U.S. patent application number 12/842006 was filed with the patent office on 2011-01-27 for carbon materials for carbon implantation.
This patent application is currently assigned to Advanced Technology Materials, Inc.. Invention is credited to Oleg BYL, Robert KAIM, Joseph D. SWEENEY.
Application Number | 20110021011 12/842006 |
Document ID | / |
Family ID | 43497679 |
Filed Date | 2011-01-27 |
United States Patent
Application |
20110021011 |
Kind Code |
A1 |
SWEENEY; Joseph D. ; et
al. |
January 27, 2011 |
CARBON MATERIALS FOR CARBON IMPLANTATION
Abstract
A method of implanting carbon ions into a target substrate,
including: ionizing a carbon containing dopant material to produce
a plasma having ions; optionally co-flowing an additional gas or
series of gases with the carbon-containing dopant material; and
implanting the ions into the target substrate. The
carbon-containing dopant material is of the formula
C.sub.wF.sub.xO.sub.yH.sub.z wherein if w=1, then x>0 and y and
z can take any value, and wherein if w>1 then x or y is >0,
and z can take any value. Such method significantly improves the
efficiency of an ion implanter tool, in relation to the use of
carbon source gases such as carbon monoxide or carbon dioxide.
Inventors: |
SWEENEY; Joseph D.;
(Winsted, CT) ; BYL; Oleg; (Southbury, CT)
; KAIM; Robert; (Brookline, MA) |
Correspondence
Address: |
INTELLECTUAL PROPERTY / TECHNOLOGY LAW
PO BOX 14329
RESEARCH TRIANGLE PARK
NC
27709
US
|
Assignee: |
Advanced Technology Materials,
Inc.
Danbury
CT
|
Family ID: |
43497679 |
Appl. No.: |
12/842006 |
Filed: |
July 22, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61227875 |
Jul 23, 2009 |
|
|
|
Current U.S.
Class: |
438/515 ;
257/E21.334 |
Current CPC
Class: |
C23C 14/06 20130101;
H01L 21/2236 20130101; C23C 14/0605 20130101; H01J 37/3171
20130101; H01L 21/265 20130101; H01J 2237/31701 20130101; H01J
2237/08 20130101; C23C 14/48 20130101 |
Class at
Publication: |
438/515 ;
257/E21.334 |
International
Class: |
H01L 21/265 20060101
H01L021/265 |
Claims
1. A method of implanting a carbon ion into a target substrate,
comprising: ionizing a carbon-containing dopant material to produce
a plasma having ions; and implanting the ions into the target
substrate; wherein the carbon-containing dopant material is of the
formula C.sub.wF.sub.xO.sub.yH.sub.z wherein if w=1, then x>0
and y and z can take any value, and wherein if w>1 then x or y
is >0, and z can take any value.
2. The method of claim 1, wherein the ions of the plasma produced
are of the form C.sub.aF.sub.bO.sub.cH.sub.d.sup.+, wherein a>0,
and b, c, and d can have any value.
3. The method of claim 1, wherein upon ionizing the
carbon-containing dopant material, the carbon ions are clustered in
groups of at least two carbon atoms.
4. The method of claim 1, wherein the carbon-containing dopant
material is COF.sub.2.
5. The method of claim 1, further comprising selecting the ratios
of w, x, y, and z to produce a feed material of the formula
C.sub.wF.sub.xO.sub.yH.sub.z prior to the step of ionizing to
produce the plasma.
6. The method of claim 1, further comprising co-flowing an
additional gas or series of gases with the carbon-containing dopant
material, the additional gas comprising one or more of carbon,
oxygen, fluorine, hydrogen, nitrogen, argon, xenon, air, and
helium.
7. A method of implanting carbon ions into a target substrate,
comprising: ionizing a carbon-containing dopant material to produce
a plasma having ions; co-flowing an additional gas or series of
gases with the carbon-containing dopant material; and implanting
the ions into the target substrate; wherein the carbon-containing
dopant material is of the formula C.sub.wF.sub.xO.sub.yH.sub.z.
