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

Abstract

Diffusion barrier properties of ultrathin Ta 2 O 5 and TiO 2 films deposited by the atomic layer deposition ͑ALD͒ method were investigated. The oxide films were deposited using well-defined deposition processes with metal alkoxides and water as precursors. Tantalum oxide films were deposited from tantalum pentaethoxide and water and titanium dioxide films from titanium tetramethoxide and water, both at 240°C. The films examined in the diffusion barrier tests were in the thickness range of 1 -4 nm. The breakdown temperatures of the annealed Cu/barrier/Si structures were determined from the increase in the sheet resistance, X-ray diffraction data, and etch-pit test results. From the studied barrier films, the 3-nm-thick titanium dioxide film was found to possess the best resistance to copper diffusion as the first etch pits were observed only after the annealing at 650°C.

Improved Thermal Stability and Electrical Performance by Using PEALD Ultrathin Al2O3 Film with Ta as Cu Diffusion Barrier on Low k Dielectrics

“…A systematic study of ALD oxide films as Cu diffusion barrier onto a low k dielectric has been rarely reported. [7][8][9][10][11][12] In this work, ultrathin Al 2 O 3 films were deposited by PEALD together with a Ta adhesion layer, and their properties as a Cu diffusion barrier on a low k dielectric (k = 2.5) were studied.…”

“…The details of the ALD growth can be seen elsewhere. 7 Then the Cu(50 nm)/Ta (5 nm) film stacks were deposited by DC magnetron sputtering. The thin Ta film was used as a glue layer to promote adhesion between the Cu and Al 2 O 3 barrier layers.…”

Effect of film thickness on the breakdown temperature of atomic layer deposited ultrathin HfO2 and Al2O3 diffusion barriers in copper metallization

“…Ultrathin Ta 2 O 5 and TiO 2 films showed high thermal stability and based on sheet resistance data, the breakdown temperature of even 1 nm-thick Ta 2 O 5 and TiO 2 films was as high as 650 1C [18]. We have found that the failure temperature of 3 nm-thick HfO 2 and Al 2 O 3 barrier layers is 700 and 750 1C, respectively [19].…”

“…However, it is widely considered that the resistivity of the barrier layers become insignificant in the case of ultrathin films [18,19].…”

“…The diffusion barrier performance of other insulating metal oxides deposited using ALD was also investigated [18,19]. Ultrathin Ta 2 O 5 and TiO 2 films showed high thermal stability and based on sheet resistance data, the breakdown temperature of even 1 nm-thick Ta 2 O 5 and TiO 2 films was as high as 650 1C [18].…”