U.S. patent application number 10/288743 was filed with the patent office on 2004-05-06 for vapor delivery system for solid precursors and method of using same.
Invention is credited to Baum, Thomas H., Wang, Luping, Xu, Chongying.
Application Number | 20040083965 10/288743 |
Document ID | / |
Family ID | 32175962 |
Filed Date | 2004-05-06 |
United States Patent
Application |
20040083965 |
Kind Code |
A1 |
Wang, Luping ; et
al. |
May 6, 2004 |
VAPOR DELIVERY SYSTEM FOR SOLID PRECURSORS AND METHOD OF USING
SAME
Abstract
A vaporizer delivery system including a sublimatable solid
precursor material applied to a wire substrate for vaporizing and
achieving a continuous uninterrupted delivery of a vaporized
precursor to a downstream semiconductor process chamber. The coated
wire substrate is drawn past a heat source at a predetermined speed
to rapidly heat and vaporize the sublimatable solid precursor.
Inventors: |
Wang, Luping; (Brookfield,
CT) ; Baum, Thomas H.; (New Fairfield, CT) ;
Xu, Chongying; (New Milford, CT) |
Correspondence
Address: |
ATMI, INC.
7 COMMERCE DRIVE
DANBURY
CT
06810
US
|
Family ID: |
32175962 |
Appl. No.: |
10/288743 |
Filed: |
November 6, 2002 |
Current U.S.
Class: |
118/715 ;
118/729; 257/E21.17; 392/388; 438/680; 438/681; 438/785 |
Current CPC
Class: |
H01L 21/28556 20130101;
B01D 3/346 20130101; C23C 16/4481 20130101 |
Class at
Publication: |
118/715 ;
438/680; 118/729; 392/388; 438/681; 438/785 |
International
Class: |
B01D 007/00; C23C
014/00; H01L 021/44; C23C 016/00; H01L 021/31; H01L 021/469 |
Claims
What is claimed is:
1. A vapor delivery system for vaporization and delivery of a
precursor, comprising: a) a sealable housing comprising an internal
chamber; b) a gas inlet port in fluid communication with the
internal chamber for introducing a carrier gas; c) a first
rotatable spool positioned adjacent to the housing; d) a wire
coated with a sublimatable solid precursor material having one end
connected to first rotatable spool and spooled thereon; e) a
heating means communicatively connected to the internal chamber to
heat at least a portion of the internal chamber thereby providing a
heated area at the sublimation temperature of the sublimatable
solid precursor material; f) at least one drive mechanism for
unspooling and moving the coated wire through the heated area
wherein the sublimatable solid precursor material is vaporized
forming a precursor gas and a substantially uncoated wire; and g) a
gas outlet port for passage of the precursor gas from the internal
chamber to a downstream processing unit.
2. The vapor delivery system according to claim 1 further
comprising a second rotatable spool for spooling of the uncoated
wire, wherein the second rotatable spool is connected to the drive
mechanism and positioned a distance from the first rotatable spool
and adjacent to the housing.
3. The vapor delivery system according to claim 2, wherein the
first and second rotatable spool are positioned on the longitudinal
axis of the housing.
4. The vapor delivery system according to claim 1, wherein the
sublimatable solid precursor is selected from the group consisting
of: elemental boron, copper and phosphorus; decaborane; gallium
halides, indium halides, antimony halides, arsenic halides, gallium
halides, aluminum iodide, titanium iodide;
cyclopentadienylcycloheptatrienyltitani- um, (C.sub.pTiCht);
cyclooctatetraenecyclopentadienyltitanium;
biscyclopentadienyltitaniumdiazide; In(CH.sub.3).sub.2(hfac);
dibromomethylstibine; and tungsten carbonyl.
5. The vapor delivery system according to claim 1, wherein the
sublimatable solid precursor is selected from the group consisting
of: metalorganic .beta.-diketonate complexes, metalorganic alkoxide
complexes, metalorganic carboxylate complexes, metalorganic aryl
complexes and metalorganic amido complexes.
6. The vapor delivery system according to claim 2, wherein the
first and second rotatable spool are positioned outside of the
housing.
7. The vapor delivery system according to claim 1, wherein the
sealable housing is fabricated of a heat conducting material.
8. The vapor delivery system according to claim 1, wherein the
first and second rotatable spool are connected to a drive
mechanism.
9. The vapor delivery system according to claim 1, wherein the
rotatable spool comprises multiple windings of the coated wire.
10. The vapor delivery system according to claim 1, wherein the
coated wire is of a length greater than the longitudinal axis of
the housing.
11. The vapor delivery system according to claim 2, further
comprising at least two sealable air locks positioned on the
longitudinal axis of the housing for moving of the coated wire from
the first rotatable spool through the internal chamber to the
second rotatable spool.
12. The vapor delivery system according to claim 2, further
comprising a pair of electrodes positioned within the internal
chamber on the longitudinal axis of the housing.
13. The vapor delivery system according to claim 12, wherein the
coated wire comprise a core wire fabricated of an electrically
conductive material.
14. The vapor delivery system according to claim 13, wherein the
coated wire contacts the pair of electrodes.
