Stress control in reactively sputtered AlN and TiN films

Abstract

Al and Ti planar magnetron targets have been sputtered in Ar/N2 mixtures to deposit AlN and TiN films on unheated substrates; rf and dc discharges were used for the AlN and TiN deposition, respectively. The N2 flow was always sufficient to produce a nitrided target layer and x-ray diffraction showed single-phase films of AlN and TiN1.2. In N2 discharges, the AlN film stress varied from −19 GPa (compressive) to +2.5 GPa (tensile) as the pressure increased from 0.2 to 5 Pa. Intrinsic tensile stress in reactively sputtered compound films has not previously been reported. A similar change was observed in the stress of TiN films. Zero-stress AlN and TiN films were obtained at ∼1 Pa for the sputtering conditions used. The rapid decrease in compressive stress with increasing pressure is associated with a rapid decrease in both target voltage (for constant applied power) and deposition rate. Calorimetry measurements of the power flux at the substrates show an increase with pressure. With increasing Ar content, at a constant pressure, the compressive stress decreases although the target voltage and deposition rate increase; the substrate power flux decreases. The surface coverage of N on the targets increases with increasing N2 pressure because the N+2 flux increases. The compressive stress is probably due to bombardment of the film by neutral N atoms reflected with high energy from the targets. The decrease in deposition rates and increase in substrate power density may result from increased sputtering rates of N atoms from the target with a consequent decrease in metal atom sputtering.

Passivation of InP heterojunction bipolar transistors by strain controlled plasma assisted electron beam evaporated hafnium oxide

“…12) was remarkably low in the present HfO 2 film and remained unchanged when exposed to the atmosphere following deposition. It is commonly agreed that for most applications, the residual stress has to be minimized because it alters the energy band structure and can influence the device characteristics.…”

Thermal reliability analysis of non-gate dielectric film in IEC-GCT

“…But PECVD is rarely used in GTO process as larger cost. AlN film, not reported in GTO process, can implement by sputtering in nitrogen atmosphere at some condition [8][9][10].…”

Effect of particle bombardment on the orientation and the residual stress of sputtered AlN films for SAW devices

“…According to [3], [4], atomic recoil and ionic implantation are the main mechanisms responsible for the generation of compressive stress in sputtered layers. In this section we will investigate the dependence of the residual stress on the deposition parameters.…”

“…This energy can be provided by heating the substrate [1] and by bombarding the surface of the film with energetic particles from the plasma [2]. However, the energetic bombardment of the substrate may have negative consequences, such as the formation of crystal defects that would induce high residual stress in the film [3], [4]. Sputtering at low pressure is the most common way to enhance the ionic bombardment of the growing films and, therefore, to induce the growth of c-axis oriented films.…”