8. The method of claim 7, wherein the ions of the plasma produced
are of the form C.sub.aF.sub.bO.sub.cH.sub.d.sup.+, wherein a>0,
and b, c, and d can have any value.
9. The method of claim 7, wherein upon ionizing the
carbon-containing dopant material, the carbon ions are clustered in
groups of at least two carbon atoms.
10. The method of claim 7, wherein the carbon-containing dopant
material is COF.sub.2 gas.
11. The method of claim 7, further comprising selecting the desired
additional gas or series of gases and desired ratios of w, x, y,
and z to produce a feed material of the formula
CC.sub.wF.sub.xO.sub.yH.sub.z, prior to the step of ionizing to
produce the plasma.
12. The method of claim 7, wherein the additional gas comprises one
or more of carbon, oxygen, fluorine, hydrogen, nitrogen, argon,
xenon, air, and helium.
13. A method of improving the efficiency of an ion implanter tool,
comprising: selecting a carbon-containing dopant material of the
formula C.sub.wF.sub.xO.sub.yH.sub.z for use in the ion implanter
tool in a chamber, wherein if w=1, then x>0 and y and z can take
any value, and wherein if w>1 then x or y is >0, and z can
take any value; ionizing the carbon-containing dopant material; and
implanting a carbon ion from the ionized carbon-containing dopant
material using the ion implanter tool; wherein the selecting of the
material of the formula C.sub.wF.sub.xO.sub.yH.sub.z minimizes the
amount of carbon and/or non-carbon elements deposited in the
chamber after the implanting of the carbon ion.
14. The method of claim 13, wherein the carbon-containing dopant
material is COF.sub.2.
15. The method of claim 13, further comprising providing an
additional material with the carbon-containing dopant material.
16. The method of claim 13, wherein the ions of the plasma produced
are of the form C.sub.aF.sub.bO.sub.cH.sub.d.sup.+, wherein a>0,
and b, c, and d can have any value.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The benefit of priority to U.S. Provisional Patent
Application No. 61/227,875 filed Jul. 23, 2009 in the names of
Joseph D. Sweeney, Oleg Byl and Robert Kaim for "Carbon Materials
for Carbon Implantation" is hereby claimed under 35 USC 119. The
disclosure of such U.S. Provisional Patent Application No.
61/227,875 is hereby incorporated herein by reference, in its
entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to ion implantation methods
and systems, and more particularly, to carbon materials for carbon
ion implantation in such systems.
BACKGROUND
[0003] Ion implantation is used in integrated circuit fabrication
to accurately introduce controlled amounts of dopant impurities
into semiconductor wafers and is one of the processes of
microelectronic/semiconductor manufacturing. In such implantation
systems, an ion source ionizes a desired dopant element gas, and
the ions are extracted from the source in the form of an ion beam
of desired energy. Extraction is achieved by applying a high
voltage across suitably-shaped extraction electrodes, which
incorporate apertures for passage of the extracted beam. The ion
beam is then directed at the surface of a workpiece, such as a
semiconductor wafer, in order to implant the workpiece with the
dopant element. The ions of the beam penetrate the surface of the
workpiece to form a region of desired conductivity.
[0004] Several types of ion sources are used in ion implantation
systems, including the Freeman and Bernas types that employ
thermoelectrodes and are powered by an electric arc, microwave
types using a magnetron, indirectly heated cathode (IHC) sources,
and RF plasma sources, all of which typically operate in a vacuum.
In any system, the ion source generates ions by introducing
electrons into a vacuum arc chamber (hereinafter "chamber") filled
with the dopant gas (commonly referred to as the "feedstock gas").
Collisions of the electrons with atoms and molecules in the dopant
gas result in the creation of ionized plasma consisting of positive
and negative dopant ions. An extraction electrode with a negative
or positive bias will respectively allow the positive or negative
ions to pass through an aperture as a collimated ion beam, which is
accelerated towards the target material.
