Monday, June 24, 2019

RASIRC Peroxidizer – the preferred way for stable on demand delivery of highly reactive H2O2-ALD precursor

Thin film titanium dioxide (TiO2) is one of the necessary materials with numerous uses in the electronics, semiconductor, and display industry. TiO2 is a high-k material (k>90) and can, therefore, be used stand-alone or laminated with other high-k metal oxides (e.g., Al2O3, HfO2, ZrO2, SrO) for capacitor application in DRAM or embedded decoupling capacitors or energy storage. Due to excellent water vapor penetration properties, TiO2 is often employed as a barrier layer together with Al2O3 for very thin barrier systems on flexible electronics and display technologies. Besides these applications, there is a growing interest also in battery applications and coating medical implants and electronic devices with ALD TiO2 – even encapsulation of medicament particulates (ref. Nanexa AB, LINK).

One of the critical TiO2 thermal ALD processes is employing titanium isopropoxide (TTIP) and water as precursors, allowing deposition of high-quality barrier well below 200 °C. However, the TTIP low-temperature ALD processes suffer from very low GPS (<0.5 Å), which is terrible for throughput.

The ALD process window showing GPC (left) and refractive index (right) as a function of process temperature for H2O, O3 and H2O2 TDMAT based ALD of TiO2.

Another commonly used titanium precursor is TDMAT with H2O or O3 as co-reactants resulting in relatively higher GPC in the temperature range 100 to 200 °C, commonly used for flexible devices.

Ozone is typically losing its oxidation power at the lowest temperature range, at 100 °C and below which is needed for processing on e.g., OLED display devices. Therefore most ALD processes for metal oxides use H2O as co-reactant for low temperature.

Hydrogen peroxide (H2O2), which has a higher oxidation potential than H2O has shown many promising results in research and previous studies by RASIRC (Reference "Cheating Raoult’s Law"). In a most recent study by RASIRC and TNSC, results showcase clearly that the TDMAT ALD-TiO2 process is improving compared to H2O and O3 based processes:
  • Higher GPC 
  • Denser layers as indicated by the higher index of refraction, especially at low temperature (100 °C) Much lower wet etch rate (WER) 
  • Improved purity – less nitrogen and carbon incorporation, which is the driver for low WER.

RASIRC, has a mature delivery method for concentrated H2O2 – The Peroxidizer, which is an integrated source and delivery unit that can be facilitated as a stand-alone H2O2 delivery unit or integrated into the ALD tool gas and precursor delivery system. 

The Peroxidizer delivers hydrogen peroxide gas concentrations from 12,500 to more than 50,000 ppm depending on flow rate. Carrier gas flow rates can range from 5 to 20slm supplying into both vacuum and atmospheric pressures. The Peroxidizer adjusts the temperature to achieve the desired output.

The RASIRC Peroxidizer provides a safe, reliable way to deliver high-concentration H2O2 gas into ALD, annealing, dry surface preparation and cleaning processes.

The three key advantages of the Peroxidizer delivery technology are:

Higher concentration - The Peroxidizer delivers 10x concentration of hydrogen peroxide gas at a given temperature and delivers droplet-free gas at temperatures as low as 80 °C. The Peroxidizer delivers up to 5% hydrogen peroxide gas by volume from 30% hydrogen peroxide liquid solution.

Stronger Oxidant - Hydrogen peroxide gas readily converts to highly reactive OH radicals, creating a high-density ALD nucleation and faster reactions with precursors. Oxygen plasma can penetrate below the interface layer, damaging the bottom electrode and surface structures. Plasma cannot reach the bottom of deep structures as it requires line-of-sight, so coatings may be non-uniform, favoring the top of the structure.

Lower Temperature - High concentration hydrogen peroxide gas delivered by the Peroxidizer creates a dense hydroxylated layer at a lower operating temperature than other oxidants. To achieve the same level of reactivity, water requires higher process temperatures that are not compatible with new materials.

Finally, The Peroxider always beat the Bubbler and the Vaporizer because it enables on-demand stable flow control and no particle generation due to liquid micro-droplet formation. RASIRC will be presenting results about the Peroxidizer at the upcoming EuroCVD22/Baltic ALD 16 conference in Luxemburg (LINK).

More information
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San Diego, CA 92126


RASIRC products generate and deliver gas to fabrication processes. RASIRC technology delivers water vapor, hydrogen peroxide and hydrazine gas in controlled, repeatable concentrations.

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