A New Technique to Measure and Deliver Low Levels of Water Vapor into Atmospheric and Vacuum Processes
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A New Technique to Measure and Deliver Low Levels of Water Vapor into Atmospheric and Vacuum Processes Jeffrey Spiegelman Executive Management, RASIRC, 11760 Sorrento Valley Road, San Diego, CA, 92121 Water vapor has multiple applications across industries including semiconductor, photovoltaic, fuel cells, carbon nanotubes, glass coating, and pharmaceuticals. Precise control of this water vapor is necessary to ensure that product yield and performance are consistent. In many of these applications, the process is performed in a vacuum. For a proper reaction to occur the water level needs to be kept low relative to the other gas species, with values below 500 ppm requested. This can require delivery at 1 sccm or less. This paper will briefly review applications and competitive technologies for water vapor and then present information on a new technology for delivery of water vapor into a vacuum. WATER VAPOR APPLICATIONS Semiconductor applications for water vapor include rapid thermal processing (RTP), atomic layer deposition (ALD), plasma stripping, and selective oxidation. For fabrication of photovoltaics, water vapor is needed to grow transparent conductive oxides, backside insulating layers and for annealing of both thick and thin films. Water vapor also plays an important role in Carbon NanoTube (CNT) fabrication [1]. The technology required to improve CNT growth rate and uniformity faces major hurdles in its transfer from research to production. TECHNOLOGIES FOR WATER VAPOR DELIVERY Up to now the delivery of water to a process has been difficult to control consistently. Simply boiling high purity de-ionized water to yield water vapor can avoid the problems and dangers inherent in the direct reaction of hydrogen and oxygen to yield steam. However, removing dissolved gases can be difficult and often requires multiple boiling/condensation cycles in a hermetically sealed environment, which can be expensive. Moreover, aerosols containing materials that are not normally volatile, such as salts or metals, can be produced during the boiling process and can add unwanted impurities. Current technologies include Bubblers, Direct Liquid Injection (DLI), Vaporizers and Membrane contactors. None of these technologies can deliver precise control of water vapor and at the same time remove particles, dissolved gases, and ionic impurities. For applications requiring high purity, safety, and fast return on investment (ROI), a new solution is required. INTRODUCING THE RAINMAKER™ HUMIDIFICATION SYSTEM The RainMaker Humidification System (RHS) adds controlled amounts of water vapor to any carrier gas. Needing only house de-ionized (DI) water and power, it can humidify inert gases, as well as oxygen, hydrogen, and corrosive gases. The system is capable of delivery into atmosphere as well as vacuum process pressures. The RHS consists of a non-porous membrane that excludes particles, micro-droplets, volatile gases, and other opposite charged species from being transferred to the carrier gas and ensures only water vapor is ad
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