Abstract: A method is described for characterizing defects on a test surface of a semiconductor wafer using a confocal-microscope-based automatic defect characterization (ADC) system. The surface to be tested and a reference surface are scanned using a confocal microscope to obtain three-dimensional images of the test and reference surfaces. The test and reference images are converted into sets of geometric constructs, or “primitives,” that are used to approximate features of the images. Next, the sets of test and reference primitives are compared to determine whether the set of test primitives is different from the set of reference primitives. If such a difference a exists, then the difference data is used to generate defect parameters, which are then compared to a knowledge base of defect reference data. Based on this comparison, the ADC system characterizes the defect and estimates a degree of confidence in the characterization.

Abstract: An improved wafer surface inspection system is disclosed. In one embodiment, the object surface inspection system includes a translation stage that generates relative motion between an object viewing device such as an objective lens and the surface of the object being inspected. A translation stage controller controls the relative movement of the object surface and the object viewing device. The translation stage controller determines current coordinates for the object surface and the object viewing device, compares the current coordinates to target coordinates generated by a processor, and generates a trigger signal in response to a match between the current coordinates to the target coordinates. A camera receives an image through the object viewing device and captures the image in response to the trigger signal while the translation stage generates relative motion between the object surface and the object viewing device.

Abstract: Dilation and erosion operations are performed on imaged objects that are represented using a number of object pixels; the object pixels are a subset of a larger number of image pixels. A ring-shaped structuring element is specified by a radius and an origin. In the ring dilation operation, the boundary of the structuring element includes two concentric circles, one having a radius that is one pixel greater than the other so that the boundary is two-pixels wide. The origin of a copy of the structuring element is then overlaid onto each object pixel such that the boundaries of the copies intersect to form a dilated image feature. The image feature includes a feature boundary defined by the outermost portions of the boundaries of the overlapping copies of the structuring element. This feature boundary is identified and described using conventional chain-coding techniques. The dilation is then completed by filling an area defined within the feature boundary.

Abstract: A laser imaging system is used to analyze defects on semiconductor wafers that have been detected by patterned wafer defect detecting systems (wafer scanners). The laser imaging system replaces optical microscope review stations now utilized in the semiconductor fab environment to examine detected optical anomalies that may represent wafer defects. In addition to analyzing defects, the laser imaging system can perform a variety of microscopic inspection functions including defect detection and metrology. The laser imaging system uses confocal laser scanning microscopy techniques, and operates under class 1 cleanroom conditions and without exposure of the wafers to operator contamination or airflow.

Abstract: A method is described for characterizing defects on a test surface of a semiconductor wafer using a confocal-microscope-based automatic defect characterization (ADC) system. The surface to be tested and a reference surface are scanned using a confocal microscope to obtain three-dimensional images of the test and reference surfaces. The test and reference images are converted into sets of geometric constructs, or "primitives," that are used to approximate features of the images. Next, the sets of test and reference primitives are compared to determine whether the set of test primitives is different from the set of reference primitives. If such a difference exists, then the difference data is used to generate defect parameters, which are then compared to a knowledge base of defect reference data. Based on this comparison, the ADC system characterizes the defect and estimates a degree of confidence in the characterization.

Abstract: 10A method is described for detecting and characterizing defects on a test surface of a semiconductor wafer. A three-dimensional image of the test surface is aligned and compared with a three-dimensional image of a defect-free reference surface. Intensity differences between corresponding pixels in the two images that exceed a predefined threshold value are deemed defect pixels. According to the method, the pixels of the reference image are grouped according to their respective z values (elevation) to identify different physical layers of the reference surface. Because different surface layers can have different image properties, such as reflectance and image texture, the groups of pixels are analyzed separately to determine an optimal threshold value for each of the groups, and therefore for each layer of the reference surface.

Abstract: A method is described for optimizing intensity-comparison thresholds used to compare test and reference images for defect detection. Intensity differences between corresponding pixels in the two images that exceed a predefined threshold value are deemed defect pixels. According to the method, the pixels of the reference image are grouped according to their respective z values (elevation) to identify different physical layers of the reference surface. Because different surface layers can have different image properties, such as reflectance and image texture, the groups of pixels are analyzed separately to determine an optimal threshold value for each of the groups, and therefore for each layer of the reference surface.

