A wafer transportation apparatus with an advanced rotary magnetic coupling system for ultra-high vacuums has been developed. In this magnetic coupling system, the gap between the magnets and the yokes can be reduced to less than 1 mm, which enables a much larger coupling force than that of conventional systems.
The apparatus has been evaluated. After a series of experiments, we found the following :
1) The rotational stiffness is more than 4.3 Nm/deg and the maximum rotational torque is more than 7.6 Nm.
2) The positioning accuracy (±3δ) is ±0.048 deg in the circumferential direction and ±0.04 mm in extension and retraction.
3) The outgassing rate from the wafer transportation apparatus is 6×10
-8 Pam
3/s after baking (120°C, 48 hr.).
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