Pyrolytic boron nitride crucible and method
View Patent ↗A method of forming a pyrolytic boron nitride (PBN) article and an article having layers of PBN separated by layers of PBN having a dopant of sufficient concentration to induce peeling, the steps of introducing vapors of ammonia and a gaseous boron halide in a suitable ratio into a heated furnace reactor to cause boron nitride to be deposited in layers on a substrate, with at least one gaseous dopant injected into furnace at controlled periodic interval(s) such that at least two selected layers of boron nitride are doped with said gaseous dopant(s) at a minimum average concentration of 0.1 atomic wt % at a depth ranging from 1000 to 2000 angstroms in each selected layer, and with the selected layers spaced apart about 0.1 micron to 100 microns.
1. An article for use in the production of semiconductors, the article comprising
a first plurality of layers containing pyrolytic boron nitride (PBN) and
a second plurality of layers containing PBN and at least one elemental dopant selected from the group of elements in groups 1–6 of the periodic table of elements, alkali metal(s), alkaline earth metal(s), transition metal(s) and rare earth metal(s) or combinations thereof, wherein said second plurality of layers separating some or all of the first plurality of layers, wherein the dopant in the second plurality of layers being present in a sufficient concentration to induce peeling upon a build up of internal stress along a fracture plane in at least one of the second plurality of layers,
and wherein said dopant being present on both sides of the fracture plane.
2. The article of claim 1 , wherein said dopant is present in a concentration of at least 0.1 atomic weight % at a depth ranging from about 1000 to 2000 angstroms measured from the surface of the peeled layer.
3. The article of claim 2 , wherein each of the layers in the second plurality of layers being spaced apart from one another a distance of at least one tenth of one micron.
4. The article of claim 3 , wherein said dopant is present in a concentration of at least 0.5 atomic weight % at a depth ranging from about 1000 to 2000 angstroms measured from the surface of the peeled layer.
5. The article of claim 3 , wherein said dopant is present in a concentration of at least 1 atomic weight % at a depth ranging from about 1000 to 2000 angstroms measured from the surface of the peeled layer.
6. An article as defined in claim 1 , wherein a maximum concentration of dopant is present on both sides of the fracture plane to a depth of 2000 angstroms.
7. An article as defined in claim 1 , wherein each of the second plurality of the layers are separated a distance of about 0.1 micron to 100 microns.
8. An article as defined in claim 1 , wherein the second plurality of layers are thinner than the first plurality of layers.
9. An article as defined in claim 8 , in which the planes along which peeling occur are substantially parallel to one another.
10. An article as defined in claim 9 , wherein the dopant is selected from the group consisting of carbon, oxygen, and mixtures thereof.
11. An article as defined in claim 10 , wherein the dopants are carbon and oxygen and wherein the total average dopant concentration for both C and O is at least 0.2 atomic wt % within a distance of 1000 to 2000 angstroms from each peeled surface.
12. An article as defined in claim 11 , wherein the total average dopant concentration for both C and O is at least 0.5 atomic wt % within a distance of 1000 to 2000 angstroms from each peeled surface.
13. An article as defined in claim 12 , wherein the total average dopant concentration for both C and O is at least 1 atomic wt % within a distance of 1000 to 2000 angstroms from each peeled surface.
14. An article as defined in claim 1 , wherein the median peel strength of each is in the range of 2–5 N/mm.
15. An article as defined in claim 1 , wherein said first plurality of layers further comprises at least one additional component selected from the group consisting of: Si3N4, SiC, AIN, TiN, C, boron carbide, boron carbonitride, boron oxycarbide, and combinations thereof.
16. An article as defined in claim 15 , wherein the at least one additional component shows a gradient in composition along the direction of deposition such that concentration of at least one additional component will vary in excess of 0.1%.
