Our target at EIDEC is to study the feasibility of directed self-assembly (DSA) technology for semiconductor device manufacturing through electrical yield verification by development of such as process, material, metrology, simulation and design for DSA. We previously developed a grapho/chemo-hybrid coordinated line epitaxial process for sub-15-nm line-and-space (L/S) patterning using polystyrene-block-poly(methyl methacrylate) lamellar block copolymers (BCPs)1– 3. Electrical yield verification results showed that a 30% open yield was successfully achieved with a metal wire line length of 700 μm 4. In the next stage of the evaluation, a sub-10-nm L/S DSA patterning process based on graphoepitaxial DSA of 20-nm lamellar period organic BCPs was developed based on neutral layer and guide space width optimization. At a 30-nm guide height, problems such as BCP overflow and DSA line shorts were observed after the dry development. At a 60-nm guide height, grid-like short defects were observed under dry development shallow etch conditions and sub-10-nm L/S patterns were formed under optimized etch conditions with a suitable BCP film thickness margin. The process performance was evaluated in terms of defects and critical dimension measurements using an electron beam inspection system and critical dimension-scanning electron microscope metrology. The main DSA defects were short defects, and the spatial roughness appeared to be caused by the periodic pitches of these short defects and the guide roughness. We successfully demonstrated the fabrication of sub-10-nm metal wires consists of L/S, pad, connect and cut patterns with controlled alignment and stack structure through lithography, etching and CMP process on a 300- mm wafer using the fully integrated DSA process and damascene processing.
Si-rich poly((polyhedral oligomeric silsesquioxane) methacrylate)-b-poly(trifluoroethyl methacrylate) (PMAPOSS-b- PTFEMA) was used to form 8-nm half-pitch line and space (L/S) pattern via grapho-epitaxy. Vertical alignment of the lamellae was achieved without using either a neutral layer or top-coating material. Because PMAPOSS-b-PTFEMA forms vertical lamellae on a variety of substrates, we used two types of physical guide structures for grapho-epitaxy; one was a substrate guide and the other was a guide with an embedded under layer. On the substrate guide structure, a fine L/S pattern was obtained with trench widths equal to 3–7 periods of the lamella spacing of the block copolymer, Lo. However, on the embedded under layer guide structure, L/S pattern was observed only with 3 Lo and 4 Lo in trench width. Cross-sectional transmission electron microscope images revealed that a thick PMAPOSS layer was formed under the PMAPOSS-b-PTFEMA L/S pattern. Pattern transfer of the PMAPOSS-b-PTFEMA L/S pattern was prevented by a thick PMAPOSS layer. To achieve pattern transfer to the under layer, optimization of the surface properties is necessary.
Directed self-assembly is a candidate process for sub-15-nm patterning applications. It will be necessary to develop the DSA process fully and consider process integration to adapt the DSA process for use in semiconductor manufacturing. We investigated the reactive ion etching (RIE) process for the fabrication of sub-10-nm metal wires using the DSA process and the process integration requirements for electrical yield verification. We evaluated the process using an organic high-chi block copolymer (BCP) with a lamellar structure. One critical issue during DSA pattern transfer involves the BCP bottom connection. The BCP bottom connections could be removed without BCP mask loss by using the optimum bias power and the optimum BCP film thickness. The sub-10-nm DSA line-and-space (L/S) patterns were successfully transferred to a SiO2 layer with sufficient film thickness for the fabrication of the metal wire. We also evaluated the overlay technique used in the process. The connect patterns and cut patterns were overlaid on 10-nm trenches fabricated by the DSA process.
The suppression of outgassing from the EUV resist is one of the significant challenges, which has to be addressed for realizing EUV lithography (EUVL). The outgassing might be the main contributor involved in the contamination of the mirror optics in scanners. This may result in reflectivity losses. The pragmatic outgassing test that utilizes the witness sample (WS) was used as a general method to quantify the outgassing level for commercially available chemically amplified resists (CAR). There are two types of contaminations. The first type of contamination involves a cleanable contamination that mainly comprises hydrocarbons that can be removed by the hydrogen radical cleaning. Another type of contamination includes the noncleanable contamination that remains on the WS even after hydrogen radical cleaning. Several outgas qualification results were evaluated at the EIDEC [1, 2]. The data indicated that contaminations by the CAR mainly comprised the cleanable contaminations. The data also indicated that there were almost negligible noncleanable contaminations from the CAR. EUV resist communities accelerate the development of high sensitivity resists to compensate the low power of the EUV source. Nonchemically amplified resist (nonCAR) with a new platform is a candidate for high sensitivity resists. The nonCAR includes some types of metal elements with high absorbance for EUV light. There is very limited research on the outgassing characteristics of the nonCAR. In this study, we considered an EUV exposure process in the actual EUV scanner and EUV resists were exposed in a hydrogen environment. A potential risk could result from the reaction of the hydrogen radicals generated by the EUV light with the metal elements in the nonCAR and the metal hydride outgases from the resist. This would result in a noncleanable contamination on the EUV mirror [3]. The knowledge with respect to outgassing from an organic metal complex is insufficient even in a vacuum condition. Hence, the study involved the preparation of certain types of organic metal complexes as model materials. Then, the outgassing evaluations for the materials were carried out as a fundamental studies in a vacuum condition. The results were reported in this study.
