Plasma processing apparatus and method

1. A plasma processing method in a plasma processing apparatus, wherein the plasma processing apparatus includes

a process container that forms a process space to accommodate a target substrate,

a vacuum pump connected to an exhaust port of the process container to vacuum-exhaust gas from inside the process container,

a first electrode and a second electrode disposed opposite each other within the process container, the first electrode being an upper electrode and the second electrode being a lower electrode and configured to support the target substrate through a mount face,

a first radio frequency (RF) power supply configured to apply a first RF power to the first electrode or the second electrode,

a second RF power supply configured to apply a second RF power to the second electrode, the second RF power having a frequency lower than that of the first RF power,

a direct current (DC) power supply configured to apply a DC voltage to the first electrode,

a process gas supply source configured to supply a process gas into the process container, and

a conductive member disposed above the second electrode, as a ring around the first electrode, to be exposed to plasma within the process space, and

wherein the plasma processing method includes executing an etching process that comprises:

supplying an etching gas as the process gas into the process container in which the target substrate is supported on the second electrode;

applying an RE power for plasma generation as the first RE power and applying an RE power for ion attraction as the second RE power to turn the etching gas into plasma and to subject the target substrate to etching;

applying a negative DC voltage to the first electrode during the etching to increase an absolute value of self-bias on the first electrode; and

releasing DC electron current generated by the negative DC voltage to ground through plasma and the conductive member, by using a first state where the conductive member is connected to a ground potential portion.

2. The plasma processing method according to claim 1 , wherein a surface of the first electrode facing the second electrode is made of a silicon-containing substance.

3. The plasma processing method according to claim 1 , wherein the negative DC voltage is set to increase a thickness of a plasma sheath formed below the first electrode and thereby to shrink plasma.

4. The plasma processing method according to claim 1 , wherein the negative DC voltage is set to control a quantity of electrons generated below the first electrode and acceleration of electrons toward the target substrate.

5. The plasma processing method according to claim 1 , wherein plasma processing method further includes executing a cleaning process after the etching process, the cleaning process comprising:

switching the conductive member from the first state, to a second state where the conductive member is connected to a negative potential portion or set in floating;

supplying a cleaning gas as the process gas into the process container; and

applying an RF power for cleaning plasma generation as the first RF power to turn the cleaning gas into plasma and to subject the conductive member to cleaning.

6. The plasma processing method according to claim 5 , wherein a negative terminal of the DC power supply is connected to the first electrode in the etching process, and the negative terminal of the DC power supply is connected to the conductive member in place of the first electrode in the cleaning process.

7. The plasma processing method according to claim 6 , wherein a positive terminal of the DC power supply is connected to the first electrode in the cleaning process.

8. The plasma processing method according to claim 7 , wherein the positive terminal of the DC power supply is grounded and is connected to the conductive member in the etching process.

9. The plasma processing method according to claim 1 , wherein the RF power for plasma generation is applied to the first electrode.

10. The plasma processing method according to claim 9 , wherein

the first electrode includes outer and inner upper electrodes, which are electrically insulated from each other, disposed on a peripheral side and a central side, respectively, in a radial direction, and connected to the first RF power supply, to define outer and inner RF discharge regions, respectively,

the inner upper electrode includes gas passages formed therein, such that the gas passages are composed of outer and inner gas passages, which are isolated from each other, disposed on a peripheral side and a central side, respectively, in a radial direction, and connected to the process gas supply source, to define outer and inner gas delivery regions, respectively, and

the etching process comprises:

setting a spatial distribution of plasma density by applying the RF power for plasma generation to the outer and inner RF discharge regions at a predetermined application ratio therebetween; and

setting a spatial distribution of radical density by supplying the etching gas to the outer and inner gas delivery regions at a predetermined flow rate ratio therebetween.

11. The plasma processing method according to claim 10 , wherein the etching process comprises performing control on the spatial distribution of plasma density and control on the spatial distribution of radical density, substantially independently of each other.

12. The plasma processing method according to claim 10 , wherein the DC, power supply is connected to both of the outer and inner upper electrodes, or connected to at least the inner upper electrode.