Wafer processing apparatus having dust proof function

A wafer processing apparatus including a mini-environment portion having a chamber therein and configured to transfer a wafer between a clean box having a housing with an opening configured to be closed by a lid to house the wafer in the housing and the chamber, wherein the housing has a flange extending from the opening of the clean box toward a side opposite to the opening and in a surface plane direction of the opening of the clean box around an entire perimeter of the opening of the clean box, said apparatus comprising:

• a first opening portion formed on a wall of the chamber, for communicating with an outside of the chamber, the wall opposing to the opening of the clean box which allows loading or unloading the wafer between the clean box and the chamber;
• and
• a door configured to close said first opening portion when the wafer is not transferred and opening the first opening portion when the wafer is transferred,
• wherein when the wafer transferring operation is performed, the clean box is fixed to overlap the flange of the clean box over an outside surface of the wall on which the first opening portion is formed with a first clearance formed at the perimeter of said first opening portion, the first clearance being defined by a predetermined constant distance along an entire perimeter of the opening of the clean box between a chamber side surface of the flange and the outside surface of the chamber wall on which the first opening portion is formed,
• wherein the clean box is settable in a manner where an outermost peripheral edge of the opening of the clean box is positioned closer to a center of said first opening portion in a direction parallel to a plane of the chamber wall than a peripheral edge of said first opening portion in the direction parallel to the plane of the chamber wall so that a part of airflow from the inside of the chamber at the peripheral edge of said first opening portion in a direction normal to said first opening portion directly hits the chamber side surface of the flange to direct an airflow in the direction along the chamber wall;
• wherein when the lid held by the door has been inserted into said first opening portion to close said first opening portion until the door has closed said first opening portion, a second clearance is formed between the door and a perimeter of said first opening portion, the second clearance communicating with the first clearance,
• and wherein an inside of the chamber is capable of communicating with an outside of the chamber through the first and second clearances.