[0005] In many ion implantation systems, carbon, which is known to
inhibit diffusion, is implanted into the target material to produce
a desired effect in the integrated circuit device. The carbon is
generally implanted from a feedstock gas such as carbon monoxide or
carbon dioxide. The use of carbon monoxide or carbon dioxide gases
can result in oxidation of the metal surfaces within the plasma
source (arc chamber) of the ion implanter tool, and can also result
in carbon residues depositing on electrical insulators. These
phenomena reduce the performance of the implanter tool, thereby
resulting in the need to perform frequent maintenance. Oxidation
can result in inefficiencies in the implantation process.
[0006] Frequency and duration of preventive maintenance (PM) is one
performance factor of an ion implantation tool. As a general
tendency the tool PM frequency and duration should be decreased.
The parts of the ion implanter tool that require the most
maintenance include the ion source, which is generally serviced
after approximately 50 to 300 hours of operation, depending on
operating conditions; the extraction electrodes and high voltage
insulators, which are usually cleaned after a few hundred hours of
operation; and the pumps and vacuum lines of vacuum systems
associated with the tool. Additionally, the filament of the ion
source is often replaced on a regular basis.
[0007] Ideally, feedstock molecules dosed into an arc chamber would
be ionized and fragmented without substantial interaction with the
arc chamber itself or any other components of the ion implanter. In
reality, feedstock gas ionization and fragmentation can results in
such undesirable effects as arc chamber components etching or
sputtering, deposition on arc chamber surfaces, redistribution of
arc chamber wall material, etc. In particular, the use of carbon
monoxide or carbon dioxide gases can result in carbon deposition
within the chamber. This can be a contributor to ion beam
instability, and may eventually cause premature failure of the ion
source. The residue also forms on the high voltage components of
the ion implanter tool, such as the source insulator or the
surfaces of the extraction electrodes, causing energetic high
voltage sparking. Such sparks are another contributor to beam
instability, and the energy released by these sparks can damage
sensitive electronic components, leading to increased equipment
failures and poor mean time between failures (MTBF).
[0008] In another instance of undesirable deposition, various
materials (such as tungsten) can accumulate on components during
extended ion implantation processes. Once enough tungsten is
accumulated, the power used to maintain temperature sufficient to
meet the beam current setpoint may not be sustainable. This causes
loss of ion beam current, which leads to conditions that warrant
the replacement of the ion source. The resultant performance
degradation and short lifespan of the ion source reduces
productivity of the ion implanter tool.
[0009] Yet another cause of ion source failure is the erosion (or
sputtering) of material. For example, metallic materials such as
tungsten (e.g., the cathode of an IHC source or the filament of a
Bernas source) are sputtered by ions in the plasma of the arc
chamber. Because sputtering is dominated by the heaviest ions in
the plasma, the sputtering effect may worsen as ion mass increases.
In fact, continued sputtering of material "thins" the cathode
eventually leading to formation of a hole in the cathode ("cathode
punch-through" in the case of IHC), or for the case of the Bernas
source, creates an opening in the filament. Performance and
lifetime of the ion source are greatly reduced as a result. The art
thus continues to seek methods that can maintain a balance between
the accumulation and erosion of material on the cathode to prolong
the ion source life.
SUMMARY
[0010] In one aspect, the present disclosure relates to a method of
implanting carbon ions into a target substrate. This method
comprises: ionizing a carbon-containing dopant material to produce
a plasma having ions; and implanting the ions into the target
substrate. The carbon-containing dopant material is of the formula
C.sub.wF.sub.xO.sub.yH.sub.z wherein if w=1, then x>0 and y and
z can take any value, and wherein if w>1 then x or y is >0,
and z can take any value.
