EBIC Amplifier

From picoamps to a live video signal#

The EBIC amplifier is a low-noise current-to-voltage converter that turns the picoamp-scale currents an electron beam induces in a sample into a video signal the microscope can display. Gain switches from 10⁴ to 10¹² V/A, the measurement floor sits at 100 fA, and the amplifier tracks signals up to 10 MHz of bandwidth — enough headroom to follow fast beam-induced transients as well as slow, quiet defect currents.

One amplifier covers five related nanoprobing techniques — EBIC, EBAC, RCI, EBIRCH and EBIV — reached by combining AC or DC amplification, image inversion and an applied sample bias, without swapping hardware. EBIC separates electron-hole pairs at a p-n junction; EBAC and RCI instead read current diffusing into metal wires contacted by the probe tips, distinguishing low- and high-ohmic connections; EBIRCH tracks a resistance change under beam injection; EBIV maps voltage drops down to a few ohms of difference. Because all five read beam-induced current rather than surface topography, a fault can be localized on 3 nm-class devices without removing the passivation layer.

The video output runs at 1 V into 50 Ω and feeds straight into the microscope’s video input, so the current map overlays the secondary-electron image live — the operator watches the defect site light up as the beam scans across it.

From wafer-scale opens to 5 nm FinFETs#

Selectable input current compensation and a large offset range keep the signal centred as gain climbs into the 10¹² V/A range, where a single stray electron matters. On a via chain of 180 elements, EBIRCH isolates a single low-ohmic failure among hundreds of nominally identical structures; on a 14 nm device, RCI separates open from closed current regression through a 1 MΩ resistance structure. The amplifier’s job throughout is the same — hold the noise floor below 100 fA while the gain does the work of making a femtoamp visible.