Area Selective Atomic Layer Deposition by Soft Lithography
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0917-E11-05
Area Selective Atomic Layer Deposition by Soft Lithography Rong Chen1, David W. Porter2, Hyoungsub Kim3,4, Paul C. McIntyre3, and Stacey F. Bent2 1 Dept. of Chemistry, Stanford University, Stanford, CA, 94305 2 Dept. of Chemical Engineering, Stanford University, Stanford, CA, 94305 3 Dept. of Materials Science and Engineering, Stanford University, Stanford, CA, 94305 4 Sungkyunkwan University, Jangan-Ku, Suwon, 440-746, Korea, Republic of
ABSTRACT Area selective HfO2 thin film growth through atomic layer deposition (ALD) has been achieved on octadecyltrichlorosilane (ODTS) patterned Si substrates. Patterned hydrophobic self-assembled monolayers (SAMs) were first transferred to Si substrates by micro-contact printing. Using hafnium-tetrachloride or tetrakis(dimethylamido) hafnium(IV) and water as ALD precursors, amorphous HfO2 layers were then grown selectively on the SAM-free regions of the surface where native hydroxyl groups nucleate growth from the vapor phase. The HfO2 pattern was readily observed through scanning electron microscopy and scanning Auger imaging, demonstrating that soft lithography is a simple and promising method to achieve area selective ALD. To evaluate the selectivity, the resolution of the soft lithography based method was compared with that of area selective ALD of HfO2 by selective surface modification of patterned silicon oxide obtained using long-time SAM exposure. It was found that the selective surface modification showed much higher spatial resolution and selectivity, an observation consistent with previous studies indicating that highly ordered and densely packed ODTS films were important to achieve complete deactivation. INTRODUCTION As the lateral dimensions of metal-oxide-semiconductor field-effect transistors (MOSFETs) continue decreasing and higher switching speeds are required, the thickness of the SiO2 gate dielectrics must be substantially decreased to a few atomic layers. However, the leakage current caused by direct electron tunneling from the gate to the channel increases exponentially with decreasing dielectric thickness [1,2]. In order to overcome this difficulty, gate dielectrics with permittivities greater than that of SiO2, such as HfO2 [3], are required. High-κ dielectric layers allow deposition of thicker layers while retaining the same effective oxide thickness. Among many possible deposition techniques for ultra-thin high-κ dielectric films, atomic layer deposition (ALD) is very promising method. It is a powerful thin film growth technique that employs a sequence of self-limiting surface reaction steps to afford sub-nanometer control of the growth process. The self-limiting adsorption reactions ensure the precise control of film thickness, conformality, and uniformity over large area. Typically, the process permits nanoscale control in the vertical direction. To extend the method to three dimensional control of materials, we have been investigating area-selective ALD techniques which will enable micro-, and ultimately nano-scale definition of the late
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