BS IEC 62951-2 pdf free download
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 IEC 62951 specifies terms, definitions, symbols, configurations and evaluation methods that can be used to evaluate and determine the performance characteristics of flexible thin-film transistor (TFT) devices. This document specifies test methods and characteristic parameters for accurately evaluating the performance and reliability in practical use of flexible TFT devices under the bending status.
2 Normative 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 IEC maintain terminological databases for use in standardization at the following addresses:
• • IEC Electropedia: available at http:/Iwww.electropedia.orgl
• • ISO Online browsing platform: available at http://www.iso.org/obp
3.1 flexible thin-film transistor flexible TFT
thin-film transistor fabricated on mechanically flexible substrates such as polymers and metal foils
Note 1 to entry: ThIs note applies to Ihe French language only.
3.2 mobility
<of an electron> quantity equal to the quotient of the modulus of the mean velocity of a charge 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 swing S parameter for quantifying how sharply the transistor is turned off by the gate voltage, defined by the following formula
where C and C0, represent 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 voltage 1GS voltage between gate and source
3.6 drain voltage 1DS voltage between drain and source
3.7 drain current ‘Os current between drain and source
3.8 transconductance gm
ratio of the increment in the drain current to a corresponding incremental change of the gate-source voltage with the drain-source voltage held constant
[SOURCE: IEC 60050-521:2002, 521-07-25]
4 Test method
4.1 General
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.
4.2 Test of electrical characteristics before bending The stability test of a flexible TFT is carried out using four kinds of biased evaluation. The negative-bias-stress (NBS) test is carried out with a VGs of -20 V at a fixed Vos of 10 V under dark and the substrate temperature is maintained at 20 oC and 60 0C. The negative- bias-illumination-stress (NBIS) test is carried out with a VGs of -20 V at a fixed Vos of 10 V under ilumination with a white light-emitting diode of 300 cd/m2 brightness and the substrate temperature is maintained at 20°C and 60 oC. The positive-bias-stress (PBS) test is carried out with a VGs of +20 V at a fixed Vps of 0,1 V under dark and the substrate temperature is maintained at 20 °C and 60 °C. The positive- bias-illumination-stress (PBIS) test is carried out with a Vss of +20 V at a fixed Vps of 0,1 V under ilumination with a white light-emitting diode of 300 cd/m2 brightness and the substrate temperature is maintained at 20 °C and 60 0C. In the test procedure, the drain current is measured at room temperature by sweeping the gate voltage from -30 V to 30 V, at a fixed drain voltage of 0,1 V. Afterwards, the device stability tests are performed for 3 h. The field-effect mobility shall be calculated using Formula (1). The moility is extracted from the linear-regime transconductance gm at the low drain voltage of 0,1 V as follows:
where, L and W are the channel length and width, respectively. The sub-threshold swing shall be obtained using the slope of transfer curves in the sub-threshold regime by application of Formula (2). BS IEC 62951-2 pdf download.
