Method for modifying and controlling the threshold voltage of thin film transistors
View Patent ↗Doped semiconductor ink formulations, methods of making doped semiconductor ink formulations, methods of coating or printing thin films, methods of forming electronic devices and/or structures from the thin films, and methods for modifying and controlling the threshold voltage of a thin film transistor using the films are disclosed. A desired dopant may be added to an ink formulation comprising a Group IVA compound and a solvent, and then the ink may be printed on a substrate to form thin films and conductive structures/devices, such as thin film transistors. By adding a customized amount of the dopant to the ink prior to printing, the threshold voltage of a thin film transistor made from the doped semiconductor ink may be independently controlled upon activation of the dopant.
1. An ink formulation comprising:
a) a silane, germane, and/or silagermane compound containing at least five Si and/or Ge atoms;
b) a dopant and/or dopant precursor in an initial concentration of from 0.001 M to 0.1 M and in an amount effective to (i) provide a film made from the silane, germane, and/or silagermane compound with a dopant atom concentration of from 1 to 10 ppm relative to the number of Si and Ge atoms and (ii) control a threshold voltage of a thin film transistor including the film, wherein the dopant and/or dopant precursor has the formula PR 3 , BR 3 or B 2 R 6 , where each R is independently selected from the group consisting of C 1 -C 10 alkyl, C 6 -C 10 aryl, C 6 -C 10 aryl substituted with 1 to 3 C 1 -C 4 alkyl groups, C 7 -C 12 aralkyl, hydrogen, SiR′ 3 and Si x H 2x+1 , where R′ is independently hydrogen, C 6 -C 10 aryl, C 6 -C 10 aryl substituted with 1 to 3 C 1 -C 4 alkyl groups, or Si x H 2x+1 , and x is an integer of from 1 to 4, such that the combined R and R′ groups include at least from 6 to 18 carbon atoms per phosphorous or boron atom and the dopant and/or dopant precursor has a boiling point of >150° C.; and
c) a solvent selected from the group consisting of linear alkanes, cycloalkanes, arenes, fluoroalkanes and siloxanes, wherein the dopant and/or dopant precursor is soluble in the ink formulation.
2. The formulation of claim 1 , wherein the Group IVA compound comprises a polysilane having at least 15 Si and/or Ge atoms.
3. The formulation of claim 1 , wherein the dopant has the formula PR 3 , BR 3 or B 2 R 6 , where each R is independently selected from the group consisting of C 1 -C 6 alkyl, C 6 -C 10 aryl, C 6 -C 10 aryl substituted with 1 to 3 C 1 -C 4 alkyl groups, SiR′ 3 and Si x H 2x+1 , where R′ is independently hydrogen, C 6 -C 10 aryl, C 6 -C 10 aryl substituted with 1 to 3 C 1 -C 4 alkyl groups, or Si x H 2x+1 , and x is an integer of from 1 to 4.
4. The formulation of claim 1 , wherein the dopant is present in an amount sufficient to provide a film with a dopant atom concentration of from 1 to 5 ppm, relative to the number of Si and Ge atoms.
5. The formulation of claim 1 , wherein the silane, germane, and/or silagermane compound is present in an amount of from about 0.1 to 50 wt. % of the formulation.
6. The formulation of claim 1 , wherein the solvent is selected from the group consisting of C 5 -C 12 cycloalkanes and C 6 -C 10 arenes.
7. The formulation of claim 1 , wherein said silane, germane, and/or silagermane compound consists essentially of (1) silicon and/or germanium and (2) hydrogen.
8. The formulation of claim 7 , wherein said silane, germane, and/or silagermane compound consists essentially of (1) silicon and (2) hydrogen.
9. The formulation of claim 1 , wherein said silane, germane, and/or silagermane compound is present in an amount of from about 1 to 20 wt. % of the formulation.
10. The formulation of claim 1 , wherein the dopant has the formula PR 3 or BR 3 , where each R is independently selected from the group consisting of C 1 -C 10 alkyl and C 6 -C 10 aryl, such that the combined R groups include from 6 to 18 carbon atoms per phosphorous or boron atom.
11. A method of making a doped silane ink, comprising:
a) combining a silane, germane, and/or silagermane compound containing at least five Si and/or Ge atoms, a dopant in an initial concentration of from 0.001 M to 0.1 M and in an amount effective to provide a film made from the silane, germane, and/or silagermane compound with a dopant atom concentration of from 1 to 10 ppm relative to the number of Si and Ge atoms, and a solvent, wherein the solvent is selected from the group consisting of linear alkanes, cycloalkanes, arenes, fluoroalkanes and siloxanes, and the dopant and/or dopant precursor (i) is soluble in the combined silane, germane, and/or silagermane compound and the solvent and (ii) has the formula PR 3 , BR 3 or B 2 R 6 , where each R is independently selected from the group consisting of C 1 -C 10 alkyl, C 6 -C 10 aryl, C 6 -C 10 aryl substituted with 1 to 3 C 1 -C 4 alkyl groups, C 7 -C 12 aralkyl, hydrogen, SiR′ 3 and Si x H 2x+1 , where R′ is independently hydrogen, C 6 -C 10 aryl, C 6 -C 10 aryl substituted with 1 to 3 C 1 -C 4 alkyl groups, or Si x H 2x+1 , and x is an integer of from 1 to 4, such that the combined R and R′ groups include from 6 to 18 carbon atoms per phosphorous or boron atom and the dopant and/or dopant precursor has a boiling point of >150° C.; and
b) mixing the silane, dopant, and solvent to form a solution.
12. The method of claim 11 , wherein the silane, germane, and/or silagermane compound comprises a polysilane having at least 15 Si and/or Ge atoms.
13. The method of claim 11 , wherein the silane, germane, and/or silagermane compound is present in an amount of from about 0.1 to about 50 wt. % of the formulation.
14. The method of claim 11 , where each R is independently selected from the group consisting of C 1 -C 10 alkyl, C 6 -C 10 aryl, C 6 -C 10 aryl substituted with 1 to 3 C 1 -C 4 alkyl groups, C 7 -C 12 aralkyl, and Si x H 2x+1 , where x is an integer of from 1 to 4.
15. The method of claim 11 , wherein the dopant is present in an amount sufficient to provide a film with a dopant atom concentration of from 1 to 5 ppm, relative to the number of Si and Ge atoms.
16. The method of claim 11 , wherein the solvent is selected from the group consisting of C 5 -C 12 cycloalkanes and C 6 -C 10 arenes.
17. The method of claim 11 , wherein said silane, germane, and/or silagermane compound consists essentially of (1) silicon and/or germanium and (2) hydrogen.
18. The method of claim 17 , wherein said silane, germane, and/or silagermane compound consists essentially of (1) silicon and (2) hydrogen.
19. The method of claim 11 , wherein said silane, germane, and/or silagermane compound is present in an amount of from about 1 to 20 wt. % of the formulation.
20. The method of claim 11 , wherein the dopant has the formula PR 3 or BR 3 , where each R is independently selected from the group consisting of C 1 -C 10 alkyl and C 6 -C 10 aryl, such that the combined R groups include from 6 to 18 carbon atoms per phosphorous or boron atom.