U.S. patent application number 10/209784 was filed with the patent office on 2002-12-26 for preheating of chemical vapor deposition precursors.
This patent application is currently assigned to Micron Technology, Inc.. Invention is credited to Derderian, Garo J., Morrison, Gordon.
Application Number | 20020195710 10/209784 |
Document ID | / |
Family ID | 24578832 |
Filed Date | 2002-12-26 |
United States Patent
Application |
20020195710 |
Kind Code |
A1 |
Derderian, Garo J. ; et
al. |
December 26, 2002 |
Preheating of chemical vapor deposition precursors
Abstract
Chemical vapor deposition systems include elements to preheat
reactant gases prior to reacting the gases to form layers of a
material on a substrate, which provides devices and systems with
deposited layers substantially free of residual compounds from the
reaction process. Heating reactant gases prior to introduction to a
reaction chamber may be used to improve physical characteristics of
the resulting deposited layer, to improve the physical
characteristics of the underlying substrate and/or to improve the
thermal budget available for subsequent processing. One example
includes the formation of a titanium nitride layer substantially
free of ammonium chloride using reactant gases containing a
titanium tetrachloride precursor and a ammonia precursor.
Inventors: |
Derderian, Garo J.; (Boise,
ID) ; Morrison, Gordon; (Boise, ID) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG, WOESSNER & KLUTH, P.A.
P.O. Box 2938
Minneapolis
MN
55402
US
|
Assignee: |
Micron Technology, Inc.
|
Family ID: |
24578832 |
Appl. No.: |
10/209784 |
Filed: |
July 31, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10209784 |
Jul 31, 2002 |
|
|
|
09642976 |
Aug 18, 2000 |
|
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6451692 |
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Current U.S.
Class: |
257/751 ;
438/627; 438/643; 438/653 |
Current CPC
Class: |
C23C 16/4557 20130101;
H01L 21/76843 20130101; C23C 16/452 20130101; C23C 16/34 20130101;
C23C 16/52 20130101; H01L 21/28556 20130101 |
Class at
Publication: |
257/751 ;
438/627; 438/643; 438/653 |
International
Class: |
C23C 016/00; H01L
021/44; H01L 023/48 |
Claims
what is claimed is:
1. A semiconductor die, comprising: an integrated circuit supported
by a substrate and having a plurality of integrated circuit
devices, wherein at least one of the plurality of integrated
circuit devices comprises a layer of material deposited by a method
comprising: heating a reactant gas containing at least one chemical
vapor deposition precursor to a temperature below an auto-reaction
temperature of each chemical vapor deposition precursor of the
reactant gas; introducing the heated reactant gas to a reaction
chamber containing the substrate; and reacting the reactant gas in
the reaction chamber, wherein reacting the reactant gas deposits at
least the layer of material on the substrate.
2. The semiconductor die of claim 1, wherein the temperature to
which the reactant gas is heated is within about 150.degree. C. of
the auto-reaction temperature of at least one chemical vapor
deposition precursor.
3. The semiconductor die of claim 1, wherein the temperature to
which the reactant gas is heated is within about 50.degree. C. of
the auto-reaction temperature of at least one chemical vapor
deposition precursor.
4. The semiconductor die of claim 1, wherein the temperature to
which the reactant gas is heated is above a temperature which each
precursor of the reactant gas will generally not form an adduct
when combined with a another precursor or a carrier gas.
5. The semiconductor die of claim 1, wherein the layer of material
includes a layer of titanium nitride substantially free of ammonium
chloride.
6. The semiconductor die of claim 1, wherein one chemical vapor
deposition precursor includes titanium tetrachloride.
7. The semiconductor die of claim 1, wherein the temperature to
which the reactant gas is heated is in the range from about
50.degree. C. to about 150.degree. C.
8. A semiconductor die, comprising: an integrated circuit supported
by a substrate and having a plurality of integrated circuit
devices, wherein at least one of the plurality of integrated
circuit devices comprises a layer of material deposited by a method
including: heating a reactant gas containing at least one chemical
vapor deposition precursor to a temperature below an auto-reaction
temperature of each chemical vapor deposition precursor of the
reactant gas with respect to gases in the reactant gas and any
gases to which the reactant gas is to be combined; combining the
heated reactant gas and at least one additional reactant gas;
introducing the combined gases into a reaction chamber containing
the substrate; and reacting the combined gases in the reaction
chamber, wherein reacting the combined gases deposits the layer of
material on the substrate.
9. The semiconductor die of claim 8, wherein the layer of material
includes a layer of titanium nitrid{acute over (e )} substantially
free of ammonium chloride.
10. The semiconductor die of claim 8, wherein the reactant gas
includes titanium tetrachloride.
11. The semiconductor die of claim 8, wherein the temperature to
which the reactant gas is heated is in the range from about
50.degree. C. to about 150.degree. C.
12. The semiconductor die of claim 8, wherein the additional
reactant gas includes ammonia.
13. The semiconductor die of claim 8, wherein the substrate is
heated to about 450.degree. C. for deposition of the layer of
material.
14. A semiconductor die, comprising: an integrated circuit
supported by a substrate and having a plurality of integrated
circuit devices, wherein at least one of the plurality of
integrated circuit devices comprises a layer of material deposited
by a method including: heating a first reactant gas containing at
least one chemical vapor deposition precursor to a first
temperature; heating a second reactant gas containing at least one
chemical vapor deposition precursor to a second temperature,
wherein the first and second temperatures are each below an
auto-reaction temperature of each chemical vapor deposition
precursor of the first and second reactant gases with respect to
gases in the first reactant gas and gases in the second reactant
gas; combining the heated first and second reactant gases;
introducing the heated first and second reactant gases into a
reaction chamber containing the substrate; and reacting the first
and second reactant gases in the reaction chamber, wherein reacting
the first and second reactant gases deposits the layer of material
on the substrate.
15. The semiconductor die of claim 14, wherein the layer of
material includes a layer of titanium nitride substantially free of
ammonium chloride.
16. The semiconductor die of claim 14, wherein the first reactant
gas includes titanium tetrachloride.
17. The semiconductor die of claim 14, wherein the first
temperature is in the range from about 90.degree. C. to about
150.degree. C.
18. The semiconductor die of claim 14, wherein the second reactant
gas includes ammonia.
19. The semiconductor die of claim 14, wherein the second
temperature is below about 200.degree. C.
20. The semiconductor die of claim 14, wherein the substrate
includes a silicon wafer heated to at least 400.degree. C. for
deposition of the layer of material.