[0011] In another aspect, the present disclosure relates to another
method of implanting carbon ions into a target substrate. This
method comprises: ionizing a carbon-containing dopant material to
produce a plasma having ions; co-flowing an additional gas or
series of gases with the carbon-containing dopant material; and
implanting the ions into the target substrate. The
carbon-containing dopant material is of the formula
C.sub.wF.sub.xO.sub.yH.sub.z, wherein w, x, y and z are as defined
above.
[0012] In another aspect, the present disclosure relates to a
method of improving the efficiency of an ion implanter tool. This
method comprises: selecting a carbon-containing dopant material of
the formula C.sub.wF.sub.xO.sub.yH.sub.z for use in the ion
implanter tool in a chamber, wherein w, x, y and z are as defined
above; ionizing the carbon-containing dopant material; and
implanting a carbon ion from the ionized carbon-containing dopant
material using the ion implanter tool. The selecting of the
material of the formula C.sub.wF.sub.xO.sub.yH.sub.z minimizes the
amount of carbon and/or non-carbon elements deposited in the
chamber after the implanting of the carbon ion. In doing so, the
performance of the ion source is optimized.
Other aspects, features and embodiments of the present disclosure
will be more fully apparent from the ensuing description and
appended claims.
DETAILED DESCRIPTION
[0013] In accordance with the present disclosure, carbon ions are
implanted from a feedstock source material into the target material
of a substrate via an ion implantation process. In one exemplary
embodiment, an ion source generates the carbon ions by introducing
electrons into a vacuum arc chamber filled with a carbon-containing
dopant gas as the feedstock material. The chamber has tungsten
walls on which a filament electrode and a repeller electrode are
mounted and separated from the walls by ceramic insulators.
Collisions of the electrons with molecules in the carbon-containing
dopant gas result in the creation of ionized plasma consisting of
positive carbon ions. The ions are then collimated into an ion
beam, which is accelerated towards the target material. The beam
may be directed through a mask having a plurality of openings
therein to implant the carbon ions in the desired configuration.
The present disclosure is not limited in this regard as other means
of implanting carbon ions are within the scope of the present
disclosure. Furthermore, the present disclosure is not limited to
the implantation of carbon ions, as any ion other than carbon (or
in addition to carbon) can be selected for implantation.
[0014] In any embodiment, to generate the carbon ions, the
carbon-containing dopant material has the formula
C.sub.wF.sub.xO.sub.yH.sub.z wherein if w=1, then x>0 and y and
z can take any value, and wherein if w>1 then x or y is >0,
and z can take any value. The carbon atom is separated from the
remainder of the molecule, thereby resulting in an ionized plasma
that includes positive carbon ions. The positive carbon ions may be
singular, or they may form clusters of two or more carbon atoms.
Alternatively, molecular ions of the form
C.sub.aF.sub.bO.sub.cH.sub.d.sup.+, wherein a>0, and b, c, and d
can have any value, may be formed in order to co-implant multiple
atomic species simultaneously. For example, implanting an ion such
as CF.sup.+ may eliminate a later F.sup.+ implant. For cases in
which co-implantation of species compromises the integrated circuit
quality or performance, the carbon dopant material can be used to
produce non-carbon ions for implantation. An example would be the
implantation of F.sup.+. The benefit is that a second dopant
material containing fluorine may not be required.
[0015] The ratios of C, F, O, and H (as denoted by w, x, y, and z)
are chosen to optimize ion source life and beam current. While the
use of carbon achieves specific integrated circuit device
characteristics, the carbon will deposit within the ion source
chamber of the ion implanter, causing electrical shorts or particle
generation. Additionally, the carbon can cause sputtering of the
cathode (IHC source) or filament (Bernas source), resulting in
shortened ion source life. The presence of oxygen within the dopant
material helps to minimize the deposition of carbon by oxidizing
carbon deposits to form CO or CO2. However, the oxygen can also
oxidize components of the ion source, such as the cathode or the
filament. The oxidation of these components may degrade the
performance of the ion implant tool, thereby leading to frequent
maintenance requirements. By adding fluorine to the dopant source,
the oxidation of the cathode or filament can be minimized. However,
fluorine can also react with the metallic walls of the arc chamber
(usually tungsten or molybdenum), forming gases of the formula WF,
or MoF.sub.x wherein x=1-6. When these gases contact the cathode or
filament, they tend to react and deposit tungsten. While this is
beneficial in that it can help balance any sputtering due to the
ions within the plasma, it may be desirable to add some hydrogen to
the molecule to balance the tungsten deposition rate (hydrogen will
restrict the ability of the fluorine from reacting with the
metallic walls to form the metal fluorides that subsequently cause
metal deposition on the cathode or filament).
