AVS 56th International Symposium & Exhibition
    Thin Film Tuesday Sessions
       Session TF2-TuA

Paper TF2-TuA10
In-situ Half-Cycle XPS Investigation of La-aluminate Formation during Atomic Layer Deposition

Tuesday, November 10, 2009, 5:00 pm, Room B4

Session: ALD/CVD: Oxides and Barriers
Presenter: T.J. Park, University of Texas at Dallas
Authors: T.J. Park, University of Texas at Dallas
H.C. Kim, University of Texas at Dallas
M. Milojevic, University of Texas at Dallas
B. Lee, University of Texas at Dallas
R.M. Wallace, University of Texas at Dallas
J. Kim, University of Texas at Dallas
X. Liu, Dow Electronic Materials
M. Rousseau, Dow Electronic Materials
J.H. Li, Dow Electronic Materials
H. Li, Dow Electronic Materials
D. Shenai, Dow Electronic Materials
J. Suydam, Dow Electronic Materials
Correspondent: Click to Email
Lanthanum based oxide (La2O3) having outstanding high dielectric constant of 30 has been extensively investigated because it can provide a generous thickness margin as well as a considerable leakage current reduction which is essentially required in modern device applications. However, the hygroscopic and catalytic nature of La ions lead s to formation of either La-hydroxide (La(OH)3) or La-silicate (LaSiOx) resulting in degradation of device properties. The formation of La-hydroxide can cause serious issues such as shifting of flat band voltage (Vfb), increased gate leakage and increased the surface roughness. La-hydroxide may also cause a CVD reaction, ruining the self-limited nature of ALD reaction during conventional water based ALD process. Also, direct deposition of La2O3 on Si substrate has a significant amount of La-silicate phase in the grown film by the interfacial reactions with the Si. In order to overcome these intrinsic problems of pure La-oxide, some of researches have been carried out using an addition of aluminum oxide (Al2O3) layer in the pure La2O3 film. La-aluminate is potentially stable on Si substrate having less opportunity to form an interfacial layer. In addition, La-aluminate has enhanced stability to water ambient due to a gettering effect of Al2O3. In this presentation, we will focus on the detailed growth mechanisms of La-aluminate during a water based ALD process. In order to investigate initial interfacial reactions during ALD, we investigate in-situ half cycle reactions by means of x-ray photoelectron spectroscopy analysis following individual ALD pulses of tris(N,N’-diisopropylformamidinato) lanthanum [La(iPrfAMD)3], trimethyl-Al ( TMA ) and water (H2O) at a deposition temperature of 300oC. The La-aluminate sample was transferred from an ALD reactor after every individual pulse of La, Al and H2O to a monochromatic x-ray photoelectron spectroscopy (XPS) chamber via ultra high vacuum (UHV) chamber maintaining a vacuum level of less than 10-11 torr. This experimental technique enables us to investigate evolution of chemical binding status without exposure to air as the number of ALD half cycle increases. Additionally, residual C and N in the films will be also discussed.