21. A semiconductor die, comprising: an integrated circuit
supported by a substrate and having a plurality of integrated
circuit devices, wherein at least one of the plurality of
integrated circuit devices comprises a layer of material deposited
by a method including: combining a first reactant gas with a second
reactant gas, wherein each reactant gas contains at least one
chemical vapor deposition precursor; heating the combined first and
second reactant gases to a temperature below an auto-reaction
temperature of each chemical vapor deposition precursor of the
first and second reactant gases with respect to gases in the first
reactant gas and gases in the second reactant gas; introducing the
heated first and second reactant gases into a reaction chamber
containing the substrate; and reacting the first and second
reactant gases in the reaction chamber, wherein reacting the first
and second reactant gases deposits the layer of material on the
substrate.
22. The semiconductor die of claim 21, wherein the layer of
material includes a layer of titanium nitride substantially free of
ammonium chloride.
23. The semiconductor die of claim 21, wherein the first reactant
gas includes titanium tetrachloride.
24. The semiconductor die of claim 21, wherein the second reactant
gas includes ammonia.
25. The semiconductor die of claim 21, wherein the combined first
and second reactant gases are heated to a temperature below about
200.degree. C.
26. The semiconductor die of claim 21, wherein the substrate
includes a silicon wafer heated to a temperature ranging from about
450.degree. C. to about 650.degree. C. for deposition of the layer
of material.
27. A semiconductor die, comprising: an integrated circuit
supported by a substrate having a layer of titanium nitride
substantially free of ammonium chloride deposited by a method
including: heating a first reactant gas containing titanium
tetrachloride to a first temperature; heating a second reactant gas
containing ammonia to a second temperature, wherein the first and
second temperatures are each below an auto-reaction temperature of
titanium tetrachloride and ammonia with respect to gases in the
first reactant gas and gases in the second reactant gas; combining
the heated first and second reactant gases; introducing the
combined first and second reactant gases into a reaction chamber
containing the substrate; reacting the first and second reactant
gases in the reaction chamber, wherein reacting the first and
second reactant gases forms the layer of titanium nitride
substantially free of ammonium chloride.
28. The semiconductor die of claim 27, wherein the first and second
temperatures are each below about 200.degree. C.
29. The semiconductor die of claim 27, wherein the substrate
includes a silicon wafer heated to a temperature ranging from about
450.degree. C. to about 650.degree. C. for deposition of the layer
of titanium nitride substantially free of ammonium chloride.
30. The semiconductor die of claim 27, wherein the substrate
includes a silicon wafer heated to a temperature of about
580.degree. C. for deposition of the layer of titanium nitride
substantially free of ammonium chloride.
31. The semiconductor die of claim 27, wherein the first and second
temperatures are substantially equal.
32. The semiconductor die of claim 27, wherein the first and second
temperatures have a temperature difference having a magnitude of
about 10.degree. C.
33. The semiconductor die of claim 27, wherein the first
temperature is about 150.degree. C.
34. The semiconductor die of claim 27, wherein the second
temperature is about 90.degree. C.
35. An electronic system, comprising: a processor; and a circuit
module having a plurality of leads coupled to the processor, and
further having a semiconductor die coupled to the plurality of
leads, wherein the semiconductor die comprises: an integrated
circuit supported by a substrate and having a plurality of
integrated circuit devices, wherein at least one of the plurality
of integrated circuit devices comprises a layer of material
deposited by a method including: heating a reactant gas containing
at least one chemical vapor deposition precursor to a temperature
below an auto-reaction temperature of each chemical vapor
deposition precursor of the reactant gas; introducing the heated
reactant gas into a reaction chamber containing the substrate; and
reacting the reactant gas in the reaction chamber, wherein reacting
the reactant gas deposits at least the layer of material on the
substrate.
36. The electronic system of claim 35, wherein the temperature to
which the reactant gas is heated is within about 150.degree. C. of
the auto-reaction temperature of at least one chemical vapor
deposition precursor.
37. The electronic system of claim 35, wherein the temperature to
which the reactant gas is heated is within about 50.degree. C. of
the auto-reaction temperature of at least one chemical vapor
deposition precursor.
38. The electronic system of claim 35, wherein the temperature to
which the reactant gas is heated is above a temperature which each
precursor of the reactant gas will generally not form an adduct
when combined with a another precursor or a carrier gas.
39. The electronic system of claim 35, wherein the layer of
material includes a layer of titanium nitride substantially free of
ammonium chloride.
40. The electronic system of claim 35, wherein one chemical vapor
deposition precursor includes titanium tetrachloride.
41. The electronic system of claim 35, wherein the temperature to
which the reactant gas is heated is in the range from about
50.degree. C. to about 150.degree. C.
42. An electronic system, comprising: a processor; and a circuit
module coupled to the processor, the circuit module having an
integrated circuit supported by a substrate, the integrated circuit
having a layer of material deposited by a method including: heating
a reactant gas containing at least one chemical vapor deposition
precursor to a temperature below an auto-reaction temperature of
each chemical vapor deposition precursor of the reactant gas with
respect to gases in the reactant gas and any gases to which the
reactant gas is to be combined; combining the heated reactant gas
and at least one additional reactant gas; introducing the combined
gases into a reaction chamber containing the substrate; and
reacting the combined gases in the reaction chamber, wherein
reacting the combined gases deposits the layer of material on the
substrate.
43. The electronic system of claim 42, wherein the layer of
material includes a layer of titanium nitride substantially free of
ammonium chloride.
44. The electronic system of claim 42, wherein the reactant gas
includes titanium tetrachloride.
45. The electronic system of claim 42, wherein the temperature to
which the reactant gas is heated is in the range from about
50.degree. C. to about 150.degree. C.
46. The electronic system of claim 42, wherein the additional
reactant gas includes ammonia.
47. The electronic system of claim 42, wherein the substrate is
heated to a temperature of about 450.degree. C. for deposition of
the layer of material.
48. The electronic system of claim 42, wherein the electronic
system is a computer.
49. An electronic system, comprising: a memory controller; a
command link; and a memory module coupled to the memory controller
by the command link, the memory module including an integrated
circuit supported by a substrate, the integrated circuit having a
layer of material deposited by a method including: heating a first
reactant gas containing a chemical vapor deposition precursor to a
first temperature; heating a second reactant gas containing a
chemical vapor deposition precursor to a second temperature,
wherein the first and second temperatures are each below an
auto-reaction temperature of each chemical vapor deposition
precursor of the first and second reactant gases with respect to
gases in the first reactant gas and gases in the second reactant
gas; combining the heated first and second reactant gases;
introducing the heated first and second reactant gases into a
reaction chamber containing the substrate; and reacting the first
and second reactant gases in the reaction chamber, wherein reacting
the first and second reactant gases deposits the layer of material
on the substrate.
50. The electronic system of claim 49, wherein the layer of
material includes a layer of titanium nitride substantially free of
ammonium chloride.
