Pixelated capacitance controlled ESC
Implementations described herein provide a chucking circuit for a pixilated electrostatic chuck which enables both lateral and azimuthal tuning of the RF coupling between an electrostatic chuck and a substrate placed thereon. In one embodiment, a chucking circuit for an electrostatic chuck (ESC) has one or more chucking electrodes disposed in a dielectric body of the ESC, a plurality of pixel electrodes disposed in the dielectric body, and a chucking circuit having the one or more chucking electrodes and the plurality of pixel electrodes, the chucking circuit operable to electrostatically chuck a substrate to a workpiece support surface of the ESC, the chucking circuit having a plurality of secondary circuits, wherein each secondary circuit includes at least one capacitor of a plurality of capacitors, each secondary circuit is configured to independently control an impedance between one of the pixel electrodes and a ground.
1. A chucking circuit for an electrostatic chuck (ESC), the chucking circuit comprising:
a dielectric body having a workpiece support surface, the dielectric body comprising:
a chucking electrode disposed therein; and
a pixel electrode disposed in the dielectric body, the pixel electrode switchable between a floating state and a grounded state, wherein the pixel electrode is electrically coupled to a voltage controlled variable capacitor circuit to a ground when in the grounded state; and
a chucking circuit that includes the chucking electrode and the pixel electrode, the chucking circuit operable to electrostatically chuck a substrate to the workpiece support surface.
2. The chucking circuit of claim 1 , wherein the voltage controlled variable capacitor circuit further comprises:
a plurality of branches having decoupling resistors, the branches comprising:
a plurality of variable capacitors; and
a plurality of fixed capacitors coupled with the variable capacitors on a respective branch; and
a thin-film transistor coupled to the plurality of branches.
3. The chucking circuit of claim 2 , wherein the plurality of branches comprise six branches having a respective decoupling resistor providing about 5 ohms of resistance.
4. The chucking circuit of claim 2 , wherein the thin-film transistor selects which one or more of the branches are floating, and which one or more the branches couple the pixel electrode to the ground.
5. The chucking circuit of claim 2 , wherein the total capacitance for each branch of the plurality of branches is a summation of the respective variable capacitor and the respective fixed capacitor.
6. The chucking circuit of claim 2 , wherein a first branch of the plurality of branches consist of six variable capacitors each having a capacitance of about 3.4 pF, and the six variable capacitors are arranged in parallel with a first fixed capacitor having a capacitance of about 74 pF, and wherein the first branch has a total capacitance of about 16 pF.
7. The chucking circuit of claim 2 , wherein a second through sixth branch are similarly constructed, and have a total capacitance of about 8 pF, 4 pF, 2 pF, 1 pF, and about 0.5 pF respectively.
8. The chucking circuit of claim 7 , wherein the fourth through sixth branches having a total capacitance of less than 3.4 pF use a single MEMs variable capacitor in parallel or series with the respective fixed capacitor.
9. The chucking circuit of claim 2 , wherein the variable capacitors may provide between about 0 pF to about 3.4 pF.