Delivering high concentration hydrogen peroxide gas
For the first time, process engineers can use hydrogen peroxide gas at high concentration for next generation semiconductor fabrication. H2O2 gas is a strong oxidant ideally suited for ALD, annealing, cleaning and other processes involving new materials and 3D architectures. Superior to older technologies, the Peroxidizer delivers 10x higher concentration of H2O2 gas at a given temperature and delivers droplet-free gas at temperatures as low as 80C.
Meeting the Demands of ALD for Next Generation Semiconductor Processes
H2O2 is a better choice when working with new materials and device architectures. High concentration H2O2 gas delivered by the Peroxidizer creates a dense hydroxylated layer at a lower operating temperature than other oxidants. The Peroxidizer delivers up to 5% H2O2 gas by volume from 30% H2O2 liquid solution.
Ozone and oxygen plasma are too aggressive. These oxidants can penetrate below the interface layer, damage the bottom electrode and damage surface structures. They have higher steric hindrance, causing a lower density interface layer. And plasma cannot penetrate high aspect ratio structures, so coatings may be non-uniform.
H2O2 gas is also superior to water. To achieve the same level of reactivity, water requires higher process temperatures that are not compatible with new materials. Like ozone and oxygen, water has higher steric hindrance, so interface layers are not as dense.
New materials and architectures are more temperature sensitive than their predecessors, forcing lower thermal budgets. The higher reactivity at lower temperature increases the range of precursors available to process engineers.
The Peroxidizer delivers H2O2 gas at a range of concentrations, always with a 4:1 molar ratio of water to H2O2. This low ratio of water to H2O2 significantly reduces process interference from water vapor.
Enabling Next Generation Gap Fill Annealing
High speed and low temperature are imperatives for next generation annealing. H2O2 gas has higher solubility than most other oxidants. Just as with ALD, plasma and ozone are too aggressive and can damage structures, whereas water is not reactive enough, requires higher temperatures and incurs long process times. The Peroxidizer delivers H2O2 at lower temperatures than other technologies, reducing impact on the thermal budget.
In Situ Surface Preparation and Cleaning
The Peroxidizer enables in situ cleaning and surface preparation. This dry processing eliminates the risk of contamination during transfers required by wet processing. The dry process also requires less chemicals and eliminates drying steps.
H2O2 gas is an excellent cleaning and surface preparation agent. Organic hydrocarbons are easily oxidized, enabling wet or dry removal. New materials and 3D architectures are cleaned without damage.
Key Innovations in Hydrogen Peroxide Delivery
H2O2 gas has never before been delivered at a stable, high concentration. Two key breakthroughs were required to achieve this milestone.
First, Raoult’s Law had to be overcome. Raoult’s Law says that when two-component solutions like H2O2 are vaporized, the individual components will vaporize at different rates. Because water vaporizes significantly faster than H2O2, the generated gas will be mostly water vapor.
Early experimentation in converting H2O2 liquid to gas did not account for the effect of Raoult’s Law. While many scientists believed that H2O2 gas was generated at 4:1 molar ratio, in fact the gas was close to 100:1 or more, and ineffective for the process.
The Peroxidizer is designed with Raoult’s Law in mind, and has key technology to ensure that the expected molar ratio is in fact delivered to process. Initial RASIRC systems developed with this technology achieved stable delivery of H2O2 gas at a 50:1 molar ratio of water to H2O2.
The second breakthrough was in concentrating the H2O2 gas prior to delivery to process. H2O2 gas is concentrated within the Peroxidizer until the gas in the headspace reaches 4:1 molar ratio of water to H2O2. Special technology ensures that once the headspace gas reaches 4:1 all gas delivered to process remains at that ratio, for any concentration from 12,500 to 50,000ppm or more.
Better than Bubblers and Flash Vaporizers
The Peroxidizer outperforms other oxidants and other technologies for H2O2 delivery. Bubblers require carrier gas to bubble through liquid source H2O2. To match the output of the Peroxidizer, higher temperatures are needed.
Bubblers cannot overcome Raoult’s Law so output is constantly changing. Initial concentration is frequently less than 300 ppm of H2O2 along with about 25,000 ppm of water. However, as the liquid in the bubbler is consumed, the water content is reduced and the H2O2 concentration increases until explosive concentration is reached. The differential vaporization rates cause the liquid solution to concentrate and the concentration of gas sent to process to constantly change, preventing process control. Direct bubbling through the solution causes entrained microdroplets, leading to particles and staining on the wafer surface.
Flash vaporizers require very high temperatures at or above boiling. This accelerates H2O2 decomposition and generates microdroplets in large quantity. Flash vaporizers operate by dripping H2O2 onto a hot plate, which can lead to a pickup in contamination and particles from the vaporizer surface. While flash vaporizers can generate a steady output, the output content tends to oscillate with the difference between water and H2O2 boiling points and is prone to downstream condensation.
Versatility for Tight Process Control
The Peroxidizer allows process engineers to control pressure, carrier gas flow and H2O2 concentration. This versatility enables tight control over processes and lets the engineer experiment to find the optimal combination for new precursors, materials and architectures.
The Peroxidizer delivers H2O2 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 in vacuum to atmospheric pressure. The Peroxidizer adjusts temperature to achieve the desired output.
More Information on the Peroxidizer
For more information about the Peroxidizer, fill out an information request form or contact RASIRC directly.