Single-exposure extreme ultraviolet (EUV) lithography is quickly advancing as a replacement for argon fluoride immersion (ArFi)-based multiple patterning approaches for printing the most critical features in semiconductor devices. However, the dimensional scaling of EUV lithography patterns is hampered by stochastic effects, resulting in rough patterns and increased defectivity. A promising solution to mitigate these stochastic pattern variations is complementing top-down EUV lithography with bottom-up directed self-assembly (DSA) of block copolymers (BCPs). We investigated an EUV + DSA complementary process for the rectification of pitch 28-nm line/space (L/S) patterns on high-volume manufacturing compatible processing tools. We found that several DSA material and process parameters contribute to minimize the roughness of the rectified patterns. In particular, the BCP size and film thickness are the most critical parameters. In terms of defectivity, a combination of optical inspection and e-beam review pointed out that dislocations are not a major concern for EUV + DSA patterning due to the fast assembly kinetics. Instead, bridge and cluster defects are the main defect modes and minimum defectivity can be achieved by controlling the geometry of the guide pattern. Finally, the impact of pattern density multiplication by DSA was assessed by comparing the performance of the current EUV + DSA rectification process to the ArFi + DSA technology, both for generating a pitch 28 nm L/S pattern. (c) 2024 Society of Photo-Optical Instrumentation Engineers (SPIE)

As the industry enters Extreme Ultraviolet (EUV) era, like every technology generation in history, there are constant demands for new materials to solve the emerging challenges accompanying with the continuous scaling effort. Although Chemically Amplified Resist (CAR) resist and conventional tri-layer stack that were established for DUV lithography have been successfully extended to EUV, challenges such as limited etch budget associated with further resist thickness shrinking needed for high Numerical Aperture (NA) EUV, increased line wiggling in SOC layer resulting from larger aspect ratio, etc., are expected to bring CAR EUV lithography to it's end soon. While new resist platform such as Metal Oxide Resist (MOR) is expected to provide the needed solution for future, other approaches such as further optimization of the underlayer (UL) could also offer an alternate solution by extending the utilization of CAR. In this paper, we explored the possibility of using spin-on metal-oxide hard mask (SOMHM) materials as UL for CAR EUV lithography. We first demonstrated excellent etch selectivity between CAR and SOMHM UL, as well as that between UL and other hard mask layers such as SOC, SiN or SiOx, in P44 pattern transfer study. Further P32 full wafer investigation allowed us to examine the critical parameters such as LER and LWR. Studies of even smaller pitches of 28nm and 24nm showed more advantages of SOMHM UL due to the etch budget limit of CAR. The possibility of simplifying the standard tri-layer stack is also demonstrated by using SOMHM as the direct hard mask for pattern transfer into 60nm SiN.

With the "first light" of high Numerical Aperture (NA) scanner announced by ASML earlier this year, it has become clear that the inevitable resist thickness shrinkage will pose great challenge to pattern transfer with current chemically amplified resist (CAR), on top of other technical challenges including resolution, line roughness and defects. Historically, through the litho stack optimization, and more critically, the underlayer (UL) optimization, the overall litho performance of a given resist system could be largely improved to meet manufacturing needs. In this paper, we propose the possibility of using spin-on metal-oxide hard mask (SOMHM) materials as EUV lithography UL for CAR. By first validating the excellent etch selectivity at P44 L/S between CAR and SOMHM UL, as well as that between UL and other hard mask layers such as SOC, SiN or SiOx, the following P32 full wafer investigation allowed us to examine the critical parameters such as LER and LWR. Studies of even smaller pitches of 28nm and 24nm showed more advantages of SOMHM UL due to the etch budget limit of CAR when thinner resist is required to address some litho pattern defects. The possibility of simplifying the standard tri-layer stack is also demonstrated by using SOMHM as the UL as well as direct hard mask for pattern transfer into 60nm SiN.

