KLA mask inspection group gears up for sematech project
11/01/1996
KLA mask inspection group gears up for Sematech project
Peter N. Dunn, Senior News Editor
KLA Instruments` Reticle and Photomask Inspection Division (RAPID), winner of a three-year SEMATECH development contract for a next-generation reticle inspection tool, will dedicate nearly 100 engineers to the project in an effort to meet aggressive milestones for the tool, which will be able to find defects just 90-100 nm in size using 248-nm light.
The effort is designed to ensure that the photomask industry has the inspection technology it needs to move forward to mask line sizes of 0.5 to 0.6 micron, required for production of devices with quarter-micron features and below. KLA executives say the consortium`s funding will accelerate their development process by two to three years, and thus avoid a gap in meeting the requirements of maskmakers (see table).
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The Semiconductor Industry Association`s National Technology Roadmap identifies mask inspection as a high-priority need for the lithographic process, regardless of which lithographic technology path is pursued.
"The present tool offerings run out of steam at 0.35 micron," noted SEMATECH manager of mask strategy Dick Moore. "We looked around and saw only one comprehensive enough equipment developer in the US, KLA. We negotiated with them to find out what it would take for a 0.25- and 0.18-micron reticle inspection tool, and they were very responsive, but there was a problem with their amount of available R&D funds." Hence, the SEMATECH member companies agreed to provide monetary aid, to ensure at-wavelength inspection capabilities for deep UV masks.
Moore added that there are a number of other critical gaps in the sub-quarter-micron photomask tool base, and said the KLA contract might serve as a model for other development efforts. He declined to identify the specific areas.
Caption:"It`s a huge project and a huge task, and every system has to be proven," said Grady.
Newly appointed RAPID vice president and general manager Ed Grady noted that 248-nm inspection is a daunting task: the printed area of a next-generation 9?9 reticle is almost twice as large as today`s advanced 6?6 masks, and the effective "pixel size" of the inspection system is twice as small - 125 nm instead of 250. This results in a geometric increase in the number of points that have to be inspected.
"We want a full reticle inspection in two to three hours, and that means that the computer, light, and sensor all have to be eight to ten times faster. It`s a huge project and a huge task, and every system has to be proven," said Grady, who referred to the program as one of the largest in KLA`s history.
He noted that to improve overall reliability, all subsystems of the as-yet unnamed new machine will be designed to be tested independently on KLA`s current flagship, the model 300. Prototype testing of a full machine is slated for late 1998; some of the subsystems will be back-compatible with the 300 series "to provide maximum value to the customer base," said Grady.
Ultimately, the two machines could work side by side, with the 300 handling future noncritical layers, and the SEMATECH-sponsored machine handling critical layers.
KLA president Ken Schroeder noted that quality, reliability, and manufacturing engineers are all participating in system design from the earliest stages, and communicating with customers to ensure that the system meets their needs.
In all probability, the system will use a 248-nm wavelength excimer laser light source, to provide at-wavelength inspection of deep ultraviolet masks. "That`s what the industry wants," said Grady, who noted that while a lamp-based system might cost less, its much lower throughput would likely result in higher cost of ownership. "There`s a question about whether the lamp is viable for getting to two to three hours," he said.
KLA`s new machine will be capable of inspecting 9?9-inch reticles, which will probably succeed 6?6 reticles early in the new century. "Anything can happen, but we believe that 9?9 will be the next generation, and we`re designing the system to be compatible," noted Grady.
Karen Brown, director of lithography for SEMATECH, called the new quarter-micron inspection machine "critical to the success of the semiconductor industry. It will be an indispensable tool for fabricating the 0.25-micron generation of integrated circuits, and it will strengthen the industry`s efforts to develop the 0.18-micron generation."
The developmental machine has not yet been named; Grady noted that although it will follow the model 300, it will probably not be named the model 400 in deference to Asian perceptions of the number 4 as unlucky. "We have to be sensitive to that," he said.