摘要:
A metrology system may include an illumination sub-system to illuminate a metrology target on a sample with illumination having a symmetric off-axis illumination profile, where the symmetric off-axis illumination profile is symmetric along one or more measurement directions, and where the illumination sub-system provides illumination from opposing angles in the symmetric off-axis illumination profile at least one of simultaneously or sequentially. The metrology target may include a first periodic structure on a first layer of the sample and a second periodic structure on a second layer of the sample. The metrology system may further include an imaging sub-system to generate images of the metrology target formed using two non-zero diffraction orders from each point of the symmetric off-axis illumination profile. The metrology subsystem may further determine an overlay error indicative of alignment between the first layer and the second layer based on the one or more images.
摘要:
Fourier filters and wafer inspection systems are provided. One embodiment relates to a one-dimensional Fourier filter configured to be included in a bright field inspection system such that the bright field inspection system can be used for broadband dark field inspection of a wafer. The Fourier filter includes an asymmetric illumination aperture configured to be positioned in an illumination path of the inspection system. The Fourier filter also includes an asymmetric imaging aperture complementary to the illumination aperture. The imaging aperture is configured to be positioned in a light collection path of the inspection system such that the imaging aperture blocks light reflected and diffracted from structures on the wafer and allows light scattered from defects on the wafer to pass through the imaging aperture.
摘要:
Systems and methods for providing illumination of a specimen for inspection are provided. One system includes one or more first optical elements configured to illuminate a diffuser with a predetermined pattern of coherent light. The system also includes one or more second optical elements configured to image light exiting the diffuser onto an illumination pupil of the system such that the predetermined pattern is reproduced in the illumination pupil. In addition, the system includes an objective lens configured to focus light from the predetermined pattern in the illumination pupil onto a specimen plane. In one embodiment, the light focused onto the specimen plane is not substantially coherent. In another embodiment, the predetermined pattern is selected based on an illumination mode selected for the inspection of the specimen.
摘要:
A system and method for maintaining focus in an imaging device; the imaging device having an objective lens with an optical axis, a stage for supporting a specimen, and a controller for controlling the stage-to-objective distance; the system comprising: one or more image sensors placed at a plurality of substantially different axial focal positions, and at least one computing device executing computer-readable instructions stored in its memory and configured to acquire images from each of the image sensors; the method comprising: computing a quantitative image characteristic for each of the images acquired by the computing device, computing an axial stage-to-objective distance correction based on the computed quantitative image characteristics and the plurality of axial focal positions, and causing the controller to adjust the axial stage-to-objective distance according to the computed axial stage-to-objective distance correction.
摘要:
Systems and methods for blocking specular reflection and suppressing modulation from periodic features on a specimen are provided. One inspection system configured to block specular reflection and suppress modulation in an image of a specimen includes an illumination subsystem configured to illuminate the specimen with a predetermined pattern of spatially incoherent light. The system also includes an optical element configured to block light reflected from periodic features formed on the specimen and at least some light diffracted from the periodic features. The system further includes a detector configured to detect light that passes through the optical element and to generate an image of the specimen in response to the detected light. The optical element blocks specular reflection and at least partially suppresses modulation in the image due to the periodic features. The system also includes a processor configured to detect defects on the specimen using the image.
摘要:
A system is provided herein for inspecting a specimen. In one embodiment, the system may include a dual-channel microscope, two illuminators, each coupled for illuminating a different channel of the dual-channel microscope and two detectors, each coupled to a different channel of the dual-channel microscope for acquiring images of the specimen. Means are provided for separating the channels of the dual-channel microscope, so that the two detectors can acquire the images of the specimen at substantially the same time. In one embodiment, the channels of the dual-channel microscope may be spectrally separated by configuring the two illuminators, so that they produce light in two substantially non-overlapping spectral ranges. In another embodiment, the channels of the dual-channel microscope may be spatially separated by positioning the two detectors, so that the illumination light do not overlap and the fields of view of the two detectors do not overlap within a field of view of an objective lens included within the system.
摘要:
Systems and methods for blocking specular reflection and suppressing modulation from periodic features on a specimen are provided. One inspection system configured to block specular reflection and suppress modulation in an image of a specimen includes an illumination subsystem configured to illuminate the specimen with a predetermined pattern of spatially incoherent light. The system also includes an optical element configured to block light reflected from periodic features formed on the specimen and at least some light diffracted from the periodic features. The system further includes a detector configured to detect light that passes through the optical element and to generate an image of the specimen in response to the detected light. The optical element blocks specular reflection and at least partially suppresses modulation in the image due to the periodic features. The system also includes a processor configured to detect defects on the specimen using the image.
摘要:
The invention may be embodied in a time delay integration (TDI) based sensor wafer inspection system that introduces controlled blur into the sampled image to suppress high spectral frequencies and thereby mitigate the occurrence of aliasing in the sampled image. Image blur may be introduced in the scan direction by desynchronizing the image motion (scan rate) from the charge transfer rate within the TDI sensor (sample clock rate). The scan rate may be desynchronized from the TDI sample clock rate by altering the speed of wafer movement, the sample clock rate, or the magnification of the imaging optics. Image blur may be introduced in the cross-scan direction by imparting a small alignment difference between the direction of image motion (image scan direction) and the direction that charges transfer within the TDI sensor (sensor direction).