Elucidare

Metal-Insulator-Metal Capacitor for Analog Mixed-Signal Applications

Title: Metal-Insulator-Metal Capacitor for Analog Mixed-Signal Applications
 

 
Start date: August 2011
Client: Tyndall National Institute
Investigator Dr David Nugent
david.nugent@elucidare.co.uk

 


Introduction

Tyndall National Institute is developing a MIM Capacitor technology with the main objective being to produce a high-k, low-leakage, high-breakdown voltage insulator material for a metal-insulator-metal (MIM) capacitor. The inventors are Dr Scott Monaghan and Dr Ian Povey, who recently won UCC’s Invention of the Year competition 2010 with the technology.


Proposition

As microelectronics journeys towards nanoelectronics, the miniaturisation of analog circuitry (and components thereof) is unable to keep pace with that of its digital counterpart. Within this, it is the capacitor miniaturisation (while maintaining electronic performance) which is the major industry bottleneck. MIM capacitors are key elements of analog circuitry components such as analog-to-digital converters (ADCs) and digital-to-analog converters (DACs), among others.

Much worldwide research in this field is focussed on the insulator, with many new materials under investigation. Most commercial devices use silicon oxides or nitrides as the insulator in a MIM capacitor, and these have k values of typically 4-5. There are numerous materials with far higher k values, and these are regularly appearing in technical publications. However, these invariably also have associated leakage, stability and reliability problems which are so great as to disable their use in the MIM capacitor application.

One illustration of the challenges encountered in contemporary MIM capacitor designs is the compromise between capacitor density and capacitor linearity. Whilst density can be increased (desirable) using thinner dielectric layers, this causes a corresponding deterioration in linearity (undesirable). Consequently it has not been possible to design MIM capacitors that meet ITRS requirements in terms of both density (>5 fF/um2) and linearity (<100ppm/V2).

By a judicious combination of precursors and deposition techniques, Tyndall researchers have developed a novel dielectric composition that enables – for the first time – capacitor density to be increased without a corresponding deterioration in linearity.

 


Source: Based on graphic in High-ĸ Metal-insulator-metal (MIM) Capacitors for RF/mixed-signal IC Applications, PhD Thesis. Sun Jung Kim, National University of Singapore.

 

Additional benefits of the Tyndall technology include:

Standard deposition process: Tyndall methodology is based on conventional atomic layer deposition (ALD) techniques.

Commercial precursors: Commercially available precursors are used.

Ultra-low leakage current: Test results have shown ultra-low leakage current densities compliant with the requirements of RF CMOS applications.

High breakdown voltages: k-values comparable to hafnium oxides have been demonstrated but with significantly higher breakdown voltages (>90 volts).

Scalable: Can be used to form thick (EOT>30nm) dielectric layers for high-voltage CMOS and thin (EOT<5 nm) dielectric layers for DRAM applications.

High-temperature robustness: The MIM capacitor can withstand CMOS process temperatures in excess of 1000°C. This will enable MIM formation during the front-end of line process, thereby eliminating certain lithography masks whilst reducing unwanted load resistance.

 


Documents available for download

Further details about the dielectric material and associated deposition process shall be posted in due course.