117:(weak inversion) show up initially as a simple translation of the subthreshold current vs. gate bias curve with change in drain-voltage, which can be modeled as a simple change in threshold voltage with drain bias. However, at shorter lengths the slope of the current vs. gate bias curve is reduced, that is, it requires a larger change in gate bias to effect the same change in drain current. At extremely short lengths, the gate entirely fails to turn the device off. These effects cannot be modeled as a threshold adjustment.
20:
82:
between the drain and body increases in size and extends under the gate, so the drain assumes a greater portion of the burden of balancing depletion region charge, leaving a smaller burden for the gate. As a result, the charge present on the gate retains charge balance by attracting more carriers
271:
611:
90:
for electrons in the channel is lowered. Hence the term "barrier lowering" is used to describe these phenomena. Unfortunately, it is not easy to come up with accurate analytical results using the barrier lowering concept.
66:
was independent of drain voltage. In short-channel devices this is no longer true: The drain is close enough to gate the channel, and so a high drain voltage can open the bottleneck and turn on the transistor prematurely.
61:
with a long channel, the bottleneck in channel formation occurs far enough from the drain contact that it is electrostatically shielded from the drain by the combination of the substrate and gate, and so classically the
98:
with the body, and so have associated built-in depletion layers associated with them that become significant partners in charge balance at short channel lengths, even with no reverse bias applied to increase
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is the low drain voltage (for a linear part of device I-V characteristics). The minus in the front of the formula ensures a positive DIBL value. This is because the high drain threshold voltage,
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of the device and that in the channel of the device is balanced by three electrode charges: the gate, the source and the drain. As drain voltage is increased, the
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The origin of the threshold decrease can be understood as a consequence of charge neutrality: the Yau charge-sharing model. The combined charge in the
106:
The term DIBL has expanded beyond the notion of simple threshold adjustment, however, and refers to a number of drain-voltage effects upon MOSFET
706:
124:, causing the current to increase with drain bias, lowering the MOSFET output resistance. This increase is additional to the normal
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Barrier lowering increases as channel length is reduced, even at zero applied drain bias, because the source and drain form
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266:{\displaystyle \mathrm {DIBL} =-{\frac {V_{Th}^{DD}-V_{Th}^{\mathrm {low} }}{V_{DD}-V_{D}^{\mathrm {low} }}},}
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curves that go beyond description in terms of simple threshold voltage changes, as described below.
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or Vtlin is the threshold voltage measured at a very low drain voltage, typically 0.05 V or 0.1 V.
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DIBL can reduce the device operating frequency as well, as described by the following equation:
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or Vtsat is the threshold voltage measured at a supply voltage (the high drain voltage), and
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In effect, the channel becomes more attractive for electrons. In other words, the potential
75:
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into the channel, an effect equivalent to lowering the threshold voltage of the device.
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effect on output resistance, and cannot always be modeled as a threshold adjustment.
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606:{\displaystyle {\frac {\Delta f}{f}}=-{\frac {2\mathrm {DIBL} }{V_{DD}-V_{Th}}},}
30:
to be surmounted by an electron from the source on its way to the drain reduces
19:
728:(Second ed.). New York: Oxford University Press. p. 268; Fig. 6.11.
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467:, is always smaller than the low drain threshold voltage,
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DIBL also affects the current vs. drain bias curve in the
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As channel length is reduced, the effects of DIBL in the
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Mosfet
Modeling for VLSI Simulation: Theory And Practice
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In practice, the DIBL can be calculated as follows:
389:is the supply voltage (the high drain voltage) and
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57:at higher drain voltages. In a classic planar
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725:Operation and Modeling of the MOS Transistor
701:. World Scientific. p. 197, Fig. 5.14.
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23:As channel length decreases, the barrier
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503:{\displaystyle V_{Th}^{\mathrm {low} }}
352:{\displaystyle V_{Th}^{\mathrm {low} }}
49:referring originally to a reduction of
422:{\displaystyle V_{D}^{\mathrm {low} }}
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510:. Typical units of DIBL are mV/V.
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35:Drain-induced barrier lowering
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460:{\displaystyle V_{Th}^{DD}}
309:{\displaystyle V_{Th}^{DD}}
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678:is the threshold voltage.
648:is the supply voltage and
753:Channel length modulation
126:channel length modulation
722:Yannis Tsividis (2003).
59:field-effect transistor
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671:{\displaystyle V_{Th}}
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641:{\displaystyle V_{DD}}
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382:{\displaystyle V_{DD}}
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695:Narain Arora (2007).
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758:Threshold voltage
708:978-981-256-862-5
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64:threshold voltage
51:threshold voltage
16:Effect in MOSFETs
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763:MOSFET operation
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88:energy barrier
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80:p-n junction
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122:active mode
772:Categories
735:0195170148
682:References
55:transistor
582:−
544:−
529:Δ
232:−
188:−
161:−
747:See also
783:MOSFETs
78:of the
53:of the
47:MOSFETs
41:) is a
732:
705:
618:where
278:where
25:φ
730:ISBN
703:ISBN
39:DIBL
108:I-V
45:in
774::
103:.
738:.
711:.
664:h
661:T
657:V
634:D
631:D
627:V
601:,
593:h
590:T
586:V
577:D
574:D
570:V
563:L
560:B
557:I
554:D
550:2
541:=
536:f
532:f
495:w
492:o
489:l
483:h
480:T
476:V
453:D
450:D
445:h
442:T
438:V
414:w
411:o
408:l
402:D
398:V
375:D
372:D
368:V
344:w
341:o
338:l
332:h
329:T
325:V
302:D
299:D
294:h
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287:V
261:,
252:w
249:o
246:l
240:D
236:V
227:D
224:D
220:V
211:w
208:o
205:l
199:h
196:T
192:V
183:D
180:D
175:h
172:T
168:V
158:=
154:L
151:B
148:I
145:D
37:(
27:B
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