The IC manufacturing industry faces multiple challenges when employing patterning techniques at dimensions below 10 nm, aided by concepts such as litho-etch processes and self-aligned multiple patterning. Common issues include stochastic defects, line edge roughness, overlay errors and pattern collapse of photoresists. Area-selective deposition (ASD) as a bottom-up concept, presents a promising solution to mitigate some of these challenges with atomic-level accuracy. One effective approach to achieve ASD involves patterning organic monolayers using optical lithography in conjunction with a photocatalytic underlayer. This can be employed for Ru hard mask concepts. In this study, titanium oxide (TiO2) serves as the photocatalytic layer, which is passivated with organosilane self-assembled monolayers (SAMs) featuring methyl and fluorine terminations. Upon exposure to deep ultraviolet (DUV) light, fragmentation of the SAM molecules occurs due to a mechanism involving electron-hole pair generation in the presence of photocatalytic TiO2. This fragmentation in the exposed regions facilitates selective deposition of Ru. Furthermore, the selectivity is also influenced by the choice of precursor used for the subsequent Ru ASD, as demonstrated by comparing tricarbonyl (trimethylenemethane) ruthenium (Ru(TMM)(CO)3) and (ethylbenzyl)(1-ethyl-1,4-cyclohexadienyl) ruthenium (EBECHRu) precursors. Lastly, the mechanisms of Ru defect formation on the SAM-passivated areas are discussed in detail. Vapor-phase deposition of short-chain TMOS SAM was found to provide more effective surface passivation than immersion-based methods.

Future semiconductor device architectures necessitate innovative patterning processes. Area-selective etching (ASE) of polymers is a self-aligned patterning technique with significant potential for the future semiconductor fabrication. In the ASE process, etchant gas penetrates the polymer film and becomes activated by the underlying catalytic material. Consequently, at the correct temperature, the polymer layer is selectively decomposed above the catalytically active areas, while it remains unaltered above catalytically inactive areas. This area-selective process ensures self-alignment, thus preventing edge placement errors. The resulting patterned polymer can be utilized in subsequent area-selective deposition or lift-off processes. In this article, we study ASE of poly(methyl methacrylate) (PMMA) and poly(lactic acid) by first testing several metal oxide and nitride surfaces, namely, Al2O3, HfO2, ZrO2, Ta2O5, CeO2, NiO, TiO2, TiN, and Si3N4, for their catalytic effect in an O-2, H-2, and inert atmosphere. The experiments reveal that most of these surfaces are noncatalytic, therefore requiring activation. We demonstrate that a noncatalytic surface (HfO2) can be easily converted to catalytic by depositing a small amount of catalytic material (CeO2) on top. We then create a test structure by patterning another noncatalytic material (TiO2) on top with direct atomic layer processing, after which we use ASE of PMMA to create a patterned inhibition layer. This inhibition layer is then used in area-selective atomic layer deposition of ZrO2. Additionally, we show that the polymer flow during the ASE process can be significantly reduced by increasing the molecular weight of the polymer.

Nanopatterned electrodes (nominal trench width = 45 nm) have been generated to enable electrochemical measurements of metals in a damascene integration scheme. Fabrication is done at 300 mm wafer scale using standard semiconductor technology processes. A morphological characterization of a wet-chemical Cu digital etching process is performed using transmission electron microscopy and atomic force microscopy, both of which provide insights into the material properties and surface features. Results reveal that recess depth increases linearly with etching cycles and indicate pit formation on the Cu surface. To validate the backside contact approach, electrical and electrochemical measurements of both Cu-filled and Ru-coated nanopatterned electrodes are performed, which show the typical metal behavior. As an application, the surface coverage of self-assembled monolayer modified Cu in damascene trenches is investigated by measuring cyclic voltammograms in an alkaline solution, demonstrating the quality of passivation using a test structure for which all materials (conductor metal, barrier/liner, and low-k dielectric) relevant for the application area-selective deposition are present.

Integrating metal-organic frameworks (MOFs) into microfabrication processes will benefit from controlled vapor-phase deposition techniques. This study presents a molecular layer deposition method that enables area-selective and oriented growth of zeolitic imidazolate framework-8 (ZIF-8) films. Substrates functionalized with self-assembled monolayers (SAMs) with different end groups (alkyl, phenyl, hydroxyl, carboxyl, amine, and imidazole) allow tuning the degree of crystallographic orientation in the resulting MOF layers. Spatial control over SAM formation determined the surface mobility of the ZIF-8 building blocks, which enabled area-selective deposition.

