Double Sidewall Image Transfer for Variable Fin Pitch Control
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Solution Overview
Problem
Traditional single sidewall image transfer (SIT) methods in semiconductor device fabrication are limited to generating fins with a fin pitch greater than 40 nm and result in inefficient use of layout area, as they cannot produce fins with a variable fin pitch.
Innovation Solution
A method involving the use of first and second mandrels with different widths and spacings, along with first and second spacers, to create a variable fin pitch by etching a substrate using these spacers as masks, allowing for the formation of fins with varying distances between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional single sidewall image transfer (SIT) methods are used, then fins can be generated, but the fin pitch is limited to greater than 40 nm
Solution Approach 1:
The patent divides the single SIT process into two sequential SIT operations. First mandrels are formed and a first spacer is deposited to create intermediate structures. Then the first mandrels are removed and a second spacer is deposited to form the final fins. This segmentation enables independent control of spacer deposition parameters, allowing fin pitch to be reduced below 40 nm while maintaining manufacturing precision.
Solution Approach 2:
The first spacer is deposited as a preliminary structure that serves as a temporary mandrel for the second spacer formation. This preliminary action creates an intermediate pattern that enables subsequent fin formation with reduced pitch. The first spacer's dimensions and material properties are optimized in advance to facilitate the final fin geometry and pitch requirements.
2Ease of manufacture
If traditional single SIT methods are used, then fins with constant pitch are generated, but layout area efficiency is reduced
Solution Approach 1:
The patent applies different mandrel widths and spacing configurations at different locations to create variable fin pitch. By locally adjusting the first and second mandrel dimensions and their relative positions, fins with different pitches can be formed in different regions of the substrate. This enables optimization of layout area efficiency by placing fins with smaller pitch where higher density is needed, while maintaining ease of manufacture through a systematic process approach.
3Manufacturing precision
If first and second mandrels with different widths and spacings are used, then variable fin pitch less than 40 nm can be achieved, but process complexity increases
Solution Approach 1:
The patent combines multiple functions into the spacer deposition steps. The first spacer serves both as a structural element defining intermediate patterns and as a temporary mandrel for second spacer formation. Similarly, the second spacer formation simultaneously removes first mandrels and creates final fin patterns. This merging reduces the number of separate process steps needed, managing complexity while achieving precise variable fin pitch control.
Data Source
AI summary
Methodology enabling a generation of fins having a variable fin pitch less than 40 nm, and the resulting device are disclosed. Embodiments include: forming a hardmask on a substrate; providing first and second mandrels on the hardmask; providing a first spacer on each side of each of the first and second mandrels; removing the first and second mandrels; providing, after removal of the first and second mandrels, a second spacer on each side of each of the first spacers; and removing the first spacers.