Abstract: An inspection system may generate first-step images of multiple sample regions after a first process step and generate second-step images of the sample regions after a second process step, where the second process step modifies the sample in at least one of the sample regions. The system may further identify one of the sample regions as a test region and at least some of the remaining sample regions as comparison regions, where the second-step image of the test region is a test image and the second-step images of the comparison regions are comparison images. The system may further generate a multi-step difference image by subtracting a combination of at least one of the second-step comparison images and at least two of the first-step images from the test image. The system may further identify defects in the test region associated with the second process step based on the multi-step difference image.

Abstract: An inspection system includes a controller including one or more processors configured to execute program instructions. The program instructions cause the one or more processors to receive at least a first portion of a first set of repeat swaths of a first scan path of a sample. The program instructions cause the one or more processors to generate an image by averaging the first portion of the first set of repeat swaths. Averaging the first portion of the first set of repeat swaths reduces a noise in the image. The program instructions cause the one or more processors to detect one or more defects in an inspection region of the sample using the image.

Abstract: An inspection system may generate first-step images of multiple sample regions after a first process step and generate second-step images of the sample regions after a second process step, where the second process step modifies the sample in at least one of the sample regions. The system may further identify one of the sample regions as a test region and at least some of the remaining sample regions as comparison regions, where the second-step image of the test region is a test image and the second-step images of the comparison regions are comparison images. The system may further generate a multi-step difference image by subtracting a combination of at least one of the second-step comparison images and at least two of the first-step images from the test image. The system may further identify defects in the test region associated with the second process step based on the multi-step difference image.

Abstract: Methods and systems for discovery of defects of interest (DOI) buried within three dimensional semiconductor structures and recipe optimization are described herein. The volume of a semiconductor wafer subject to defect discovery and verification is reduced by storing images associated with a subset of the total depth of the semiconductor structures under measurement. Image patches associated with defect locations at one or more focus planes or focus ranges are recorded. The number of optical modes under consideration is reduced based on any of a comparison of one or more measured wafer level defect signatures and one or more expected wafer level defect signatures, measured defect signal to noise ratio, and defects verified without de-processing. Furthermore, verified defects and recorded images are employed to train a nuisance filter and optimize the measurement recipe. The trained nuisance filter is applied to defect images to select the optimal optical mode for production.

Abstract: Disclosed are methods and apparatus for facilitating defect detection in a multilayer stack. The method includes selection of a set of structure parameters for modeling a particular multilayer stack and a particular defect contained within such particular multilayer stack and a set of operating parameters for an optical inspection system. Based on the set of structure and operating parameters, an electromagnetic simulation is performed of waves scattered from the particular multilayer stack and defect and arriving at a collection pupil of the optical inspection system.

Abstract: A three-dimensional calibration structure for measuring buried defects on a semiconductor device is disclosed. The three-dimensional calibration structure includes a defect standard wafer (DSW) including one or more programmed surface defects. The three-dimensional calibration structure includes a planarized layer deposited on the DSW. The three-dimensional calibration structure includes a layer stack deposited on the planarized layer. The layer stack includes two or more alternating layers. The three-dimensional calibration structure includes a cap layer deposited on the layer stack. One or more air gaps are formed in the layer stack following deposition of the cap layer. The three-dimensional calibration structure includes one or more holes formed into at least one of the cap layer, the layer stack, or the planarized layer.

Abstract: Methods and systems for improved detection and classification of defects of interest (DOI) on semiconductor wafers based on three-dimensional images are described herein. Three dimensional imaging of volumes of thick, layered structures enables accurate defect detection and estimation of defect location in three dimensions at high throughput. A series of images are acquired at a number of different wafer depths. A three dimensional image of a thick semiconductor structure is generated from the series of images. Defects are identified and classified based on an analysis of the three dimensional image of the thick semiconductor structure. In some examples, the three-dimensional image stack is visualized by contour plots or cross-sectional plots to identify a characteristic defect response. In some examples, the three-dimensional image is processed algorithmically to identify and classify defects. In another aspect, the location of a defect is estimated in three dimensions based on the three dimensional image.

