A robot which transports a substrate such as a liquid crystal panel generally has a cantilevered hand with a fork on which a substrate is placed. In recent years, as the substrate size increases, the fork inevitably elongates. The fork itself is made of lightweight rigid carbon so as to reduce its flexure. In contrast, flexure occurs at the hand front end due to its own weight and the substrate weight to a larger degree in a direction away from the robot main body, that is, the center of gravity in the hand. Therefore, in the process of transporting a substrate to a processing apparatus for the next process or to a cassette, the substrate may cause a fault upon interfering with the processing apparatus or the cassette or may be damaged. To prevent this, various techniques for correcting flexure of the hand have been proposed.
For example, Japanese Patent Laid-Open No. 7-99225 discloses a technique for rotating an eccentric cam using an air cylinder to pivot a hand about a supporting portion in placing a substrate on the hand, thereby correcting the tilt angle of the hand in a direction opposite to that of flexure which has occurred upon placing the substrate on the hand.
Also, International Publication No. 2005/004230 discloses a technique for rotating a screw to tilt a tilting table on which a hand is fixed in placing a substrate on the hand, thereby correcting the tilt angle of the hand.
Note that the amount of flexure of the hand changes depending on, for example, the weight of the transported substrate. In this respect, the technique disclosed in Japanese Patent Laid-Open No. 7-99225 assumes that the amount of flexure of the hand is constant. Therefore, this technique is inapplicable when substrates with different weights are transported. On the other hand, International Publication No. 2005/004230 discloses a method of storing in advance information concerning the amount of flexure of the hand due to the weight of each substrate, and correcting the tilt angle of the hand based on the type of transported substrate and the stored information. Unfortunately, it is cumbersome to store in advance information concerning the amount of flexure of the hand due to the weight of each substrate. Furthermore, it is impossible to correct the tilt angle of the hand in transporting a substrate whose information is not stored.