Electrode metallization for high permittivity oxide RF thin film capacitors

Tommi Riekkinen (Corresponding Author), Jyrki Molarius, Markku Ylilammi

Research output: Contribution to journalArticleScientificpeer-review

Abstract

High permittivity oxide thin film capacitors for RF components should be integrated on the chip to form a complete miniaturized module, with other semiconductor or thin film components such as inductors, isolation capacitors, and bias resistors. The quality factor (Q) values of the RF capacitors are strongly dependent on electrode conductivity. Alas the best conducting metals (e.g. Ag, Cu, Al) are not thermodynamically stable during deposition of high permittivity oxide films with high temperature and oxygen atmosphere. On the other hand, refractory metals (e.g. Mo, W) endure high temperatures, but are prone to oxidation. Therefore, a diffusion barrier is a prerequisite for integrating refractory metals to achieve a stable electrode structure.

In this study both non-reactive and sacrificial diffusion barriers with Mo metallization were investigated on Si/SiO2 substrates. Also, noble metals (Au and Pt) as oxidation resistant materials were examined. Annealing at 650 °C was performed to the electrode stacks in an open-end air furnace and in vacuum with protective gas.

The chemically inert materials Au and Pt failed to endure the high annealing temperature. Au became extremely rough and cracks appeared. Massive grain growth and adhesion loss occurred with Pt film. Mo electrode withstood the oxidizing ambient conditions with a sacrificial Si or Al–Ti diffusion barrier. Moderate increase in surface roughness was observed after the annealing due to oxidation. Also, thermally stable AlN, Si3N4, and SiO2 diffusion barriers were able to block oxygen from the Mo electrode.
Original languageEnglish
Pages (from-to)2983-2987
JournalJournal of the European Ceramic Society
Volume27
Issue number8-9
DOIs
Publication statusPublished - 2007
MoE publication typeA1 Journal article-refereed

Fingerprint

Metallizing
Diffusion barriers
Oxides
Permittivity
Electrodes
Refractory metals
Annealing
Oxidation
Oxide films
Capacitors
Oxygen
Precious metals
Grain growth
Resistors
Temperature
Furnaces
Adhesion
Gases
Surface roughness
Metals

Keywords

  • films
  • surfaces
  • diffusion
  • capacitors
  • electrodes
  • oxidation resistance
  • oxidation
  • diffusion barriers

Cite this

Riekkinen, Tommi ; Molarius, Jyrki ; Ylilammi, Markku. / Electrode metallization for high permittivity oxide RF thin film capacitors. In: Journal of the European Ceramic Society. 2007 ; Vol. 27, No. 8-9. pp. 2983-2987.
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Electrode metallization for high permittivity oxide RF thin film capacitors. / Riekkinen, Tommi (Corresponding Author); Molarius, Jyrki; Ylilammi, Markku.

In: Journal of the European Ceramic Society, Vol. 27, No. 8-9, 2007, p. 2983-2987.

Research output: Contribution to journalArticleScientificpeer-review

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N2 - High permittivity oxide thin film capacitors for RF components should be integrated on the chip to form a complete miniaturized module, with other semiconductor or thin film components such as inductors, isolation capacitors, and bias resistors. The quality factor (Q) values of the RF capacitors are strongly dependent on electrode conductivity. Alas the best conducting metals (e.g. Ag, Cu, Al) are not thermodynamically stable during deposition of high permittivity oxide films with high temperature and oxygen atmosphere. On the other hand, refractory metals (e.g. Mo, W) endure high temperatures, but are prone to oxidation. Therefore, a diffusion barrier is a prerequisite for integrating refractory metals to achieve a stable electrode structure.In this study both non-reactive and sacrificial diffusion barriers with Mo metallization were investigated on Si/SiO2 substrates. Also, noble metals (Au and Pt) as oxidation resistant materials were examined. Annealing at 650 °C was performed to the electrode stacks in an open-end air furnace and in vacuum with protective gas.The chemically inert materials Au and Pt failed to endure the high annealing temperature. Au became extremely rough and cracks appeared. Massive grain growth and adhesion loss occurred with Pt film. Mo electrode withstood the oxidizing ambient conditions with a sacrificial Si or Al–Ti diffusion barrier. Moderate increase in surface roughness was observed after the annealing due to oxidation. Also, thermally stable AlN, Si3N4, and SiO2 diffusion barriers were able to block oxygen from the Mo electrode.

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