Self-Aligned Double Patterning Spacer Formation
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Solution Overview
Problem
The down-scaling of semiconductor devices has reached limits in photolithography, where the spacing between elements (pitch) is smaller than what can be manufactured using traditional optical masks and equipment, leading to challenges in semiconductor fabrication.
Innovation Solution
A method involving the formation of mandrels and spacers in a semiconductor structure, where spacers are formed around mandrels, and then the mandrels are removed, allowing for the patterning of conductive lines and vias with improved overlay alignment and reduced spacer residues, thereby expanding the photolithographic and etching process windows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional photolithography equipment and optical masks are used, then the manufacturing process is simple, but the pitch between elements cannot be reduced below a certain limit
Solution Approach 1:
The patent applies segmentation by dividing the patterning process into multiple stages: first forming mandrels at a relaxed pitch, then forming spacers around the mandrels to create the final fine-pitch pattern. This multi-step segmentation enables achieving smaller pitch values that cannot be obtained through single-step photolithography, directly resolving the contradiction between manufacturing precision and process complexity.
2Manufacturing precision
If mandrels and spacers are formed to achieve smaller pitch, then the pitch precision is improved, but spacer residues and damage occur
Solution Approach 1:
The patent applies preliminary action by performing a controlled etch process on the spacers before removing the mandrels. This preliminary etching removes potential spacer residues and strengthens the spacers against subsequent processing, preventing spacer damage while maintaining the achieved pitch precision. The mandrels are then removed, leaving clean, intact spacer structures that define the final pattern.
Data Source
AI summary
A method for fabrication of a semiconductor structure according to some embodiments of the present disclosure comprises following steps. A first mandrel is formed over a target layer over a substrate, wherein the first mandrel comprises a mandrel island connecting a first mandrel strip and a second mandrel strip. A first spacer is formed along first and second sidewalls of the mandrel island, the first mandrel strip, and the second mandrel strip. The first mandrel is then removed, and the target layer is patterned with the first spacer remains over the target layer. The first mandrel strip and the second mandrel strip are misaligned from one another.