Patent GB-1358513-A (GB)
Title: Pneumatic transport system for flat objects
IPC: H01L21/677
Filed: 1972-05-22
Abstract: 1358513 Stacking, and de-stacking, flat objects on a pneumatic transport system INTERNATIONAL BUSINESS MACHINES CORP 22 May 1972 [1 June 1971] 23904/72 Headings B8A and B8C A system for transporting flat objects, such as semi-conductor wafers 14, 16 with integrated circuits respectively on their upper and lower surfaces, comprises an air-slide 10 which is divided into two channels 20, 22 controlled by gates 38, 28 respectively and which is provided with four rows of apertures 46, 48, 50, 52 through which air can be selectively forced to provide a longitudinal air-flow for the air-slide 10 in one direction or the other, means being provided for stacking the wafer 14 on top of the wafer 16 in the course of their travel in one direction along the air path, and for unstacking such a pair of wafers during the course of their travel along the air-slide in the opposite direction. The apertures in the rows 46, 50 and 48, 52 are angled to provide air-flows from right to left and left to right respectively and are connected to respective manifolds 56, 54. Wafer arresting means, for stacking, and unstacking, the pairs of wafers comprises vertically movable pairs of pins 62 and 84 respectively, a section 66 of the main airslide 10 having apertures 68 for providing vertical air-jets 70. As shown, compressed air, Figs. 1, 4, is fed to manifold 54 to provide an air-slide from right to left and an independent air inlet 89, Fig. 2A, supplies air for the vertical jets 70. A carrier 34, at the end of the channel 20 is indexed downwardly so that a wafer 16 floats into the channel 20 beneath a gate 38, which is simultaneously raised, and into the main channel 32 of the air-slide 10 where it passes beneath the arresting pins 84 which are in their raised position. As the wafer 16 passes over the section 66, it is lifted upwardly by the air jets 70 before being detained by the arrester pins 62, which are located in their lowered position, and dropping back to its initial floating level. If desired, the jets 70 could be turned off during the passage of the wafer to the detaining pins 62. The carrier 24 at the end of the channel 22 is then indexed downwardly, the gate 38 is closed, and the gate 28 opened so that a wafer 14 from the carrier 24 floats along the main channel 32 of the air-slide 10 and is lifted by the jets 70 and arrested by the pins 62 to settle down gently upon the wafer 16 therebelow, Fig. 2B. The pins 62 are then raised and the pair of stacked wafers 12, 16 then being transported on the air line 10 into a vacant slot 90 in a carrier 74. The carrier 74 is inched upwardly to receive the next pair of stacked wafers. After the carrier 74, preferably made of quartz, has been completely loaded, an operation such as oxidation, or diffusion, is carried out on the wafers after which the air supply is switched to the manifold 56 to provide an air-slide 10 with a flow from right to left, air to the jets 70 is switched off, and the pins 62, 84 are raised and lowered respectively. Each stack of wafers 12, 16 moves along the air-slide 10 from right to left and is arrested by the pins 84 where an air-operated, pick-up 88 lifts and holds the wafer 12 while the wafer 16 proceeds along the air-slide 10 as the pins 84 are raised and passes into the channel 20 as the gate 38 is opened, the carrier 34 being indexed to provide a slot to receive the wafer 16. The gate 38 is then closed and the gate 28 is opened while the wafer 12 is released by the pick-up 88 to travel into the channel 22 for loading into the carrier 24.