Ted Guo

Nucleation and growth of CVD Al on different types of TiN

Abstract The deposition of Al by CVD on top of a Ti/TiN liner is a very promising approach for filling gaps with a high aspect ratio. In this work we have studied the nucleation and growth of CVD Al and its bulk properties as a function of the type of TiN used. For a given type of TiN we deposited films over a wide range of thickness (5–300 nm). The depositions were carried out in a cluster tool (Endura™) where in some cases we deliberately allowed for a vacuum break prior to the Al deposition. Auger electron spectroscopy was used to measure the amount of Al deposited, thus yielding the kinetics of the Al growth. X-ray diffraction was used to determine the preferred orientation of the Al, which is important for electromigration resistance. The microstructure was studied by scanning and transmission electron microscopy and atomic force microscopy. We found that air exposure affects the nucleation, the rate of growth at the early stages, and the resultant morphology. A correlation exists between the nucleation stages of the growth and the bulk properties.

CVD AL for advanced interconnect applications

Abstract A method for depositing low resistivity, high purity aluminum films by Chemical Vapor Deposition (CVD) is introduced. Pyrolysis of Dimethyl Aluminum Hydride (DMAH) using either H2 or an inert gas as a carrier is shown to yield films with less than 0.01 at.% carbon and oxygen and resistivities of 3.0 μΩcm. The kinetics are exponentially temperature dependent with Eact ∼ 0.5 eV independent of substrate. Introduction of some possible byproducts indicate that the deposition mechanism may be self reduction of DMAH. The morphology, wettability, and step coverage of the films are shown to depend strongly on the nature of the substrate and how it is integrated with the CVD Al process. Clustering of CVD Al with the deposition of the underlying liner is shown to be critical in achieving the highest quality films. Smooth, highly 〈111〉 oriented films with excellent reflectivity may be obtained. Some methods for Cu doping are discussed including a novel form of in situ deposition. Complete via fill is obtained with blanket depositions with one or two grains filling the vias in most cases. Vias as high as 3.5:1 aspect ratio are filled—sometimes with a single grain of Al. Electrical results indicate that the via resistances and electromigration resistance of the Al plugs are excellent.

Texture and surface morphology improvement of Al by two-stage chemical vapor deposition and its integration in an Al plug-interconnect scheme for sub 0.25 μm metallization

A two-stage deposition with successive seed and bulk deposition steps was developed to improve the morphology and texture of chemical vapor deposited (CVD) aluminum on titanium. Dimethylaluminumhydride (DMAH) was used as the precursor. Typically, CVD Al deposited using a single deposition stage showed highly granular structure with surface “defects” resulting in films that become rough with increase in thickness creating integration problems with photolithography and etch. Here, a two-stage deposition process for CVD Al is described that significantly improves the morphology and texture of Al on titanium. In this process, the wafer surface is preconditioned with a short burst of DMAH before stabilizing gas flows or pressure. Such a treatment in the very first step results in a seed layer upon which proceeds the bulk film deposition in a subsequent step after stabilizing pressure, gas flows and equilibrating temperature. The two-stage deposition resulted in reflectivity improvement of CVD Al on Ti from ⩽ 1...

A low temperature integrated aluminum metallization technology for ULSI devices

Abstract An integrated aluminum metallization process (Cool Al technology) was successfully applied to fabricate device wafers for the 0.25-μm technology. This new technology integrates CVD and PVD aluminum thin film deposition processes into a high vacuum cluster tool, the applied materials’ Endura, and is capable of reliable contact and via fills of high aspect ratio (>8:1) structures at low temperatures, typically around 330–400°C. Two different Cool Al integration sequences employing CVD TiN and Ti as liners were used to process device wafers with 0.3 and 0.4×1.2μm via structures. The fill performance and electrical and reliability characteristics of the devices were evaluated. Void-free fills of all via structures were achieved. In comparison with a standard W-plug process, both Cool Al splits show more than five times reduction in via resistance. The two Cool Al sequences yielded excellent electromigration (EM) reliability, equivalent or better than a standard W-plug process. Interestingly, the two Cool Al splits, with very different aluminum crystal textures, resulted in similar EM performance.