U.S. patent application number 10/632582 was filed with the patent office on 2004-02-05 for focused ion beam deposition.
Invention is credited to Gavish, Ilan, Greenzweig, Yuval.
Application Number | 20040020434 10/632582 |
Document ID | / |
Family ID | 25029189 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040020434 |
Kind Code |
A1 |
Gavish, Ilan ; et
al. |
February 5, 2004 |
Focused ion beam deposition
Abstract
Introducing at least one metal such as cobalt, molybdenum, metal
carbonyl, tungsten, platinum, or other suitable metal to a focused
ion beam. Introducing the focused ion beam to a substrate within a
processing chamber. Forming at least one layer over a substrate.
Applying heat to the layer by, for example, a laser.
Inventors: |
Gavish, Ilan; (Kamiel,
IL) ; Greenzweig, Yuval; (Ramat Hasharon,
IL) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN
12400 WILSHIRE BOULEVARD, SEVENTH FLOOR
LOS ANGELES
CA
90025
US
|
Family ID: |
25029189 |
Appl. No.: |
10/632582 |
Filed: |
July 31, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10632582 |
Jul 31, 2003 |
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10209983 |
Jul 31, 2002 |
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6627538 |
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10209983 |
Jul 31, 2002 |
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09753108 |
Dec 30, 2000 |
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6492261 |
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Current U.S.
Class: |
118/723FI ;
257/E21.168; 257/E21.17; 257/E21.591 |
Current CPC
Class: |
C23C 16/486 20130101;
C23C 16/52 20130101; C23C 16/047 20130101; C23C 16/56 20130101;
H01L 21/28556 20130101; H01L 21/76892 20130101; H01L 21/28568
20130101; H01L 21/76886 20130101; C23C 16/16 20130101 |
Class at
Publication: |
118/723.0FI |
International
Class: |
C23C 016/00 |
Claims
What is claimed is:
1. A system comprising: a chamber configured to house a substrate
for processing; an energy source coupled to the chamber; a system
controller configured to control the introduction of at least one
metal precursor gas to a focused ion beam and to control the
introduction of the focused ion beam from the energy source; and a
memory coupled to the controller comprising a computer-readable
medium having a computer-readable program embodied therein for
directing operation of the system, the computer-readable program
comprising: instructions for controlling the energy source and for
introducing the metal precursor gas into a focused ion beam which
is introduced into the chamber over the substrate in which the
metal from the focused ion beam forms at least one metal layer over
the substrate; and controlling a coherent electromagnetic radiation
source to heat the at least one layer.
2. The system of claim 1, wherein the metal precursor gas is one of
cobalt, metal carbonyl, molybdenum, platinum, and tungsten.
3. The system of claim 2, wherein introducing one of cobalt, metal
carbonyl, molybdenum, platinum, and tungsten into the focused ion
beam in a controlled ratio at a chamber pressure in the range of
10.sup.-5 to 10.sup.-7 torr.
4. The system of claim 1, wherein the focused ion beam heats a
discrete area on the layer.
5. The system of claim 1, further comprising a lens coupled to the
coherent electromagnetic radiation source to focus the coherent
electromagnetic radiation source to a spot size on the at least one
layer.
6. The system of claim 5, wherein said lens comprises a 5.times.
lens of numerical aperture approximately 0.15 to focus a spot size
of the coherent electromagnetic radiation source in the range of 8
microns to 10 microns in diameter.
7. The system of claim 5, wherein the at least one metal layer
formed over the substrate comprises tungsten and the spot size is
approximately 10 micro-meters in width.
8. The system of claim 1, wherein the at least one metal layer over
the substrate comprises at least one metal layer line having a
thickness in the range of 0.1 microns to 1 micron.
9. The system of claim 1, wherein the chamber further comprises one
of a low level vacuum, a non-reacting gas, and a reducing
atmosphere.
10. The system of claim 9, wherein one of a carbon, gallium, and an
oxygen is removed from the layer.
