# CVD and PVD: two ways to supply a film

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Revision: 2026-10-07
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Fabrication / Repeated operations · Atlas v1.3.0

# CVD and PVD: two ways to supply a film

Contrasts chemical surface growth with physical material transport.

[Explore in Atlas](https://semiaifoundry.com/ai-atlas/#cvd-pvd-film-transport)Nanometer films on a wafer; thickness exaggerated

Learning objectiveExplain how transport and reaction produce different deposited geometries.

## The mechanism

Deposition 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.

1.  Choose the intended film function and identify the surfaces that must receive material.
2.  For CVD, deliver reactants and enable the required surface chemistry; for PVD, generate a material flux.
3.  Account for transport and reaction along the feature rather than assuming uniform exposure.
4.  Grow to the required geometry while tracking stress, impurities and possible closure of an opening.
5.  Measure local coverage and interface performance, not only a blanket-wafer thickness.

## Science and assumptions

### Coverage ratio

$$
C_{\mathrm{bottom}}=\frac{t_{\mathrm{bottom}}}{t_{\mathrm{top}}}
$$

Bottom coverage is bottom-film thickness divided by top-reference thickness for the same feature.

Symbols and units

C\_bottom

Bottom-to-top thickness coverage ratio

dimensionless

t\_bottom

Film thickness at the selected feature bottom

nm

t\_top

Film thickness at its defined top reference

nm

Both thicknesses use the same unit and refer to the same defined feature; the ratio is dimensionless.

Assumptions A local geometric descriptor. It does not capture adhesion, composition, stress or complete three-dimensional void topology.

## Engineering example

Synthetic 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.

## Distinctions and tradeoffs

Equal blanket thickness does not establish equal sidewall coverage or void-free filling.

A method with high deposition throughput may struggle with extreme geometry or a thermal budget; another may require slower cycles or additional preparation.

Contacts, barriers, dielectrics and conductors must cover three-dimensional structures without introducing weak electrical or mechanical interfaces.

## Specifications and interfaces

Thickness

Length, measured at named locations

Top, sidewall and bottom coverage may differ.

Conformality

Local thickness / reference thickness

A defined geometric ratio, not a guarantee of electrical continuity.

### Interfaces

Surface and material supply Input

Precursors or physically transported atoms

Deposited film Output

Geometry, composition, stress and interface adhesion

## Check your understanding

### A trench opening closes before its interior fills. What does this indicate?

1.  The local growth profile matters beyond average deposition rate
2.  The film is necessarily electrically perfect
3.  All deposition methods are self-limiting

Answer and reasoning

The local growth profile matters beyond average deposition rate

Material can accumulate near the opening and isolate a cavity; changing average thickness alone does not describe this geometry.

## Evidence and scope

Cross-sections are representative mechanisms. Actual coverage depends on process, chemistry, pressure, temperature, geometry and surface preparation.

Use the manufacturing investigation to trace compatible inputs, assembly and operating constraints; no current standalone calculator models this lesson’s full mechanism.

## Sources

-   [Lam Research — Our Processes](https://www.lamresearch.com/products/our-processes/)
-   [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/)

[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)

## Continue exploring

### Foundations

-   [A process chamber as a controlled reactor](https://semiaifoundry.com/learn/atlas/process-chamber-control/)

### Related lessons

-   [ALD and self-limiting surface reactions](https://semiaifoundry.com/learn/atlas/ald-self-limiting-growth/)
-   [BEOL layers, damascene and vias](https://semiaifoundry.com/learn/atlas/beol-damascene-vias/)