III-V and Si Cleanroom Technology

The “III-V and Si Cleanroom Technology” lab – together with the “III-V, Si & Ge Epitaxy Lab” – forms a central technological pillar of the Fraunhofer ISE's “Center for High Efficiency Solar Cells.” Here, we develop and validate key semiconductor manufacturing processes that lay the foundation for solar cell efficiencies at the international cutting edge.

In addition to processes for conventional silicon photovoltaics, the focus is particularly on processes for next-generation high-efficiency III-V, Si, and tandem cells. These technologies address applications in space travel, electromobility, concentrator PV, energy self-sufficiency, and power electronics. Fraunhofer ISE holds several world records in this field, including 26% for double-sided silicon solar cells, 36.1% for a III-V/Si tandem cell, 47.6% for a quad-junction III-V-based concentrator solar cell, and 68.9% efficiency for a GaAs cell under laser light for optical energy transfer.

All relevant process chains are available across more than 1,000 m² of cleanroom and laboratory space: photolithography, wet and dry chemical etching for III-V and silicon materials, PVD metallization and dielectric layers, as well as high-precision wafer bonding. Our infrastructure enables both the development of innovative processes and complete process chains, as well as the implementation of pilot-scale, customer-tailored developments. We support individual manufacturing steps – flexibly, in line with industry standards, and aligned with the highest scientific requirements.

Our Services in the Lab for "III-V and Si Cleanroom Technology" Include:

• Microtechnology Processes for Wafer Processing
• Nanoimprint Lithography and Successor Processes
• Process, Material, and Component Characterization

• Various materials: GaAs, Ge, InP, Si, Al2O3
• Pilot-scale production for wafer sizes up to 6" (150 mm); processing of smaller sizes and individual pieces is possible
• Cleaning processes (wet chemical, plasma-assisted)
• Wet and dry chemical patterning/etching
• Yellow light area for photo- and laser lithography to generate microstructures with bilateral alignment
• Wafer bonding technology for direct bonding of various semiconductor materials or via metallic interconnects (e.g., InP//GaAs, GaAs//Si, Au//Au)
• Deposition systems for thermal and electron beam evaporation and sputtering of metals and dielectric layers (metal contacts, anti-reflective coating)
• Electrolytic metal plating for solar cell contacting and as a carrier film
• Substrate debonding processes and thin-film technology
• Chip sawing for singulation

To fabricate photonic structures, we use a scalable nanoimprint process:

• UV roll-to-roll nanoimprint lithography (NIL) with flexible UV-transparent stencils
• Structure transfer onto III-V and silicon wafers via wet and dry chemical etching
• Deposition via PVD processes
• Compatible with wafer sizes up to 6" (150 mm); processing of smaller formats and pieces is possible

Various measurement techniques are available for quality assurance and for analyzing structures before, during, and after processing:

• Scanning electron microscopy (SEM) (including EDX and FIB sections)
• Atomic force microscopy (AFM)
• Digital microscopy
• White-light interference microscopy
• Transfer length measurement for determining contact resistance
• Reflectance measurement