Processing unit

Abstract

In a technology for processing a workpiece with a processing liquid while rotating an inner cup inside an outer cup, the aim is to prevent contamination of the inner cup by the processing liquid, thereby preventing contamination of the workpiece by foreign matter caused by the processing liquid and improving productivity. [Solution] The inner cup is a bottomed cylindrical cup rotatably installed inside the outer cup, and the inner cup is provided with a mounting surface for placing a workpiece along its inner bottom surface. The cylindrical side wall of the inner cup is composed of two parts: an upper and a lower part. The upper part of the side wall has an annular projection that protrudes inward, and the lower surface of this projection and the inner bottom surface form a transverse groove that extends over the entire circumferential direction. In addition, the lower part of the side wall has a through hole that penetrates from the transverse groove to the outer surface of the side wall and leads into the outer cup.

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