The evolution of the photolithographic model has enabled the semiconductor industry to achieve enhanced device efficiency within the consumer electronics domain through the ability to create diminutive shapes and sizes. This historical progression can be delineated into six discernible periods, all of which are based on fundamental elements of a light source and a lens: broadband, i-line, KrF (248 nm), dry ArF (193 nm), immersion (193 nm), and the present environment belonging to the dynamic and evolving Extreme Ultraviolet (EUV) generation (13.5 nm). Accompanied by this evolution, three supplementary patterning modalities have synergistically evolved to augment and extend the capacities of the lithographic approaches: Reactive Ion Etching (RIE), Chemical Mechanical Planarization (CMP) and Atomic Layer Deposition (ALD). The current EUV generation presents unique scaling challenges such as overlay discrepancies, critical dimension (CD) variance, and EUV exposure capacity limitations. To mitigate these scaling impediments and continue the miniaturization trajectory, Directed Self-Assembly (DSA) represents the nascent fourth era of complimentary patterning. DSA has the potential to tackle the foremost triad of scaling challenges pervading the contemporary industry landscape. In this discourse, we shall explain the profound role of DSA in the future of semiconductor fabrication. Specifically, we will critically assess the readiness to produce DSA materials and their potential for continued extension beyond the existing PS-b-PMMA generation platform.

The adoption of extreme ultraviolet lithography (EUVL) has enabled the manufacturing of semiconductor chips with circuit dimensions below 20nm. Photoresists used in the current EUVL are based on the extension of polymeric chemically amplified photoresist system initially introduced three decades ago. While having been the industry's workhorse since the deep UV era, its limitations have begun to emerge too. With requirements for line edge roughness (LER) approaching single nanometer and resolution falling below 15nm, the inherent large scale and inhomogeneity of polymeric systems lead to great technical challenges. Miniaturization of the building blocks of photoresist is desired for further scaling. In the meanwhile, the demand for higher throughput in lithography process due to the restriction of EUV source power requires faster photo-speed as well. In this study, a molecular resist platform is developed with the superior dose-to-size well below 50mJ/cm(2). The resist forms negative-tone images which is beneficial for printing pillars and isolated lines utilizing dark-field masks. Pillars in hexagonal arrays with pitch below 38nm are patterned with local CD uniformity (LCDU) below 3nm. Thanks to its negative-tone nature, top loss of the resist film is minimal, which results in higher remaining film to sustain the subsequent etch process. The robust design of the molecular core renders the resist film enhanced etch resistance. Pattern transferring into over 15nm silicon layer was demonstrated using a simple stack. The new resists offer a more straightforward solution to print pillars and similar features without tone-inversion process. The negative-tone resists can be combined with the DSA technology to significantly improve cost of ownership. The processes were successfully implemented for both contact hole and line/space patterns with drastically improved pattern quality. LCDU of 1.4nm was achieved for contact hole pattern at pitch of 34nm in hexagonal array. It could be considered as an alternative to EUV double patterning or high-NA EUV processes.

For printing the most critical features in semiconductor devices, single exposure extreme ultraviolet (EUV) lithography is quickly advancing as a replacement for ArF immersion-based multipatterning approaches. However, the transition from 193 nm to 13.5 nm light is severely limiting the number of photons produced by a given source power, leading to photon shot noise in EUV patterns. In addition, inhomogeneous distribution of components inside conventional photoresists is adding to the printing variability, especially when critical dimensions continue to shrink. As a result, stochastic issues leading to rough, non-uniform, and potentially defective patterns have become a major challenge for EUV lithography. A promising solution for this top-down patterning approach is complementing it with bottom-up directed self-assembly (DSA) of block copolymers. In combination with 193i lithography, DSA of lamellae forming block copolymers has previously shown favorable results for defining dense line-space patterns using LiNe flow.1 In this study, we investigate the complementarity of EUV + DSA for rectification of pitch 28 nm line-space patterns. Roughness and defectivity are critical factors that need to be controlled to make these patterns industrially relevant. We look at the impact of DSA material and processing parameters on line edge roughness and line width roughness in order to identify and mitigate the origins of pattern roughness. On the other hand, we also assess the different types of defect modes that are observed by means of optical defect inspection and ebeam review, and study the root causes for their formation. To wrap-up, the benefits of 1X DSA versus 3X DSA are presented by comparing EUV + DSA to LiNe flow.

