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Higher k hafnium oxide material for Nano-Electronic Devices (k > 30)

The material, a new form of hafnium oxide, was developed by Dr Andrew Flewitt’s research group in the Department of Engineering. The material provides exceptionally high dielectric constant compared with currently existing forms of hafnium oxide, which is already a key material in the electronics industry.

Metal oxides are used in a wide variety of applications. Normally, they are produced on substrates by sputtering, a process by which some of the atoms of an electrode are ejected as a result of bombardment by heavy positive ions. One of the problems when attempting to make high-quality electronic materials through sputtering, however, is the difficulty in precisely controlling the energetics of the deposition process, and hence the material properties such as defect density.

In order to enable much greater control of the material properties, Dr Flewitt and his team began using a novel deposition technology to promote plasma sputtering. The technology, known as HiTUS (High Target Utilisation Sputtering), was developed by a UK-based company, Plasma Quest Ltd. One of the first materials that the Cambridge team looked at using HiTUS was hafnium oxide.

Hafnium oxide is an electrical insulator which is used in optical coatings, capacitors and transistors, among other applications. Many companies are currently using hafnium oxide to replace silicon dioxide in transistors, due to its high ratio of electric displacement in a medium to the intensity of the electric field producing it, known as a dielectric constant. The higher the dielectric constant of a material, the higher its capacitance - the ability to store an electric charge.

Hafnium oxide forms in different crystalline and polycrystalline structures: monoclinic, cubic and orthorhombic. However, an amorphous form is preferable to polycrystalline forms due to the absence of grain boundaries, the point at which two crystals in a polycrystalline material meet. Grain boundaries act as conduction paths through thin films of the material. They not only reduce the resistivity, but lead to a non-uniformity in conductivity over a large area, which itself leads to spatial non-uniformity in device performance However, until now amorphous hafnium oxide has had a relatively low dielectric constant of around 20.The form of hafnium oxide developed by Dr Flewitt has a dielectric constant higher than 30.

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Higher k hafnium oxide material for Nano-Electronic Devices (k > 30)

The material, a new form of hafnium oxide, was developed by Dr Andrew Flewitt’s research...