As the optical lithography advances into the sub-30nm technology node, the various candidates of lithography have
been discussed. Double dipole lithography (DDL) has been a primary lithography candidate due to the advantages of a
simpler process and a lower mask cost compared to the double patterning lithography (DPL). However, new DDL
requirements have been also emerged to improve the process margin and to reduce the mask-enhanced error factor
(MEEF), which is to maximize the resolution and image contrast. There are two approaches in DDL i.e. model basedand
rule based-DDLs. Rule-based DDL, in which the patterns are decomposed by the simple rules such as x- and ydirectional
rules, shows the low process margin in the 2-dimension (2D) patterns, i.e., line-end to line-end, line-end to
bar and semi-isolated bars.
In this paper, we first present various analyses of our new model-based DDL (MBDDL) method. Our goal is to
maximize the process margin of the 2D patterns. Our main contributions are as follows. (1) We generate new 2D test
patterns including various configurations of the metal layer. The new 2D patterns can be used to optimize the parameters
of the MBDDL and to build the good design rules. The purpose of building the good design rules is improving the
process margin of the certain 2D patterns with the low process margin in spite of optimizing the parameters of MBDDL.
(2) We optimize the initial layout decomposition, which is the first step of MBDDL and affects the whole of MBDDL
quality. In addition, the model-based decomposition is applied with the process-window OPC (PWOPC) in terms of the
criteria of edge placement error (EPE) and mask rule checking (MRC) violation. Our new model-based approach
including the newly designed test patterns and optimized decomposition parameters leads to the improved depth of focus
(DOF) and enhanced the exposure latitude (EL). We achieve the 80nm DOF, which is the manufacturable margin for the
metal 1 layer at the sub-30nm node.
The two key factors in EUV lithography imaging will be flare and shadow effect among other issues. The flare which is
similar to the long range density loading effect and also known to be of high level will generate CD variation throughout
the exposure field while the EUV specific shadow effect differentiates H-V CDs along the slit. The long range character
of flare in EUV full field scanner can even affect CDs in the neighboring fields. It seems to be apparent that the major
imaging challenges for EUV lithography to be successfully adopted and applied to device manufacturing will be
determined by how smartly and effectively CD variations induced both by flare and shadow effect in the full chip level
are compensated. We investigated and assessed the previously proposed full chip level compensation strategies of the
flare and shadow effect in EUVL for the application to memory device both by simulation and experiments on the
condition of full field scanner. The effectiveness of flare compensation for the case of thin absorber mask was also
addressed together with related impact on the shadow induced H-V CD bias.
Extreme ultraviolet lithography (EUVL) is one of the leading candidates for next-generation lithography technology for
the 32 nm half-pitch node and beyond. We have evaluated the Alpha Demo Tool(ADT) characterizing for mixed-andmatched
overlay(MMO), flare noise, and resolution limit. For process integration, one of the important things in EUVL
is overlay capability. We performed an overlay matching test of a 1.35NA and 193 immersion tool using a low thermal
expansion material(LTEM) mask. We also investigated the flare level of the EUV ADT for device applications. The
current EUV tool has a higher flare level than ArF lithography tools. We applied a contact layer for 40nm node device
integration to reduce the variation in critical dimension(CD) from the flare noise.
Flare in EUV mirror optics has been reported to be very high and long range effect due to its character which is inversely
proportional to the 4th order of wavelength. The high level of flare will generate CD (Critical Dimension) variation
problem in the area where the gradient of aerial pattern density is large while the long range influencing character would
confront an issue of computational challenge either for OPC (Optical Proximity Correction) modeling or for any other
practical ways to accommodate such a long range effect. There also exists another substantial challenge of measuring
and characterizing such a long range flare accurately enough so that the characterized flare can successfully be used for
the compensation in the standard OPC flow.