PROCEEDINGS ARTICLE | March 21, 2012
Proc. SPIE. 8323, Alternative Lithographic Technologies IV
KEYWORDS: Electron beam lithography, Electron beams, Backscatter, Metals, Control systems, Optical alignment, Electron beam direct write lithography, Photoresist processing, Semiconducting wafers, Overlay metrology
Techniques to appropriately control the key factors for a character projection (CP) based electron beam direct writing
(EBDW) technology for mass production are shown and discussed. In order to achieve accurate CD control, the CP
technique using the master CP is adopted. Another CP technique, the Packed CP, is used to obtain suitable shot count.
For the alignment on the some critical layers which have the normally an even surface, the alignment methodology differ
from photolithography is required. The process that etches the SiO2 material in the shallow trench isolation is added and
then the alignment marks can be detected using electron beam even at the gate layer, which is normally on an even
surface. The proximity effect correction using the simplified electron energy flux model and the hybrid exposure are used
to obtain enough process margins. As a result, the sufficient CD accuracy, overlay accuracy, and yield are obtained on the
65 nm node device. The condition in our system is checked using self-diagnosis on a regular basis, and scheduled
maintenances have been properly performed. Due to the proper system control, more than 10,000 production wafers have
been successfully exposed so far without any major system downtime. It is shown that those techniques can be adapted
to the 32 nm node production with slight modifications. For the 14 nm node and beyond, however, the drastic increment
of the shot count becomes more of a concern. The Multi column cell (MCC) exposure method, the key concept of which
is the parallelization of the electron beam columns with a CP, can overcome this concern. It is expected that by using the
MCC exposure system, those techniques will be applicable to the rapid establishment for the 14 nm node technology.
