RF impedance matching circuit and systems and methods incorporating same
In one embodiment, an RF impedance matching network utilizing at least one electronically variable capacitors (EVC) is disclosed. Each EVC includes discrete capacitors operably coupled in parallel, the discrete capacitors including fine capacitors and coarse capacitors. A control circuit determines a parameter related to the plasma chamber and, based on the parameter, determines which of the coarse capacitors and which of the fine capacitors to have switched in to cause an impedance match. The increase of the variable total capacitance of each EVC is achieved by switching in more of the coarse capacitors or more of the fine capacitors than are already switched in without switching out a coarse capacitor that is already switched in.
1. A radio frequency (RF) impedance matching network comprising:
an RF input configured to operably couple to an RF source;
an RF output configured to operably couple to a plasma chamber;
at least one electronically variable capacitors (EVC), each EVC comprising discrete capacitors operably coupled in parallel, the discrete capacitors comprising fine capacitors and coarse capacitors, wherein each EVC has a variable total capacitance that is increased when the discrete capacitors are switched in and decreased when the discrete capacitors are switched out;
a control circuit operably coupled to the at least one EVC, the control circuit configured to:
determine a parameter related to the plasma chamber;
determine, based on the parameter related to the plasma chamber, which of the coarse capacitors and which of the fine capacitors to have switched in to cause an impedance match;
cause the determined coarse capacitors and the determined fine capacitors to be switched in;
wherein the increase of the variable total capacitance of each EVC is achieved by switching in more of the coarse capacitors or more of the fine capacitors than are already switched in without switching out a coarse capacitor that is already switched in.
2. The matching network of claim 1 wherein the parameter related to the plasma chamber is the impedance of the plasma chamber.
3. The matching network of claim 1 wherein when the variable total capacitance is increased and the control circuit does not switch in more of the coarse capacitors than are already switched in, then the control circuit switches in more fine capacitors than are already switched in without switching out a fine capacitor that is already switched in.
4. The matching network of claim 1 wherein any increase of the variable total capacitance of each EVC is achieved by switching in more of the coarse capacitors or more of the fine capacitors than are already switched in without switching out a coarse capacitor that is already switched in.
5. The matching network of claim 1 wherein the coarse capacitors and the fine capacitors have values having a ratio substantially similar to 10:1, respectively.
6. The matching network of claim 1 wherein the coarse capacitors have a coarse capacitance value and the fine capacitors have a fine capacitance value, the fine capacitance value being:
less than or equal to one-half (½) of the coarse capacitance value;
less than or equal to one-third (⅓) of the coarse capacitance value; or
less than or equal to one-fourth (¼) of the coarse capacitance value.
7. The matching network of claim 1 wherein the EVCs comprise two EVCs.
8. The matching network of claim 1 further comprising a driver circuit operatively coupled between the control circuit and the at least one EVC, the driver circuit being configured to alter the variable total capacitance of each EVC based upon a control signal received from the control circuit.
9. The matching network of claim 8 further comprising an RF filter operatively coupled between the driver circuit and the EVCs.
10. The matching network of claim 8 wherein the driver circuit is configured to switch a high voltage source on or off in less than 15 μsec, the high voltage source controlling electronic switches of each of the EVCs for purposes of altering the variable capacitance.
11. The matching network of claim 1 wherein each discrete capacitor of each EVC is switched out by applying a high voltage to an electronic switch and switched in by applying a low voltage to the electronic switch, the low voltage being opposite in polarity to the high voltage, and both the high voltage and the low voltage being applied from a common output of a driver circuit.
12. A method of impedance matching, the method comprising:
operably coupling an RF impedance matching network between an RF source and a plasma chamber, the matching network comprising:
at least one electronically variable capacitors (EVC), each EVC comprising discrete capacitors operably coupled in parallel, the discrete capacitors comprising fine capacitors and coarse capacitors, wherein each EVC has a variable total capacitance that is increased when the discrete capacitors are switched in and decreased when the discrete capacitors are switched out;
a control circuit operably coupled to the at least one EVC;
by the control circuit, determining a parameter related to the plasma chamber;
by the control circuit, determining, based on the determined parameter related to the plasma chamber, which of the coarse capacitors and which of the fine capacitors to have switched in to cause an impedance match;
by the control circuit, causing the determined coarse capacitors and the determined fine capacitors to be switched in;
wherein the increase of the variable total capacitance of the each EVC is achieved by switching in more of the coarse capacitors or more of the fine capacitors than are already switched in without switching out a coarse capacitor that is already switched in.
