U.S. patent application number 10/404216 was filed with the patent office on 2004-06-17 for remote icp torch for semiconductor processing.
Invention is credited to Bar-Gadda, Ronny, DePetrillo, Al, Heden, Craig, McGuire, Mickey.
Application Number | 20040115936 10/404216 |
Document ID | / |
Family ID | 22846826 |
Filed Date | 2004-06-17 |
United States Patent
Application |
20040115936 |
Kind Code |
A1 |
DePetrillo, Al ; et
al. |
June 17, 2004 |
Remote ICP torch for semiconductor processing
Abstract
Chemical generators and methods are described for generating a
desired chemical species at or near a point of use such as the
chamber of a reactor in which a workpiece such as a semiconductor
wafer is to be processed. The chemical species is generated by
dissociating precursor materials to create free radicals, and
combining the free radicals, alone or in combination with other
materials, to form the chemical species. An inductively coupled
plasma preferably performs such dissociation.
Inventors: |
DePetrillo, Al; (Folsom,
CA) ; Heden, Craig; (Pacifica, CA) ; McGuire,
Mickey; (Aptos, CA) ; Bar-Gadda, Ronny; (Palo
Alto, CA) |
Correspondence
Address: |
MARTINE & PENILLA, LLP
710 LAKEWAY DRIVE
SUITE 170
SUNNYVALE
CA
94085
US
|
Family ID: |
22846826 |
Appl. No.: |
10/404216 |
Filed: |
March 31, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10404216 |
Mar 31, 2003 |
|
|
|
09225922 |
Jan 5, 1999 |
|
|
|
6579805 |
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Current U.S.
Class: |
438/689 ;
257/E21.252; 257/E21.256 |
Current CPC
Class: |
C01B 21/30 20130101;
G03F 7/427 20130101; C01B 7/191 20130101; C01B 21/26 20130101; H01L
21/31116 20130101; H01L 21/31138 20130101; H05H 1/30 20130101; C01B
33/02 20130101; C01B 17/76 20130101; C01B 7/01 20130101 |
Class at
Publication: |
438/689 |
International
Class: |
H01L 021/302; H01L
021/461 |
Claims
1. An apparatus for semiconductor processing comprising: a tube
having a chamber, a first inlet providing access to the chamber,
and an outlet providing fluidic connectivity between the chamber
and a reactor chamber for semiconductor processing; and a connector
configured to provide turbulence in a flow of a first precursor
material being admitted into the chamber through the first inlet so
as to be uniformly distributed while flowing through the
chamber.
2. The apparatus according to claim 1 further comprising a coil
disposed concentrically around the tube so as to generate an
inductively coupled plasma in the chamber from the precursor
material when energized.
3. The apparatus according to claim 2 wherein the coil is energized
by radio frequency power.
4. The apparatus according to claim 3 wherein the radio frequency
power oscillates at approximately 27.12 MHz.
5. The apparatus according to claim 2 wherein the tube further has
a second inlet providing access to the chamber, and the coil is
aligned with the tube such that the first inlet is on a high
voltage side of the coil and the second inlet is on a grounded side
of the coil so as to result in free radicals generated from the
first precursor material flowing through the first inlet to combine
with molecules of a second material flowing through the second
inlet to form a desired chemical species.
6. The apparatus according to claim 5 wherein the first precursor
material is oxygen, the second material is hydrogen, and the
desired chemical species is steam H.sub.2O.
7. The apparatus according to claim 1 wherein the connector
provides fluidic connectivity between a source of the first
precursor material and the first inlet.
8. The apparatus according to claim 7 wherein the connector is
fluidically connected to the source of the first precursor material
through a delivery hose line.
9. The apparatus according to claim 1 wherein the connector has an
inner wall against which all molecules of the first precursor
material collide before being admitted into the chamber through the
first inlet.
10. The apparatus according to claim 9 wherein the connector is
L-shaped.
11. The apparatus according to claim 1 further comprising a ground
strap contacting the tube so as to inhibit plasma generation in the
chamber beyond the ground strap.
12. An apparatus for semiconductor processing comprising: a tube
having a chamber, first and second inlet ports providing access to
the chamber, and an open end providing access from the chamber to a
reactor chamber for semiconductor processing; and a coil disposed
concentrically around the tube and aligned such that the first
inlet port is on a high voltage side of the coil and the second
inlet port is on a low voltage side of the coil so as to generate
an inductively coupled plasma in the chamber when energized that
results in free radicals generated from a first precursor material
flowing through the first inlet port to combine with molecules of a
second material flowing through the second inlet port to form a
desired chemical species.
