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The Ground Electrode within the XR80 extraction assembly is the high-purity graphite element that defines the zero-potential reference at the exit of the ion source extraction optics. In an Applied Materials XR80-class implanter, positive ions are pulled from the arc-chamber plasma through the extraction aperture by a steep potential gradient. The ground electrode sits at the downstream end of that gradient, terminating the extraction field at earth potential and shaping the emerging ribbon or spot beam before it enters the analyser magnet and beamline. Because it stands directly in the path of an intense, high-current ion flux, it is fabricated from dense, fine-grain graphite rather than metal, a deliberate choice that minimises sputter contamination and tolerates extreme localised heating.
Within the triode (or tetrode) extraction stack, the electrodes are arranged in sequence: the plasma/source electrode at full extraction potential, one or more suppression electrodes biased negatively to reject backstreaming electrons, and the ground electrode at the end of the column. Each aperture must be aligned to a few thousandths of an inch with respect to the others, because the field they jointly produce acts as an electrostatic lens. The ground electrode’s aperture geometry and surface condition therefore have a direct, measurable effect on beam emittance, transmission and divergence.
As a graphite consumable operating in a high-vacuum, high-energy environment, this electrode is a scheduled wear item. Aperture erosion, edge rounding and surface deposition gradually degrade the extracted beam, so the part is replaced periodically as part of source and extraction preventive maintenance. ESCT Fab Support stocks this assembly (ESCT P/N ES227-0548) as an AMAT-compatible replacement to support uptime on XR80 source and beamline hardware.
The ground electrode performs several interdependent jobs at the boundary between the ion source and the analysing beamline. It is simultaneously an electrostatic, mechanical and thermal component, and its performance is judged by the quality and stability of the beam that passes through its aperture.
Graphite is selected for this electrode because no practical metal survives the combination of direct ion impingement, radiant heat from the arc chamber and the contamination constraints of front-end processing. The grade, density and machining tolerance of the graphite together determine how long the aperture holds its as-installed geometry.
The electrode uses a dense, fine-grain graphite with low ash content so that sputtered material does not introduce yield-limiting metallic species into the beam. Fine grain size yields a smoother machined aperture edge, which sputters more uniformly and preserves a clean field boundary. The material’s high sublimation temperature and excellent thermal radiation characteristics allow it to run hot without melting or outgassing markedly, while its self-lubricating, non-galling nature suits the repeated assembly and disassembly of the extraction column.
The bore diameter, edge profile and the planarity of the electrode face are machined to tight tolerances because they set the local equipotential surfaces of the extraction lens. Even modest deviation in aperture diameter or in the gap to the adjacent electrode shifts the beam perveance and focus. Consistent, controlled geometry is what allows a replacement electrode to reproduce the beam tune of the part it replaces.
Because the ground electrode shapes the beam at the very point it leaves the source, its condition propagates through the entire implant. A worn or contaminated electrode is frequently the hidden root cause of beam-quality faults that first appear far downstream.
The dominant wear mechanism is sputter erosion of the aperture by ions striking its edge. Over time the bore widens and the once-sharp edge rounds, enlarging and softening the field boundary. This shifts the focal properties of the extraction lens, drops perveance-matched beam current and gradually degrades emittance until the beam can no longer be tuned to specification.
Material evaporated and sputtered from the arc chamber and source electrode condenses on the cooler ground electrode, building up conductive or insulating films. These deposits flake to generate particles, distort the local field, and in severe cases bridge the inter-electrode gap, a leading contributor to high-voltage breakdown and persistent glitching during extraction.
Repeated thermal cycling and localised beam heating impose stress on the graphite, which can craze, crack or chip, especially at the aperture rim. Graphite is also brittle, so handling during source rebuilds can introduce edge chips or fractures. Any such damage alters the field, accelerates further erosion and, if a fragment breaks free, becomes a particle source.
The ground electrode is replaced during scheduled source and extraction maintenance, typically alongside the source electrode, suppression electrode and arc-chamber consumables. Always follow the machine’s lockout, high-voltage discharge and vacuum-vent procedures, and handle graphite parts with clean, powder-free gloves to avoid contamination and chipping.
Extraction electrodes are predictable consumables, so holding them on the shelf is a straightforward way to protect implant availability. ESCT Fab Support supplies this graphite ground electrode as an AMAT-compatible part intended to drop into existing XR80 extraction maintenance without retooling your procedures.
It sits at the downstream end of the extraction column at earth potential, terminating the extraction field and forming the final aperture of the electrostatic lens. In doing so it focuses and collimates the ion beam as it leaves the source, intercepts stray ions and protects downstream beamline surfaces.
No. This is supplied as a new, AMAT-compatible replacement part. It is not an original OEM item and is not sold as one. It is cross-referenced to OEM P/N 0020-85090 and verified to match the original in form, fit and function so it performs equivalently in the XR80 extraction assembly.
Graphite withstands direct ion bombardment and high radiant heat without melting, and its sputter products (carbon) are far less harmful to a silicon process than sputtered metals. It also outgasses little under vacuum and is dimensionally stable when hot, making it the standard material for high-flux extraction optics.
Tell-tale signs include falling extracted beam current, increasing difficulty achieving a stable tune, rising high-voltage glitch rates, degraded dose uniformity and visible aperture erosion, edge rounding or deposit build-up on inspection. Most fabs replace it on a fixed source/extraction PM interval before symptoms reach the wafer.
It is good practice. The source, suppression and ground electrodes form one optic and wear together, so refreshing the full stack during a source rebuild gives the most consistent beam tune and avoids a fresh part working against worn neighbours. Kitting the consumables together also shortens PM duration.
Handle it only with clean, powder-free gloves and avoid touching the aperture surfaces, as fingerprints and oils contaminate the vacuum and seed deposits. Because graphite is brittle, protect the aperture rim from knocks and store the part in clean packaging until installation to prevent chips and particle generation.
The graphite ground electrode (OEM P/N 0020-85090, ESCT P/N ES227-0548) is the earth-potential exit optic of the AMAT XR80 extraction assembly. It terminates the extraction field, forms the final lens aperture, and shapes the ion beam that feeds the analyser and beamline, all while resisting sputter erosion, heat and contamination. As a graphite consumable it wears predictably through aperture erosion, deposition and thermal stress, making it a core PM item whose condition directly governs beam current, stability, uniformity and yield. ESCT supplies it as an AMAT-compatible replacement, verified to form, fit and function, with a typical lead time of around 2.5 weeks to keep your implanter sources running.
Disclaimer: This part is supplied by ESCT Fab Support as a new, OEM-compatible second-source component, verified to the form, fit and function of Applied Materials part number 0020-85090. It is not an original OEM part and is not sold as one. It is not manufactured by, endorsed by, or affiliated with Applied Materials, and all manufacturer names and part numbers are quoted for identification and compatibility purposes only.
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