Patent ID: 7971734

Claim:
Wafer boat for holding wafers in a spaced vertical arrangement during processing, said wafer boat comprising a plurality of vertically spaced holding positions for receiving and supporting corresponding ones of said wafers in a substantially horizontal orientation, wherein the holding positions can be accessed from a front side (F) of the wafer boat to allow for insertion and removal of a wafer, wherein at least one holding position comprises one or more back supports for engaging a wafer to support a back edge of said wafer and two lateral supports for engaging and supporting opposite lateral side portions of the wafer, and wherein the one or more back supports are disposed at a position that supports said wafer back edge a first predetermined distance vertically downward with respect to said two lateral supports, wherein a deflection value α represents a distance a centerline section of an inserted wafer deflects from the horizontal near the center due to gravity and a sagging value δ represents a distance by which the centerline section at the front side portion (F) of an inserted wafer sags from the horizontal due to gravity when the back edge and the two lateral side portions are located in the same horizontal plane, where δ>α, and wherein said first predetermined distance is chosen such that an amount a front side portion of an inserted wafer near the front side of the wafer boat sags due to gravity is limited to be not greater than α.