Station Characteristics #
The main function of the wafer handling robot is transferring substrates from one location to another. These locations could be slots of a wafer carrier, the chuck of a process module or the pins of a prealigner. In any case the robot is supposed to ‘know’ the location and the geometry of the transfer location in order to perform the material transfer.
The Station is a metaphor for any location that the robot needs to interact with. It is implemented as a data object that encapsulates all parameters describing a wafer carrier (cassette) or a process module location.
In addition to the station mechanical characteristics, the robot needs to have dedicated motion parameters and delays in executing the material handling algorithms. These parameters are also stored among the station data members.
Each station is identified with a single character from the alphabet which represents the station name. The names are case sensitive which results in a maximum number of 52 stations (26 capital and 26 small letter names).
The station parameters are summarized below in two categories: Cassette parameters and Motion Parameters
Cassette Features #
The Station Coordinates are the main station parameter – they represent the reference position which is used by the robot to calculate all derivative coordinates necessary for it motion algorithm.
The other features the cassette pitch (defining the distance between the slots of the cassette). Due to use of this parameter as a multiplier in the calculations, its dimension has higher resolution (0.00001”). This avoids the effect of the rounding error that gets multiplied by the slot number.
Another cassette feature is the number of slots in a cassette. It should range between 1 and 200.
The cassette depth defines the distance that the wafer has to travel in order to get out of the cassette. This parameter defines the ‘approach’ position of the cassette. Typically this parameter is set to 0 for radial cassettes and to the wafer size for non-radial cassettes.
The table below describes the cassette features in detail:
(Missing table content from Software Manual?)
Algorithm and Motion #
The station parameters include definition for motion parameters such as speed and acceleration for the execution of the material handling algorithms. In addition, the algorithm settings include the distances for the pick-up/drop-off motion, the end effector to be used, the need to check for confirmation of the wafer presence with the vacuum sensor and others. The use of these parameters is application specific.
Another algorithm that benefits from the station parameters is the wafer mapping (scanning). The station includes parameters such as the reference scanning position, the scanning motion parameters and the wafer thickness.
The detailed description of the algorithm control station parameters is included in the table below:
(Missing table content from Software Manual?)
Parameter Management #
The robot firmware allocates space for 52 stations. Their parameters are stored persistently in a file called STATIONS.DAT.The file is in text format and can be backed up on the host if needed.
There is a dedicated command called READS which reads the file contents and updates the internal data structures. This operation is executed automatically upon firmware startup.
Stations Teaching #
The station teaching can be done in two different ways:
- The station pickup coordinates can be copied from the current robot coordinates using the
TEACHcommand. - The station parameters (including the pickup positions) can be set using the
SPARcommand multiple times.
The first method is suitable for scenarios where the robot is jogged to the desired position. This method works if the teach point is clearly identified and the robot position can be adjusted accordingly.
The second method is more suitable when a dedicated utility is used to calibrate or modify the station parameters.