For the 14nm node and beyond there are many integration strategy decisions that need to be made. All of these can have a significant impact on both alignment and overlay capability and need to be carefully considered from this perspective. One example of this is whether a Litho Etch Litho Etch (LELE) or a Self Aligned Double Patterning (SADP) process is chosen. The latter significantly impacting alignment and overlay mark design. In this work we look at overlay performance for a Back End of Line (BEOL) SADP Dual Damascene (DD) process for the 14nm node. We discuss alignment mark design, particularly focusing on the added complexity and issues involved in using such a process, for example design of the marks in the Metal Core and Keep layers and recommend an alignment scheme for such an integration strategy.
We successfully demonstrate a new approach to achieve 15nm half pitch with a spacer based selfaligned
triple patterning (SATP). This new concept has a single spacer deposition and etch step to
achieve 15nm half pitch using immersion lithography. Current spacer based triple or quadruple
patterning approaches use two iterations of "spacer deposition / spacer etch" for pitch splitting, thus
generating multi-modal trench CD, line CD and, trench depth population leading to challenging
process control. The new concept overcomes CD population issues and reduces additional steps over
implemented double patterning, thus could relax process window. The key innovative aspect is an
undercut dry trim achieved by a selective dry etch process, followed by a flowable CVD (EternaTM
FCVDTM) based gap-fill that can fill the undercut structures.
State of the art production single print lithography for contact is limited to ~43-44nm half-pitch given the
parameters in the classic photolithography resolution formula for contacts in 193 immersion tool (k1 ≥ 0.3,
NA = 1.35, and λ = 193nm). Single print lithography limitations can be overcome by (1) Process /
Integration based techniques such as double-printing (DP), and spacer based self-aligned double patterning
(SADP), (2) Non-standard printing techniques such as electron-beam (eBeam), extreme ultraviolet
lithography (EUVL), nano-imprint Lithography (NIL). EUV tools are under development, while nanoimprint
is a developmental tool only. Spacer based SADP for equal line/space is well documented as
successful patterning technique for 3xnm and beyond. In this paper, we present an adaptation of selfaligned
double patterning process to 2-D regular 32/32nm contact/space array. Using SADP process, we
successfully achieved an equal contact/space of 32/32nm using 193 immersion lithography that is only
capable of 43-44nm resolvable half-pitch contact printing. The key and unique innovation of this work is
the use of a 2-D (x and y axis) pillar structure to achieve equal contact/space. Final result is a dense contact
array of 32nm half-pitch in 2-D structure (x and y axis). This is achieved on simplified stack of Substrate /
APF / Nitride.
Further transfer of this new contact pattern from nitride to the substrate (e.g., Oxide, APF, Poly, Si...) is
possible. The technique is potentially extendible to 22/22nm contact/space and beyond.