In this work, thin inorganic ALD-deposited capping layers are integrated into polymer-based redistribution layer (RDL) processes with 2–4 $\mu \mathrm{m}$ line/space. The primary objective of enhanced reliability is shown, with secondary process improvements detailed. Impact and respective mitigation on Lithography process reviewed and the introduction of the capping etch are further detailed.

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.

Thin films of crystalline porous materials have great potential in membranes, sensors, and microelectronics. Still, characterizing their pore size, pore volume, and specific surface area is challenging. In article number 2006993, Rob Ameloot and co-workers discuss positron annihilation lifetime spectroscopy, represented by the bees lighting up inside the honeycomb, in comparison to physisorption methods, symbolized by the quantification of honey in the pores.

Thin films of crystalline and porous metal–organic frameworks (MOFs) have great potential in membranes, sensors, and microelectronic chips. While the morphology and crystallinity of MOF films can be evaluated using widely available techniques, characterizing their pore size, pore volume, and specific surface area is challenging due to the low amount of material and substrate effects. Positron annihilation lifetime spectroscopy (PALS) is introduced as a powerful method to obtain pore size information and depth profiling in MOF films. The complementarity of this approach to established physisorption‐based methods such as quartz crystal microbalance (QCM) gravimetry, ellipsometric porosimetry (EP), and Kr physisorption (KrP) is illustrated. This comprehensive discussion on MOF thin film porosimetry is supported by experimental data for thin films of ZIF‐8.

The native self-alignment of area-selective deposition (ASD) processes makes this technology a promising solution for precise pattern positioning in the EUV era. The key challenge for any ASD process is its defectivity associated with the deposition on the growth-inhibiting surface. Therefore, the ability to qualify an ASD process using the appropriate set of in-line metrology tools is crucial for up-scaling of the technology. In this work, we present a new concept of area-selective ALD TiO2 growth and use it as an example to show the potential of in-line OCD and XPS tools for evaluation of ASD processes. The proposed novel process is based on selective growth of TiO2 on top of SiO2/SiN in the presence of plasma halogenated amorphous carbon (a-C:H) acting as a growth-inhibiting layer. The exposure of a-C:H to CF4 or Cl2 plasma results in formation of a thin halogen-rich film suppressing nucleation of TiO2, while the latter is minimally affected on the plasma treated SiNx or SiO2 layers. The selectivity was assessed on both blanket films and 45 nm half-pitch a-C:H line patterns. The analysis of blanket a-C:H substrates showed that the plasma chlorination provides a substantially more efficient growth inhibition as compared to the fluorination. However, the ability of the CF4-plasma to etch the topmost surface of the a-C:H makes it more favorable for application on a-C:H patterns, surface of which is typically contaminated with residues from hard-mask or from the patterning plasma. Therefore, the pre-cleaning of the a-C:H line pattern surface with CF4-plasma is required to restore the growth blocking efficiency of the chlorinated a-C:H.

Selective ALD of Ru on Si-based materials with simultaneous ALD inhibition on the amorphous carbon surface enabled by remote H plasma.

This study describes the damage caused by physical vapor deposition of TaN/Ta barriers on porous self-assembled organosilica low-k dielectrics for IC applications. It is demonstrated that the ion bombardment associated with TaN layer sputtering strongly influences the metal species in-diffusion and modifies the bulk dielectric and pore sealing characteristics. The modulation of the pore structure via controlled decomposition of the organic template, prior to the barrier deposition step, allows to mitigate this damage. The reduction of open porosity, from nominal 39% down to 26%, is realized by partial retention of the sacrificial organic porogen phase in the pores of the low-k dielectric, resulting in the suppression of deep Ta penetration and in the recovery of pore sealing. This approach is successfully tested in a 45 nm half-pitch damascene vehicle. The compatibility of the organic template residues with the subsequent steps of the interconnects integration process flow, such as hard-mask deposition and patterning, are discussed.

The performance of modern chips is strongly related to the multi-layer interconnect structure that interfaces the semiconductor layer with the outside world. The resulting demand to continuously reduce the k-value of the dielectric in these interconnects creates multiple integration challenges and encourages the search for novel materials. Here we report a strategy for the integration of metal-organic frameworks (MOFs) as gap-filling low-k dielectrics in advanced on-chip interconnects. The method relies on the selective conversion of purpose-grown or native metal-oxide films on the metal interconnect lines into MOFs by exposure to organic linker vapor. The proposed strategy is validated for thin films of the zeolitic imidazolate frameworks ZIF-8 and ZIF-67, formed in 2-methylimidazole vapor from ALD ZnO and native CoOx, respectively. Both materials show a Young's modulus and dielectric constant comparable to state-of-the-art porous organosilica dielectrics. Moreover, the fast nucleation and volume expansion accompanying the oxide-to-MOF conversion enable uniform growth and gap-filling of narrow trenches, as demonstrated for 45 nm half-pitch fork-fork capacitors.

Robust and scalable thin film deposition methods are key to realize the potential of metal-organic frameworks (MOFs) in electronic devices. Here, we report the first integration of the chemical vapor deposition (CVD) of MOF coatings in a custom reactor within a cleanroom setting. As a test case, the MOF-CVD conditions for ZIF-8 are optimized to enable smooth, pinhole-free, and uniform thin films on full 200 mm wafers under mild conditions. The single-chamber MOF-CVD process and the impact of the deposition parameters are elucidated via a combination of in situ monitoring and ex situ characterization. The resulting process guidelines will pave the way for new MOF-CVD formulations and a plethora of MOF-based devices.