51. The electronic system of claim 49, wherein the first reactant
gas includes titanium tetrachloride.
52. The electronic system of claim 49, wherein the first
temperature is in the range from about 90.degree. C. to about
150.degree. C.
53. The electronic system of claim 49, wherein the second reactant
gas includes ammonia.
54. The electronic system of claim 49, wherein the second
temperature is below about 200.degree. C.
55. The electronic system of claim 49, wherein the substrate
includes a silicon wafer heated to at least 400.degree. C. for
deposition of the layer of material.
56. The electronic system of claim 49, wherein the electronic
system is incorporated on a single integrated circuit.
57. An electronic system, comprising: a processor; and a memory
system coupled to the processor, the memory system having a
plurality of integrated circuits, wherein at least one integrated
circuit has a layer of material deposited on a substrate by a
method including: combining a first reactant gas with a second
reactant gas, wherein each reactant gas contains at least one
chemical vapor deposition precursor; heating the combined first and
second reactant gases to a temperature below an auto-reaction
temperature of each chemical vapor deposition precursor of the
first and second reactant gases with respect to gases in the first
reactant gas and gases in the second reactant gas; introducing the
heated first and second reactant gases into a reaction chamber
containing the substrate; and reacting the first and second
reactant gases in the reaction chamber, wherein reacting the first
and second reactant gases deposits the layer of material on the
substrate.
58. The electronic system of claim 57, wherein the layer of
material includes a layer of titanium nitride substantially free of
ammonium chloride.
59. The electronic system of claim 57, wherein the first reactant
gas includes titanium tetrachloride.
60. The electronic system of claim 57, wherein the second reactant
gas includes ammonia.
61. The electronic system of claim 57, wherein the combined first
and second reactant gases are heated to a temperature below about
200.degree. C.
62. The electronic system of claim 57, wherein the substrate
includes a silicon wafer heated to a temperature ranging from about
450.degree. C. to about 650.degree. C. for deposition of the layer
of material.
63. An electronic system, comprising: a processor; and a circuit
module coupled to the processor, the circuit module including an
integrated circuit supported by a substrate having a layer of
titanium nitride substantially free of ammonium chloride deposited
by a method including: heating a first reactant gas containing
titanium tetrachloride to a first temperature; heating a second
reactant gas containing ammonia to a second temperature, wherein
the first and second temperatures are each below an auto-reaction
temperature of titanium tetrachloride and ammonia with respect to
gases in the reactant gas and gases in the second reactant gas;
combining the heated first and second reactant gases; introducing
the combined first and second reactant gases to a reaction chamber
containing the substrate; reacting the first and second reactant
gases in the reaction chamber, wherein reacting the first and
second reactant gases forms the layer of titanium nitride
substantially free of ammonium chloride.
64. The electronic system of claim 63, wherein the first and second
temperatures are each below about 200.degree. C.
65. The electronic system of claim 63, wherein the substrate
includes a silicon wafer heated to a temperature ranging from about
450.degree. C. to about 650.degree. C. for deposition of the layer
of titanium nitride substantially free of ammonium chloride.
66. The electronic system of claim 63, wherein the substrate
includes a silicon wafer heated to about 580.degree. C. for
deposition of the layer of titanium nitride substantially free of
ammonium chloride.
67. The electronic system of claim 63, wherein the first and second
temperatures have a temperature difference having a magnitude of
about 10.degree. C.
68. The electronic system of claim 63, wherein the first
temperature is about 150.degree. C .
69. The electronic system of claim 63, wherein the second
temperature is about 90.degree. C.
Description
[0001] This application is a Divisional of U.S. application Ser.
No. 09/642,976, filed Aug. 18, 2000 which is incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present invention relates generally to chemical vapor
deposition, and in particular to methods for chemical vapor
deposition including preheating of the chemical vapor deposition
precursors, systems to perform the methods, and apparatus produced
by such methods.
BACKGROUND
[0003] Semiconductor integrated circuits (ICs) contain individual
devices that are typically coupled together using metal line
interconnects and various contacts. In many applications, the metal
lines are formed on a different level than the devices, separated
by an intermetal dielectric, such as silicon oxide or
borophosphosilicate glass (BPSG). Commonly used metal lines include
aluminum, tungsten and copper, as well as combinations of these
materials with refractory metals and silicon. Interconnects used to
electrically couple devices and metal lines are formed between the
individual devices and the metal lines. A typical interconnect is
composed of a contact hole (i.e. opening) formed in an intermetal
dielectric layer over an active device region. The contact hole is
often filled with a metal, such as aluminum or tungsten.
[0004] Interconnects often further contain a diffusion barrier
layer sandwiched between the interconnect metal and the active
device region at the bottom of the contact hole. Such layers
prevent intermixing of the metal and the material from the active
device region, such as silicon. Reducing intermixing generally
extends the life of the device. Passive titanium nitride (TiN)
layers are commonly used as diffusion barrier layers. An example
may include the use of titanium nitride interposed between a
silicide contact and a metal fill within a contact hole. Further
uses of diffusion barrier layers may include a barrier layer
interposed between a polysilicon layer and a metal layer in a gate
stack of a field effect transistor.
[0005] Titanium nitride is a desirable barrier layer because it is
an impermeable barrier for silicon, and because it presents a high
barrier to the diffusion of other impurities. Titanium nitride has
relatively high chemical and thermodynamic stability and a
relatively low resistivity. Titanium nitride layers are also often
used as adhesion layers, such as for tungsten films. While titanium
nitride can be formed on the substrate by physical vapor deposition
(PVD) or chemical vapor deposition (CVD) techniques, CVD is often
the technique of choice.
[0006] CVD is a process in which a deposition surface is contacted
with vapors of volatile chemical compounds, generally at elevated
temperatures. The compounds, or CVD precursors, are reduced or
dissociated at the deposition surface, resulting in an adherent
coating of a preselected composition. In contrast to physical
deposition, CVD does not require high vacuum systems and permits a
wide variety of processing environments, including low pressure
through atmospheric pressure, and is an accepted method for
depositing homogeneous films over large areas and on non-planar
surfaces.
[0007] CVD is often classified into various types in accordance
with the heating method, gas pressure, and/or chemical reaction.
For example, conventional CVD methods include cold-wall CVD, in
which only a deposition substrate is heated; hot-wall CVD, in which
an entire reaction chamber is heated; atmospheric CVD, in which
reaction occurs at a pressure of about one atmosphere; low-pressure
CVD (LPCVD) in which reaction occurs at pressures from about
10.sup.-1 to 100 torr; and plasma-assisted CVD (PACVD) and
photo-assisted CVD in which the energy from a plasma or a light
source activates the precursor to allow depositions at reduced
substrate temperatures. Other classifications are known in the
art.