13. The apparatus according to claim 12 wherein the inductively
coupled plasma is generated such that it does not extend to the
second inlet port.
14. The apparatus according to claim 12 wherein the first precursor
material is oxygen, the second material is hydrogen, and the
desired chemical species is steam.
15. The apparatus according to claim 12 further comprising a third
inlet port providing access to the chamber on a side of the tube
approximately opposite from the first inlet port on the high
voltage side of the coil so as to admit additional of the first
precursor material into the chamber.
16. The apparatus according to claim 12 further comprising a fourth
inlet port providing access to the chamber on a side of the tube
approximately opposite from the second inlet port on the ground
side of the'coil so as to admit additional of the second material
into the chamber.
17. The apparatus according to claim 12 further comprising a ground
strap contacting the tube so as to inhibit plasma generation in the
chamber beyond the ground strap.
18. An apparatus for semiconductor processing comprising: a tube
having a chamber, an inlet providing access to the chamber, and an
outlet providing fluidic connectivity to a reactor chamber for
processing semiconductors; means for generating a plasma in the
chamber; and a ground strap contacting the tube so as to inhibit
plasma generation in the chamber beyond the ground strap.
19. The apparatus according to claim 18 further comprising a coil
disposed concentrically around the tube so as to generate an
inductively coupled plasma when energized.
20. The apparatus according to claim 19 wherein~the coil is
energized by a radio frequency generator through a matching
network.
21. The apparatus according to claim 19 wherein the ground strap is
positioned on the tube on a ground side of the coil.
22. The apparatus according to claim 21 wherein the ground strap
includes copper material.
23. An apparatus for semiconductor processing comprising: a first
free radical source for generating a first type of free radicals
from a first precursor material and providing the first type of
free radicals to a reactor chamber, and a second free source for
generating a second type of free radicals from a second precursor
material and providing the second type of free radicals to the
reactor chamber for combination with the first type of free
radicals to form a desired chemical species for processing
semiconductors in the reactor chamber.
24. The apparatus according to claim 23 wherein the first free
radical source comprises: a first tube having a first chamber; and
a first coil disposed concentrically around the first tube so as to
generate a first inductively coupled plasma generating the first
type of free radicals from the first precursor material when
energized.
25. The apparatus according to claim 24 wherein the second free
radical source comprises: a second tube having a second chamber;
and a second coil disposed concentrically around the second tube so
as to generate a second inductively coupled plasma generating the
second type of free radicals from the second precursor material
when energized.
26. The apparatus according to claim 24 wherein the first coil is
coupled to a first radio frequency generator through a first
matching network.
27. The apparatus according to claim 26 wherein the second coil is
coupled to the first radio frequency generator through the first
matching network.
28. The apparatus according to claim 26 wherein the second coil is
coupled to a second radio frequency generator through a second
matching network.
29. The apparatus according to claim 26 wherein the second coil is
coupled to the first radio frequency generator through a third
matching network.
Description
[0001] This application is a continuation-in-part of commonly-owned
U.S. patent application Ser. No. 09/225,922, filed Jan. 5, 1999,
which is incorporated herein by this reference to the extent
consistent herewith.
[0002] This invention pertains generally to the fabrication of
semiconductor devices and, more particularly, to a method and
apparatus for generating important chemical species in the
deposition, etching, cleaning, and growth of various materials and
layers.
[0003] It is in general an object of the invention to provide a new
and improved chemical generator and method for generating chemical
species at or near the location where they are to be used.
[0004] Another object of the invention is to provide a chemical
generator and method of the above character which are particularly
suitable for generating chemical species for use in the fabrication
of semiconductor devices.
[0005] These and other objects are achieved in accordance with the
invention by providing a chemical generator and method for
generating a chemical species at or near a point of use such as the
chamber of a reactor in which a workpiece such as a semiconductor
wafer is to be processed. The species is generated by creating free
radicals, and combining the free radicals, alone or with other
materials, to form the chemical species.
[0006] FIG. 1 is a diagrammatic view of a chemical generator
incorporating aspects of-the invention.
[0007] FIG. 2 is a cross-sectional view taken along line 2-2 of
FIG. 1.
[0008] FIG. 3 is a diagrammatic view of another version of the
chemical generator incorporating aspects of the invention.
[0009] FIG. 4 is a diagrammatic view of a remote ICP torch
incorporating aspects of the invention.
[0010] As illustrated in FIG. 1, a chemical generator includes a
free radical source 11 which has one or more chambers in which free
radicals are created and delivered for recombination into stable
species. In the embodiment illustrated, the source has three
chambers which are formed by elongated, concentric tubes 12-14.