15. A vaporizer delivery system, comprising: a) a sealable housing
comprising an internal chamber; b) a gas inlet and gas outlet in
fluid communication with the internal chamber; c) at least one
rotatable spool positioned within the internal chamber for holding
a wire coated with a sublimatable solid source material; d) a
heating means communicatively connected to at least a portion of
the housing to provide a heated area within the internal chamber at
the sublimation temperature of the solid source material; and e) a
drive mechanism for moving the coated wire from the rotatable spool
through the heated area.
16. The vapor delivery system according to claim 15, further
comprising a second rotatable spool for spooling of the uncoated
wire, wherein the second rotatable spool is connected to the drive
mechanism and positioned outside the internal chamber.
17. The vapor delivery system according to claim 16, wherein the
first and second rotatable spool are positioned on the longitudinal
axis of the housing.
18. The vapor delivery system according to claim 15, wherein the
sublimatable solid precursor is selected from the group consisting
of: elemental boron, copper and phosphorus; decaborane; gallium
halides, indium halides, antimony halides, arsenic halides, gallium
halides, aluminum iodide, titanium iodide;
cyclopentadienylcycloheptatrienyltitani- um, (C.sub.pTiCht);
cyclooctatetraenecyclopentadienyltitanium;
biscyclopentadienyltitaniumdiazide; In(CH.sub.3).sub.2(hfac);
dibromomethylstibine; and tungsten carbonyl.
19. The vapor delivery system according to claim 15, wherein the
sublimatable solid precursor is selected from the group consisting
of: metalorganic .beta.-diketonate complexes, metalorganic alkoxide
complexes, metalorganic carboxylate complexes, metalorganic aryl
complexes and metalorganic amido complexes.
20. The vapor delivery system according to claim 15, wherein the
sealable housing is fabricated of a heat conducting material.
21. The vapor delivery system according to claim 15, wherein the
first and second rotatable spool are connected to a drive
mechanism.
22. The vapor delivery system according to claim 15, wherein the
first rotatable spool comprises multiple windings of the coated
wire.
23. The vapor delivery system according to claim 15, wherein the
coated wire is of a length greater than the longitudinal axis of
the housing.
24. The vapor delivery system according to claim 15, further
comprising a pair of electrodes positioned within the internal
chamber on the longitudinal axis of the housing.
25. The vapor delivery system according to claim 24, wherein the
coated wire comprises a core wire fabricated of an electrically
conductive material.
26. The vapor delivery system according to claim 25, wherein the
coated wire contacts the pair of electrodes.
27. The vapor delivery system according to claim 15, wherein the
heating means heats a heating area without direct contact of the
heating means to the coated substrate.
28. A vaporizer system comprising: a) a sealable vessel comprising
an internal chamber; b) a gas inlet and gas outlet in fluid
communication with the internal chamber; c) a conductive wire
coated with a sublimatable solid source material for introduction
into the internal chamber, wherein the conductive wire has a length
extending beyond the longitudinal axis of the sealable vessel; d)
at least one motorized mechanism positioned adjacent to the
sealable vessel for moving the conductive wire through the internal
chamber; e) a heating means for raising the temperature in the
internal chamber to the sublimation temperature of the sublimatable
solid source material; and f) a pair of electrodes positioned in
the internal chamber and contacting the conductive wire for passing
an electric heating current therethrough.
29. The vapor delivery system according to claim 28, wherein the
conductive wire coated with a sublimatable solid source material is
spooled on a first rotatable spool.
30. The vapor delivery system according to claim 28, wherein the
sublimatable solid precursor is is selected from the group
consisting of: elemental boron, copper and phosphorus; decaborane;
gallium halides, indium halides, antimony halides, arsenic halides,
gallium halides, aluminum iodide, titanium iodide;
cyclopentadienylcycloheptatrienyltitani- um, (C.sub.pTiCht);
cyclooctatetraenecyclopentadienyltitanium;
biscyclopentadienyltitaniumdiazide; In(CH.sub.3).sub.2(hfac);
dibromomethylstibine; and tungsten carbonyl.
31. The vapor delivery system according to claim 28, wherein the
sublimatable solid precursor is selected from the group consisting
of: metalorganic .beta.-diketonate complexes, metalorganic alkoxide
complexes, metalorganic carboxylate complexes, metalorganic aryl
complexes and metalorganic amido complexes.
32. The vapor delivery system according to claim 28, wherein the
sealable vessel is fabricated of a heat conducting material.
33. The vapor delivery system according to claim 28, wherein the
heating means is selected from the group consisting of strip
heaters, radiant heaters, circulating fluid heaters, resistant
heating systems, and inductive heating systems.
34. A method for vaporizing and delivering a solid source material
to a downstream semiconductor process chamber, comprising: a)
providing a metallic substrate coated with a sublimatable solid
precursor material; b) introducing the coated substrate into a
housing having an internal chamber; c) heating the internal chamber
to the sublimation temperature of the sublimatable solid precursor
material to form a precursor gas; and d) moving the coated
substrate through the internal chamber wherein the sublimatable
solid material coated on the metallic substrate is sublimated to
form a precursor gas and an uncoated metallic substrate; and e)
removing the precursor gas from the internal chamber and
transporting same to the downstream semiconductor process
chamber.