In the original publication [...].

Area selective deposition (ASD) is a promising IC fabrication technique to address misalignment issues arising in a top–down litho-etch patterning approach. ASD can enable resist tone inversion and bottom–up metallization, such as via prefill. It is achieved by promoting selective growth in the growth area (GA) while passivating the non-growth area (NGA). Nevertheless, preventing undesired particles and defect growth on the NGA is still a hurdle. This work shows the selectivity of Ru films by passivating the Si oxide NGA with self-assembled monolayers (SAMs) and small molecule inhibitors (SMIs). Ru films are deposited on the TiN GA using a metal-organic precursor tricarbonyl (trimethylenemethane) ruthenium (Ru TMM(CO)3) and O2 as a co-reactant by atomic layer deposition (ALD). This produces smooth Ru films (<0.1 nm RMS roughness) with a growth per cycle (GPC) of 1.6 Å/cycle. Minimizing the oxygen co-reactant dose is necessary to improve the ASD process selectivity due to the limited stability of the organic molecule and high reactivity of the ALD precursor, still allowing a Ru GPC of 0.95 Å/cycle. This work sheds light on Ru defect generation mechanisms on passivated areas from the detailed analysis of particle growth, coverage, and density as a function of ALD cycles. Finally, an optimized ASD of Ru is demonstrated on TiN/SiO2 3D patterned structures using dimethyl amino trimethyl silane (DMA-TMS) as SMI.

Perfluorododecyl iodide (I-PFC12) is of interest for area-selective deposition (ASD) applications as it exhibits intriguing properties such as ultralow surface energy, the ability to modify silicon’s band gap, low surface friction, and suitability for micro-contact patterning. Traditional photolithography is struggling to reach the required critical dimensions. This study investigates the potential of using I-PFC12 as a way to produce contrast between the growth area and non-growth areas of a surface subsequent to extreme ultraviolet (EUV) exposure. Once exposed to EUV, the I-PFC12 molecule should degrade with the help of the photocatalytic substrate, allowing for the subsequent selective deposition of the hard mask. The stability of a vapor-deposited I-PFC12 self-assembled monolayer (SAM) was examined when exposed to ambient light for extended periods of time by using X-ray photoelectron spectroscopy (XPS). Two substrates, SiO2 and TiO2, are investigated to ascertain the suitability of using TiO2 as a photocatalytic active substrate. Following one month of exposure to light, the atomic concentrations showed a more substantial fluorine loss of 10.2% on the TiO2 in comparison to a 6.2% loss on the SiO2 substrate. This more pronounced defluorination seen on the TiO2 is attributed to its photocatalytic nature. Interestingly, different routes to degradation were observed for each substrate. Reference samples preserved in dark conditions with no light exposure for up to three months show little degradation on the SiO2 substrate, while no change is observed on the TiO2 substrate. The results reveal that the I-PFC12 SAM is an ideal candidate for resistless EUV lithography.

Area-selective deposition (ASD) is a technique to deposit material only on a defined area of a prepatterned surface, while no deposition occurs on adjacent surface areas. It is the subject of intense investigations by the scientific and engineering communities as it offers the prospect to simplify and improve patterning processes for fabrication of nanoelectronic devices as well as to reduce the manufacturing costs. Numerous efforts have been dedicated to identify process conditions for highly selective ASD processes. Still, the search for optimal conditions is often an empirical process due to the limited understanding of the mechanisms that take place at the atomic scale. Understanding the links between precursor reactivity, surface treatments, and the reactor operating conditions could greatly contribute to the development of highly selective ASD processes. In this paper, we therefore combine first-principles calculations with statistical thermodynamics to understand the role of the precursors in area-selective TiO2 atomic layer deposition (ALD). First, we investigate the selectivity loss mechanisms for TiCl4/H2O ALD on SiO2 nongrowth surfaces with different surface terminations (e.g., OH groups and trimethylsilyl groups). We link the resulting thermodynamic driving forces to experimental reports. Subsequently, we extend the investigation to a total of 26 commercially available titanium precursors and to three different oxygen sources and rank their potential for TiO2 ASD for the SiO2 surfaces with different surface terminations (OH groups and trimethylsilyl groups). We find that the combination of TiCl4 with H2O offers the best performance in terms of selectivity. The theoretical approach proposed here is expected to greatly assist and accelerate the design of precursors for different ASD approaches.

