Metal Gate Recessed Access Device (RAD) for DRAM Scaling
A functional DRAM with higher data retention characteristics than a planar access device has been demonstrated, using a metal gate recessed access device (RAD). Chemical vapor deposition (CVD) and atomic layer deposition (ALD) were used to deposit titanium nitride (TiN) and tantalum nitride (TaN), respectively. CVD TiN and ALD TaN-CVD TiN laminate gate stacks were integrated with a RAD module. ALD TaN-CVD TiN laminate gates showed enhanced drive current (IDS), higher transconductance (GM), higher mobility (¿EFF) and reduced off current (IOFF) characteristics compared to CVD TiN gates. Device characteristics and reliability data for both the planar devices and RADs are presented. The ALD TaN-CVD TiN laminate metal gate RAD showed much improved data retention characteristics compared to a conventional planar device with a poly silicon gate. The optimum thickness of ALD TaN in the laminate stack is discussed.
Atomic layer deposition of TaN and Ta3N5 using pentakis(dimethylamino)tantalum and either ammonia or monomethylhydrazine
Abstract TaN x thin films were grown at temperatures ranging from 200 to 375 °C using atomic layer deposition (ALD). Pentakis(dimethylamino)tantalum (PDMAT) was used as a tantalum source with either ammonia or monomethylhydrazine (MMH) as a nitrogen co-reactant. Self-limiting behaviour was observed for both ammonia and MMH processes, with growth rates of 0.6 and 0.4 A/cycle, respectively at 300 °C. Films deposited using ammonia were found to have a mono-nitride stoichiometry with resistivities as low as 70 mΩ cm. In contrast, films deposited using MMH were found to be nitrogen rich Ta 3 N 5 with high resistivities. A Quartz Crystal Microbalance (QCM) was used to measure mass gain and loss during the cyclic ALD processes and the data was used in combination with medium energy ion scattering (MEIS) to elucidate the PDMAT absorption mechanisms.
PASSIVE AND LOW-ENERGY RESEARCH AND PRACTICES-DEHUMIDIFICATION
Methods of achieving acceptable indoor conditions in overheated, temperate, and underheated humid climates are discussed and compared. Desiccants and desiccant systems utilizing solid and liquid sorbents and various low-energy mechanical systems are described and evaluated.