Method of evaluating thin-film transistor, method of manufacturing thin-film transistor, and thin-film transistor

Patent metadata

Field	Value
Publication number	US-2016197198-A1
Application number	US-201414915704-A
Country	US
Kind code	A1
Filing date	Jun 25, 2014
Priority date	Sep 3, 2013
Publication date	Jul 7, 2016
Grant date	—

Abstract

A method of evaluating a thin-film transistor (TFT) which is disposed on a substrate, and includes at least: an oxide semiconductor layer which functions as a channel layer; and a channel protection layer disposed above the oxide semiconductor layer. The method includes: measuring a change in a reflectance of a microwave emitted to the oxide semiconductor layer while the oxide semiconductor layer is irradiated with excitation light by pulse irradiation; calculating a decay period which is a period of time taken for the reflectance to decay to 1/e or 1/e 2 , based on the change in the reflectance obtained in the measuring; and performing determination related to a threshold voltage of the oxide semiconductor layer, based on the decay period calculated in the calculating.

First claim

1 . A method of evaluating a thin-film transistor which is disposed on a substrate, and includes at least: an oxide semiconductor layer which functions as a channel layer; and a channel protection layer disposed above the oxide semiconductor layer, the method comprising:
measuring a change in a reflectance of a microwave emitted to the oxide semiconductor layer while the oxide semiconductor layer is irradiated with excitation light by pulse irradiation; calculating a decay period which is a period of time taken for the reflectance to decay from a first value to a second value, based on the change in the reflectance obtained in the measuring; and performing determination related to a threshold voltage of the oxide semiconductor layer, based on the decay period calculated in the calculating.

2 . The method of evaluating a thin-film transistor according to claim 1 , wherein
the decay period is at least one of a period of time taken for the reflectance to decay from a peak value to 1/e of the peak value, a period of time taken for the reflectance to decay from 1/e of the peak value to 1/e 2 of the peak value, and a period of time taken for the reflectance to decay from the peak value to 1/e 2 of the peak value, e being a base of natural logarithm.

3 . The method of evaluating a thin-film transistor according to claim 1 , wherein
the determination related to the threshold voltage is at least one of identification of the threshold voltage and determination of whether or not the threshold voltage falls within a predetermined range.

4 . The method of evaluating a thin-film transistor according to claim 1 , wherein
in the performing of determination, the threshold voltage of the oxide semiconductor layer corresponding to the decay period calculated in the calculating is identified by referring to a pre-calculated relation between a decay period and a threshold voltage.

5 . A method of evaluating a thin-film transistor which is disposed on a substrate and includes at least: an oxide semiconductor layer which functions as a channel layer; and a channel protection layer disposed above the oxide semiconductor layer, the method comprising:
measuring a change in a reflectance of a microwave emitted to the oxide semiconductor layer while the oxide semiconductor layer is irradiated with excitation light by pulse irradiation; calculating at least one of a decay period which is a period of time taken for the reflectance to decay from a first value to a second value, and a peak value of the reflectance, based on the change in the reflectance obtained in the measuring; and performing determination related to a resistance value of the oxide semiconductor layer, based on the decay period or the peak value calculated in the calculating.

6 . The method of evaluating a thin-film transistor according to claim 5 , wherein
the decay period is at least one of a period of time taken for the reflectance to decay from a peak value to 1/e of the peak value, a period of time taken for the reflectance to decay from 1/e of the peak value to 1/e 2 of the peak value, and a period of time required for the reflectance to decay from the peak value to 1/e 2 of the peak value, e being a base of natural logarithm.

7 . The method of evaluating a thin-film transistor according to claim 5 , wherein
the determination related to the resistance value is at least one of identification of the resistance value and determination of whether or not the resistance value falls within a predetermined range.

8 . The method of evaluating a thin-film transistor according to claim 6 , wherein
in the performing of determination, the resistance value of the oxide semiconductor layer corresponding to the at least one of the decay period and the peak value calculated in the calculating is identified by referring to a pre-calculated relation between a decay period or peak value and a resistance value.

9 . The method of evaluating a thin-film transistor according to claim 1 , wherein
the thin-film transistor is subjected to a first annealing treatment after forming of the channel protection layer, the first annealing treatment being for stabilizing the channel protection layer, and the measuring is performed subsequent to the first annealing treatment.

10 . The method of evaluating a thin-film transistor according to claim 1 , wherein
the thin-film transistor further includes a source electrode and a drain electrode which are disposed above the channel protection layer, and an interlayer insulating layer disposed above the source electrode and the drain electrode, and the measuring is performed after forming of the interlayer insulating layer.

11 . The method of evaluating a thin-film transistor according to claim 10 , wherein
the thin-film transistor is subjected to a second annealing treatment after forming of the interlayer insulating layer, the second annealing treatment being for stabilizing the interlayer insulating layer, and the measuring is performed subsequent to the second annealing treatment.

12 . The method of evaluating a thin-film transistor according to claim 1 , further comprising
positioning a measurement position to change a target position of the measurement performed in the measuring, wherein the measuring, the calculating, and the performing of determination are performed on the target position changed in the positioning.

13 . The method of evaluating a thin-film transistor according to claim 12 , wherein
the oxide semiconductor layer is formed by a sputtering method targeting a plurality of strip regions arranged at regular intervals on the substrate, and in the positioning, the target position of the measurement is changed to perform the measurement in the measuring on each of the plurality of strip regions and each of regions between adjacent ones of the strip regions.

14 . The method of evaluating a thin-film transistor according to claim 12 , wherein
the target position of measurement comprises a plurality of target positions of measurement, and the target position is sequentially changed among the plurality of target positions in the positioning, the plurality of target positions being arranged according to a tendency of at least one of (i) an increasing film thickness of the oxide semiconductor layer, (ii) a decreasing film thickness of the oxide semiconductor layer, (iii) a deteriorating film quality of the oxide semiconductor layer, and (iv) an improving film quality of the oxide semiconductor layer.

15 . The method of evaluating a thin-film transistor according to claim 12 , wherein
the target position of measurement comprises a plurality of target positions of measurement, and the target position is sequentially changed among the plurality of target positions in the positioning, the plurality of target positions being arranged according to a tendency of at least one of (i) an increasing temperature in an annealing treatment performed on the thin-film transistor and (ii) a decreasing temperature in the annealing treatment.

16 . The method of evaluating a thin-film transistor according to claim 1 ,
wherein the microwave has a frequency of 10 GHz or higher.

17 . The method of evaluating a thin-film transistor according to claim 1 ,
wherein the excitation light has a wavelength of 500 nm or shorter.

18 . A method of manufacturing a thin-film transistor, comprising:
forming an oxide semiconductor layer above a substrate, the oxide semiconductor layer functioning as a channel layer; forming a channel protection layer above

Assignees

• Joled Inc

Inventors

• Takeda Eiji
• Saito Toru

Classifications

• H10P14/3434

  being oxide semiconductor materials (Group IIB-VIA semiconductor materials H10P14/3424) · CPC title

• H10P14/3426

  Oxides · CPC title

• H10P14/22

  using physical deposition, e.g. vacuum deposition or sputtering · CPC title

• H10P95/90

  Thermal treatments, e.g. annealing or sintering · CPC title

• H10P74/207

  Electrical properties, e.g. testing or measuring of resistance, deep levels or capacitance-voltage characteristics · CPC title