The rush for better-performing electronics, and manufacturing processes that heavily rely on "top-down" patterning techniques, is making the integration of "self-aligned" fabrication methods, such as area-selective deposition (ASD), a critical objective for continued device scaling. The fully self-aligned via (FSAV) scheme is broadly proposed as a "killer application" to determine whether ASD can shift from an R&D process to high-volume manufacturing. Nevertheless, the lack of a suitable low-κ deposition process has prevented the realization of FSAV by dielectric-on-dielectric ASD. This is primarily due to the high temperature and/or strong oxidizers employed during low-κ dielectric deposition and their unsuitability in the presence of organic masks, such as self-assembled monolayers (SAMs), used to prevent material nucleation during ASD. In this work, AlOx and Al-silicate atomic layer deposition (ALD) processes are studied to provide suitable materials for ASD-enabled FSAV. Dimethylaluminum isopropoxide and H2O are utilized to deposit the metal oxide, whereas Al-silicate is grown by adding 2,2-dimethoxy-1,6-diaza-2-silacyclooctane (DMDAcO) pulses to the AlOx ALD cycle. The selectivity of such processes is demonstrated on 50 nm Cu/SiO2 structures, using octadecanethiol-derived SAMs to inhibit material nucleation on the metal lines. Scanning and transmission electron microscopies are employed to assess the quality of the ASD processes and investigate the mechanisms behind defect generation on a nongrowth surface. X-ray photoelectron spectroscopy measurements show the high purity of the AlOx film, whereas DMDAcO-ligand incorporation into the Al-silicate matrix is observed. Planar capacitor structures are used to assess the electrical properties of both ASD films, revealing that the silicate film exhibits a relatively low κ-value (5.3 ± 0.2), with a high acceleration field factor (32.4 ± 1.4) and a dielectric breakdown voltage of 6.0 ± 0.3 V at 100 °C.

Atomic layer-deposited (ALD) inorganic films were processed on top of copper metal lines in a polymer-based redistribution layer (RDL). The primary objective was to develop capping layers thinner than 15 nm to prevent copper oxidation. Due to their uniformity and high density, ALD layers are established permeation barriers. Nonetheless, owing to the presence of polymers in the final product, a low deposition temperature is required, resulting in an increased defect density and a greater susceptibility to degradation by moisture. In this study, various inorganic cappings, based on Al _2 O _3 , HfO _2 and TiO _2 , deposited at 100 °C were integrated in an RDL stack. It is demonstrated that they impede the reaction of the polymer photo acid generator with copper, improving the lithography process, and ultimately allowing to print smaller critical dimensions. Additionally, capping layers built upon Al _2 O _3 or HfO _2 are shown to fully block copper oxidation after reliability stress tests.

Heterogeneous 3D integration is being hailed as the driver for new technologies due to its stacked device architecture. This increases functionality as the number and length of interconnecting wires decreases, in turn decreasing power consumption. In these advanced packaging technologies, the metal redistribution layers (RDLs) and the insulating polymer surrounding them are crucial components on which stringent reliability requirements are placed. The metal RDL’s are necessary to reroute signals from device level to packaging level. The polymer insulator, used as an alternative to traditional dielectric materials, must (i) be photosensitive to be compatible with lithography processing steps, (ii) possess high mechanical strength, (iii) exhibit good electrical performance, (iv) have a high thermal stability and glass transition temperature, and crucially (v) it must not be hygroscopic. Low or no moisture uptake of the polymer is essential as any moisture can cause mechanical and electrical reliability issues. Absorbed moisture can cause oxidation of Cu lines leading to the well-known problem of Cu diffusion resulting in voids, contact issues, delamination, electromigration and higher leakage currents. Area selective deposition (ASD) could greatly benefit these RDL’s by preferentially depositing an oxygen barrier to stop the oxidation of the Cu lines. The proprietary polymer used in this work is part of the WPR series by JSR Corporation and is a thermosetting phenol-based polymer which displays a high mechanical stability as it contains rubber nanoparticles, 70 nm in diameter. These are added to the polymer to increase the toughness and to prevent cracks and fractures forming and propagating through the film. However, achieving ASD with this polymer is difficult as the polymer is designed to have good adhesion properties so it will easily adhere to the Cu in the metal lines, and there are two materials of interest to passivate, the polymer itself and the rubber nanoparticles. In this work the surface is passivated by utilizing a polymerizing octafluorocyclobutane (C4F8) plasma which creates a Teflon-like film on the surface. The surface morphology and hydrophobicity are investigated to assess the best plasma exposure time, which was found to be 30 s. Surface chemistry from XPS analysis reveals surface modification through the deposition of fluorine rich groups from the 30 s C4F8 plasma exposure, Figure 1(a). Water contact angle measurements reveal an initial hydrophobic surface (~94°) but this hydrophobicity decreases over the course of several seconds. Following the 30 s C4F8 plasma exposure, the hydrophobicity increases significantly to above 110° and remains stable as shown in Figure 1(b). Surface morphology studies carried out by AFM demonstrates no increase in surface roughness following plasma exposure, Figure 1(c) and (d). ALD tests show the process to be selective to the tetrachloride family of ALD precursors. No selectivity was observed with tetrakis (dimethylamino) or isopropoxide based precursors. This process has the capability to block approximately 2 nm of TiO2 and HfO2 from these tetrachloride precursors. Studies of the same process on Cu substrates show that the metal surface is only temporarily modified, and ALD growth can still take place. Reliability stress and corrosion tests were performed to assess if the selectively deposited barriers could prevent Cu oxidation. Figure 1(a) C 1s XPS spectra showing difference before and after plasma treatment, (b) WCA value increases following plasma treatment, and AFM images in (c) and (d) show no change in the surface following plasma exposure. Figure 1

