Solar Fab capabilities

The Solar Fab supports cell fabrication, module creation and reliability testing.

The lab has all the necessary processing equipment for raw silicon to serve as the input, and completed, characterized and tested solar cells generated as the output.

• Wet processing: Like semiconductor fabrication, solar cell processing requires intensive wet processing operations. Standard wet processing cleans such as RCA-A, RCA-B, piranha, BOE, saw damage removal and texturing can be performed in the Solar Fab.
• Screen printing: Owing to the need for inexpensive fabrication of solar cells, screen printing is used for patterning operations.
• Thermal operations: Standard processes exist for paste drying and paste firing, along with the ability to grow dry thermal oxides. Additionally, both rapid thermal annealing and tube annealing in Ar, O2, N2, and H2N2 are available. Finally thermal diffusion of P capability exists.
• Deposition: Deposition capabilities in the Solar Fab include e-beam evaporation, both DC and RF sputtering and PECVD.

The Solar Fab also fabricates modules, usually single-cell or 2×2 format, but a few larger modules, up to 36-cells, have also been made.

• Module fabrication: Soldering, paste dispense and up to full-size module lamination of solar cells is possible in the lab.
• Laser processing: Cutting substrates and fusing materials are possible with wavelengths from 1064–10600 nm.

Core reliability testing such as damp heat exposure and thermal cycling is available.

• Reliability: Dedicated damp heat and thermal cycle testing of single-cell and two-by-two module formats can be performed.

In addition to the above capabilities, various concomitant characterization techniques are also available in the Solar Fab. In turn, these characterization techniques may be classified as in-situ or post fabrication.

• In-situ: Capabilities include reflectometry, profilometry, bright light and microscope inspections, gauge thickness, weight change, resistivity, photoluminescence/electroluminescence and spectrophotometry.

Post fabrication: Quantum efficiency, steady state and flash I-V, and lock-in thermography are examples of available characterization techniques.

The Solar Fab has recently augmented the solar cell tool set to include technologies not found in or otherwise limited at the other Core facilities.  Currently MOCVD and ALD have been pursued, with other technologies under consideration.

• The Solar Fab Core at ASU now has two MOCVD tools, both just recently installed.  An Agnitron Mini Agilis 50 is available for growth of UWB nitride films (e.g., AlN, AlGaN, and GaN) for various applications such as research into power electronic devices.  Similarly, an Agnitron Agilis 100 can be used to study UWB oxide films such as beta, alpha, and epsilon phases of Ga2O3 and AlGa2O3. 
• The capability to deposit sandwich and multilayer structures has recently been realized in the Solar Fab using both the Savannah thermal ALD system and the Fiji plasma-enhanced ALD tool.  Currently tin, titanium, aluminum, silicon, hafnium, and water liquid sources are available on the ALD tools as are N2, Ar, H2, and O2 gases.  Both the Savannah and the Fiji ALD tools have ozone generators.  The lab is slowly expanding film capabilities, so additional requests are welcome.