Onto Innovation Inc.

Nicholas James Keller

George Andrew Antonelli

Kevin Eduard Heidrich

Robin Mair

Nigel P Smith

Manjusha Mehendale

Francis Scott Hoover

Overlay is determined for a device using signals measured from the device and a signal response to overlay determined from a plurality of calibration targets. Each calibration target has the same design as the device, but includes a known overlay shift. The calibration targets may be located in a scribe line, within a product area on the wafer, or on a separate calibration wafer. Each calibration target may have a different overlay shift, including zero overlay shift. The device may serve as a calibration target with zero overlay shift. The overlay shift may be in two orthogonal directions. The signal response to overlay may be determined based on a set of signals obtained from the calibration targets. A second set of signals may then be obtained from the device and the overlay determined based on the second set of signals and the determined signal response to overlay.

Multi-layer calibration for empirical overlay measurement

Characteristics of a standard logic cell, e.g., a random logic cell, are determined using an effective cell approximation. The effective cell approximation is smaller than the standard logic cell and represents the density of lines and spaces of the standard logic cell. The effective cell approximation may be produced based on a selected area from the standard logic cell and include the same non-periodic patterns as the selected area. The effective cell approximation, alternatively, may represent non-periodic patterns in the standard logic cell using periodic patterns having a same density of lines and spaces as found in the standard logic cell. A structure on the sample, such as a logic cell or a metrology target produced based on the effective cell approximation is measured to acquire data, which is compared to the data for the effective cell approximation to determine a characteristic of the standard logic cell.

Effective cell approximation model for logic structures

A metrology target is designed for measuring a feature at the bottom of a trench in a device under test, such as a tungsten recess vertical profile in a wordline in a three-dimensional (3D) NAND. The metrology target follows the design rules for the device under test and includes a tier stack with a plurality of tier stack pairs including, each including a conductor layer, such as tungsten, and an insulator layer, such as silicon dioxide and a trench that extends through the tier stack pairs. The metrology target includes a via that extends through the tier stack pairs and is positioned a lateral distance to the trench to promote access of light to a bottom of the trench, via plasmonic resonance, for measurement of a characteristic of the trench, such as the tungsten recess at the bottom of the wordline slit.

Target for optical measurement of trenches

A non-destructive opto-acoustic metrology device detects the presence and location of non-uniformities in a film stack that includes a large number, e.g., 50 or more, transparent layers. A transducer layer at the bottom of the film stack produces an acoustic wave in response to an excitation beam. A probe beam is reflected from the layer interfaces of the film stack and the acoustic wave to produce an interference signal that encodes data in a time domain from destructive and constructive interference as the acoustic wave propagates upward in the film stack. The data may be analyzed across the time domain to determine the presence and location of one or more non-uniformities in the film stack. An acoustic metrology target may be produced with a transducer layer configured to generate an acoustic wave with a desired acoustic profile based on characteristics of the film stack.

Opto-acoustic measurement of a transparent film stack

Grating-coupled surface plasmon resonance response of a calibration grating is used to calibrate the azimuth angle offset between a sample on the stage and the plane of incidence (POI) of the optical system of an optical metrology device. The calibration grating is configured to produce grating-coupled surface plasmon resonance in response to the optical characteristics of the optical metrology device. The calibration grating is coupled to the stage and positioned at a known azimuth angle with respect to the optical channel of the optical metrology device while the grating-coupled surface plasmon resonance response of the calibration grating is measured. The azimuth angle between an orientation of the calibration grating and the POI of the optical system is determined based on the grating-coupled surface plasmon resonance response. The determined azimuth angle may then be used to correct for an azimuth angle offset between the sample and the POI.

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La Jolla, CA, United States of America

Nicholas James Keller