Traditional transistor miniaturization has long driven performance gains in integrated circuits. However, as transistors and their connecting copper wires shrink into the sub-10 nanometer regime, the surrounding protective layers—essential for maintaining electrical integrity—resist further reduction. These layers, typically tantalum-based barrier and liner materials, must maintain a minimum thickness of around four nanometers. In future nanoscale interconnects, these coatings may consume nearly half the cross-sectional area of the copper wiring, severely throttling electrical conductivity and device speed. The NUS and Applied Materials team’s innovation resides in synthesizing an ultrathin WS₂ film, less than a nanometer thick, that simultaneously fulfills the dual role of barrier and liner, drastically slashing thickness without compromising performance.

This pioneering coating, grown on industry-standard 200-millimeter silicon wafers using a low-temperature thermal atomic layer deposition process at 350 degrees Celsius, exemplifies a remarkable confluence of scalability and compatibility. The process avoids plasma, guaranteeing conformal deposition with precise thickness control down to a single atomic layer. Notably, this method achieves uniform coverage in high aspect ratio trenches, exceeding 95% conformity even at depth-to-width ratios of 10:1. Such attributes position this WS₂ monolayer as a viable drop-in replacement within existing semiconductor fabrication lines, bridging the formidable divide between laboratory breakthroughs and industrial applicability.

The WS₂ film’s threshold thickness of approximately 0.7 nanometers contrasts starkly with the conventional six nanometer standard, enabling a future 20-nanometer-wide copper wire to retain over 90% of its conductive cross-section. This relatively unobstructed copper path translates into reduced electrical resistance and elevated current carrying capacity, directly enhancing chip speed and energy efficiency. Extensive electrical testing demonstrated a monumental reduction in resistance—exceeding a factor of one million—compared to uncoated counterparts. The superior adhesion properties offered by the WS₂ liner promote smooth and continuous copper film formation, vital for producing reliable, defect-free interconnects at such ultrathin dimensions.

Beyond adhesion, the WS₂ monolayer serves as a robust diffusion barrier that impedes copper migration into silicon and dielectric materials under thermal and electrical stress. In accelerated aging tests, conventional barrier-free copper rapidly reacted with underlying silicon, forming deleterious intermetallic compounds and defect clusters. In stark contrast, WS₂-coated samples exhibited no such degradation, maintaining pristine interfaces even after prolonged exposure. Remarkably, devices using the atomically thin barrier exhibited projected lifetimes surpassing unprotected designs by an order of magnitude, signaling a dramatic leap in device durability.

Central to the WS₂ film’s efficacy is its polycrystalline structure composed of myriad tiny grains and grain boundaries arranged in random orientations. Unlike continuous single crystals, where aligned grain boundaries can form direct diffusion channels, the staggered grain orientation in multilayer WS₂ films creates a complex labyrinth that frustrates copper atom penetration akin to the staggered offsets in a well-built brick wall. This insight, derived from computational modeling by NUS chemists, identifies nanoscale grain architecture as a key parameter in optimizing barrier functionality, challenging the entrenched paradigm that perfect crystallinity is always advantageous.

The discovery that a single atomic layer can supplant the combined barrier and liner stack confronts long-held assumptions in semiconductor interconnect design. Prior industry standards dictated separate layers with cumulative thicknesses of several nanometers to provide necessary protection and adhesion. By collapsing these essential roles into an atomically thin WS₂ sheet, researchers open new vistas for continuing Moore’s Law scaling into unprecedented regimes. Professor Silvija Gradečak, co-director of the NUS-Applied Materials Corporate Lab, emphasizes that this fundamental shift in approach heralds a new class of interconnect architectures tailored to atomically precise materials engineering.

The process’s compatibility with low thermal budgets—vital for avoiding damage to complex multilayer device stacks—and its wafer-scale uniformity underscore its readiness for integration into contemporary manufacturing ecosystems. These breakthrough properties allow semiconductor producers to adopt WS₂-based coatings without extensive equipment overhauls or processing disruptions, facilitating rapid technology transfer. Dr. Hippolyte Astier highlights that such advancements transcend the immediate generation of chips, positioning the industry to harness this technology across multiple forthcoming innovations extending out to 2037 and beyond.

