Kla Corporation

Kla Tencor Corporation

Evgeni Gurevich

Yoel Feler

Vladimir Levinski

Mark Ghinovker

Roel Gronheid

Sharon Aharon

Anna Golotsvan

Diana Shaphirov

Amnon Manassen

Michael E Adel

Daniel Kandel

Barak Bringoltz

Ohad Bachar

Nuriel Amir

Alexander Svizher

Tal Marciano

Dana Klein

Yuval Lamhot

Boris Efraty

Dror Alumot

Ido Adam

Lilach Saltoun

Nadav Carmel

Tal Yaziv

Noga Sella

Tom Leviant

Ofer Zaharan

Oded Kaminsky

Amir Handelman

Ze'ev Lindenfeld

Zeng Zhao

Moshe Cooper

Roee Sulimarski

Eltsafon Ashwal

Yaron Deleeuw

A metrology target may include a first rotationally symmetric working zone with one or more instances of a first pattern and a second rotationally-symmetric working zone with one or more instances of a second pattern, where at least one of the first pattern or the second pattern is a Moiré pattern formed from a first grating structure with a first pitch along a measurement direction on a first sample layer and a second grating structure with a second pitch different than the first pitch along the measurement direction on a second sample layer. Centers of rotational symmetry of the first and second working zones may overlap by design when an overlay error between the first sample layer and the second layer is zero. A difference between the centers of rotational symmetry of the first and second working zones may indicate an overlay error between the first and second sample layers.

Imaging overlay targets using moiré elements and rotational symmetry arrangements

Metrology methods and targets are provided for reducing or eliminating a difference between a device pattern position and a target pattern position while maintaining target printability, process compatibility and optical contrast—in both imaging and scatterometry metrology. Pattern placement discrepancies may be reduced by using sub-resolved assist features in the mask design which have a same periodicity (fine pitch) as the periodic structure and/or by calibrating the measurement results using PPE (pattern placement error) correction factors derived by applying learning procedures to specific calibration terms, in measurements and/or simulations. Metrology targets are disclosed with multiple periodic structures at the same layer (in addition to regular target structures), e.g., in one or two layers, which are used to calibrate and remove PPE, especially when related to asymmetric effects such as scanner aberrations, off-axis illumination and other error sources.

Reduction or elimination of pattern placement error in metrology measurements

Metrology methods and targets are provided for reducing or eliminating a difference between a device pattern position and a target pattern position while maintaining target printability, process compatibility and optical contrast&#x2014;in both imaging and scatterometry metrology. Pattern placement discrepancies may be reduced by using sub-resolved assist features in the mask design which have a same periodicity (fine pitch) as the periodic structure and/or by calibrating the measurement results using PPE (pattern placement error) correction factors derived by applying learning procedures to specific calibration terms, in measurements and/or simulations. Metrology targets are disclosed with multiple periodic structures at the same layer (in addition to regular target structures), e.g., in one or two layers, which are used to calibrate and remove PPE, especially when related to asymmetric effects such as scanner aberrations, off-axis illumination and other error sources.

A metrology target may include a first rotationally symmetric working zone with one or more instances of a first pattern and a second rotationally-symmetric working zone with one or more instances of a second pattern, where at least one of the first pattern or the second pattern is a Moir&#xe9; pattern formed from a first grating structure with a first pitch along a measurement direction on a first sample layer and a second grating structure with a second pitch different than the first pitch along the measurement direction on a second sample layer. Centers of rotational symmetry of the first and second working zones may overlap by design when an overlay error between the first sample layer and the second layer is zero. A difference between the centers of rotational symmetry of the first and second working zones may indicate an overlay error between the first and second sample layers.

Imaging overlay targets using Moir&#xe9; elements and rotational symmetry arrangements

A metrology system and metrology methods are disclosed. The metrology system includes an illumination sub-system, a collection sub-system, a detector, and a controller. The controller is configured to receive an image of an overlay target on a sample, determine an apparent overlay between two working zones along a measurement direction based on the image, and calculate an overlay between the two sample layers by dividing the apparent overlay by a Moir&#xe9; gain to compensate for Moir&#xe9; interference.

Misregistration metrology by using fringe Moir&#xe9; and optical Moir&#xe9; effects

Methods are provided for designing metrology targets and estimating the uncertainty error of metrology metric values with respect to stochastic noise such as line properties (e.g., line edge roughness, LER). Minimal required dimensions of target elements may be derived from analysis of the line properties and uncertainty error of metrology measurements, by either CDSEM (critical dimension scanning electron microscopy) or optical systems, with corresponding targets. The importance of this analysis is emphasized in view of the finding that stochastic noise may have increased importance with when using more localized models such as CPE (correctables per exposure). The uncertainty error estimation may be used for target design, enhancement of overlay estimation and evaluation of measurement reliability in multiple contexts.

Determining the impacts of stochastic behavior on overlay metrology data

Methods are provided for deriving a partially continuous dependency of metrology metric(s) on recipe parameter(s), analyzing the derived dependency, determining a metrology recipe according to the analysis, and conducting metrology measurement(s) according to the determined recipe. The dependency may be analyzed in form of a landscape such as a sensitivity landscape in which regions of low sensitivity and/or points or contours of low or zero inaccuracy are detected, analytically, numerically or experimentally, and used to configure parameters of measurement, hardware and targets to achieve high measurement accuracy. Process variation is analyzed in terms of its effects on the sensitivity landscape, and these effects are used to characterize the process variation further, to optimize the measurements and make the metrology both more robust to inaccuracy sources and more flexible with respect to different targets on the wafer and available measurement conditions.

Method of analyzing and utilizing landscapes to reduce or eliminate inaccuracy in overlay optical metrology

Growing community of inventors

Yoqneam Ilit, Israel

Evgeni Gurevich