Ion beam etching Scia Systems Coat 200

Marek Eliáš

Ion beam etching (IBE) removes material from the etch target by bombardment with directed and precisely controlled ion energies. IBE is also referred to as "ion beam milling."

The IBE source generates plasma from a noble gas, typically argon. A set of electrically biased grids establish the ion beam energy and angular divergence of ions within the beam. The ion beam strikes the substrate, removing material by physical sputtering.

Ion beam etching provides directional flexibility that is not available in other plasma processes. While the etch rate with IBE is typically lower than for reactive ion etching (RIE), IBE offers high precision (high anisotropism) for applications that demand exacting profile control. Also, ion beam etching can be used to remove materials where RIE may not be successful. Ion beam can etch alloys and composite materials that are not compatible with RIE.

A tilting and rotating substrate stage allows ion angle of incidence to be altered. This affects sputtering yield and resulting topography. Tilting and rotating the substrate during etching can substantially improve etch profiles and avoid material redeposition.

Endpoint control is available with SIMS (secondary ion mass spectroscopy) to monitor sputtered material species, allowing etching to be stopped at specific layers.

Ion-beam etching has many applications, including nano-machining of magnetic transducers, MEMS devices, and trimming of surface acoustic wave (SAW) and bulk acoustic wave (BAW) filters. A newer application is fabricating high-performance non-volatile memory, specifically "spin transfer torque" MRAM (magnetoresistive random-access memory).

circular microwave broad ion beam source at frequency 2,54 GHz
ion energy 50–2 000 keV
sample size up to 6” wafer
sample rotation 5–20 rpm
He backside cooling
endpoint detection system SIMS HAL IMP 301/3F with accuracy 1 nm
Ar+ sputtering
reactive ion beam etchingCHF3, O2, SF6

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