Tsutomu Shinzawa

Aluminum Metallization Using a Combination of Chemical Vapor Deposition and Sputtering

An aluminum metallization process that combines blanket chemical vapor deposition and sputtering was developed for use in fabrication of future ultralarge scale integration interconnections. Blanket chemical vapor deposition of aluminum using dimethylaluminum hydride on titanium nitride, which provides superior step coverage and a smooth surface morphology for films of less than approximately 0.15 μm thickness, was only used for hole-filling. Subsequent aluminum alloy sputtering, which has a high deposition rate and provides smooth surface films, was used for the thickening of the aluminum films. This combination process draws on the respective advantages of both chemical vapor deposition and sputtering, which mutually compensate for each others drawbacks. As a result, via holes with a diameter of 0.3 μm and an aspect ratio of 2.7 were successfully filled. The resistance of contact holes fabricated by the combination process was slightly lower than that obtained in the conventional tungsten plug process due to low film resistivity of chemically vapor deposited aluminum. The contact resistivity for contacts to p- and n-type Si were 1.0 x 10 -7 and 2.9 x 10 -8 Ω cm 2 , respectively. Via hole resistance for 0.45 μm diameter holes was less than 1 Ω, which corresponds to a contact resistivity of less than 1.6 x 10 -9 Ω cm 2 between chemically vapor deposited aluminum and the underlayer titanium nitride.

Titanium-containing hydrofluoric acid pretreatment for aluminum chemical vapor deposition

A new solution pretreatment has been developed to improve the surface morphology of chemical vapor deposition (CVD0 Al films on SiO2. This method is simple: substrates are dipped into Ti-containing hydrofluoric acid and are dried before Al CVC. With this pretreatment, the surface morphology of the deposited Al films is improved. This improvement in surface morphology may be attributable to enhancement in Al nucleation due to the Ti adsorbed from the solution onto the substrate surface. Furthermore, the Al deposition temperature on SiO2 was able to reduced from 260 to 210°C. Lowering of the deposition temperature also improved the surface morphology of Al films. Moreover, Al films deposited at the lower temperature have a stronger (111) orientation, which is expected to provide higher electromigration resistance.

Molecular dynamics simulation of Al grain boundary diffusion for electromigration failure analysis

The grain boundary (GB) diffusion for Al interconnections has been characterized for the first time by using the molecular dynamics (MD) simulation with the embedded atom potential. The activation energy for grain boundary diffusion is found to be 0.55 eV. The simulated GB diffusivity almost agrees with the experimental data in the literature (Baluffi and Blakely, Thin Solid Films, vol. 25. p. 363, 1975). The GB diffusivity is found to be suppressed by the compressive strain and to be highly dependent on the GB rotation angle.

Adhesion layerless submicron Al damascene interconnections using novel Al-CVD

Adhesion layerless submicron damascene interconnection has been realized by using a combination of novel Al-CVD and CMP technique. A new nucleation method with tetrakis-dimethyl-amino titanium (TDMAT) gas pretreatment has enabled Al-CVD to fill Al in trenches without using a glue layer. As a result, this technology achieved Al damascene interconnections with low specific line resistance as low as 600 /spl Omega//cm with half micron line width and an aspect ratio of 3. This specific line resistance is one-third of that for conventional reactive ion etched Al line with an aspect ratio of 1.<<ETX>>

New molecular compound precursor for aluminum chemical vapor deposition

A new type of precursor for aluminum chemical vapor deposition (Al-CVD) has been developed by mixing dimethylaluminum hydride (DMAH) and trimethylaluminum (TMA). The new precursor has proven itself to be effective for Al-CVD, where a good selectivity between the Si and the SiO 2 mask, a 3.0 μΩ cm resistivity and a pure Al film with low C and O contamination levels (under 100 ppm) were achieved. Quadrupole mass and infrared absorption analysis have shown that the precursor contains a new molecular compound, consisting of a DMAH monomer and a TMA monomer. The mixture has lower viscosity than DMAH and can be easily bubbled for a stable precursor vapor supply.