35. The method according to claim 34, further comprising the step
of passing an electric heating current through the coated substrate
that has a core wire fabricated of an electrically conductive
wire.
36. The method according to claim 34, wherein the coated substrate
is wound on a rotatable spool positioned adjacent to the
housing.
37. The method according to claim 36, wherein the moving of the
coated substrate through the internal chamber is moved by a drive
mechanism connected to the rotatable spool.
38. The method according to claim 34, wherein the sublimatable
solid precursor is selected from the group consisting of: elemental
boron, copper and phosphorus; decaborane; gallium halides, indium
halides, antimony halides, arsenic halides, gallium halides,
aluminum iodide, titanium iodide;
cyclopentadienylcycloheptatrienyltitanium, (C.sub.pTiCht);
cyclooctatetraenecyclopentadienyltitanium;
biscyclopentadienyltitaniumdiazide; In(CH.sub.3).sub.2(hfac);
dibromomethylstibine; and tungsten carbonyl.
39. The vapor delivery system according to claim 34, wherein the
sublimatable solid precursor is selected from the group consisting
of: metalorganic .beta.-diketonate complexes, metalorganic alkoxide
complexes, metalorganic carboxylate complexes, metalorganic aryl
complexes and metalorganic amido complexes.
40. The method according to claim 36, wherein the rotatable spool
comprises multiple windings of the coated substrate.
41. The method according to claim 34, wherein the heating of the
internal chamber is conducted by a heating selected from the group
consisting of strip heaters, radiant heaters, circulating fluid
heaters, resistant heating systems, and inductive heating
systems.
42. The method according to claim 34, further comprising moving the
uncoated substrate from the internal chamber.
43. A system for delivering a precursor vapor, said system
comprising: a) a solid precursor vaporization chamber; b) an
elongate support having a vaporizable solid precursor coated
thereon; c) means for (i) translating the elongate support having
the vaporizable solid precursor coated thereon through the chamber
so that a length of the elongate support having the vaporizable
solid precursor coated thereon is exposed for vaporization of said
vaporizable solid precursor in said chamber, and (ii) translating
out of the chamber the elongate support from which the solid
precursor has been vaporized; and d) means for heating the exposed
length of the elongate support having the vaporizable solid
precursor coated thereon in said chamber.
44. The system of claim 43, wherein the support comprises an
electrically resistively heatable element, and said heating means
comprise means for electrifying said electrically resistively
heatable element to a temperature for vaporizing said solid
precursor coated on the elongate support.
45. The system of claim 43, wherein the support comprises a
structure selected from the group consisting of screens, meshes,
webs, wires, fibers, multifilament ropes, chain structures, and
ribbons.
46. The system of claim 43, wherein the support comprises a wire
element.
47. The system of claim 46, wherein the means for (i) translating
the elongate support having the vaporizable solid precursor coated
thereon through the chamber so that a length of the elongate
support having the vaporizable solid precursor coated thereon is
exposed for vaporization of said vaporizable solid precursor in
said chamber, and (ii) translating out of the chamber the elongate
support from which the solid precursor has been vaporized, comprise
dispensing and uptake spools of said wire element arranged for
continuous feed of the wire element through said chamber, whereby
the dispensing spool of said wire element supplies wire element
coated with said vaporizable solid precursor to said chamber in a
continuous manner.
48. The system of claim 46, wherein the dispensing spool is
containerized in a cassette.
49. The system of claim 43, wherein the solid precursor
vaporization chamber is maintained under a vacuum.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a vaporizer, and more
particularly, to a vaporizer delivery system comprising a
sublimatable solid precursor material applied to a wire substrate
for vaporizing and achieving a continuous uninterrupted delivery of
a vaporized precursor to a downstream semiconductor process
chamber.
[0003] 2. Description of the Related Art
[0004] Chemical vapor deposition (CVD) has been extensively used
for preparation of films and coatings in semiconductor wafer
processing. CVD is a favored deposition process in many respects,
for example, because of its ability to provide highly conformable
and high quality films, at relatively fast processing times.
Further, CVD is beneficial in coating substrates of irregular
shapes including the provision of highly conformable films even
with respect to deep contacts and other openings.
[0005] In general, CVD techniques involve the delivery of gaseous
reactants to the surface of a substrate where chemical reactions
takes place under temperature and pressure conditions that are
favorable to the thermodynamics of the desired reaction. The type
and composition of the layers that can be formed using CVD is
limited by the ability to deliver the reactants or reactant
precursors to the surface of the substrate. Various liquid
reactants and precursors are successfully used in CVD applications
by delivering the liquid reactants in a carrier gas. In liquid
reactant CVD systems, the carrier gas is typically bubbled at a
controlled rate through a container of the liquid reactant so as to
saturate the carrier gas with liquid reactant, and the saturated
carrier then is transported to the reaction chamber.
[0006] Analogous attempts have been made to deliver solid reactants
to a CVD deposition chamber, but with much less success. The
delivery of solid precursors in CVD processing is carried out using
the sublimator/bubbler method in which the precursor typically is
placed in a sublimator/bubbler reservoir, which then is heated to
the sublimation temperature of the precursor to transform it into a
vapor for transport into the CVD reactor with a carrier gas such as
argon, or nitrogen. The carrier gas mixes with the vapor, and is
then transported to the deposition chamber.
