One stop shop for chip producers

Wisconsin has been a centre of manufacturing for more than 100 years and Sigma-Aldrich, a global chemical manufacturer, has had a significant manufacturing presence in the state for at least a quarter of a century. Sheboygan, only 45 minutes away from Sigma-Aldrich’s major materials distribution centre in Milwaukee and a three-hour drive from Chicago’s O’Hare International airport, is the site of a SAFC campus that has seen investment in excess of US$100m (€63.8m) over a number of years to build and extend its chemical manufacturing infrastructure.

April 2008 saw the opening of the latest addition to the Sheboygan site: a $9m (€5.7m) cleanroom facility, which has enabled SAFC Hitech, a focus area within SAFC, a member of the Sigma-Aldrich Group, to produce, package and analyse products all in one location. The 5,000ft2 facility, consisting of an ISO Class 4 cleanroom, a distillation suite and office space, provides in-house trace metals analysis and the capability to clean and fill containers in a tightly controlled environment, ensuring that SAFC Hitech customers have access to an uninterrupted supply of quality materials required for advanced semiconductor manufacturing.

The Sheboygan campus was selected as the site for the new cleanroom as it already provides large-scale manufacturing of products for the material science industry. Sheboygan is not a major cosmopolitan area so the location, close to the shores of Lake Michigan, offers fresh, clean air and a plentiful supply of clean water – critical elements in cleanroom operations.

There is also ample room for future expansion of the site. SAFC has 77 acres of land developed for industrial use an owns 592 acres of land surrounding the manufacturing campus.

Despite the trend towards off-shore manufacturing for many industries, and in particular for semiconductor manufacturing, the US remains the home of the largest chip manufacturer and the world’s largest Original Equipment Manufacturer (OEM). In addition, it is a hotbed for technology innovation and a global chip design centre. For technical design and the manufacturing of materials, the US is still a key centre of excellence and the home of key markets for material consumption. In expanding the Sheboygan site, it was vital that the company had this capability to service customers at source.

The building in which the Clean-1 facility is located was originally built as a warehouse for the storage of flammable and dangerous materials. From a design and engineering perspective, it presented certain advantages as well as challenges. Among the advantages were that the building already meets many of the building codes required for handling of dangerous materials. In addition, there are many existing facilities already in place for the intended application of the building, reducing the overall cost of building a facility.

Creative solutions

On the other hand, the system design required additional features and functions that were not part of the original warehouse design. The design team therefore had to be creative to make optimum use of the existing warehouse structure. This created certain complexities in logistics and production planning, but these operations are modular to some extent, and can be sited at different locations on the Sheboygan campus without compromising the production processes.

The Clean-1 area itself houses only the most high value-adding operations in SAFC Hitech’s manufacturing process. The designers of the facility have worked in major semiconductor fabs and materials manufacturing environments and have extensive working knowledge of the semiconductor materials supply industry. The majority of the design concepts were generated as a result of the experience gained working in these other facilities.

Sample handling

One important aspect of the ISO Class 4 facility is its analytical area, which handles analytical sample preparation and analysis and has an area for container cleaning and processing and product packaging. All these functions have been segregated and modularised for optimum process efficiency and quality consistency.

Chip manufacturing must be carried out in an ultra clean environment. With the advancement of manufacturing technology, the requirements for cleanliness are only going to be tightened further. The design of the facility ensures that the company will continue to meet these stringent requirements for at least another four to six years.

In general, contamination in the chip manufacturing process includes particulate contamination as well as conducting or mobile ion contamination. The design of the Sheboygan cleanroom guarantees that the company is capable of producing, testing and packaging products where parts per billion level of purity in mobile ions is achieved while keeping particle adders to a minimum level. The clean environment ensures consistent levels of product purity are maintained from point of manufacture through to final test and packaging.