Those chambers include a first annular chamber 16 between the
outermost tube 12 and the middle tube 13, a second annular chamber
17 between middle tube 13 and the innermost tube 14, and a third
chamber 18 inside the innermost tube 14. The tubes are fabricated
of a material such as ceramic or quartz.
[0011] The number of tubes which are required in the generator is
dependent upon the chemical species being generated and the
reaction by which it is formed, with a separate chamber usually,
but not necessarily, being provided for each type of free radical
to be used in the process.
[0012] Gases or other precursor compounds from which the free
radicals are formed are introduced into the chambers from sources
21-23 or by other suitable means. Such precursors can be in
gaseous, liquid and/or solid form, or a combination thereof.
[0013] As previously explained, although a separate chamber may be
used for providing each type of free radicals, it is also
contemplated for certain chemical reactions such as described below
that a single chamber may also be used for providing more than one
type of free radicals. In such a case, gases or other precursor
compounds from which the more than one type of free radicals are
formed are introduced into the single chamber from corresponding
sources.
[0014] A plasma is formed within the one or more chambers to create
the free radicals, and in the embodiment illustrated, the means for
generating the plasma includes an induction coil 26 disposed
concentrically about the one or more tubes, a radio frequency (RF)
power generator 27 connected to the coil by a matching network 28,
and a Tesla coil 29 for striking an arc to ignite the plasma. The
plasma can, however, be formed by any other suitable means such as
RF electrodes or microwaves.
[0015] In the embodiment illustrated, the free radicals are
recombined to form the desired species downstream of the tubes. In
this case, recombination takes place in a chamber 31 which is part
of a reactor 32 in which a semiconductor wafer 33 is being
processed. Recombination can be promoted by any suitable means such
as by cooling 36 and/or by the use of a catalyst 37.
[0016] Cooling can be effected in a number of ways, including the
circulation of a coolant such as an inert gas, liquid nitrogen,
liquid helium or cooled water through tubes or other suitable means
in heat exchange relationship with the reacting gases.
[0017] A catalyst can be placed either in the cooling zone or
downstream of it. It can, for example, be in the form of a thin
film deposited on the wall of a chamber or tube through which the
reacting gases pass, a gauze placed in the stream of gas, or a
packed bed. The important thing is that the catalyst is situated in
such a way that all of the gas is able to contact its surface and
react with it.
[0018] If desired, monitoring equipment such as an optical emission
spectrometer can be provided for monitoring parameters such as
species profile and steam generation.
[0019] In the embodiment illustrated in FIG. 1, the chemical
generator is integrated with the reactor, and the species produced
is formed in close proximity to the wafer being processed. That is
the preferred application of the generator, although it can also be
used in stand-alone applications as well. It can be added to
existing process reactors as well as being constructed as an
integral part of new reactors, or as a stand-alone system.
[0020] FIG. 3 illustrates another version of the chemical
generator. In the embodiment illustrated, a chemical generator
includes a free radical source 300 which has two chambers in which
free radicals are created and delivered for recombination into
stable species. In the embodiment illustrated, the source has two
chambers which are respectively formed within elongated tubes 312
and 313. Those chambers include a first chamber inside tube 312 and
a second chamber inside tube 313. The tubes are preferably
fabricated of a material such as quartz or ceramic.
[0021] In the tubes depicted in FIG. 3, a separate chamber is
provided to generate each type of free radical to be used in the
process. This approach ensures that the free radicals will not
recombine to form the desired chemical species until after they are
introduced into the reactor 331. In the tube depicted in FIG. 4,
however, more than one type of free radical may be generated in the
tube. In this latter approach, recombination of free radicals to
form the desired chemical species may occur within the tube as
well.
[0022] The free radicals are generated from precursor materials
which are introduced into the chambers of tubes 312 and 313
respectively from, for example, first and second precursor sources
322 and 323. The precursor materials can be in gaseous, liquid
and/or solid form, or a combination thereof.
[0023] Plasmas are formed within the chambers to create the free
radicals, and in the embodiment illustrated, the means for
generating the plasmas includes an induction coil 332 disposed
concentrically about tube 312, another induction coil 333 disposed
concentrically about tube 313, and a radio frequency (RF) power
generator 327 connected to the coils 332 and 333 by a matching
network 328. Although this embodiment shows the coils 332 and 333
sharing the same RF power generator 327 and matching network 328,
an alternative embodiment, fully contemplated but not shown herein
to avoid unnecessary duplication or straightforward elaboration of
details, includes each of the coils 332 and 333 having its own RF
power generator and/or matching network. A Tesla coil (not shown)
for striking an arc to ignite each of the plasmas may also be
included if useful. Although shown as being generated through RF
energized induction coils, the plasmas can also be formed by any
other suitable means such as RF electrodes or microwaves.