Abstract: Disclosed are methods and apparatus for facilitating defect detection in a multilayer stack. The method includes selection of a set of structure parameters for modeling a particular multilayer stack and a particular defect contained within such particular multilayer stack and a set of operating parameters for an optical inspection system. Based on the set of structure and operating parameters, an electromagnetic simulation is performed of waves scattered from the particular multilayer stack and defect and arriving at a collection pupil of the optical inspection system.

Abstract: Systems and methods for determining information for defects on a wafer are provided. One system includes an illumination subsystem configured to direct light having one or more illumination wavelengths to a wafer. The one or more illumination wavelengths are selected to cause fluorescence from one or more materials on the wafer without causing fluorescence from one or more other materials on the wafer. The system also includes a detection subsystem configured to detect only the fluorescence from the one or more materials or to detect non-fluorescent light from the wafer without detecting the fluorescence from the one or more materials. In addition, the system includes a computer subsystem configured to determine information for defects on the wafer using output generated by the detection subsystem responsive to the detected fluorescence or the detected non-fluorescent light.

Abstract: Disclosed are methods and apparatus for facilitating defect detection in a multilayer stack. The method includes selection of a set of structure parameters for modeling a particular multilayer stack and a particular defect contained within such particular multilayer stack and a set of operating parameters for an optical inspection system. Based on the set of structure and operating parameters, an electromagnetic simulation is performed of waves scattered from the particular multilayer stack and defect and arriving at a collection pupil of the optical inspection system.

Abstract: Systems and methods for determining information for defects on a wafer are provided. One system includes an illumination subsystem configured to direct light having one or more illumination wavelengths to a wafer. The one or more illumination wavelengths are selected to cause fluorescence from one or more materials on the wafer without causing fluorescence from one or more other materials on the wafer. The system also includes a detection subsystem configured to detect only the fluorescence from the one or more materials or to detect non-fluorescent light from the wafer without detecting the fluorescence from the one or more materials. In addition, the system includes a computer subsystem configured to determine information for defects on the wafer using output generated by the detection subsystem responsive to the detected fluorescence or the detected non-fluorescent light.

Abstract: Methods and systems for selecting optical modes suitable for defect inspection are disclosed. A method may include: scanning a full-stack wafer of the particular type utilizing a set of optical modes to obtain a set of full-stack wafer images; and de-processing the full-stack wafer to produce a de-processed wafer based on a location of a potential defect of interest indicated by the set of full-stack wafer images to facilitate selection of optical modes suitable for defect inspection of wafers of the particular type.

Abstract: Systems and methods for determining information for defects on a wafer are provided. One system includes an illumination subsystem configured to direct light having one or more illumination wavelengths to a wafer. The one or more illumination wavelengths are selected to cause fluorescence from one or more materials on the wafer without causing fluorescence from one or more other materials on the wafer. The system also includes a detection subsystem configured to detect only the fluorescence from the one or more materials or to detect non-fluorescent light from the wafer without detecting the fluorescence from the one or more materials. In addition, the system includes a computer subsystem configured to determine information for defects on the wafer using output generated by the detection subsystem responsive to the detected fluorescence or the detected non-fluorescent light.

Abstract: Disclosed are methods and apparatus for optimizing a mode of an inspection tool. A first image or signal for each of a plurality of first apertures of the inspection tool is obtained, and each first image or signal pertains to a defect area. For each of a plurality of combinations of the first apertures and their first images or signals, a composite image or signal is obtained. Each composite image or signal is analyzed to determine an optimum one of the combinations of the first apertures based on a defect detection characteristic of each composite image. In one aspect, determining an optimum one of the combinations of the first apertures includes selecting a set of one or more individual apertures that result in the highest signal to noise ratio for the defect area, and the method includes setting the optimum combination of the first apertures on the inspection tool and inspecting a sample using such optimum combination of the first apertures.