11. The system of claim 1, wherein the instructions for controlling
the introduction of at least two metals comprises instructions
involving introducing the cobalt, metal carbonyl, molybdenum,
platinum, and tungsten in a controllable ratio.
12. The system of claim 1, further comprising a plurality of inlets
to introduce a plurality of metal precursor gasses, wherein each of
the plurality of metal precursor gasses is introduced via a
separate inlet and in a controllable ratio.
Description
RELATED APPLICATION
[0001] The application is a divisional of U.S. patent application
Ser. No. 10/209,983, filed Jul. 31, 2002, by Applicants, Ilan
Gavish and Yuval Greenzweig, entitled "Focused Ion Beam
Deposition," which is a continuation of U.S. patent application,
Ser. No. 09/753,108, filed Dec. 30, 2000, now U.S. Pat. No.
6,492,261.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to post-processing with heat
of focused ion beam deposited "metal lines" or layers, and the
resultant reduction of the metal line or layer's electrical
resistance.
[0004] 2. Background
[0005] Integrated circuit structures are generally formed of
numerous discrete devices on a semiconductor chip such as a silicon
semiconductor chip. The individual devices are interconnected in
appropriate patterns to one another and to external devices through
the use of interconnection lines or interconnects to form an
integrated device. Typically, many integrated circuit devices are
formed on a single structure, such as a wafer substrate and, once
formed, are separated into individual chips or dies for use in
various environments.
[0006] There are several conventional processes for introducing
metals such as aluminum, an aluminum alloy, or platinum to form an
interconnect onto a substrate. The metal is generally introduced in
the form of a deposition process, (e.g., chemical vapor deposition
(CVD)) and patterned by way of an etching process into a discrete
line or lines. Another process for introducing a metal
interconnect, particularly copper or its alloys over a substrate is
the damascene process. The damascene process introduces copper
interconnect according to a desired pattern previously formed in
dielectric material over a substrate.
[0007] Yet another process is FIB metal deposition that is
generally used to introduce thin metal lines or arbitrary patterns
as a layer over a substrate. FIB deposition is used for
modification of small metallic structures such as the modification
of existing interconnects in integrated circuits. In the FIB, a
gaseous metal-organic precursor containing metal (e.g. platinum,
tungsten etc.) is introduced over a substrate. The ion beam
contacts the gaseous metal-organic precursor causing the
dissociation of the precursor and the release of metal atoms. The
metal atoms then form a metal line or layer over the substrate.
[0008] One disadvantage of FIB metal line deposition is that the
material that is formed is impure, and typically has a high (in
comparison to process lines) electrical resistance such as 160
micro Ohm centimeters (micro Ohm cm) to 200 micro Ohm cm. What is
needed is a process and a tool that allows for the introduction of
metals to form a layer over a substrate that is both efficient and
decreases the electrical resistance of the FIB interconnect.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The features, aspects, and advantages of the invention will
become more thoroughly apparent from the following detailed
description, appended claims, and accompanying drawings in
which:
[0010] FIG. 1 illustrates a schematic cross-sectional view of a
processing chamber suitable for performing the modification
described in reference to FIGS. 2-5 in accordance with one
embodiment of the invention;
[0011] FIG. 2 illustrates a schematic cross-sectional view of a
portion of a substrate in accordance with one embodiment of the
invention;
[0012] FIG. 3 illustrates a schematic cross-sectional view of a
metal introduced onto the substrate of FIG. 2 in accordance with
one embodiment of the invention;
[0013] FIG. 4 illustrates a schematic cross-sectional view of a
structure having multiple layers in which discrete areas are heated
in accordance with one embodiment of the invention; and
[0014] FIG. 5 illustrates a flow diagram of one method of focused
ion beam deposition of a layer over a substrate and heating of the
layer in accordance with one embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] In one embodiment, a method includes introducing at least
one metal precursor to a focused ion beam (FIB), forming at least
one metal (or alloy) layer over a substrate, and applying heat to
the layer in order to reduce the resistance of that layer. The
metal may include cobalt, molybdenum, tungsten, platinum, or a
mixture of cobalt, molybdenum, tungsten or any other suitable
metal. In the context of the description of the invention, the
words cobalt, molybdenum, platinum, or tungsten are intended to
refer to both pure cobalt, molybdenum, platinum, or tungsten and to
their alloys that are suitable as integrated circuit interconnect
material.