This study describes the use of a novel ultra-high sensitive ‘metal resist’ for use in extreme ultraviolet (EUV) lithography. Herein, the development of a metal resist has been studied for improving the sensitivity when using metal-containing non-chemically amplified resist materials; such materials are metal-containing organic–inorganic hybrid compounds and are referred to as EUVL Infrastructure Development Center, Inc. (EIDEC) standard metal EUV resist (ESMR). The novel metal resist’s ultra-high sensitivity has previously been investigated for use with electron beam (EB) lithography. The first demonstration of ESMR performance was presented in SPIE2015, where it was shown to achieve 17-nm lines with 1.5 mJ/cm2: equivalent in EUV lithography tool. The sensitivity of ESMR using EUV open-flame exposure was also observed to have the same high sensitivity as that when using EB lithography tool. Therefore, ESMR has been confirmed to have the potential of being used as an ultra-high sensitive EUV resist material. The metal-containing organic–inorganic hybrid compounds and the resist formulations were investigated by measuring their sensitivity and line-width roughness (LWR) improvement. Furthermore, new processing conditions, such as new development and rinse procedures, are an extremely effective way of improving lithographic performance. In addition, the optimal dry-etching selective conditions between the metal resist and spin-on carbon (SOC) were obtained. The etched SOC pattern was successfully constructed from a stacked film of metal resist and SOC.
The perpendicularly orientated lamellar structure of the self-organized diblock copolymer is an attractive template for sub-10-nm line-and-space pattern formation. We propose a method of evaluating the neutral layer (NL) whose performance has an important bearing on the perpendicular orientation of the lamellar structure. The random copolymer of methyl methacrylate and i-butyl POSS methacrylate (MAIBPOSS) has been investigated as an NL for a polymethylmethacrylate-b-polymethacrylethylPOSS (PMMA-b-PMAIBPOSS) lamellar structure. PMMA-b-PMAIBPOSS material has the potential to form sub-10 nm line-and-space pattern, in addition to high etch selectivity due to its POSS structure. Under the free surface, PMMA-b-PMAIBPOSS film on the random copolymer layer showed horizontal orientation. However, a half-pitch of a 7-nm finger pattern structure was observed by peeling off the horizontally oriented layer. The upper portion of the PMMA-b-PMAIBPOSS film was eliminated till proximity of the random copolymer layer by CF4 gas etching. From the result, it was revealed that the PMMA-r-PMAIBPOSS works as an NL. It was confirmed that the contact angle analysis using an appropriate polymer is a suitable method for evaluation of the surface energy performance of the copolymer with the attribute of high segregation energy.
The relation between resist composition and its development behavior was evaluated. The effect of a hydrophobic unit on a resist and on its development behavior was systematically investigated. The resist was exposed to extreme ultraviolet (EUV) or electron beam (EB) exposure, and the development behavior of the film was observed by high-speed atomic force microscopy (HS-AFM). The introduction of a hydrophobic group in the resist resulted in diminished swelling behavior and uniform dissolution. The resist resin cluster shape was also altered by the introduction of the hydrophobic group. These behaviors imply that the resin–resin and resin–tetramethylammonium hydroxide solution interactions differ. EUV lithography suffers from the photon issue that causes stochastic uniformity; however, in this study, we demonstrate the feasibility of achieving a better uniformity of resist patterning by altering the resist formulation.
In this study, half-pitch (HP) 15 nm line-and-space (L/S) metal wires were successfully fabricated and fully integrated on a 300 mm wafer by applying directed self-assembly (DSA) lithography and pattern transfer for semiconductor device manufacturing. In order to evaluate process performances of DSA, we developed a simple sub-15 nm L/S patterning process using polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) lamellar block copolymer (BCP), which utilizes trimming resist and shallow etching spin-on-glass (SOG) as pinning guide[1]-[4]. From the results of defect inspection after SOG etch using Electron Beam (EB) inspection system, defects were classified as typical DSA defects or defects relating to DSA pattern transfer. From the evaluation of DSA L/S pattern Critical Dimension (CD), roughness and local placement error using CD-SEM, it is considered that isolated PS lines are placed at the centerline between guides and that placement of paired PS lines depends on the guide width. The control of the guide resist CD is the key to local placement error and the paired lines adjacent to the guide shifted toward the outside (0.5 nm) along the centerline of the isolated line after SOG etch. We demonstrated fabrication of HP 15 nm metal wires in trenches formed by the DSA process with reactive ion etching (RIE), followed by metal chemical vapor deposition (CVD) and chemical mechanical polishing (CMP). By SEM observation of alignment errors between the trenches and connect spaces, overlay shift patterns (-4 nm) in guide lithography mask were fabricated without intra-wafer alignment errors.
