Plasma potential adjustment circuit

1 . A method of adjusting sheath potential of a plasma at a substrate, the method comprising:

applying pulsed direct current (DC) plasma power to an upper plasma electrode above the substrate and in contact with the plasma using a pulsed DC power supply while applying pulsed DC bias power to the substrate;

measuring electric potential of the plasma produced by the pulsed DC plasma power and the pulsed DC bias power to obtain time-resolved electric potential information of the plasma; and

adjusting an electric potential profile at the upper plasma electrode based on the time-resolved electric potential information of the plasma to adjust the sheath potential of the plasma at the substrate by adjusting a voltage shape of the pulsed DC plasma power using a potential adjustment circuit coupled between the pulsed DC power supply and the upper plasma electrode.

2 . The method of claim 1 , wherein adjusting the electric potential profile at the upper plasma electrode of the pulsed DC plasma power results in a substantially flat sheath potential profile.

3 . The method of claim 1 ,

wherein the time-resolved electric potential information includes a plasma potential profile and a substrate potential profile, and

wherein adjusting the electric potential profile at the upper plasma electrode comprises minimizing the difference between a slope of the plasma potential profile and a slope of the substrate potential profile.

4 . The method of claim 1 , wherein the pulsed DC plasma power comprises a series of positive DC pulses.

5 . The method of claim 1 , wherein the pulsed DC plasma power and the pulsed DC bias power have the same pulse frequency and are pulsed in phase with one another.

6 . The method of claim 1 , wherein adjusting the electric potential profile comprises adjusting capacitance along a transmission path of the pulsed DC plasma power.

7 . The method of claim 1 , wherein adjusting the electric potential profile comprises adjusting inductance along a transmission path of the pulsed DC plasma power.

8 . The method of claim 1 , wherein adjusting the electric potential profile comprises adjusting resistance along a transmission path of the pulsed DC plasma power.

9 . The method of claim 1 ,

wherein applying the pulsed DC plasma power comprises generating a substantially square waveform using the pulsed DC power supply, and

wherein adjusting the voltage shape of the pulsed DC plasma power comprises modifying the substantially square waveform using only passive variable components of the potential adjustment circuit.

10 . A plasma system comprising:

an upper plasma electrode configured to be in contact with a plasma;

a substrate holder disposed below the upper plasma electrode and configured to support a substrate in contact with the plasma;

at least one pulsed direct current (DC) power supply configured to deliver pulsed DC plasma power to the upper plasma electrode and pulsed DC bias power to the substrate holder; and

a potential adjustment circuit coupled along a transmission path of the pulsed DC plasma power between the upper plasma electrode and the at least one pulsed DC power supply, the potential adjustment circuit being configured to adjust an electric potential profile at the upper plasma electrode by adjusting a voltage shape of the pulsed DC plasma power using only variable passive components of the potential adjustment circuit.

11 . The plasma system of claim 10 , further comprising:

at least one sensor configured to measure electric potential of the plasma produced by the pulsed DC plasma power and the pulsed DC bias power to obtain time-resolved electric potential information of the plasma, the potential adjustment circuit being configured to adjust the electric potential profile based on the time-resolved electric potential information of the plasma.

12 . The plasma system of claim 11 ,

wherein the time-resolved electric potential information of the plasma comprises a plasma potential profile and a substrate potential profile,

wherein the at least one sensor comprises a plasma potential sensor configured to measure the plasma potential profile and a substrate potential sensor configured to measure the substrate potential profile, and

wherein the potential adjustment circuit is further configured to adjust the electric potential profile by minimizing the difference between a slope of the plasma potential profile and a slope of the substrate potential profile.

13 . The plasma system of claim 10 , wherein the plasma system is a capacitively coupled plasma (CCP) plasma system, the upper plasma electrode being an upper electrode of the CCP plasma system.

14 . The plasma system of claim 10 , further comprising:

a source power coupling element configured to generate the plasma through an intervening dielectric material using applied source power, the plasma system being an inductively coupled plasma (ICP) plasma system.

15 . The plasma system of claim 10 , wherein the potential adjustment circuit is an RLC circuit comprising one or more of variable capacitance, variable inductance, and variable resistance.

16 . The plasma system of claim 15 , wherein the potential adjustment circuit comprises variable capacitance, variable resistance, and fixed inductance.

17 . A plasma system comprising:

an upper plasma electrode configured to be in contact with a plasma;

a substrate holder disposed below the upper plasma electrode and configured to support a substrate in contact with the plasma;

at least one pulsed direct current (DC) power supply;

a potential adjustment circuit coupled between the upper plasma electrode and the at least one pulsed DC power supply;

at least one sensor; and

a controller operatively coupled to the potential adjustment circuit and the at least one pulsed DC power supply, the controller comprising a processor and a non-transitory computer-readable medium storing a program including instructions that, when executed by the processor, perform a method comprising:

using the at least one pulsed DC power supply to apply pulsed DC plasma power to the upper plasma electrode and to apply pulsed DC bias power to the substrate;

using the at least one sensor to measure electric potential of the plasma produced by the pulsed DC plasma power and the pulsed DC bias power to obtain time-resolved electric potential information of the plasma; and

using the potential adjustment circuit to adjust an electric potential profile at the upper plasma electrode based on the time-resolved electric potential information of the plasma to adjust a sheath potential of the plasma at the substrate by adjusting a voltage shape of the pulsed DC plasma power.

18 . The plasma system of claim 17 , wherein adjusting the electric potential profile at the upper plasma electrode results in a substantially flat sheath potential profile.

19 . The plasma system of claim 17 ,

wherein the time-resolved electric potential information of the plasma includes a plasma potential profile and a substrate potential profile, and

wherein adjusting the electric potential profile at the upper plasma electrode comprises minimizing the difference between a slope of the plasma potential profile and a slope of the substrate potential profile.

20 . The plasma system of claim 17 , wherein adjusting the electric potential profile comprises adjusting one or more of capacitance, inductance, and resistance along a transmission path of the pulsed DC plasma power.