13. The method of claim 12 wherein when the variable total capacitance is increased and the control circuit does not switch in more of the coarse capacitors than are already switched in, then the control circuit switches in more fine capacitors than are already switched in without switching out a fine capacitor that is already switched in.
14. The method of claim 12 wherein any increase of the variable total capacitance of each EVC is achieved by switching in more of the coarse capacitors or more of the fine capacitors than are already switched in without switching out a coarse capacitor that is already switched in.
15. The method of claim 12 wherein the coarse capacitors and the fine capacitors have values having a ratio substantially similar to 10:1, respectively.
16. The method of claim 12 wherein the coarse capacitors have a coarse capacitance value and the fine capacitors have a fine capacitance value, the fine capacitance value being:
less than or equal to one-half (½) of the coarse capacitance value;
less than or equal to one-third (⅓) of the coarse capacitance value; or
less than or equal to one-fourth (¼) of the coarse capacitance value.
17. The method of claim 12 wherein the EVCs comprise two EVCs.
18. The method of claim 12 :
wherein the RF impedance matching network further comprises:
a driver circuit operatively coupled between the control circuit and the at least one EVC, the driver circuit being configured to alter the variable total capacitance of each EVC based upon a control signal received from the control circuit; and
an RF filter operatively coupled between the driver circuit and the EVCs;
the method further comprising switching a high voltage source on or off in less than 15 μsec, the high voltage source controlling electronic switches of each of the EVCs for purposes of altering the variable capacitance.
19. A method of fabricating a semiconductor, the method comprising:
placing a substrate in a plasma chamber configured to deposit a material layer onto the substrate or etch a material layer from the substrate; and
energizing plasma within the plasma chamber by coupling RF power from an RF source into the plasma chamber to perform a deposition or etching, and while energizing the plasma:
providing an RF matching network between the plasma chamber and the RF source, the RF matching network comprising:
at least one electronically variable capacitors (EVC), each EVC comprising discrete capacitors operably coupled in parallel, the discrete capacitors comprising fine capacitors and coarse capacitors, wherein each EVC has a variable total capacitance that is increased when the discrete capacitors are switched in and decreased when the discrete capacitors are switched out;
a control circuit operably coupled to the at least one EVC;
by the control circuit, determining a parameter related to the plasma chamber;
by the control circuit, determining, based on the determined parameter related to the plasma chamber, which of the coarse capacitors and which of the fine capacitors to have switched in to cause an impedance match;
by the control circuit, causing the determined coarse capacitors and the determined fine capacitors to be switched in;
wherein the increase of the variable total capacitance of the each EVC is achieved by switching in more of the coarse capacitors or more of the fine capacitors than are already switched in without switching out a coarse capacitor that is already switched in.
20. A semiconductor processing tool comprising:
a plasma chamber configured to deposit a material onto a substrate or etch a material from the substrate; and
an impedance matching network operably coupled to the plasma chamber, matching network comprising:
an RF input configured to operably couple to an RF source;
an RF output configured to operably couple to a plasma chamber;
at least one electronically variable capacitors (EVC), each EVC comprising discrete capacitors operably coupled in parallel, the discrete capacitors comprising fine capacitors and coarse capacitors, wherein each EVC has a variable total capacitance that is increased when the discrete capacitors are switched in and decreased when the discrete capacitors are switched out;
a control circuit operably coupled to the at least one EVC, the control circuit configured to:
determine a parameter related to the plasma chamber;
determine, based on the determined parameter related to the plasma chamber, which of the coarse capacitors and which of the fine capacitors to have switched in to cause an impedance match;
cause the determined coarse capacitors and the determined fine capacitors to be switched in;
wherein the increase of the variable total capacitance of each EVC is achieved by switching in more of the coarse capacitors or more of the fine capacitors than are already switched in without switching out a coarse capacitor that is already switched in.