structures provide uniform spacing in high-density regions, while second mandrel structures are selectively formed to create variable spacing patterns. This local differentiation allows tight pitches where needed for density while maintaining adequate process windows by introducing spacing variations in specific locations
3Ease of manufacture
If conventional SIT process is used with uniform mandrel spacing, then the manufacturing is straightforward, but it cannot accommodate irregular device spacing requirements
Solution Approach 1:
The patent transitions from a static, uniform mandrel spacing approach to a dynamic, variable spacing approach. The second mandrel structures are selectively formed based on desired fin spacing patterns, allowing the system to adapt to different device density requirements. This dynamic configuration enables both regular and irregular spacing patterns while maintaining manufacturing feasibility through a systematic two-stage formation process
Data Source
AI summary
A method of forming semiconductor fins with variable pitches of arbitrary values in a sidewall image transfer (SIT) process is provided. After forming an array of first mandrel structures with a constant pitch and removing at least one first mandrel structure form the array, a set of second mandrel structures are formed overlapping the first mandrel structures. The combination of the first mandrel structures and the second mandrel structures defines pitches of sidewall spacer patterns to be subsequently formed.