Patterning below 10 nm with conventional techniques such as Litho-etch (LE*), a subtractive self-aligned multiple patterning process, suffers from limitations due to edge placement errors, decreasing throughput, complexity, pattern collapse, photoresist non-uniformity. Bottom-up processes for fabrication of nano devices by means of Area selective deposition (ASD) are peaking up over top-down approaches to mitigate most of the above-mentioned problems. One of the ways to achieve ASD of an hardmask is by using extreme ultra-violet (EUV, lambda-13.5 nm) lithography to single-step pattern self-assembled monolayers (SAM) on a photosensitive substrate (or layer) followed by atomic layer deposition (ALD). In this work, photo-catalytically active titanium oxide is considered as substrate for the deposition of organosilane SAMs of different chain length. Upon exposure to EUV, fragmentation of SAM's molecules is observed though a mechanism involving electron/hole pair exchange from TiO2. This induces changes in the chemistry of the exposed area, allowing an ALD deposition in the SAM-cleared areas.

Utilising self-assembled monolayers (SAMs) to achieve area-selective atomic layer deposition (AS-ALD) as an approach to bottom-up nanofabrication has recently gained significant attention from the nanoelectronics industry. With the continued downscaling of feature sizes, top-down processing can no longer reach the challenging demands of the industry which requires conformal coating of high aspect ratio vias and a reduction in misalignment errors in multi-layered devices. In this work we attempt to imitate the effects of the ALD oxidation pulse experienced by the SAMs during the AS-ALD process by exposing two SAMs of different chain lengths and different functional groups, (3-trimethoxysilylpropyl)diethylenetriamine (DETA) and octadecyltrimethoxysilane (OTMS), to numerous controlled in-vacuo atomic oxygen exposures with subsequent characterisation by X-ray photoelectron spectroscopy (XPS). We monitor the sequential removal of the deposited monolayers with each successive atomic oxygen exposure for both SAMs. The etch rate is observed to be distinct for the different SAMs, the amino-terminated short chain DETA SAM reveals a linear etch rate while the longer chain OTMS SAM reveals an exponential etch rate. The results presented provide some insights into what characteristics are important for choosing the correct SAM for AS-ALD applications.

Area-selective deposition (ASD), a "bottom-up" substrate-selective material deposition process, is a promising solution to overcome the current limitations experienced in semiconductor manufacturing processes, which rely on "top-down" patterning techniques. To achieve this selective material growth, atomic layer deposition (ALD) is frequently employed in conjunction with a blocking layer to suppress material nucleation on the nongrowth areas. ASD is suitable on many levels of wafer manufacturing; notably, its "bottom-up" nature makes it more impactful at the smallest critical dimensions (CDs), such as sub-10 nm. Nevertheless, the ASD studies at such relevant nanoscale dimensions are very limited or nonexistent. Therefore, we studied ASD enabled by 1-octadecanethiol (ODT)-derived self-assembled monolayer (SAM) passivation on unprecedented scaled-down Cu/SiO2 patterns, targeting ASD of hafnium nitride on 10 nm-wide dielectric spacings. Pulsed force atomic force microscopy nanomechanical characterization proved the tight confinement of the organic layer to the metal lines even on such high-density patterns. In addition, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy (SEM) measurements reveal the selective and conformal deposition of similar to 5.0 nm hafnium nitride film on the 10 nm-wide SiO2 spacings. Nevertheless, it is shown that, as the pattern features shrink, the undesired lateral expansion of the isotropically growing ALD film becomes a more stringent limitation to the ASD resolution. The "monolayer trade-off" associated with the employed passivation to enable ASD is analyzed in this work. In fact, a monolayer-thick blocking film is desired to avoid poisoning of the growth surface, whereas the ASD film lateral expansion could be effectively prevented if thicker passivation films are employed instead.

