Metrology Targets with Filling Elements to Reduce CMP Dishing
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Solution Overview
Problem
Common metrology targets with empty background regions between target elements lead to inaccuracies such as the dishing effect and rotation term errors during the Chemical Mechanical Polishing (CMP) process, causing uneven layer formation and asymmetric polishing.
Innovation Solution
Introducing specified filling elements into identified continuous regions of the target design, with parameters determined by a trade-off between contrast and inaccuracy requirements, to prevent asymmetric polishing and maintain optical contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If empty background regions are used between target elements, then optical contrast is improved, but dishing effect and rotation term increase causing measurement inaccuracies
Solution Approach 1:
The empty background region is segmented into multiple sub-regions by introducing filling elements (such as trenches, vias, or patterned structures) that divide the continuous empty space into discrete sections. This segmentation reduces the dishing effect by preventing large continuous empty regions from causing uneven material removal during CMP, while still maintaining adequate optical contrast for measurement purposes.
Solution Approach 2:
Different regions of the background are given different properties by introducing filling elements with specific characteristics (material composition, depth, pattern density) in localized areas. This allows the target design to optimize for both contrast and accuracy locally - some regions maintain emptiness for contrast while others have filling elements to prevent dishing and rotation effects.
2Manufacturing precision
If filling elements are introduced into continuous regions, then dishing effect and rotation term are reduced, but optical contrast may be compromised
Solution Approach 1:
Instead of completely filling the background region (which would eliminate contrast), filling elements are introduced partially - using materials with intermediate refractive indices, partial depth filling, or sparse patterning that provides enough structural support to reduce dishing while leaving sufficient empty space to maintain optical contrast for measurements.
Solution Approach 2:
The parameters of the filling elements (material composition, depth, width, pattern density, refractive index) are carefully adjusted to find the optimal balance point where the dishing and rotation effects are sufficiently reduced while the optical contrast remains above the threshold required for accurate measurements.
Data Source
AI summary
The subject application relates to metrology targets with filling elements that reduce inaccuracies and maintain contrast. The present invention provides a metrology target and a method to design the metrology target. The metrology target comprises specified filling elements introduced into identified continuous regions in a given target design, wherein parameters of the introduced filling elements are determined by a trade-off between a contrast requirement and an inaccuracy requirement which is associated via production with the identified continuous regions. The method includes the steps of identifying continuous regions in a target design, and introducing specified filling elements into the identified continuous regions, wherein parameters of the introduced filling elements are determined by a trade-off between a contrast requirement and an inaccuracy requirement which is associated via production with the identifying continuous regions. At least one of the identifying and the introducing can be carried out by at least one computer processor.