Apparatus for processing substrate and method for detecting a presence of a focus ring on a stage

1. An apparatus for processing a substrate, the apparatus comprising:

a stage that includes a first placing surface on which a substrate is to be placed and a second placing surface that surrounds the first placing surface and on which a focus ring is to be placed;

a light source;

an optical assembly that adjustably focuses light from the light source substantially on a lower surface position, which is a position of a lower surface of the focus ring once placed on the second placing surface;

a light receiver that receives light from the lower surface position;

controller circuitry configured to detect at least one of a presence of the focus ring and an absence of the focus ring on the second placing surface, based on the light received by the light receiver;

a first through hole that is open on one end to the second placing surface and that penetrates through the stage; and

an optical channel structure that is disposed in the first through hole and through which the light passes, wherein

the optical assembly focuses light from the light source on the lower surface position via the optical channel structure disposed in the first through hole,

the light receiver receives reflected light from the lower surface position, and

the controller circuitry detects that the focus ring is present when an amount of received light exceeds a threshold, and detects that the focus ring is not present when the amount of received light is equal to or less than the threshold.

2. The apparatus according to claim 1 , wherein the optical channel structure is made of sapphire or quartz.

3. The apparatus according to claim 1 , wherein the optical channel structure seals the first through hole.

4. The apparatus according to claim 1 , wherein the optical channel structure is a lifter pin disposed in the first through hole to permit reciprocating movement along a direction orthogonal to the second placing surface.

5. The apparatus according to claim 4 , further comprising:

a drive assembly that controls the reciprocating movement of the lifter pin.

6. The apparatus according to claim 1 , further comprising:

another light receiver, wherein

the stage includes another first through hole with another optical channel structure, and

the another light receiver is disposed to receive light from the another optical channel.

7. The apparatus according to claim 1 , further comprising:

the stage includes another first through hole with another optical channel structure, and

the light receiver is configured to receive light from the optical channel structure and the another optical channel structure.

8. The apparatus according to claim 1 , wherein

the optical assembly includes an objective lens.

9. The apparatus according to claim 1 , further comprising:

the focus ring, the focus ring including two or more ring members partially overlapping with each other in a vertical direction, wherein

at least one of the two or more ring members includes a second through hole that communicates with the first through hole under a condition that the focus ring is disposed on the second placing surface, and that is closed by another of the two or more ring members, and

the optical assembly focuses light from the light source on a lower surface position, which is a position of a lower surface of another of the two or more ring members.

10. The apparatus according to claim 1 , further comprising:

an opposing structure that faces the second placing surface and is disposed over the second placing surface, the opposing structure being made of a same material as the focus ring.

11. The apparatus according to claim 10 , wherein the opposing structure is a shower head made of silicon.

12. A controller in an apparatus for processing a substrate, the controller comprising:

circuitry configured to

control an optical assembly to focus light from a light source substantially on a lower surface portion of a focus ring once disposed on a second placing surface of a stage, the second placing surface surrounding a first placing surface of the stage on which a substrate is to be placed;

receive light that returns through an optical channel structure disposed in a through hole formed in the stage, the through hole being opened to the second placing surface; and

detect at least one of a presence of the focus ring and an absence of the focus ring on the second placing surface, based on the light received, wherein

the circuitry is configured to detect that the focus ring is present when an amount of received light exceeds a threshold, and detects that the focus ring is not present when the amount of received light is equal to or less than the threshold.

13. The controller of claim 12 , wherein

the circuitry is configured to focus the light on the lower surface position via the optical channel structure.

14. The controller of claim 12 , wherein

the circuitry is further configured to drive a reciprocating movement of the optical channel structure, wherein the optical channel structure also serves as a lifting pin.

15. The controller of claim 12 , wherein

the stage includes another through hole with another optical channel structure, and

the circuitry is configured to receive light from the optical channel structure and the another optical channel structure, and detect a posture of the focus ring based on the light received from the optical channel structure and the another optical channel.