Teamwork, clean construction key to quick cleanroom completion
Contract wafer bumping facility celebrates first year in fast-track cleanroom
By Sheila Galatowitsch
Two years ago, when company officials at Delco Electronics (Troy, MI), which had a proprietary flip chip technology, and Kulicke & Soffa Industries (Willow Grove, PA), a semiconductor equipment manufacturer, joined forces to create Flip Chip Technologies (Phoenix), they knew they were onto something big. It was so big — the product`s use is predicted to grow at a 38 percent compound annual growth rate between now and 2001 — they didn`t want to waste a single day getting to market.
From the beginning in February 1996, the pace for bringing online their contract wafer bumping facility for flip chips has been aggressive. In May 1996, a start-up team was in place, and two months after that, construction of the plant, which houses a 13,000-square foot Class 1,000 cleanroom, was underway. In only 11 weeks, the cleanroom was complete, and two months later, Flip Chip was processing customer wafers, increasing worldwide wafer bumping capacity for flip chips by more than five times.
The plant, online now for a year, boasts a capacity of 1.8 million flip chips per day, making it the largest contract flip chip facility in the world, according to the company. And it has an impressive first-year record: zero-injury construction; outstanding faci lity per for mance with all systems performing as designed 99.98 percent of the time; fewer than 80 minutes of downtime of any cleanroom system in 12 months; and minimal manpower necessary to operate the facility.
Flip Chip`s achievement can be traced back to the design and construction process, says Facilities Vice President Robin Ross. “The thing that made us successful was teamwork, communication and a coordinated focus on a common goal,” Ross says.
Phoenix was chosen as the site for the new facility because of its proximity to manufacturers in the semiconductor industry. The company leased a new 37,000-square foot building, which included 6,000 square feet of office space, and started planning the cleanroom design.
The 13,000-square foot cleanroom was built to a Class 1,000 modified ballroom design. It has bays and chases separated by cleanroom walls, high-efficiency particulate air (HEPA)-filtered air and conductive tile flooring. Positive pressure airflow is recirculated into the bays and chases via a 12-inch opening between the wall and floor. All of the airflow is above the floor, Ross says, with nothing going through the floor.
Seven recirculation air handlers are mounted in the mezzanine, which is treated as Class 1,000 cleanroom space. “In a typical cleanroom, mezzanine and chase areas are not considered clean. But we wanted to keep not just the work area, but the whole envelope surrounding the cleanroom, at Class 1,000,” says Kiet Nguyen, facilities engineer. Although the mezzanine cannot be certified as Class 1,000 because of lighting and flooring issues, Flip Chip personnel use the same cleaning and particle control protocols in the mezzanine as in the rest of the cleanroom.
The utilities include 18 megohm DI water, process cooling water, clean/dry air, nitrogen and several vacuum systems. Temperature, pressure, humidity and particle control correspond to Class 1,000 requirements, although the cleanroom has consistently performed at Class 100 levels.
From jeans to gowns in one day
After the concrete floor from the existing building was removed to make way for the cleanroom floor, all the construction groups began work simultaneously. Several local design and construction firms, including Huber, Hunt and Nichols (Phoenix), a construction management company, worked with Flip Chip on the clean-build project.
Safety was the team`s top priority throughout the entire construction process, says safety engineer Maurice Camp. Safety issues were discussed at the beginning of every meeting, and jobs and procedures were reviewed daily with the crews. This intense focus on safety led to zero injuries during construction, Camp says.
The notoriously hot summer days in Phoenix complicated the aggressive construction schedule. “The height of our construction was in Phoenix in August,” Ross says. “We worked split shifts starting at 5 a.m., working for eight to 10 hours, then stopping. The second shift started at 7 p.m. That way we avoided the hottest hours of 2 to 6 p.m.”
A major challenge in the project was getting the cleanroom built and cleaned quickly enough to begin to move tools in. “After we completed the mezzanine, we cleaned as construction was taking place on the main floor, and then did a super-clean prior to certification,” says Bill James, facilities leader who oversaw commissioning and startup of the new plant. A rigorous discipline was maintained during the clean construction, and air handlers and recirculation fans were cranked up early. The company also certified each contractor and then enforced certification with Flip Clip personnel, says Nguyen.
The plan worked so well that the cleanroom went from construction protocol number one — boots and jeans — to protocol number four — full gowns — in one day. “In going to that protocol we focused on the HEPA-filtered makeup air handler unit. We started that unit up early with four weeks of construction left. As soon as we could, we closed the envelope of the cleanroom totally and forced HEPA-filtered clean air into the room,” Ross says.
The HEPA-filtered air was the only air circulating in the cleanroom as workers finished construction. Since the only air outlet was the construction entrance, people, materials and equipment entering the room were automatically swept with clean air.
The fully gowned workers operated un der Class 1,000 protocols to complete construction. All tools and materials coming into the cleanroom were cleaned and wiped down with a standard dilute water and isopropyl alcohol mixture. “The first particle count measurement taken was 13,000. In less than a week, counts were under 1,000,” Ross says.
