SUBSTRATE FOR FLEXIBLE DISPLAY AND METHOD OF MANUFACTURING THE SUBSTRATE
A substrate for a flexible display is disclosed. The substrate has a film stress range that does not affect an electronic device such as a thin film transistor, and includes a barrier layer having excellent oxygen and moisture blocking characteristics, and a method of manufacturing the substrate. The substrate includes: a plastic substrate having a glass transition temperature from about 350° C. to about 500° C.; and a barrier layer disposed on the plastic substrate, having a multi-layer structure, wherein at least one silicon oxide layer and at least one silicon nitride layer are alternately stacked on each other, and having a film stress from about −200 MPa to about 200 MPa due to the at least one silicon oxide layer and the at least one silicon nitride layer.
1 . A flexible substrate, comprising:
a plastic substrate having a glass transition temperature from about 350° C. to about 500° C.; and
a barrier layer disposed on the plastic substrate, having a multi-layer structure, which comprises at least one silicon oxide layer and at least one silicon nitride layer that are alternately stacked on each other, the barrier layer having a film stress from about −200 MPa to about 200 MPa.
2 . The substrate of claim 1 , wherein the barrier layer comprises:
a first silicon oxide layer;
a silicon nitride layer stacked on the first silicon oxide layer; and
a second silicon oxide layer stacked on the silicon nitride layer.
3 . The substrate of claim 1 , wherein the barrier layer comprises:
a first silicon oxide layer;
a first silicon nitride layer stacked on the first silicon oxide layer;
a second silicon oxide layer stacked on the first silicon nitride layer;
a second silicon nitride layer stacked on the second silicon oxide layer; and
a third silicon oxide layer stacked on the second silicon nitride layer.
4 . The substrate of claim 1 , wherein the barrier layer comprises:
a first silicon oxide layer;
a first silicon nitride layer stacked on the first silicon oxide layer;
a second silicon oxide layer stacked on the first silicon nitride layer;
a second silicon nitride layer stacked on the second silicon oxide layer;
a third silicon oxide layer stacked on the second silicon nitride layer;
a third silicon nitride layer stacked on the third silicon oxide layer; and
a fourth silicon oxide layer stacked on the third silicon nitride layer.
5 . The substrate of claim 1 , wherein the at least one silicon oxide layer has compressive film stress, and wherein the at least one silicon nitride layer has tensile film stress.
6 . The substrate of claim 1 , wherein a film density of the at least one silicon nitride layer is from about 2.5 g/cm 3 to about 2.7 g/cm 3 .
7 . The substrate of claim 1 , wherein a hydrogen atom content in the at least one silicon nitride layer is from about 13% to about 17%.
8 . The substrate of claim 1 , wherein a thickness of each of the at least one silicon nitride layer is from about 200 Å to about 1000 Å.
9 . The substrate of claim 1 , wherein a thickness of each of the at least one silicon oxide layer is from about 1000 Å to about 3000 Å.
10 . The substrate of claim 1 , wherein the plastic substrate comprises polyimide.
11 . A method of manufacturing a flexible substrate, the method comprising:
providing a plastic substrate having a glass transition temperature from about 350° C. to about 500° C.; and
forming a barrier layer having a film stress from about −200 MPa to about 200 MPa by alternately stacking at least one silicon oxide layer and at least one silicon nitride layer on the plastic substrate.
12 . The method of claim 11 , wherein the forming of the barrier layer comprises forming the barrier layer using a high temperature deposition technique at a temperature from about 350° C. to about 400° C.
13 . The method of claim 11 , wherein the barrier layer comprises:
a first silicon oxide layer;
a silicon nitride layer stacked on the first silicon oxide layer; and
a second silicon oxide layer stacked on the silicon nitride layer.
14 . The method of claim 11 , wherein the barrier layer comprises:
a first silicon oxide layer;
a first silicon nitride layer stacked on the first silicon oxide layer;
a second silicon oxide layer stacked on the first silicon nitride layer;
a second silicon nitride layer stacked on the second silicon oxide layer; and
a third silicon oxide layer stacked on the second silicon nitride layer.
15 . The method of claim 11 , wherein the barrier layer comprises:
a first silicon oxide layer;
a first silicon nitride layer stacked on the first silicon oxide layer;
a second silicon oxide layer stacked on the first silicon nitride layer;
a second silicon nitride layer stacked on the second silicon oxide layer;
a third silicon oxide layer stacked on the second silicon nitride layer;
a third silicon nitride layer stacked on the third silicon oxide layer; and
a fourth silicon oxide layer stacked on the third silicon nitride layer.
16 . The method of claim 11 , wherein the at least one silicon oxide layer has compressive film stress, and wherein the at least one silicon nitride layer has tensile film stress.
17 . The method of claim 11 , wherein a film density of the at least one silicon nitride layer is from about 2.5 g/cm 3 to about 2.7 g/cm 3 .
18 . The method of claim 11 , wherein a hydrogen atom content in the at least one silicon nitride layer is from about 13% to about 17%.