RASIRC Inc of San Diego, CA, USA, whose products purify and deliver ultra-pure liquids and gases, has announced independent test results by the University of California, San Diego (UCSD) that show high-purity hydrogen peroxide vapor delivered to process by RASIRC technology enables the removal of carbon-based contaminants from germanium surfaces. A subsequent anneal removes oxygen. In addition, the hydrogen peroxide dosing creates a suitable surface for atomic layer deposition (ALD). RASIRC develops dynamic vapor generation technology that delivers high-purity vapor to key semiconductor and photovoltaic manufacturing processes.
“RASIRC is the only company able to create a consistent hydrogen peroxide vapour,” claims RASIRC’s founder & president Jeffrey Spiegelman. For high-purity hydrogen peroxide vapor generation and delivery, RASIRC offers a range of products that can deliver hydrogen peroxide concentrations up to 30,000ppm and flow rates from 10sccm to 30slm. “Alternative delivery techniques generate droplets that contaminate and pit germanium surfaces,” he adds.
UCSD performed a series of tests to determine the best method to clean and prepare germanium surfaces for ALD. Germanium is an attractive material for electronics manufacturers because of its much faster data transmission potential. Previous cleaning methods that involved liquid baths are not suitable for germanium because it easily dissolves and is removed from thin layers and new architectures, says RASIRC. Contaminants must be removed without any damage to germanium in the underlying surface. Similarly, cleaning and preparation must be performed in-situ, as any transfer from bath to chamber leads to more contamination.
Initial tests used high-purity hydrogen peroxide dosing at 300miliTorr and 300°C. This dramatically reduced the carbon signal and generated some germanium oxide. Subsequent heating to 700°C desorbed the oxide and eliminated the oxygen contamination. Another loop of dosing and annealing further reduced the carbon. A final longer dose of hydrogen peroxide resulted in a contaminant-free surface that was planar.
Because high temperatures can damage surfaces, a second test used atomic hydrogen dosing in place of the annealing step. This process was also effective at removing the residual oxygen layer. A final short-pulse, high-temperature anneal left a well-ordered surface with low roughness.
“The industry is reaching the limits of liquid chemistry for cleaning new materials and architectures,” believes Spiegelman. “In the near future, many processes will have to move to vapor. RASIRC technology is ready to support these processes.”
