BS IEC 62951-2-2019 pdf free download – Semiconductor devices – Flexible and stretchable semiconductor devices Part 2: Evaluation method for electron mobility, sub-threshold swing, and threshold voltage of flexible devices.
This part of lEC 62951 specifies terms,definitions，symbols，configurations and evaluationmethods that can be used to evaluate and determine the performance characteristics offlexible thin-film transistor (TFT) devices. This document specifies test methods andcharacteristic parameters for accurately evaluating the performance and reliability in practicaluse of flexible TFT devices under the bending status.
2Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
Iso and lEC maintain terminological databases for use in standardization at the followingaddresses:
. ·IEC Electropedia: available at http://www.electropedia.orgl
. -Iso Online browsing platform: available at http://www.iso.orglobp
3.1
flexible thin-film transistorflexible TFT
thin-film transistor fabricated on mechanically flexible substrates such as polymers and metalfoils
Note 1 to entry: This note applies to the French language only.3.2
mobility
<of an electron> quantity equal to the quotient of the modulus of the mean velocity of acharge carrier (electron) in the direction of an electric field by the modulus of the field strength
[SOURCE: IEC 60050-521:2002,521-02-58,modified — “electron” has been added.]
3.3
sub-threshold swings
parameter for quantifying how sharply the transistor is turned off by the gate voltage,definedby the following formula
where Cand coxrepresent depletion layer capacitance and gate-oxide capacitance,respectively
3.4
threshold voltage
gate-source voltage at which the magnitude of the drain current reaches a specified low value
[SOURCE: IEC 60050-521:2002,521-07-24]
3.5
gate voltagevcs
voltage between gate and source
3.6
drain voltageVDs
voltage between drain and source
3.7
drain currentlos
current between drain and source
3.8
transconductancegm
ratio of the increment in the drain current to a corresponding incremental change of thegate-source voltage with the drain-source voltage held constant
[SOURCE: IEC 60050-521:2002,521-07-25]
4Test method
4.1General
To investigate the reliability of the flexible TFTs,bending tests are performed as follows(see Figure 1):
a) prior to any bending, the electrical characteristics of the TFTs are measured;
b) under the mechanical bending state，the electrical characteristics of the TFTs are re-measured as shown in Figure 3.
4.2Test of electrical characteristics before bending
The stability test of a flexible TFT is carried out using four kinds of biased evaluation. Thenegative-bias-stress(NBS) test is carried out with a Vcs of -20 V at a fixed Vps of 10 V underdark and the substrate temperature is maintained at 20 C and~60 C. Thenegative-bias-illumination-stress (NBIS) test is carried out with a VGs of -20 v at a fixed Vpsof 10 V under illumination with a white light-emitting diode of 300 cd/m2 brightness and thesubstrate temperature is maintained at 20 C and 60 C. The positive-bias-stress (PBS) test iscarried out with a VGs of +20 v at a fixed Vps of 0,1 v under dark and the substratetemperature is maintained at 20 C and 60 c.the positive-bias-illumination-stress (PBIS)test is carried out with a VGs of +20 v at a fixed Vos of 0,1 V under illumination with a whitelight-emitting diode of 300~cd/m2 brightness and the substrate temperature is maintained at2oC and 6o oc.
In the test procedure，the drain current is measured at room temperature by sweeping thegate voltage from -30 V to 30 V, at a fixed drain voltage of 0,1 V.Afterwards, the devicestability tests are performed for 3 h. The field-effect mobility shall be calculated usingFormula (1).The mobility is extracted from the linear-regime transconductance gm at the lowdrain voltage of 0,1 v as follows:
where, L and W are the channel length and width, respectively.The sub-threshold swing shallbe obtained using the slope of transfer curves in the sub-threshold regime by application ofFormula (2).BS IEC 62951-2 pdf download.