In today's manufacturing world, the need for ultraprecise position measurement and control grows as feature sizes shrink in the semiconductor industry and the world of microelectromechanical systems (MEMS) impinges on conventional manufacturing. Now NanoWave, a startup company with roots at MIT, has announced that its subnanometer precision measurement technology is ready for licensing and commercialization.
The NanoWave scanning probe position encoder (SPPE) will enable manufacturing equipment to move and be controlled in real time at subnanometer or atomic levels of precision, with the capability of reliable measurement over 12 inches of travel - a key requirement for the semiconductor industry as it moves to 300-mm wafer fabrication.
The SPPE comprises four primary components: the head unit with oscillating scanning probe microscopy (SPM) probe; the holographic grating or reference scale with a highly periodic signal structure; the active gap-distance control system; and the signal processing unit, which measures position in real time, reliably and precisely, with NanoWave's patented phase-tracking system.
The sensor probe is oscillated with a sub-quarter-micron amplitude at a constant high frequency above the patterned holographic grating, which has an extremely small grating period (100-278 nm). The probe senses the field generated between its edge and the grating surface. This is amplified by a sensor amplifier. Meanwhile the SPM probe oscillation is detected by an independent sensor from which the reference signal is synthesized. This output is mixed with the SPM output, converting the position information into a phase-modulated signal referenced by the synthesized signal.
The numerical phase-tracking detection method provides digital interpolation simultaneously and yet allows an accurate phase accumulation as the grating scale moves in the X direction. Thus highly repeatable and superfine-resolution position encoding becomes possible in an ordinary atmospheric environment.
A line-patterned holographic grating is used for applications requiring measurement and control in the X and Z axes. A dot-patterned grating is used for applications requiring measurement and control in X, Y, and Z directions (Figure 1). When multiple probes are placed above such gratings, one can measure the motion in up to six axes with an atomic level of precision in each axis (Figure 2).
Among applications foreseen are semiconductor chip positioning at 50-nm rule, optical and DVD disk mastering, diamond turning of aspherics, and microelectromechanical systems (MEMS).