Wafer flats convention, based on Image:Wafer flats convention.PNG

Conventional meaning of flats in semiconductor wafers. Red denotes material that has been removed.

Wafer orientation is the orientation of the crystallographic plane in which the crystal grew. Wafer type indicated the type of doping.
Primary flat - indicates crystallographic planes of high symmetry (usually the {110} face).
Secondary flat - it's position relative to Primary flat or it's absence is indicating the doping type and the orientation of wafer.

• Absence - p {111}
• 90° - p {100}
• 180° - n {100}
• 45° - n {111}