In addition to several laboratories in UH main campus for thin film materials processing and metrology, our group’s main laboratory is housed in building 15 of the UH Energy Research Park through its affiliation with the Advanced Manufacturing Institute (AMI). AMI, led by Prof. Selva, was recently established as a University-wide initiative with a mission to address the challenges in scaling up lab-scale research advances demonstrated at the University of Houston to manufacturing as well as to develop unique solutions to manufacturing problems faced by industry.
The areas of manufacturing research undertaken at AMI broadly covers the ongoing work on superconductor wire manufacturing, roll-to-roll semiconductor manufacturing and as well as other areas of UH expertise such as flexible electronics, polymers, batteries and automation.
Superconductor Wire Manufacturing
It is very likely that our group is the only academic institution world-wide with complete facilities for thin film superconductor wire manufacturing. A pilot-scale superconductor metal organic chemical vapor deposition (MOCVD) tool (Figure 1) that is identical to that used in industry is available in our Energy Research Park facility. This system is being used for conducting manufacturing research and includes features such as a meter-long deposition zone, dual high capacity evaporators, dual high capacity pumping system, in-line X-ray Diffraction (Figure 1) for real-time information on crystallographic orientation of superconductor film growth and in-line vision system for real-time detection and tagging of defects in the film.
Figure 1. (Left) Pilot-scale MOCVD tool for superconductor wire manufacturing at our facility (Right) In-line X-ray Diffraction system in the MOCVD manufacturing tool for real-time quality control
The pilot MOCVD manufacturing tool is being upgraded in a new program funded by the DOE-Advanced Manufacturing Office with Advanced MOCVD features that was developed in a laboratory MOCVD tool. The Advanced MOCVD tool consists of as a novel reactor design that includes direct tape heating, direct temperature monitoring, laminar flow channel and plasma activation. The novel features provide excellent stability of film growth temperature, precursor composition as well as high precursor-to-film conversion efficiency. Record-high performance levels have been demonstrated using the Advanced MOCVD tool and this technology is being scaled up to manufacturing in the modified pilot MOCVD manufacturing tool. This is an excellent example of transitioning laboratory-scale research demonstrations to manufacturing and our record in securing a multi-million dollar project to execute this scale up. A photograph of the Advanced MOCVD tool is shown in Figure 2. This tool was completely designed and built by our group members.
A reel-to-reel system for electropolishing of substrates and electroplating system of copper stabilizer is available in our facility (Figure 3). This system was obtained as a gift from Los Alamos National Laboratory and completely revamped by our group into its present state. The reel-to-reel electroplating system is utilized to deposit copper stabilizer on long superconductor tapes. It can be used for electroplating of other materials as well.
A reel-to-reel system for magnetron sputtering of silver overlayer on superconductor wires are available at our facility (Figure 4). This system can be used for magnetron sputtering of other materials as well, on a manufacturing scale. Our group members designed and built this system in house. UH and its industrial partner AMPeers designed, constructed and commissioned a reel-to-reel wire winding system in our facility for spiral winding of superconductor tapes to fabricate round, ultra-small diameter wires (Figure 4). This technology of converting a flat tape to a round wire was developed by our group members. A startup company, AMPeers created by the Prof. Selva, which then secured Phase I and Phase II SBIR funding to scale up this technology to manufacturing at our facility in collaboration with UH researchers. The $1M Phase II SBIR program is a good example of our pursuing many effective pathways to transition UH technology to manufacturing.
Figure 4. (Left) Reel-to-reel system for magnetron sputtering of silver (Right) Reel-to-reel wire winding equipment for fabricating round, ultra-small diameter superconductor wire. Both equipment are present in our facility.
