DETAILED DESCRIPTION An object of the invention, therefore, is to overcome the problems existing in the prior art, and to provide a wafer boat for a vertical furnace that can reduce stress in the wafer caused by the weight thereof with a usual wafer thickness even where the diameter of the wafer increases to about 30 cm (12 inches), and that is less susceptible to the effects of thermal stress.
According to one aspect of the invention, there is provided a wafer boat for use with vertical furnaces and having a structure for supporting a plurality of wafers one above another at an interval, the structure comprising: a plurality of support posts disposed upright and essentially perpendicular to principal surfaces of the wafers at positions around the wafers, and a plurality of supporting bars each extending laterally from each of the support posts and supporting a back surface of each of the wafers at positions thereof spaced apart from a center of the wafer by a distance corresponding to two-thirds of the radius of the wafer.
The wafer is (001)-wafer, and the support bars may support the wafer back at positions thereof along ?100!, i.
e.
, <100>, <010>, <100>, and <010>, or ?110!, i.
e.
, <110>, <110>, <110>, and <110>, crystal orientation.
The supporting bars may support the wafer back in point contact therewith, in line contact therewith, or in line plane contact therewith.
According to the invention, stress generated in a wafer due to the weight thereof, is reduced by supporting the back of the wafer at positions thereof spaced apart from the center of the wafer by a distance corresponding to two-thirds of the radius (r) of the wafer by the supporting bars each extending from each of a plurality of upright support posts essentially perpendicular to the principal surface of the wafer.
FIG.
3 shows the maximum stress, at a temperature of 1,200.
degree.
C.
, that is generated in a wafer having diameter of about 30 cm (12 inches) in size and having a thickness of 0
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Nonmetallic Processes 