Applied Materials’ Director of Engineering, Dr. John Sudijono, notes the criticality of merging academic ingenuity with industrial constraints through the Corporate Lab framework. The collaborative environment enabled iterative validation of WS₂ films under realistic fabrication conditions, ensuring the material meets demanding reliability, scalability, and process compatibility benchmarks. This convergence of theory, experimentation, and commercialization is essential to bridging the notorious gulf between laboratory demonstrations and full-scale production deployments in semiconductor manufacturing.

Looking forward, the team is exploring refined control over WS₂ grain orientation and microscopic interface phenomena to fine-tune long-term stability and electrical behavior. Further studies aim to exploit the low-temperature vapor-phase growth technique to deposit other two-dimensional materials within diverse chip components, expanding the scope of atomic-scale coatings in integrated circuit design. This foundational research not only sets a new standard for interconnect barriers and liners but also signals the inception of a broader materials revolution in microelectronics.

The ultrathin WS₂ monolayer innovation thus represents a monumental stride towards sustaining the pace of semiconductor evolution. By ingeniously combining barrier and liner functionality into a single atomic layer with industrially scalable fabrication, this discovery resolves a pressing miniaturization bottleneck, empowering the continuation of chip performance scaling in an era where every nanoscale dimension counts. As the semiconductor industry confronts the ultimate physical limits of transistor and interconnect shrinking, atomically precise materials like WS₂ will be vital enablers of future computational breakthroughs, underpinning the technology transformations of tomorrow.

Subject of Research: Not applicable

Article Title: Low-temperature wafer-scale growth of ultrathin tungsten disulfide for bifunctional interconnect barriers and liners

News Publication Date: 31-Mar-2026

Web References: https://doi.org/10.1038/s41928-026-01592-6

Image Credits: College of Design and Engineering, NUS

Keywords

Semiconductors, Microelectronics, Materials engineering, Materials science

Ultrawide-bandgap semiconductors possess a unique advantage over traditional semiconductor materials like silicon. Their much larger energy gap—over 4 electron volts—enables them to manage higher voltages and operate efficiently at elevated frequencies. However, probing these intriguing materials has presented a considerable challenge due to their unique optical properties, most notably their transparency to visible light. Professors Margaret Murnane and Henry Kapteyn, both affiliated with JILA and the University of Colorado, led a team that sought to overcome these hurdles by developing a novel microscopy setup that could engage with these materials using high-energy DUV light.

Conventional optical microscopy techniques rely heavily on visible light, which, due to its limitations, is not suitable for examining materials with large energy gaps such as diamond. This presents an obstacle, as visible light cannot effectively excite charge carriers within these materials. Consequently, researchers struggled to explore the electronic and thermal properties of diamond and similar semiconductors, which are pivotal in high-performance applications. The JILA team devised a new methodology to utilize DUV lasers to create a nanoscale interference pattern that enhances the investigation of these elusive materials.

The innovation lies in the design of a compact microscope that harnesses DUV light to generate a nanoscale transient grating on the material’s surface. By modulating the energy and wavelength of laser light, the researchers successfully converted it to DUV wavelengths, ultimately achieving a remarkable range of around 200 nanometers through the strategic manipulation of nonlinear crystals. This technique underscores the intricate process of optical alignment and energy conversion—a feat that took years of meticulous experimentation, especially compounded by the challenges posed by the COVID-19 pandemic.

To investigate how heat and charge transport characteristics unfold at a nanometer scale, the team employed a transient grating created by splitting the DUV light into two beams. These beams interfered with one another, forming a precise standing wave of alternating high and low energy regions on the diamond’s surface. This innovative approach allowed the team to heat the material in a controlled fashion while enabling them to study phenomena such as the diffusion of electrons and holes—essential charge carriers in the diamond’s structure—without altering the material itself or introducing any undesirable modifications.

