Atomic Layer Deposition of W[sub 1.5]N Barrier Films for Cu Metallization

Abstract

An atomic layer deposition process to grow tungsten nitride films was established at 350°C with a pulse sequence of WF 6 /NH 3 /C 2 H 4 /SiH 4 /NH 3 . The film composition was determined with Rutherford backscattering as W 1.5 N, being a mixture of WN and W 2 N phases. The growth rate was ϳ1 ϫ 10 15 W atom/cm 2 per cycle ͑monolayer of W 2 N or WN͒. The films with a thickness of 16 nm showed root-mean-square roughness as low as 0.43-0.76 nm. The resistivity of the films was stable after 50 cycles at a value of 480 ⍀ cm. Results of four-point probe sheet resistance measurements at elevated temperature demonstrated that our films are nonreactive with Cu at least up to 500°C. Results of I-V measurements of p + /n diodes before and after heat-treatment in ͑N 2 + 5% H 2 ͒ ambient at 400°C for 30 min confirmed excellent diffusion barrier properties of the films.

Recent Developments of Atomic Layer Deposition Processes for Metallization

“…Resistivity can be effectively brought down to 350 − 400 µΩ cm at a low process temperature of 300 °C. In other work done by Bystrova et al,163 ethene (C 2 H 4 ) and SiH 4 were used instead of TEB for WN x deposition, and set the ALD sequence to a new record with a four‐step ABCD sequence. It was not clear if ethylene plays an active role in the ALD surface reaction, however in both cases the obtained film had a very high growth rate at 2.8 Å per cycle, indicating a possible mechanism similar to that of the metallic W ALD reaction between WF 6 and SiH 4 .…”

Synthesis of nano-structure tungsten nitride thin films on silicon using Mather-type plasma focus

“…Various techniques have been employed for the synthesis of tungsten nitride films such as pulsed laser depositions (14), reactive magnetron sputtering (12,15), atomic layer *Corresponding author. Email: ahussnainsyed@gmail.com deposition (16), physical vapor deposition (17,18), and plasma enhanced chemical vapor deposition (18). We employed plasma focus device for deposition of tungsten nitride thin films on silicon substrate at room temperature by different deposition shots.…”

A study of structural and mechanical properties of nano-crystalline tungsten nitride film synthesis by plasma focus

“…Tungsten nitride coatings are one of them, have high hardness, high melting point and are chemically inert with high conductivity (1). These worthy properties of tungsten nitride films make them a suitable material for various applications such as hard, wear-resistant protective coatings (2)(3)(4) and diffusion barriers at elevated temperature in microelectronics devices (5)(6)(7)(8) and can also be used electrodes for field effect transistors and thin film capacitors. Various deposition techniques have been used for the synthesis of tungsten nitride films such as direct current/radio-frequency (DC/RF) sputtering (9), pulsed laser ablation (10), plasma focus (11), thermal chemical vapor deposition, cathodic arc (2), chemical vapor deposition, (6) etc.…”