Fab desk

Etch and deposition: adding and removing atoms

Published 3 August 2026. Facts verified to 27 July 2026 unless dated otherwise.

Lithography decides where the pattern goes. Deposition and etch do the actual building, and between them they consume most of a fab's exotic chemistry.

Deposition: growing films atoms thick

Chips are stacks of extremely thin films: conductors, insulators and semiconducting layers. Three families of tools put them there. Chemical vapour deposition flows reactive gases over a heated wafer so a solid film forms on its surface. Physical vapour deposition, commonly sputtering, knocks atoms off a target so they land on the wafer. Atomic layer deposition builds the film one atomic layer at a time through self-limiting surface reactions, trading throughput for extraordinary thickness control and conformality.

The choice among them is dictated by the material, the required thickness uniformity, and the shape of the surface being coated. Deep, narrow features need conformal coverage that only the slower, more controlled methods can provide, which is one reason process complexity and cost rise as geometries shrink.

Etch: cutting the pattern in

Etching removes material from the areas the resist leaves exposed. Wet etching uses liquid chemistry and tends to cut in all directions at once. Plasma or dry etching uses energised reactive gas and can be made strongly directional, cutting downward far faster than sideways. That directionality, anisotropy, is what allows tall narrow structures to be formed without undercutting the pattern.

The second critical property is selectivity: the etch must attack the target material much faster than the mask above it or the layer beneath it. Achieving both anisotropy and selectivity, repeatably, across a whole wafer and across thousands of wafers, is the core difficulty of etch engineering, and it is why process recipes are guarded assets and why a technology partner's recipe library is worth so much to a first-time fab operator.

Why these tools drive the gas supply chain

Deposition and etch consume a long list of specialty gases and precursor chemicals, many of them hazardous, several of them requiring on-site abatement before exhaust. That demand is precisely why an industrial gas supplier siting a specialty gas facility near a fab is such a strong signal: it is a capital commitment made against expected consumption. The reported gas hub at Dholera REPORTED is filed on our INOX company page, and the wider pattern is argued in the supply-chain briefing.

What this means for a region's industrial base

Every one of these tool families implies a local ecosystem: gas handling, chemical logistics, abatement systems, spares, calibration, and technicians who can maintain vacuum and plasma systems. Those are the businesses that actually populate a fab region over a decade, and they are the realistic entry point for domestic suppliers, as our supplier guide sets out.