Monday, June 29, 2020

AVS ALD 2020 starts today and RASIRC is presenting and contributing with the latest results using´peroxide and hydrazine in Atomic Layer Porcessing

RASIRC is contributing to two oral and two poster presentations at the AVS ALD2020 Virtual conference starting today. The results summarize the latest development using either peroxide (H2O2) or hydrazine (N2H4) as powerful co-reactants in atomic layer processing of high-quality films with higher overall performance beyond that of classical thermal or plasma ALD processes.

Atomic Layer Annealing of AlN to Template The Growth of High Thermal Conductivity Heat Spreader Films (LINK)

Scott Ueda‚ Aaron McLeod (University of California‚ San Diego); Michelle Chen‚ Chris Perez‚ Eric Pop (Stanford University); Dan Alvarez (RASIRC); Andrew Kummel (University of California‚ San Diego)

In this study of AlN Atomic Layer Annealing (ALA)‚ two metal precursors (TMA and TDMAA) were compared using anhydrous N2H4 as a co-reactant and argon ions with tuned energy for the third pulse. High-quality AlN films are deposited with large grain size and low C/O contamination which can then be used as a templating layer for further high-speed AlN film growth.

Effect of Copper Surface Condition on Passivation Characteristics for Applications to Area Selective Atomic Layer Deposition (LINK)

Su Min Hwang (University of Texas at Dallas); Harrison Kim‚ Jin-Hyun Kim (The University of Texas at Dallas); Yong Chan Jung (University of Texas at Dallas); Luis Fabian Pena‚ Kui Tan‚ Jean-Francois Veyan (The University of Texas at Dallas); Dan Alvarez‚ Jeffrey Spiegelman (RASIRC); Kashish Sharma‚ Paul Lemaire‚ Dennis Hausmann (Lam Research Corp.); Jiyoung Kim (University of Texas at Dallas)

Herein‚ electroplated Cu films were treated using glacial acetic acid (CH3COOH) and anhydrous N2H4‚ respectively.4 After cleaning‚ the Cu samples were immersed in a 1 mM solution of octadecanethiols (ODTs) in ethanol for 20 h. To elucidate the surface chemistry and stability of ODTs‚ the passivated Cu samples were loaded into an in-situ reflectance absorption infrared spectroscopy (RAIRS) system equipped with an ALD chamber‚ then ALD of AlOx process was performed using TMA and H2O at 120 oC. During surface cleaning‚ CH3COOH removes surface adventitious contaminants (e.g.‚ –CHx‚ –CO3‚ and –OH)‚ and most importantly‚ reduces the surface oxide (Cu2O) to metallic copper by forming copper acetate as an intermediate material. In the ex-situ XPS and RAIRS‚ the SAMs on the CH3COOH-treated Cu sample gives poor selectivity of ALD-AlOx compared to the SAMs on the as-is Cu and N2H4-treated Cu‚ respectively. It implies that the residual copper acetate on the surface can affect the chemisorption of ODTs during passivation‚ eventually attributing a relatively lower surface coverage‚ poor thermal stability of ODTs‚ and poor selectivity during ALD process. To circumvent the issue‚ the effect of post-treatment after surface cleaning with CH3COOH was investigated. Vacuum treatment of the sample under the UHV condition (~10-8 Torr) can partially reduce the copper acetate by forming -CHx and -OH species. However‚ a post-annealing at 75 oC effectively removes the copper acetate and residual contaminants on the surface‚ which can improve not only ODTs quality in the passivation process but also the increase of nucleation delay during the consecutive ALD process. The detailed experimental results will be presented.

Thermal SiNx Using NH3 and Anhydrous Hydrazine as Nitriding Agents (LINK)

Su Min Hwang‚ Dan Le‚ Arul Ravichandran‚ Aswin Kondusamy (University of Texas at Dallas); Dan Alvarez‚ Jeffrey Spiegelman (RASIRC); Jiyoung Kim (University of Texas at Dallas)
Deposition of ultrathin and uniform SiNx films with high conformality is required for ULSI due to application restrictions‚ such as thickness and complicated surface areas. In general‚ the plasma-enhanced ALD (PEALD) process allows a low temperature process for such film deposition‚ but potentially results in poor conformality‚ creates surface damage‚ and is not applicable on sensitive substrates. The thermal ALD (tALD) process can overcome these issues; however‚ it requires a higher deposition temperature range for SiNx films. In this study‚ we focus on establishing a high quality SiNx tALD deposition process at relatively low temperatures (350 °C – 650 °C) for ammonia (NH3) and evaluate the properties of films deposited using hydrazine.
In this experiment‚ hexachlorodisilane (HCDS) is used as the source of silicon‚ along with BRUTE hydrazine and ammonia as the precursors for nitrogen. A PEALD/ tALD chamber (Rocky Mountain Vacuum Tech Inc.) is employed to deposit SiNx films with a working pressure between 150 – 160 mTorr. Furthermore‚ to eliminate the possibility of condensation of precursor or residual products‚ the chamber walls and precursor delivery lines are heated to 120 °C and 100 °C‚ respectively. The experimental temperature range is established from 350 °C to 650 °C. At the temperature range of 450 °C – 550 °C‚ the index of refraction (R.I.) of SiNx films deposited using hydrazine is up to 2.0‚ which further coincides with the earlier reported result‚ with a R.I. as high as 2.1.
Good growth rate, high etch resistance, and high uniformity SiNx thin film can be deposited using hydrazine. Top as deposited >96% resp after 500:1 HF >90% conformality.

Aluminum Oxide ALD with Hydrogen Peroxide: Comparative Study of Growth and Film Characteristics for Anhydrous H2O2‚ H2O2/H2O Mixtures‚ H2O and Ozone (LINK)

Jeffrey Spiegelman‚ Dan Alvarez (RASIRC); Keisuke Andachi‚ Gaku Tsuchibuchi‚ Katsumasa Suzuki (Taiyo Nippon Sanso Corporation‚ Japan)

Thermal low temperature ALD has seen a resurgence in activity due to difficulties found with plasma approaches on 3D surfaces. Hydrogen peroxide reactivity may benefit low temperature growth rates and achieve improved film properties. We studied:
  • Gas-phase hydrogen peroxide‚ delivered from an anhydrous‚ ampoule-based formulation by use of a membrane delivery system.
  • High concentration H2O2/H2O delivery by in situ concentration methods and use of a membrane vaporizer as a gas generator.
Composition of films grown by all four oxidant methods was measured by XPS; all films have near stoichiometric Al2O3 composition‚ within the experimental error of the instrument.

Dielectric Breakdown Strength measurement comparing films grown by all three oxidants. Hydrogen peroxide based film shows a significant increase in this electrical property where H2O2/H2O > H2O2 > O3 > H2O.
Initial wet etch rate studies (7.14% buffered HF) were performed on H2O2/H2O and H2O films grown at 200°C. In this instance‚ H2O2/H2O film has an etch rate of 69.9nm/min vs 81.5nm/min for water: a 15% improvement in etch resistance.
Electrical properties of resultant Al2O3 films have been examined. For films grown at 300C‚ Dielectric Breakdown Strength was measured. Here‚ film grown with H2O2/H2O was significantly greater than both water and ozone grown films; anhydrous hydrogen peroxide was similarly improved‚ but to a lesser degree. An analogous result was obtained when measuring leakage current.

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