Backplane substrate, manufacturing method for the same, and organic light-emitting display device using the same

A backplane substrate of a display device, comprising:

• a substrate having an active area and a peripheral area where the active area has a plurality of sub-pixels;
• a driving thin-film transistor located in each sub-pixel and including a first gate electrode, a first active layer located above the first gate electrode, a first source electrode and a first drain electrode connected to opposite sides of a first channel of the first active layer, and a first gate insulating layer between the first active layer and the first gate electrode;
• and
• a switching thin-film transistor located at each sub-pixel, connected to the driving thin-film transistor and including a second gate electrode, a second active layer located below the second gate electrode, a second source electrode and a second drain electrode connected to opposite sides of a second channel of the second active layer, and a second gate insulating layer between the second active layer and the second gate electrode,
• wherein the first active layer and the second active layer are located at the same layer, and
• wherein a first distance between the first gate electrode and the first active layer is greater than a second distance between the second gate electrode and the second active layer.

A method of manufacturing a backplane substrate of a display device, the method comprising:

• forming plurality of sub-pixels on a substrate, each sub-pixel having a first area and a second area partitioned from each other;
• forming a first gate electrode in the first area of the sub-pixel;
• forming a first gate insulating layer having a first thickness covering the first gate electrode;
• forming a first active layer and a second active layer on the first gate insulating layer in the first area and the second area respectively;
• forming a second gate insulating layer having a second thickness, which is smaller than the first thickness covering the first and second active layers;
• forming a second gate electrode on the second gate insulating layer corresponding to a top of the second active layer;
• and
• forming a first source electrode and a first drain electrode connected to opposite sides of the first active layer and a second source electrode and a second drain electrode connected to opposite sides of the second active layer.

An organic light-emitting display device comprising:

• a substrate having a plurality of sub-pixels;
• a driving thin-film transistor located in each sub-pixel and including a first gate electrode, a first active layer located above the first gate electrode, a first source electrode and a first drain electrode connected to opposite sides of a first channel of the first active layer, and a first gate insulating layer between the first active layer and the first gate electrode;
• and
• a switching thin-film transistor located in each sub-pixel connected to the driving thin-film transistor and including a second gate electrode, a second active layer located below the second gate electrode, a second source electrode and a second drain electrode connected to opposite sides of a second channel of the second active layer, and a second gate insulating layer between the second active layer and the second gate electrode;
• a storage capacitor between the first gate electrode and the first source electrode;
• and
• an organic light-emitting diode including an anode connected to the first source electrode, a cathode opposite the anode, and an organic layer including an organic light-emitting layer located between the anode and the cathode,
• wherein the first active layer and the second active layer are located at the same layer, and
• wherein a first distance between the first gate electrode and the first active layer is greater than a second distance between the second gate electrode and the second active layer.

A backplane substrate of a display, comprising:

• a plurality of sub-pixels at a substrate;
• a driving thin-film transistor at each sub-pixel and including a first insulation layer, a first gate electrode, a first active layer and having a first distance between the first gate electrode and the first active layer;
• and
• a switching thin-film transistor at each sub-pixel and electrically connected to the driving thin-film transistor and including a second insulation layer, a second gate, a second active layer and having a second distance between the second gate and the second active layer,
• wherein the first gate insulation layer has a thickness great enough, so that the driving thin-film transistor has an S-factor of at least 0.2 V/dec and a gate-to-source voltage differential of at least 1.0 V, and the second insulation has a thickness smaller than that of the first gate insulation layer,
• wherein the S-factor (S) is defined by:
• S
• =
• 2.3
• 
• kT
• q
• 
• [
• 1
• +
• (
• C
• d
• +
• Cit
• )
• C
• i
• ]
• where Ci is a capacity of a gate insulating layer, Cd is a capacity of a depletion area in an active layer, Cit is a captured density of a gap in the gate insulating layer and kT/q is a thermal voltage of the display device.