Restricted capacitor switching

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, the matching network comprising:
• a radio frequency (RF) input configured to operably couple to an RF source;
• an RF output configured to operably couple to the plasma chamber;
• a first electronically variable capacitor (EVC) comprising discrete capacitors configured to be switched in and out to alter a first capacitance of the first EVC;
• a second EVC comprising discrete capacitors configured to be switched in and out to alter a second capacitance of the second EVC;
• and
• a control circuit operably coupled to the first and second EVCs, the control circuit configured to:
• determine or receive a reflection parameter value at the RF input or the RF output;
• stop the altering of the first capacitance and the second capacitance when the reflection parameter value is at or below a first reflection value;
• cause a limited altering of the first capacitance and the second capacitance to pursue an impedance match when the reflection parameter value is (a) at or above a second reflection value and (b) at or below the third reflection value, the limited altering allowing only a predetermined number of predetermined discrete capacitors to switch in or out;
• and
• cause an unlimited altering of the first capacitance and the second capacitance to pursue an impedance match when the reflection parameter value is at or above a third reflection value, the unlimited altering allowing any discrete capacitor of the first or second EVC to switch in or out.

A method of matching an impedance comprising:

• operably coupling a radio frequency (RF) input of a matching network to an RF source;
• operably coupling an RF output of the matching network to a plasma chamber, the plasma chamber comprising (a) a first electronically variable capacitor (EVC) comprising discrete capacitors configured to be switched in and out to alter a first capacitance of the first EVC, and (b) a second EVC comprising discrete capacitors configured to be switched in and out to alter a second capacitance of the second EVC;
• and
• determining or receiving a reflection parameter value at the RF input or the RF output;
• stopping the altering of the first capacitance and the second capacitance when the reflection parameter value is at or below a first reflection value;
• causing a limited altering of the first capacitance and the second capacitance to pursue an impedance match when the reflection parameter value is (a) at or above a second reflection value and (b) at or below the third reflection value, the limited altering allowing only a predetermined number of predetermined discrete capacitors to switch in or out;
• and
• causing an unlimited altering of the first capacitance and the second capacitance to pursue an impedance match when the reflection parameter value is at or above a third reflection value, the unlimited altering allowing any discrete capacitor of the first or second EVC to switch in or out.

A method of manufacturing 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
• coupling an impedance matching circuit between a radio frequency (RF) source and the plasma chamber, the impedance matching circuit comprising:
• a radio frequency (RF) input configured to operably couple to an RF source;
• an RF output configured to operably couple to a plasma chamber;
• a first electronically variable capacitor (EVC) comprising discrete capacitors configured to be switched in and out to alter a first capacitance of the first EVC;
• a second EVC comprising discrete capacitors configured to be switched in and out to alter a second capacitance of the second EVC;
• and
• a control circuit operably coupled to the first and second EVCs, the control circuit configured to:
• determine or receive a reflection parameter value at the RF input or the RF output;
• stop the altering of the first capacitance and the second capacitance when the reflection parameter value is at or below a first reflection value;
• cause a limited altering of the first capacitance and the second capacitance to pursue an impedance match when the reflection parameter value is (a) at or above a second reflection value and (b) at or below the third reflection value, the limited altering allowing only a predetermined number of predetermined discrete capacitors to switch in or out;
• and
• cause an unlimited altering of the first capacitance and the second capacitance to pursue an impedance match when the reflection parameter value is at or above a third reflection value, the unlimited altering allowing any discrete capacitor of the first or second EVC to switch in or out.