Abstract: Methods and device for user terminal based fast handoff are provided. User terminal builds a neighbor group list in which possible neighbor access points (APs) are divided into one or more groups. When a handoff needs to be prepared, the user terminal performs intermittently multiple pre-break probing subphases according to the neighbor group list while not breaking connection with a current serving AP. In each PBP subphase, signal qualities of neighbor APs in one group are probed in a manner of active probing. The user terminal selectively performs handoff according to the probed signal qualities of the neighbor APs. The user terminal may build the neighbor group list based on information of neighbor APs derived through overlapped channel scanning or information of neighbor APs received from the serving AP. The neighbor APs belonging to the same group work on the same channel and in each PBP subphase, a group of neighbor APs may be probed by using unicast probe request.

Abstract: Methods, devices and system for access point facilitated fast handoff are provided. Each access point (AP) in a wireless local area network is provided with a primary interface and a secondary interface wherein the primary interface performs normal communication with user terminals and broadcasts standard beacon frames on its working channel, and the secondary interface broadcasts extended beacon frames on working channels of neighbor APs sequentially. The extended beacon frame includes at least information of BSSID, SSID, working channel and the like of the primary interface of the corresponding AP. The user terminal may receive the standard beacons from the serving AP it is communicating with and the extended beacons from the neighbor APs, and according to the two kinds of beacons, the terminal may calculate the signal quality with the primary interface of the serving AP and the signal qualities with the neighbor APs at the current position.

Abstract: A method for inspecting objects such as semiconductor wafers. A staging platform and an optical platform are arranged so that the object may be staged and its surface scanned by optical equipment situated on the optical platform. During the scanning process, the surface is illuminated with light of a plurality of wavelengths, each strobed at a predetermined rate so that multiple images may be collected using time and frequency multiplexing. The multiple images are stored in a database for analysis, which includes processing selected ones of the multiple images according to one or more algorithms. The defect-detection algorithms used for each object are determined by referenced to a predetermined or calculated defect detection protocol, then a defect mask is created for each pixel in the images that is suspected to be defective. The defect mask is then compared to threshold parameters to determine which if any of the suspected defects should be reported.

Abstract: A system and method for performing optical inspection of structures on the surface of a semiconductor wafer. The wafer surface is illuminated with a polychromatic light source. A multiple-charged couple-device (CCD) camera is positioned to capture light diffracted by the structures on the wafer surface at the first order of diffraction. The captured light is then separated into a plurality of component wavelengths which are directed onto the CCDs. A digital filter creates a plurality of digitized diffractive images of the wafer surface at different component wavelengths. The diffractive images may be integrated and analyzed to detect defects in the structures, or may be, analyzed individually. An image at a particular wavelength may be selected and analyzed by using the known grating pitch of the structures to calculate the wavelength.

Abstract: A method of collating and using captured semiconductor-wafer image data in an automated defect analysis. The method includes the steps of receiving image data and, if necessary, converting it to a digital format. Once the data is in pixel-by-pixel form, each pixel is assigned a slope value derived from the direction of the structure edge, if any, on which it lies. The pixel-slope data is then evaluated to determine whether a photo-resist anomaly is present. The method may also include evaluated an average pixel slope value for each inspected wafer. Dependant claims further define the invention to claim an inspection system for employing the method.

Abstract: A system and method for performing optical inspection of structures on the surface of a semiconductor wafer. The wafer surface is illuminated with a polychromatic light source. A multiple-charged couple-device (CCD) camera is positioned to capture light diffracted by the structures on the wafer surface at the first order of diffraction. The captured light is then separated into a plurality of component wavelengths which are directed onto the CCDs. A digital filter creates a plurality of digitized diffractive images of the wafer surface at different component wavelengths. The diffractive images may be integrated and analyzed to detect defects in the structures, or may be analyzed individually. An image at a particular wavelength may be selected and analyzed by using the known grating pitch of the structures to calculate the wavelength.