[0016] In another aspect, a system is disclosed for FIB
introduction of a metal or metals over a substrate to form a layer
on the substrate and thereafter, heat is applied to that layer.
Heating the layer reduces the resistance of that layer. In one
embodiment, the system includes a chamber configured to house a
substrate, such as a semiconductor wafer, a discrete chip or a die,
and an energy source. A system controller is configured to control
the introduction of a metal precursor such as a metal carbonyl,
where the metal may be cobalt, molybdenum, platinum, tungsten, or a
mixture of two or more of these metals into a FIB. The system
controller also controls the deposition of the metals by
controlling the ion beam scanning over a substrate. A memory
coupled to the controller includes a machine-readable medium having
a machine-readable program embodied therein for directing the
operation of the system. The machine-readable program includes
instructions for controlling the flow of metal precursor introduced
to the substrate, and controlling the scanning of the ion beam to
form the pattern of the metal layer. Additionally, the
machine-readable program includes instructions for controlling the
amount of power and its special distribution applied by a laser or
other power source to heat a layer of metal(s) formed over the
substrate. In the discussion that follows, FIG. 1 illustrates FIB
deposition system 103 for FIB deposition and FIGS. 2-5 illustrate
the formation of layers over a substrate and the formation of
heated areas on the layers.
[0017] FIG. 1 illustrates a schematic cross-sectional view of a FIB
deposition system 103 that is used to introduce a metal or metals
over substrate 100 to form a layer over substrate 100 and heat the
layer or a discrete area of the layer to reduce the resistance in
the layer. FIB deposition system 103 includes chamber 150, first
and second reservoirs (183, 185), FIB column 175, heat source 191,
and controller 190 for FIB deposition of metals such as cobalt,
molybdenum, platinum, tungsten or other suitable metals over
substrate 100. Each of these devices is described below.
[0018] Chamber 150 is typically constructed of aluminum or steel
and has a suitable inside volume to house a substrate, such as
substrate 100. Substrate 100 may be a piece of silicon coated by a
layer 1 micron thick of silicon dioxide or any electrically
insulating substrate. In FIG. 1, substrate 100 is seated on
substrate processing stage 160 that itself is coupled to shaft 165
to support stage 160 inside chamber 150.
[0019] Coupled to chamber 150 is first reservoir 183 and second
reservoir 185. First reservoir 183 and second reservoir 185 are
configured to contain different metal precursors for their delivery
to chamber 150 in, for example, a metal carbonyl. Many metals have
gaseous precursors that have molecules composed of a metal atom (or
atoms) chemically bonded to a lighter radical--frequently
organic--which enables the composite material to be in the gaseous
phase in vacuum levels typical of FIBs such as (10.sup.-6
torr).
[0020] First inlet 187 connected to first reservoir 183 and second
inlet 189 connected to second reservoir 185 are configured to
release the metal precursor at the working area of the ion beam
over substrate 100. In one embodiment, first inlet (e.g., nozzle)
187 and second inlet 189 should be positioned (h.sub.1)
approximately 100 microns from the surface of substrate 100 and
approximately 100 microns from the center of FIB column 175, or the
center of the working area of the ion beam. FIG. 1 also shows that
first reservoir 183 and second reservoir 185 are connected to
controller 190. Controller 190 controls the addition of the metal
precursors from first reservoir 183 and second reservoir 185 to
chamber 150 and may automatically adjust first inlet 187 and second
inlet 189. Absent automated process control, first inlet 187 and
second inlet 189 may be positioned manually.
[0021] There are several methods for introducing one or more metal
precursors to chamber 150. For example, at least one or more metal
precursors is placed into the first or second reservoirs (183 and
185). At atmospheric pressure, the metal precursor(s) are solid.
