Multiple 'C40s control deep sub-micron lithography

TI DSPs now used for maglev positioning

To meet the advanced requirements of deep sub-micron semiconductor production, researchers at Sandia National Laboratories (Livermore, CA) have developed a frictionless, nanometer-accurate wafer positioning system. The system uses magnetic levitation (maglev) technology controlled by a total of six TI TMS320C40 DSPs. Until recently, the nonlinear nature and computational requirements of maglev positioning has made the technology impractical for commercial wafer stepper applications, but by leveraging the processing power of multiple DSPs, the approach has now become viable.

Conventional fine-resolution wafer-positioning systems use piezoelectric, linear, or DC motors which must be physically coupled to a wafer holder through lead screws and friction drives. Maglev positioning completely eliminates this physical coupling, greatly increasing positioning flexibility and accuracy. The Sandia system uses the TI DSP-based maglev positioning to enable an advanced form of projection lithography, known as extreme ultraviolet lithography (EUVL). Already, developers of the technology are experimenting with 0.1-micron gate sizes, and commercial production processes based on EUVL technology are expected within the next ten years.

Sandia's experimental system, based on a Hydra quad-TMS320C40 VMEbus™ board from Ariel Corporation (Cranbury, NJ), controls the position of a magnetically levitated wafer holder by using data from capacitive sensors and laser interferometers.

The Hydra board, coupled with a pair of Ariel's 'C40-based CommIO-IP data acquisition cards, serves as a master controller for the maglev system. Each CommIO-IP card contains one A/D IndustryPack™ module to acquire sensor data, and three D/A IndustryPack modules to drive the actuators. The Hydra board communicates with the CommIO-IP boards via 12 'C40 comm ports, and a 'C40 on each CommIO-IP routes data between IndustryPack modules and the 'C40 comm ports. The Hydra board also acquires laser interferometry position information from seven Hewlett Packard laser axis interferometry boards.

On the Hydra board, 'C40 #1 handles host communications and provides a synchronization trigger to the laser interferometer cards. 'C40 #3 runs a real-time PID (Proportional Integral Derivative) control loop algorithm to calculate the magnetic forces needed to position the wafer holder. 'C40s #2 and #4 then compute real-time, force-to-current conversions, deriving outputs for the 16 D/A channels to drive the electromagnetic actuators. 'C40s #2 and #4 also handle data collection and status monitoring for the interferometer cards.

Although Sandia's designers developed the 'C40-based maglev wafer positioning system to meet the requirements of an EUVL application, the system's ultra-fine resolution and simplicity also makes it ideal for other wafer processing systems. Integrated Solutions Inc. (Tewksbury, MA), for example, is currently using the Sandia maglev fine positioning stage and an Ariel 'C40-based control system to upgrade their own stepper in a conventional projection lithography system.