Metal oxide or metal nitride films are used as hard mask materials in semiconductor industry for patterning purposes due to their excellent etch resistances against the plasma etches. Chemical vapor deposition (CVD) or atomic layer deposition (ALD) techniques are usually used to deposit the metal containing materials on substrates or underlying films, which uses specialized equipment and can lead to high cost-of-ownership and low throughput. We have reported novel spin-on coatings that provide simple and cost effective method to generate metal oxide films possessing good etch selectivity and can be removed by chemical agents. In this paper, new spin-on Al oxide and Zr oxide hard mask formulations are reported. The new metal oxide formulations provide higher metal content compared to previously reported material of specific metal oxides under similar processing conditions. These metal oxide films demonstrate ultra-high etch selectivity and good pattern transfer capability. The cured films can be removed by various chemical agents such as developer, solvents or wet etchants/strippers commonly used in the fab environment. With high metal MHM material as an underlayer, the pattern transfer process is simplified by reducing the number of layers in the stack and the size of the nano structure is minimized by replacement of a thicker film ACL. Therefore, these novel AZ (R) spinon metal oxide hard mask materials can potentially be used to replace any CVD or ALD metal, metal oxide, metal nitride or spin-on silicon-containing hard mask films in 193 nm or EUV process.

It is well known that metal oxide films are useful as hard mask material in semiconductor industry for their excellent etch resistance against plasma etches. In the advanced lithography processes, in addition to good etch resistance, they also need to possess good wet removability, fill capability, in high aspect ratio contacts or trenches. Conventional metal containing materials can be applied by chemical vapor deposition (CVD) or atomic layer deposition (ALD). Films derived from these techniques have difficulty in controlling wet etch, have low throughput and need special equipment. This leads to high costs. Therefore it is desirable to develop simple spin-on coating materials to generate metal oxide hard masks that have good trench or via filling performances using spin track friendly processing conditions. In this report, novel spin-on type inorganic formulations providing Ti, W, Hf and Zr oxide hard masks will be described. The new materials have demonstrated high etch selectivity, good filling performances, wet removal capability, low trace metals and good shelf-life stability. These novel AZ r Spin-on metal hard mask formulations can be used in several new applications and can potentially replace any metal, metal oxide, metal nitride or silicon-containing hard mask films currently deposited using CVD process in the semiconductor manufacturing process.

Significant progresses on 300 mm wafer level DSA (Directed Self-Assembly) performance stability and pattern quality were demonstrated in recent years. DSA technology is now widely regarded as a leading complementary patterning technique for future node integrated circuit (IC) device manufacturing. We first published SMART (TM) DSA flow in 2012. In 2013, we demonstrated that SMART (TM) DSA pattern quality is comparable to that generated using traditional multiple patterning technique for pattern uniformity on a 300 mm wafer. In addition, we also demonstrated that less than 1.5 nm/3 sigma LER (line edge roughness) for 16 nm half pitch DSA line/space pattern is achievable through SMART (TM) DSA process. In this publication, we will report impacts on SMART (TM) DSA performances of key pre-pattern features and processing conditions. 300mm wafer performance process window, CD uniformity and pattern LER/LWR after etching transfer into carbon-hard mask will be discussed as well.

