A system including a first linear bearing, a second linear bearing, a first shuttle, and a second shuttle. The first linear bearing is mounted in and disposed along a linear path of a transfer chamber. The second linear bearing is mounted on a same side of the transfer chamber as the first linear bearing and disposed along the linear path. The first shuttle rides on the first linear bearing and carries a first wafer. The second shuttle rides on the second linear bearing and carries a second wafer. The second shuttle moves independent of the first shuttle. During movement of the first shuttle and the second shuttle and during a first period of time, a first portion of the second shuttle is above the first shuttle such that the first portion of the second shuttle is vertically overlapping the first shuttle. During movement of the first shuttle and the second shuttle and during a second period of time, the first portion of the second shuttle is not above the first shuttle such that the first portion of the second shuttle is not vertically overlapping the first shuttle.