Silicon precursor development for advanced dielectric barriers for VLSI technology Anupama Mallikarjunan a,⇑ , Andrew D. Johnson a , Laura Matz a , Raymond N. Vrtis a , Agnes Derecskei-Kovacs a , Xuezhong Jiang a , Manchao Xiao b a Air Products and Chemicals, Inc., 7201 Hamilton Blvd, M/S R4203, Allentown, PA 18195, United States b Air Products and Chemicals, Inc., 1969 Palomar Oaks Way, Carlsbad, CA 92011, United States article info Article history: Available online 5 May 2011 Keywords: Barrier SiCN BEOL Interconnects abstract For back end of line (BEOL) interconnects, maintaining device reliability while scaling the dielectric stack is a continual challenge. In this paper, the ability to improve the dielectric barrier properties of silicon carbonitride (SiCN) films is discussed. Designing the precursor structure to provide improved film prop- erties in a plasma-enhanced chemical vapor deposition (PECVD) system is demonstrated. The precursor was optimized for maximizing the density value of the deposited film for a given dielectric constant with- out compromising the electrical properties. For the deposited SiCN films, the nature of carbon bonding was identified as a key structural element correlating to critical barrier film properties such as leakage and hardness. Ó 2011 Elsevier B.V. All rights reserved. 1. Introduction Continual scaling of BEOL interconnect capacitance with each technology node necessitates implementation of lower dielectric constant (k) films [1]. Traditionally, scaling of BEOL barrier films has been achieved through process optimization and multi-layered structures (e.g., SiCN/SiCO); enabling intermediate reductions in effective k while retaining barrier properties such as etch selectiv- ity and hermeticity. These approaches, however, restrict further scaling due to process limitations. An alternative strategy is to de- sign a precursor that incorporates the desired network into the precursor structure; enabling more efficient deposition which could maintain existing film density while lowering dielectric con- stant. In this paper, nitrogen-containing precursors with different bonding configurations were studied. Using bond energy calcula- tions, BASICN series of precursors was selected for their combina- tion of high Si–N and Si–C bond energies. By engineering the desired structure into an optimized precursor, reduced k value SiCN films are presented which also balance the nitrogen content for good barrier properties. 2. Computational methods Precursor structures were modeled with proceeding computa- tional techniques. All bond energies were calculated assuming homolytic cleavage, i.e., calculating the energies of the two fragment radicals and subtracting from their sum the energy of the molecule. All calculations were performed using Density Func- tional Theory, specifically the gradient corrected density functional BLYP in conjunction with a double numerical polarized basis set (BLYP/dnp) and Effective Core Potentials as implemented in Dmol 3 by Accelrys within the Materials Studio program package (version 5.0) [2,3]. In this work, the reported values of bond energies were not corrected for zero point vibrations. 3. Experimental methods All barrier film depositions were performed using a 200 mm P5000 applied materials PECVD chamber with direct liquid injec- tion. With the exception of 3MS results, all other precursors were liquids with varied delivery temperatures dependent on the pre- cursor’s boiling point. Typical BASICN liquid precursor flow rates were 200–800 mg/min, plasma power density was 0.75–2 W/cm 2 , pressure was 3–5 Torr and temperature was 350 °C. A mer- cury probe was utilized for all film measurements where dielectric constant, electrical breakdown field and leakage are presented. Dielectric constant reported is the commonly quoted out-of plane-value. Leakage current density (J) is quoted in this work as the value taken from current vs voltage measurements at an elec- tric field of 2 MV/cm. This value is used as a representative com- parison of leakage behavior of different films. Modulus and hardness were measured by nanoindentation and are quoted at 5% and 10% of the film thickness respectively. Bonding properties of the dielectric films were analyzed with a Nicolet transmission FTIR tool. All density measurements were performed with X-ray reflectivity (XRR). X-ray Photoelectron Spectroscopy (XPS) experi- ments were performed to determine film composition (Si, C, N, 0167-9317/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.mee.2011.04.014 ⇑ Corresponding author. E-mail address: mallika@airproducts.com (A. Mallikarjunan). Microelectronic Engineering 92 (2012) 83–85 Contents lists available at ScienceDirect Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee