A monolayer-based lift-off process for patterning chemical vapor deposition copper thin films

We describe a non-lithographic monolayer based patterning process for depositing copper thin film microstructures by chemical vapor deposition (CVD). The technique combines the microcontact printing of octadecyltrichlorosilane (OTS) monolayers, nonselective copper CVD, and mild (abrasive-free) mechanical polishing to fabricate thin film microstructures on both planar and nonplanar substrates. This technique has been used successfully to deposit copper features with sizes ranging from 5 to 250 μm on variety of technologically important substrates including indium tin oxide (ITO), titanium nitride (TiN), thermal and plasma grown SiO₂, Al₂O₃, and glass. Patterning is effected via adhesive failure in regions modified by microcontact printing (μCP); nucleation and growth are inhibited in these regions and the copper grains which eventually form on top of the OTS monolayer remain loosely adherent and, thus, are easily removed by mechanical means. The versatility and simplicity of the μCP process as a method for surface modification combined with chemical/physical routes of thin film deposition and patterning suggest a new, defecttolerant method for fabricating thin film features with micrometer to centimeter dimensions with potential advantages over conventional subtractive patterning processes involving photolithography and chemical etching. Possible applications in the manufacturing of multichip modules (MCM-D) and more generally in microelectronic packaging and liquid crystal display (LCD) metalization are described.