Ion generator and ion implanter

1. An ion generator comprising:

an arc chamber which defines a plasma generation space; and

a cathode which emits thermoelectrons toward the plasma generation space, wherein

the arc chamber includes a box-shaped main body which includes an opening in at least part of a front side of the main body, and a slit member which is mounted to cover the opening of the front side of the main body and provided with a front slit for extracting ions,

an inner surface of the main body which is exposed to the plasma generation space is made of a first refractory metal material,

the slit member includes an inner member made of graphite, and an outer member made of a second refractory metal material,

the outer member includes an outer surface which is exposed to an outside of the arc chamber, and

the inner member includes an inner surface which is exposed to the plasma generation space and an opening portion which forms the front slit extending from the inner surface of the inner member to the outer surface of the outer member.

2. The ion generator according to claim 1 , wherein

the outer member is provided with an outer opening for forming the front slit, and

an opening size of the outer opening is larger than an opening size of the inner opening.

3. The ion generator according to claim 2 , wherein

the inner member includes a tapered surface which is provided at an edge of the inner opening such that an opening size increases from an inside toward an outside of the arc chamber, and

an edge of the outer opening is provided at a position farther from a center of the front slit than a virtual plane obtained by extending the tapered surface toward the outside of the arc chamber.

4. The ion generator according to claim 2 , wherein

the inner member includes a protrusion portion which protrudes toward the outside of the arc chamber on a periphery of the inner opening, and

an edge of the outer opening is provided along an outer periphery of the protrusion portion of the inner member.

5. The ion generator according to claim 4 , wherein a position of an outer surface of the outer member on a periphery of the outer opening in a thickness direction from the inside toward the outside of the arc chamber coincides with a front surface of the protrusion portion of the inner member which is exposed to the outside of the arc chamber.

6. An ion implanter comprising:

an ion generator that comprises an arc chamber which defines a plasma generation space, and a cathode which emits thermoelectrons toward the plasma generation space, wherein

the arc chamber includes a box-shaped main body which includes an opening in at least part of a front side of the main body, and a slit member which is mounted to cover the opening of the front side of the main body and provided with a front slit for extracting ions,

an inner surface of the main body which is exposed to the plasma generation space is made of a first refractory metal material,

the slit member includes an inner member made of graphite, and an outer member made of a second refractory metal material,

the outer member includes an outer surface which is exposed to an outside of the arc chamber, and

the inner member includes an inner surface which is exposed to the plasma generation space and an opening portion which forms the front slit extending from the inner surface of the inner member to the outer surface of the outer member.

7. The ion implanter according to claim 6 , wherein the first refractory metal material includes the same refractory metal element as the second refractory metal material.

8. The ion implanter according to claim 6 , wherein

the inner opening portion includes an exposed portion which is exposed to the outside of the arc chamber, and

the outer member surrounds the exposed portion.

9. The ion implanter according to claim 8 , wherein at least part of the outer member faces the inner member in a thickness direction from the inside toward the outside of the arc chamber.

10. An ion implanter comprising:

a beam generation unit that comprises an ion generator to generate multiply charged ions, and that generates an ion beam of the multiply charged ions extracted from the ion generator;

a beam acceleration unit that accelerates the ion beam to obtain a high energy ion beam of 1 MeV or more; and

a substrate processing unit in which the high-energy ion beam is implanted into a substrate, wherein

the ion generator includes an arc chamber which defines a plasma generation space, and a cathode which emits thermoelectrons toward the plasma generation space,

the arc chamber includes a box-shaped main body which includes an opening in at least a part of a front side of the main body, and a slit member which is mounted to cover the opening of the front side of the main body and provided with a front slit for extracting ions,

an inner surface of the main body which is exposed to the plasma generation space is made of a refractory metal material, and

an inner surface of the slit member which is exposed to the plasma generation space is made of graphite.

11. The ion implanter according to claim 10 , wherein the beam acceleration unit comprises a linear accelerator.

12. The ion implanter according to claim 10 , wherein the beam acceleration unit comprises a plurality of linear accelerators.

13. The ion implanter according to claim 10 , wherein the beam acceleration unit accelerates the ion beam to obtain a high energy ion beam of 4 MeV or more.

14. The ion implanter according to claim 10 , wherein the ion generator generates the multiply charged ions of at least one of boron, phosphorus, and arsenic.