Low-Temperature Low-Resistivity PEALD TiN Using TDMAT under Hydrogen Reducing Ambient

Abstract

Titanium nitride ͑TiN͒ films were deposited using plasma-enhanced atomic layer deposition ͑PEALD͒ from the organometallic precursor tetrakis-dimethyl-amino-titanium ͑TDMAT͒ with hydrogen ͑H 2 ͒ as a coreactant. Low-resistivity values lying from 210 to 275 ⍀ cm were achieved for 10 nm thick films deposited at low temperature: 150°C. The effects of temperature, plasma time, and plasma power were investigated. It was demonstrated that the chemical reaction is complementary and self-limiting. A minimum energy is necessary to reach the low-resistivity plateau. Chemical and physical properties of the films are also reported and a surface reaction mechanism is proposed. It is suggested that after TDMAT chemisorption to the surface, amines are removed by hydrogen radicals, and at the same time, titanium carbide bonds ͑Ti-C͒ are formed. The low resistivity results from the presence of Ti 2 C or Ti 2 N phases in the PEALD TiN film. The industrial viability of this process was also evaluated on 300 mm wafers. Good performances were obtained on wafer-to-wafer uniformity and step coverage, while some improvements related to the within-wafer uniformity are required.TiN is one of the most widely used metals for electrodes of metal/insulator/metal ͑MIM͒ capacitors because its barrier height and chemical stability with most of the dielectrics generally provide low leakage current and good voltage linearity for capacitors, 1,2 and also because it is easy to etch and to polish compared to other metals for electrodes such as TaN, WN͑C͒, Ru... . In the case of threedimensional ͑3D͒ capacitors with high-aspect-ratio features ͑to increase capacitance density͒, metal electrodes should be very conformal with low resistivity for device operation in high frequencies.While chemical vapor deposition ͑CVD͒ TiN is faced with some limitations related to poor conformality, atomic layer deposition ͑ALD͒ offers the outstanding advantage of thickness uniformity, even on the sidewalls of 3D capacitors, thanks to its two main characteristics of complementary and self-limiting surface reactions. 3 The aim of the study was to develop a low-temperature process for the deposition of low-resistivity TiN films, with the lowest defectivity. In this article, defectivity refers to the presence of solidphase particles embedded in the deposited film, or on top of it, generated in gas phase or coming from some peeled-off films deposited inside the reactor and carried by the reactant gas flows.The motivations of lowering the TiN deposition temperature are the integration of the electrode material for MIM capacitors and the investigation of the ALD process. The capacitor electrodes are embedded in the upper part ͑"back-end of line"͒ of integrated circuits, i.e., within the stack of insulators and interconnects. This environment can be very sensitive to high temperatures, especially when low-permittivity dielectrics ͑low-k͒ or some silicides like NiSi are used. From the ALD process point of view, lowering temperature minimizes decomposition of the organometallic pr...

Plasma-Assisted Atomic Layer Deposition: Basics, Opportunities, and Challenges

“…oxidation by an O 2 plasma 69,70,119,122,130,132,149 and nitridation by NH 3 or N 2 plasmas 119,129,132 ), substrate cleaning, 98 post-deposition treatments, 141,164 and reactor wall conditioning and cleaning. 240 For example, a layer of TiN covering the walls of the reactor can be removed easily by running a F-based plasma such as one generated in NF 3 or SF 6 . 136 The aforementioned merits of plasma-assisted ALD can be illustrated in more detail by several results that have been reported for various material systems in the recent years.…”

“…In particular cases, a low-resistivity barrier and adhesion layer could also simultaneously act as a seed-layer for the electrochemical deposition process of Cu. 161,166,[180][181][182][183]220,240 Triggered by these challenges, Rossnagel and co-workers at IBM developed plasma-assisted ALD processes of Ta and Ti using the metal halides TaCl 5 and TiCl 4 as precursors and an H 2 plasma as a reducing agent. 206 As mentioned in Sec.…”

Gadolinium nitride films deposited using a PEALD based process

“…Pure hydrogen plasma are often used to produce metal films [23]; however, they can also be used with nitrogen containing precursors, such as alkylamides, to produce nitrides as the precursor provides both the metal and nitrogen. HfN [47], TaN [35,41] and TiN [48] have been grown using this approach. Pure N 2 plasma has also been used for the deposition of Hf 3 N 4 [49], TiN [46] and ZrN [50] with alkylamide precursors.…”

Plasma-Enhanced Atomic Layer Deposition (PEALD) of TiN using the Organic Precursor Tetrakis(ethylmethylamido)Titanium (TEMAT)

“…Interestingly, the resistivity is low at 350°C, when decomposition should occur. Such deposition by precursor decomposition is similar to the work of Caubet et al [9], where TDMAT was used, resulting in low resistivity films. The carbon concentration and N/Ti ratio, as seen in Figure 2 due to incomplete surface reaction of the precursor at such a low temperature.…”

“…However, growth rates are low and the hydrochloric acid (HCl) byproduct may cause selfetching [7], copper pitting [4][5] and/or reactive site poisoning [5,7]. The drawbacks of using TiCl 4 precursor has lead to research into metalorganic precursors like tetrakis(dimethylamido)titanium (TDMAT) [8][9], tetrakis(ethylmethylamido)titanium (TEMAT) [8], and tetrakis(diethylamido)titanium (TDEAT) [8,10]. Although TDMAT produces films at a higher deposition rate and with lower resistivity, there is higher carbon content in the film at higher temperatures from the decomposition of TDMAT [8].…”