Directed self-assembly (DSA) of block copolymers (BCP) is attracting a growing amount of interest as a technique to expand traditional lithography beyond its current limits. It has recently been demonstrated that chemoepitaxy can be used to successfully direct BCP assembly to form large arrays of high-density features using the ‘LiNe’ flow. This process uses lithography and trim-etch to produce a “prepattern” of stripes of alternating chemical composition, which in turn guide the formation of assembled BCP structures. The entire process is predicated on the preferential interaction of the respective BCP domains with particular regions of the underlying prepattern. The natural and relative strength of these interactions are at least partially responsible for many aspects of the resulting assembled BCP film, including equilibrium morphology, type and persistence of kinetically trapped defects, and domain roughness. This study develops the understanding of how various guiding chemistries ultimately govern BCP morphology and characteristics in the LiNe flow. In particular, the work focuses on how stronger affinity between chemical patterns and the guided BCP film leads to faster assembly, lower ultimate defectivity levels, and better incommensurability tolerance, as well as the relationship between pattern strength and domain roughness. One issue in generating finely controllable chemical patterns is that all materials are affected to some degree by processing, which can modify or weaken the guiding ability of the pattern. This investigation addresses the non-idealities introduced in production processing and explores how this knowledge can be employed in improving BCP DSA for lithography.

Hard masks used in lithography processes play a vital role in pattern transfer to the desired substrate. Hard mask materials can be categorized into organic and inorganic types. Examples of organic type hard masks include amorphous carbon, organo siloxane based materials with reflection control properties. These organic hard masks are deposited either by CVD process or spin-on processes. SiN, SiON and TiN are some examples of inorganic type hard masks and typically these hard masks are deposited through CVD process. In either type, key requirement is etch resistance to either oxygen rich plasma or halogen rich plasma depending on the substrate to be etched away. However, in the advanced lithography processes, in addition to good etch resistance, they also need to possess good wet removability, fill capability in high aspect ratio contacts and trenches. In this paper, we discuss the advances made in the spin-on organic and inorganic hard masks. The spin-on option provides high throughput and several alternate material options compared to CVD option. Spin-on carbon (SOC) is a high carbon containing polymer solution and as a coating material, the polymers need to be soluble in organic solvent and insoluble after curing for coating upper layer materials. Recent progress made in good filling, low outgas, high thermal stability and planarization properties required for double and quadruple patterning is presented. Similarly, novel spin-on type inorganic formulations providing Ti, W, and Zr oxide hard masks with high etch selectivity, wet removal capability and good shelf-life stability are described. These novel AZ(R) Spin-on MHM formulations can be used in several new applications and can potentially replace any metal, metal oxide, metal nitride or silicon-containing hard mask films currently deposited using CVD process in the semiconductor manufacturing process.

Directed self-assembly (DDSA) of block copolymers ((BCP) is attracting a growing amount of interest as a techhnique to expand traditional lithography beyond its current limits. It has reecently been demonstrated that chemoepitaxy can be used to successfully ddirect BCP assembly to form large arrays off high-density features. The imec DSA LiNe flow uses lithography and trim-etch to produce a “prepattern” of cross-linked polystyrene (PS) stripes, which in turn guide the formation of assembled BCPP structures. Thhe entire process is predicated on the preferential interaction of the respective BCP domains with particular regionss of the underlying prepattern. The use of polystyrene as the guiding material is not uniquely required, however, and in fact may not even be preferable. This study investigates an alternate chemistry –– crosslinked poly(methyl methacrylate), X-PMMA, –– as the underlying polymer mat, providing a route to higher auto-affinity and therefore a stronger guiding ability. In addition to tthe advantages of the chemistry under investigation, this study explores the broader theme of extending BCP DSA to other materials.

Directed Self-Assembly (DSA) of Block Co-Polymers (BCP) has become an intense field of study as a potential patterning solution for future generation devices. The most critical challenges that need to be understood and controlled include pattern placement accuracy, achieving low defectivity in DSA patterns and how to make chip designs DSA-friendly. The DSA program at imec includes efforts on these three major topics. Specifically, in this paper the progress in DSA defectivity within the imec program will be discussed. In previous work, defectivity levels of similar to 560 defects/cm(2) were reported and the root causes for these defects were identified, which included particle sources, material interactions and pre-pattern imperfections. The specific efforts that have been undertaken to reduce defectivity in the line/space chemo-epitaxy DSA flow that is used for the imec defectivity studies are discussed. Specifically, control of neutral layer material and improved filtration during the block co-polymer manufacturing have enabled a significant reduction in the defect performance. In parallel, efforts have been ongoing to enhance the defect inspection capabilities and allow a high capture rate of the small defects. It is demonstrated that transfer of the polystyrene patterns into the underlying substrate is critical for detecting the DSA-relevant defect modes including microbridges and small dislocations. Such pattern transfer enhances the inspection sensitivity by similar to 10x. Further improvement through process optimization allows for substantial defectivity reduction.

