Plasma processing apparatus

1. A plasma processing apparatus for applying a process to a workpiece, by supplying an electromagnetic wave in a VHF band of 100 MHz or higher to a chamber to form a plasma, the plasma processing apparatus comprising:

a ceiling wall that defines a part of the chamber and is at a ground potential; and

a central conductor disposed in a hole formed in a center of the ceiling wall via a dielectric window, the central conductor being configured to apply the electromagnetic wave; wherein

a central position of the central conductor substantially coincides with a central position of a stage on which the workpiece is placed,

an outer diameter of the central conductor and a size of the hole of the ceiling wall are defined such that a cutoff frequency of a coaxial path composed of the central conductor and the ceiling wall is greater than a frequency of the electromagnetic wave,

the dielectric window is provided at least at an end of the coaxial path, and

the dielectric window includes a first solid dielectric layer that separates an interior of the coaxial path from a plasma space.

2. The plasma processing apparatus according to claim 1 , wherein the outer diameter of the central conductor and the size of the hole of the ceiling wall are defined such that the cutoff frequency of the coaxial path is equal to or greater than twice the frequency of the electromagnetic wave.

3. The plasma processing apparatus according to claim 1 , wherein a coaxial path length of the coaxial path is 20 mm or more.

4. The plasma processing apparatus according to claim 1 , wherein

the dielectric window is provided within the coaxial path, and

the dielectric window includes a second solid dielectric layer or a space layer, each of the second solid dielectric layer and the space layer having a lower relative permittivity than the first solid dielectric layer.

5. The plasma processing apparatus according to claim 4 , wherein the space layer is a vacuum space.

6. The plasma processing apparatus according to claim 1 , wherein the first solid dielectric layer is a material of alumina, aluminum nitride, or quartz, or a material having a lower relative permittivity than alumina, aluminum nitride, or quartz.

7. The plasma processing apparatus according to claim 1 , wherein a thickness of the first solid dielectric layer is less than or equal to a one fourth of a coaxial path length of the coaxial path.

8. The plasma processing apparatus according to claim 1 , wherein at least one of the ceiling wall and a side portion of the chamber includes an electromagnet.

9. A plasma processing apparatus for applying a process to a workpiece, by supplying an electromagnetic wave in a VHF band of 100 MHz or higher to a chamber to form a plasma, the plasma processing apparatus comprising:

a ceiling wall that defines a part of the chamber and is at a ground potential; and

a central conductor disposed in a hole formed in a center of the ceiling wall via a dielectric window, the central conductor being configured to apply the electromagnetic wave; wherein

a central position of the central conductor substantially coincides with a central position of a stage on which the workpiece is placed,

an outer diameter of the central conductor and a size of the hole of the ceiling wall are defined such that a cutoff frequency of a coaxial path composed of the central conductor and the ceiling wall is greater than a frequency of the electromagnetic wave,

the central conductor has an I-shaped longitudinal cross-sectional shape or a T-shaped longitudinal cross-sectional shape,

in a case in which the central conductor has the I-shaped longitudinal cross-sectional shape, the outer diameter of the central conductor is a diameter of a shaft portion of the central conductor, and

in a case in which the central conductor has the T-shaped longitudinal cross-sectional shape, the outer diameter of the central conductor is a diameter of a widened portion of the central conductor.

10. The plasma processing apparatus according to claim 9 , wherein the outer diameter of the central conductor and the size of the hole of the ceiling wall are defined such that the cutoff frequency of the coaxial path is equal to or greater than twice the frequency of the electromagnetic wave.

11. The plasma processing apparatus according to claim 9 , wherein a coaxial path length of the coaxial path is 20 mm or more.

12. The plasma processing apparatus according to claim 9 , wherein the dielectric window is provided at least at an end of the coaxial path, and the dielectric window includes a first solid dielectric layer that separates an interior of the coaxial path from a plasma space.

13. The plasma processing apparatus according to claim 12 , wherein

the dielectric window is provided within the coaxial path, and

the dielectric window includes a second solid dielectric layer or a space layer, each of the second solid dielectric layer and the space layer having a lower relative permittivity than the first solid dielectric layer.

14. The plasma processing apparatus according to claim 13 , wherein the space layer is a vacuum space.

15. The plasma processing apparatus according to claim 12 , wherein the first solid dielectric layer is a material of alumina, aluminum nitride, or quartz, or a material having a lower relative permittivity than alumina, aluminum nitride, or quartz.

16. The plasma processing apparatus according to claim 12 , wherein a thickness of the first solid dielectric layer is less than or equal to a one fourth of a coaxial path length of the coaxial path.

17. The plasma processing apparatus according to claim 9 , wherein at least one of the ceiling wall and a side portion of the chamber includes an electromagnet.