Search

Copper is widely used in the semiconductor industry as interconnects due to its low resistivity, high resistance to electromigration, low temperature coefficient of resistance, and good thermal stability (1). As advanced nanoelectronics has moved towards the sub-5 nm node technology and beyond, the back-end of line interconnects process is scaled down to smaller pitch sizes with a lot of challenges (2,3). Recently, area-selective atomic layer deposition (AS-ALD) by locally passivating the surface has garnered attention as it can lead to a paradigm shift from today’s top-down VLSI fabrication by not only reducing the number of processing steps but also by alleviating key challenges associated with lithography and layer alignment at the sub-5 nm node (4). However, there are still several challenging factors to implement them in the process node successfully. Despite the enormous scientific effort in recent years, lack of surface science during cleaning and passivation of Cu surfaces impede the development of AS-ALD. Specifically, the initial surface condition of Cu films can affect not only a cleaning surface (i.e., adventitious contaminants and CuxO) but also further passivation process using a self-assembled monolayer (SAMs). Recently, the reduction of the Cu surface using vapor-phase N2H4 has been reported due to its higher reduction capability (4,5). Herein, the effect of the initial surface condition of Cu samples on both cleaning and passivation of the surfaces was investigated. Electroplated Cu films were pretreated using anhydrous N2H4 for vapor phase surface cleaning. Reflectance absorption infrared spectroscopy (RAIRS) with ALD capability was employed to elucidate the surface chemistry. During surface cleaning, N2H4 reduces the surface oxide (Cu2O) to metallic copper as well as remove adventitious surface contaminants (e.g., –CHx, –CO3, and –OH). In the case of cleaning with CH3COOH, the Cu surface reduces the surface oxide (Cu2O) to metallic copper, importantly the copper acetate which might be the intermediate material was formed after cleaning. After pretreatment, each Cu sample was immersed into 1 mM octadecanethiols (ODTs) in ethanol for 20 hours, then ALD of AlOx using TMA and H2O was performed at 120 oC. The N2H4-treated Cu sample shows better physical and chemical stability during ALD process, resulting in good selectivity compared to the SAMs on the as-is Cu. The detailed experimental results will be presented. This work is supported by Rasirc Inc. by providing the anhydrous N2H4. This work was also partly supported by the Fostering Global Talents for Innovative Growth Program (No. P0008750) through KIAT and MOTIE. J. Ahn and J. Kim also acknowledge partial financial supports by Brain Pool Program through National Research Foundation by the Ministry of Science and ICT in Korea (Grant #: 2019H1D3A2A01101691). R. P. Chaukulkar, N. F. W. Thissen, V. R. Rai, and S. Agarwal, J. Vac. Sci. Technol. A, 32, 01A108 (2014). L. F. Pena, J. F. Veyan, M. A. Todd, A. Derecskei-Kovacs, and Y. J. Chabal, ACS Appl. Mater. Interfaces, 10, 38610–38620 (2018). M. He et al., J. Electrochem. Soc., 160, D3040–D3044 (2013). D. M. Littrell, D. H. Bowers, and B. J. Tatarchuk, J. Chem. Soc. Faraday Trans. 1 Phys. Chem. Condens. Phases, 83, 3271–3282 (1987). S. M. Hwang et al., ECS Trans., 92, 265–271 (2019). Figure 1

