R. A Donaton

Limitation of HF‐Based Chemistry for Deep‐Submicron Contact Hole Cleaning on Silicides

The limitation of the use of HF-based chemistry for the cleaning of submicron high aspect ratio features is discussed. In this paper we describe the post-dry-etch cleaning of contact holes on TiSi 2 . This cleaning process is a combination of the use O oxidizing agents to remove residues consisting of fluorinated polymers and titanium fluorides, and HF-last cleaning to remove SiO 2 on TiSi 2 . The HF-last cleaning is necessary to reduce the contact resistance. Two issues are pointed out: a very narrow process window for the HF etch time, and a strong hole size dependence of the contact resistance. These issues are not seen when soft sputter etching is used instead of HF-last cleaning. Concerning the narrow process window, the contact resistance decreases with increasing HF treatment time but increases again after passing through a minimum value. The kinetic study of TiSi 2 etching shows that a preferential etching of the C49 phase takes place during an HF treatment. As a result, the TiSi 2 surface becomes porous, which is thought to decrease the contact area. The hole size dependence is discussed in view O transport of chemical species in the contact hole. It is shown that the size dependence can be explained by assuming an abnormally small diffusion coefficient. HF-SiO 2 chemistry at the sidewall surface of narrow hydrophilic features can explain this abnormally small diffusivity.

Kinetics and Mechanism of the Etching of CoSi2 in HF‐based Solutions

The wet etching behavior of CoSi 2 films in HF-based solutions is investigated for a wide range of experimental conditions. It is established that the etching rate of CoSi 2 depends on the concentrations of H + ions and on the initial concentration of HF ([HF],). Interaction of H + and HF with the CoSi 2 occurs in the adsorption layer. The concentration of adsorbed particles is described by the equation of the Freundlich adsorption isotherm. The kinetic equation of the etching rate is R = k R Θ H .Θ HF , where k R 2.5. 10 7 exp (-10500/RT) nm/s (0.416 at 293 K), Θ H . [H + ] 0.135 and Θ HF [HF] 1 0.310 . It is shown that the induction period increases in the etching process of CoSi 2 in diluted HF 1 which is attributed to the presence of a thin surface layer on top of the CoSi 2 .

New process for the controlled formation of ultrathin PtSi films for infrared detector applications

A simple method for controlling the thickness of PtSi for infrared detectors is presented. Thicknesses of PtSi in the range of 2 - 5 nm can be controlled via the reaction kinetics of the silicidation. Compared to conventional furnace anneal, the thickness and homogeneity of the resulting PtSi-layers are independent of the deposited Pt-thickness. Superior uniformity, lower continuous film thicknesses of the PtSi-layers, and smoother PtSi/Si-interfaces than possible by conventional furnace anneal are achieved by applying this technique.

Ion‐Induced Amorphization and Regrowth of C49 and C54 TiSi2

C49 and C54 TiSi 2 films were implanted with 200 keV 5 × 10 14 cm -2 xenon (Xe + ) ions at - 185°C, and the regrowth of C49 and C54 TiSi 2 grains was studied following thermal annealing. The low-temperature Xe + implant resulted in partial amorphization of the C54 TiSi 2 layer, as evidenced by transmission electron microscopy. Upon annealing at temperatures below ∼600°C, a double-layer structure was obtained consisting of a C49 TiSi 2 layer on top of C54 TiSi 2 . For an equivalent Xe + implant in C49 TiSi 2 , the C49-C54 transition temperature was delayed as compared with the phase transition for a nonimplanted C49 TiSi 2 film. Following room-temperature implantation of C49 TiSi 2 with 100 keV germanium (Ge + ) ions at various doses ( 1 × 10 14 to 1 × 10 16 cm -2 ), or low doses of 70 keV Xe + (1 × 10 12 and 1 × 10 13 cm -2 ), no reduction in the C49-C54 transition temperature was observed upon thermal annealing. According to our results, defects caused by Xe + or Ge + ion implantation of C49 TiSi 2 do not promote formation of C54 TiSi 2 .

CoSi2/Si1-xGex interfaces for Schottky barrier infrared detectors with extended detection regime

A CoSi2/strained-Si1-xGex-Schottky barrier detector is proposed for detection of infrared radiation in the 3 - 5 micrometers window. It could be a substitute for PtSi/Si-Schottky barrier detectors, which have already been integrated with readout electronics, but which imply the disadvantage of having the metal Pt in the line as a possible source of contamination. A silicidation study on strained Si1-xGex-layers with sacrificial Si-layers on top has been carried out to realize CoSi2/strained-Si1-xGex-interfaces, which will form the heart of the detector. The possibilities to integrate this detector with readout electronics are critically reviewed. First CoSi2/Si1-xGex-detectors have been processed which yield barrier heights as low as 229 meV.