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 method of making a DR detector comprising:
forming a gate layer on a substrate;
forming an insulator layer over the gate layer;
forming an a-IGZO active layer over the insulator;
forming a first passivation layer over the a-IGZO active layer;
patterning the a-IGZO active layer and the passivation layer;
forming a source and a drain each in electrical contact with the a-IGZO active layer;
forming a second passivation layer over at least the source and the drain;
forming a scintillator layer over the second passivation layer;
electrically connecting a read-out circuit to the a-IGZO active layer; and
enclosing the formed layers and components in a DR detector housing,
wherein the step of forming the a-IGZO active layer includes using sputtering, and wherein the steps of forming the insulator layer and the a-IGZO active layer are performed in a vacuum tight chamber without breaking vacuum.
2. The method of claim 1 , further comprising forming the second passivation layer over the insulator layer and the first passivation layer.
3. The method of claim 1 , wherein the step of forming the source and drain comprises using molybdenum and covering any exposed portions of the a-IGZO active layer.
4. The method of claim 1 , further comprising patterning the a-IGZO active layer and the first passivation layer into isolated islands of the a-IGZO active layer and the material used for the first passivation layer.
5. The method of claim 1 , wherein the gate layer comprises molybdenum.
6. A method of making a DR detector comprising:
forming a gate layer on a substrate;
forming in consecutive steps in a vacuum tight chamber without breaking vacuum: only one insulator layer over the gate layer; only one a-IGZO active layer over the insulator layer; and only one first passivation layer over the a-IGZO active layer;
patterning the a-IGZO active layer and the first passivation layer;
forming a source and a drain each in electrical contact with the a-IGZO active layer;
forming a second passivation layer over at least the source and the drain;
forming a scintillator layer over the second passivation layer;
electrically connecting a read-out circuit to the a-IGZO active layer; and
enclosing the formed layers and components in a DR detector housing.
7. The method of claim 6 , further comprising forming the second passivation layer over the insulator layer and the first passivation layer.
8. The method of claim 6 , wherein the step of forming the source and drain comprises using molybdenum and covering any exposed portions of the a-IGZO active layer.
9. The method of claim 8 , further comprising patterning the a-IGZO active layer and the first passivation layer into isolated islands on the insulator layer.
10. The method of claim 6 , wherein the step of forming the gate layer comprises using molybdenum.
11. The method of claim 6 , wherein the steps of forming the first passivation layer and forming the second passivation layer each comprises using SiO 2 .
12. A method of making a DR detector comprising:
forming a gate layer on a substrate;
forming in consecutive steps in a vacuum tight chamber without breaking vacuum: only one insulator layer over the gate layer; only one a-IGZO active layer over the insulator layer wherein the only one a-IGZO active layer comprises a thickness of about 7 nm or less; and only one first passivation layer over the a-IGZO active layer;
patterning the a-IGZO active layer and the first passivation layer;
forming a source and a drain each in electrical contact with the a-IGZO active layer;
forming a second passivation layer over at least the source and the drain;
forming a scintillator layer over the second passivation layer;
electrically connecting a read-out circuit to the a-IGZO active layer; and
enclosing the formed layers and components in a DR detector housing.
13. The method of claim 12 , further comprising forming the only one a-IGZO active layer over the insulator layer at a thickness of about 5 nm or less.
14. The method of claim 12 , further comprising forming the only one a-IGZO active layer over the insulator layer at a thickness of about 3 nm.
15. The method of claim 12 , wherein the steps of forming the first passivation layer and forming the second passivation layer each comprises using a common material.
16. The method of claim 12 , wherein the steps of forming the first passivation layer and forming the second passivation layer each comprises using SiO 2 .