Flexible substrate, method of fabricating the same, and thin film transistor using the same

A method of fabricating a flexible substrate, comprising:

• forming a metal substrate having a predetermined coefficient of thermal expansion;
• and
• forming a buffer layer on the metal substrate, the buffer layer including a silicon oxide or a silicon nitride,
• wherein the predetermined coefficient of thermal expansion of the metal substrate satisfies an equation as follows:
• α
• f
• +
• 0.162
• ×
• (
• 1
• -
• v
• f
• )
• E
• f
• ≤
• α
• s
• ≤
• α
• f
• +
• 0.889
• ×
• (
• 1
• -
• v
• f
• )
• E
• f
• Ef representing Young's modulus of the buffer layer, vf representing Poisson's ratio of the buffer layer, αf representing a coefficient of thermal expansion of the buffer layer, and αs representing the predetermined coefficient of thermal expansion of the metal substrate.

A thin film transistor (TFT), comprising:

• a metal substrate having a predetermined coefficient of thermal expansion;
• and
• a buffer layer on the metal substrate, the buffer layer including a silicon oxide or a silicon nitride;
• a semiconductor layer on the buffer layer, the semiconductor layer including a source region, a drain region, and a channel region;
• a gate electrode on the semiconductor layer, the gate electrode overlapping the channel region of the semiconductor layer;
• a gate insulating layer between the semiconductor layer and the gate electrode;
• a source electrode electrically connected with the source region of the semiconductor layer;
• and
• a drain electrode electrically connected with the drain region of the semiconductor layer,
• wherein the predetermined coefficient of thermal expansion of the metal substrate satisfies an equation as follows,
• α
• f
• +
• 0.162
• ×
• (
• 1
• -
• v
• f
• )
• E
• f
• ≤
• α
• s
• ≤
• α
• f
• +
• 0.889
• ×
• (
• 1
• -
• v
• f
• )
• E
• f
• Ef representing Young's modulus of the buffer layer, vf representing Poisson's ratio of the buffer layer, αf representing a coefficient of thermal expansion of the buffer layer, and αs representing the predetermined coefficient of thermal expansion of the metal substrate.