[0016] In one embodiment, the C.sub.wF.sub.xO.sub.yH.sub.z source
gas comprises COF.sub.2. When COF.sub.2 is used as the source gas,
the molecule is ionized in the arc chamber, and C.sup.+ ions are
separated via mass analysis and then implanted into the target
material. Within the arc chamber, O and F ions and neutrals are
also present. The oxygen helps to minimize carbon deposits, while
the fluorine serves to keep the cathode or filament from forming an
oxide surface layer. In this manner, the performance of the ion
source is greatly improved.
[0017] The present disclosure also contemplates the simultaneous
flowing of C.sub.wF.sub.xO.sub.yH.sub.z material(s) with oxygen or
an oxygen-containing gas such as air to modify or control the
ratios of C, F, O, and H, thereby further modifying or controlling
the amount of carbon ions implanted and optimizing the trade-off
between carbon ions implanted and oxide formation. In particular,
the C.sub.wF.sub.xO.sub.yH.sub.z can be co-flowed with COF.sub.2,
CO.sub.2, CO, or any other oxygen-containing gas. Without being
bound by theory, it is contemplated that the co-flowing of
COF.sub.2 or similar gases balances the deposition of the carbon
ion with the coating of the arc chamber and etching.
[0018] The present disclosure additionally contemplates the
simultaneous flowing of C.sub.wF.sub.xO.sub.yH.sub.z material(s)
with gases such as fluorine and hydrogen or dilution with inert
gases such as nitrogen, argon, xenon, helium, combinations of the
foregoing, and the like. The use of inert gases helps to sustain a
plasma when flowing dopant gases.
[0019] By adjusting the ratios of elements in and generating carbon
ions from a carbon-containing dopant gas having the formula
C.sub.wF.sub.xO.sub.yH.sub.z (and optionally co-flowing the dopant
gas with COF.sub.2, CO.sub.2, CO, (or another carbon-containing
molecule) fluorine, hydrogen, nitrogen, argon, or the like), the
amount of carbon implanted is maximized and the amounts of
non-carbon elements are minimized with regard to the deposition
thereof within the chamber. In such manner, the efficiency of the
implanter tool can be improved. Additionally, the downtime of such
a tool (for maintenance, cleaning, and the like) can also be
reduced.
[0020] Furthermore, the C.sub.wF.sub.xO.sub.yH.sub.z material could
be flowed simultaneously with up to four additional gases. Such
gases include, but are not limited to, (1)
CO+F.sub.2+H.sub.2+O.sub.2; (2) CO+COF.sub.2+H.sub.2; and (3)
CF.sub.4+CH.sub.4+O.sub.2. The present disclosure is not limited in
this regard as other gases are within the scope of the present
invention.
[0021] Although this disclosure has included various detailed
embodiments, it will be understood by those of skill in the art
that various changes may be made and equivalents may be substituted
for elements thereof without departing from the scope of the
disclosure. In addition, modifications may be made to adapt a
particular situation or material to the teachings of the invention
without departing from the essential scope thereof. Therefore, it
is intended that the disclosure not be limited to the particular
embodiments disclosed in the above detailed description, but that
the disclosure will include all embodiments falling within the
spirit and scope of the foregoing description.
* * * * *