Patent Application
20080024772
The embodiments of the invention address the problems associated with defect detection and analysis during burnishing without removal of the media from the burnishing (particle removal) tool. These problems were solved by integration of the particle removal tool and the particle detection tool as one merged tool comprising one disc mounting mechanism, plus advanced image processing algorithm. The integrated unit comprises a particle detection tool and a particle removal (burnishing) tool combined as one merged tool comprising a disc mounting mechanism having a mount for mounting the disc for both particle detection and particle removal, wherein the particle detection tool is adapted to distinguish between a void in the disc and a particle on the disc.
The burnishing tool of the embodiments of the invention comprises a burnishing head that sweeps over the surface of the media and removes particles and asperities, for example. Burnishing is achieved, at least in part, by arrangements and methods which provide for the sweeping of the burnishing head across the disc at a skewed angle. A skewing of the arm to which the burnishing head is attached causes the burnishing head to be skewed relative to a disc diameter perpendicular to the sweeping direction, i.e., relative to a surface of the disc (media). This achieves a more complete wiping of loose particles and surface contamination, a more aggressive wedge cutting of asperities and surface conditioning, as well as more efficient particle deflection than conventional non-skewed head burnish arrangements. Employing a burnishing head with a continuous rail edge provides for a wedge cutting that is more, efficient than non-skewed arrangements.
In a burnishing operation, an arm having a burnishing head attached to it at one end is translated in a sweeping direction over the media which is rotated while the arm is translated in such that the head sweeps over the media. The head could be skewed at an angle with respect the surface of the media or it could parallel to the surface of the media. The skewing angle could be between about 5° to about 30° in certain embodiments, between about 10° to about 25° in certain other embodiments and could be between about 15° to about 20° in especially preferred embodiments. The skewed head burnishing could create a more complete wiping action that catches loose particles and surface contaminations.
Another improvement provided by the skewed-head burnishing arrangement is the very aggressive asperity cutting and surface conditioning. For example, the arm could have slider/rail edges that form effective wedges. The aggressiveness of the asperity cutting could be further enhanced with the lower fly height that could be achieved because of the skewing of the burnishing head as there is a less efficient compression of incoming air with a skewed head versus a non-skewed head.
Another improvement produced by the skewed burnishing head arrangement is the deflection action created by the skewed slider/rails. Deflection action prevents loose particles from being embedded into the disc surface. Instead, the particles deflect off the skewed rails. The axes of the rails could be skewed at the skewing angle of about 15° to about 20° with respect to the surface of the disc
The disc is mounted on a mount during burnishing and defect detection/analysis. The mount is rotated by a disc rotation mechanism. The disc rotation mechanism controls the speed of rotation on the disc, which may have an effect on the burnishing with the skewed angle arrangement of the present invention. The disc could be rotated at between about 500 ips to about 1500 ips during the sweeping. In certain embodiments of the invention, the disc could be rotated at about 1100 ips during burnishing and defect detection.
The integrated particle removal and defect detection/analysis unit of the embodiments of this invention isable to perform particle removal and surface defect detection and intermittent disc handling between burnishing and particle removal is eliminated. Also, the embodiments of the invention provide for the distinction between loose particles and non-removable surface defects (mainly voids) in the following way, for example. Perform two defect detection runs before and after the particle removal process and map the defect topography of the media surface before and after the particle removal process. Compare the two defect maps and identify defects that show up on both maps at the same locations on the media surface. These defects are most likely non-removable, void type surface defects. If a disc shows only non-removable defects after the particle removal process, the disc could be accepted for the replication procedure.
An integrated unit having a particle removal tool and an in-situ disc inspection system (“in-situ” meaning that the disc is mounted on the same mount, i.e., a spindle platform, during both the particle removal and in-situ disc inspection) preferably has the following performance specifications:
Additional system specification of the embodiments of the invention could include:
Design of the Integrated Particle Removal and Defect Detection/Analysis Tool
An example of an integrated unit having a merged tool is shown in
Design of the Optics Module
The defect detection and analysis unit comprises an optics module and a software algorithm module. An embodiment of the optics module. The optics module comprises an incident laser beam that reflects off the surface of the media and the reflected/scattered beam from defects is detected by a detector such as a camera such as a charge coupled device (CCD) camera, a single channel detector or a low-density detector such as a photodiode, a photomultiplier tube, or an avalanche photodiode. The detected signal is then analyzed by the computer software so as to create a defect map of the surface of the media. The optics module can detect particles to 0.1 micron or larger, preferably, 0.5 micron or larger, and most preferably 1 micron or larger, though detection limit is determined mainly by hardware, and further performance enhancement is achievable through the improvement of: (a) incident laser intensity, wavelength, polarization, etc.; (b) numerical aperture (light collecting capability) of the optics; (c) spectral response of the imager (CCD); and reduced noise (electronic, optical).
System Integrator (Software Algorithm) for the Optics Module
The optics module alone can not differentiate fixed media defects from loose particles. It is known from earlier work that fixed defects such as pits, target spits, blisters, handling damage, etc. do not damage the stamper. Rejecting discs having fixed defects leads to over-rejection of the media. To overcome this problem, the embodiments of this invention include a system integrator having software algorithm connected to the optics module. The system integrator compares the optical defect maps before and after particle removal process to differentiate pits from particles. The fixed defects will not be moved by the particle removal process and will show up as the matched defects in the defect maps before and after particle removal while the loose particles will be moved by the head and will show up as the un-matched defects. The system integrator ignores the fixed defects and uses the un-matched defects as a criteria for loose particle detection. While the above examples generally describe defect detection and mapping pre- and post a single burnishing step, it is possible to have multiple burnishing steps with pre- and post burnishing steps for each or some of the burnishing steps.
Method of Manufacturing the Integrated Particle Removal and Defect Detection/Analysis Tool
The manufacturing of the integrated tool would include assembling controller/computer controlling the parameters, motion, sequences, data operation and processing of the particle removal device, the optical inspection system and the disc spindle. This includes, but is not limited to, monitoring safety sensors, communicating to external devices and adhering to SEMI equipment manufacturing safety standards and operations and NFPA standards.
SEMI and other equipment guidelines are described below and incorporated herein by reference.
The above description is presented to enable a person skilled in the art to make and invention, and is provided in the context of a particular application and its requirements. Various modifications to the preferred embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Thus, this invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.
This application discloses several numerical range limitations that support any range within the disclosed numerical ranges even though a precise range limitation is not stated verbatim in the specification because this invention can be practiced throughout the disclosed numerical ranges. Finally, the entire disclosure of the patents and publications referred in this application are hereby incorporated herein in entirety by reference.
This application is related to U.S. Pat. Nos. 7,028,743, 6,987,627, 6,985,314 and 6,979,524, which are incorporated herein by reference.
