Direct Electrostatic Suspension and Propulsion of Thin Plates



Direct Electrostatic Suspension and Propulsion of Thin
Plates
Keywords: Electrostatic force, Non-contact levitation, Aluminium
disk, Silicon wafer, Glass plate


1. IntroductionTo eliminate the contamination to aluminium disks,
silicon wafers and thin glass panels, new technology of their handling without
mechanical contacts is needed. Since the only applicable force which acts on
silicon wafer in vacuum is only electrostatic force, electrostatic levitation of
silicon wafer was examined to achieve levitation of 300 mm wafer. The levitation
of thin glass plate was also achieved by inventing the multiple divided
electrodes. Transportation of the levitated wafer and glass plate could be
succeeded by combining electrostatic drive. The developed technologies will be
utilized in handling system in super clean room and vacuum.


2. Suspension and drive of a silicon wafer or an aliminium
disk[1,2]As shown in Figure 1 and 2, by controlling the voltages
on electrodes to keep the position and attitude of a silicon wafer[1]
or an alminium disk[2] for hard disk drives, the wafer/disk can be
suspended stably without any mechanical contacts.







Figure 1: Electrostatic suspension of
aluminium disk.View from the bottom. Gap is around 0.4mm.
Figure 2: Electrostatic suspension system.

By using such a system, 300 mm wafer also could be suspended with a gap of
0.4 mm.
Since silicon wafers are able to be dealt as of conductive material in
electrostatic suspension and drive, they can be propelled not by the induction
drive but by the variable capacitance drive. A 8-inch wafer could be suspended
and transported beneath the electrode plate shown in Figure 3. Shifting the
activated electrodes and gap sensors in according to the position of the wafer,
driving force is generated by means of edge effect.







Figure 3: Device for non-contact drive of a
wafer.


3. Suspension and drive of a glass plate[3]Clean
transportation system for a thinner and wider glass plates is demanded in the
production of flat displays. Since glass has high resistivity, we did not expect
to levitate a glass plate by electrostatic force without spattering of a thin
conductive layer. Nevertheless, we succeeded to suspend a flat glass of 0.7mm
thick by developing the electrode pattern as shown in Figure 4.







Figure 4: Glass suspension system.
By means of the multi-devided electrodes, a
glass plate can be lift up immediately after the start of control. As for the
drive, on the other hand, glass is very suitable for the electrostatic induction
drive. We already succeeded to suspend and drive a 100 mm x 100 mm glass plate.


See also

High-power
electrostatic motor

Pulse
driven electrostatic induction motor
Dual
excitation multiphase electrostatic drive
Electrostatic
paper feeder
Particle
handling by electric field


References[1] J.Jin, T.Higuchi, M.Kanemoto: "Electrostatic
Silicon Wafer Suspension", Proc. 4th Int. Symp. Magnetic Bearings, pp. 343-348,
1994[2] J.Jin, T.Higuchi, M.Kanemoto: "Electrostatic Levitator for Hard Disk
Media", IEEE Trans. Industrial Electronics, Vol. 42, No. 5, pp. 467-473,
1995[3] J.U.Jeon, T.Higuchi: "Electrostatic Suspension of Dielectrics", IEEE
Trans. Industrial Electronics, Vol. 45, No. 6, pp. 938-946, 1998


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