Method of stress relief in anti-reflective coated cap wafers for wafer level packaged infrared focal plane arrays

A method of reducing wafer bow induced by an anti-reflective coating on a cap wafer, the method comprising:

• providing the cap wafer having a planar side and an opposing cavity side, the cavity side including at least one recessed region and a dividing region on either side of the at least one recessed region;
• positioning a first shadow mask having at least one opening therein over the planar side of the cap wafer, the at least one opening dimensioned to extend beyond the at least one recessed region on the cap wafer;
• aligning the first shadow mask such that the at least one opening is positioned opposite the at least one recessed region;
• and
• depositing at least one layer of an anti-reflective coating material through the first shadow mask onto the planar side of the cap wafer to provide a discontinuous coating on the planar side, the discontinuous coating dimensioned and configured such that a wafer bow induced by the anti-reflective coating is less than 30 microns for an 8 inch diameter cap wafer.