Organic monolayers as resist layers for Cu deposition on Si (111) surfaces

Abstract

Organic covalently attached monolayers (CAMs) were found to be useful as resist layers for patterning Si surfaces. In the present work, we investigate selective plating of Cu on n-type Si (111) surfaces chemically modified with different organic monolayers and subsequently directly patterned by an electron-beam (e-beam) and by AFM induced scratching. The organic molecules (1-undecylenic acid, 1-decene and 1-octadecene) were covalently attached to a hydrogen-terminated Si surface. The use of such monolayers as masks for copper deposition by electroinduced and immersion plating on Si surfaces was investigated. A masking effect can be clearly observed, the efficiency of which depends on the type of molecule. The effect of e-beam irradiation on modification of CAMs and selective deposition of Cu in e-beam treated locations was shown. For this, the monolayers were locally irradiated using a scanning electron microscope (SEM) equipped with a lithographic tool and Cu deposition was performed under external applied potential. Selectivity of deposition strongly depends on applied e-beam dose. The results show that e-beam-modified organic monolayer can be used as a positive tone resist if treated with medium e-beam doses and as a negative tone resist if treated with high doses for both: copper immersion plating and electrodeposition. Also it was demonstrated that CAMs can be successfully used as negative tone resists for AFM induced scratching. By optimizing the electroless deposition parameters, homogeneous deposition with a complete selectivity can be achieved, leading to a high lateral resolution of the Cu patterns.