Directed Self Assembly (DSA) of Block Co-Polymers (BCP) has become an intense field of study as a potential patterning solution for future generation devices. The most critical challenges that need to be understood and controlled include pattern placement accuracy, achieving low defectivity in DSA patterns and how to implement this process as a patterning solution. The DSA program at imec includes efforts on these three major topics.Specifically, in this paper the progress for the templated DSA flow within the imec program will be discussed. An experimental assessment is made based on a 37 nm BCP pitch material. In particular, the impact of different process options is illustrated, and data for CD and placement accuracy of the DSA holes in their template is provided.

Shot noise is a significant issue in EUV lithography, especially in printing small area features like contact holes. This brings about LCDU (Local CD Uniformity) issue and LCDU-sensitivity tradeoff. This paper describes efforts to alleviate this issue through a novel EUV Underlayer (UL) chemistry design approach. The novel component "buffer" was introduced into EUV UL formulations to balance back exposure energy from UL to the resist at different incident positions. Measured back exposure dose from UL shows much lower variation (6 sigma/mean) compared with shot noise of resist absorbed dose. Thus summed energy variation will be suppressed when counting back exposure effect of UL, namely shot noise is reduced. Through reported shot noise model, our calculation suggests 30% sensitivity improvement and 13.4% shot noise suppression can be expected. Actual lithographic evaluations demonstrated simultaneous LCDU and sensitivity improvement. The feasibility of 30% sensitivity improvement by Metal hard mask (MHM) material was tested. The combination of buffer functionalized UL and MHM was modeled.

A new process for directed block co-polymer self-assembly (DSA), AZ (R) SMART (TM), for high resolution line and space patterning was introduced. The SMART process started with photoresist trench patterns generated through common photolithographic processes on top of a thin crosslinked neutral layer. A reactive ion etching (RIE) process removed the neutral layer at bottom of the resist trenches and followed by a resist stripping step which completely removed the resist material and uncovered the neutral surface protected by the resist film during etching step. DSA performances of the resultant SMART chemical pre-patterns without or with extra pinning material brushing step were compared. Results indicated that pinning material enhanced chemical pre-pattern directing power for DSA performance. The chemical pre-pattern without pinning material provided well aligned DSA performance for some specific pre-pattern structure and DSA multiplication factor, but it lacked general performance stability. On the other hand, process with added pinning material was demonstrated with stable performance for variable pre-pattern pitches with different DSA multiplication factors. SMART DSA pattern profile and its pattern etching transfer into hard masks were investigated.

As directed self-assembly (DSA) has gained momentum over the past few years, questions about its application to high volume manufacturing have arisen. One of the major concerns is about the fundamental limits of defectivity that can be attained with the technology. If DSA applications demonstrate defectivity that rivals of traditional lithographic technologies, the pathway to the cost benefits of the technology creates a very compelling case for its large scale implementation. To address this critical question, our team at IMEC has established a process monitor flow to track the defectivity behaviors of an exemplary chemo-epitaxy application for printing line/space patterns. Through establishing this baseline, we have been able to understand both traditional lithographic defect sources in new materials as well as new classes of assembly defects associated with DSA technology. Moreover, we have explored new materials and processing to lower the level of the defectivity baseline. The robustness of the material sets and process is investigated as well. In this paper, we will report the understandings learned from the IMEC DSA process monitor flow.