Paper AP+2D+EM+PS+TF-MoM8
Area-Selective Atomic Layer Deposition of Metal Oxides on an Inhibitor-Functionalized SiO₂ Surface

Monday, October 21, 2019, 10:40 am, Room A214

The continued downscaling of modern semiconductor devices together with the incorporation of 3D architectures places new constrains on conventional lithography techniques. To enable further advances in patterning process, new techniques will be required for next-generation devices to overcome the challenges of limiting the growth of desired materials in a specific area. One method to address these issues is area-selective atomic layer deposition (ALD), which provides the opportunity to build defined patterns from the bottom-up at the atomic-level accuracy. In this study, we will focus on area-selective ALD of metal oxides including ZrO₂ and Al₂O₃ with a metal as the growth surface and inhibitor-functionalized SiO₂ as the non-growth surface. To inhibit ALD, the SiO₂ surfaces were functionalized with aminosilane inhibitors through the vapor phase or with a solution-based method. The functionalized SiO₂ surfaces were characterized by transmission Fourier transform infrared (FTIR) spectroscopy, ellipsometry, and water contact angle measurements. Metal oxides including ZrO₂ and Al₂O₃ were deposited by ALD using metal precursors and H₂O over a temperature range of 150-250 °C. In situ attenuated total reflection FTIR spectroscopy was utilized to identify the surface reactions sites and absorbed surface species during ALD. In addition, the corresponding film growth was measured using in situ four-wavelength ellipsometry.

Using in situ optical diagnostics, we show the mechanism for the breakdown in selectivity during area-selective ALD on a SiO₂ surface that is functionalized with aminosilanes. The infrared spectra show that aminosilane inhibitors react with almost all of the surface –SiOH groups forming Si–O–Si–R bonds on the surface (see Figure 1). After repeated exposure of the functionalized SiO₂ surface to TEMAZ and ZTB, these precursors react with Si–O–Si bonds without surface –SiOH groups (see Figure 2). Although small growth in the first few ALD cycles is not detected by in situ ellipsometry, growth inhibition breaks down after an increased number of ALD cycles. These results suggest that it is an additional requirement to suppress other reactions with a higher activation energy barrier during ALD expect removing main surface reactive sites through surface functionalization. To further impede growth of metal oxides on functionalized SiO₂ surface, a two-step functionalization method was developed to passivate the SiO₂ surface while providing additional steric blocking for the underlying substrates. Comparative studies were carried out to evaluate the effect of different functionalization methods on suppressing the nucleation during ALD.