METHOD OF FABRICATING ZnO FILM AND THIN FILM TRANSISTOR ADOPTING THE ZnO FILM

Abstract

Provided is a method of fabricating a low temperature ZnO polycrystalline film and a thin film transistor (TFT) adopting the low temperature ZnO polycrystalline film. The method includes growing ZnO on a substrate at a first temperature for a first time using Metal Organic Chemical Vapor Deposition (MOCVD) to form a ZnO buffer layer, and heating the substrate at a temperature lower than the first temperature to grow ZnO on the ZnO buffer layer for a second time longer than the first time so as to form a ZnO film.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

FIGS. 1 through 3 are cross-sectional views illustrating a method of fabricating a low temperature ZnO film;

FIGS. 4 and 5 are cross-sectional views of ZnO thin film transistors (TFTs);

FIGS. 6 through 8 are graphs illustrating the results of quantitative analyses of elements of a ZnO film by an X-ray photoelectron spectroscopy (“XPS”); and

FIGS. 9 and 10 are graphs illustrating variations in drain current characteristics of TFT samples.

Claims

1. A method of fabricating a ZnO film, comprising: growing ZnO on a substrate at a first temperature for a first time using MOCVD (Metal Organic Chemical Vapor Deposition) to form a ZnO buffer layer; andheating the substrate at a temperature lower than the first temperature to grow ZnO on the ZnO buffer layer for a second time longer than the first time so as to form a ZnO film.

2. The method of claim 1, wherein the first temperature is greater than or equal to 300° C., and the second temperature is less than or equal to 300° C.

3. The method of claim 1, wherein the substrate is plastic or silicon.

4. The method of claim 1, wherein the second temperature is about 250° C.

5. The method of claim 1, wherein a thickness of the ZnO buffer layer is within a range between 1 nm and 1,000 nm.

6. The method of claim 1, wherein DEZ (diethylzinc) is used as a precursor for growing the ZnO.

7. The method of claim 6, wherein when the ZnO buffer layer is grown, O2:DEZ are supplied in a flow ratio of greater than or equal to about 1,000:1.

8. The method of claim 7, wherein when the ZnO film is grown, O2:DEZ are supplied in a flow ratio of greater than or equal to about 1800:1.

9. The method of claim 4, wherein when the ZnO film is grown, O2:DEZ are supplied in a flow ratio of greater than or equal to 1,000:1.

10. The method of claim 9, wherein when the ZnO film is grown, O2:DEZ are supplied in a flow ratio of greater than or equal to about 1,800:1.

11. A method of fabricating a ZnO TFT (thin film transistor) comprising a substrate, a ZnO semiconductor layer formed on a surface of the substrate, a source and a drain disposed on and contacting a surface of the ZnO semiconductor layer opposite the substrate, and a gate forming an electric field around the ZnO semiconductor layer, comprising: forming the ZnO semiconductor layer by;growing ZnO on the substrate at a first temperature for a first time using MOCVD to form a ZnO buffer layer; andheating the substrate at a temperature lower than the first temperature to grow ZnO on the ZnO buffer layer for a second time longer than the first time so as to form a ZnO film.

12. The method of claim 11, wherein the first temperature is greater than or equal to 300° C., and the second temperature is greater than or equal to 300° C.

13. The method of claim 11, wherein the substrate is silicon or plastic.

14. The method of claim 11, wherein the second temperature is about 250° C.

15. The method of claim 11, wherein DEZ is used as a precursor for growing the ZnO.

16. The method of claim 15, wherein when the ZnO film is grown, O2:DEZ are supplied in a flow ratio of greater than or equal to about 1,000:1.

17. The method of claim 16, wherein O2:DEZ is supplied in a flow ratio of about 1,800:1.