Mercury probe
Encyclopedia
The Mercury Probe is an electrical probing device to make rapid, non-destructive contact to a sample for electrical characterization. Its primary application is semiconductor
measurements where time-consuming metallizations or photolithographic processing are required to make contact to a sample. These processing steps usually take hours and have to be avoided where possible to reduce device processing times.
One of the first successful Mercury Probe applications was the characterization of epitaxial layers grown on silicon
[1]. It is critical to device performance to monitor the doping
level and thickness of an epitaxial layer. Prior to the Mercury Probe, a sample had to undergo a metallization process, which could take hours. A Mercury Probe connected to capacitance-voltage doping profile instrumentation could measure an epitaxial layer as soon as it came out of the epitaxial reactor. The Mercury Probe formed a Schottky barrier
of well-defined area that could be measured as easily as a conventional metallized contact.
Another Mercury Probe application popular for it speed is oxide characterization [2]. The Mercury Probe forms a gate
contact and enables measurement of the capacitance-voltage or current-voltage parameters of the mercury-oxide-semiconductor structure. Using this device, material parameters such as permittivity
, doping, oxide charge, and dielectric strength may be evaluated.
A Mercury Probe with concentric dot and ring contacts as well as a back contact extends Mercury Probe applications to SOI
structures, where a pseudo-MOSFET device is formed [3]. This Hg-FET can be used to study mobility, interface trap density, and transconductance
.
The Mercury Probe applies mercury contacts of well-defined areas to a flat sample. The nature of the mercury-sample contacts and the instrumentation connected to the Mercury Probe define the application. If the mercury-sample contact is ohmic (non-rectifying) then current-voltage instrumentation can be used to measure resistance
, leakage currents, or current-voltage characteristics. Resistance can be measured on bulk samples or on thin films. The thin films can be composed of any material that does not react with mercury. Metals, semiconductors, oxides, and chemical coatings have all been measured successfully [4].
The same mercury-sample structures can be measured with capacitance-voltage instrumentation to monitor permittivity and thickness of dielectric materials. These measurements are a convenient gauge for development of novel dielectrics of both low-k and high-k types.
If the mercury-sample contact is rectifying then a diode has formed and offers other measurement possibilities. Current-voltage measurements of the diode can reveal properties of the semiconductor such as breakdown voltage and lifetime. Capacitance-voltage measurements allow computation of the semiconductor doping level and uniformity. These measurements are successfully made on many materials including SiC
, GaAs
, 2DEG
, GaN
, InP
, CdS
, and InSb.
The ability of the Mercury Probe to form rapid, non-destructive, contacts to planar materials makes it a versatile tool for investigation of many parameters of a wide range of conducting, insulating and semiconductor materials.
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
measurements where time-consuming metallizations or photolithographic processing are required to make contact to a sample. These processing steps usually take hours and have to be avoided where possible to reduce device processing times.
One of the first successful Mercury Probe applications was the characterization of epitaxial layers grown on silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
[1]. It is critical to device performance to monitor the doping
Doping (semiconductor)
In semiconductor production, doping intentionally introduces impurities into an extremely pure semiconductor for the purpose of modulating its electrical properties. The impurities are dependent upon the type of semiconductor. Lightly and moderately doped semiconductors are referred to as extrinsic...
level and thickness of an epitaxial layer. Prior to the Mercury Probe, a sample had to undergo a metallization process, which could take hours. A Mercury Probe connected to capacitance-voltage doping profile instrumentation could measure an epitaxial layer as soon as it came out of the epitaxial reactor. The Mercury Probe formed a Schottky barrier
Schottky barrier
A Schottky barrier, named after Walter H. Schottky, is a potential barrier formed at a metal–semiconductor junction which has rectifying characteristics, suitable for use as a diode...
of well-defined area that could be measured as easily as a conventional metallized contact.
