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Nanometer Drilling with Nanometer Precision Using Near-Field Optics

IP.com Disclosure Number: IPCOM000031846D
Publication Date: 2004-Oct-14
Document File: 2 page(s) / 336K

Publishing Venue

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Abstract

A new laser-machining technology is being developed to fabricate sub-wavelength, or nanometer scale, features in ambient condition with nanometer precision. We use NSOM (near-field scanning optical microscope) delivered femto-second pulses to machine targeted substrate surface. The ablation laser has a pulse width of 150 femto-second and wavelength of 387-nm. The distance between fiber probe and the substrate is controlled to be much less than wavelength of 387 nm.

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Nanometer Drilling with Nanometer Precision Using Near-Field Optics

   1. Introduction: A new laser-machining technology is being developed to fabricate sub-wavelength, or nanometer scale, features in ambient condition with nanometer precision. The current targeted device is a one-dimensional photonic crystal that can be used as optical signal delay generators or add/drop filters for next generation THz communication market.

The ability of monitoring surface topology of substrate in real time enables us to accomplish the in-situ surface processing. In other words, we are able to do nanometer scale repair/adjustment on a preformed nanometer structure, which is difficult or impossible by etching technique. It has broad potential in many fabrication processes.

Since the technology does not require vacuum equipment, it is a superior solution in field applications when the device only can be repaired or adjusted away from the factory. Because no harsh chemical process is needed, clean up of chemical waste is minimal. Therefore, this technology is considered environment-friendly or "green" in the manufacturing settings.

ablation

Figure 1. NSOM drilling system.

We use NSOM (near-field scanning optical microscope) delivered femto-second pulses to machine targeted substrate surface. The ablation laser has a pulse width of 150 femto-second and wavelength of 387-nm. The distance between fiber probe and the substrate is controlled to be much less than wavelength of 387 nm. The produced feature on Silicon surface is at least 200- nm deep with hole diameter around 200-nm.

   2. Technology Description: There are two major limitations using ultra-fast laser pulses to drill nanometer scale holes in free space.

First of all, the fundamental limitation of diffraction restricts the spot size to larger than half of the wavelength in free space optics.

Secondly, it is difficult to precisely direct the beam onto target. The same diffraction limit mentioned above also limits how small an optical microscope can resolve a feature. It is impossible to do in-situ nanometer machining using traditional optical microscope. A metrology method that can be applied in air and coexist with laser drilling technology is necessary for precision machining on pre-formed nanometer structures.

A technique is being developed to take advantage of near- field optics and use fiber delivery method. Near-field optics technique requires extremely short distance (shorter than wavelength) between a sub-wavelength optical aperture and substrate surface. Under such condition, the diffraction limit is not longer applicable and the laser beam size can be smaller than half of the wavelength. In fact, Ohtsu et al had shown possible resolution of λ/81.

In practice, we use optical fibers with nanometer tapered- probe made on one end to deliver the laser beam as shown in Figure 1. The laser pulses are coupled into the free end of a multimode optical fiber that a nanometer-size NSOM probe was fab...