Analyzing issues for 300mm "backend" lithography

With 300mm wafer processing, expect to see a shift from conventional proxim ity aligners to more applications of 1x steppers for backend bump processin g. While passe for leading-edge frontend applications, 1xsteppers provide c lear advantages for semiconductor manufacturing's backend, in cost. of owne rship, automation, and processing. Advantages include broadband exposure, s uperior automatic alignment, and overlay performance. The 2 mum resolution capability of these tools is more than adequate for even difficult bump app lications. In addition, these tools' low 0.16 NA provides a large depth of focus (5.0 mum at the resolution limit of 2.0 mum), which is useful in imag ing thick resist.