Physical vapor deposition (PVD) forms a film by transferring material from a condensed source to a wafer through a low-pressure environment. Sputtering is one PVD method: energetic ions strike a solid target and eject atoms by momentum transfer; evaporation is another method with a different source mechanism . This article explains sputtering in particular. Film composition, adhesion and coverage depend on the source, transport and wafer conditions; the method alone guarantees none of them.
Metal-Film Context for PVD
The 7nm FinFET flow overview contains gate-metal films, metal fill and interconnect barrier/seed deposition. The cross-sections below show where these films sit in the stack. Their step names do not identify sputtering, and the tungsten fill must not be described as a sputter fill. Use the overview for integration context, then ask which deposition method the source actually specifies before assigning PVD to a step. For the wider PVD family, see the separate PVD overview.
7nm flow cross-sections show metal-film locations only. Step labels do not establish sputtering, and the tungsten fill method is unspecified.
Process map
7nm FinFET
Locate gate-metal and interconnect film roles. Their labels and cross-sections do not establish sputtering or the metal-fill method.
Physics & Mechanism
PVD includes sputtering and evaporation. Sputtering uses ion momentum to eject target atoms; evaporation supplies energy to turn source material into vapor. In either case the vapor travels to a surface and forms a film, while source, transport and surface conditions determine what arrives . These methods cannot be inferred from a film name alone.
In sputtering, ions from a discharge reach a target and transfer momentum to its near-surface atoms. Some atoms leave the target, pass through gas or vacuum and condense on the wafer. The flux reaching a surface depends on target material, ion bombardment, scattering and the geometry between source and wafer. A magnetron can confine electrons near the target and sustain a discharge, but it does not make every sputtered film equally conformal or pure.
The arriving flux is often directional. A raised edge may intercept atoms before they reach the bottom or sidewall of a narrow feature. Scattering or ionization can change that distribution, but coverage must be evaluated for the actual geometry. Alloy composition need not reproduce the target exactly, because constituent yields, transport and resputtering can differ. In reactive sputtering, a supplied gas participates in forming a compound film; the target surface may change state and alter the deposition response.
Process Principles
- Identify the actual method: a label such as “metal deposition” or “barrier/seed deposition” establishes a film role, not that it was sputtered.
- Track source and transport: target composition, ejection and scattering jointly influence the arriving flux .
- Check coverage and interface: directionality can leave recessed surfaces undercoated; cleanliness and nucleation influence the resulting film.
- Separate liner from fill: a thin PVD barrier or seed can prepare a feature for a different, later fill method. The two steps should not be conflated.
Challenges & Failure Modes
Nonuniform arrival can thin a liner at feature bottoms, while re-entrant coverage can narrow an opening. Reactive target-state changes can shift growth rate or composition. Stress, contamination and particles are possible concerns, but their direction and scale depend on the process and film. None can be inferred from a cross-section without process evidence.
From Principle to Production Flow
Use the 7nm overview to locate metal films and their order relative to fill and planarization. The overview is an integration map; it does not certify a PVD recipe. Compare seed layers and diffusion barriers for film functions, then CVD for a distinct chemical growth mechanism.
Technology Node Evolution
As features become narrower, directional coverage becomes harder to use for complete fill. PVD can still serve some thin metal, barrier or seed roles, while other methods may handle conformal coating or bulk fill. The choice follows the required material and geometry rather than a node-wide rule.
Related Processes
PVD as a family includes sputtering and evaporation. Tungsten describes a possible fill material, not evidence that the flow's tungsten was sputtered. Annealing can change film microstructure after deposition.
Future Outlook
The central integration question remains whether the arriving flux builds the required film across the real surface while preserving the interface and neighboring layers. A named material in a flow is only the starting point for that analysis.
References
Silicon VLSI Technology - Full
James D. Plummer, Michael D. Deal, Peter B. Griffin
Silicon VLSI Technology · ISBN 978-0130850379