HfO2 is investigated for its suitability to act as an oxygen and moisture barrier to prevent Cu oxidation in redistribution layers (RDLs) in 3D packaging technologies. HfO2 barriers of varying thicknesses were deposited via atomic layer deposition (ALD) on Cu surfaces and then stressed by (i) high temperature stress and (ii) humidity and thermal stress for 1000 h to ascertain the optimal thickness to prevent oxidation of the Cu. The thickness of the ALD HfO2 film was monitored by ellipsometry, while the extent of Cu oxidation was monitored by focus ion beam prepared SEM cross sections. It is found that ∼9 nm of HfO2 is sufficient to prevent Cu oxidation.

Self-aligned patterning schemes for microelectronics fabrication require area-selective deposition processes. In this context, a sol-gel-based selective dielectric-on-dielectric deposition with respect to metal is reported. The selective deposition is achieved by first de-wetting a solution from the lyophobic surface areas and second ensuring uniform organosilicate polymer deposition during a droplet drying on the lyophilic surface regions. The de-wetting occurs when a critical volume for de-wetting is reached as a result of capillary solution draining. De-wetting from 1 mu m wide lyophobic copper area separating lyophilic rectangular dielectric (SiO2) regions with a width as narrow as 4 mu m is demonstrated. The subsequent solution drying results in a 200 nm thick dielectric film.

Area-selective deposition (ASD) is a "bottom-up" substrate-selective material deposition process, considered as a promising alternative to current "top-down" pattering techniques. The most studied and successful ASD strategies envisage a combination of atomic layer deposition (ALD) and a passivation layer, which prevents material deposition on the non-growth areas. As ASD targets increasingly smaller dimensions, metrology challenges are prominent along with preserving confined film growth. For patterned substrates with nanometric critical dimensions, only a few characterization techniques can be employed to assess the ASD performance. However, these techniques provide no or little insight into the passivation layer. This is a crucial limitation as the blocking film plays a key role in the ASD process. In this work, pulsed force mode atomic force microscopy (AFM) is used to characterize and monitor the quality of the passivation films by measuring the surface energy fluctuations occurring on the patterned substrate undergoing ASD. As the evolution of the relative adhesion force distribution of the sample under ALD conditions is recorded, the octadecanethiol (ODT) coverage on non-growth areas is accurately estimated. The heavily temperature-dependent self-assembled monolayer degradation revealed by the nanomechanical characterization is supported by X-ray photoelectron spectroscopy. As Hf3N4 ALD is performed, the top-down scanning electron microscopy investigation is employed to show the strong relationship between ASD quality upon ALD and pulsed force AFM-derived ODT coverage.

As critical dimensions in integrated circuits continue to shrink, the lithography-based alignment of adjacent patterned layers becomes more challenging. Area-selective atomic layer deposition (ALD) allows circumventing the alignment issue by exploiting the chemical contrast of the exposed surfaces. In this work, we investigate the selective deposition of TiO2 by plasma halogenation of amorphous carbon (a-C:H) acting as a growth-inhibiting layer. On a-C:H, a CF4 or Cl2 plasma forms a thin halogenated layer that suppresses the growth of TiO2, while nucleation remains unaffected on plasma-treated SiO2. The same halogenating plasmas preferentially etch TiO2 nuclei over films and thus enable the restoration of the halogenated surface of amorphous carbon. By embedding the intermediate plasma treatments in the ALD TiO2 sequence, an 8 nm TiO2 layer could be deposited with a selectivity of 0.998. The application of the cyclic process on a 60 nm half-pitch line pattern resulted in the defect-free deposition of TiO2 at the bottom of the trenches. Cyclic fluorination demonstrated better growth inhibition compared to chlorination due to more efficient defect removal and retention of the favorable surface composition during plasma exposure. While exploring the TiO2 nucleation defects at the limit of detection for conventional elemental analysis techniques (<1 × 1014 at/cm2), we additionally highlight the value of imaging techniques such as atomic force microscopy for understanding defect formation mechanisms and accurately assessing growth selectivity.