Nanofabrication service

Plasma Enhanced Chemical Vapour Deposition (PECVD)

PECVD is a technique for depositing a variety of materials that are commonly used in the semiconductor industry. The reactants are gases and energy is provided partly by heating the substrate to a high temperature (typically 400°C or below) and partly by the plasma.

We offer a number of PECVD services:

Amorphous silicon deposition

This system is used to deposit amorphous and polycrystalline silicon, germanium and silicon-germanium. The material can be doped either n-type (phosphorus) or p-type (boron) during deposition (i.e. in-situ doping).

A deposition temperature up to 650°C can be used, allowing the silicon to be deposited as polycrystalline (~600°C and above) or amorphous (<540°C) material. For silicon-germanium slightly lower temperatures can be used and for germanium slightly lower still.

The deposition rate for amorphous silicon is >25 nm/min and for polysilicon is >40 nm/min. The system can accept wafers up to 200 mm in diameter and can perform depositions on small pieces of silicon placed on a larger wafer.

Nitride and oxide deposition

This system is used to deposit silicon dioxide, silicon nitride and rare earth doped oxides.

The machine has two liquid precursors, one for TEOS and one for rare earth doped oxides. For high vapour pressure liquid sources, argon is bubbled through the liquid precursor to provide a vapour for the PECVD, whereas for low vapour pressure liquid sources, the bottle is open to the deposition chamber.

TEOS is used to deposit silicon dioxide at 350-400°C and has good planarising properties for metallisation.

The system has a low frequency and high frequency (RF) plasma source and the two can be combined to deposit layers with low stress. For TEOS the deposition rate is >40 nm/min. Silicon dioxide can also be deposited using SiH4/N2O/N2 at 300°C with a deposition rate of >40 nm/min. Silicon nitride is deposited using SiH4/NH3/N2 at 300°C with a deposition rate of >10 nm/.min.

The system can accept wafers up to 200 mm in diameter and can perform depositions on small pieces of silicon placed on a larger wafer.

Nanotube and wire deposition

This system is used to deposit carbon nanotubes and silicon, silicon-germanium and germanium nanowires. Catalyst nanoparticles are needed to initiate nanotube or wire growth, which usually takes the form of metal nanoparticles generated on the surface of the wafer prior to deposition.

If the nanoparticles are omitted, the system can be used to produce silicon, silicon-germanium, germanium and SiC films.

The nanowires can be doped either n-type (phosphorus) or p-type (boron) during deposition (i.e. in-situ doping). A deposition temperature up to 1000°C can be used, allowing the silicon to be deposited as polycrystalline (~600°C and above) or amorphous (<540°C) material. For silicon-germanium slightly lower temperatures can be used and for germanium, slightly lower still.

The system can accept wafers up to 200 mm in diameter and can perform depositions on small pieces of silicon placed on a larger wafer.

Atomic layer deposition

This system is equipped with four liquid precursor modules and hence can deposit up to four different ALD layers in the same run.

It can be used to deposit HfO2, TiN, ZnO and Al2O3 using TEMAH, TiCl4, DEZ and TMA precursors respectively. The deposition rate is typically between 0.2 and 1.5 angstrom per cycle.

The system can accept wafers up to 200 mm in diameter and can do depositions on small pieces of silicon placed on a larger wafer.