Patent attributes
A hand unit of a robot arm includes a U-shaped placement portion on which a semiconductor wafer is placed. The hand unit includes, on one end side of the placement portion, a first support portion configured to support the semiconductor wafer at a first support height and a second support portion configured to support the semiconductor wafer at a second support height, and includes, on the other end side of the placement portion, a third support portion configured to support the semiconductor wafer at the first support height and a fourth support portion configured to support the semiconductor wafer at the second support height. The hand unit further includes a first driving unit configured to move the third support portion and/or the fourth support portion forward and backward with respect to the first support portion and the second support portion.