given the desired size and spacing of emitter tips in feds traditional photolithographic techniques suffer from significant depth of focus problems and the need for a high level of planarity in fabricated wafer structures is paramount in contrast embodiments of the present invention provide the advantage of improved depth of focus relative to traditional transmission photolithography as is known by those skilled in the art as such the base layer 36 may be a relatively inexpensive glass plate in which the planarity of the plate is not a critical design element phase shifting lithography has been used in certain applications to form sub micron features in highly integrated circuits but such applications have typically required multiple exposure and position shifting of masks in order to form desired feature sizes and shapes for example use of phase shifting masks and techniques is described in u s pat no 5 308 741 to kemp incorporated herein by reference methods of fabricating phase shifting reticles or masks are described in u s pat no 5 194 344 to cathey et al and in u s pat no 5 194 346 to rolfson et al each of which is incorporated herein by reference because the chemical properties of photoresist materials do not change linearly with light energy exposure multiple exposure photolithography is more difficult to control and has reduced tolerance as known to those skilled in the art in contrast to currently employed phase shifting lithographic apparatus and techniques embodiments of the present invention provide phase shifting masks and microelectronic fabrication techniques that require only a single light exposure u2014 that is the lithographic patterning process includes light exposure for no more than a single substantially continuous time interval those skilled in the art will appreciate the numerous advantages this provides including improved lithographic.