a method for wafer alignment includes forming a first alignment circuit within a first semiconductor wafer ; the first alignment circuit is configured to emit an optical signal . next , the first alignment circuit is activated upon receiving a first activation signal from a wafer bonding tool then the optical signal is sent to a second alignment circuit in a second semiconductor wafer in overlapping relation to the first semiconductor wafer . the second alignment circuit transmits a second activation signal to the wafer bonding tool and consequently the wafer bonding tool initiates an alignment technique between the first and second semiconductor wafers . the alignment technique uses the first and second alignment circuits for optical alignment .