One of the common misunderstandings in the industry is that equipment is everything. In fact, equipment is only half of the overall equation. SAFC Hitech’s real strength is that it has a group of people who have the depth of knowledge and technical knowhow to operate this complex equipment and maintain the facility to optimise production. Their vigilance and expertise are the company’s best precautions in keeping within control boundaries and minimising contaminants by maintaining best practices for the operations.

In terms of the equipment used in the Sheboygan expansion, elements such as the HVAC system used were custom-designed to meet the company’s specific needs. In this case, the central blower is sized to meet the factory’s operational and cleanliness requirements. SAFC Hitech has also adopted a combination of plenum and individual blower configurations to satisfy both chemical-related operations as well as non-chemical related operations.

Of special note, this facility is designed to fill pyrophoric materials in an ISO 4 operational environment. It has to meet both Class I Div II safety requirements as well as the stringent cleanroom requirements. As a result, the HVAC control system was fairly complex to design, as its operation nor its maintenance are not trivial tasks.

From a cleanroom efficiency perspective, SAFC Hitech considered raised floor design to be the best approach. However, this design is incompatible with certain chemical operations. Therefore, the air circulation is achieved by wall air return methods, in a configuration consistent with practices in the cleanroom chemical operations in the industry.

The cleanroom houses general cleaning, filling and analytical equipment, including a high-resolution inductively coupled plasma mass spectrometer (ICP-MS) that is highly sensitive and capable of the determination of a range of metal concentrations below one part in 1012. Here again, while the company has state-of-the-art equipment, that is merely part of the equation. The real capability resides in those people who operate it.

High visibility

To protect the cleanroom integrity, the company installed different types of hatches, doors, pass through and viewing windows. To allow visitors to see as much of the operation as possible without having to enter clean areas, the cleanroom was designed with good use of viewing windows. It also has both simple doors and interlocked doors that cannot be opened at the same time. Process flow is an extremely important part of the fab operation; the key factor to avoid is cross-contamination between different processes and materials, and this is something that the facility design and operational procedures address.

Materials produced in other buildings have to be moved into the cleanroom for filling into final product containers. These containers are cleaned and processed in a cleanroom environment to ensure consistent product quality. The process of moving these materials into the cleanroom is called the fab-in process. During this process, all in-coming materials and equipment must be cleaned using fab-in procedures. Containers filled with products must be properly packaged using the proper protocol before leaving the cleanroom. This minimises the cleaning required when customers receive and use these materials in their own cleanroom environment.

The company has designed materials mop-down and staging areas, in which incoming containers and equipment are thoroughly cleaned as per cleanroom protocol before they are moved into the cleanroom environment. These fab-in areas are equipped with interlocked doors. For safety reasons, the interlocking mechanism will be temporarily disengaged if the fire alarm is triggered. For personnel fab-in, all relevant measures have been adopted to ensure that the cleanliness of the cleanroom is maintained. Personnel change into cleanroom gowns, go through air showers and wash hands before entering the cleanroom.

Segregated flow

To maximise work efficiency, and prevent cross-contamination, in addition to in-coming and outgoing materials following different flow-paths, incoming personnel and outgoing personnel also follow different paths. This method has been proven to be effective in minimising cross-contamination, enhancing personnel safety and optimising cleanroom operations. The company adopts a gowning and changing procedure that is entirely consistent with those of top chip manufacturers, such as TSMC, Samsung and Intel.

Initially the facility is operating an eight hour one-shift basis, but can ramp up to be operated as a 24/7 three-shift operation as required. Clean down is performed daily or on an “as needed” basis. The design allows for the ability to configure the suites to the job at hand, enabling a range of materials to be purified. This adaptability to material/process per suite may be accomplished while also maintaining segregation of product classes where necessary, further minimising any potential for cross-contamination.

The building for the distillation suites is due to be commissioned during second half of 2008. It can house up to 200L purification systems with 22ft column heights.

From initial design and concept of expanding the facility to full operation took just under two years and it was an extremely valuable learning process for us, and will act as a blueprint for further global expansions or new builds in future.