In addition to manufacturing tools for processing, our group members also have designed, constructed and commissioned novel reel-to-reel quality assurance tools for verification of quality of long superconductor wires. One such tool is a reel-to-reel in-field critical current measurement system (Figure 5) where critical current of long superconductor tapes is measured in a magnetic field of 5 Tesla. This equipment provides unique performance data that is important for verification of uniformity of quality of superconductor tapes in many applications but has not been available even in industry. Using know-how that was developed in our research laboratories, we established this innovative tool to qualify long tapes that are produced in our manufacturing research as well as those made in industry. A second quality assurance tool designed, built and commissioned by our group members is a reel-to-reel Scanning Hall Probe Microscope (SHPM) (Figure 5). This equipment consists of a high speed, high resolution driver for a Hall probe that maps the magnetic field and in turn the critical current of the tape. A spatial resolution of 100 µm is achievable even at a linear tape speed of 30 m/h. This tool too is being used for high-resolution critical current mapping of long tapes produced in our manufacturing research as well as those manufactured by industry. We have secured a sponsored research program with a superconductor wire manufacturer to use the SHPM tool to provide critical feedback to their manufacturing operations.
Roll-to-roll Semiconductor Manufacturing
Our group has developed technologies to fabricate single-crystalline-like semiconductor thin films on inexpensive, flexible substrates. These semiconductors have been used to demonstrate thin film transistors with 100-fold higher mobility than those currently used in flexible electronic devices. Also, they have been used to demonstrate thin film III-V semiconductor photovoltaics to achieve high efficiency solar cells at low cost. We have established a complete range of roll-to-roll thin film deposition systems for semiconductor manufacturing, including two ion beam assisted deposition (IBAD), three magnetron sputtering and one e-beam evaporation systems (Figure 6).
Roll-to-roll semiconductor processing, device manufacturing and metrology are conducted in our 13,000 sq.ft. Semiconductor Device Fabrication Laboratory (building 15) at the UH Energy Research Park. The Semiconductor Device Fabrication Laboratory consists of a class 10,000 cleanroom, a device fabrication area and a metrology area. The Laboratory is equipped with facilities to safely handle several toxic and pyrophoric gases (Figure 7) that are used in metal organic chemical vapor deposition (MOCVD) and plasma enhanced chemical vapor deposition (PECVD) processes for semiconductor manufacturing. Low pressure gas cylinders are used for arsine, phosphine and germane delivery to further enable safe operation. Being a self-contained facility off-campus with specialized gas handling in a secured building and its own in-house safety manager, our Semiconductor Device Fabrication laboratory provides a unique facility for UH researchers, not feasible elsewhere on campus.
We have established a novel tool for roll-to-roll MOCVD of III-V thin films in the cleanroom area in the Semiconductor Device Fabrication Laboratory (Figure 8). Some of the key features of this tool include dual reactors, one for roll-to-roll processing of 100 m long, 50 mm wide flexible substrates and another for 50 mm diameter wafers, delivery of six metal organic and six hydrides precursors, deposition temperature capability up to 1300°C, 600 W plasma sources, and all necessary features for safe operation. This tool is very likely the first roll-to-roll compound semiconductor MOCVD system ever to be built in the world.
Two Plasma Enhanced Chemical Vapor Deposition (PECVD) tools, one for epitaxial germanium and silicon deposition (Figure 9) and another for dielectric deposition are present in a class 10,000 cleanroom along with the MOCVD tool. Complete semiconductor device fabrication equipment including sputter, e-beam and thermal evaporation systems and lithography tools are available in the device fabrication area. Photolithographic tools for semiconductor device fabrication is present in a separate device fabrication area (Figure 9).
Several advanced metrology tools are available in our Semiconductor Device Fabrication laboratory. These include a Bruker X-ray Diffractometer (XRD) with area detector, Bruker High Resolution XRD system, Agilent Inductively Coupled Plasma Spectroscopy (ICP-MS) and Stylus and Optical profilometers. Solar cell conversion efficiency measurements system including a AAA Solar simulator with concentrated light, internal and external quantum efficiency measurement system, Hall mobility, time-resolved photoluminescence measurement systems are present in the metrology area.
Electromagnetic testing apparatus include a second critical current measurement apparatus with capability for measurements up to 1 T is present. A third system with capability up to 9 T, temperature range of 4.2 K to 77 K and 170° angular orientation between the magnetic field and superconductor tape is also available. A Physical Property Measurement System (PPMS) capable of magnetization and susceptibility measurements from 4.2 K to 77 K in magnetic fields up to 14 T is available.