Technical Insight
It's not all Si at Albany
Albany Nanotech is rapidly expanding its silicon processing facilities, but less well known are its III-nitride development activities, which include integration with silicon, writes Jon Newey.
When discussing the US semiconductor industry, Silicon Valley is the location that immediately springs to mind. However, thanks to the efforts of Governor George Pataki of the state of New York, another regional semiconductor hotspot is springing up in the north-east of the country. Much of the activity is centered on Albany NanoTech (ANT), which was established in 2000 at the University of Albany (part of the State University of New York). ANT combines an array of research areas covering opto- and nanoelectronics, micro- and nanosystems and thin-film technology into a fully integrated complex for R&D, prototyping, pilot manufacturing and education.
ANT boasts an impressively equipped array of 200 mm wafer cleanroom laboratories with an asset value in excess of $125 million. In the next two years this figure is expected to exceed $500 million, primarily as a result of the construction of the world s only university-based 300 mm Si processing facility.
The 300 mm center will become the home of International Sematech North, a joint $320 million five-year program between International Sematech and ANT. Sematech is a consortium of 10 of the world s largest semiconductor manufacturers, which through precompetitive collaboration, leads and reduces the costs and risks of developing manufacturing technologies for the semiconductor industry. In particular it has been grappling with issues surrounding sub-65 nm scaling and associated manufacturing on 300 mm wafers. The presence of Sematech and the backing of New York s governor and legislative leaders are in turn attracting other semiconductor companies into the region.
While the big silicon projects grab the headlines, ANT s varied activities in compound semiconductors continue to grow and attract funding. The Interconnect Focus Center at ANT has a large MBE program for the growth of nanoscale GaAs-based optoelectronic devices as part of an overall mission to integrate compound semiconductor devices on a Si platform, thus advancing high-speed information transport.
Integrating GaN and Si
More recently, a second compound semiconductor activity has begun at ANT within a new facility. The work, led by Shadi Shahedipour, focuses on the development of GaN-based devices such as UV emitters and the integration of high-quality GaN onto silicon substrates. The growth is done on two Emcore MOCVD systems that can accommodate one or three 2 inch wafers.
There is much interest worldwide in growing GaN onto Si, because Si wafers are relatively cheap and available in large diameters. However, the problems of large lattice parameter and thermal mismatches between GaN and Si must be overcome if high-quality material is to be grown (Compound Semiconductor August 2002 p49). The work at the laboratory has already resulted in a patent application for a method of growing GaN on silicon. Meanwhile, work on UV sources is continuing using sapphire substrates, with the aim that the work can be transferred to Si substrates once GaN of sufficiently high quality can be grown onto Si. In the future, Shahedipour and her colleagues hope to take advantage of ANT s comprehensive Si device processing infrastructure to integrate GaN-based optoelectronics with Si nanoelectronics.
Much of the funding for the nitride program comes from the State of New York and the General Electric Global Research Center (GEGRC). In future, Shahedipour wants to bid for funding from the DARPA programs that have been set up to accelerate progress in wide-bandgap materials and devices (Compound Semiconductor October 2002 p49). GEGRC, located close to ANT in Niskayuna, NY, has a wide-bandgap semiconductor research program, which includes a III-nitrides project. Shahedipour is also taking advantage of another element of GE s work - the development of bulk GaN wafers, grown using high-pressure, high-temperature techniques - for nitride homoepitaxy. Epitaxial growth of GaN onto bulk GaN would remove many of the problematic mismatches in material properties that are present when growing on sapphire and Si. While devices such as LEDs are remarkably tolerant of material defects, blue and UV lasers are less so, and require the highest-quality material if acceptable lifetimes and efficiencies are to be achieved.
ANT boasts an impressively equipped array of 200 mm wafer cleanroom laboratories with an asset value in excess of $125 million. In the next two years this figure is expected to exceed $500 million, primarily as a result of the construction of the world s only university-based 300 mm Si processing facility.
The 300 mm center will become the home of International Sematech North, a joint $320 million five-year program between International Sematech and ANT. Sematech is a consortium of 10 of the world s largest semiconductor manufacturers, which through precompetitive collaboration, leads and reduces the costs and risks of developing manufacturing technologies for the semiconductor industry. In particular it has been grappling with issues surrounding sub-65 nm scaling and associated manufacturing on 300 mm wafers. The presence of Sematech and the backing of New York s governor and legislative leaders are in turn attracting other semiconductor companies into the region.
While the big silicon projects grab the headlines, ANT s varied activities in compound semiconductors continue to grow and attract funding. The Interconnect Focus Center at ANT has a large MBE program for the growth of nanoscale GaAs-based optoelectronic devices as part of an overall mission to integrate compound semiconductor devices on a Si platform, thus advancing high-speed information transport.
Integrating GaN and Si
More recently, a second compound semiconductor activity has begun at ANT within a new facility. The work, led by Shadi Shahedipour, focuses on the development of GaN-based devices such as UV emitters and the integration of high-quality GaN onto silicon substrates. The growth is done on two Emcore MOCVD systems that can accommodate one or three 2 inch wafers.
There is much interest worldwide in growing GaN onto Si, because Si wafers are relatively cheap and available in large diameters. However, the problems of large lattice parameter and thermal mismatches between GaN and Si must be overcome if high-quality material is to be grown (Compound Semiconductor August 2002 p49). The work at the laboratory has already resulted in a patent application for a method of growing GaN on silicon. Meanwhile, work on UV sources is continuing using sapphire substrates, with the aim that the work can be transferred to Si substrates once GaN of sufficiently high quality can be grown onto Si. In the future, Shahedipour and her colleagues hope to take advantage of ANT s comprehensive Si device processing infrastructure to integrate GaN-based optoelectronics with Si nanoelectronics.
Much of the funding for the nitride program comes from the State of New York and the General Electric Global Research Center (GEGRC). In future, Shahedipour wants to bid for funding from the DARPA programs that have been set up to accelerate progress in wide-bandgap materials and devices (Compound Semiconductor October 2002 p49). GEGRC, located close to ANT in Niskayuna, NY, has a wide-bandgap semiconductor research program, which includes a III-nitrides project. Shahedipour is also taking advantage of another element of GE s work - the development of bulk GaN wafers, grown using high-pressure, high-temperature techniques - for nitride homoepitaxy. Epitaxial growth of GaN onto bulk GaN would remove many of the problematic mismatches in material properties that are present when growing on sapphire and Si. While devices such as LEDs are remarkably tolerant of material defects, blue and UV lasers are less so, and require the highest-quality material if acceptable lifetimes and efficiencies are to be achieved.
