The Integration of Plasma Enhanced Atomic Layer Deposition (PEALD) of Tantalum-Based Thin Films for Copper Diffusion Barrier Applications

Abstract

A plasma-enhanced atomic layer deposition (PEALD) process for the growth of tantalumbased compounds is employed in integration studies for advanced copper metallization on a 200- mm wafer cluster tool platform. This process employs terbutylimido tris(diethylamido)tantalum (TBTDET) as precursor and hydrogen plasma as the reducing agent at a temperature of 250°C. Auger electron spectrometry, X-ray photoelectron spectrometry, and X-ray diffraction analyses indicate that the deposited films are carbide rich, and possess electrical resistivity as low as 250νΔcm, significantly lower than that of tantalum nitride deposited by conventional ALD or CVD using TBTDET and ammonia. PEALD Ta(C)N also possesses a strong resistance to oxidation, and possesses diffusion barrier properties superior to those of thermally grown TaN.

Diffusion Barrier Properties of Atomic Layer Deposited Ultrathin Ta[sub 2]O[sub 5] and TiO[sub 2] Films

“…Isothermal annealing was used to investigate the barrier properties of ALD and PE-ALD Ta͑C͒N films with thicknesses of 1 and 2 nm using TBTDET as a precursor with and without hydrogen plasma. 28 The breakdown temperature was determined by Rutherford backscattering spectrometry ͑RBS͒ measurements. The PE-ALD films remained stable after annealing at 450°C but failed after annealing at 550°C.…”

Properties of Plasma-Enhanced Atomic Layer Deposition-Grown Tantalum Carbonitride Thin Films

“…Together with comparable results of Greer, 23 to our knowledge, this value is the lowest currently pub-lished resistivity for tantalum nitride based films deposited by metallorganic chemical vapor deposition, PEALD, or ALD. 10,11,[16][17][18][19][20][21][22]32,30,[33][34][35][36] The increase in resistivity at lower film thicknesses can be attributed to the so-called size effect and the increasing proportion of the thin native surface tantalum oxide layer. Therefore, it is conceivable that in situ sheet resistance measurements would result in even lower resistivities especially for film thicknesses below 10 nm.…”

“…There are many publications regarding ALD and PEALD of tantalum nitride based films, but only a few about tantalum carbide deposition. 10,11 To our knowledge, so far there are no publications about the ALD or the PEALD of stoichiometric tantalum carbonitride films.…”

Low Temperature ALD MoN for Applications in Nanoscale Devices

“…While care must always be taken when comparing results from different research groups, these results indicate that ALD MoN possesses competitive barrier properties when compared to other materials being investigated for emerging barrier applications. 1,6,7…”

“…The continued downscaling of device dimensions has placed a high priority on the development of robust copper barrier/liner materials. 1 Moreover, the associated processes used to deposit these materials need to be carried out at reduced temperatures to allow integration with back-end-of-the-line (BEOL) processing, and are required to yield smooth, conformal films in aggressive trench/via structures with atomic layer scale thickness and uniformity control 1 . In this respect, atomic layer deposition (ALD) is emerging as a highly promising copper barrier/liner deposition technique, due to its inherent excellent step coverage and precise thickness control.…”