17. A method of forming a pyrolytic boron nitride article, said method comprising the steps of
introducing vapors of ammonia and a gaseous boron halide in a suitable ratio into a heated furnace reactor to cause boron nitride to be deposited in layers on a substrate, injecting at least one gaseous dopant into the furnace at controlled periodic interval(s) such that at least two selected layers of boron nitride are doped with said gaseous dopant to at least a minimum concentration of 0.1 atomic wt % at a depth ranging from 1000 to 2000 angstroms in each selected layer,
controlling the interval of injection to space the selected layers from about 0.1 micron to 100 microns apart and
separating the article from the substrate such that upon the application of stress in a direction substantially normal to the plane of deposition for the boron nitride layers peeling will be induced to occur in a doped layer along a fracture plane in which dopant is present on both sides of the fracture plane.
18. A method according to claim 17 , in which the flow rates of ammonia and gaseous boron halide are altered during the dopant introduction.
19. A method according to claim 17 , in which the gaseous dopant is injected into the furnace at controlled interval(s) such that the at least two selected layers of boron nitride are doped with said gaseous dopant to at least a minimum concentration of 0.5 atomic wt %.
20. A method according to claim 17 , wherein a maximum concentration of dopant is present on both sides of the fracture plane to a depth of 2000 angstroms.
21. An article for use in the production of semiconductors, the article comprising
layers of pyrolytic boron nitride (PBN) separated by layers of PBN doped with one or more elements selected from Group 1–6 of the periodic table, transition metals, rare earth metals, or combinations thereof
wherein the dopant is present in each of the doped layers at amount of at least 0.12 atomic weight % at a depth ranging from about 1000–2000 angstroms measured from the surface of a peeled layer to induce peeling in each of the doped layers in a given sequence upon a build up of internal stress along a fracture plane in the peeled layer; and
wherein the dopant is present on both sides of the fracture plane and with each of the doped layers being spaced at least one tenth of one micron apart.
22. An article as defined in claim 21 , wherein the doped layers are separated by about 0.1 micron to 100 microns.
23. An article as defined in claim 21 , wherein the doped layers are thinner by a factor of 2 to 100,000 relative to the thickness of other PBN layer.
24. An article as defined in claim 21 , wherein the planes along which peeling occur are substantially parallel to one another.
25. An article as defined in claim 21 , wherein the dopant is selected from the group consisting of carbon, oxygen, and mixtures thereof.
26. An article as defined in claim 25 , wherein the total average dopant concentration for both C and O is at least 0.1 atomic wt % at a depth ranging from about 1000–2000 angstroms measured from the surface of a peeled layer.
27. An article as defined in claim 25 , wherein the total average dopant concentration for both C and O is at least 0.5 atomic wt % at a depth ranging from about 1000–2000 angstroms measured from the surface of a peeled layer.
28. An article as defined in claim 21 , wherein the median peel strength of each selected layer is above 2 N/mm.
29. An article as defined in claim 21 , wherein a maximum concentration of dopant is present on both sides of the fracture plane to a depth of 2000 angstroms.
30. An article comprises
layers of pyrolytic boron nitride (PBN) separated by layers of PBN doped with one or more elements selected from Group 1–6 of the periodic table, transition metals, rare earth metals and combinations thereof,
wherein the dopant is present in a concentration of at least 0.1 atomic weight % at a depth ranging about 1000–2000 angstroms measured from the peeled layer,
wherein the thickness of the doped layers being varied relative to one another and being spaced at least one tenth of one micron apart to cause peeling of the doped layers to occur in a given sequence upon a build up of internal stress along a fracture plane in each peeled layer, and wherein the dopant is present on both sides of the fracture plane.
31. An article as defined in claim 30 , wherein the doped layers are separated by about 0.1 micron to 100 microns.
32. An article as defined in claim 30 , wherein the doped layers are thinner by a factor of 2 to 100,000 relative to that of the other PBN layers.
33. An article as defined in claim 30 , in which the planes along which peeling occur are substantially parallel to one another.
34. An article as defined in claim 30 , wherein the dopant is selected from the group consisting of carbon, oxygen, and mixtures thereof.
35. An article as defined in claim 34 , wherein the total average dopant concentration for both C and O is at least 0.5 atomic wt % at a depth ranging about 1000–2000 angstroms measured from the peeled layer.
36. An article as defined in claim 30 , wherein the median peel strength of each selected layer is in the range of 2–5 N/mm.
37. An article as defined in claim 30 , wherein a maximum concentration of dopant is present on both sides of the fracture plane to a depth of 2000 angstroms.