Reduction of TFT instability in digital X-ray detectors
A digital radiographic detector uses an IGZO active layer in the switching element for each imaging pixel in a two-dimensional array of imaging pixels. Each imaging pixel has a photo-sensitive element and the switching element. Read-out circuits electrically connected to the two-dimensional array generate a radiographic image by reading out image data by switching on and off the switching elements. The IGZO active layer may be formed having a thickness less than about 7 nm.
1. A digital radiographic detector comprising:
a two-dimensional array of imaging pixels, each imaging pixel comprising a photo-sensitive element and a switching element;
read-out circuits electrically coupled to the two-dimensional array of imaging pixels to generate a radiographic image by reading out image data from the two-dimensional array of imaging pixels; and
a housing enclosing the two-dimensional array of imaging pixels and the read-out circuits,
wherein each switching element in the two-dimensional array of imaging pixels comprises an active layer formed from indium-gallium-zinc oxide having a thickness less than about 7 nm.
2. The detector of claim 1 , wherein the active layer is formed from indium-gallium-zinc oxide having a thickness less than about 5 nm.
3. The detector of claim 1 , wherein the active layer is formed from indium-gallium-zinc oxide having a thickness of about 3 nm.
4. The detector of claim 1 , wherein the read-out circuits include gate drivers electrically connected to the active layer in each switching element.
5. A DR detector comprising:
a gate layer on a substrate;
an insulator layer over the gate layer;
a patterned a-IGZO active layer over the insulator;
a patterned first passivation layer over the a-IGZO active layer;
a source and a drain each in electrical contact with the a-IGZO active layer;
a second passivation layer over at least the source and the drain;
a scintillator layer over the second passivation layer;
a read-out circuit electrically connected to the a-IGZO active layer; and
a DR detector housing enclosing the gate layer, the insulator layer, the patterned a-IGZO active layer, the patterned first passivation layer, the second passivation layer, the scintillator layer, the source and drain, and the read-out circuit,
wherein the a-IGZO active layer is formed using sputtering, and wherein the insulator layer and the a-IGZO active layer are formed in a vacuum tight chamber without breaking vacuum.
6. The detector of claim 5 , further comprising the second passivation layer disposed over the insulator layer and the first passivation layer.
7. The detector of claim 6 , wherein the source and drain comprises molybdenum.
8. The detector of claim 7 , wherein the a-IGZO active layer and the first passivation layer comprise isolated islands of the a-IGZO active layer and the first passivation layer.
9. The detector of claim 8 , wherein the gate layer comprises molybdenum.
10. A DR detector comprising:
a gate layer on a substrate;
only one insulator layer over the gate layer;
only one patterned a-IGZO active layer over the insulator layer;
only one patterned first passivation layer over the a-IGZO active layer;
a source and a drain each in electrical contact with the a-IGZO active layer;
a second passivation layer over at least the source and the drain;
a scintillator layer over the second passivation layer;
a read-out circuit electrically connected to the a-IGZO active layer; and
a DR detector housing enclosing the gate layer, the insulator layer, the patterned a-IGZO active layer, the patterned first passivation layer, the second passivation layer, the scintillator layer, the source and drain, and the read-out circuit.
11. The DR detector of claim 10 , further comprising the second passivation layer over the insulator layer and the first passivation layer.
12. The DR detector of claim 10 , wherein the source and drain comprise molybdenum.
13. The DR detector of claim 12 , wherein the a-IGZO active layer and the first passivation layer are shaped as isolated islands on the insulator layer.
14. The DR detector of claim 10 , wherein the gate layer comprises molybdenum.
15. The DR detector of claim 10 , wherein the first passivation layer and the second passivation layer each comprise SiO 2 .
16. The DR detector of claim 10 , wherein the only one patterned a-IGZO active layer comprises a thickness of about 5 nm or less.
17. The DR detector of claim 16 , wherein the only one patterned a-IGZO active layer comprises a thickness of about 3 nm.
18. The DR detector of claim 16 , wherein the first passivation layer and the second passivation layer comprise a common material.