Abstract: A method for preventing a substrate W from being contaminated by particles are provided, where the substrate is held horizontally, by means of holding means, in an environment having a specified cleanliness. The method comprises the step of flowing clean gas, by means of gas flowing means along the top surface of the substrate at a specific relative horizontal speed with respect to the top surface of the substrate, such that a laminar boundary layer, a transition layer, and/or turbulent boundary layer, of the clean gas are formed all over an entire area of the top surface of the substrate. In this method, the gas within the laminar boundary layer, a transition layer, and/or turbulent boundary layer, of clean gas may be considered as a viscous fluid. Thus, even if particles are existing and floating in the environment, where the substrate is disposed, and falling towards the substrate, the particles falling onto the substrate are blocked with the viscous fluid layer existing over the substrate.

Abstract: A substrate conveyance system for transporting a substrate from a substrate source to either one of a plurality of substrate destinations. The substrate conveyance system is characterized by a combination comprising a first transfer module including substrate holding means for holding the substrate thereon and for changing orientation of the substrate, and a first housing surrounding the substrate holding means; and a second transfer module including a second housing which can be connected with the first housing, and transfer means in the second housing for transferring the substrate to or from said substrate holding means in the first housing which is connected with the second housing. Efficient interbay or intrabay transportation of substrates is enabled by arranging the combinations in a checkerboard form. In the arrangement, the combination is used as the minimum unit.