[0007] However, this procedure has been unsuccessful in reliably
and reproducibly delivering a solid precursor to the reaction
chamber for a number of reasons. Initially, it is difficult to
ensure complete saturation of the fast flowing carrier gas stream
because of the limited amount of exposed surface area of the solid
precursor in the vaporizer system and need for uniform temperature
to provide maximum sublimation. This problem may be alleviated by
using large excesses of precursor material beyond the amount needed
for film growth. However, using an excess of material can result in
a substantial waste of precursor materials.
[0008] Further, it is difficult to vaporize a solid at a controlled
rate such that a reproducible flow of vaporized solid precursor can
be delivered to the process chamber. Lack of control of solid
precursor sublimation is, at least in part, due to the changing
surface area of the bulk solid precursor as it is vaporized. Such a
changing surface area when the bulk solid precursor is exposed to
sublimation temperatures produces a continuously changing rate of
vaporization, particularly for thermally sensitive compounds. This
ever-changing rate of vaporization results in a continuously
changing and non-reproducible flow of vaporized solid precursor for
deposition in the process chamber. As a result, processes using
such vaporized solid precursors cannot be controlled adequately and
effectively.
[0009] Accordingly, there is a need in the art for a vapor delivery
system for delivering solid precursors, particularly thermally
sensitive precursors, which efficiently vaporizes solid precursor
materials at a highly controllable and reproducible flow rate.
SUMMARY OF THE INVENTION
[0010] The present invention relates to a vaporizer system and
method for vaporizing solid precursor source materials having
particular utility for semiconductor manufacturing
applications.
[0011] In one aspect, the present invention relates to a vapor
delivery system for vaporization and delivery of a solid source
material that provides sufficient surface area of the solid source
material to meet the flow rates required for typical deposition
applications.
[0012] Accordingly, the present invention provides for a system for
delivering a precursor vapor, said system comprising:
[0013] a. a solid precursor vaporization chamber;
[0014] b. an elongate support having a vaporizable solid precursor
coated thereon:
[0015] c. means for
[0016] i) translating the elongate support having the vaporizable
solid precursor coated thereon through the chamber so that a length
of the elongate support having the vaporizable solid precursor
coated thereon is exposed for vaporization of said vaporizable
solid precursor in said chamber, and
[0017] ii) translating out of the chamber the elongate support from
which the solid precursor has been vaporized;
[0018] d. means for heating the exposed length of the elongate
support having the vaporizable solid precursor coated thereon in
said chamber; and
[0019] e. means for discharging precursor vapor from said
chamber.
[0020] In the present invention the elongated support may include,
but is not limited to, screens, meshes, webs, wires, fibers,
multifilament ropes, chain structures, and ribbons. The support may
further comprises an electrically resistively heatable element that
can be electrically heated to a temperature for vaporizing said
solid precursor coated on the elongate support. Preferably, the
elongated support is a wire element connected to a dispensing spool
arranged for continuous feed of the wire element through the
internal chamber. Further, the solid precursor depleted wire
element can be rewound on an uptake spool positioned adjacent to
the chamber.
[0021] In another aspect, the present invention relates to a vapor
delivery system for vaporization and delivery of a precursor,
comprising:
[0022] a. a sealable housing comprising an internal chamber;
[0023] b. a gas inlet port in fluid communication with the internal
chamber for introducing a carrier gas;
[0024] c. a first rotatable spool positioned adjacent to the
housing;
[0025] d. a wire coated with a sublimatable solid precursor
material having one end connected to first rotatable spool and
spooled thereon;
[0026] e. a heating means communicatively connected to the internal
chamber to heat at least a portion of the internal chamber thereby
providing a heated area at the sublimation temperature of the
sublimatable solid precursor material;
[0027] f. at least one drive mechanism for unspooling and moving
the coated wire through the heated area wherein the sublimatable
solid precursor material is vaporized forming a precursor gas and a
substantially uncoated wire; and
[0028] g. a gas outlet port for passage of the precursor gas from
the internal chamber to a downstream processing unit.
[0029] The delivery system may further comprise a second rotatable
spool for spooling of the uncoated wire, wherein the second
rotatable spool can be connected to the drive mechanism and
positioned a distance from the first rotatable spool and adjacent
to the housing.
[0030] Solid precursors useful in the present invention include but
are not limited to, elemental boron, copper and phosphorus;
decaborane; metal halides such as gallium halides, indium halides,
antimony halides, arsenic halides, gallium halides, aluminum
iodide, titanium iodide; metalorganic complexes, such as,
cyclopentadienylcycloheptatrienyltitaniu- m (C.sub.pTiCht),
cyclooctatetraenecyclopentadienyltitanium,
biscyclopentadienyltitanium-diazide, In(CH.sub.3).sub.2(hfac),
dibromomethyl stibine and tungsten carbonyl, as well as
metalorganic .beta.-diketonate complexes, metalorganic alkoxide
complexes, metalorganic carboxylate complexes, metalorganic aryl
complexes and metalorganic amido complexes.
