Electron-beam-induced current (EBIC) is a semiconductor analysis technique performed in a

scanning electron microscope A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that ...

(SEM) or scanning transmission electron microscope (STEM). It is most commonly used to identify buried junctions or defects in semiconductors, or to examine minority carrier properties. EBIC is similar to

cathodoluminescence Cathodoluminescence is an optical and electromagnetic phenomenon in which electrons impacting on a luminescent material such as a phosphor, cause the emission of photons which may have wavelengths in the visible spectrum. A familiar example i ...

in that it depends on the creation of

electron–hole pair In solid-state physics of semiconductors, carrier generation and carrier recombination are processes by which mobile charge carriers (electrons and electron holes) are created and eliminated. Carrier generation and recombination processes are fund ...

s in the semiconductor sample by the microscope's electron beam. This technique is used in semiconductor

failure analysis Failure analysis is the process of collecting and analyzing data to determine the cause of a failure, often with the goal of determining corrective actions or liability. According to Bloch and Geitner, ”machinery failures reveal a reaction chain ...

and

solid-state physics Solid-state physics is the study of rigid matter, or solids, through methods such as solid-state chemistry, quantum mechanics, crystallography, electromagnetism, and metallurgy. It is the largest branch of condensed matter physics. Solid-state phy ...

Physics of the technique

If the semiconductor sample contains an internal

electric field An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) descri ...

, as will be present in the

depletion region In semiconductor physics, the depletion region, also called depletion layer, depletion zone, junction region, space charge region, or space charge layer, is an insulating region within a conductive, doped semiconductor material where the mobil ...

at a p-n junction or Schottky junction, the electron–hole pairs will be separated by drift due to the electric field. If the p- and n-sides (or semiconductor and Schottky contact, in the case of a Schottky device) are connected through a picoammeter, a current will flow. EBIC is best understood by analogy: in a

solar cell A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

, photons of light fall on the entire cell, thus delivering energy and creating electron hole pairs, and cause a current to flow. In EBIC, energetic electrons take the role of the photons, causing the EBIC current to flow. However, because the electron beam of an SEM or STEM is very small, it is scanned across the sample and variations in the induced EBIC are used to map the electronic activity of the sample. By using the signal from the picoammeter as the imaging signal, an EBIC image is formed on the screen of the SEM or STEM. When a semiconductor device is imaged in cross-section, the depletion region will show bright EBIC contrast. The shape of the contrast can be treated mathematically to determine the minority carrier properties of the semiconductor, such as diffusion length and surface recombination velocity. In plain-view, areas with good crystal quality will show bright contrast, and areas containing defects will show dark EBIC contrast. As such, EBIC is a semiconductor analysis technique useful for evaluating minority carrier properties and defect populations. EBIC can be used to probe subsurface hetero-junctions of nanowires and the properties of minority carrier

EBIC has also been extended to the study of local defects in insulators. For example, W.S. Lau ( Lau Wai Shing) developed "true oxide electron beam induced current" in the 1990s. Thus, besides p-n junction or Schottky junction, EBIC can also be applied to MOS diodes. Local defects in

semiconductor A semiconductor is a material with electrical conductivity between that of a conductor and an insulator. Its conductivity can be modified by adding impurities (" doping") to its crystal structure. When two regions with different doping level ...

and local defects in the insulator could be distinguished. There exists a kind of defect which originates in the

silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...

substrate and extends into the insulator on top of the

substrate. (Please see references below.) Recently, EBIC has been applied to high-k dielectric used in advanced

CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss ", , ) is a type of MOSFET, metal–oxide–semiconductor field-effect transistor (MOSFET) semiconductor device fabrication, fabrication process that uses complementary an ...

technology.

SEEBIC

A related STEM EBIC technique, called secondary electron emission EBIC, or SEEBIC, measures the positive current produced by emission of

secondary electrons Secondary electrons are electrons generated as ionization products. They are called 'secondary' because they are generated by other radiation In physics, radiation is the emission or transmission of energy in the form of waves or particle ...

from a sampl

SEEBIC was first demonstrated in 2018, likely due to its much smaller signal compared to the standard EBIC mode (electron-hole pair separation). The smaller interaction volume of secondary electron generation compared to electron-hole pair production makes SEEBIC accessible at much higher spatial resolutio

SEEBIC signal is sensitive to a number of electronic properties, and is most notably the only high-resolution

electrical conductivity Electrical resistivity (also called volume resistivity or specific electrical resistance) is a fundamental specific property of a material that measures its electrical resistance or how strongly it resists electric current. A low resistivity in ...

mapping technique for the transmission electron microscop

Quantitative SEM EBIC

Most EBIC images acquired in the SEM are qualitative, only showing EBIC signal as image display contrast. Use of an external scan control generator on the SEM and a dedicated data acquisition system allow for sub-picoamp measurements and can give quantitative results. Some systems are commercially available that do this, and provide the ability to provide functional imaging by biasing and applying gate voltages to semiconductor devices.

References

* (Review Article) * * * * * * * (Note: EBIC was performed on advanced high-k gate stack even though it is not obvious by reading the title of the paper.) * {{Electron microscopy Electron beam Scientific techniques Semiconductor device fabrication Semiconductor analysis