Abstract: A three-dimensional calibration structure for measuring buried defects on a semiconductor device is disclosed. The three-dimensional calibration structure includes a defect standard wafer (DSW) including one or more programmed surface defects. The three-dimensional calibration structure includes a planarized layer deposited on the DSW. The three-dimensional calibration structure includes a layer stack deposited on the planarized layer. The layer stack includes two or more alternating layers. The three-dimensional calibration structure includes a cap layer deposited on the layer stack. One or more air gaps are formed in the layer stack following deposition of the cap layer. The three-dimensional calibration structure includes one or more holes formed into at least one of the cap layer, the layer stack, or the planarized layer.

Abstract: Methods and systems for discovery of defects of interest (DOI) buried within three dimensional semiconductor structures and recipe optimization are described herein. The volume of a semiconductor wafer subject to defect discovery and verification is reduced by storing images associated with a subset of the total depth of the semiconductor structures under measurement. Image patches associated with defect locations at one or more focus planes or focus ranges are recorded. The number of optical modes under consideration is reduced based on any of a comparison of one or more measured wafer level defect signatures and one or more expected wafer level defect signatures, measured defect signal to noise ratio, and defects verified without de-processing. Furthermore, verified defects and recorded images are employed to train a nuisance filter and optimize the measurement recipe. The trained nuisance filter is applied to defect images to select the optimal optical mode for production.

Abstract: Methods and systems for improved detection and classification of defects of interest (DOI) on semiconductor wafers based on three-dimensional images are described herein. Three dimensional imaging of volumes of thick, layered structures enables accurate defect detection and estimation of defect location in three dimensions at high throughput. A series of images are acquired at a number of different wafer depths. A three dimensional image of a thick semiconductor structure is generated from the series of images. Defects are identified and classified based on an analysis of the three dimensional image of the thick semiconductor structure. In some examples, the three-dimensional image stack is visualized by contour plots or cross-sectional plots to identify a characteristic defect response. In some examples, the three-dimensional image is processed algorithmically to identify and classify defects. In another aspect, the location of a defect is estimated in three dimensions based on the three dimensional image.

Abstract: Disclosed are methods and apparatus for optimizing a mode of an inspection tool. A first image or signal for each of a plurality of first apertures of the inspection tool is obtained, and each first image or signal pertains to a defect area. For each of a plurality of combinations of the first apertures and their first images or signals, a composite image or signal is obtained. Each composite image or signal is analyzed to determine an optimum one of the combinations of the first apertures based on a defect detection characteristic of each composite image. In one aspect, determining an optimum one of the combinations of the first apertures includes selecting a set of one or more individual apertures that result in the highest signal to noise ratio for the defect area, and the method includes setting the optimum combination of the first apertures on the inspection tool and inspecting a sample using such optimum combination of the first apertures.

Abstract: Disclosed are methods and apparatus for optimizing a mode of an inspection tool. A first image or signal for each of a plurality of first apertures of the inspection tool is obtained, and each first image or signal pertains to a defect area. For each of a plurality of combinations of the first apertures and their first images or signals, a composite image or signal is obtained. Each composite image or signal is analyzed to determine an optimum one of the combinations of the first apertures based on a defect detection characteristic of each composite image.

Abstract: Disclosed are methods and apparatus for inspecting a vertical semiconductor stack of a plurality of layers is disclosed. The method includes (a) on a confocal tool, repeatedly focusing an illumination beam at a plurality of focus planes at a plurality of different depths of a first vertical stack, wherein a defect is located at an unknown one of the different depths and the illumination beam has a wavelength range between about 700 nm and about 950 nm, (b) generating a plurality of in-focus images for the different depths based on in-focus output light detected from the first vertical stack at the different depths, wherein out-of-focus output light is inhibited from reaching the detector of the confocal system and inhibited from contributing to generation of the in-focus images, and (c) determining which one of the different depths at which the defect is located in the first vertical stack based on the in-focus images.