Sub-15nm Silicon Lines Fabrication via PS-b-PDMS Block Copolymer Lithography

This paper describes the fabrication of nanodimensioned silicon structures on silicon wafers from thin films of a poly(styrene)-block-poly(dimethylsiloxane) (PS-b-PDMS) block copolymer (BCP) precursor self-assembling into cylindrical morphology in the bulk. The structure alignment of the PS-b-PDMS (33 k–17 k) was conditioned by applying solvent and solvothermal annealing techniques. BCP nanopatterns formed after the annealing process have been confirmed by scanning electron microscope (SEM) after removal of upper PDMS wetting layer by plasma etching. Silicon nanostructures were obtained by subsequent plasma etching to the underlying substrate by an anisotropic dry etching process. SEM images reveal the formation of silicon nanostructures, notably of sub-15 nm dimensions

Rapid, Brushless Self-assembly of a PS-b-PDMS Block Copolymer for Nanolithography

AbstractBlock copolymers (BCP) are highly promising self-assembling precursors for scalable nanolithography. Very regular BCP nanopatterns can be used as on-chip etch masks. The first step in the processing of BCP thin films is usually the chemical modification of the substrate surface, typically by grafting of a brush layer that renders the surface energy neutral relative to the constituent blocks. We provide here a first study on rapid, low temperature self-assembly of PS-b-PDMS (polystyrene-block-polydimethylsiloxane) on silicon substrates without a brush layer. We show that it forms line and antidot patterns after short solvo-thermal annealing. Unlike previous reports on this system, low temperature and short annealing time provide self-assembly in homogeneous thin films covering large substrate areas. This on-chip mask was then used for pattern transfer to the underlying silicon substrate. SEM (scanning electron microscope) images reveal silicon nanowires relative to the PDMS patterns of the BCP mask

A highly efficient sensor platform using simply manufactured nanodot patterned substrates

Block copolymer (BCP) self-assembly is a low-cost means to nanopattern surfaces. Here, we use these nanopatterns to directly print arrays of nanodots onto a conducting substrate (Indium Tin Oxide (ITO) coated glass) for application as an electrochemical sensor for ethanol (EtOH) and hydrogen peroxide (H\u1d7e4O\u1d7e4) detection. The work demonstrates that BCP systems can be used as a highly efficient, flexible methodology for creating functional surfaces of materials. Highly dense iron oxide nanodots arrays that mimicked the original BCP pattern were prepared by an ‘insitu’ BCP inclusion methodology using poly(styrene)-\u1d623\u1d62d\u1d630\u1d624\u1d62c-poly(ethylene oxide) (PS-\u1d623-PEO). The electrochemical behaviour of these densely packed arrays of iron oxide nanodots fabricated by two different molecular weight PS-\u1d623-PEO systems was studied. The dual detection of EtOH and (H\u1d7e4O\u1d7e4) was clearly observed. The as-prepared nanodots have good long term thermal and chemical stability at the substrate and demonstrate promising electrocatalytic performance

Study of the kinetics and mechanism of rapid self-assembly in block copolymer thin films during solvo-microwave annealing

Microwave annealing is an emerging technique for achieving ordered patterns of block copolymer films on substrates. Little is understood about the mechanisms of microphase separation during the microwave annealing process and how it promotes the microphase separation of the blocks. Here, we use controlled power microwave irradiation in the presence of tetrahydrofuran (THF) solvent, to achieve lateral microphase separation in high- lamellar-forming poly(styrene-b-lactic acid) PS-b-PLA. A highly ordered line pattern was formed within seconds on silicon, germanium and silicon on insulator (SOI) substrates. In-situ temperature measurement of the silicon substrate coupled to condition changes during "solvo-microwave" annealing allowed understanding of the processes to be attained. Our results suggest that the substrate has little effect on the ordering process and is essentially microwave transparent but rather, it is direct heating of the polar THF molecules that causes microphase separation. It is postulated that the rapid interaction of THF with microwaves and the resultant temperature increase to 55 degrees C within seconds causes an increase of the vapor pressure of the solvent from 19.8 to 70 kPa. This enriched vapor environment increases the plasticity of both PS and PLA chains and leads to the fast self-assembly kinetics. Comparing the patterns formed on silicon, germanium and silicon on insulator (SOI) and also an in situ temperature measurement of silicon in the oven confirms the significance of the solvent over the role of substrate heating during "solvo-microwave" annealing. Besides the short annealing time which has technological importance, the coherence length is on a micron scale and dewetting is not observed after annealing. The etched pattern (PLA was removed by an Ar/O-2 reactive ion etch) was transferred to the underlying silicon substrate fabricating sub-20 nm silicon nanowires over large areas demonstrating that the morphology is consistent both across and through the film

