Saturday, June 11, 2016

RASIRC Study Finds 500 Fold Particle Reduction Using RASIRC RHS versus Flash Vaporizer

RASIRC Study Finds 500 Fold Particle Reduction Using RASIRC RHS versus Flash Vaporizer Low particle count pivotal to processing nanoscale features in new semiconductor devices.

San Diego, Calif – June 7, 2016 –RASIRC today announced that a new study shows that the RASIRC RainMaker® Humidification System (RHS) generates substantially lower particle count than flash vaporizers. The study compared particle generation in thermal and membrane evaporation systems using water. Particles are hazardous to microelectronics, causing defects and reduced electrical performance. Shrinking device sizes have made even the smallest particles and microdroplets into killer particles. The RASIRC RHS generates and delivers precise amounts of ultrapure water vapor for atomic layer deposition (ALD) and other semiconductor processes.
 Figure 1. Illustration of Membrane Technology Pervaporation process.

“Particle problems frequently arise when vaporizers are used to create gases from liquid sources,” said Jeff Spiegelman, RASIRC President and Founder. “Our pervaporization technology keeps liquid and gas separate by using a non-porous membrane. This technology demonstrates a particle-free vapor instead of a constant stream of particles that is generated with current vaporizer technology.” A principal drawing of the RHS device is shown in Figure 1 above. The study compared the relative particle/microdroplet generation of pervaporation versus flash vaporization in both continuous and intermittent flow conditions. A liquid evaporation vaporizer (LE), also known as a flash vaporizer, was compared to the RHS. Particles down to 10 nanometer size were measured by a condensation particle counter using water vapor as the condensation gas.

I asked Jeff Spiegelman about what motivated RASIRC to conduct this study and he responded “There has long been a debate on whether micro-droplets truly exist is a gas stream.  This study proves that they do exist and can be created or prevented through proper engineering.  Completely vaporizing a micro droplet in an ALD chamber is a thermodynamic challenge, by replacing flash vaporizers with membrane vaporizers this problem is prevented."  
Figure 2. Comparison of RHS and LE. LE internal temperature at 140°C. Overall, LE created 400 to 500 times more particles per minute.

Results (Figure 2) in continuous flow testing showed that the RHS was substantially more effective than the LE. The LE created 400-500 times more particles per minute than the RHS. In intermittent flow conditions, testing showed that the RHS was insensitive to flow interruptions while flash vaporizers created spikes of up to 5,000 on initiation of flow.

“Incomplete vaporization is the fundamental problem for flash vaporizers, causing spikes and a continuous stream of entrained microdroplets,” said Spiegelman. “The RHS operates at lower temperatures and adds water vapor directly to the carrier gas, reducing particle count reaching wafers and thereby improving film uniformity.”

Previous testing indicated that the RHS is feasible for ALD. In that testing, the RHS was able to achieve expected layer thickness and there were no obvious particle difference with a standard ozone plasma process.

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