[0024] Insulation housings 342 and 343 conventionally protect
adjacent computer and other circuitry from electromagnetic fields
induced by energized coils 332 and 333, as well as preventing such
induced electromagnetic fields from interfering or otherwise
interacting with each other or the plasmas generated therefrom.
[0025] In the embodiment illustrated, the free radicals are
recombined to form the desired species downstream of the tubes. In
this case, recombination takes place in a chamber 331 which is part
of a reactor 332 in which a semiconductor wafer 333 is being
processed. Recombination can be promoted, if necessary, by any
suitable means such as by cooling (not shown) and/or by the use of
a catalyst (not shown).
[0026] As an example of the use of this embodiment of a chemical
generator, the formation of steam (H.sub.2O) is described. In this
example, the first precursor source 322 provides H.sub.2 gas which
is admitted into the chamber of tube 312 and the second precursor
source 323 provides O.sub.2 gas which is admitted into the chamber
of tube 313. Plasmas are created in both chambers, and as a result,
hydrogen and oxygen free radicals are respectively generated and
provided to the chamber 331. Within the reactor chamber 331, these
free radicals recombine to form steam (H.sub.2O), which in turn,
may be used, for example, to produce SiO.sub.2 on the exposed
surface of the semiconductor wafer 333.
[0027] As illustrated in FIG. 4, a remote inductively coupled
plasma (ICP) source (or "torch") includes a free radical source 400
having a tube 401 with a closed end 411 and an open end 412. The
open end (or outlet port) 412 is to be fluidically connected to a
reactor chamber for processing semiconductors. The torch is
referred to as being "remote" in this case, because it creates a
plasma that is outside of the reactor chamber. The tube is
preferably made of ultra-pure quartz (such as GE 214), or
alternatively, of some other material commonly used for such
purposes, such as ceramic.
[0028] A coil 430 is disposed concentrically about the tube 401 and
aligned such that the high voltage or "hot" side of the coil 430 is
closest to the closed end 411 of the torch, and the grounded end of
the coil 430 is closest to the open end 412 of the torch. In this
example, the coil 430 is depicted as a 4-turn coil made of suitable
material such as gold-plated copper tubing.
[0029] A radio frequency (RF) power generator 480 is connected to
the coil 430 by a matching network 481. The matching network 481 is
used to adjust the overall impedance of the torch and coil assembly
to couple (i.e., resonate in phase) with the 50 ohm output
impedance of the RF power generator 480. The RF power generator 480
delivers, as an example, up to 5 kW of forward power to the
matching network 481 at a fixed frequency of approximately 27.12
MHz.
[0030] Inlet ports 440 and 450 made from similar material as the
tube 401 are fused into the tube's inner chamber walls between its
closed end 411 and the "hot" side of the coil 430, and inlet ports
460 and 470 also made from similar material as the tube 401 are
fused into the tube's inner chamber walls between its open end 412
and the grounded end of the coil 430. Connectors 441, 451, 561, and
471 made of, for examples, Teflon, PFA, or ceramic, are clamped to
the ends of respective inlet ports 440, 450, 460, and 470 to serve
as connectors for respective delivery hose lines 443, 453, 463, and
473.
[0031] The connectors 441, 451, 461, and 471 cause turbulence in
the flow of precursor materials passing through them as the flow of
molecules collide with and scatter from the inner walls 442, 452,
462, and 472 of their L-shaped bends. As a result of such
turbulence, the density of the precursor materials flowing into and
through the chamber of tube 401 has high uniformity, which is
useful for controlling plasma generation in the tube 401. Although
the connectors 441, 451, 461, and 471 depict 90 degree bends, it is
to be appreciated that the angle of the bend may be other values as
long as the molecules in the flow of precursor material strike at
least one wall in the connector/inlet port combination so as to
increase the turbulence in the flow before entering the chamber of
the tube 401.
[0032] Precursor and/or other materials are provided to one or more
of the inlet ports 440, 450, 460, and 470 by corresponding of the
sources 444, 454, 464, and 474 through corresponding delivery hose
lines and connectors. The type or types of materials to be provided
and the inlet ports through which they are to be provided generally
depend upon the reaction used to generate a desired chemical
species.
