Transistor aging (sometimes called silicon aging) is the process of

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...

transistors upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...

developing flaws over time as they are used, degrading performance and reliability, and eventually failing altogether. Despite the name, similar mechanisms may affect transistors made of any kind of semiconductor.

Manufacturers Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a ra ...

compensate for this (as well as manufacturing defects) by running chips at slower speeds than they are initially capable of.

Causes

The main causes of transistor aging in

MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...

s are ''electromigration'' and ''charge trapping''.

Electromigration Electromigration is the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect is important in applications where high direc ...

is the movement of

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

s caused by

momentum In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass ...

from the transfer of

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary partic ...

s in the conductor. This results in degradation of the material, causing intermittent glitches that are very difficult to diagnose, and eventual failure. Charge trapping is related to time-dependent gate oxide breakdown, and manifests as an increase in resistance and

threshold voltage The threshold voltage, commonly abbreviated as Vth or VGS(th), of a field-effect transistor (FET) is the minimum gate-to-source voltage (VGS) that is needed to create a conducting path between the source and drain terminals. It is an important ...

(the voltage needed for the transistor to conduct), and a decrease in drain current. This degrades the chip performance over time, until ultimately the thresholds collapse. Charge trapping occurs in several ways: *

Hot carrier injection Hot carrier injection (HCI) is a phenomenon in solid-state electronic devices where an electron or a “hole” gains sufficient kinetic energy to overcome a potential barrier necessary to break an interface state. The term "hot" refers to the ...

(HCI) is where electrons gain enough energy to leak into the oxide, becoming trapped there and possibly damaging it. *

Random telegraph noise Burst noise is a type of electronic noise that occurs in semiconductors and ultra-thin gate oxide films. It is also called random telegraph noise (RTN), popcorn noise, impulse noise, bi-stable noise, or random telegraph signal (RTS) noise. It co ...

(RTN) can also result, where the drain current fluctuates between several discrete levels, and is worsened with increasing temperature. * Bias temperature instability (BTI) is where charge leaks into the oxide when voltage is applied to the gate, even with no current flowing through the transistor. When the voltage is removed from the gate, the charges gradually dissipate between milliseconds or hours. Charge trapping was determined by John Szedon and Ting L. Chu to be a viable means of storing digital information, and was developed into the SONOS, MirrorBit, and 3D NAND flash memory technologies.

References

* *{{cite web , title=Silicon Aging and Signal Integrity , first=Alan , last=Sguigna , date=25 Aug 2013 , publisher=ASSET InterTech , url=https://blog.asset-intertech.com/test_data_out/2013/08/silicon-aging-and-signal-integrity.html , accessdate=21 Jun 2020 Transistors Semiconductor device defects

Causes

See also

References