Combined lifetime killing by platinum and fast light ions in silicon power diode : thermal stability of introduced radiation defects
The influence of combined lifetime killing by platinum in-diffusion and fast light ion irradiation on generation and stability of introduced radiation defects was investigated in the low-doped n-type float-zone oxygen rich silicon forming the base of power pnn diodes. Different concentrations of platinum substitutionals were introduced by platinum implantation and subsequent annealing at temperatures ranging from 725 to 900°C. Diodes were then irradiated with 1.8 MeV protons or 5 MeV alphas to fluences ranging from 5x10 to 1x10 cm. The influence of platinum doping on introduction rates of dominant radiation defects and their thermal stability during subsequent isochronal annealing was investigated by deep-level transient spectroscopy. Results show that the presence of platinum atoms significantly influences introduction rates of dominant recombination centers introduced both by hydrogen and helium irradiation (vacancy-oxygen pairs, divacancies and VOH complexes). Simultaneously, temperature stability of vacancy-oxygen pairs and divacancies decreases of up to 150°C. In both cases, these effects are proportional to platinum concentration introduced into diodes.
On the behavior of interaction of a Pt‐related center with radiation‐induced defects and the trace platinum detection
The interaction of platinum (Pt) with electron irradiation‐induced defects has been observed. Platinum in silicon increases irradiation‐induced defects remarkably, especially the A center, and lowers the annealing temperature to 220 °C for the A center and to 140 °C for the divacancy and E center. The level Ea (0.23) in the Pt‐doped silicon is the Pt(−/0) level, an acceptor like the A center. A method is suggested for activating the platinum in silicon with low‐energy electron irradiation and subsequent thermal annealing and detecting it by deep level transient spectroscopy (DLTS).
Bevel RIE application to reduce defectivity in copper BEOL processing
Bevel etch used during wafer fabrication for semiconductor devices is discussed. In this case, the bevel etch process was utilized in middle of the line processing (MOL) to reduce back end of line (BEOL) defectivity. Tungsten and titanium nitride films, from the formation of contacts to the transistors, extend into the bevel region of the wafer and have been shown to initiate arcing. This can spread foreign material defects on the front side of the wafer in various BEOL post processing steps including subsequent reactive ion etching, SEM metrology and film depositions. The bevel etch tool confines a plasma etch to the outer edge of the front side of the wafer (which can be individually adjusted) and can remove dielectric, organic and Ti/TiN/W films using a fluorine based chemistry.