Techn. University, Diss., 2004--Dresden.

Techn. Universiẗat, Diss., 2004--Dresden.

Zugl.: Chemnitz, Techn. Univ., Diss., 2003

Techn. Universiẗat, Diss., 2002--Chemnitz.

In this paper, a study of tungsten metallization in advanced BEOL interconnects is presented. A mature 10 nm process is used for comparison between the tungsten and conventional copper metallization. Wafers were processed together till M1 dual-damascene etch then separated for different metallization. Tungsten metal line of 24 nm width is showing a 1.6X wire resistance comparing to the copper metal line. Comparable opens/shorts yield were obtained on a 0.8 M comb serpentine, Kelvin-via and 4K via chains. Similar physical profile were also achieved. This study has demonstrated the feasibility of replacing the copper by tungsten at BEOL using the conventional tungsten metallization tools and processes. This could be a cost- effective solution for the low-power products.

In der Halbleitertechnik, wie auch in der chemischen Sensorik werden Metallstrukturen mit geringen Strukturbreiten auf Substratoberflächen mit sehr niedriger mittlerer Rauhtiefe (wie Glas bzw. polierten Siliziumeinkristallen) benötigt. Die für diesen Zweck industriell angewandten Verfahren sind solche, die mit einer Abscheidung aus der Gasphase arbeiten (PVD, CVD). In der vorgelegten Arbeit werden zwei Varianten zur Sensibilisierung von Silikatglasoberflächen mit Zinkoxid für das electroless plating von Nickel-Phosphor-Schichten beschrieben. Die Strukturierung erfolgte mit einem photolithographischen Prozess. Die so sensibilisierten Glasoberflächen wurden in einer sauren Palladiumchloridlösung aktiviert und in einer alkalischen Lösung mit Nickel-Phosphor metallisiert. Nach dem elektrolytischen Abscheiden einer Gold- bzw. Silberschicht sind elektrochemische Untersuchungen zur (Langzeit-)Stabilität der Schichtsysteme durchgeführt worden, in deren Verlauf der Nachweis der Eignung für den Einsatz als Elektroden in elektrochemischen Sensoren erbracht worden ist.

Zugl.: Saarbrücken, Univ., Diss., 2009

Copper has become the material of choice for metallization of high-performance ultra-large scale integrated circuits. As the feature size is continuously decreasing, metal-organic chemical vapor deposition (MOCVD) appears promising for depositing the Cu seed layer required for electroplating, as well as for filling entire interconnect structures. In this work, four novel organophosphane and organophosphite Cu(I) trifluoroacetates were studied as precursors for Cu MOCVD. Details are reported on CVD results obtained with Tris(tri-n-butylphosphane)copper(I)trifluoroacetate, (ⁿBu₃P)₃CuO₂CCF₃. Solutions of this precursor with acetonitrile and isopropanol were used for deposition experiments on 100 mm Si wafers sputter-coated with Cu, Cu/TiN, and Al(2 % Si)/W. Experiments were carried out in a cold-wall reactor at a pressure of 0.7 mbar, using a liquid delivery approach for precursor dosage. On Cu seed layers, continuous films were obtained at low deposition rates (0.5 to 1 nm/min). At temperatures above 320°C, hole formation in the Cu films was observed. Deposition on TiN led to the formation of single copper particles and etching of the TiN, whereas isolating aluminum oxyfluoride was formed after deposition on Al(Si)/W. It is concluded that the formation of CF₃ radicals during decarboxylation has a negative effect on the deposition results. Furthermore, the precursor chemistry needs to be improved for a higher volatility of the complex.

Tantalum and tantalum nitride thin films are routinely applied as diffusion barriers in state-of-the-art metallization systems of microelectronic devices. In this work, such films were prepared by reactive magnetron sputtering on silicon and oxidized silicon substrates and studied by spectroscopic ellipsometry in the spectral range from 190 nm to 2.55 μm. The complex refractive index for thick films (75 to 380 nm) was modeled using a Lorentz-Drude approach. These models were applied to film stacks of 20 nm TaN / 20 nm Ta on unoxidized and thermally oxidized Si. With free oscillator parameters, accurate values of the film thicknesses were obtained according to cross-sectional scanning electron microscope (SEM) measurements. At the same time, a strong variation of the optical properties with film thickness and substrate was observed.

Copper has become the material of choice for metallization of high-performance ultra-large scale integrated circuits. As the feature size is continuously decreasing, metal-organic chemical vapor deposition (MOCVD) appears promising for depositing the Cu seed layer required for electroplating, as well as for filling entire interconnect structures. In this work, four novel organophosphane and organophosphite Cu(I) trifluoroacetates were studied as precursors for Cu MOCVD. Details are reported on CVD results obtained with Tris(tri-n-butylphosphane)copper(I)trifluoroacetate, (ⁿBu₃P)₃CuO₂CCF₃. Solutions of this precursor with acetonitrile and isopropanol were used for deposition experiments on 100 mm Si wafers sputter-coated with Cu, Cu/TiN, and Al(2 % Si)/W. Experiments were carried out in a cold-wall reactor at a pressure of 0.7 mbar, using a liquid delivery approach for precursor dosage. On Cu seed layers, continuous films were obtained at low deposition rates (0.5 to 1 nm/min). At temperatures above 320°C, hole formation in the Cu films was observed. Deposition on TiN led to the formation of single copper particles and etching of the TiN, whereas isolating aluminum oxyfluoride was formed after deposition on Al(Si)/W. It is concluded that the formation of CF₃ radicals during decarboxylation has a negative effect on the deposition results. Furthermore, the precursor chemistry needs to be improved for a higher volatility of the complex.