[0008] In a typical CVD process, the substrate on which deposition
is to occur is placed in a reaction chamber, and is heated to a
temperature sufficient to drive the desired reaction. The reactant
gases containing the CVD precursors are introduced into the
reaction chamber where the precursors are transported to, and
subsequently adsorbed on, the deposition surface. Surface reactions
deposit nonvolatile reaction products on the deposition surface.
Volatile reaction products are then evacuated or exhausted from the
reaction chamber. While it is generally true that the nonvolatile
reaction products are deposited on the deposition surface, and that
volatile reaction products are removed, the realities of industrial
processing recognize that undesirable volatile reaction products,
as well as nonvolatile reaction products from secondary or side
reactions, may be incorporated into the deposited layer. Integrated
circuit fabrication generally includes the deposition of a variety
of material layers on a substrate, and CVD may used to deposit one
or more of these layers.
[0009] As an example, one LPCVD process combines titanium
tetrachloride (TiCl.sub.4) and ammonia (NH.sub.3) to deposit
titanium nitride. However, LPCVD titanium nitride using these
precursors has a tendency to incorporate a large amount of residual
ammonium chloride in the film. This residual ammonium chloride
detrimentally effects the resistivity and barrier properties of the
titanium nitride layer. Once exposed to air, the residual ammonium
chloride will cause the titanium nitride layer to absorb water and
to form particles, both undesirable effects. It is known that
residual ammonium chloride can be reduced by the use of ammonia
post-flow, or annealing in an ammonia atmosphere, subsequent to
deposition. However, such post-processing leads to reduced
throughput and a higher risk of particle formation. It is also
known that increased reaction temperatures can be used to reduce
the incorporation of residual ammonium chloride. However, this,
too, is detrimental as increased processing temperatures reduce the
thermal budget available for subsequent processing and often lead
to undesirable dopant diffusion.
[0010] For the reasons stated above, and for other reasons stated
below which will become apparent to those skilled in the art upon
reading and understanding the present specification, there is a
need in the art for alternative methods of chemical vapor
deposition.
SUMMARY
[0011] The various embodiments of the invention include chemical
vapor deposition methods, chemical vapor deposition systems to
perform the methods, and apparatus produced by such chemical vapor
deposition methods. The methods involve preheating one or more of
the reactant gases used to form a deposited layer. The reactant
gases contain at least one chemical vapor deposition precursor.
Heating one or more of the reactant gases prior to introduction to
the reaction chamber may be used to improve physical
characteristics of the resulting deposited layer, to improve the
physical characteristics of the underlying substrate and/or to
improve the thermal budget available for subsequent processing. One
example includes the formation of a titanium nitride layer with
reactant gases containing the precursors of titanium tetrachloride
and ammonia. Preheating the reactant gases containing titanium
tetrachloride and ammonia can reduce ammonium chloride impurity
levels in the resulting titanium nitride layer, thereby reducing or
eliminating the need for post-processing to remove the ammonium
chloride impurity.
[0012] For one embodiment, the invention provides a method of
depositing a layer of material on a substrate. The method includes
heating a reactant gas containing at least one chemical vapor
deposition precursor to a temperature within approximately
150.degree. C. of an auto-reaction temperature of each chemical
vapor deposition precursor of the reactant gas, introducing the
heated reactant gas to a reaction chamber containing the substrate,
and reacting the reactant gas in the reaction chamber. Reacting the
reactant gas involves reaction of the chemical vapor deposition
precursors to deposit the layer of material on the substrate. It is
recognized that additional compounds may be incorporated into the
layer of material, such as nonvolatile reaction products from side
reactions deposited in the layer of material as well as volatile
reaction products from desired or side reaction products entrapped
in the layer of material.
[0013] For another embodiment, the invention provides a method of
depositing a layer of material on a substrate. The method includes
heating a reactant gas containing at least one chemical vapor
deposition precursor to a temperature below an auto-reaction
temperature of each chemical vapor deposition precursor of the
reactant gas, combining the heated reactant gas and at least one
additional reactant gas, introducing the combined gases to a
reaction chamber containing the substrate, and reacting the
combined gases in the reaction chamber. Reacting the combined gases
deposits at least the layer of material on the substrate. For yet
another embodiment, the additional reactant gases are also heated
prior to introduction to the reaction chamber.
[0014] For a further embodiment, the invention provides a method of
depositing a layer of titanium nitride on a substrate. The method
includes heating a first reactant gas containing titanium
tetrachloride to a first temperature and heating a second reactant
gas containing ammonia to a second temperature. The first and
second temperatures are each below an auto-reaction temperature of
titanium tetrachloride and ammonia. The method further includes
combining the heated first and second reactant gases, introducing
the combined first and second reactant gases to a reaction chamber
containing the substrate, reacting the first and second reactant
gases in the reaction chamber to produce titanium nitride, and
depositing the titanium nitride on the substrate.
[0015] For another embodiment, the invention provides a chemical
vapor deposition system. The chemical vapor deposition system
includes a gas source, a reaction chamber, a gas conduit coupled
between the gas source and the reaction chamber, a heater, a gas
flow temperature sensor coupled to the gas conduit between the
heater and the reaction chamber, and a control system coupled to
the gas flow temperature sensor and the heater. The control system
is adapted to adjust energy input from the heater to the gas
conduit in response to data from the gas flow temperature sensor.
For yet another embodiment, the chemical vapor deposition system
further includes a gas flow control valve coupled to the gas
conduit. For this embodiment, the control system is further coupled
to the gas flow control valve and is further adapted to control an
opening of the gas flow control valve in response to data from the
gas flow temperature sensor.
[0016] Further embodiments of the invention include deposition
methods and chemical vapor deposition systems of varying scope, as
well as apparatus making use of such deposition methods and
chemical vapor deposition systems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a schematic block diagram of one embodiment of a
chemical vapor deposition system.
[0018] FIG. 2 is an elevation view of one embodiment of a wafer
containing semiconductor dies.
[0019] FIG. 3 is a block diagram of one embodiment of an integrated
circuit memory device.
[0020] FIG. 4 is a block diagram of one embodiment of an exemplary
circuit module.
[0021] FIG. 5 is a block diagram of one embodiment of an exemplary
memory module.
[0022] FIG. 6 is a block diagram of one embodiment of an exemplary
electronic system.
[0023] FIG. 7 is a block diagram of one embodiment of an exemplary
memory system.
[0024] FIG. 8 is a block diagram of one embodiment of an exemplary
computer system.
DESCRIPTION OF THE EMBODIMENTS
[0025] In the following detailed description of the preferred
embodiments, reference is made to the accompanying drawings which
form a part hereof, and in which is shown by way of illustration
specific embodiments in which the inventions may be practiced.