Directed self-assembly (DSA) is one of the promising candidates for next-generation lithography. We developed a novel simple sub-15 nm line-and-space (L/S) patterning process, the “coordinated line epitaxy (COOL) process,” using grapho- and chemo-hybrid epitaxy. In this study we evaluate the DSA L/S pattern transfer margin. Since defect reduction is difficult in the case of the DSA pattern transfer process, there is a need to increase the pattern transfer margin. We also describe process integration for electrical yield verification.
This paper reports on an all-out effort to reduce the intersite gap of the resist outgassing contamination growth in the results obtained under the round-robin scheme. All test sites collaborated to determine the causes of such gaps. First, it was determined that wafer temperature during exposure could impact the amount of contamination growth. We discovered a huge intersite gap of wafer temperatures among the sites by using a wafer-shaped remote thermometer with wireless transmitting capability. Second, whether the contamination-limited regime was attained during testing could have been another primary root cause for such a difference. We found that for one of the model resists whose protecting unit had lower activation energy and molecular weight the contamination-limited regime was insufficient at one test site. Third, the ratio of the exposed area to pumping speed is necessary to equalize contamination growth. We validated the effect of matching the ratio of exposure area to pumping speed on reducing the intersite gap. This study and the protocols put in place should reduce the intersite gap dramatically.
The suppression of extreme ultraviolet (EUV) photoresist-related outgassing is one of the challenges in high-volume manufacturing with EUV lithography (EUVL), because it contributes to the contamination of the EUV scanner mirror optics, resulting in reflectivity loss. Witness sample pragmatic outgas qualification has been developed into the general method for clarifying commercially available, chemically amplified resists. Preliminary results have suggested a linear correlation between contamination thickness in the electron-beam-based and the EUV-based evaluation systems. In fact, a positive relationship was observed between contamination thickness and exposure dose. However, recent experiments indicate that in some resists, this relationship is not linear. In the present study, a resist outgas model is proposed and tested to investigate the contamination thickness’ dependency on exposure dose. The model successfully explains the experimental outgas phenomenon. It is estimated that increasing exposure dose, in resists with low activation energies (Ea) in deprotection reactions, results in extreme increase in contamination thickness. Furthermore, the low-Ea resists have high contamination risk when exposure is extensive.
We proposed a new concept of “defect-aware process margin.” Defect-aware process margin was evaluated by investigating the energy difference between the free-energy of the most stable state and that of the first metastable state. The energy difference is strongly related to the defect density in DSA process. As a result of our rigorous simulations, the process margin of the pinning layer width was found to be: (1) worse when the pinning layer affinity is too large, (2) better when the background affinity has the opposite sign of the pinning layer affinity, and (3) better when the top of the background layer is higher than that of the pinning layer by 0.1L0.
The advantage of blend DSA (Directed Self Assembly) is milder anneal condition than PS-b-PMMA BCP
DSA materials and availability of conventional instruments. In this paper, blend type DSA was applied for
hole patterning. Target patterns were contact hole and oval hole. Polymer phase separation behavior has
been studied from the point of χN. In the case of polymer blend, χN needs to be more than 2 to give phase
separation. At first the effect of polymer size was studied. When the polymer weight was low, the shrunk
hole was not clean because of low χN. Furthermore, the correlation of shrink amount and χN was studied.
Higher χN polymer blend system gave higher shrink amount. High χN polymer systems give clear interface,
then the intermixing area would be reduced, then the attached polymer blend part became larger. The
polymer blend ratio effect was also investigated. The blend ratio was varied for polymer A/ polymer
B=70/30-50/50. The shrink amount of oval hole was reduced with increasing the ratio of polymer B.
However, the shrink amount ratio of CDY/CDX was almost constant (~3).
Beyond 45nm node processes, ArF hyper-NA immersion lithography systems are an inevitable choice for
obtaining smaller patterns. A hyper-NA, dual BARC system is proposed to achieve low reflectivity. However, the
ability for the resist to ask as a mask is severely challenged because of the increased film thickness associated with a dual
BARC system. In order to obtain enough etch selectivity to the substrate, multi-layer resist processes can be applied.
General multi-layer resist processes uses silicon containing an inorganic spin-on hard mask and an organic spin-on hard
mask with a high carbon content. One of the problems of organic spin-on hard masks is high out-gassing, which can
cause defect issues in mass production. We have developed a new organic hard mask with low out-gassing, good
reflectivity control (< 0.2%) and good etch durability. Gap-filling performance also can be controlled by changing its
fluidity and wettability on the substrate.
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