MONOLAYER-MEDIATED DEPOSITION OF TANTALUM(V) OXIDE THIN-FILM STRUCTURES FROM SOLUTION PRECURSORS

Integration of oxide thin films with semiconductor substrates is a cri tical technology for a variety of microelectronic memory and circuit a pplications. Patterned oxide thin film devices are typically formed by uniform deposition followed by postdeposition ion-beam or chemical et ching in a controlled environment, This paper reports details of an am bient atmosphere technique which allows selective deposition of dielec tric oxide thin layers without postdeposition etching. In this method, substrate surfaces are selectively functionalized with hydrophobic se lf-assembled monolayers of octadecyltrichlorosilane by microcontact pr inting (mu-CP). Sol-gel deposition of ceramic oxides on these function alized substrates, followed by mild, nonabrasive polishing, yields hig h-quality, patterned oxide thin layers only on the unfunctionalized re gions. A variety of micrometer-scale dielectric oxide devices have bee n fabricated by this process, with lateral resolutions as fine as 4 mu m. In this paper, we describe the solution chemistry, evolution of mi crostructure, and electrical properties of Ta2O5 thin films, as well a s the stress-related mechanism which enables selective de-adhesion and resultant patterning, Selectively deposited, 80-120 nm thick Ta2O5 th in film capacitors were crystallized on platinized silicon at 700-800 degrees C, and had dielectric constants of 18-25 depending upon the pr ocessing conditions, with 1 V leakage current densities as low as 2 x 10(-8) A/cm(2). The ability to selectively deposit Ta2O5 and other ele ctrical ceramics (such as LiNbO3 and PbTiO3) on a variety of technolog ically important substrate materials suggests broad potential for inte grated circuit and hybrid microelectronics applications.