Kazumi Sugai

Large scale two-step selective aluminum CVD on laser patterned palladium lines

Abstract In the present report we first outline and characterize the details of uniform deposition of PdAc from an acetone solution on a large area. Then, we investigate the parameters that highly influence the thickness and quality of the laser direct-written palladium lines (spin coating speed among others). Currently, good quality and uniform patterning of laser written thin lines of Pd have been achieved on samples as large as 4 inches in diameter. The Pd lines are well resolved (minimum of 3 μm in width now) and exhibit fairly good resistivity around 30 μΩ⋯cm. They also showed good adhesion to the SiO 2 substrate as they endure repeated Scotch tape adhesion tests. Moreover, the second step of highly selective Al-CVD has been investigated under various conditions and gave rise to resistivities of about 6.5 μΩ⋯cm and 3000 A thickness for a 7 min deposition. This process stands out as very promising for packaging and high density interconnect technologies.

Aluminum chemical vapor deposition reaction of dimethylaluminum hydride on TiN studied by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry

To understand the nucleation mechanisms of aluminum film during chemical vapor deposition (CVD), the reactions of dimethylaluminum hydride (DMAH) with oxidized TiN and Si surfaces were studied by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). It was observed that DMAH exposure reduced the native oxide on the TiN surface, resulting in a clean TiN surface. The reduction of the native oxide and the deposition of Al on the TiN surface were enhanced with increasing DMAH dose. In contrast with the reaction on the TiN surface, no reduction of native oxide by DMAH exposure was observed on the Si surface except at the uppermost surface level analyzed by TOF-SIMS. The amount of Al deposited on the oxidized Si surface was less than that on the oxidized TiN surface under the same experimental conditions and was largely independent of the amount of DMAH dose over the studied range. The reduction of native oxide and the appearance of a clean TiN surface are thought to be important in accounting for the nucleation mechanism and the improved surface morphology of Al film deposited on TiN surfaces using the CVD process.

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.

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.