René Raaijmakers
6 May 2021

One of Frits Klostermann’s main jobs as the manager of the litho workshop at the Philips Natlab in the 60s was fighting dust.

Chip lithography is all about productivity and precision. But there’s also a third, equally important parameter. One that hardly reaches the public eye, but that’s at least as critical to system architects of a wafer scanner: cleanliness.

Chip production is a continuous effort to reduce particles. ICs in the making are vulnerable. They spend months in a waferfab before they’re ready. One hit by a single dust particle and the whole chip is wasted. That battle against dust began in the 1960s and has resulted in the cleanest environments on Earth – wafer fabs. Today, they consist of huge spaces that are significantly cleaner than any food production plant or surgery room.

ASML cleanroom
One of the cleanest environments on Earth – a wafer fab. Credit: ASML

The size of a postcard

Avoiding dust was one of the first problems that Frits Klostermann, litho pioneer at the Philips Natuurkundig Laboratorium (Natlab), had to tackle in the early sixties. The young researcher planned to design his own lithographic equipment in early 1963, but after his transfer to a different research group, his boss, Henk Jonker, put his efforts on hold. Instead, Klostermann had to run the technical service group, tasked with producing contact masks and advanced photographic negatives for a variety of customers inside Philips. He now was responsible for an entire service department, with all the accompanying bureaucracy and administrative headaches. His world had been narrowed to eliminating dust and vibrations.

Jonker was a no-nonsense group manager who chose a practical path. He wanted to catch up with the Americans by buying a David Mann photorepeater to produce contact masks. After a David Mann Model 1080 arrived in Eindhoven in June 1963, Klostermann fired it up quickly.

In the early sixties, every part of the Philips conglomerate was working on miniaturization, placing heavy demands on Klostermann’s service department for photographic negatives (the mask center). His four assistants serviced Natlab and ten other Philips divisions.

That work still had little to do with microelectronics. Most of it was coarser work: contact masks on foil twice the size of a postcard with patterns for strain gauges and ultrasound components and spiral negatives for spiral groove air bearings and rotors in Philishave electric shavers. Klostermann quickly learned all the ins and outs of the materials, processes and equipment used in technical photography. He and his assistants soon found out they needed a cleaner working environment for the photolithographic work at the micron scale.

Unheard of

Cleanrooms didn’t yet exist at the time; they had to battle dust during exposure and contact multiplication. Klostermann complained about the poor filters in the water pipes and the dust particles in the air – particles of one to five microns were particularly problematic for them.

In the summer of 1963, Klostermann and his assistants adopted a dust elimination regime. They threw all non-essential equipment out the door. Smoking was forbidden inside the workshops – a phenomenon unheard of in a time when cigarettes were deeply embedded in Dutch culture. Lighting up was encouraged by popular sayings as “a man’s a joke if he can’t smoke.” Natlab even provided the cigars and cigarettes that group leaders used to make a hospitable gesture during meetings.

One of the assistants started scrubbing down the newly smoke-free rooms. “As soon as possible, he’ll start wiping down all horizontal surfaces with a damp cloth before work begins. We’re now waiting for instructions and cleaning materials,” Klostermann noted in June 1963. The lab area was inching ever closer to what would later be called a cleanroom: everyone started wearing nylon coveralls, new filters were installed in the water pipes and the assistants started using dust-free working fluids.