Silicon nitride (SiNx) films have drawn great attention due to the wide range of applications such as passivation layer, gate dielectric, spacer, charge trap layer, and diffusion barrier [1]. Conventionally used LPCVD and PECVD for SiNx deposition have limitations in terms of conformal deposition and thickness scalability. Since plasma enhanced atomic layer deposition (PEALD) is expected to overcome these shortcomings, several research groups have reported SiNx film deposition. A number of studies on PEALD SiNx process using various chlorine-containing silicon precursors have been reported due to their ease in synthesis as well as good thermal stability [2]. Recently, PEALD SiNx film using a novel chlorosilane precursor, pentachlorodisilane (PCDS, HSi2Cl5) with NH3/N2 plasma was reported [3]. Under the NH3/N2 plasma condition, PCDS enhanced the growth rate (approximately > 20 %) compared to the hexachlorodisilane (HCDS, Si2Cl6), but still showed relatively poor wet etch resistance. Inspired the film characteristics, we propose to explore the feasibility of improving the wet etch resistance of PEALD-SiNx films using the different gas mixture for plasma. It has been reported that the wet etch rate of SiNx films has a linear relationship with the hydrogen concentration in the films [1]. Compared to NH3/N2 plasma, N2-H2 (forming gas) plasma improves the wet etch rate possibly due to less N-H and H-N-H bonds in the SiNx films [2]. Herein, PEALD SiNx films using PCDS as Si precursor and N2-H2 (10 % forming gas) plasma as the reactant were evaluated. The combination with PCDS and N2-H2 plasma showed a relatively lower (approximately < 10 %) growth rate than NH3/N2 plasma under a range of process temperatures (270−300 °C) whereas the wet etch resistance to HF acid was improved (> 1.5 nm/min, 500:1 HF). Studying these results, we suggest the effect of hydrogen on film properties such as growth rate, film composition, and wet etch resistance. [1] H.S. Kim, X. Meng, S.J. Kim, A.T. Lucero, L. Cheng, Y.C. Byun, J.S. Lee, S.M. Hwang, A.L.N. Kondusamy, R.M. Wallace, G. Goodman, A.S. Wan, M. Telgenhoff, B.K. Hwang, and J. Kim, ACS Appl. Mater. Interfaces 10, 44825 (2018). [2] X. Meng, Y.C. Byun, H.S. Kim, J.S. Lee, A.T. Lucero, L. Cheng, and J. Kim, Materials 9, 1007 (2016). [3] X. Meng, H.S. Kim, A.T. Lucero, S.M. Hwang, J.S. Lee, Y.C. Byun, J. Kim, B.K. Hwang, X. Zhou, J. Young, and M. Telgenhoff, ACS Appl. Mater. Interfaces 10, 14116 (2018). Figure 1

The demand for faster, smaller and more energy efficient logic devices as well as higher density, higher speed, and increased reliability for advanced memory devices has led to numerous challenges in Semiconductor device manufacturing. Novel metal materials, 3D architecture and increasing High-aspect-ratio (HAR) structures are being used to address these challenges, however this has placed additional constraints on film deposition methods. CVD and ALD of SiN are used in several applications including, gates, spacers, etch stops, liners, encapsulation layers as well as passivation layers.1 Recently PEALD of SiN is taking on an increasingly important role due to new temperature constraints of 3 may not be feasible due to the high temperature requirement (500°C-700°C) of these reactions.2 Our approach involves the development and use of a novel hydrazine delivery system in order to develop methods for thermal ALD of SiN at A hydrazine delivery system was developed to provide a stable flow of ultra-dry hydrazine gas from a liquid source in a sealed vaporizer. The liquid source combines anhydrous hydrazine and a proprietary solvent that acts as a stabilizer. The solvent is highly non-volatile, where high purity hydrazine gas may be generated in-situ and delivered to the deposition chamber while the solvent remains in the vaporizer. Testing confirms that hydrazine vapor pressure is maintained at levels viable for ALD (12-14 torr) even in the presence of the solvent used to dilute the liquid source to safe handling levels. Previous studies with hydrazine were plagued by oxygen contamination.3 This study demonstrates high purity hydrazine delivery at A study of silicon nitride deposition was conducted using hexacholorodisilane (HCDS) and hydrazine on a Si-H substrate. A custom made thermal ALD reactor was used to deposit silicon nitride films from 250-400°C. Film growth per cycle (GPC) with hydrazine was 0.4-0.5 Å/cycle at 400°C with refractive index of 1.813. Film stoichiometry was confirmed with X-ray photoelectron spectroscopy. SiN films with low impurities were achieved for oxygen (3. Film growth and resulting properties at 350°C closely resemble those grown thermally at 400°C for hexachlorodisilane and hydrazine. Some discrete differences in film density and composition start to become apparent at a growth temperature of 325°C. Specifically, film density decreases and wet etch rate increases. The presentation will compare growth rates, film density, refractive index and wet etch rate results at different temperatures for hydrogen terminated silicon. Initial growth studies with the use of Hydrazine and Organosilicon Amide precursors will also be discussed. References: X. Meng, Y.-C. Byun, H. Kim, J. Lee, A. T. Lucero, L. Cheng, J. Kim, Materials 9 (12) 1007 (2016) S. Morishita, S. Sugahara, M. Matsumura, Atomic-layer chemical-vapor-deposition of silicon-nitride. Appl. Surf. Sci. 1997, 112, 198–204. K. B. Ramos, R. K. Kanjolia, Y. K. Chabal, AVS 2013, Baltimore, Md., Paper TF + EM + NS + SS-ThA10.