Views: 0 Author: Site Editor Publish Time: 2025-11-07 Origin: Site
Chemical formula: WCl5
Molecular weight: 361.11
CAS: 13470-14-9
Appearance: Black-green crystals
Melting Point: 242°C
Boiling Point: 297.19°C (estimate)
Tungsten(V) chloride, also known as WCl5, is a fluorine-free tungsten precursor that has been used in recent years to deposit metallic tungsten and tungsten nitride (WNx) thin films in semiconductor processes, especially in atomic layer deposition (ALD) or staged pulse nucleation (PNL) processes, to form tungsten padding or nucleation layers.
Traditionally, tungsten thin films often use tungsten(Ⅵ) chloride (WF6) as a precursor. However, the presence of fluorine can lead to electromigration or diffusion into adjacent components, corroding contacts and reducing device performance.
In contrast, tungsten chloride (WClx) is fluorine-free, with hydrogen chloride (HCl) being the primary reaction byproduct. While HCl is corrosive, its effects are relatively easy to control, avoiding the fluorine contamination and substrate corrosion associated with WF6.
Furthermore, compared to WCl6, WCl5 has a higher saturated vapor pressure at room temperature, making it easier to vaporize and deliver into the deposition chamber, thus achieving a more stable precursor supply in ALD/CVD. This characteristic makes WCl5 a potential alternative to WF6 as a tungsten deposition precursor.
However, WCl5 is a solid at room temperature and remains a low-vapor-pressure precursor. In practical applications, heating of the container and optimization of the supply method are required to ensure a stable vapor flow rate.
Some studies have improved the sublimation behavior of WCl5 by controlling its crystalline phase composition, ensuring a stable output of the precursor during long-term deposition processes. These measures aim to overcome the supply problem of solid precursors and improve the feasibility of WCl5 in industrial deposition equipment.
In the ALD process, WCl5 can undergo self-limiting adsorption on the substrate surface, and then be reduced to metallic tungsten by introducing a reducing gas. For example, alternating pulses of WCl5 with reducing agents such as borane (B2H6), silane (SiH4), or hydrogen can be used to deposit a tungsten nucleation layer. WCl5 can also be used to deposit a bulk tungsten host layer via CVD, resulting in a tungsten film with extremely low or even undetectable chlorine content.
It is important to note that glass containers are preferred for storing solid WCl5 to avoid corrosion. During deposition, the temperature of the container and piping should be maintained within the range of 190-245°C to ensure sufficient vapor pressure for the sublimation of solid WCl5 and to maintain a stable vapor flow during transportation.
Overall, WCl5 has been used as a nucleation layer and host layer for depositing tungsten metal thin films, and tungsten filling in high aspect ratio structures is achievable.
Commonly used typical reducing agents:
Hydrogen, silanes, boranes, and organoborohydrides, etc.
Some studies have attempted to react organoaluminum reagents (such as triethylaluminum) with WCl5, resulting in the formation of a carbide phase (W–C).
WN thin films can serve as diffusion barrier layers for conductors such as copper or ruthenium. Experiments show that an ALD-WN layer with a thickness of approximately 4 nm can still block the diffusion of copper and ruthenium during annealing at temperatures as high as 850°C, exhibiting excellent thermal stability and barrier performance.
Lam Research's patented technology uses PE-ALD at lower temperatures, first introducing NH3 onto the dielectric surface to adsorb and decompose it, then introducing WCl5 to react with the previously adsorbed nitrogen source to form a high-quality WN thin film. This method can form a uniform WN barrier layer on oxides.
Commonly used co-reactants:
Common nitrogen sources: NH3.
Nitrogen-containing organic compounds (such as tert-butylhydrazine): produce carbon-containing W(N,C) co-deposits.
Preferred nitrogen source: N2/H2, which not only provides active nitrogen, but also reduces chlorine residue and promotes the formation of low-resistivity phase through the reduction of hydrogen.
Tungsten(V) chloride, as an emerging tungsten precursor, has shown unique advantages and diverse application potential in semiconductor thin film deposition.
Manufacturing equipment manufacturer Lam Research was among the first to develop technology for using WCl5 in tungsten filling and has applied for several patents. On the materials supplier side, Air Liquide has also focused on the purification and storage of WCl5, applying for relevant patents to ensure the high purity and stable supply of precursors.
While semiconductor device manufacturers rarely explicitly state the use of WCl5 in publicly available literature, leading companies have already incorporated this material into their R&D efforts, as evidenced by some publicly available information. For example:
Merck's Electrochemistry division explicitly states in its product introduction for high-purity WCl5 that its applications include tungsten filling of metal gate contacts for logic devices, and fluorine-free tungsten material deposition for memory (DRAM, 3D NAND).
TSMC, Intel, Samsung and other logic foundries and memory chip manufacturers may be evaluating WCl5 as a replacement for WF6 to reduce the damage of fluorine to the dielectric layer during the process.
Applied Materials also mentioned fluorine-free tungsten solutions in its technology promotion and offered a new CVD system that enables selective tungsten deposition, which may involve the selection of tungsten chloride precursors to achieve selective deposition of tungsten-filled channels on specific surfaces.
Samsung, SK Hynix, and other companies in the memory industry are more focused on using WCl5 in embedded word lines of 3D NAND and DRAM to avoid the problem of fluorine corrosion of multilayer oxide films.
According to a white paper published by Entegris, WCl₅ has demonstrated the ability to effectively replace WF6 in 3D NAND fabrication, mitigating defects such as line bending induced by fluorine-related reactions. Nevertheless, its large-scale adoption in mass production remains limited primarily due to cost factors.
As the material supply chain becomes more robust and process technologies continue to mature, WCl5 is poised to assume a more significant role in semiconductor fabrication. The current industry outlook toward WCl5 is both optimistic and prudent. Recognized as a strong candidate for the next-generation tungsten precursor, it has already gained support from leading material and equipment suppliers.
It is expected that major semiconductor manufacturers will introduce WCl₅ gradually and on a limited scale into critical process nodes, expanding its adoption following comprehensive validation in terms of cost, safety, and process stability.
As a key part of the semiconductor supply chain, a stable and high-purity supply of tungsten(Ⅴ) chloride (WCl5) is essential. We are committed to providing ultra-high-purity, electronics-grade tungsten materials and precursors for global chip manufacturers. If you are looking for a reliable WCl5 supplier, please contact us for product specifications and technical solutions.
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