[0033] As one example, steam (H.sub.2O) can be generated in the
chemical generator (or further down the line of flow towards or in
the reactor chamber) by providing O.sub.2 gas at inlet port 440 and
H.sub.2 gas at inlet port 450, with no materials provided to inlet
ports 460 and 470. In this case, hydrogen and oxygen free radicals
are generated by the induced plasmas respectively from the H.sub.2
and O.sub.2 gases, and then recombined to form the desired chemical
species of steam (H.sub.2O).
[0034] As another example, steam (H.sub.2O) can also be generated
in the chemical generator (or further down the line of flow towards
or in the reactor chamber) by providing O.sub.2 gas at inlet port
440 (and optionally, also at inlet port 450 to improve uniformity
of the gas density in the tube 401) and H.sub.2 gas at inlet port
460 (and optionally, also at inlet port 470). In this case, oxygen
free radicals are generated by the induced plasma from the O.sub.2
gas, and then combined with the H.sub.2 gas molecules provided just
outside the induced plasma to form the desired chemical species of
steam (H.sub.2O).
[0035] A ground strap 490 is mounted in direct contact with the
tube 401 at a strategic position between the grounded end of the
coil and the open end of the tube 401 to inhibit plasma generation
in the chamber beyond the ground strap 490 and preferably restrict
plasma generation to the immediate or near vicinity of the coil
430. The ground strap 490 is preferably made of copper or other
highly conductive material.
[0036] The chemical generators described herein can be employed in
a wide variety of applications for generating different species for
use in the fabrication of semiconductor devices, some examples of
which are given below.
Oxidation
[0037] Steam for use in a wet oxidation process for producing
SiO.sub.2 according to the reaction
Si+H.sub.2O.fwdarw.SiO.sub.2+H.sub.2
[0038] can be generated in accordance with the invention by
admitting H.sub.2 and O.sub.2 into one of the plasma generating
chambers. When the plasma is energized, the H.sub.2 and O.sub.2
react to form steam in close proximity to the silicon wafer. If
desired, oxygen admitted alone or with N.sub.2 and/or Ar can be
used to produce ozone (O.sub.3) to lower the temperature for
oxidation and/or improve device characteristics.
[0039] It is known that the use of NO in the oxidation of silicon
with O.sub.2 can improve the device characteristics of a transistor
by improving the interface between silicon and silicon oxide which
functions as a barrier to boron.
[0040] Conventionally, NO is supplied to the reactor chamber from a
source such as a cylinder, and since NO is toxic, special
precautions must be taken to avoid leaks in the gas lines which
connect the source to the reactor. Also, the purity of the NO gas
is a significant factor in the final quality of the interface
formed between the silicon and the silicon oxide, but it is
difficult to produce extremely pure NO.
[0041] With the invention, highly pure NO can be produced at the
point of use through the reaction
N.sub.2+O.sub.2.fwdarw.2NO
[0042] by admitting N.sub.2 and O.sub.2 to one of the chambers and
striking a plasma. When the plasma is struck, the N.sub.2 and
O.sub.2 combine to form NO in close proximity to the wafer. Thus,
NO can be produced only when it is needed, and right at the point
of use, thereby eliminating the need for expensive and potentially
hazardous gas lines.
[0043] NO can also be produced by other reactions such as the
cracking of a molecule containing only nitrogen and oxygen, such as
N.sub.2O. The NO is produced by admitting N.sub.2O to the plasma
chamber by itself or with O.sub.2. If desired, a gas such as Ar can
be used as a carrier gas in order to facilitate formation of the
plasma.
[0044] N.sub.2O can also be cracked either by itself or with a
small amount of O.sub.2 to form NO.sub.2, which then dissociates to
NO and O.sub.2. In rapid thermal processing chambers and diffusion
furnaces where temperatures are higher than the temperature for
complete dissociation of NO.sub.2 to NO and O.sub.2 (620.degree.
C.), the addition of NO.sub.2 will assist in the oxidation of
silicon for gate applications where it has been found that nitrogen
assists as a barrier for boron diffusion. At temperatures below
650.degree. C., a catalyst can be used to promote the conversion of
NO.sub.2 to NO and O.sub.2. If desired, nitric acid can be
generated by adding water vapor or additional H.sub.2 and O.sub.2in
the proper proportions.
[0045] Similarly, NH.sub.3 and O.sub.2 can be combined in the
plasma chamber to produce NO and steam at the point of use through
the reaction
NH.sub.3+O.sub.2.fwdarw.NO+H.sub.2O
[0046] By using these two reagent gases, the efficacy of NO in the
wet oxidation process can be mimicked.
