| 초록 |
One of the refractory metal nitrides, WNx, has been used in many different applications because of their desirable material properties, including high melting temperatures, relatively low resistivities, chemical inertness, etc. Among those applications, the most interesting area nowadays is microelectronics, where these materials are being extensively studied as a diffusion barrier, a metal gate electrode, and a glue layer at ultra-high-aspect-ratio contact and via holes in ultra-large-scale-integrated (ULSI) devices. ALD-WNx films was generally deposited by inorganic precursor, WF6 and NH3 as a reactant though a few investigations were done using metallorganic precursors such as bis(tert-butylimido) bis(di-methylamido)tungsten(VI) [TBIDMW, (NtBu)2(NMe2)2W], and tungsten (III) precursor, W2(NMe2)6 and NH3 as a reactant at temperatures ranging from 150 to 400 ºC. In this study, we reported the ALD-WNx process using a new F-free W metallorganic precursor at the low deposition temperature between 150 and 350 ºC and the developed ALD-WNx film has been evaluated as a diffusion barrier for Cu metallization and gate electrode. The use of F-free precursor can give advantages by excluding many issues of the conventional WF6: (i) WF6 and its by-products such as HF are corrosive and can chemically attack many other materials exposed on substrate surfaces; (ii) F-containing species that are trapped inside the films may diffuse out, react with their adjacent materials such as Cu and dielectric layers, and finally degrade the device performances; and (iii) fluorine impurities residing on the surface of the films may impede the adhesion of Cu. The results showed that self-limited film growth with both precursor and reactant (NH3 plasma) pulsing time, which is the typical characteristics of ideal ALD, could be obtained at 250 ºC. The XRD and TEM analysis showed that the film had polycrystalline structure with cubic WN phase and its step coverage was good [~ 60 % at a very small-sized trench structure (bottom width: 15 nm and aspect ratio of ~ 3.5)]. In order to improve the properties, we also evaluated the ALD-WNx process using N2/H2 mixture plasma as a reactant. The results indicated that the use of N2/H2 mixture plasma could control the phase of the film and composition by controlling the gas ratio of N2/H2. |