[0031] Other solid precursor compositions useful in specific
applications of the instant invention are disclosed in the
following United States Patents, which are commonly owned by the
assignee of the present application and hereby incorporated herein
by reference in their entireties:
[0032] U.S. pat. application Ser. No. 09/414,133 in the names of,
Thomas H. Baum and Witold Paw, which was issued as U.S. Pat. No.
6,399,208 on Jun. 4, 2002;
[0033] U.S. pat. application Ser. No. 09/218,992 filed 22 Dec.
1998, in the names of, Chongying Xu and Thomas H. Baum, which was
issued as U.S. Pat. No. 6,204,402 on Mar. 20, 2001;
[0034] U.S. pat. application Ser. No. 08/960,915 filed 30 Oct.
1997, in the names of, Thomas H. Baum, et al., which was issued as
U.S. Pat. No. 5,859,274 on Jan. 12, 1999.
[0035] U.S. pat. application Ser. No. 08/307,316 filed 16 Sep. 1994
in the names of Peter S. Kirlin et al., which was issued as U.S.
Pat. No. 5,679,815 on Oct. 21, 1997; and
[0036] U.S. application Ser. No. 07/918,141 filed Jul. 22, 1992 in
the names of Peter S. Kirlin, et al., and issued as U.S. Pat. No.
5,453,494;
[0037] In yet another aspect, the present invention relates to a
vaporizer delivery system, comprising:
[0038] a. a sealable housing comprising an internal chamber;
[0039] b. a gas inlet and gas outlet in fluid communication with
the internal chamber;
[0040] c. at least one rotatable spool positioned within the
internal chamber for holding a wire coated with a sublimatable
solid source material;
[0041] d. a heating means communicatively connected to at least a
portion of the housing to provide a heated area within the internal
chamber at the sublimation temperature of the solid source
material;
[0042] e. a drive mechanism for moving the coated wire from the
rotatable spool through the heated area.
[0043] In still a further aspect, the present invention provides
for a vaporizer system comprising:
[0044] a. a sealable vessel comprising an internal chamber;
[0045] b. a gas inlet and gas outlet in fluid communication with
the internal chamber;
[0046] c. a conductive wire coated with a sublimatable solid source
material for introduction into the internal chamber, wherein the
conductive wire has a length extending beyond the longitudinal axis
of the sealable vessel;
[0047] d. at least one motorized mechanism positioned adjacent to
the sealable vessel for moving the conductive wire through the
internal chamber;
[0048] e. a heating means for raising the temperature in the
internal chamber to the sublimation temperature of the sublimatable
solid source material; and
[0049] f. a pair of electrodes positioned in the internal chamber
and contacting the conductive wire for passing an electric heating
current therethrough.
[0050] In yet another aspect, the present invention provides a
method for vaporizing and delivering a solid source material to a
downstream semiconductor process chamber, comprising:
[0051] a. providing a metallic substrate coated with a sublimatable
solid precursor material;
[0052] b. introducing the coated substrate into a housing having an
internal chamber;
[0053] c. heating the internal chamber to the sublimation
temperature of the sublimatable solid precursor material to form a
precursor gas; and
[0054] d. moving the coated substrate through the internal chamber
wherein the sublimatable solid material coated on the metallic
substrate is sublimated to form a precursor gas and an uncoated
metallic substrate; and
[0055] e. removing the precursor gas from the internal chamber and
transporting same to the downstream semiconductor process
chamber.
[0056] This embodiment further contemplates the step of passing an
electric heating current through the coated wire that has a core
wire fabricated of an electrically conductive core and coated with
a sublimatable solid precursor material.
[0057] Other aspects and features of the invention will be more
fully apparent from the ensuing disclosure and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] FIG. 1 is a schematic diagram of a sublimation system in
accordance with the present invention for subliming a solid
precursor from a coated metallic substrate coiled on a rotatable
spool for drawing through the sublimation system.
[0059] FIG. 2 is a cross-sectional view of a metallic substrate
coated with a sublimatable solid precursor material.
[0060] FIG. 3 is a schematic diagram of a sublimation system
illustrating a sublimator having a cone-shaped configuration
enclosing a rotatable spool having a coiled length of substrate
coated with a sublimatable solid precursor in accordance with one
embodiment of the present invention.
[0061] FIG. 4 is a schematic diagram of a sublimator system of the
present invention illustrating a concentrated heating area for
sublimation of a sublimatable solid precursor from a coated
metallic substrate.
[0062] FIGS. 5 and 6 are schematic diagrams of sublimators of the
present invention incorporating a containerize cassette including a
coiled wire coated with a sublimatable solid and different heating
devices that concentrate vaporization to a precise section of the
coated substrate.
DETAILED DESCRIPTION OF THE INVENTION, AND PREFERRED EMBODIMENTS
THEREOF
[0063] Generally, the vapor delivery system described herein
utilizes a sublimatable solid precursor material applied to a
metallic substrate, such as a wire. The coated substrate is drawn
through a heated internal chamber at a predetermined speed to
rapidly heat and vaporize the sublimatable solid precursor. The
vaporization continues until the desired amount of solid precursor
is vaporized. The vapor delivery system of the present invention
vaporizes a known amount of precursor and achieves continuous
uninterrupted delivery of the vaporized solid precursor to a
downstream process chamber in reproducible fashion. Further, the
present invention allows the user to vaporize sufficient quantities
of a solid precursor material to meet the flow rates required for
typical deposition applications.
