Improvement of the Process Window at Structuring
Original Publication Date: 2002-Feb-01
Included in the Prior Art Database: 2003-Jul-23
For the evaluation of new technologies huge efforts are necessary to characterize the products behavior in litho and etch. This means that a so called focus exposure matrix (FEM) wafer has to be run. By varying the focus and the exposure dose on the wafer it is possible to measure the process windows for the critical dimension (CD) values and judge the quality of the patterns over the focus range. Currently the process window is mostly limited by semi- or iso- lated structures which can collapse before the meas- ured CD is out of specification. The problem is, that only some well known positions on the wafer can be covered. But there is always the risk that one critical position may be forgotten, because the pattern is not said to be very critical. It is possible, that some resist residues will remain within the pattern area or that pattern lift offs will occur. As a consequence the chip would not work any more. With the help of this method it is possible to avoid yield loss in the early state of the process development. It could also be done on a routine base to make sure that the influ- ences of later process changes do not affect the litho or etch process windows. Today there is no prior art for an automatic inline detection of critical patterns during the process win- dow evaluation.