Abstract: A microscope system moves a target in a first direction relative to a low power objective lens and, during the relative motion, generates and records values of an electronic focus signal that depends on the magnitude of light reflected by the target. Then, a host workstation calculates a first estimate of position ("focus position") of the target at which the microscope system is focused, by a median point method. In the median point method, the host workstation calculates the sum of the recorded values and determines the position along the range of motion at which half of this sum was exceeded, to be a first estimate of the focus position. From the intensity values of the first pass, optimal sensor gain is set for subsequent passes. Second and third estimates of the focus position can be calculated in a similar manner if necessary and the target is moved to the most recent estimate of the focus position.

Abstract: Disclosed is method of adjusting a microscope aperture to obtain the highest possible defect detection rate for a particular type of target. According to the method, an operator obtains an image of a calibration target and visually analyzes the image for defects. The operator then uses a defect detection process to analyze the image to obtain another set of defect information. This second set of defect information is compared with the visually obtained defect information to determine the accuracy of the defect detection performed by the defect detection process: a perfect match indicates 100% accurate defect detection. The operator then changes the aperture diameter and repeats the process to obtain a second set of defect information. This second set of defect information is, like the first set, compared with the visually obtained defect information. This process is repeated as many times as are necessary to determine which aperture diameter results in the highest defect detection rate.

Abstract: A microscope system moves a target in a first direction relative to a low power objective lens and, during the relative motion, generates and records values of an electronic focus signal that depends on the magnitude of light reflected by the target. Then, a host workstation calculates a first estimate of position ("focus position") of the target at which the microscope system is focused, by a median point method. In the median point method, the host workstation calculates the sum of the recorded values and determines the position along the range of motion at which half of this sum was exceeded, to be a first estimate of the focus position. From the intensity values of the first pass, optimal sensor gain is set for subsequent passes. Second and third estimates of the focus position can be calculated in a similar manner if necessary and the target is moved to the most recent estimate of the focus position.

Abstract: A method is described for obtaining an image of a target surface with a confocal microscope. The surface to be imaged is represented by a number of points on the surface, each of which has a unique location represented by X, Y, and Z Cartesian coordinates. The microscope selects a starting position for an objective lens of the microscope along a Z vector substantially normal to the surface. The objective lens has a preselected range of travel along the Z vector that is divided into a number of Z positions. Next, the objective lens is positioned and the surface scanned at each of the Z positions. The scan at each Z position provides signals, one for each point on the surface, representing the reflected intensity of laser light. Then, for each point on the surface, the microscope finds the Z coordinate of the point by determining which Z position resulted in the greatest return intensity of reflected laser light.

Abstract: A beam steering apparatus including a base, an input block slidably connected to the base, and an output block slidably connected to the base. An input mirror is connected to the input block and an output mirror is connected to the output block. The input mirror is positioned to receive a light beam and to steer the light beam to the output mirror, and the output mirror is positioned to redirect the light beam to a target. The terminal portion of the light beam is adjustable in a first orthogonal direction by sliding the input block relative to the base, and in a second orthogonal direction by sliding the output block relative to the base. The input mirror is rotatably connected to the input block and the output mirror is rotatably connected to the output block. An angle of incidence of the output beam relative to the target is adjustable in a first plane by rotating the input mirror relative to the input block, and is adjustable in a second plane by rotating the output mirror relative to the output block.

Abstract: A laser imaging system is used to analyze defects on semiconductor wafers that have been detected by patterned wafer defect detecting systems (wafer scanners). The laser imaging system replaces optical microscope review stations now utilized in the semiconductor fab environment to examine detected optical anomalies that may represent wafer defects. In addition to analyzing defects, the laser imaging system can perform a variety of microscopic inspection functions including defect detection and metrology. The laser imaging system uses confocal laser scanning microscopy techniques, and operates under class 1 cleanroom conditions and without exposure of the wafers to operator contamination or airflow.

Abstract: Surface image data representing a three-dimensional surface is extracted from a three-dimensional set of data representing characteristics of a volume in space (volumetric data) that encompasses the surface of an object, so that the surface image data can be used to display the surface. The volumetric data can comprise any data set in which comparisons between data can be used to ascertain points on a surface. In one embodiment of the invention, each of the pieces of volumetric data represents the intensity of light reflected in a particular direction from a point in space on or near the surface of an object. For example, the light intensity data can represent the intensity of laser light reflected back through an optical path of a laser imaging system after the laser light has been directed toward the surface of an object such as a semiconductor wafer.