Manufacture of electronic devices comprising thin-film circuit elements
In the manufacture of an electronic device such as an active matrix display, a vertical amorphous PIN photodiode or similar thin-film diode (D) is advantageously integrated with a polysilicon TFT (TFT 1 , TFT 2 ) in a manner that permits a good degree of optimization of the respective TFT and diode properties while being compatible with the complex pixel context of the display. High temperature processes for making the active semiconductor film ( 10 ) of the TFT more crystalline than an active semiconductor film ( 40 ) of the diode and for forming the source and drain doped regions (s 1 ,s 2 , d 1 ,d 2 ) of the TFT are carried out before depositing the active semiconductor film ( 40 ) of the diode. Thereafter, the lateral extent of the diode is defined by etching while protecting with an etch-stop film ( 30 ) an interconnection film ( 20 ) that can provide a doped bottom electrode region ( 41 ) of the diode as well as one of the doped regions (s 2 , g 1 ) of the TFT.
1. A method of manufacturing an electronic device comprising thin-film circuit elements that include a diode integrated with a crystalline thin-film transistor, the transistor having a channel area in an active semiconductor film that is more crystalline than an active semiconductor film of the diode, comprising:
forming on a circuit substrate the crystalline active semiconductor film of the transistor with a first process involving a first processing temperature;
forming doped source and drain regions of the transistor at ends of the channel area with a second process involving a second processing temperature;
providing an interconnection film between an electrode area of the transistor and a diode area over which the diode is to be formed, and providing an etch-stop film on which the active semiconductor film for the diode is to be deposited;
depositing the active semiconductor film for the diode over the interconnection film and the etch-stop film with a third process that involves a third processing temperature, the first and second processing temperatures being higher than the third processing temperature; and
etching away the active semiconductor film for the diode from over the etch-stop film to leave the active semiconductor film for the diode over the interconnection film in the diode area;
wherein the diode has its active semiconductor film forming an intrinsic region between P and N electrode regions of a vertical PIN diode structure, and wherein the interconnection film comprises a doped region in a semiconductor film together with the doped source and drain regions of the transistor and a bottom one of the P and N electrode regions of the PIN diode.
2. The method of claim 1 , wherein the etch-stop film is an insulating film that extends over the interconnection film and that has a window at the diode area to permit contact between the interconnection film and the active semiconductor film of the diode.
3. The method of claim 1 , wherein regions of the crystalline active semiconductor film are doped to provide the source and drain regions of the transistor, the bottom one of the P and N electrode regions of the PIN diode, and the interconnection film therebetween.
4. The method of claim 3 , wherein the electronic device comprises first and second crystalline thin-film transistors integrated with the PIN diode by the interconnection film, and wherein the interconnection film provides the bottom one of the P and N electrode regions of the PIN diode, the top gate electrode of the first transistor, and/or the source and drain regions of the second transistor.
5. The method of claim 4 , wherein the electronic device comprises an active-matrix electroluminescent display with a light-emitting diode in each pixel, and wherein the light-emitting diode is driven via the first transistor as addressed via the second transistor.
6. The method of claim 1 , wherein at least a portion of the interconnection film is provided on a gate-dielectric film on the crystalline active semiconductor film to form a doped-semiconductor top gate electrode of the transistor which is interconnected with the bottom one of the P and N electrode regions of the PIN diode.
7. The method of claim 6 , wherein the PIN diode is formed on the gate-dielectric film on the crystalline active semiconductor film of the transistor.
8. The method of claim 6 , wherein the electronic device comprises first and second crystalline thin-film transistors integrated with the PIN diode by the interconnection film, and wherein the interconnection film provides the bottom one of the P and N electrode regions of the PIN diode, the top gate electrode of the first transistor, and/or the source and drain regions of the second transistor.
9. The method of claim 1 , wherein the interconnection film comprises metal which provides the etch-stop film, and the diode has a vertical PIN diode structure formed in its active semiconductor film as an intrinsic region between P and N electrode regions.
10. The method of claim 1 , wherein the crystalline semiconductor film is subjected to a hydrogenation process.
11. The method of claim 1 , wherein the crystalline semiconductor film is formed by crystallising a deposited semiconductor film using laser heating of the film.
12. The method of claim 1 , wherein the doped source and drain regions are formed by an ion implant of dopant in the crystalline semiconductor film and by annealing the implanted dopant.
13. A method of manufacturing an electronic device comprising thin-film circuit elements that include a diode integrated, with a crystalline thin film transistor, the transistor having a channel area in an active semiconductor film that is more crystalline than an active semiconductor film of the diode, comprising:
forming on a circuit substrate the crystalline active semiconductor film of the transistor with a first process involving a first processing temperature;
forming doped source and drain regions of the transistor at ends of the channel area with a second process involving a second processing temperature;
providing an interconnection film between an electrode area of the transistor and a diode area over which the diode is to be formed, and providing an etch-stop film on which the active semiconductor film for the diode is to be deposited;
depositing the active semiconductor film for the diode over the interconnection film and the etch-stop film with a third process that involves a third processing temperature, the first and second processing temperatures being higher than the third-processing temperature; and
etching away the active semiconductor film for the diode from over the etch-stop film to leave the active semiconductor film for the diode over the interconnection film in the diode area;
wherein at least a portion of the interconnection film is provided on a gate-dielectric film on the crystalline active semiconductor film to form a top gate electrode of the transistor which is interconnected with a bottom one of the P and N electrode regions of the PIN diode.
14. The method of claim 13 , wherein the PIN diode is formed on the gate-dielectric film on the crystalline active semiconductor film of the transistor.
15. The method of claim 14 , wherein the electronic device comprises first and second crystalline thin-film transistors integrated with the PIN diode by the interconnection film, and wherein the interconnection film connects the bottom one of the P and N electrode regions of the PIN diode, the top gate electrode of the first transistor, and the source region of the second transistor.
16. The method of claim 13 , wherein the electronic device comprises first and second crystalline thin-film transistors integrated with the PIN diode by the interconnection film, and wherein the interconnection film connects the bottom one of the P and N electrode regions of the PIN diode, the top gate electrode of the first transistor, and the source region of the second transistor.
17. The method of claim 16 , wherein the electronic device comprises an active-matrix electroluminescent display with a light-emitting diode in each pixel, and wherein the light-emitting diode is driven via the first transistor as addressed via the second transistor.