Following the establishment of the DUV transient grating system, the team set about validating its accuracy through a series of tests conducted on well-known materials. Thin layers of gold served as a benchmark for the initial experiments, allowing the researchers to generate nanoscale heat patterns and observe the resultant acoustic waves traveling across the surface. Analyzing the frequencies and behaviors of these waves not only confirmed the system’s adeptness in examining material properties but also established a solid framework for future experiments.

The significance of this advancement extends beyond confirming its capabilities; it sets a new precedent for understanding diamond’s exceptional electronic and thermal characteristics. Previous methods that necessitated physical alterations or coatings could distort the material properties and obscure valuable insights. The DUV microscope, however, permitted the exploration of diamond in its pristine form. By closely analyzing the transport dynamics of charge carriers in response to laser excitation, the researchers gleaned new perspectives on their interactions and the resulting impacts on material behavior.

In addition to studying diamond, this innovative microscope has broader implications for understanding heat transport at the nanoscale. Traditional models assume a smooth and continuous flow of energy carriers, but observations in this field have unveiled more complex behaviors such as ballistic and hydrodynamic transport. In these scenarios, phonons—quantized sound waves—can travel considerable distances without scattering or spread in forms reminiscent of fluid dynamics. As the JILA team delves deeper into the properties of various materials, they stand at the precipice of unraveling crucial aspects of nanoscale physics.

The collaboration between JILA researchers and industry partners exemplifies a dynamic exchange of knowledge that fuels scientific progress. When 3M approached the team with a challenge to study a unique ultrawide-bandgap material, it propelled the researchers to break from traditional methodologies and innovate a solution tailored to contemporary needs. This collaboration showcases the intersection of academia and industry, emphasizing the importance of knowledge sharing in driving advancements in materials science.

As this research progresses, the implications for fields ranging from power electronics to communication technologies remain profound. By embracing the unique properties of ultrawide-bandgap materials such as diamond, scientists are not only aiming to enhance performance metrics but also to explore new paradigms for device fabrication and efficiency. This pioneering work will undoubtedly inspire future explorations into the properties of a variety of materials, potentially unlocking new frontiers in nanoscience.

Rigorous validation of experimental setups will continue to be a priority for the team, as they seek to ensure the precision and reliability of their findings. The successful synergy between experimental results and theoretical models serves as a testament to the robustness of their techniques and the potential for future discoveries in the realm of semiconductor physics. The findings paves the way for other researchers in the field, facilitating a pathway for broader applications and enhancements in technology.

As researchers hone their techniques and expand their understanding, the quest to optimize material properties for next-generation devices remains ongoing. The journey into the complexities of nanoscale material interactions is just beginning. The implications of these findings for future technologies are vast, offering promising avenues for improved efficiency and performance in various industrial applications. With continued exploration, the insights gained will reverberate through multiple domains within materials science, fostering innovative solutions for tomorrow’s technological challenges.

The transformative potential of this new DUV microscopy technique is evident, shedding light on a multitude of promising materials and the unique properties that define them. By meticulously observing their behaviors at the nanoscale, scientists can inform the design of more effective electronic components, high-frequency devices, and communication systems. As the team shares their breakthroughs with the scientific community, the excitement surrounding this novel approach highlights the ever-evolving landscape of physics and the materials that comprise the foundation of modern technology.

Subject of Research: Ultrawide-bandgap Semiconductors
Article Title: Novel DUV Microscopy Technique Sets New Basis for Understanding Diamond and Other Advanced Materials
News Publication Date: October 2023
Web References: https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.22.054007
References: DOI – 10.1103/PhysRevApplied.22.054007
Image Credits: Steven Burrows/Murnane and Kapteyn groups

Keywords

Deep-ultraviolet microscopy, ultrawide-bandgap semiconductors, diamond, nanoscale transport, JILA, Murnane and Kapteyn groups, power electronics, high-frequency communication.