Review—Ruthenium as Diffusion Barrier Layer in Electronic Interconnects: Current Literature with a Focus on Electrochemical Deposition Methods

Abstract

Ruthenium is one of the most promising candidates to replace tantalum and titanium based diffusion barrier layers in microelectronics. Its unique properties allow the deposition of ultrathin layers with controlled thickness by means of a wide variety of different techniques. Ruthenium barriers are characterized by good thermal stability, low resistivity and great adherence. Moreover, the copper filling deposited during the Damascene process can be directly applied on the barrier without the need of a seed layer. As a consequence of the industrial interest in developing new ruthenium based interconnects technologies, a significant literature has been produced in the last few years. The scope of the present work is to collect and analyze the literature on the topic, investigating in this way the technologies developed in the past and the current development stage of ruthenium based barrier layers. Due to their multiple advantages, a special focus is devoted to the manufacturing of ruthenium diffusion limiters by mean of wet electrochemical processes.

Effect of ethylenediamine on CMP performance of ruthenium in H2O2-based slurries

“…9 shows the resulting equivalent circuit, and the tted values are shown in Table 2. The corresponding values of C f and C dl in the table can be calculated by the following eqn (10), where f z im Àmax is the frequency value at which the imaginary part of the impedance in the Nyquist plots is maximum. 37-39…”

“…Ruthenium is a chemically stable transition metal with a high melting point (2250 C), a resistivity (7.1 mU cm) lower than that of Ta (13.1 mU cm), and excellent adhesion with copper. [5][6][7][8][9][10][11] More importantly, the continuous copper lm can be conformally and directly deposited on the ruthenium surface, while no intermetallic compound is formed between copper and ruthenium. 7,9,12,13 Ruthenium, being a chemically stable and hard metal, is difficult to achieve the high removal rate in CMP process.…”

Nanometer-thin pure boron CVD layers as material barrier to Au or Cu metallization of Si

“…An extra issue with Cu interconnect is that Cu diffuses rapidly, not only in Si but also through SiO 2 at temperatures as low as 200-300°C [11]. Here also, TiN has been extensively studied as a diffusion barrier [12,13], along with other barrier materials that become interesting for meeting the requirements of down-scaling such as W [14], Ta [14,15], TaSi [15], TaN [15], Ti-Si-N [16], and Ru [17].…”

Plasma Enhanced Atomic Layer Deposition of Ruthenium Films Using Ru(EtCp)2 Precursor

“…Thin ruthenium films are highly demanded in a wide range of applications. Ruthenium is a leading candidate for next-generation integrated circuit (IC) interconnection [1][2][3][4], as an ultra-thin layer of ruthenium has an electrical conductivity higher than other competing metals [5], does not require special barrier layers, and can be deposited in narrow trenches by atomic deposition (ALD) [6,7]. Ruthenium is also a promising candidate for the electrodes of the dynamic random-access memory (DRAM) capacitors [8], gate electrodes in metal oxide semiconductor transistors (MOSFETs) [9], and high conductive coating for MEMS devices [10,11].…”