NOVELTY - The device has a roller unit arranged slidable along a roller unit axis between a rolling position and a retracting position, where the roller unit transports a substrate in the rolling position. A cover unit (1) is arranged slidable along a cover unit axis (2) between a shielding position and an opening position, where the cover unit shields the roller unit against contamination by a substance present in a deposition system in the shielding position, and the roller unit axis and the cover unit axis are tilted with each other if the roller unit is in the retracting position.    USE - Roller drive device for transporting a substrate i.e. workpiece, in a deposition system e.g. CVD system, PVD system, PECVD system, APCVD system and MOCVD system, for manufacturing a photovoltaic device i.e. thin-film photovoltaic device (all claimed). Can also be used for photoelectric conversion device and thin film solar cell.    ADVANTAGE - The roller unit is arranged slidable along the roller unit axis between the rolling position and the retracting position, and the cover unit is arranged slidable along the cover unit axis between the shielding position and the opening position such that the cover unit shields the roller unit against contamination by the substance present in the deposition system in the shielding position if the roller unit is in the retracting position and only one cover unit is sufficient for shielding all roller unit required for transporting the substrate, thus allowing for simple and cost efficient shielding of the roller unit by the cover unit, preventing the contamination present on an O-ring sealing and avoiding the negative influence arising from substances used in the deposition system. The cover unit locks the receiving element and evacuates the receiving element to improve the sealing, thus improving lifetime of the roller unit.    DETAILED DESCRIPTION - The substance is selected from a group consisting of pyrophoric metal organic chemical, phosphine, diborane, silane, dimethylzinc, diethylzinc, zinc, zinc oxide and doped zinc oxide.    DESCRIPTION OF DRAWING(S) - The drawing shows a side view of a roller drive device with a cover unit in opening position.    Cover unit (1)    Cover unit axis (2)    Housing (3)    Motorized unit (4)    Cover head (5)    Quick change unit (6)    O-ring sealing (14)