These embodiments are described in sufficient detail to enable
those skilled in the art to practice the invention, and it is to be
understood that other embodiments may be utilized and that process
or mechanical changes may be made without departing from the scope
of the present invention. The terms wafer and substrate used in the
following description include any base semiconductor structure.
Both are to be understood as including silicon-on-sapphire (SOS)
technology, silicon-on-insulator (SOI) technology, thin film
transistor (TFT) technology, doped and undoped semiconductors,
epitaxial layers of a silicon supported by a base semiconductor
structure, as well as other semiconductor structures well known to
one skilled in the art. Furthermore, when reference is made to a
wafer or substrate in the following description, previous process
steps may have been utilized to form regions/junctions in the base
semiconductor structure, and terms wafer or substrate include the
underlying layers containing such regions/junctions. The following
detailed description is, therefore, not to be taken in a limiting
sense, and the scope of the present invention is defined only by
the appended claims and equivalents thereof.
[0026] FIG. 1 shows a simplified schematic block diagram
illustrating one embodiment of a Chemical Vapor Deposition (CVD)
system 100 in accordance with the invention. It is to be understood
that the CVD system 100 has been simplified to illustrate only
those aspects of the CVD system 100 relevant for a clear
understanding of the present invention, while eliminating, for the
purposes of clarity, many of the elements found in a typical CVD
system 100. Those of ordinary skill in the art will recognize that
other elements are required, or at least desirable, to produce an
operational CVD system 100. However, because such elements are well
known in the art, and because they do not relate to the design
which is the subject of the various embodiments, a discussion of
such elements is not provided herein.
[0027] The design and construction of CVD systems is well known,
and the present invention is applicable to any CVD system. The CVD
system 100 for one embodiment comprises a cold wall reaction
chamber 112, typically constructed of stainless steel. The bottom
and sides of the reaction chamber 112 may be lined with quartz to
protect the walls from film deposition during the processing steps.
The walls of the reaction chamber 112 may be cooled by a
circulating water jacket (not shown) in conjunction with a heat
exchanger (not shown). The walls are generally maintained at or
below 100.degree. C., because higher temperatures may induce the
deposition of films on the walls of the reaction chamber 112. Such
depositions are undesirable because they absorb energy and effect
heat distribution within the reaction chamber 112, causing
temperature gradients which adversely affect the processing steps.
Furthermore, depositions on walls may flake and produce
particulates that can contaminate a wafer in the reaction chamber
112. However, such cooling of the walls of the reaction chamber 112
is within the discretion of the designer.
[0028] A wafer support table 114 or the like is located near the
bottom of the reaction chamber 112, and is used for supporting a
wafer or substrate 116. The support table 114 is generally a flat
surface, typically having three or more vertical support pins 115
with low thermal mass. The support table 114 may be heated to help
reduce temperature variations on the supported substrate 116.
[0029] A wafer handling system 118 is adjacent to the reaction
chamber 112, and includes a wafer cassette 120 and a wafer handler
122. The wafer cassette 120 holds a plurality of wafers (substrates
116), and the wafer handler 122 transports one wafer at a time from
the wafer cassette 120 to the wafer support table 114, and back
again. A door 124 isolates the wafer handling system 118 from the
reaction chamber 112 when the wafers are not being transported to
and from the wafer support table 114.
[0030] A showerhead 126 introduces reactant gases 127 into the
reaction chamber 112, and a plurality of light sources 128 heat the
substrate 116. For the purposes of this description, the embodiment
will be described in terms of light sources 128, although other
sources of heating a substrate 116, such as RF and microwave
energy, are known and applicable to the present invention. In
addition, the showerhead 126 is depicted to be above the surface of
substrate 116, although showerhead 126 may optionally be disposed
to the side of substrate 116 as well as underneath substrate 116.
Furthermore, distribution devices other than showerhead 126 may be
used to introduce and distribute reactant gases 127 to the reaction
chamber 112.
[0031] One or more gas sources 130A-B are coupled to the showerhead
126 to provide one or more of the reactant gases 127 to be
disbursed by the showerhead 126 within the reaction chamber 112.
More than one type of gas may be available from each gas source
130, and reactant gases 127 may be provided to the showerhead 126
individually or in combination.
[0032] Each reactant gas includes at least one CVD precursor.
Examples of CVD precursors include titanium tetrachloride and
ammonia. These precursors can be combined to deposit titanium
nitride. In a pyrolysis system, the reactant gases may require only
one CVD precursor. An example of such a system includes silane
(SiH.sub.4) which can be used to deposit silicon (Si) without
further precursors. Although the term "reactant gas" is used, one
or more of the reactant gases 127 may include a carrier, or
non-reactive, gas. Examples of carrier gases include nitrogen
(N.sub.2), argon (Ar), helium (He), and other non-reactive gases
used in the art of chemical vapor deposition. CVD system 100 may
further include additional gas sources providing only carrier
gases.
[0033] Gas flow control valves 132A and 132B control the flow of
gases from gas sources 130A and 130B, respectively, through gas
conduits 133A and 133B, respectively. Gas conduits represent a flow
path for the reactant gases 127 between the gas sources 130 and the
reaction chamber 112. Gas conduits include such things as piping
between elements of the CVD system 100 as well as spaces or
channels for gas flow within elements of the CVD system 100. Gas
conduits 133A and 133B merge at combination node 135 to become a
single gas conduit 137, thus combining the gases from gas sources
130A and 130B. Gas conduits 133A and 133B can be thought of as
inputs to combination node 135, while gas conduit 137 can be
thought of as an output of combination node 135. One example of
combination node 135 includes a simple Y-fitting of piping making
up the gas conduits. Another example of combination node 135
includes a gas manifold allowing selection of reactant and carrier
gases from a variety of gas sources. Gas conduit 137 may contain a
static mixer or other mixing element to improve homogeneity of the
reactant gases 127. For one embodiment, the gas conduits 133A and
133B are not merged outside the reaction chamber. For this
embodiment, the gases from gas sources 130A and 130B are combined
subsequent to heating, but within the reaction chamber 112. One
example includes a heated showerhead 126 having separate flow
channels for each reactant gas 127, thus heating the reactant gases
127 prior to combination in the reaction chamber 112.
[0034] Heaters 134A and 134B supply energy to the gas conduits 133A
and 133B, respectively, and thus supply energy to the flow of gases
from gas sources 130A and 130B, respectively. Heaters 134 may be
any heater or heat exchanger capable of supplying energy to the gas
conduits 133 in order to produce a rise in temperature to the gases
from gas sources 130. Supplying energy to the gas conduits 133 may
include passing radiation or other energy through the gas conduits
133 that is absorbed by gases within the gas conduits 133. Examples
of heaters 134 include resistive heat tracing, IR radiation sources
or other electric heaters as well as direct-fired, jacketed or
wrapped heat exchangers. Heating thus involves raising the gas
temperature above an ambient temperature.