High quality sub-10 nm graphene nanoribbons by on-chip PS-b-PDMS block copolymer lithography

“High quality sub-10 nm graphene nanoribbons by on-chip PS-b-PDMS block copolymer lithography”, SEM image of sub-10 nm graphene nanoribbons fabricated using a brushless lamellar PS-b-PDMS (5k–5.5k) block copolymer and its Raman spectra.</p

Block copolymer self-assembly based device structures

This thesis investigated the block copolymer (BCP) thin film characteristics and pattern formation using a set of predetermined molecular weights of PS-b-PMMA and PS-b-PDMS. Post BCP pattern fabrication on the required base substrate a dry plasma etch process was utilised for successful pattern transfer of the BCP resist onto underlying substrate. The resultant sub-10 nm device features were used in front end of line (FEoL) fabrication of active device components in integrated circuits (IC). The potential use of BCP templates were further extended to metal and metal-oxide nanowire fabrication. These nanowires were further investigated in real-time applications as novel sensors and supercapacitors

Directed self-assembly of a high-chi block copolymer for the fabrication of optical nanoresonators

In this paper, we report on the fabrication of optical nanoresonators using block copolymer lithography. The nanostructured gratings or nanofins were fabricated by silicon-containing block copolymer on a chromium coated silicon-on-insulator substrate. Etch resistance of the block copolymer template enables a unique patterning technique for high-aspect-ratio silicon nanofins. Integration of the directed self-assembly with nanoimprint lithography provides a well-aligned array of nanofins with a depth of ~125 nm on a wafer scale. The developed nanopatterning method is an alternative to the previously reported nanopatterning techniques utilizing block copolymers. The dense array of sub-10 nm nanofins are used to realize a photonic guided-mode resonance filter. The nanostructured grating provides high sensitivity in refractive index sensing, as demonstrated by simulations and experiments in measuring varying contents of the tetrahydrofuran solvent.acceptedVersionPeer reviewe

Block co-polymers for nanolithography: rapid microwave annealing for pattern formation on substrates

The integration of block copolymer (BCP) self-assembled nanopattern formation as an alternative lithographic tool for nanoelectronic device fabrication faces a number of challenges such as defect densities, feature size, pattern transfer, etc. Key barriers are the nanopattern process times and pattern formation on current substrate stack layers such as hard masks (e.g., silicon nitride, Si3N4). We report a rapid microwave assisted solvothermal (in toluene environments) self-assembly and directed self-assembly of a polystyrene-block-polydimethylsiloxane (PS-b-PDMS) BCP thin films on planar and topographically patterned Si3N4 substrates. Hexagonally arranged, cylindrical structures were obtained and good pattern ordering was achieved. Factors affecting BCP self-assembly, notably anneal time and temperature, were studied and seen to have significant effects. Graphoepitaxy within the topographical structures provided long range, translational alignment of the patterns. The effect of surface topography feature size and spacing was investigated. The solvothermal microwave based technique used to provide periodic order in the BCP patterns showed significant promise and ordering was achieved in much shorter periods than more conventional thermal and solvent annealing methods. The implications of the work in terms of manufacturing technologies are discussed