Silicon single crystal doped with gallium, indium, or aluminum
View Patent ↗A doped silicon single crystal having a resistivity variation along a longitudinal and/or radial axis of less than 10% and a method of preparing one or a sequential series of doped silicon crystals is disclosed. The method includes providing a melt material comprising silicon into a continuous Czochralski crystal growth apparatus, delivering a dopant, such as gallium, indium, or aluminum, to the melt material, providing a seed crystal into the melt material when the melt material is in molten form, and growing a doped silicon single crystal by withdrawing the seed crystal from the melt material. Additional melt material is provided to the apparatus during the growing step. A doping model for calculating the amount of dopant to be delivered into the melt material during one or more doping events, methods for delivering the dopant, and vessels and containers used to deliver the dopant are also disclosed.
1. A method of preparing at least one doped silicon single crystal comprising the steps of:
a) providing a melt material comprising silicon into a continuous Czochralski crystal growth apparatus;
b) delivering a dopant to said melt material, wherein the dopant is gallium, indium, or aluminum;
c) providing a seed crystal into said melt material, wherein said melt material is in molten form; and
d) growing a doped silicon single crystal by withdrawing said seed crystal from said melt material, wherein additional melt material is provided to the crystal growth apparatus during the growing step,
wherein a model is employed to predict dopant concentration within the melt material in an inner growth chamber of the crystal growth apparatus, wherein said model predicts an amount of evaporation of said dopant from the melt material over time.
2. The method of claim 1 , wherein the method comprises sequentially preparing a series of doped silicon single crystals and wherein said delivering step comprises delivering said dopant into the melt material via one or more doping events.
3. The method of claim 2 , wherein the frequency of said doping events is determined in part by calculating the amount of said dopant that has evaporated during the growing step.
4. The method of claim 3 , wherein said one or more doping events comprises adding said dopant to an inner growth chamber of the crystal growth apparatus at intervals between successive crystal growth.
5. The method of claim 3 , wherein said one or more doping events comprises adding said dopant to an outer melt chamber of a crystal growth apparatus during the growing step.
6. The method of claim 1 , wherein said doped silicon single crystal has a resistivity variation along a longitudinal axis of less than 5%.
7. The method of claim 6 , wherein said doped silicon single crystal has an interstitial oxygen level of less than 25 parts per million atoms.
8. The method of claim 1 , wherein said doped silicon single crystal has a resistivity variation along a longitudinal axis of less than 2%.
9. The method of claim 8 , wherein said doped silicon single crystal has an interstitial oxygen level of less than 25 parts per million atoms.
10. The method of claim 1 , wherein said doped silicon single crystal has a resistivity variation along a radial axis of less than 5%.
11. The method of claim 10 , wherein said doped silicon single crystal has an interstitial oxygen level of less than 25 parts per million atoms.
12. The method of claim 1 , wherein said doped silicon single crystal has a resistivity variation along a radial axis of less than 2%.
13. The method of claim 12 , wherein said doped silicon single crystal has an interstitial oxygen level of less than 25 parts per million atoms.
14. The method of claim 1 , wherein said dopant is a dopant/silicon alloy.
15. The method of claim 2 , wherein said one or more doping events comprises providing a silicon vessel, adding said dopant to said silicon vessel, and delivering said silicon vessel filled with said dopant to said melt material in an inner growth chamber of the crystal growth apparatus.
16. The method of claim 15 , wherein providing a silicon vessel comprises growing a silicon vessel on said seed crystal using melt material in said inner growth chamber.
17. The method of claim 16 , wherein providing a silicon vessel comprises pre-manufacturing a silicon vessel and mounting said vessel to said seed crystal.
18. The method of claim 17 , wherein said silicon vessel is a plate having a well into which said dopant is added.
19. The method of claim 18 , wherein said silicon vessel is mounted to said seed crystal via a friction fit.
20. The method of claim 2 , wherein said one or more doping events comprises providing a silicon cube to an outer melt chamber of a crystal growth apparatus during the growing step, wherein said cube defines a center, threaded cavity with an amount of dopant contained therein and further comprises a threaded plug configured to be secured in a portion of said threaded cavity.
21. The method of claim 2 , wherein said one or more doping events comprises providing a dopant alloy cube to an outer melt chamber of a crystal growth apparatus during the growing step.
22. The method of claim 2 , wherein said doping events occur prior to growing each doped silicon single crystal in said series.
23. The method of claim 2 , wherein said doping events occur during growth of each doped silicon single crystal in said series.