[0035] Gas flow temperature sensors 136A and 136B sense the
temperature of the flow of gases from gas sources 130A and 130B,
respectively. For one embodiment, gas flow temperature sensors 136
sense the temperature of the flow of gases directly from the gas
flow. For another embodiment, gas flow temperature sensors 136
sense the temperature of one or more portions of heaters 134 and
derive the temperature of the flow of gases from the heater
temperatures and the theoretical approach temperatures predicted by
the physical characteristics of the heaters 134, conduits 133 and
reactions gases 127. For one embodiment, gas flow temperature is
sensed after combination of the reactant gases 127 in addition to
being sensed prior to combination as depicted in FIG. 1. For a
further embodiment, gas flow temperature is sensed only after
combination of the reactant gases 127.
[0036] Jacket 144 may be used downstream of heaters 134 to reduce
any tendency of the gases to condense prior to reaching reaction
chamber 112. Jacket 144 may be a simple insulative jacket to
control energy loss of reactant gases 127 by conduction.
Alternatively, jacket 144 may control energy loss by supplying
additional energy input to the reactant gases 127, as described
with reference to heaters 134, in addition to or in lieu of
providing insulation. Heaters 134 and jacket 144 may be separate
units, as depicted in FIG. 1, or they may be a single unit
supplying energy to reactant gases 127 before and after
combination. Although not shown in FIG. 1, jacket 144, if not
merely an insulative jacket, may be coupled to the control system
146, described below, for control of energy input by jacket 144. In
a similar manner, showerhead 126 may be adapted to supply energy to
the reactant gases 127, as described with reference to heaters 134
and jacket 144, in addition to or in lieu of heaters 134 and jacket
144.
[0037] Jacket 144 is coupled to at least gas conduit 137 to control
energy loss of reactant gases 127 between combination node 135 and
reaction chamber 112. As shown in FIG. 1, jacket 144 may be further
coupled to at least a portion of gas conduits 133 extending between
heaters 134 and combination node 135.
[0038] Exhaust gases are removed from the reaction chamber 112, and
a vacuum may be created within the reaction chamber 112, by a gas
exhaust and vacuum system 142, as is well known in the art. Also
present is a wafer temperature sensor 138, such as a pyrometer,
which is used to measure the temperature of the substrate 116
through a window 140.
[0039] A control system 146 monitors and controls the various
elements that make up the CVD system 100, such as the wafer handler
122, the gas flow control valves 132, the heaters 134, the gas flow
temperature sensors 136, the wafer temperature sensor 138, and the
gas exhaust and vacuum system 142. Control system 146 is in
communication with the various elements of CVD system 100 such that
process information is passed from these elements to control system
146 through communication lines, and process control information is
passed from control system 146 to various elements of CVD system
100 through communication lines. It is noted that communications
may be bidirectional across a communication line. Control system
146 may include distributed and centralized computerized industrial
process control systems, as are well known in the art. Such control
systems generally include a machine-readable medium containing
instructions capable of causing the control system, or more
directly, a processor within the control system, to monitor and
control the various elements coupled to the control system.
Examples of such machine-readable medium include random access
memory (RAM), read only memory (ROM), optical storage mediums,
magnetic tape drives, and magnetic disk drives. The
machine-readable medium may be fixed, such as an installed hard
drive or memory module, or removable, such as a magnetic diskette
or data cartridge.
[0040] Data indicating the temperature of the substrate 116 is
generated by the wafer temperature sensor 138, and is used by the
control system 146 to adjust the intensity of the light sources 128
so as to produce a desired wafer temperature. Data indicating the
temperature of the gas flow from gas sources 130 is generated by
the gas flow temperature sensors 136, and is used by the control
system 146 to adjust the energy input of heaters 134, jacket 144
(if not a simple insulative jacket) and/or the flow rate of flow
control valves 132 (reductions in flow rate can be used to increase
the gas flow temperature at a given energy input).
[0041] In addition, multiple wafer temperature sensors 138 may be
used to sense the temperature of different regions of the substrate
116. That data may be used by the control system 146 to selectively
adjust the intensity of some of the light sources 128 so as to
compensate for uneven heating of the substrate 116. The control
system 146 also controls when and what gases are provided to the
showerhead 126, as well as when exhaust gases are removed from the
reaction chamber 112, in a known manner.
[0042] The operation of the CVD system 100 will be described with
reference to the deposition of titanium nitride (TiN) from titanium
tetrachloride (TiCl.sub.4) and ammonia (NH.sub.3). However, the
invention is not limited to this chemical system. Other reactant
gases may utilized to form layers of TiN as well as layers having
other compositions.
[0043] For one embodiment, gas source 130A provides titanium
tetrachloride and gas source 130B provides ammonia. Flow control
valve 132A controls the flow of titanium tetrachloride from gas
source 130A as directed by control system 146 in response to a
desired titanium nitride deposition rate. Flow control valve 132B
controls the flow of ammonia from gas source 130B as directed by
control system 146 in response to the desired titanium nitride
deposition rate. Gas flow may be directly controlled by the control
system 146 by producing a set opening of a flow control valve 132
based on a desired deposition rate. Alternatively, gas flow may be
indirectly controlled by the control system 146 by utilizing a
feedback controller (not shown) and producing a flow rate setpoint
for the feedback controller which, in turn, controls the opening of
a flow control valve 132. Control of gas flows may be responsive to
other factors in addition to or in lieu of a desired deposition
rate. As one example, flow of titanium tetrachloride may be
responsive to a desired deposition rate while flow of ammonia may
be responsive to a desired ammonia concentration in the reaction
chamber 112. To extend this example, the flow of ammonia may have a
maximum limit such that an ammonia concentration calling for
ammonia flow rates above the maximum limit may direct a reduction
in titanium tetrachloride flow rate despite being lower than
expected for the desired deposition rate. As a further example,
control of both flow rates may be responsive to desired
concentrations within the reaction chamber 112.
[0044] Energy is supplied by heaters 134A and 134B to the gases
from gas sources 130A and 130B, respectively, prior to combination
of the gases for this embodiment. It is generally preferred to heat
the gases prior to combination in order to reduce the probability
of forming an adduct or inclusion complex of the gas molecules.
Combining gases cold may lead to formation of an adduct. It is
preferred to avoid forming an adduct as the adduct may require
excessive or undesirable energy input to break the association of
the individual gas molecules. Adducts having a negative effect on
deposition may form between a precursor and other constituents of
the reactant gases, e.g., another precursor or a carrier gas.
