Method of preparing a tin oxide layer
View Patent ↗Tin oxide having high mobility and a low electron concentration, and methods for producing layers of the tin oxide layers on a substrate by atmospheric pressure chemical vapor deposition (APCVD) are disclosed. The tin oxide may undoped polycrystalline n-type tin oxide or it may be doped polycrystalline p-type tin oxide. When the layer of tin oxide is formed on a crystalline substrate, substantially crystalline tin oxide is formed. Dopant precursors for producing doped p-type tin oxide are also disclosed.
1. A method for preparing a tin oxide layer on a substrate, the method comprising the step of:
depositing the tin oxide layer on the substrate by atmospheric pressure chemical vapor deposition using a tin oxide precursor in a carrier gas;
in which:
the tin oxide precursor comprises a vaporizable tin compound;
the tin oxide precursor comprises less about 0.01 weight percent total halides and less than about 0.01 weight percent total d and f transition metals;
the carrier gas comprises nitrogen, nitrous oxide, and oxygen; and
the flow rates are nitrogen, 2-20 L/min; nitrous oxide, 1-10 L/min; and oxygen, 20-160 cm 3 /min.
2. The method of claim 1 additionally comprising the step of annealing the tin oxide layer at a temperature greater than about 400 K and less than 700 K.
3. The method of claim 1 in which the tin oxide layer has the following electrical properties at room temperature:
a) a mobility of at least 50 cm 2 /Vs; and
b) an electron concentration of less than 1×10 18 cm −3 .
4. The method of claim 1 in which the flow rates are nitrogen, 3-16 L/min; nitrous oxide, 2-6 L/min; and oxygen, 40-120 cm 3 /min; and the carrier gas does not comprise a dopant precursor.
5. The method of claim 1 in which the flow rates are nitrogen, 4-10 L/min; nitrous oxide, 2-4 L/min; and oxygen, 50-100 cm 3 /min.
6. The method of claim 5 additionally comprising the step of annealing the tin oxide layer at a temperature greater than about 400 K and less than 700 K.
7. The method of claim 1 in which the substrate is borosilicate glass and the temperature of the substrate during the deposition step is about 600±20° C.
8. The method of claim 7 additionally comprising the step of annealing the tin oxide layer at a temperature greater than about 400 K and less than 700 K.
9. The method of claim 1 in which the substrate is a crystalline substrate.
10. The method of claim 9 in which the substrate is Si(100).
11. The method of claim 10 in which the tin oxide layer has a texture coefficient of at least about 0.99.
12. The method of claim 11 in which the tin oxide is undoped, n-type tin oxide.
13. The method of claim 10 in which the flow rates are nitrogen, 3-16 L/min; nitrous oxide, 2-6 L/min; and oxygen, 40-120 cm 3 /min; and the carrier gas does not comprise a dopant precursor.
14. The method of claim 10 in which the flow rates are nitrogen, 4-10 L/min;
nitrous oxide, 2-4 L/min; and oxygen, 50-100 cm 3 /min.
15. The method of claim 14 in which the tin oxide layer has a texture coefficient of at least about 0.99.
16. The method of claim 15 in which the tin oxide layer has a thickness of at least 300 nm.
17. The method of claim 10 additionally comprising the step of annealing the tin oxide layer at a temperature greater than about 400 K and less than 700 K.