Once chamber 150 is pumped down to pressures as specified herein,
one or more metal precursors begin to sublimate and to create a
vapor. Upon opening of the appropriate valves such as V.sub.1 or
V.sub.2 from first and second reservoirs (183, 185), the gaseous
phase of metal precursor(s) flows through, for example, a single
inlet such as first inlet 187 to chamber 150. A metal line or layer
is then formed over substrate 100 after the ion beam contacts the
metal precursor.
[0022] Another method is to introduce two metal precursors (e.g.,
tungsten hexacarbonyl, methylcyclopentadienyl trimethyl platinum,
etc.) into first and second reservoirs (183 and 185) that enter
chamber 150 through separate inlets such as first and second inlets
(187 and 189). Another method involves using a single bi-metal
precursor from a single reservoir, into chamber 150, and onto
substrate 100.
[0023] Yet another method is to introduce two metal precursors such
as W(CO).sub.6 and Co.sub.2(CO).sub.8 into first and second
reservoirs (183, 185) for injection of the metal precursors through
a single inlet, such as first inlet 187, into chamber 150. The
mixture of these two metal precursors is placed in the path of the
ion beam and after the FIB contacts the metal precursors, a metal
or a metal alloy layer is formed over substrate 100.
[0024] Once the metal precursor(s) flow starts reaching the working
area 102 of the FIB system 103 on substrate 100 in the chamber 150,
the ion beam may be activated in a raster (scanning) pattern that
defines the shape of the box or pattern to be deposited on the
sample. The ion beam is introduced through FIB column 175. FIB
column 175 is coupled to chamber 150 and enters through a top
surface of the otherwise sealed chamber. FIB column 175 includes an
ion source 180 for introducing an ion species, including but not
limited to a gallium source, and an acceleration voltage powered by
a HV power supply 182 (e.g., 50 kilo-Volt (kV), 30 kV) for ionizing
the source species and delivering the source species to the
substrate. The current introduced is also regulated by FIB
aperture(s) 181 inside the FIB column 175.
[0025] In one embodiment, FIB column 175 is a Micron 9800FC column
produced by FEI Corporation of Hillsboro, Oreg. (www.feico.com). In
another embodiment, FIB column 175 is an FEI FIB 200, produced by
FEI. It is to be appreciated that other FIB columns may be
similarly suitable.
[0026] Once the precursor molecules are adsorbed to the surface of
substrate 100 and the FIB contacts the substrate, a layer such as
an interconnect is formed over substrate 100. For example, FIB
tungsten lines of width 8 microns, length 100 microns and height
(thickness) 0.25 microns may be formed using techniques described
herein. The width of 8 microns conforms to the typical minimum spot
size of the laser and the optics used to heat the lines. It will be
appreciated that the width of FIB tungsten lines may be much
smaller than or greater than 8 microns. These lines are lines with
a specific resistance of about 200 micro Ohm cm.
[0027] After the metal lines or layers have been formed over
substrate 100, substrate 100 is either kept in chamber 150 or is
placed within an evacuated chamber (e.g., a chamber of a lower
grade vacuum e.g. .about.1 torr). The heating of the FIB-deposited
metal lines or layer may be performed in a low level vacuum of 1
torr, an atmosphere of non-reacting gas, a reducing atmosphere such
as hydrogen or any other suitable atmosphere.
[0028] Heat is then applied to the layer over substrate 100 through
heat source 191 in order to reduce the resistance of the layer.
Heat source 191 may be external or internal to FIB deposition
system 103. Heat source 191 may be, for example, a Light
Amplification through Stimulated Emission of Radiation (laser), a
continuous wave (CW)(not pulsed), a pulsed laser, an Argon Ion
laser having most of its power in the wavelengths 514 and 488 nm,
or any other suitable laser. A 5.times. lens of numerical aperture
approximately 0.15 may be used with a resulting spot size of
roughly 8-10 microns. Other objective lenses and resultant spot
sizes may also be suitable.
