Patent ID: 7735451

Claim:
A substrate processing unit that includes: a substrate receiving ring to which a seal ring is mounted; a vertically movable substrate holder having a substrate fixing ring movable so as to hold a substrate by nipping a peripheral portion of the substrate between the substrate fixing ring and the seal ring to seal the peripheral portion of the substrate during processing of the substrate; and a temporary retaining section, that is mounted to the substrate receiving ring and positioned around the seal ring to temporarily retaining the substrate thereon while forming a space between the substrate and the seal ring; wherein the substrate receiving ring and the substrate fixing ring hold the substrate with its front surface facing downward; wherein the temporary retaining section is comprised of a plurality of temporary retaining pins which are biased upwardly by an elastic member, and which lower integrally with the substrate holder against the elastic force of the elastic member as the substrate holder lowers, and return to the original position as the substrate holder rises; wherein each of the temporary retaining pins has a head portion having a tapered surface provided so that, when placing the substrate on the temporary retaining pins, the tapered surface contacts a peripheral end surface of the substrate and effects positioning of the substrate, and having a retaining portion, projecting outwardly, for receiving thereon and retaining a peripheral lower surface of the substrate; and wherein the substrate holder having the substrate fixing ring, the seal ring, and the temporary retaining section having the temporary retaining pins, which each have the retaining portion, are structured and arranged such that the substrate can be vertically moved with the retaining portion retaining the substrate by vertically moving the substrate holder and such that a gap is formed between the retaining portion and the substrate by holding the substrate by nipping a peripheral portion of the substrate between the substrate fixing ring and the seal ring.