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  "title": "CVD and PVD: two ways to supply a film",
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  "description": "Contrasts chemical surface growth with physical material transport.",
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  "revisionDate": "2026-10-07",
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  "topic": "Fabrication / Repeated operations",
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      "title": "A trench opening closes before its interior fills. What does this indicate?",
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      "title": "Explore in Atlas",
      "url": "https://semiaifoundry.com/ai-atlas/#cvd-pvd-film-transport"
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    {
      "title": "Lam Research — Our Processes",
      "url": "https://www.lamresearch.com/products/our-processes/"
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      "title": "MIT 6.152J — Micro/Nano Processing Technology lecture notes",
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      "title": "A process chamber as a controlled reactor",
      "url": "https://semiaifoundry.com/learn/atlas/process-chamber-control/"
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    {
      "title": "ALD and self-limiting surface reactions",
      "url": "https://semiaifoundry.com/learn/atlas/ald-self-limiting-growth/"
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  "content": "Fabrication / Repeated operations · Atlas v1.3.0\n\n# CVD and PVD: two ways to supply a film\n\nContrasts chemical surface growth with physical material transport.\n\n[Explore in Atlas](https://semiaifoundry.com/ai-atlas/#cvd-pvd-film-transport)Nanometer films on a wafer; thickness exaggerated\n\nLearning objectiveExplain how transport and reaction produce different deposited geometries.\n\n## The mechanism\n\nDeposition adds material, but different methods deliver it differently. Chemical vapor deposition supplies molecules that react or decompose to form a film. Physical vapor deposition transports material from a source, for example through sputtering or evaporation, to a receiving surface. Geometry matters: a surface that receives little incoming flux can coat differently from an exposed top face. Chemistry, surface reactions and transport can also produce gradients or voids in difficult features. The lesson compares the same trench after representative CVD and directional PVD steps, keeping film thickness, conformity, adhesion and composition as separate outputs rather than labeling one method universally better.\n\n1.  Choose the intended film function and identify the surfaces that must receive material.\n2.  For CVD, deliver reactants and enable the required surface chemistry; for PVD, generate a material flux.\n3.  Account for transport and reaction along the feature rather than assuming uniform exposure.\n4.  Grow to the required geometry while tracking stress, impurities and possible closure of an opening.\n5.  Measure local coverage and interface performance, not only a blanket-wafer thickness.\n\n## Science and assumptions\n\n### Coverage ratio\n\n$$\nC_{\\mathrm{bottom}}=\\frac{t_{\\mathrm{bottom}}}{t_{\\mathrm{top}}}\n$$\n\nBottom coverage is bottom-film thickness divided by top-reference thickness for the same feature.\n\nSymbols and units\n\nC\\_bottom\n\nBottom-to-top thickness coverage ratio\n\ndimensionless\n\nt\\_bottom\n\nFilm thickness at the selected feature bottom\n\nnm\n\nt\\_top\n\nFilm thickness at its defined top reference\n\nnm\n\nBoth thicknesses use the same unit and refer to the same defined feature; the ratio is dimensionless.\n\nAssumptions A local geometric descriptor. It does not capture adhesion, composition, stress or complete three-dimensional void topology.\n\n## Engineering example\n\nSynthetic cross-section: 10 nm on a trench top and 3 nm at its bottom gives 0.30 bottom coverage. A blanket thickness measurement reporting 10 nm would miss the weak bottom coverage.\n\n## Distinctions and tradeoffs\n\nEqual blanket thickness does not establish equal sidewall coverage or void-free filling.\n\nA method with high deposition throughput may struggle with extreme geometry or a thermal budget; another may require slower cycles or additional preparation.\n\nContacts, barriers, dielectrics and conductors must cover three-dimensional structures without introducing weak electrical or mechanical interfaces.\n\n## Specifications and interfaces\n\nThickness\n\nLength, measured at named locations\n\nTop, sidewall and bottom coverage may differ.\n\nConformality\n\nLocal thickness / reference thickness\n\nA defined geometric ratio, not a guarantee of electrical continuity.\n\n### Interfaces\n\nSurface and material supply Input\n\nPrecursors or physically transported atoms\n\nDeposited film Output\n\nGeometry, composition, stress and interface adhesion\n\n## Check your understanding\n\n### A trench opening closes before its interior fills. What does this indicate?\n\n1.  The local growth profile matters beyond average deposition rate\n2.  The film is necessarily electrically perfect\n3.  All deposition methods are self-limiting\n\nAnswer and reasoning\n\nThe local growth profile matters beyond average deposition rate\n\nMaterial can accumulate near the opening and isolate a cavity; changing average thickness alone does not describe this geometry.\n\n## Evidence and scope\n\nCross-sections are representative mechanisms. Actual coverage depends on process, chemistry, pressure, temperature, geometry and surface preparation.\n\nUse the manufacturing investigation to trace compatible inputs, assembly and operating constraints; no current standalone calculator models this lesson’s full mechanism.\n\n## Sources\n\n-   [Lam Research — Our Processes](https://www.lamresearch.com/products/our-processes/)\n-   [MIT 6.152J — Micro/Nano Processing Technology lecture notes](https://ocw.mit.edu/courses/6-152j-micro-nano-processing-technology-fall-2005/pages/lecture-notes/)\n\n[Published lesson data](https://semiaifoundry.com/ai-atlas/lesson-data/cvd-pvd-film-transport-c379b4502b875a78.json) · [Atlas releases and licensing](https://semiaifoundry.com/ai-atlas/licenses.html)\n\n## Continue exploring\n\n### Foundations\n\n-   [A process chamber as a controlled reactor](https://semiaifoundry.com/learn/atlas/process-chamber-control/)\n\n### Related lessons\n\n-   [ALD and self-limiting surface reactions](https://semiaifoundry.com/learn/atlas/ald-self-limiting-growth/)\n-   [BEOL layers, damascene and vias](https://semiaifoundry.com/learn/atlas/beol-damascene-vias/)"
}