[0047] It is often desired to include chlorine in an oxidation
process because it has been found to enhance oxidation as well as
gettering unwanted foreign contaminants. Using any chlorine source
such as TCA or DCE, complete combustion can be achieved in the
presence of O.sub.2, yielding HCl+H.sub.2O+CO.sub.2. Using chlorine
alone with H.sub.2 and O.sub.2 will also yield HCl and
H.sub.2O.
[0048] When TCA or DCE is used in oxidation processes, it is
completely oxidized at temperatures above 700.degree. C. to form
HCl and carbon dioxide in reactions such as the following:
C.sub.2H.sub.3Cl.sub.3+2O.sub.2.fwdarw.2CO.sub.2+3HCl
C.sub.2H.sub.2Cl.sub.2+2O.sub.2.fwdarw.2CO.sub.2+2HCl
[0049] The HCl is further oxidized in an equilibrium reaction:
4HCl=O.sub.2.fwdarw.2H.sub.2O+Cl.sub.2
[0050] Decomposition of various organic chlorides with oxygen at
elevated temperatures provides chlorine and oxygen-containing
reagents for subsequent reactions in, e.g., silicon processing.
Such decomposition is generally of the form
C.sub.xH.sub.yCl.sub.y+xO.sub.2.fwdarw.xCO.sub.2+yHCl
[0051] where x and y are typically 2, 3 or 4.
[0052] All of the foregoing reactions can be run under either
atmospheric or subatmospheric conditions, and the products can be
generated with or without a catalyst such as platinum.
[0053] The invention can also be employed in the cleaning of quartz
tubes for furnaces or in the selective etching or stripping of
nitride or polysilicon films from a quartz or silicon oxide layer.
This is accomplished by admitting a reactant containing fluorine
and chlorine such as a freon gas or liquid, i.e.
C.sub.xH.sub.yF.sub.zCl.sub.q, where
X=1, 2, . . .
Y=0, 1, . . .
Z=0, 1, . . .
Q=0, 1, . . .
[0054] and the amount of fluorine is equal to or greater than the
amount of chlorine. It is also possible to use a mixture of
fluorinated gases (e.g., CHF.sub.3, CF.sub.4, etc.) and chlorinated
liquids (e.g., CHCl.sub.3, CCl.sub.4, etc.) in a ratio which
provides effective stripping of the nitride or polysilicon
layer.
Dielectric Films
[0055] Other dielectric films can be formed from appropriate
precursor gases. Polysilicon can be formed using SiH.sub.4 and
H.sub.2, or silane alone. The silane may be introduced downstream
of the generator to avoid nucleation and particle formation.
[0056] Silicon nitride can be formed by using NH.sub.3 or N.sub.2
with silane (SiH.sub.4) or one of the higher silanes, e.g.
Si.sub.2H.sub.6. The silane can be introduced downstream of the
generator to avoid nucleation and particle formation.
[0057] In addition to gases, the chemical generator is also capable
of using liquids and solids as starting materials, so that
precursors such as TEOS can be used in the formation of conformal
coatings. Ozone and TEOS have been found to be an effective mixture
for the deposition of uniform layers.
Metal and Metal Oxide Films
[0058] Metal and metal oxide films can be deposited via various
precursors in accordance with the invention. For example,
Ta.sub.2O.sub.5 films which are used extensively in memory devices
can be formed by generating a precursor such as TaCl.sub.5 via
reduction of TaCl.sub.5, followed by oxidation of the TaCl.sub.5 to
form Ta.sub.2O.sub.5. In a more general sense, the precursor from
which the Ta.sub.2O.sub.5 is generated can be expressed as
T.sub.aX.sub.m, where x is a halogen species, and m is the
stoichiometric number.
[0059] Copper can be deposited as a film or an oxide through the
reaction
CuCl.sub.2+H.sub.2.fwdarw.Cu+HCl
[0060] and other metals can be formed in the same way. Instead of a
gaseous precursor, a solid precursor such as Cu or another metal
can also be used.
Wafer and Chamber Cleaning
[0061] With the invention, organic residue from previous process
steps can be effectively removed by using O.sub.2 to form ozone
which is quite effective in the removal of organic contaminants. In
addition, reacting H.sub.2 with an excess of O.sub.2 will produce
steam and O.sub.2 as well as other oxygen radicals, all of which
are effective in eliminating organic residue. The temperature in
the chamber should be below about 700.degree. C. if a wafer is
present, in order to prevent oxide formation during the cleaning
process.