The effect of the replacement of Si–O–Si by Si–CH2–Si groups on the mechanical and electrical properties of silica-based hybrid sol–gel thin films is reported.

Integrating bottom-up area-selective building-blocks in microelectronics has a disruptive potential because of the unique capability of engineering new structures and architectures. Atomic layer deposition (ALD) is an enabling technology, yet understanding the surfaces and their modification is crucial to leverage area-selective ALD (AS-ALD) in this field. The understanding of general selectivity mechanisms and the compatibility of plasma surface modifications with existing materials and processes, both at research and production scale, will greatly facilitate AS-ALD integration in microelectronics. The use of self-assembled monolayers to inhibit the nucleation and growth of ALD films is still scarcely compatible with nanofabrication because of defectivity and downscaling limitations. Alternatively, in this Research Article, we demonstrate a straightforward H2 plasma surface modification process capable of inhibiting Ru ALD nucleation on an amorphous carbon surface while still allowing instantaneous nucleation and linear growth on Si-containing materials. Furthermore, we demonstrate how AS-ALD enables previously inaccessible routes, such as bottom-up electroless metal deposition in a dual damascene etch-damage free low-k replacement scheme. Specifically, our approach offers a general strategy for scalable ultrafine 3D nanostructures without the burden of subtractive metal patterning and high cost chemical mechanical planarization processes.

In this work, we studied low-field leakage currents in the self-assembly based spin-on low-k dielectrics (k = 2.2) as it may be affected by the degree of the organic template decomposition. The distinct role of the template residues could be examined due to the remarkably different rate of organosilica matrix cross-linking and template decomposition during the hard-bake process. We found that the incomplete decomposition of the sacrificial organic phase is responsible for increased low-field leakage current through the dielectric. The analysis of photocurrent spectra and the results of electron resonance spectroscopy suggest that the degradation of electrical performance can be attributed to the presence of defect states ∼5 eV below the insulator conduction band induced by the residues in the form of oxidized sp3-carbon chains. The lowest leakage current is attained in the template-free material obtained by introduction of additional broadband UV-assisted curing (λ > 200 nm).

Polymer grafting of pore sidewalls is studied as a protecting agent against processing damage. Polymethyl-methacrylate (PMMA), an improved polystyrene (PS-pro), and a tailored plasma damage management polymer (PDM) are considered as potential candidates. PMMA and PS-pro show nonhomogeneous grafting properties, while PDM coat the pore sidewalls uniformly through the bulk of the porous low-k film. A k ∼ 2.2 porous spin-on glass is used as a vehicle for processing damage study. Approximately one monolayer is grafted on the pore walls, leading to a k-value increase up to Δk ∼ 0.2. Using grafted PDM, the porous low-k chemical stability in 0.5% diluted hydrofluoric acid is significantly improved. Concerning plasma damage, at constant etch depth methyl depletion is decreased, mainly in capacitive coupled plasma discharge showing high polymerizing character, leading to similar damage depth as found for a reference organo-silicate glass 2.7 low-k. However, moisture uptake is not improved, leading to significant drift in the dielectric constant.

The impact of terminal and linking organic groups on the mechanical stability of self-assembly based porous ultralow-k dielectrics was investigated by nanoindentation and four-point bending tests in conjunction with quantitative FTIR analysis. Using a set of six porous low-k dielectric films functionalized with alkyl- and aryl-based groups, we demonstrated that both elastic and fracture properties can be sensitive to the type of embedded linking or terminal groups. Based on the obtained correlations between the material composition and the mechanical properties, two approaches for improvement of fracture toughness in low-k dielectrics are proposed.

This paper describes an approach for the reduction of plasma-induced damage in self-assembly based porous ultra low-k organosilica dielectrics. The concept is based on retention of the partially decomposed sacrificial organic phase (template) into the pores of the low-k film during plasma exposure. The amount of the template residues can be controlled by varying the hard-bake process time. It is shown that those residues are uniformly distributed throughout the film in the form of pore wall coatings. After plasma processing, the remaining residues are removed by means of a UV cure. Plasma damage to the underlying organosilica matrix was assessed by exposure of the differently hard-baked low-k films to fluorine-rich Ar/SF6 plasma. The thickest coating, estimated to be around 0.4 nm, enables a nearly damage-free etch process without any carbon depletion or k-value degradation along with limited shrinkage induced by post-etch UV-curing (<4.5%). These results highlight the efficiency of a simple and scalable route for damage-free integration of highly porous self-assembly based low-k dielectrics.

An analytical approach allowing to analyze effect of porosity, pore size, and interconnectivity on dielectric constant of organosilicate based low-k materials is developed. Within the framework of this approach, a good agreement between the calculated and experimentally measured dielectric constants for several porogen (template) based organosilicate glasses low-k films is demonstrated. It is shown that the best agreement between the calculated and measured k-values corresponds to low-k structure with CH3 groups localized on pore wall surface. The results also demonstrate a good agreement with recently published results of similar analysis based on numerical approach.

An analytical approach allowing to analyze effect of porosity, pore size, and interconnectivity on dielectric constant of organosilicate based low-k materials is developed. Within the framework of this approach, a good agreement between the calculated and experimentally measured dielectric constants for several porogen (template) based organosilicate glasses low-k films is demonstrated. It is shown that the best agreement between the calculated and measured k-values corresponds to low-k structure with CH3 groups localized on pore wall surface. The results also demonstrate a good agreement with recently published results of similar analysis based on numerical approach. (C) 2016 American Vacuum Society.

Interconnects pose increasing challenges as technology scaling proceeds. In order to overcome these challenges simultaneous optimization of novel metallization schemes, new materials, circuit and system level approaches are required.