Another Mercury Probe application popular for it speed is oxide characterization [2]. The Mercury Probe forms a gate
Gate
A gate is a point of entry to a space enclosed by walls, or a moderately sized opening in a fence. Gates may prevent or control entry or exit, or they may be merely decorative. Other terms for gate include yett and port...
contact and enables measurement of the capacitance-voltage or current-voltage parameters of the mercury-oxide-semiconductor structure. Using this device, material parameters such as permittivity
Permittivity
In electromagnetism, absolute permittivity is the measure of the resistance that is encountered when forming an electric field in a medium. In other words, permittivity is a measure of how an electric field affects, and is affected by, a dielectric medium. The permittivity of a medium describes how...
, doping, oxide charge, and dielectric strength may be evaluated.
A Mercury Probe with concentric dot and ring contacts as well as a back contact extends Mercury Probe applications to SOI
SOI
SOI might be an acronym or abbreviation for:Technology:* Silicon on Insulator* Signal operating instructions* Service Oriented Infrastructure* Start of injectionScience:* Southern Oscillation Index...
structures, where a pseudo-MOSFET device is formed [3]. This Hg-FET can be used to study mobility, interface trap density, and transconductance
Transconductance
Transconductance, also known as mutual conductance, is a property of certain electronic components. Conductance is the reciprocal of resistance; transconductance, meanwhile, is the ratio of the current change at the output port to the voltage change at the input port. It is written as gm...
.
The Mercury Probe applies mercury contacts of well-defined areas to a flat sample. The nature of the mercury-sample contacts and the instrumentation connected to the Mercury Probe define the application. If the mercury-sample contact is ohmic (non-rectifying) then current-voltage instrumentation can be used to measure resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
, leakage currents, or current-voltage characteristics. Resistance can be measured on bulk samples or on thin films. The thin films can be composed of any material that does not react with mercury. Metals, semiconductors, oxides, and chemical coatings have all been measured successfully [4].
The same mercury-sample structures can be measured with capacitance-voltage instrumentation to monitor permittivity and thickness of dielectric materials. These measurements are a convenient gauge for development of novel dielectrics of both low-k and high-k types.
If the mercury-sample contact is rectifying then a diode has formed and offers other measurement possibilities. Current-voltage measurements of the diode can reveal properties of the semiconductor such as breakdown voltage and lifetime. Capacitance-voltage measurements allow computation of the semiconductor doping level and uniformity. These measurements are successfully made on many materials including SiC
SIC
Sic is a Latin word that means "thus" or, in writing, "it was thus in the source material".Sic may also refer to:* Sic, Cluj, a commune in Romania* SiC, Silicon carbide, a semiconducting material, also used to make metalworking tools from...
, GaAs
Gaas
Gaas is a commune in the Landes department in Aquitaine in south-western France....
, 2DEG
2DEG
A two-dimensional electron gas is a gas of electrons free to move in two dimensions, but tightly confined in the third. This tight confinement leads to quantized energy levels for motion in that direction, which can then be ignored for most problems. Thus the electrons appear to be a 2D sheet...
, GaN
Gan
Gan may refer to:-Computing and telecommunications:*.gan, the file extension for documents created by GanttProject*Generic Access Network formerly known as Unlicensed Mobile Access *Global Area Network- Mythology :...
, InP
INP
INP may stand for:*INP , a Korean chemical company*INP , an early database system developed at the University of California, Berkeley*Integrated National Police, a forerunner of the Philippine National Police...
, CdS
Cadmium sulfide
Cadmium sulfide is the inorganic compound with the formula CdS. Cadmium sulfide is a yellow solid. It occurs in nature with two different crystal structures as the rare minerals greenockite and hawleyite, but is more prevalent as an impurity substituent in the similarly structured zinc ores...
, and InSb.
The ability of the Mercury Probe to form rapid, non-destructive, contacts to planar materials makes it a versatile tool for investigation of many parameters of a wide range of conducting, insulating and semiconductor materials.