Masafumi Hori

Dual brush process for selective surface modification in graphoepitaxy directed self-assembly

Grapho-epitaxy directed self-assembly is a potential low-cost solution for patterning via layers with pitches beyond the reach of a single optical lithographic exposure. In this process, selective control of the interfacial energy at the bottom and sidewall of the template is an important but challenging exercise. In this work, a dual brush process is implemented, in which two brushes with distinct end-groups are consecutively grafted to the pre-pattern to achieve fully independent modification of the bottom and sidewall surface of the template. A comprehensive study of hole pattern quality shows that using a dual brush process leads to a substantial improvement in terms of positional and dimensional variability across the process window. These findings will be useful to others who wish to manipulate polymer-surface interactions in directed self-assembly flows.

Photosensitized Chemically Amplified Resist (PSCAR) 2.0 for high-throughput and high-resolution EUV lithography: dual photosensitization of acid generation and quencher decomposition by flood exposure

A new type of Photosensitized Chemically Amplified Resist (PSCAR) **: “PSCAR 2.0,” is introduced in this paper. PSCAR 2.0 is composed of a protected polymer, a “photo acid generator which can be photosensitized” (PS-PAG), a “photo decomposable base (quencher) which can be photosensitized” (PS-PDB) and a photosensitizer precursor (PP). With this PSCAR 2.0, a photosensitizer (PS) is generated by an extreme ultra-violet (EUV) pattern exposure. Then, during a subsequent flood exposure, PS selectively photosensitizes the EUV exposed areas by the decomposition of a PS-PDB in addition to the decomposition of PS-PAG. As these pattern-exposed areas have the additional acid and reduced quencher concentration, the initial quencher loading in PSCAR 2.0 can be increased in order to get the same target critical dimensions (CD). The quencher loading is to be optimized simultaneously with a UV flood exposure dose to achieve the best lithographic performance and resolution. In this work, the PSCAR performance when different quenchers are used is examined by simulation and exposure experiments with the 16 nm half-pitch (HP) line/space (L/S, 1:1) patterns. According to our simulation results among resists with the different quencher types, the best performance was achieved by PSCAR 2.0 using PS-PDB with the highest possible chemical gradient resulting in the lowest line width roughness (LWR). PSCAR 2.0 performance has furthermore been confirmed on ASML’s NXE:3300 with TEL’s standalone pre-alpha flood exposure tool at imec. The initial PSCAR 2.0 patterning results on NXE:3300 showed the accelerated photosensitization performance with PS-PDB. From these results, we concluded that the dual sensitization of PS-PAG and PS-PDB in PSCAR 2.0 have a potential to realize a significantly improved resist performance in EUV lithography.

Via patterning in the 7-nm node using immersion lithography and graphoepitaxy directed self-assembly

Abstract. Insertion of a graphoepitaxy directed self-assembly process as a via patterning technology into integrated circuit fabrication is seriously considered for the 7-nm node and beyond. At these dimensions, a graphoepitaxy process using a cylindrical block copolymer that enables hole multiplication can alleviate costs by extending 193-nm immersion-based lithography and significantly reducing the number of masks that would be required per layer. To be considered for implementation, it needs to be proved that this approach can achieve the required pattern quality in terms of defects and variability using a representative, aperiodic design. The patterning of a via layer from an actual 7-nm node logic layout is demonstrated using immersion lithography and graphoepitaxy directed self-assembly in a fab-like environment. The performance of the process is characterized in detail on a full 300-mm wafer scale. The local variability in an edge placement error of the obtained patterns (4.0 nm 3σ for singlets) is in line with the recent results in the field and significantly less than of the prepattern (4.9 nm 3σ for singlets). In addition, it is expected that pattern quality can be further improved through an improved mask design and optical proximity correction. No major complications for insertion of the graphoepitaxy directed self-assembly into device manufacturing were observed.

Constructing a robust PSCARTM process for EUV (Conference Presentation)

In order to lower the cost of ownership of EUV lithography, high sensitivity EUV resists , enabling higher throughput of EUV scanners are being explored. The concept that utilizes a Photosensitized Chemically Amplified ResistTM (PSCARTM) is a promising solution for achieving increased resist sensitivity, while maintaining other high performance characteristics of the material (i.e., resolution, line edge roughness (LER), exposure latitude). PSCAR uses a UV exposure after EUV exposure and selective absorption to meet these goals . Preliminary results have been discussed in previous papers 1-8. PSCAR utilizes an area-selective photosensitization mechanism to generate more acid in the exposed areas during a UV exposure. PSCAR is an attempt to break the resolution, line-edge-roughness, and sensitivity trade-off (RLS trade-off) relationships that limit standard chemically amplified resists. The photosensitizer, which is generated in exposed area by a photoacid catalytic reaction, absorbs the UV exposure light selectively and generates additional acid in the exposed area only. Material development and UV exposure uniformity are the key elements of PSCAR technology for semiconductor mass fabrication. This paper will review the approaches toward improvement of PSCAR resist process robustness. The chemistry’s EUV exposure cycle of learning results from experiments at imec will be discussed.

EUV resist sensitization and roughness improvement by PSCAR with in-line flood exposure system (Conference Presentation)

Photosensitized Chemically Amplified ResistTM (PSCARTM) **2.0’s advantages and expectations are reviewed in this paper. Alpha PSCAR in-line UV exposure system (“Litho Enhancer”) was newly installed at imec in a Tokyo Electron Ltd. (TELTM)’s CLEAN TRACKTM LITHIUS ProTM Z connected to an ASML’s NXE:3300. Using the Litho Enhancer, PSCAR 2.0 sensitization preliminary results show that suppression of roughness enhancement may occur while sensitivity is increased. The calibrated PSCAR 2.0 simulator is used for prediction of resist formulation and process optimization. The simulation predicts that resist contrast enhancement could be realized by resist formulation and process optimization with UV flood exposure.

Novel EUV photoresist for sub-7nm node (Conference Presentation)

Extreme ultraviolet (EUV) lithography has been recognized as a promising candidate for the manufacturing of semiconductor devices as LS and CH pattern for 7nm node and beyond. EUV lithography is ready for high volume manufacturing stage. For the high volume manufacturing of semiconductor devices, significant improvement of sensitivity and line edge roughness (LWR) and Local CD Uniformity (LCDU) is required for EUV resist. It is well-known that the key challenge for EUV resist is the simultaneous requirement of ultrahigh resolution (R), low line edge roughness (L) and high sensitivity (S). Especially high sensitivity and good roughness is important for EUV lithography high volume manufacturing. We are trying to improve sensitivity and LWR/LCDU from many directions. From material side, we found that both sensitivity and LWR/LCDU are simultaneously improved by controlling acid diffusion length and efficiency of acid generation using novel resin and PAG. And optimizing EUV integration is one of the good solution to improve sensitivity and LWR/LCDU. We are challenging to develop new multi-layer materials to improve sensitivity and LWR/LCDU. Our new multi-layer materials are designed for best performance in EUV lithography system. From process side, we found that sensitivity was substantially improved maintaining LWR applying novel type of chemical amplified resist (CAR) and process. EUV lithography evaluation results obtained for new CAR EUV interference lithography. And also metal containing resist is one possibility to break through sensitivity and LWR trade off. In this paper, we will report the recent progress of sensitivity and LWR/LCDU improvement of JSR novel EUV resist and process.