H. M. Phillips

Sub‐100 nm lines produced by direct laser ablation in polyimide

Periodic line structures with a period of 167 nm and linewidths varying from 35 to 100 nm have been produced on polyimide by direct ablation with a KrF laser using an interferometric technique. Since ablation is a nonlinear process, the resolution can exceed that expected from the wavelength and numerical aperture of the system and the linewidth can be controlled by varying the laser fluence. This externally generated period of 167 nm prevents the spontaneous growth of periodic surface structures due to radiation remnants.

Direct laser ablation of sub-100 nm line structures into polyimide

Periodic line structures with a period of 167 nm and linewidths varying from 30 to 100 nm have been produced in polyimide by direct ablation with a KrF laser using an interferometric technique. The characteristics of this interferometer as it applies to the ablation of these line structures, including linewidth and alignment sensitivity, are analyzed. The ability to control the linewidth by varying the average incident fluence is described theoretically and demonstrated experimentally. This externally generated period of 167 nm also prevents the spontaneous growth of laser induced periodic surface structures (LIPSS).

Femtosecond excimer-laser-induced structure formation on polymers

Structure formation upon 500 fs 248 nm KrF-laser irradiation of PolyEthylene Terephthalate (PET) and PolyImide (PI) has been investigated. The results obtained with fs pulses have been compared to those with ns pulses.

Excimer-laser-produced nanostructures in polymers

The ability of excimer lasers to modify the surface morphology and the electrical conductivity of polymers with spatial resolution on a nanometer scale has been demonstrated. Using holographic techniques with a KrF excimer laser, periodic line structures with periods ranging from 166 to 950 nm have been ablated into polyimide (Kapton) and polybenzimidazole (PBI). The nonlinear nature of laser ablation allows linewidths as small as 30 nm to be obtained, exceeding the resolution expected from linear optics. These experiments establish a new spatial resolution limit for laser ablation and illustrate the dependence of resolution on material properties. This technique has been combined with the ability to modify the electrical conductivity of polymers to produce an array of permanently electrically conducting wires in polyimide with a 0.5-μm width and a 0.9-μm period. The electrical conductivity of these submicrometer wires was greater than 1 Ω -1 cm -1 .

Excimer-laser-induced electric conductivity in thin-film C60

The electrical conductivity of thin-film C60 has been changed by more than seven orders of magnitude with KrF (248nm) excimer-laser irradiation. Specific conductivities of 1 Ω−1 · cm−1 have been obtained. The onset of conductivity is consistent with a laser-induced metal-insulator phase transition. The threshold for KrF-laser ablation of C60 has been determined to be 20±2 mJ/cm2. This laser-induced process generates an all-carbon semiconductor-metallic junction which may have important technological applications.

Characterization of plasmas from a pulsed jet discharge for applications VUV spectroscopy and micromechanics

Plasmas from a pulsed jet discharge have been characterized with respect to gas species and nozzle design. Spectral lines from the gas used in the pulsed nozzle are apparent in the visible region. The vacuum ultraviolet spectrum, particularly for heavier gases, is dominated by emission from species sputtered from the nozzle. The production of highly ionized and excited states from materials created by the sputtering of the nozzle has possible applications in VUV (vacuum ultraviolet) spectroscopy. Operating the pulsed jet discharge at a 50-Hz repetition rate with NF/sub 3/ to produce excited fluorine ions allowed etch rates in excess of 10 mu m/min to be achieved in silicon; this may have applications to micromechanics. >

Excimer Laser Induced Mechanical and Electrical Nanostructures in Polymers

Periodic line structures with periods ranging from 166 nm to 950 nm have been produced in polyimide by direct ablation with a KrF (248 nm) laser using holographic techniques. Taking advantage of the large nonlinearity in the laser ablation process, linewidths ranging from 30 nm to several hundred nanometers could be obtained. These techniques were combined with the ability to induce electrical conductivity in polyimide to produce an array of 500 nm wide electrically conducting wires. The conductivity of these wires was similar to that found in macroscopic regions of laser induced conductivity.

Modification of electrical conductivity and surface structure in polymers using ultraviolet laser radiation

Abstract Irradiation of most polymers with ultraviolet lasers results in permanent changes in their surface morphology and electrical conductivity. Using KrF (248 nm) excimer laser radiation, the electrical conductivity of polyimide (Kapton) and polybenzimidazole (PBI) has been increased by as much as sixteen orders of magnitude, obtaining values on the order of 10 Ω -1 cm -1 . This laser-induced conductivity exhibits a threshold both in fluence and in the number of laser shots and has a saturation conductivity which is slightly fluence dependent. Periodic line structures with a period of 167 nm and linewidths varying from 30 to 100 nm have been produced in polyimide by direct ablation with a KrF laser using an interferometric technique. This experiment establishes the optics- and materials-dependent spatial resolution limits for laser ablation and for the modification of the electrical conductivity in polymers. An array of sub-micron wires has been produced in polyimide, demonstrating the ability to modify electrical conductivity in polymers with high spatial resolution.