KLA Tencor : Patent Issued for Wafer Edge Inspection with Trajectory following Edge Profile (USPTO 9719943)
Patent number 9719943 is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "Wafers used in semiconductor manufacturing are typically inspected for defects such as, for example, surface imperfections, particles, or irregularities in thickness. These defects may impair operation of a semiconductor device. As each wafer processing step is expensive, manufacturers usually inspect the wafer between processing steps to determine whether the wafer should be reworked or scrapped.
"Edges of a wafer can pose challenges during semiconductor manufacturing or inspection. Semiconductor manufacturers try to include as many semiconductor devices on a wafer as possible. Thus, inspection of the wafer edge may be needed to determine whether the edge can form usable devices. Devices near the wafer edge also may be inspected to determine yield or process control problems. However, wafer edges may be rounded or have irregular shapes. These rounded or irregular shaped edges can make inspection difficult.
"Use of a semicircular scan of the wafer edge may result in images that are out of focus or unclear because the wafer edge may have an irregular, rather than perfectly semicircular, shape. This results in the optical head used for imaging being off-normal or defocused with respect to the edge profile over portions of the wafer surface or edge. For example, phase imaging over an irregular surface with a semicircular scan can result in a signal that is degraded by light and dark bands caused by variations in the angle of incidence of the imaging beam or defocus. Thus, sensitivity to defects is degraded.
"Therefore, what is needed is an improved wafer edge inspection system and technique."
In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventor's summary information for this patent: "In a first embodiment, an inspection system is provided. The inspection system includes an optical head, a support system, and a controller. The support system is configured to provide movement to the optical head with three degrees of freedom around a circumferential edge of the wafer. The controller is in electrical communication with the support system and is programmed to control movement of the optical head using the support system such that the optical head maintains a constant angle of incidence relative to a wafer surface while imaging the circumferential edge of the wafer.
"An edge profiler may be operatively connected to the controller. The edge profiler may be a shadowgram imaging system that includes a collimated light source and a camera. The camera is configured to receive collimated light from the collimated light source and image a shadow of the circumferential edge of the wafer.
"The optical head may include an imaging system. The optical head may further include an edge profiler.
"The controller may be configured to move the optical head from a first surface of the wafer to a second surface of a wafer.
"The support system may be configured to move the optical head in a direction perpendicular to the wafer surface. The support system may be configured to move the optical head in a direction radially with respect to the wafer. The support system may be configured to rotate the optical head about an axis which is tangential with respect to the circumferential edge.
"The inspection system may include a platen configured to support the wafer. The platen may be configured to rotate the wafer about a central axis of the wafer.
"In a second embodiment, a method is provided. The method includes collecting and analyzing a shadowgram edge profile image of a wafer to determine an edge profile, determining a trajectory of an optical head using the edge profile, moving the optical head along the trajectory, and generating an image of the circumferential edge of the wafer. The shadowgram edge profile image is a shadow of a circumferential edge of the wafer generated using collimated light. A constant angle of incidence is maintained relative to a wafer surface while imaging a circumferential edge of the wafer using the trajectory. Images may be generated as a sum and difference of two individually orthogonally-polarized reflected incident beams. The imaging may be between a first surface of the wafer to an opposite second surface of the wafer.
"In a third embodiment, a system is provided. The system includes a processor, a storage device in electronic communication with the processor, and a communication port in electronic communication with the processor. The processor is programmed to receive a shadowgram edge profile of a wafer, determine a trajectory of an optical head using the edge profile, and send instructions to move the optical head along the trajectory. The shadowgram edge profile image is a shadow of a circumferential edge of the wafer generated using collimated light. A constant angle of incidence is maintained relative to a wafer surface while imaging a circumferential edge of the wafer using the trajectory. The imaging may be between a first surface of the wafer to an opposite second surface of the wafer."
URL and more information on this patent, see: Horn, Paul. Wafer Edge Inspection with Trajectory following Edge Profile.
Keywords for this news article include: Electronics, Technology Companies,
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