Directed self-assembly (DSA) of block copolymers is proving to be an interesting and innovative method to make three-dimensional periodic, uniform patterns useful in a variety of microelectronics applications. Attributes critical to acceptable DSA performance of block copolymers include molecular weight uniformity, final purity, and reproducibility in all the steps involved in producing the polymers. Reversible Addition Fragmentation Chain Transfer (RAFT) polymerization technology enables the production of such materials provided that careful process monitoring and compositional homogeneity measurement systems are employed. It is uniquely suited to construction of multiblocks with components of widely divergent surface energies and functionality. We describe a high chi diblock system comprising partially fluorinated methacrylates and substituted styrenics. While special new polymer separation strategies involving controlled polymer particle assembly in liquid media are required for some monomer systems and molecular weight regimes, we have been able to demonstrate high yield and compositionally homogeneous diblocks of lamellar and cylindrical morphology with polydispersities < 1.1. During purification processes, these diblock materials undergo assembly processes in liquid media, and with appropriate controls, this allows for removal of soluble homopolymer contaminants. SAXS analyses of solid polymer samples provide estimates of lamellar d-spacing, and a good correlation with molecular weight is shown. This system will be described.
Reversible Addition Fragmentation Chain Transfer (RAFT) polymerization technology enables the production of
polymers possessing low polydispersity (PD) in high yield for many applications. RAFT technology also enables control
over polymer architecture. With synthetic control over these polymer characteristics, a variety of polymers can be
designed and manufactured for use in advanced electronic applications. By matching the specific RAFT reagent and
monomer combinations, we can accommodate monomer reactivity and optimize acrylate or methacrylate
polymerizations (193 and 193i photoresist polymers) or optimize styrenic monomer systems (248 nm photoresist
polymers) to yield polymers with PD as low as 1.05. For 193i lithography, we have used RAFT technology to produce
block copolymers comprising of a random "resist" block with composition and size based on conventional dry
photoresist materials and a "low surface energy" block The relative block lengths and compositions may be varied to
tune solution migration behavior, surface energy, contact angles, and solubility in developer. Directed self assembly is
proving to be an interesting and innovative method to make 2- and even 3-dimensional periodic, uniform patterns. Two
keys to acceptable performance of directed self assembly from block copolymers are the uniformity and the purity of the
materials will be discussed.
Reversible Addition Fragmentation Chain Transfer (RAFT) technology has been developed for use in producing high
yield low polydispersity (PD) polymers for many applications. RAFT technology is being used to produce low PD
polymers and to allow control of the polymer architecture. A variety of polymers are being synthesized for use in
advanced photoresists using this technique. By varying the RAFT reagent used we can modulate the system reactivity of
the RAFT reagent and optimize it for use in acrylate or methacrylate monomer systems (193 and 193i photoresist
polymers) or for use in styrenic monomer systems (248 nm photoresist polymers) to achieve PD as low as 1.05.
RAFT polymerization technology also allows us to produce block copolymers using a wide variety of monomers. These
block copolymers have been shown to be useful in self assembly polymer applications to produce unique and very small
The mutual compatibilities of all the components within a single layer 193 photoresist are very important in order to
achieve low LWR and low defect count. The advent of immersion imaging demands an additional element of protection
at the solid/liquid interface. We have used RAFT technology to produce block copolymers comprising a random "resist"
block with composition and size based on conventional dry photoresist materials, and a "low surface energy" block for
use in 193i lithography. The relative block lengths and compositions may be varied to tune solution behavior, surface
energy, contact angles, and solubility in developer. The use of this technique will be explored to produce polymers used
in hydrophobic single layer resists as well as additives compatible with the main photoresist polymer.
Remarkable progress has been made in the formulation of chemically amplified resists for deep-UV (DUV or 248 nm) lithography. These materials are now in general use in full scale manufacturing. One of the deterrents to rapid and universal adoption of DUV lithography has been the combination of high cost of ownership and a narrow process latitude when compared to conventional i-line process alternatives. A significant part of the high cost of the DUV process is associated with installing and maintaining special air handling equipment that is required to remove basic contaminants from the ambient. Manufacture process latitude demands this special air handling. The chemically amplified resists were developed originally to support mercury lamp powered exposure systems. The sensitivity realized by chemical amplification is required to enable useful productivity with such systems that generate very little DUV flux at the wafer plane. With the advent of high powered excimer laser based illumination systems for 248 nm steppers and step-and-scan systems, it is appropriate to re-examine the applicability of non-chemically amplified DUV resist systems. These systems are less sensitive but have the potential to offer both lower cost of ownership and improved process latitude. A series of photoactive compounds (PACs) have been synthesized and auditioned for use in the formulation of a non-chemically amplified 248 nm resist. The most promising of these materials are analogs of 3-oxo-3-diazocoumarin. This chromophore displays photochemistry that is analogous to that of the diazonaphthoquinones (DNQ) that are the basis of i-line resist formulations, but it bleaches at 248 nm. Several structural analogs of the chromophore have been synthesized and a variety of ballast groups have been studied with the goal of enhancing the dissolution inhibition properties of the molecule. The diazocoumarin PACs have been formulated with customized phenolic resins that were designed to provide the combination of optical transparency, dry etch resistance and the dissolution characteristics that are required for manufacturing applications. The resins are copolymers of poly(4-hydroxystyrene) and blends of these polymers with novolac.