Substrate support unit and substrate treating apparatus having the same

An apparatus for supporting a substrate, the apparatus comprising:

• a rotatable spin head configured to support the substrate;
• a hollow shaft connected with the spin head and configured to transmit torque to the spin head;
• a nozzle assembly disposed in an interior space of the spin head so as not to rotate and configured to supply a treatment liquid to a backside of the substrate;
• and
• a sealing member configured to seal a gap between the spin head and the nozzle assembly using a magnetic fluid,
• wherein the sealing member includes:
• a magnetic body installed on a first member, the first member being one of a main body of the nozzle assembly and the spin head configured to surround the main body;
• pole pieces installed around the magnetic body and configured to transmit a magnetic force of the magnetic body to a second member, the second member being the other of the main body of the nozzle assembly and the spin head;
• and
• a magnetic fluid provided between the second member and the pole pieces and configured to seal a gap between the second member and the pole pieces by the magnetic force transmitted by the pole pieces.