[0062] Sulfuric acid, nitric acid and hydrofluoric acid for use in
general wafer cleaning are also effectively produced with the
invention. Sulfuric acid (H.sub.2SO.sub.4) is generated by reacting
either S, SO or SO.sub.2 with H.sub.2 and O.sub.2 in accordance
with reactions such as the following:
S+2.5O.sub.2+2H.sub.2.fwdarw.H.sub.2SO.sub.4+H.sub.2O
SO+1.5O.sub.2+H.sub.2.fwdarw.H.sub.2SO.sub.4
SO.sub.2+1.5O.sub.2+2H.sub.2.fwdarw.H.sub.2SO.sub.4+H.sub.2O
[0063] then quickly quenching the free radicals thus formed with or
without a catalyst.
[0064] Nitric acid (HNO.sub.3) is generated by reacting NH.sub.3
with H.sub.2 and O.sub.2, or by a reaction such as the
following:
N.sub.2+3.5O.sub.2+H.sub.2.fwdarw.2HNO.sub.3+H.sub.2O
NH.sub.3+2O.sub.2.fwdarw.2HNO.sub.3+H.sub.2O
[0065] Hydrofluoric acid is generated by co-reacting H.sub.2 and
O.sub.2 with a compound containing fluorine such as NF.sub.3 or
C.sub.xH.sub.yF.sub.z, where
X=1, 2,
Y=0, 1,
Z=1, 2,
[0066] Mixed acids can be generated from a single precursor by
reactions such as the following:
SF.sub.6+4H.sub.2+2O.sub.2.fwdarw.H.sub.2SO.sub.4+6HF
NH.sub.2+H.sub.2+1.5O.sub.2.fwdarw.HNO.sub.3+HF
2NHF+H.sub.2+3O.sub.2.fwdarw.2HNO.sub.3+2HF
NF.sub.3O+2H.sub.2+O.sub.2.fwdarw.HNO.sub.3+3HF
NF.sub.2Cl+2H.sub.2+1.5O.sub.2.fwdarw.HNO.sub.3+2HF+HCl
N.sub.2F.sub.4+3H.sub.2+3O.sub.2.fwdarw.2HNO.sub.3+4HF
N.sub.2F.sub.4+2H.sub.2+3O.sub.2.fwdarw.2HNO.sub.3+2HF
NF.sub.3+2H.sub.2+1.5O.sub.2.fwdarw.HNO.sub.3+3HF
NF.sub.2+1.5H.sub.2+1.5O.sub.2.fwdarw.HNO.sub.3+2HF
NF+H.sub.2+1.5O.sub.2.fwdarw.HNO.sub.3+HF
NS+1.5H.sub.2+3.5O.sub.2.fwdarw.HNO.sub.3+H.sub.2SO.sub.4
2N.sub.2OF+2H.sub.2+O.sub.2.fwdarw.2HNO.sub.3+2HF
NOF.sub.3+2H.sub.2+O.sub.2.fwdarw.HNO.sub.3+3HF
NOF+H.sub.2+O.sub.2.fwdarw.HNO.sub.3+HF
NOCl+H.sub.2+O.sub.2.fwdarw.HNO.sub.3+HCl
NOBr+H.sub.2+O.sub.2.fwdarw.HNO.sub.3+HBr
NO2Cl+2H.sub.2+O.sub.2.fwdarw.2HNO.sub.3+HCl
S.sub.2F.sub.1O+7H.sub.2+4O.sub.2.fwdarw.H.sub.2SO.sub.4+10HF
S.sub.2F.sub.2+3H.sub.2+4O.sub.2.fwdarw.H.sub.2SO.sub.4+2HF
SF+1.5H.sub.2+2O.sub.2.fwdarw.H.sub.2SO.sub.4+HF
SF.sub.2+2H.sub.2+2O.sub.2.fwdarw.H.sub.2SO.sub.4+2HF
SF.sub.3+2.5H.sub.2+2O.sub.2.fwdarw.H.sub.2SO.sub.4+3HF
SF.sub.4+3H.sub.2+2O.sub.2.fwdarw.H.sub.2SO.sub.4+4HF
SF.sub.5+3.5H.sub.2+2O.sub.2.fwdarw.H.sub.2SO.sub.4+5HF
SF.sub.6+4H.sub.2+2O.sub.2.fwdarw.H.sub.2SO.sub.4+6HF
SBrF.sub.5+4H.sub.2+2O.sub.2.fwdarw.H.sub.2SO.sub.4+5HF+HBr
S.sub.2Br.sub.2+3H.sub.2+4O.sub.2.fwdarw.2H.sub.2SO.sub.4+2HBr
SBr.sub.2+2H.sub.2+2O.sub.2.fwdarw.H.sub.2SO.sub.4+2HBr
SO.sub.2F.sub.2+2H.sub.2+O.sub.2.fwdarw.H.sub.2SO.sub.4+2HF
SOF.sub.4+3H.sub.2+1.5O.sub.2.fwdarw.H.sub.2SO.sub.4+4HF
SOF.sub.2+2H.sub.2+1.5O.sub.2.fwdarw.H.sub.2SO.sub.4+2HF
SOF+1.5H.sub.2+1.5O.sub.2.fwdarw.H.sub.2SO.sub.4+HF
SO.sub.2ClF+2H.sub.2+O.sub.2.fwdarw.H.sub.2SO.sub.4+HF+HCl
SOCl.sub.2+2H.sub.2+1.5O.sub.2.fwdarw.H.sub.2SO.sub.4+2HCl
SOCl+1.5H.sub.2+1.5O.sub.2.fwdarw.H.sub.2SO.sub.4+HCl
SOBr.sub.2+2H.sub.2+1.5O.sub.2.fwdarw.H.sub.2SO.sub.4+2HBrCl
