Atomic layer deposition of titanium nitride

Transcription

1 Atomic layer deposition of titanium nitride Jue Yue,version4, 04/26/2015 Introduction Titanium nitride is a hard and metallic material which has found many applications, e.g.as a wear resistant coating[1], a diffusion barrier for copper in microelectronics[2-5], a candidate for capacitator electrode material in dynamic random access memory. Previous studies have reported thermal ALD of TiN with TDMAT, Plasma enhanced (PE) processes have been studied with TDMAT and H2, H2/N2 mixture and N2 plasmas as reactive gas, In this paper,we studied the growth kinetics, resistivity and purity of TiN films grown using ALD/PEALD with a metalorganic precursor and N2 or NH3. Experiment The experiments were performed in an ALD chamber.the ALD setup can accommodate up to six precursors and six reactive gases. Computer controlled pneumatic valves allow the flow of TDMAT (Sigma Aldrich, %) in Ar carrier gas into the chamber.the TDMAT precursor bottle is kept at 40 by a temperature controller. The tube from the precursor bottle to the

2 chamber is heated to 50 to prevent condensation of the precursor gas. The vacuum chamber walls were heated to 80. The deposition temperature is controlled by placing the samples on a resistive heating element. Based on calibration with a thermocouple, the temperature is set by adjusting the current through the heater. The system allows for both standard thermal ALD and PEALD, where the gases are preactivated in an inductively coupled plasma radio frequency (ICP RF) plasma source, which is separated from the growth chamber by a computer controlled gate valve. Samples with 100 nm thermally grown SiO2 and pieces of ptype Si(100) wafers were used as substrates for film deposition. Before deposition, the substrates were RCA cleaned. The silicon dioxide substrate was used for resistivity measurements, with a four point probe. The Si substrate was used for thickness measurements with X-ray reflectometry (XRR) using a Bruker D8 Advance Diffractometer. The chemical composition of the deposited films was determined by XPS, using a Thermo VG Scientific ESCALAB 220i-XL with a monochromatic Al K a X-ray source. The XPS was done ex-situ. The films were

3 sputtered in steps of 300 s with a beam of Ar ions to obtain a depth profile. The ions were accelerated to 2KV in an ion gun, forming a beam with a current of 220 na and a spot size of 2 mm 2 mm. Results and discussion The growth rate (growth per cycle, GPC) as a function of deposition temperature is shown in Fig. 1. as a function of deposition temperature. The GPC is higher for PEALD compared to thermal ALD for both N2 and NH3. Except for the PE process below 100, the GPC with ammonia is higher compared to processes with nitrogen.

4 Fig.1 Growth rate for films deposited using (a) nitrogen and (b) ammonia as reactive gas. The resistivity of the titanium nitride film as a function of plasma power and plasma exposure time is given in Fig. 2. The resistivity decreases strongly by an increase in plasma power between 0 and 200 W. A further increase of the plasma power only results in a marginal improvement of the conductivity. Longer plasma times further reduce the resistivity of the TiN films. The choice of plasma parameters does not significantly affect the growth rate. Fig.2. Resistivity of TiN films deposited with TDMAT and NH3 at 200 as a function of plasma power. Increasing power results in lower resistivity. Inset shows the effect of plasma time on the resistivity (plasma power 500 W).

5 Fig3 Resistivity as a function of thickness for films at 200 and 6 s plasma at 300 W. Fig.4 XPS depth profile of films. Table.1 Overview of deposition parameters, film stoichiometry and resistivity. *Conclusion *Acknowledgments *References [1] M. Hua, H.Y. Tam, H.Y. Ma, C.K. Mok, Wear 260 (2006) [2] K.-C. Park, K.-B. Kim, I.J.M.M. Raaijmakers, K. Ngan, J. Appl. Phys. 80 (1996) [3] J.-S. Min, H.-S. Park, S.-W. Kang, Appl. Phys. Lett. 75 (1999) [4] J.W. Elam, M. Schuisky, J.D. Ferguson, S.M. George, Thin Solid Films 436 (2003) 145.

6 [5] J.Y. Kim, S. Seo, D.Y. Kim, H. Jeon, Y. Kim, J. Vac. Sci. Technol. A 22 (2004) 8.