[0064] One embodiment of the present invention is a vapor delivery
system described with reference to FIG. 1. The vaporizer delivery
system 10 comprises a housing 12, a sealable cover plate 14 that is
removably attached to the housing to form a sealed internal chamber
16. A gasket 24 seals the connection between the housing 12 and the
cover plate 14. The housing may be fabricated of a suitable
heat-conducting material, such as for example silver, silver
alloys, copper, copper alloys, aluminum, aluminum alloys, lead,
nickel clad, stainless steel, graphite and/or ceramic
materials.
[0065] The housing includes a gas inlet port 18 and gas outlet port
20 in fluid communication with the internal chamber. The gas inlet
port 18 is in fluid communication with a carrier gas supply 22. A
suitably valved manifold 26 may be connected to the inlet port for
controlling the flow rate and pressure of the carrier gas into the
internal chamber. The carrier gas may be an inert gas such as
argon, helium, nitrogen, neon, and etc.
[0066] The gas outlet port 20 is in fluid communication with the
internal chamber 16 and a semiconductor processing chamber 30. The
outlet port receives the precursor gas formed within the internal
chamber. It should be recognized that this embodiment can be
maintained under a vaccum to increase vaporization of the solid
material. A vacuum may be generated with the internal chamber by
either connection with the semiconductor processing chamber 30 or
outlet port 28 which may be connected to a separate vacuum source
(e.g. a turbo pump). Generally, the vacuum may be maintained from
about 100 torr to about 1.times.10.sup.-11 torr. Advantageously,
this embodiment limits vaporization of a solid precursor to only
that within the internal chamber. A suitably valved manifold 32 can
control gas flow of the precursor gas through the outlet port
20.
[0067] Traversing the internal chamber 16 is a length of coated
wire 34 having deposited thereon a sublimatable solid precursor
material. The coated wire is initially wound around a first
rotatable spool 36. The windings of the coated wire are unwound and
moved through the internal chamber during the vaporization process.
As shown in FIG. 2, the coated wire comprises a core wire 40 and an
outer coating of a sublimatable solid precursor 42. Preferably the
core wire is fabricated of a material that has a melting
temperature higher than the sublimation temperature of the
sublimatable solid precursor coated thereon. The wire may take on
any geometry, including but not limited to, circular, ovoid,
ellipsoidal, rectangular, square and polygonal cross-section. The
wire core material may include, but is not limited to, silver,
silver alloys, copper, copper alloys, aluminum, aluminum alloys,
lead, nickel clad, stainless steel, nickel alloys, graphite and/or
ceramic material. In the preferred embodiment of wire 34, the wire
core 40 is a metallic substrate having a diameter of approximately
fifty (50) to one hundred fifty (150) microns. Preferably the core
wire is fabricated from an electrically conductive metal to provide
the option of heating both the interior surface of the sublimatable
solid precursor that contacts the core wire and the exterior
surface of the sublimatable solid precursor exposed to the heated
internal chamber.
[0068] The sublimatable solid precursor layer 42 is fabricated from
any solid precursor applicable for use in a semiconductor process
system, including but not limited to, elemental boron, copper and
phosphorus; decaborane; metal halides such as gallium halides,
indium halides, antimony halides, arsenic halides, gallium halides,
aluminum iodide, titanium iodide; metalorganic complexes, such as,
cyclopentadienylcyclohe- ptatrienyltitanium (C.sub.pTiCht),
cyclooctatetraenecyclopentadienyltitani- um,
biscyclopentadienyltitanium-diazide, In(CH.sub.3).sub.2(hfac),
dibromomethyl stibine and tungsten carbonyl, as well as
metalorganic .beta.-diketonate complexes, metalorganic alkoxide
complexes, metalorganic carboxylate complexes, metalorganic aryl
complexes and metalorganic amido complexes. Preferably, this
coating has a width of approximately fifty (50) to one hundred
fifty (150) microns.
[0069] The solid precursor material is coated on the surface of the
core wire by any of various methods including the method of melting
the solid precursor material by heating, applying to the support
wire core and then cooling it. Additionally, the solid precursor
material may be dissolved in a solvent to form a solution, applying
the solution to the surface of the core wire and then removing the
solvent under reduced pressure. Alternatively, the wire can be
coated by sublimation of the solid precursor material and then
condensation of the solid precursor material on the surface of the
core wire. Each of the above processes for preparing the coated
wires may be repeated several times to achieve additional
thickness. The desired thickness may be utilized in controlling the
delivery rate of the vaporized solid precursor material to the
process chamber.
[0070] The first rotatable spool 36 is removably mounted adjacent
to the housing 12. Spool 36 can be replaced when additional
material is required. Wire 34 is wound on spool 36 in a juxtaposed
spooled configuration forming a plurality of overlapping coils.
