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Applied Materials’ selective tungsten process tackles a growing bottleneck in advanced chips: the tiny contacts that connect transistors to wiring. By growing tungsten directly from the contact’s underlying metal, rather than first adding conventional liner and nucleation layers, the process is designed to leave more room for conductive metal. Applied introduced the Endura Volta Selective W CVD system in 2020; it remains relevant, though the company is now also developing selective molybdenum for the smallest contacts.
The small connection that can limit a transistor
A transistor contact is a short vertical connection between a transistor and the first levels of a chip’s wiring. It is often called a middle-of-line contact because it sits between transistor fabrication and the interconnect stack. As that contact narrows, its resistance can become a meaningful obstacle to moving current efficiently.
Two effects compound. First, a smaller conductor has less cross-sectional area, which raises its resistance. Second, the materials used to make a conventional tungsten contact reliable do not shrink in proportion to the opening. They take up an increasingly large share of the available space. Interfaces between different materials can also add resistance, while narrow, deep openings are harder to fill without seams or voids.
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A conventional tungsten contact is more than a hole filled with tungsten. The process typically deposits a titanium or titanium-nitride liner/barrier, then a tungsten nucleation layer, followed by the bulk tungsten fill. The liner helps with adhesion, reactions and process reliability; the nucleation layer helps tungsten start growing on the liner. They are useful manufacturing layers, but they are not as effective conductors as bulk tungsten and they displace it.
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Applied’s 2020 explanation gave an illustrative example: for a contact around 20 nanometers in diameter associated with a 7-nm process generation, it estimated that the liner/barrier and nucleation layers could occupy about 75% of the contact volume, leaving roughly 25% for tungsten. That is Applied’s estimate for an example, not a universal measurement for every 7-nm process. Node names such as 7 nm, 5 nm and 3 nm refer to process generations, not standardized contact dimensions. Applied’s technical explanation describes the example and its limits.
What selective tungsten changes
Applied’s Endura Volta Selective W CVD is designed to skip the conventional liner/barrier and tungsten nucleation layers in the targeted contact structure. It uses integrated surface treatments to condition the exposed metal and dielectric differently, so tungsten is encouraged to nucleate on the desired conductive surface rather than coat everything indiscriminately. The tungsten then grows upward from the bottom of the contact.
- Prepare the surfaces: Surface treatments clean and condition the underlying metal and surrounding dielectric.
- Promote selective nucleation: The chemistry is tuned so tungsten starts on the intended conductive surface, not on dielectric areas.
- Grow from the bottom: Tungsten fills upward, rather than relying on sidewall growth that can close an opening around a seam or trap a void.
- Preserve the interface: Treatment and deposition steps take place in an integrated high-vacuum environment.
“Selective” is a process result, not an unconditional property of tungsten. If the surface preparation or chemistry is out of its process window, tungsten may fail to nucleate uniformly on the metal or may deposit where it is not wanted. The former can leave a high-resistance or incomplete contact; the latter can create unwanted metal, leakage paths or shorts.
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1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesApplied has likened the approach to “atomic-scale 3D printing.” That is an analogy for controlling where material grows and how it fills a three-dimensional opening, not a literal description of the equipment. The more important point is that the tool combines surface engineering and deposition: it is not simply a tungsten CVD chamber operating faster.
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Why the vacuum-integrated platform matters
Selective growth depends on carefully prepared surfaces. Exposure to oxygen, moisture or other contaminants between treatment and deposition could change those surfaces and undermine the intended chemistry or interface. Applied therefore combines multiple treatment and deposition steps on the Endura platform under high vacuum. Keeping the wafer in that controlled environment is part of the process solution, not a convenience added around it. See the Endura Volta product description.
The approach is intended to avoid center seams, voids and delamination while increasing the volume available to conducting tungsten. Those are design aims, not guarantees for every wafer: defectivity and yield still depend on the contact’s etch profile, cleaning, pattern density, underlying material and downstream integration.
What Applied claimed—and what is known publicly
Applied announced the technology on July 20, 2020, positioning it as a way to support continued transistor and contact scaling through 5 nm, 3 nm and smaller process generations. That is a company roadmap claim; it does not establish that every process at those generations uses the tool or receives the same benefit. Lower contact resistance can help transistor power and performance, but it does not translate by itself into a fixed improvement in whole-chip speed or energy use.
Applied’s current technical material says selective tungsten can reduce contact resistance by about 40% compared with conventional tungsten. This is a vendor-reported comparison; the public material cited here does not provide the full test structure, process node or measurement conditions needed to treat it as a universal result. Likewise, claims about maximizing conducting-metal volume should not be read as proof that every finished contact is literally 100% tungsten.
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At launch, Applied said multiple leading customers were using the technology. EE Times reported that Applied said more than 20 systems had been sold by then. The customers were not named, and no independent, customer-level resistance or yield data were published in that report. It is a historical launch-era report, not a current installed-base figure. Applied’s announcement and the EE Times account provide the original context.
Tungsten versus cobalt: the contact level matters
Cobalt is a genuine alternative, not a material that selective tungsten has simply displaced. At very small dimensions, cobalt can support a thinner liner and may offer favorable gapfill and resistance in some applications. The choice depends on the underlying material, contact geometry, thermal budget, reliability needs and process maturity.
In its 2020 comparison, Applied characterized liner-based cobalt as a more forgiving option for some first-level contacts to silicon, while selective tungsten could suit contacts to an existing metal layer. That distinction is application-specific, not a general rule that one metal is always better. A process that works well on a metal surface may not be the right choice for a silicon source/drain contact, and vice versa. EE Times’ cobalt discussion covers this trade-off.
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The 2026 context: molybdenum is entering the picture
Applied still lists selective tungsten among its advanced contact technologies, but its newer materials work points to another option for the smallest structures. The company reports that selective molybdenum achieves about 15% lower contact resistance than selective tungsten in advanced test structures. That comparison is also vendor-reported, and it does not establish that molybdenum has replaced tungsten in production or is preferable for every contact.
The development also underscores that low resistance is only one part of the challenge. Surface selectivity, uniform fill, overfill or underfill, protrusion, planarization and metrology all have to work together. Applied’s process-development discussion and molybdenum overview describe the company’s current direction. For now, tungsten is best understood as a way to buy scaling headroom by removing resistive layers, while molybdenum is a developing complement or successor for especially demanding contacts.
Where selective tungsten makes sense
The approach is most attractive when the contact is small enough that liner and nucleation layers consume substantial volume, the exposed metal is compatible with direct tungsten growth, and the fab can maintain the surface-treatment and vacuum sequence. It may be less attractive where a liner provides valuable process tolerance, the substrate is not compatible, or existing contact resistance already meets the product target. This is an enterprise fab process requiring integration and qualification, not a consumer technology or a drop-in upgrade for chip-design teams.
Applied’s 2020 launch story is therefore still useful, but its significance is specific: selective tungsten addresses the geometry and process penalties of conventional tungsten contacts. It does not prove a universal winner over cobalt, guarantee whole-chip performance gains, or settle which metal will serve the smallest future contacts.
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