[0045] For one embodiment, one or more of the gases from gas
sources 130A and 130B are heated to a temperature below the
auto-reaction temperature, or the lowest temperature at which at
least one precursor will react without further energy input, prior
to introduction to the reaction chamber 112. For another
embodiment, the gases from gas sources 130A and 130B are each
heated to a temperature within approximately 150.degree. C. of the
auto-reaction temperature prior to introduction. For a further
embodiment, the gases from gas sources 130A and 130B are each
heated to a temperature within approximately 50.degree. C. of the
auto-reaction temperature prior to introduction.
[0046] For yet another embodiment, one or more of the gases from
gas sources 130A and 130B are heated to a temperature at or above
which they generally will not form an adduct when combined. For a
further embodiment, the gases from gas sources 130A and 130B are
each heated, prior to combination, to a temperature at least
approximately 50.degree. C. above the temperature at which they
generally will not form an adduct. It is recognized that the
auto-reaction temperature and the temperature above which the gases
will generally not form an adduct are dependent upon the pressure
chosen for operation of the CVD system 100.
[0047] When only one reactant gas is heated, its temperature should
be chosen such that, when combined with other reactant or carrier
gases, no adduct will form and auto-reaction will not occur. While
temperatures approaching the auto-reaction temperature, and
diverging from conditions favoring adducts, are preferred, the
designer should recognize that hot spots within the heaters may
lead to localized reaction if a temperature too close the
auto-reaction temperature is chosen.
[0048] For one embodiment, the temperature of each reactant gas is
adjusted to be substantially equal at the time of combination. For
another embodiment, the range of temperatures of the reactant gases
has a magnitude of at least approximately 10.degree. C. at the time
of combination. When the temperatures of the various reactant gases
are not substantially equal at the time of combination,
temperatures should be chosen such that, when combined, no adduct
will form and auto-reaction will not occur.
[0049] For an embodiment utilizing the precursors of titanium
tetrachloride and ammonia to form titanium nitride, and a CVD
system 100 operating at a chamber pressure of approximately 0.2-10
torr and a substrate temperature of 450-650.degree. C., the
titanium tetrachloride and the ammonia are each heated to a
temperature in the range of approximately 200-300.degree. F.
(90-150.degree. C.) prior to combination. Typical flow rates under
these conditions may be 10-50 sccm for titanium tetrachloride and
50-150 sccm for ammonia. For a specific embodiment, the chamber
pressure is approximately 1 torr, the substrate temperature is
approximately 580.degree. C., the titanium tetrachloride flow rate
is approximately 30 sccm and the ammonia flow rate is approximately
100 sccm. It has been reported that reaction of titanium
tetrachloride and ammonia can be effected at temperatures as low as
200.degree. C. Therefore, the substrate temperature chosen to drive
the reaction at the surface of the substrate should not be confused
with the auto-reaction temperature of the precursors.
[0050] For one embodiment, the temperature of the reactant gas
containing the titanium tetrachloride and the temperature of the
reactant gas containing the ammonia are substantially equal at the
time of combination. For another embodiment, the difference between
the temperature of the reactant gas containing the titanium
tetrachloride and the temperature of the reactant gas containing
the ammonia has a magnitude of at least approximately 10.degree. C.
at the time of combination. The temperature of the gases before and
after combination is maintained by jacket 144. For one embodiment,
the temperature of the gases after combination is further raised by
jacket 144 in accordance with the above guidelines relating to the
auto-reaction temperature, i.e., maintaining the gas temperature
below the auto-reaction temperature prior to introduction to the
reaction chamber 112.
[0051] The heated reactant gases 127 enter the reaction chamber 112
where the precursors are transported to the surface of the
substrate 116. The reactant gases 127 react to deposit a layer of
material on the surface of the substrate 116. In more detail, the
precursors of the reactant gases 127 are adsorbed on the surface of
the substrate 116 where they react and deposit, in this case,
titanium nitride. Heating the reactant gases 127 prior to
introduction to the reaction chamber 112 as described above has
been shown to reduce the formation of ammonium chloride in
deposited titanium nitride layers, thus reducing or eliminating the
need for an ammonia post-flow procedure. Reducing the formation of
impurities during deposition can also permit deposition at reduced
chamber temperatures, thus reducing undesirable diffusion within
the substrate and improving the thermal budget available for
subsequent processing. Accordingly, reactant gas preheating may be
used to improve physical characteristics of the resulting deposited
layer, to improve the physical characteristics of the underlying
substrate and/or to improve the thermal budget available for
subsequent processing. Furthermore, a given impurity level may be
attained at reduced thermal input to the substrate, thus reducing
undesirable diffusion of implants in integrated circuit
devices.
[0052] As noted previously, and as is well known, integrated
circuit fabrication involves the deposition of a plurality of
layers supported by a substrate. The CVD processes and systems
described herein may be used to form one or more of these layers.
Integrated circuits are typically repeated multiple times on each
substrate. The substrate is further processed to separate the
integrated circuits into dies as is well known in the art.
[0053] Semiconductor Dies
[0054] With reference to FIG. 2, for one embodiment, a
semiconductor die 210 is produced from a wafer 200. A die is an
individual pattern, typically rectangular, on a substrate that
contains circuitry, or integrated circuit devices, to perform a
specific function. At least one of the integrated circuit devices
contains at least one CVD-deposited layer formed in accordance with
the invention. For one embodiment, the CVD-deposited layer formed
in accordance with the invention is a titanium nitride layer. A
semiconductor wafer will typically contain a repeated pattern of
such dies containing the same functionality. Die 210 may contain
circuitry to extend to such complex devices as a monolithic
processor with multiple functionality. Die 210 is typically
packaged in a protective casing (not shown) with leads extending
therefrom (not shown) providing access to the circuitry of the die
for unilateral or bilateral communication and control.
[0055] One example of an integrated circuit device utilizing an
embodiment of the invention in the formation of various conducting,
semiconducting and insulating layers defining its circuitry is a
memory device. As one specific example, memory devices may include
layers of titanium nitride as diffusion barrier layers in, for
example, contacts and wordlines.
[0056] Memory Devices
[0057] FIG. 3 is a simplified block diagram of a memory device
according to one embodiment of the invention. The memory device 300
includes an array of memory cells 302, address decoder 304, row
access circuitry 306, column access circuitry 308, control
circuitry 310, and Input/Output circuit 312. The memory can be
coupled to an external microprocessor 314, or memory controller for
memory accessing. The memory receives control signals from the
processor 314, such as WE*, RAS* and CAS* signals. The memory is
used to store data which is accessed via I/O lines. It will be
appreciated by those skilled in the art that additional circuitry
and control signals can be provided, and that the memory device of
FIG. 3 has been simplified to help focus on the invention. The
circuitry of memory device 300 includes at least one CVD-deposited
layer formed in accordance with the invention. For one embodiment,
the CVD-deposited layer formed in accordance with the invention is
a titanium nitride layer.
