Joy Cheng

Polymer self assembly in semiconductor microelectronics

Integration of polymer self assembly with semiconductor processing enables sub-lithographic patterning of integrated circuit (IC) device elements and offers a non-traditional pathway to performance improvements (Black, 2005). We discuss target applications including surface-roughening for on-chip decoupling capacitors (Black et al., 2004), patterning nanocrystal floating gates for FLASH devices (Guarini et al., 2003), and defining FET channel arrays (Black, 2005)

Self-assembly patterning for sub-15nm half-pitch: a transition from lab to fab

Directed self-assembly is an emerging technology that to-date has been primarily driven by research efforts in university and corporate laboratory environments. Through these environments, we have seen many promising demonstrations of forming self-assembled structures with small half pitch (<15 nm), registration control, and various device-oriented shapes. Now, the attention turns to integrating these capabilities into a 300mm pilot fab, which can study directed selfassembly in the context of a semiconductor fabrication environment and equipment set. The primary aim of this study is to create a 300mm baseline process of record using a 12nm half-pitch PS-b-PMMA lamellae block copolymer in order to establish an initial measurement of the defect density due to inherent polymer phase separation defects such as dislocations and disclinations.

Si-containing block copolymers for self-assembled nanolithography

Block copolymers can self-assemble to generate patterns with nanoscale periodicity, which may be useful in lithographic applications. Block copolymers in which one block is organic and the other contains Si are appealing for self-assembled lithography because of the high etch contrast between the blocks, the high etch resistance of the Si-containing block, and the high Flory–Huggins interaction parameter, which is expected to minimize line edge roughness. The locations and long range order of the microdomains can be controlled using shallow topographical features. Pattern generation from poly(styrene)-poly(ferrocenyldimethylsilane) and poly(styrene)-poly(dimethylsiloxane) block copolymers, and the subsequent pattern transfer into metal, oxide, and polymer films, is described

Three‐Dimensional Nanofabrication by Block Copolymer Self‐Assembly

Thin films of block copolymers are widely seen as enablers for nanoscale fabrication of semiconductor devices, membranes, and other structures, taking advantage of microphase separation to produce well-organized nanostructures with periods of a few nm and above. However, the inherently three-dimensional structure of block copolymer microdomains could enable them to make 3D devices and structures directly, which could lead to efficient fabrication of complex heterogeneous structures. This article reviews recent progress in developing 3D nanofabrication processes based on block copolymers.

Rapid directed self assembly of lamellar microdomains from a block copolymer containing hybrid

The directed self-assembly of a lamellar-forming hybrid block copolymer system comprising of a poly(styrene-b-ethylene oxide) and organosilicates (OSs) has been investigated. The addition of OS to the block copolymer is found to provide additional control over the persistence length of lamellae as well as the behavior of directed self assembly. Two OSs with different molecular weights and reactivities have been compared in this experiment. Both OSs yield the same local structure of lamellar domains but different degrees of mid- and long-range order. Longer correlation length and better alignment of lamellar domains were observed with the lower molecular weight, more reactive OS, which suggest a potential guidance for controlling over microdomains in block copolymer-containing hybrid systems.

Directed Self-Assembly of Silicon-Containing Block Copolymer Thin Films

The directed self-assembly (DSA) of lamella-forming poly(styrene-block-trimethylsilylstyrene) (PS-PTMSS, L0=22 nm) was achieved using a combination of tailored top interfaces and lithographically defined patterned substrates. Chemo- and grapho-epitaxy, using hydrogen silsesquioxane (HSQ) based prepatterns, achieved density multiplications up to 6× and trench space subdivisions up to 7×, respectively. These results establish the compatibility of DSA techniques with a high etch contrast, Si-containing BCP that requires a top coat neutral layer to enable orientation.

Directed self-assembly defectivity assessment. Part II

The main concern for the commercialization of directed self-assembly (DSA) for semiconductor manufacturing continues to be the uncertainty in capability and control of defect density. Our research investigates the defect densities of various DSA process applications in the context of a 300mm wafer fab cleanroom environment; this paper expands substantially on the previously published DSA defectivity study by reporting a defect density process window relative to chemical epitaxial pre-pattern registration lines; as well as investigated DSA based contact hole shrinking and report critical dimension statistics for the phase separated polymers before and after etch, along with positional accuracy measurements and missing via defect density.

Determination of the Internal Morphology of Nanostructures Patterned by Directed Self Assembly

The directed self-assembly (DSA) of block copolymers (BCP) is an emerging resolution enhancement tool that can multiply or subdivide the pitch of a lithographically defined chemical or topological pattern and is a resolution enhancement candidate to augment conventional lithography for patterning sub-20 nm features. Continuing the development of this technology will require an improved understanding of the polymer physics involved as well as experimental confirmation of the simulations used to guide the design process. Both of these endeavors would be greatly facilitated by a metrology, which is capable of probing the internal morphology of a DSA film. We have developed a new measurement technique, resonant critical-dimension small-angle X-ray scattering (res-CDSAXS), to evaluate the 3D buried features inside the film. This is an X-ray scattering measurement where the sample angle is varied to probe the 3D structure of the film, while resonant soft X-rays are used to enhance the scattering contrast. By measuring the same sample with both res-CDSAXS and traditional CDSAXS (with hard X-rays), we are able to demonstrate the dramatic improvement in scattering obtained through the use of resonant soft X-rays. Analysis of the reciprocal space map constructed from the res-CDSAXS measurements allowed us to reconstruct the complex buried features in DSA BCP films. We studied a series of DSA BCP films with varying template widths, and the internal morphologies for these samples were compared to the results of single chain in mean-field simulations. The measurements revealed a range of morphologies that occur with changing template width, including results that suggest the presence of mixed morphologies composed of both whole and necking lamella. The development of res-CDSAXS will enable a better understanding of the fundamental physics behind the formation of buried features in DSA BCP films.

Self-assembling materials for lithographic patterning: overview, status, and moving forward

We survey several different approaches wherein self-assembly has been applied in lithographic patterning. As part of this survey, we trace the evolution of block copolymer directed self-assembly used as lithographic technique, and summarize its current status. We compare a process based on block copolymer lithography with an equivalent process based on spacer pitch division. We conclude with a brief discussion of design issues and future research in the field.

Pattern Placement Accuracy in Block Copolymer Directed Self-Assembly Based on Chemical Epitaxy

The realization of viable designs for circuit patterns using the dense features formed by block copolymer directed self-assembly (DSA) will require a precise and quantitative understanding of self-assembled feature registration to guiding templates or chemical prepatterns. Here we report measurements of DSA placement error for lamellar block copolymer domains indexed to specific lines in the surface chemical prepattern for spatial frequency tripling and quadrupling. These measurements are made possible by the use of an inorganic domain-selective prepattern material that may be imaged upon polymer removal after DSA and a prepattern design incorporating a single feature serving as an in situ registration mark that is identifiable by pattern symmetry in both the prepattern and resulting self-assembled pattern. The results indicate that DSA placement error is correlated with average prepattern line width as well as prepattern pitch uniformity. Finally, the magnitude of DSA placement error anticipated for a uniform, optimized prepattern is estimated.