Preferably, the winding of the wire on the spool is completed
before positioning the spool in working relation to the housing.
Notably, a relatively long length of wire 34 can be positioned on
the spool. Spool 36 can be made of any suitable material, e.g.,
steel, aluminum or any material that can withstand the elevated
temperatures that may occur during the vaporization process.
[0071] As the spool is rotated, successive portions of the wire are
drawn sequentially through the internal chamber and then wound
around a second rotatable spool 37. To draw or feed the wire
through the internal chamber, a free end of the wire is attached to
the second rotatable spool and at least the second rotatable spool
is rotated by a drive mechanism 39. The drive mechanism rotates a
shaft that the rotatable spool attaches thereto. The shaft is
rotated at a predetermined speed to move the second rotatable spool
at a rate that winds the depleted wire onto the spool and draws the
wire through the internal chamber wherein the sublimatable solid
precursor material is vaporized to form a precursor gas. As the
sequential lengths of coated wire are moved along the longitudinal
axis of the internal chamber a heating unit 38 vaporizes a
predetermined amount of solid precursor. The rate of the
vaporization and delivery of vaporized precursor gas to the process
chamber can be controlled by the speed of the rotating spool.
Further, as previously indicated, the thickness of the solid
precursor material on the core wire can also be varied to change
the flow rate. The uniformity of the solid precursor material on
the core wire provides for reproducibility of the process.
[0072] Housing 12 is heated to the desired sublimation temperature
by the heating means 38. The heating means can include any suitable
device which provides sufficient heat to cause the sublimatable
solid precursor to vaporize including, without limitation, strip
heaters; radiant heaters; circulating fluid heaters; resistant
heating systems; electromagnetic energy systems including
frequencies in the ranges of infrared, ultrasound, acoustic,
ultraviolet and etc.; inductive heating systems; etc., constructed
and arranged for controlled temperature operation. Preferably, the
heating means heats a heating area without the heating means
directly contacting with the coated substrate. The temperature of
the vaporizer is different dependent on the operating conditions of
the downstream semiconductor processing system, the vapor pressure,
type and amount of the source material. The temperature is
generally from about 250 to about 2000.degree. C., and more
preferably from about 400 to 1200.degree. C.
[0073] The present invention has been designed to sustain a
sublimation-direct transition from the solid state to the vapor
state. At a given temperature, the vapor pressure of a solid is the
partial pressure of that material at the interface, that is, there
are as many molecules condensing on the solid surface as the number
of molecules sublimating from the surface at a given time period.
Equilibrium is destroyed if the molecules in gaseous state is
removed from the solid/gas interface by the carrier gas. Clearly,
sublimation takes place at a higher rate to restore equilibrium if
there is enough heat supplied to the surface of the solid to make
up for the latent heat of sublimation.
[0074] To enhance the sublimation process the present invention
contemplates a second heating source that provides heating of the
solid source material by contacting the core wire with a heating
current that traverses the core wire. As can shown in FIG. 1, the
coated wire is guided by several feed rollers 33 and 35 that can
function as a pair of electrodes if the feed rollers are fabricated
of an electrically conductive material. Thus an electric heating
current can be used to heat a conductive core wire coated with a
solid precursor material. As current is introduced to the core
wire, the interface between the core wire and the solid precursor
material is heated thereby enhancing the vaporization of the solid
precursor material from within the coating. A source of direct
current has one of its positive terminal connected to feed roller
33 and the current passes longitudinally through the core wire into
feed roller 35 which is connected to the negative terminal. The
heating current can vary between 115 and 200 amps depending on the
speed of the moving wire and coating thickness of the solid
precursor material. This current flow causes the core wire to heat
thereby providing an increased and reproducible sublimation rate of
the solid precursor. It should be recognized that even though a
direct current source has been illustrated the inventors also
contemplate utilizing alternating current to cause heating of the
solid precursor surface contacting the conductive metallic
substrate.
[0075] The apparatus of the present invention further comprises
lines for supplying a carrier gas and for transferring a vaporized
gas, which are connected to the vaporizer, valves, adjusting valves
and instruments for measurements of pressure and temperature. The
apparatus further comprises heaters for maintaining the temperature
in the lines for supplying a carrier gas and for transferring a
vaporized gas from the apparatus for vaporizing and transferring a
material to a downstream semiconductor processing system.
[0076] In operation of the vaporizer delivery system 10, a first
rotatable spool 36 holding a coil of wire coated with a
sublimatable solid precursor is attached to a rotatable shaft. A
free end of the coated wire is fed through an air lock 31 in
housing 12, through the internal chamber and through another air
lock 31 for attachment to a second rotatable spool 37 that is
aligned with the first rotatable spool to reduced twisting of the
moving wire. At the start of the process, a vacuum is generated
within the internal chamber. At this time there is no carrier gas
flowing through the internal chamber. The entire system including
the internal chamber 16 and coated wire 34 are heated by a heating
means. After an initial heating period, the solid precursor
material is vaporized. A carrier gas is introduced into the
internal chamber via gas inlet port 18 for carrying the vaporized
precursor material through the outlet port 20 to a downstream
processing chamber that requires a flow of the precursor gas.
