Samsung Revs 64-mbit production in austin

01/01/1998

Samsung revs 64-Mbit production in Austin

Silicon has begun to flow through the new Samsung Austin Semiconductor (SAS) DRAM fab, for a 0.3-?m second generation 64-Mbit DRAM design - a market-driven step forward from the fourth-generation 16-Mbit that had originally been envisioned for initial output.

The fab line is not adopting some leading-edge technologies. CMP is not used, for example, and won`t be added until geometries go below 0.25-?m. Moreover, the Samsung 64-Mbit design uses only two layers of metal, and next-generation versions will make use of a capacitor design utilizing hemispherical grain (HSG) polysilicon, which provides increased surface area without deep trenches or high stacks. Deep UV litho tools will not be needed until the fab`s Phase II, when quarter-micron production will begin.

Further down the road, Samsung plans to add at least two more fab lines at the site, with the second one "very possibly" being a 300-mm facility.

Trial wafers at the existing 200-mm fab began to be processed in late September, with at-risk production slated to commence in November. Mass production in the fab`s Phase I started in November. Phase II, which will bring capacity up to a full 25,000 wafers/month, will require an investment of about $500 million over the $900 million that has already been invested in the building and equipment, said SAS president Sung W. Lee.

Initially, the fab (Samsung`s first outside South Korea) has been established as a near-duplicate of Samsung`s Line 8 in Kiehung. "As we stabilize, we will begin to work on selective improvement," said Paul Lewis, director of manufacturing development. "In Phase II, our level of involvement will be increased - US engineers will be writing the equipment acceptance specifications." He noted that Samsung has some of the highest DRAM yields and reliability in the world, and added, "There have been cases where we`ve transferred a process recipe, run it for the first time, and had it come out dead center. [Had we chosen different equipment], we would have had to do a tremendous amount of experimentation." Yields on test wafers processed from contact levels through two layers of metal are already in line with those achieved in Korea, he stated.

In most cases, two suppliers were chosen for each type of process equipment. This not only allows the company to take advantage of different suppliers` strengths, but also generates competitive pressure within each equipment area. In most areas, a tool is dedicated to a particular device layer or process step; this cuts the time lost to changeovers, and reduces the risk of misprocessing. Among those supplying Samsung Austin are:

 Nikon Precision and ASM Lithography, which have installed 10 and 6 i-line steppers, respectively. Capabilities between the two are comparable. Negotiations are still under way for the deep UV stepper contract; about 24 machines will ultimately be on site. Laser light sources will be mounted on a level below the cleanroom to save space.

 Deposition is handled by Applied Materials Endura and Precision 5000 systems, along with Novellus Concept I and Concept II machines. The Novellus units are in part used for glass deposition, including the coming HSG process, as well as overcoating following furnace depositions. Most of the P-5000 systems carry four separate chambers.

 Over 100 vertical furnaces, built by Kokusai and Tokyo Electron Ltd., will be installed for other deposition processes. No horizontal furnaces are used.

 In the implant area, a total of about five tools from Genus and Varian are dedicated to individual species.

 Etch tasks are handled by a combination of systems from Applied (about 50%), Lam Research (30%) and Tokyo Electron (20%). The TEL units were a late addition, for one undisclosed process-specific function, said Lewis. "They were a critical piece of equipment" for starting with the 64-Mbit design instead of 16-Mbit, he noted.

 Three Hitachi SEMs and a group of Electroglas probers are used in the on-site device lab.

 Ashland Chemical and Air Products provide both materials and maintenance of delivery systems, while machines from German manufacturer Durr handle abatement of volatile organic compounds.

 A Daifuku overhead wafer transport system runs in an oval around the fab`s central corridor; metrology areas are located along the corridor, dividing it from process bays. In coming months, automatic guided vehicles will be added to the litho cells, and later to the diffusion area, mimicking their use in Kiehung.

 Overall factory control is provided by a Samsung-developed Integrated Manufacturing System, which handles everything from recipe management to statistical process control, document control, and data collection, said Lewis. "In the photo area, for example, it collects critical dimension (CD) data, and feeds it forward for use in subsequent steps," he explained.

Training of employees has been a challenge, noted Lewis, since there is no local facility where they can study. About 300 workers have traveled to Kiehung for training, for periods ranging from three weeks to four months, noted Lee. A number of Kiehung-based employees are in Austin to aid in the startup. Employees work 12-hr shifts, alternating three-day and four-day work weeks.

Looking ahead, Samsung Austin has plans to build new fabs on either side of the current building, and has taken an option on 120 acres of adjacent land. Although Samsung was an early adopter of 200-mm wafers, Lee stated that for the 300-mm transition, "We would like to be between the fifth and tenth player." While the Austin facility would not adopt the larger wafers before Samsung in Korea, Lee said it is "very possible" that Austin`s Fab 2 will be 300 mm.

Another planned addition is an R&D center. "Initially, it will do R&D for process technology, and later we may add some design," said Lee.- P.N.D.