Sunday, June 18, 2006

US Patent 7060977 - Dip Pen Nanolithography Calibration

The development of the scanning tunneling microscope, and later the atomic force microscope, in the early 1980's was a crucial development for nanotechnology since these devices allow for detection at the atomic level by using ultrasharp tips positioned by sensitive optical and piezoelectric feedback mechanisms. Together with other new microscopes such as near-field optical microscopes and magnetic force microscopes, these devices introduced a paradigm shift in microscopy by using proximal, or near contact, inspection techniques rather than the far field optical or electron beam inspection methods used previously. Collectively referred to as scanning probe microscopes these proximal probes are now beginning to revolutionize manufacture techniques, as they previously revolutionized microscopy in the '80s and '90s, by providing etching, curing, coating, or other fabrication process steps. Nanoink, the owner of this patent, is helping to lead the way in this innovation by using the tips as a nanoscale coating tool in applications such as mask repair and circuit fabrication. This patent is specific to a calibration method. Claim 1 reads:

1. A method for calibration of a scanning probe nanolithographic process, the method comprising: (i) fabricating a nanoscale test pattern by scanning probe lithography, (ii) measuring a parameter of the test pattern, (iii) calculating a calibration coefficient from the measured parameter, (iv) using the calculated calibration coefficient for forming a nanolithographic pattern by scanning probe lithography.

While I admire Nanoink's efforts and think (based on some of their other patents) that this company is making a valuable contribution to nanotechnology, I think that the attorney prosecuting this application may have been a bit overambitious and the Examiner a little too lenient in allowing this claim. Test pattern calibration is common in microlithography and extention to nanolithography tools such as scanning probes, nanoimprint stamps, etc. would have been obvious to a person of ordinary skill in the art to provide the advantage of increased accuracy of fabrication at nanometer dimensions. However, regardless of arguments about obviousness, the patent is anticipated by US Patent 6337479.

See, for example, column 2, lines 46-67 of the '479 patent.