SF.sub.2Cl+2.5H.sub.2+2O.sub.2.fwdarw.H.sub.2SO.sub.4+2HF+HCl
SClF.sub.5+4H.sub.2+2O.sub.2.fwdarw.H.sub.2SO.sub.4+5HF+HCl
SO.sub.2Cl.sub.2+2H.sub.2+O.sub.2.fwdarw.H.sub.2SO.sub.4+2HCl
S.sub.2Cl+2.5H.sub.2+4O.sub.2.fwdarw.2H.sub.2SO.sub.4+HCl
SCl.sub.2+2H.sub.2+2O.sub.2.fwdarw.H.sub.2SO.sub.4+2HCl
[0067] These are but a few examples of the many reactions by which
mixed acids can be generated in accordance with the invention.
Including more H.sub.2 and O.sub.2 in the reactions will allow
steam to be generated in addition to the mixtures of acids.
[0068] In order to devolitize the various resultant products of the
reaction of HCl, HF, H.sub.2SO.sub.4 or HNO.sub.3, either H.sub.2O
or H.sub.2 and O.sub.2 can be co-injected to form steam so that the
solvating action of water will disperse in solution in the
products. The temperature of the water must be cool enough so that
a thin film of water will condense on the wafer surface. Raising
the temperature of the water will evaporate the water solution, and
spinning the wafer will further assist in the removal process.
Native Oxide Removal
[0069] The native oxide which is ever present when a silicon wafer
is exposed to the atmosphere can be selectively eliminated by a
combination of HF and steam formed by adding a fluorine source such
as NF.sub.3 or CF.sub.4 to the reagent gases H.sub.2 and O.sub.2.
In order for the native oxide elimination to be most effective, the
reaction chamber should be maintained at a pressure below one
atmosphere.
Photoresist Stripping
[0070] H.sub.2 and O.sub.2 can also be reacted to form steam for
use in the stripping of photoresist which is commonly used in
patterning of silicon wafers in the manufacture of integrated
circuits. In addition, other components such as HF, H.sub.2SO.sub.4
and HNO.sub.3 which are also generated with the invention can be
used in varying combinations with the steam to effectively remove
photoresist from the wafer surface. Hard implanted photoresist as
well as residues in vias can also be removed with steam in
combination with these acids.
[0071] SO.sub.3 for use in the stripping of organic photoresist can
be generated by adding O.sub.2 to SO.sub.2. Similarly, as discussed
above, N.sub.2O can be converted to NO.sub.2, a strong oxidizing
agent which can also be used in the stripping of photoresist.
[0072] Hydrofluoric acid for use in the stripping of photoresist
can be generated in situ in accordance with any of the following
reactions:
CF.sub.4+2H.sub.2+O.sub.2.fwdarw.+CO.sub.2+4HF
4CF.sub.4+3H.sub.2+1.5O.sub.2CO.sub.2+4HF+H.sub.2O
NF.sub.3+5H.sub.2+O.sub.2.fwdarw.N.sub.2+6HF+2H.sub.2O
[0073] It is apparent from the foregoing that a new and improved
chemical generator and method have been provided. While only
certain presently preferred embodiments have been described in
detail, as will be apparent to those familiar with the art, certain
changes and modifications can be made without departing from the
scope of the invention as defined by the following claims.
* * * * *