Brief Introduction

Topic

The topic of our project is modelling electrical properties of thin high-k gate stacks.

This project focus on researching the electrical properties of HfSiO (with 50% doping density), which is a high-k stack produced by MOCVD (the method of metal organic vapour chemical deposition). The final product is the different parameters that were calculated from the experimental CV curve, including k value, equivalent oxide thickness (EOT), mid gap voltage, mid gap capacitance, flat band voltage, flat band capacitance, fixed oxide charge. The field effect transistor (FET) was invented in 1951 by scientists such as Shockley from the bell laboratories with the achievement of controlled switching on and off under an external electric field. Up to now, the FET can still be seen everywhere in the mobile phones and personal computers.

There are two types of FET, one is J-FET, the other is metal-oxide-semiconductor FET, the latter has become the first choice because of the property of simple process, low power consumption and easy integrating.

The MOS structure includes the substrate which was made of the silicon semiconductor material. On the substrate, there are three electrodes which were called the gate, drain and source. The gate, source and drain electrode were insulated separately. The oxide was laid between the gate and the substrate.  There are two pn junctions between the drain and source.

There will be current between the source and the drain when enough voltage is applied between the gate and the substrate.  If you think of the current as the water, the gate is the milldam.

In the past few decades, the semiconductor industry has made rapid development, creating huge economic benefits and driven society to the information era. 

The application of CMOS covers almost all modern mobile phone and computer processors. It’s of great importance to to discover how to improve the performance and make the size even smaller. Is there any rules that can be applied to guide the future development?  The answer is yes. It’s called the Moore’s law.

Moore's Law

As Moore's law told us that the number of transistors on an integrated circuit double every 18 months with the performance would also be doubled. 

This golden rule has guided the semiconductor industry for many decades. In keeping with Moore's law, the size of the transistors must be cut in half every two years. The existing processes have reduced the components of a transistor to the thickness of a few molecules and atoms, the material that makes up a semiconductor has reached the limits of its physical and electrical properties.

Unfortunately, it was the heart of the integrated circuit, the gate oxide that makes up the transistor -- the gate dielectric – which has reached this limit first.

Will Moore’s law be terminated ever since? The answer is no. From the midterm of the 90s, the technical elites from intel tried to break the habitual thinking way, by giving up the existing material which has been used for approximately 40 years. Through the untiring effort, the revolutionary high-k materials and metal gate appeared, which are still popular today.