DIRECT DEPOSITION OF PATTERNED COPPER-FILMS ON TEFLON

Current subtractive methods yielding patterned Cu features on PTFE substrates rely on wet Cu etching processes. We have developed three variations of a new dry, additive patterning process. The mechanisms for patterning include Mg Kalpha X-ray-induced cross-linking, e-beam-induced cross-linking, or laser patterning. The X-ray and e-beam patterning processes rely on irradiation followed by selective etching of the non-irradiated areas. The laser patterning begins by chemically etching PTFE which leaves a rough surface with good adhesion characteristics. An argon-ion laser beam is then used to selectively remove the etched layer, revealing the underlying surface which has physical properties closely resembling unmodified Teflon. Typical laser patterning conditions are scan rates of 0.005-5.5 mm/s, incident powers of 40-380 mW at 514 nm, and base pressures of 10(-2) Torr and at atmospheric pressure in air. In all cases, CVD from (beta-diketonate)CuL compounds is used to deposit copper only on the etched regions of the sample, leaving the irradiated regions copper-free. The advantages of this procedure are: (1) subtractive Cu wet etching of copper is avoided, so no masking techniques are necessary and no liquid waste is generated; (2) ten-micron-sized features can be produced; (3) excellent adhesion is obtained.