[0077] After a time, the precursor material will begin to be
completely sublimed off the core wire and at this time a drive
mechanism 39 is activated so that an additional length of coated
wire is unwound from the first rotatable spool while the depleted
wire is wound on the second rotatable spool. Movement of the coated
wire through the internal chamber will continuously expose new
precursor material to the carrier gas and in this manner precursor
material can be continuously supplied to the downstream processing
chamber. The subliming surface area, however, will remain constant,
resulting in a constant net material sublimation rate.
[0078] Referring again to FIG. 1, as the coated wired moves through
the internal chamber, the portion of the coated wire exposed to the
heating section is rapidly vaporized. The vapors are carried
through the internal chamber by the carrier gas through the gas
outlet port to the downstream processing system. The velocity of
the moving wire is generally in the range of about 0.05 to about 10
mm per minute. The carrier gas flow rate is sufficient to provide
the required vaporized precursor gas to the downstream processing
unit and preferably from about 100 to about 1000 cm.sup.3/min
depending on the requirements of the processing system. By way of
example, the internal chamber can be heated to a temperature of
from about 250 to about 2000.degree. C., at a vacuum of from 0.01
mTorr to 10 mTorr, to provide a precursor gas flow rate of from 1
sccm to 500 sccm.
[0079] In an alternate embodiment of the invention, the housing has
a configuration such as shown in FIG. 3. Housing 60, preferably
fabricated of a conductive material as described herein above,
comprises a sealable cover 61, a heating area 62 and a preheating
area 66. A gas inlet port 72 is provided to provide input of a
carrier gas from a carrier gas source 63. This embodiment provides
for a more concentrated heating area 62 while permitting a
preheating section 66 within the internal chamber for positioning a
rotatable spool 68. Placement of the rotatable spool within the
internal chamber provides for preheating of the sublimatable solid
precursor coated on a wire that is wound on the rotatable spool.
Preferably, the rotatable spool is constructed from a material
capable of withstanding high temperatures, such as stainless steel
or material described hereinabove relating to fabrication of the
housing. A drive mechanism 75 draws the coated wire 70 from the
rotatable spool and through the heating area 62, guided by guide
rollers 73, wherein the sublimatable solid precursor is vaporized
forming a precursor gas and a depleted core wire. The depleted core
wire can be drawn through air lock 71 and respooled on rotatable
spool 69. The vaporized precursor gas is removed from the internal
chamber via gas outlet port 74 for passage to a downstream
processing chamber 76. Heat can be supplied to the heating area by
a variety of means as described hereinabove.
[0080] Preferably, the heating means includes an inductive coil 77
for heating the heating area 62 of the internal chamber. The
heating coil is operated by the rf power supply 79. The power
supply may be controlled by feedback from a thermocouple positioned
within the internal chamber (not shown) that is connected to
suitable controls to maintain the heating area at a controlled
temperature. The amount of power required for complete sublimation
of the solid precursor is a function of the chemistry of the solid
precursor material, carrier gas, and the flow rate of the vaporized
precursor gas and carrier gas all within the knowledge of one
skilled in the art.
[0081] It should be recognized that this embodiment may further
comprise a secondary heating source comprising a pair of electrodes
for directing an electrically heating current through the coated
substrate.
[0082] FIG. 4 illustrates another embodiment of the vaporize
delivery system of the present invention wherein both the first 80
and second 82 rotatable spools are positioned within an internal
chamber 84 and holding a metallic substrate coated with a
sublimatable solid precursor 86 positioned therebetween. The coated
substrate is moved through a concentrated heating area 88 that is
heated to the sublimation temperature of the sublimatable solid
precursor for vaporization therein. A carrier gas introduced in gas
inlet port 90 is saturated with the vaporized precursor and removed
from the heating area to a downstream processing chamber via gas
outlet port 92.
[0083] FIG. 5 illustrates yet another embodiment 100 of the present
invention comprising a vaporization chamber 101 having positioned
therein a containerized cassette 102 which includes rotatable
spools for holding the metallic substrate coated with a
sublimatable solid precursor 103. In this specific embodiment, the
coated substrate 104 is continuously uncoiled from a first spool
while only a select portion of the coated substrate is heated to a
temperature sufficient to sublimate the sublimatable solid. Any
heating device that can deliver and concentrate a source of energy
that increases heat and/or electron vibrations in the sublimatable
solid to cause vaporization is contemplated including, but limited
to, electromagnetic radiation, such as frequencies in the infrared
range, ultrasound, ultraviolet, electron gun, acoustic, optical
heating devices. FIG. 5 shows an electromagnetic source 106 being
administered to a small heating spot by 105 for more precise
control of the vaporization process. Advantageously, the present
invention including this embodiment eliminates the need for a
carrier gas to transport the vaporized solid precursor material
from the vaporization chamber to the processing tool 107 and
refilling is merely a replacement of the used cassette.
[0084] Likewise, the embodiment shown in FIG. 6 provides for
similar advantages wherein the heating device is a heating head 124
and/or 125. The coated substrate is passed by heating heads 124
and/or 125 and subjected to a concentrated heating source that
vaporizes the solid substrate for transference to the processing
tool 126.
* * * * *