Optimization of pyrolysis tube cracking efficiency

Patent metadata

Field	Value
Publication number	US-10719634-B2
Application number	US-201615147659-A
Country	US
Kind code	B2
Filing date	May 5, 2016
Priority date	May 5, 2015
Publication date	Jul 21, 2020
Grant date	Jul 21, 2020

Abstract

A method for optimizing a cracking efficiency with which a pyrolysis tube of a deposition apparatus cracks a precursor material into reactive species is disclosed, including measuring an input pressure at an entrance to the pyrolysis tube, outside of the pyrolysis tube; measuring an output pressure at an exit from the pyrolysis tube, outside of the pyrolysis tube; measuring a pyrolysis temperature within the pyrolysis tube; calculating a cracking efficiency based on the input pressure, the output pressure and the pyrolysis temperature; and determining an adjustment to be made to at least one of the input pressure, the output pressure and the pyrolysis temperature to increase the cracking efficiency.

First claim

What is claimed:

1. A method for optimizing a cracking efficiency with which a pyrolysis tube of a deposition apparatus cracks a precursor material into reactive species, comprising:
measuring an input pressure at an entrance to the pyrolysis tube, outside of the pyrolysis tube;
measuring an output pressure at an exit from the pyrolysis tube, outside of the pyrolysis tube;
measuring a pyrolysis temperature within the pyrolysis tube;
calculating a cracking efficiency based on the input pressure, the output pressure and the pyrolysis temperature;
determining an adjustment to be made to at least one of the input pressure, the output pressure and the pyrolysis temperature to increase the cracking efficiency; and
cracking the precursor material into the reactive species at the adjusted input pressure, the adjusted output pressure, or the adjusted pyrolysis temperature.

2. The method of claim 1 , further comprising:
adjusting at least one of the input pressure, the output pressure, the pyrolysis temperature in accordance with the adjustment to be made to increase the cracking efficiency.

3. The method of claim 1 , further comprising:
measuring a vaporization temperature at the entrance to the pyrolysis tube, outside of the pyrolysis tube;
wherein calculating a cracking efficiency comprises calculating the cracking efficiency based on the input pressure, the output pressure, the vaporization temperature and the pyrolysis temperature.

4. The method of claim 1 , further comprising:
determining a pressure differential between the input pressure and the output pressure.

5. The method of claim 4 , further comprising:
calculating a residence time that the precursor material remains within the pyrolysis tube with the pressure differential.

6. The method of claim 5 , wherein calculating the residence time comprises employing the following formula:
Δ t=t 0 ( P 1 −P 2 ) −β ,

where Δt is the residence time, (P 1 −P 2 ) is pressure differential between the input pressure and the output pre, t 0 is an experimentally determined pre-factor for the residence time and corresponds specifically to the pyrolysis tube and β is an experimentally determined exponent that corresponds specifically to the pyrolysis tube.

7. The method of claim 6 , wherein calculating the cracking efficiency comprises employing the following formula:
η=1− e −Δt ,

where η is cracking efficiency, e is Euler's number and λ is a reaction rate at which molecules of the precursor material are cracked into reactive species.

8. The method of claim 5 , wherein the residence time is at least as great as a predetermined minimum threshold residence time.

9. The method of claim 8 , wherein the residence time that is at least 0.1 second.

10. The method of claim 1 , wherein determining the adjustment to be made comprises identifying the adjusted pyrolysis temperature that does not exceed a predetermined maximum threshold pyrolysis temperature.

11. The method of claim 10 , wherein determining the adjustment to be made comprises identifying the pyrolysis temperature that does not exceed 680° C.

12. A method for determining a cracking efficiency of a pyrolysis tube of a material deposition apparatus, comprising:
determining a pyrolysis tube-dependent pre-factor for residence time; and
determining a pyrolysis tube-dependent exponential constant, wherein determining the pyrolysis tube-dependent exponential constant comprises experimentally determining the pyrolysis tube-dependent exponential constant,
wherein experimentally determining the pyrolysis tube-dependent exponential constant and determining the pyrolysis tube-dependent pre-factor for residence time comprise:
determining residence time of a plurality of different precursor material load amounts in the pyrolysis tube;
determining a logarithm of the residence time corresponding to each precursor material load amount of the plurality of precursor material load amounts;
determining a pressure drop within the pyrolysis tube corresponding to each precursor material load amount of the plurality of precursor material load amounts;
determining a logarithm of the pressure drop within the pyrolysis tube corresponding to each precursor material load amount;
plotting a data point for each precursor material load amount, the data point including a plot of the logarithm of the residence time corresponding to the precursor material load amount against the logarithm of the pressure drop within the pyrolysis tube corresponding to the precursor material load amount;
identifying a best-fit line through a plurality of data points corresponding to the plurality of precursor material load amounts; and
setting an equation for the best-fit line equal to Δt=t 0 (P 1 −P 2 ) −β , where P 1 −P 2 is the pressure drop within the pyrolysis tube, t 0 is the pyrolysis tube-dependent pre-factor for residence time and β is the pyrolysis tube-dependent exponential constant.

13. A method for optimizing a cracking efficiency of a pyrolysis tube of a material deposition apparatus, comprising:
determining at least one of a residence time and a pyrolysis temperature that provide a desired cracking efficiency for a pyrolysis tube having a specified pre-factor for residence time and a specified exponential constant; and
operating the pyrolysis tube in a predetermined manner that enables a precursor material to be heated to a predetermined pyrolysis temperature and/or that enables the precursor material to remain within the pyrolysis tube for a predetermined residence time.

14. The method of claim 13 , wherein determining at least one of the residence time and the pyrolysis temperature comprises use of the equation:
η=1− e −λΔt,

where η is the cracking efficiency, λ is a reaction rate, and is based in part on the pyrolysis temperature, and Δt is the residence time.

15. The method of claim 14 , wherein determining at least one of the residence time and the pyrolysis temperature further comprises use of the equation:
λ=4ρπ d 2 ( P 1 /kT v )(√(8 Kt p /πμ))( e (−Ea/kTp) ),

where T p is the pyrolysis temperature, ρ is a steric factor, d is an equivalent diameter for a molecule of precursor material, k is the Boltzmann constant, μ is a reduced mass of the precursor material and a monomer formed therefrom, E a is an activation energy for the precursor material and P 1 is a pressure at a first end of the pyrolysis tube.

16. The method of claim 14 , wherein determining at least one of the residence time and the pyrolysis temperature further comprises use of the equation:
Δ t=t 0 ( P 1 −P 2 ) −β ,

where P 1 −P 2 is the pressure drop within the pyrolysis tube, t 0 is the pyrolysis tube-dependent pre-factor for residence time and β is the pyrolysis tube-dependent exponential constant.

Assignees

• Hzo Inc

Inventors

• Su Tining
• Yun Yang

Classifications

• G06F2111/10

  Numerical modelling · CPC title

• G06F30/00 Primary

  Computer-aided design [CAD] · CPC title

• G06F30/20 Primary

  Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30) · CPC title

• C10G9/20 Primary

  Tube furnaces · CPC title