SAFC Hitech(TM) Successfully Demonstrates Device-Quality GST Precursors For Phase Change Memory Ap...(dustrial scaling and highcompositional c...)

Since 2005, SAFC Hitech has been a participant in the European Commission-supported CHEMAPH project, a consortium set up to look at deposition methods for GST films. Researchers at the company's Bromborough facility in the UK have been actively investigating a variety of GST sources suitable for MOCVD, and have matched the physical properties of each metal precursor to enhance efficiencies at the desired growth parameters.

"Variations in cracking efficiencies were one major hurdle that we had to overcome," explained Kanjolia. "After extensive work to synthesise a number of different chemicals and characterize their physical properties, a combination of sources was found with a much improved match of thermal stability to allow decomposition to the same degree when simultaneously introduced to the deposition reactor chamber."

The actual chemicals of choice were found to be Ge(NMe2)4, Sb(NMe2)3 and iPr2Te. With these identified, SAFC Hitech then developed synthesis protocols to allow the isolation of high purity product in both small and large laboratory scale equipment. These materials are now available to customers with guaranteed quality by state-of-the-art in-house analysis. Samples have been shipped to various centers, and collaborations with partners have taken place to test the different combinations. Recent growth trials have resulted in successful deposition of device-quality GST using nitrogen as a carrier gas

"While a full process to make MOCVD devices remains to be demonstrated on anything other than very small research structures, the quality of the films on flat substrates is improving, and the precursor chemistry is ideally-suited," concluded Kanjolia. "The next challenge is to get the correct parameters
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