[0029] Other options for heating include ovens, local heating by
hot inert gas jets, a current forced through the metal line by an
external power source, or other suitable heat sources. Other
suitable heat sources include those heat source that cause a
re-crystallization of the metal component of the FIB metal.
[0030] The amount of heat that must be applied to a layer is
dependent, in part, upon the metal or metals of which the layer is
composed. Generally, if a laser is used, a power density
characterized by 0.3 to 5 watts applied to a spot of diameter 10
.mu.m, with the higher power generally reserved for the more
refractory elements, such as tungsten. If the metal line or layer
comprises tungsten, the power of the laser should be about 4.5W. In
order to achieve an appropriate heat to be applied, the metal
line(s) or layer(s) over substrate 100, one skilled in the art may
adjust the laser power to obtain probable damage to substrate 100
before actually heating the metal line or layer. The power may then
be adjusted to below the estimated heating value that may
potentially cause damage to the metal line or layer. The stage
speed may then be adjusted to about 50 .mu./second range. It will
be appreciated that the stage speed is in the range of about 0 to
about 250 .mu./second preferably; however, stage speeds greater
than 250 .mu./second may also be used. The lower the stage speed,
the lower the power density that is typically required.
[0031] Heating of the metal line or layer by laser may be
accomplished by fixing the laser beam and moving substrate 100 (by
moving substrate processing stage 160), fixing both the laser beam
and substrate 100, fixing the substrate 100 and scanning substrate
100 with the laser beam, or any other suitable method.
[0032] An example of effective parameters for a laser to heat a
line thickness of about 0.25 .mu. is a spot size width of 8
microns, a stage speed of 50 .mu./second and a power value of 0.125
watt/micron.sup.2. Such laser treatment has caused crystallization
of tungsten and its transformation into poly-crystalline tungsten
as determined by transmission electron microscopy diffraction
analysis. It has also caused the removal of carbon, oxygen, and
residual source elements (e.g. gallium) as determined by Energy
Dispersive Spectrometry and Auger analyses. The laser heating of
the FIB-introduced metal layer may be performed in a low level
vacuum of 1 torr, an atmosphere of non-reacting gas, or a reducing
atmosphere such as hydrogen. After a particular area on the layer
has been heated, the specific resistance of the layer may be as low
as 10 micro Ohm cm to about 120 micro Ohm cm.
[0033] Coupled to chamber 150 is controller 190. Controller 190
includes a processor (not shown) and memory 192. Memory 192
includes instruction logic accessible by the processor to control
the introduction of metal precursor(s) and the operation of the
FIB. Memory 192 also includes instruction logic for applying heat
to a layer formed over substrate 100.
[0034] Controller 190 may control a variety of other parameters.
For example, controller 190 may control the movement of heat source
191 to heat areas on layers over substrate 100. Alternatively,
substrate 100 of FIG. 1 itself may be moved to heat another
discrete area on a layer. It is to be appreciated, however, that
with a suitable heat source 191, an entire interconnect area may be
heated at once.
[0035] Controller 190 also controls vacuum pump 173 to ensure gases
generated in chamber 150 from heating a layer over substrate 100
are removed. In this embodiment, likely expelled gases such as
carbon oxides are removed through pump 173, and exhaust 174. Other
suitable instructions in controller 190 are used to control other
applicable control parameters.
[0036] Given the explanation of FIB deposition system 103, the
description that follows in FIGS. 2 through 5 illustrates the
formation of a structure of interconnects as part of a device in
accordance with one embodiment of the invention. FIG. 2 illustrates
a schematic cross-sectional view of a portion of typical
semiconductor substrate or wafer 200 in accordance with one
embodiment of the invention. Substrate 200 generally comprises
silicon or other suitable material. Typically, substrate 200
includes a dielectric layer 205. Dielectric layer 205 may include
materials such as silicon dioxide, silicon nitride, or other
suitable material. Devices (e.g., transistors) and other material
layers may also be formed on substrate 200 below dielectric layer
205.
