Dennis Hausmann

Highly conformal atomic layer deposition of tantalum oxide using alkylamide precursors

Abstract Atomic layer deposition of highly conformal films of tantalum oxide were studied using tantalum alkylamide precursors and water as the oxygen source. These films also exhibited a very high degree of conformality: 100% step coverage on vias with aspect ratios greater than 35. As deposited, the films were free of detectable impurities with the expected (2.5–1) oxygen to metal ratio and were smooth and amorphous. The films were completely uniform in thickness and composition over the length of the reactor used for depositions. Films were deposited at substrate temperatures from 50 to 350 °C from precursors that were vaporized at temperatures from 50 to 120 °C. As deposited, the films showed a dielectric constant of 28 and breakdown field consistently greater than 4.5 MV/cm.

ALTERNATING LAYER CHEMICAL VAPOR DEPOSITION (ALD) OF METAL SILICATES AND OXIDES FOR GATE INSULATORS

A new process was developed for deposition of the silicates and oxides of metals such as zirconium and hafnium at low substrate temperatures (100-300 o C). The silicon and oxygen source is tris(tert-butoxy)silanol, ( t BuO)3SiOH, and the metal precursors are metal amides. A typical reaction is ZrL4 +2 ( t BuO)3SiOH ZrSi2O6 +4 HL +6 H 2C=C(CH3)2 +2 H 2O in which the ligand L is ethylmethylamide, -NEtMe. The precursor vapors were alternately pulsed into a heated reactor, yielding about 0.3 to 0.7 nm of metal silicate film for each cycle. Replacing the silanol pulses with water pulses yields pure metal oxides with a thickness of about 0.1 to 0.15 nm per cycle. The silicon content of the films can be adjusted to any desired value by replacing some of the silanol pulses by water pulses. This new process has a number of advantages over previous methods for depositing metal silicates. Uniformity of thickness and stoichiometry are readily achieved. The deposition atmosphere is non-oxidizing, so that formation of low-k interfacial oxides between the deposited layer and a silicon substrate is minimized. The new halogen-free precursors avoid halogen contamination of films and corrosion of deposition systems. This process is a promising method for forming the next generation of ultra-thin high-k gate dielectrics in silicon-based microelectronics.

Challenges in atomic layer deposition of carbon-containing silicon-based dielectrics

The authors have designed experiments to test three different approaches for the incorporation of carbon atoms into amorphous SiNx or SiO2 films grown using atomic layer deposition (ALD). In each approach, the surface reactions of the precursors were monitored in situ using attenuated total reflection Fourier transform infrared spectroscopy. In the first approach, for depositing carbon-containing SiNx films using ALD, carbon was introduced into the process through a silicon precursor, SiCl2(CH3)2, followed by NH3 plasma exposure. While our infrared data show that SiCl2(CH3)2 reacts with an –NHx (x = 1, 2) terminated surface created after NH3 plasma exposure, –CH3 groups are eliminated in the precursor adsorption step leading to no significant carbon in the films. In the second approach, the authors hypothesized a three-step ALD process, which would involve Si-, C-, and N-containing precursors, and tested the reactivity of two carbon-containing precursors, CH3I and Al(CH3)3, with H- and Cl-terminated silic...