[0058] It will be understood that the above description of a DRAM
(Dynamic Random Access Memory) is intended to provide a general
understanding of the memory and is not a complete description of
all the elements and features of a DRAM. Further, the invention is
equally applicable to any size and type of memory circuit and is
not intended to be limited to the DRAM described above. Other
alternative types of devices include SRAM (Static Random Access
Memory) or Flash memories. Additionally, the DRAM could be a
synchronous DRAM commonly referred to as SGRAM (Synchronous
Graphics Random Access Memory), SDRAM (Synchronous Dynamic Random
Access Memory), SDRAM II, and DDR SDRAM (Double Data Rate SDRAM),
as well as Synchlink or Rambus DRAMs and other emerging DRAM
technologies.
[0059] Circuit Modules
[0060] As shown in FIG. 4, two or more dies 210 may be combined,
with or without protective casing, into a circuit module 400 to
enhance or extend the functionality of an individual die 210.
Circuit module 400 may be a combination of dies 210 representing a
variety of functions, or a combination of dies 210 containing the
same functionality. One or more dies 210 of circuit module 400
contain at least one CVD-deposited layer formed in accordance with
the invention. For one embodiment, the CVD-deposited layer formed
in accordance with the invention is a titanium nitride layer.
[0061] Some examples of a circuit module include memory modules,
device drivers, power modules, communication modems, processor
modules and application-specific modules, and may include
multilayer, multichip modules. Circuit module 400 may be a
subcomponent of a variety of electronic systems, such as a clock, a
television, a cell phone, a personal computer, an automobile, an
industrial control system, an aircraft and others. Circuit module
400 will have a variety of leads 410 extending therefrom and
coupled to the dies 210 providing unilateral or bilateral
communication and control.
[0062] FIG. 5 shows one embodiment of a circuit module as memory
module 500. Memory module 500 contains multiple memory devices 510
contained on support 515, the number depending upon the desired bus
width and the desire for parity. Memory module 500 accepts a
command signal from an external controller (not shown) on a command
link 520 and provides for data input and data output on data links
530. The command link 520 and data links 530 are connected to leads
540 extending from the support 515. Leads 540 are shown for
conceptual purposes and are not limited to the positions shown in
FIG. 5.
[0063] Electronic Systems
[0064] FIG. 6 shows an electronic system 600 containing one or more
circuit modules 400. Electronic system 600 generally contains a
user interface 610. User interface 610 provides a user of the
electronic system 600 with some form of control or observation of
the results of the electronic system 600. Some examples of user
interface 610 include the keyboard, pointing device, monitor or
printer of a personal computer; the tuning dial, display or
speakers of a radio; the ignition switch, gauges or gas pedal of an
automobile; and the card reader, keypad, display or currency
dispenser of an automated teller machine. User interface 610 may
further describe access ports provided to electronic system 600.
Access ports are used to connect an electronic system to the more
tangible user interface components previously exemplified. One or
more of the circuit modules 400 may be a processor providing some
form of manipulation, control or direction of inputs from or
outputs to user interface 610, or of other information either
preprogrammed into, or otherwise provided to, electronic system
600. As will be apparent from the lists of examples previously
given, electronic system 600 will often contain certain mechanical
components (not shown) in addition to circuit modules 400 and user
interface 610. It will be appreciated that the one or more circuit
modules 400 in electronic system 600 can be replaced by a single
integrated circuit. Furthermore, electronic system 600 may be a
subcomponent of a larger electronic system.
[0065] FIG. 7 shows one embodiment of an electronic system as
memory system 700. Memory system 700 contains one or more memory
modules 500 and a memory controller 710. Memory controller 710
provides and controls a bidirectional interface between memory
system 700 and an external system bus 720. Memory system 700
accepts a command signal from the external bus 720 and relays it to
the one or more memory modules 500 on a command link 730. Memory
system 700 provides for data input and data output between the one
or more memory modules 500 and external system bus 720 on data
links 740.
[0066] FIG. 8 shows a further embodiment of an electronic system as
a computer system 800. Computer system 800 contains a processor 810
and a memory system 700 housed in a computer unit 805. Computer
system 800 is but one example of an electronic system containing
another electronic system, i.e., memory system 700, as a
subcomponent. Computer system 800 optionally contains user
interface components. Depicted in FIG. 8 are a keyboard 820, a
pointing device 830, a monitor 840, a printer 850 and a bulk
storage device 860. It will be appreciated that other components
are often associated with computer system 800 such as modems,
device driver cards, additional storage devices, etc. It will
further be appreciated that the processor 810 and memory system 700
of computer system 800 can be incorporated on a single integrated
circuit. Such single package processing units reduce the
communication time between the processor and the memory
circuit.
CONCLUSION
[0067] Chemical vapor deposition methods utilizing preheating of
one or more of the reactant gases used to form deposited layers,
chemical vapor deposition systems to perform the methods, and
apparatus containing deposited layers produced using the methods
have been described herein. The reactant gases include at least one
chemical vapor deposition precursor. Heating one or more of the
reactant gases prior to introduction to the reaction chamber may be
used to improve physical characteristics of the resulting deposited
layer, to improve the physical characteristics of the underlying
substrate and/or to improve the thermal budget available for
subsequent processing.
[0068] One example includes the formation of a titanium nitride
layer with reactant gases including the precursors of titanium
tetrachloride and ammonia. Preheating these reactant gases prior to
introduction to the reaction chamber can reduce ammonium chloride
levels in the resulting titanium nitride layer, thereby reducing or
eliminating the need for post-processing to remove the ammonium
chloride impurity. Chemical vapor deposition systems as described
herein include one or more heaters to raise the temperature of the
reactant gases prior to introduction to the reaction chamber.
[0069] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that any arrangement which is calculated to achieve the
same purpose may be substituted for the specific embodiments shown.
Many adaptations of the invention will be apparent to those of
ordinary skill in the art. For example, a chemical vapor deposition
system may further include a heater for a carrier gas to raise the
temperature of the carrier gas prior to combination with a
precursor gas or other reactant gas. Furthermore, the heated
carrier gas may be combined with a first, unheated, reactant gas,
with the heated carrier gas supplying the energy input necessary to
raise the temperature of the combined reactant gas to a desired
level in lieu of direct heating of the first reactant gas.
Accordingly, this application is intended to cover any adaptations
or variations of the invention. It is manifestly intended that this
invention be limited only by the following claims and equivalents
thereof.
* * * * *