[0037] FIG. 3 illustrates a schematic cross-sectional view of
metals introduced onto substrate 200 illustrated in FIG. 2 using
FIB deposition to form structure 212. At least one or more
precursors of metals such as cobalt, molybdenum, platinum, tungsten
or other suitable metal is introduced by a metal precursor in a
gaseous phase to the chamber. The ion beam scans a layer thereby
formning a FIB layer such as first layer 210. First layer 210 may
include one or more metals. In this embodiment, first layer 210 is
an alloy that includes, for example, two metals such as cobalt and
molybdenum that are introduced onto substrate 200 through FIB
deposition. It will be appreciated that first layer 210 may also
comprise any other selection of metals.
[0038] Additional layers may optionally be formed over first layer
210 as shown by second, third, and fourth layers (220, 230, 240) of
structure 262 of FIG. 4 using techniques disclosed herein.
Additional layers may include one or more metals such as cobalt,
metal carbonyl, molybdenum, platinum, tungsten, or other suitable
metals. For example, second layer 220 may include metals such as
tungsten carbonyl and tungsten; third layer 230 may include metals
such as cobalt and molybdenum; and fourth layer 240 may include
metals such as tungsten and tungsten carbonyl. Moreover, the
thickness of these layers may range from about 0.1 .mu.m to about
0.3 .mu.m. It will be appreciated that the thickness and
composition of additional layers may be arbitrarily established by
adjusting the parameters to FIB deposition system 103.
[0039] FIG. 4 further illustrates layers of structure 262 in which
resistance of a layer is reduced by localized heating in accordance
with one embodiment of the invention. Specifically, localized
heating by using a laser produces first heated area 255. It will be
appreciated that localized heating of discrete areas on fourth
layer 240 over substrate 200 may be accomplished in a variety of
ways. For example, the laser may heat a localized area on structure
262 at 0.3 watts to 5 watts in an area of 0.5 .mu.m.sup.2 to 800
.mu.m.sup.2. Other heat sources capable of heating a layer include
local heating by inert hot gas jets, local ion scan bombardment,
current forced through the layer by an external power source, or
other suitable heat sources.
[0040] First heated area 255 is formed through top heating of
fourth layer 240. Crystalline metal is formed at first heated area
255. A suitable amount of time to form first heated area 255 of
structure 262 in FIG. 4 is in the range of about 500 to about
20,000 microseconds to heat a 0.1 to about 1 micron thick
interconnect material in which the heat that is applied is about
0.3 to 5 watts. Heating of, for example, fourth layer 240 causes
carbon and oxygen that may be present in this layer to be driven
off, presumably as carbon monoxide and carbon dioxide. The
resistance that is achieved in first heated area 255 is about in
the range of 120 micro Ohm cm to about 10 micro Ohm cm.
Consequently, structure 262 illustrated in FIG. 4 has a much lower
resistance than the resistance found in conventional devices. It is
appreciated that to lower the resistance of the metal line, the
entire line need not be exposed to the heat treatment. Instead, the
resistance of the line may be reduced by localized heating of a
desired number of areas. Additionally, localized heating of
discrete areas on other layers such as first, second, third, or
fourth layers (210, 220, 230, 240) over substrate 200 may be
accomplished by using a suitable heat source 191. For example, side
heating of second layer 220 and third layer 230 may create a second
heated area (not shown).
[0041] FIG. 5 illustrates a flow diagram of one method of FIB
deposition of a layer over a substrate and heating of the layer in
accordance with one embodiment of the invention. At block 300, at
least one metal is introduced to a FIB. At block 310, the FIB is
introduced to a substrate within a processing chamber. At block
320, at least one layer is formed over a substrate by the FIB. At
block 330, heat is applied to the layer. Crystalline metal may be
formed in the area that is heated. Crystalline metal is the more
stable form of metal in its natural state.
[0042] In the preceding detailed description, the invention is
described with reference to specific embodiments thereof. It will,
however, be evident that various modifications and changes may be
made thereto without departing from the broader spirit and scope of
the invention as set forth in the claims. The specification and
drawings are, accordingly, to be regarded in an illustrative rather
than a restrictive sense.
* * * * *