Those counts were achieved even by substituting plastic for the cleanroom doors, which were six weeks away from delivery when the cleanroom was sealed and the HEPA-filtered air was circulating.
In fact, the schedule was so accelerated, tools were commissioned and processes begun before some of the waste systems were fully operational. “We had to manually handle the wastewater generated because the automatic system was not yet online,” says environmental engineer Mark Berner. The small quantities of wastewater were accumulated in a tank and manually neutralized on a batch basis, then discharged in full compliance with all environmental and safety regulations.
The final construction, commissioning and start-up teams also worked simultaneously, according to James. “We had the operations and commissioning team onsite shortly after construction started. We moved through commissioning system by system, as each system became completed to a point where the contractor was ready to sign off. We accepted the system and did preliminary commissioning without waiting for a total sign-off,” he says.
Distributed control system
Ross reports few unanticipated changes during the construction process, but one change was significant. Since a critical design para meter was 100 percent consistent utility supply to the cleanroom, the team decided to im plement a distributed control system that monitors all facility variables by computer.
The advanced control system pro vides automatic starting and uninterrupted supply of utilities and support systems to the cleanroom. It monitors all system operations and pa ra meters, including airflow, exhaust, particle counts, temperature and humidity, and makes continuous adjustments. Under certain emergency conditions, it will automatically page a technician. “That`s a unique feature for a facility this size,” Ross says. With the control system, only one technician is required to supervise facility operations. The cleanroom itself employs 55 people in its two-shift, 16-hour operation.
In addition to the control system, another unique feature of the cleanroom is its electrical backup system. “We decided to go with two separate electrical feeds to the whole facility from two completely separate substations located several miles apart,” Ross says. In case of power loss from one substation, power will automatically transfer to the alternative substation in a two-second delay. If both substations fail to deliver power, a back-up emergency generator installed by the company will supply power in six seconds.
The system was tested last summer during one of the Silicon Desert`s monsoon storms, which caused a power outage in the city. Flip Chip`s automatic transfer system and generator “functioned as designed,” Ross says. “The likelihood of our facility being without power for any length of time is zero.”
Moreover, all of Flip Chip`s facility systems have 100 percent redundancy in case of loss of any one system. That includes all utilities and service entrances for the electrical load. “Everything has a backup, even down to the computer automation system,” James says. In case of failure, the distributed control system will automatically start the redundant system and notify the facilities technician. All these redundancies are necessary to safeguard the customer wafers, which are constantly in a stage of the manufacturing process. “If we are unable to maintain any of the requirements of the fab, we jeopardize the customer`s wafer,” James says. “Flip Chip`s policy is to do everything we can to support our customers.”
Flip Chip has also brought all tool installation, maintenance and repair capabilities in-house, eliminating dependence on contractors. “This way we are not at the mercy of contractor schedules, and it allows us to be in control of our own destiny,” Ross says. In addition to the freedom, it also saves on costs, he adds.
Expansion
The flip chip market is expected to grow at a 38 percent compound annual growth rate over the next three years. Ultimately, flip chips will replace wirebonded chips in several applications, such as mobile electronics, which are under continuous pressure to become smaller, and high-performance electronics products, which differentiate themselves based on functionality.
Market growth will fuel Flip Chip Technologies` growth. The company expects to launch a three-shift, 24-hour operation this year. An additional 7,600 square feet is available in the current location for future expansion, and as the business grows, plans are in place to add additional facilities, which will be modeled on the success of its flagship plant.
“We have an excellent team in place at Flip Chip to grow with the technology and our customers,” Ross says. “Our facilities team is well experienced to support this plant`s growth, as well as getting new facilities on the ground when and where needed — safely, quickly and with absolute quality. That will allow Flip Chip to maintain its position as the world`s premier bumping and wafer processing service.”
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The cleanroom at Flip Chip Technologies` wafer bumping facility (above and right).
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The deionized water plant.
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Above, a group of Flip Chip Technologies wafers.
Left, a view of the scrubbed exhaust system.
Bumping defined
Flip Chip`s core service is wafer bumping. The “bump” in a flip chip is the electrical interconnection, analogous to the wirebond in a traditional chip. Bumping places tiny dots of solder on the chip, which is then flipped over and soldered onto a circuit board. The bumps make the connections commonly made by metal leads. A flip chip can be 95 percent smaller than a standard chip. It also has increased functionality and improved reliability, according to the company. Flip chips are smaller, higher performance alternatives to wirebonded chips and are used in electronics such as pagers, cellular phones, laptops and cameras.
Device and component manufacturers provide wafers to Flip Chip for bumping. The facility is designed to handle 16,000 wafers per week on 4-, 5-, 6- and 8-inch wafers. The company also provides reliability modeling; test vehicles, such as chips and substrates; and assembly processes and underfills. It also assists in the implementation of flip chips into an application. Most all of these processes require a cleanroom. — SG
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Flip Chip`s FA10 Full Array Bump Daisy Chain Flip Chip Test Die, with a close-up view of a solder bump (above).