Impact of nanosecond laser energy density on the C40-TiSi2 formation and C54-TiSi2 transformation temperature

Abstract

The formation of Ti based contacts in new image sensors CMOS technologies is limited by the requirement of low thermal budget. The objectives for these new 3D-technologies are to promote ohmic, low resistance, repeatable and reliable contacts by keeping the process temperature as low as possible. In this work, UV-nanosecond laser annealing were performed before classical rapid thermal annealing (RTA) to promote the formation at lower RTA temperatures of the low resistivity C54-TiSi2 phase. The laser energy density was varied from 0.30 to 1.00 J/cm² with 3 pulses in order to form the C40-TiSi2 phase and finally to obtain the C54-TiSi2 phase by a subsequent RTA at low temperature. The formed Ti-silicides were characterized by four-point probe measurements, X-Ray Diffraction, Transmission Electron Microscopy and Atom Probe Tomography. A threshold in the laser energy density for the formation of the C40-TiSi2 is observed at an energy density of 0.85 J/cm² for the targeted TiN/Ti stack on blanket wafers. The C40-TiSi2 formation by laser annealing prior to RTA enables to reduce the formation temperature of the C54-TiSi2 phase by 150°C in comparison to a single RTA applied after the Ti/TiN deposition. This specific phase sequence is only observed for a laser energy density close to 0.85 J/cm². At higher energy densities, the presence of C49-TiSi2 or a mix of C49-TiSi2 and C54-TiSi2 is observed. The underlying mechanisms for the phase sequence and formation are discussed in details.

Te and Ge solid-state reaction: comparison between the 2D and 3D growth of α-GeTe

“…It is usual to observe a 3 to 5 nm-thick amorphous or crystalline intermixing layer between a metal and the Si or Ge substrate after sputtering. 35–38 This layer acts usually as the initial stage of the 2D growth of silicides or germanides. 47 During annealing (Fig.…”

“…When a metal is deposited on a Ge or Si substrate, it is usual to observe a 3–5 nm-thick, amorphous or crystalline, intermixing layer. 35–38 For germanides, the growth usually follows a parabolic law versus time. 39–41 This means that the growth is limited by atomic diffusion according to the linear-parabolic model.…”

Influence of Si surface preparation on CoSi2 formation and agglomeration

“…Then, fluorine salts are sublimated by bringing the wafer surface closer to a showerhead heated at 180 °C (Eq. 5) [13,41].…”