Easier, Inexpensive Method Created for Etching Semiconductors

Advances in materials happen frequently in breakthrough medical device development, but many of the same manufacturing processes have been used for decades to create components. Recently, a new way to chemically etch semiconductors has been developed by researchers at University of Illinois (Champaign, IL), which is said to be less expensive and faster than other dry etch methods. Used in sensors, capacitors, LEDs, lasers and solar cells, the semiconductor gallium arsenide (GaAs) was used in a new process for etching patterned arrays to tune electrical and optical properties on the semiconductor wafer.

Previously, two techniques have been used for etching semiconductors, using either a chemical solution in the wet etching process to erode the semiconductor in all directions or using a directed beam of ions to card out a directed surface pattern in a process called dry etching. Though silicone is the most common material used in semiconductors, materials in a group referred to as III-V are more efficient in lasers, solar cells, and other optoelectronic applications, but can't withstand the damage made to the semiconductor's surface in the high-energy ion blasts used in dry etching.

A new wet-etching approach previously developed for silicon by the U of I group called metal-assisted chemical etching (MacEtch) was used on the III-V semiconductor material GaAs, and unlike other wet etching methods, works in one direction, etching from the top of the material downwards. This process first patterns a thin layer of gold film on the surface of the semiconductor, and then submerges it in the MacEtch chemical solution. Only the areas touching the metal are etched away, and as the metal sinks into the wafer, high-aspect-ratio structures are created. The metal can be easily cleaned from the surface without causing damage when the etching is complete.

The process of creating the metal film patterns was created by another U of I research team. Soft lithography creates patterns over the whole semiconductor wafer without the need of expensive optical equipment. The researchers plan to continue optimizing conditions for etching GaAs, as well as using the MacEtch process on other III-V semiconductor materials before attempting to fabricate devices like photonic crystals and reflector lasers. The technique was described in detail in the journal Nano Letters.