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Clean room supreme

Chemicals for semiconductor electronics manufacturing are tested for purity in BASF’s cleanroom lab. The manufacture of microchips, which are found in nearly every electronic device from computers to single lens reflex cameras these days, would not be possible without them.

Melanie Bauer is dressed in lightcolored coveralls, wears facehugging safety goggles and has her hair up under a cap. She could be taken for a surgeon ready for an operation. As a matter of fact, her work at BASF takes place in a highly sensitive environment: the clean room lab of the Competence Center Analytics. Elemental analytics experts work closely with BASF’s Electronic Materials unit. Samples of highly purified chemicals undergo final testing here before going out to customers all over the world.

Before Melanie Bauer enters her workplace, she passes through an airlock and is blasted in an air shower lasting about 30 seconds that removes the tiniest of contaminating particles from her clothes and hands. Things other people take for granted, like having a cup of coffee or visiting the bathroom, are a lot more complicated in her job than elsewhere. She has to change her outfit every single time and repeat the whole procedure – but that’s no problem for the chemical laboratory assistant: “It’s just routine in the meantime.”

She and her similarly clad colleagues are well aware of the fine points of their job. Their task in the clean room lab is to analyze the special chemicals required in the meticulous microchip production process. The continuous reduction in the size of electronic components over the years has placed increased demands on the chemicals necessary for their production. The rapid pace of development in the electronics industry requires ever greater quality control. The input of chemistry has helped to make computers faster than ever before and to come up with increasingly smart mobile phones that can do just about anything you want.

Hundreds of production steps are involved in turning ordinary silica sand into millimeterthick wafers and then going on to produce complex microchips. Even then, they won’t work unless the most stringent cleanliness standards have been complied with during the production process. When a surface area of barely a single square centimeter is teeming with as many as a billion transistors, even the tiniest of particles that would be invisible to the naked eye could have disastrous consequences and result in entire production runs having to be discarded.

Any surface irregularities on microelectronic components must not exceed a tolerance of more than a few nanometers – if that. A nanometer is to a meter what a football is to planet Earth. “You wouldn’t believe the absolutely miniscule levels of contamination we can detect here,” Bauer says, sitting down at a flow box to prepare an ammonium hydroxide sample. The flow box is a lab workstation that looks like an openbottom aquarium and meets the stringent clean room requirements. An inbuilt filter system draws in ambient air, removes dust particles from it and returns it to the circuit in the form of highly concentrated fresh air.

“Measurement precision is getting better all the time due to continuous improvements in the methods and equipment,” says Alexander Honacker, who has worked in the lab since it first opened 15 years ago. To give an idea of the level of precision that applies when reviewing sample contents for compliance with the applicable limits, he has an example to offer: “We could detect a sugar cube in a mountain lake.”

In addition to the rapid advances in analytical equipment and programs, the human factor is important, too. The skills of the dozen-or-so staff members and the care they exercise in the lab are crucial to the quality of the measurements obtained. For example, special devices are used for specific chemicals and samples are taken using high purity pipettes. Staff members wear gloves as a matter of routine and make sure not to brush against an experimental setup with a hand or arm. The standards of cleanliness in the lab sometimes cross over into everyday life. “I’ve developed a very special view when it comes to hygiene,” Honacker admits. “After emptying the dishwasher, I sometimes rinse the dishes one more time.”

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