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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device and a method for processing of
semiconductor wafers and fabrication of microelectronic devices.
2. Description of the Relevant Art
Advanced semiconductor VLSI technologies employ plasma processing for a
number of important steps in the device fabrication sequence. The use of
plasma processing results in a lower processing temperature and a higher
deposition rate for growth and deposition of thin layers of insulators,
semiconductors, or metals. Moreover, reactive ion etching processes in
low-pressure plasmas are essential for anisotropic patterning of the
submicron features in VLSI device structures.
Conventional plasma processing techniques, however, suffer from a number of
limitations. Low-pressure reactive ion etching systems with RF (usually
13.56 MHz) discharge offer relatively low gas ionization efficiencies and
can cause damage to the devices due to the large substrate floating
potentials and excessive ion energies and plasma deposition processes
using conventional discharge methods can also suffer from similar
problems. A major disadvantage of the conventional RF discharge techniques
is that the average ion energy cannot be controlled or adjusted
independently and any adjustment of the ion energy results in a change in
the plasma density and, as a result, the process kinetics.
Generation of plasmas by electrodeless microwave (2.45 GHZ) discharge is a
viable alternative to the conventional RF discharge methods. The use of
microwave power instead of lower frequency RF power enhances the gas
ionization efficiency and reduces the ion bombardment-induced damage to
the wafer due to the lower iow acceleration potentials. The coupling of
microwave power to the discharge medium can be made very efficient if a
suitable static magnetic field is established in the discharge medium.
Under the so-called electron cyclotron resonance (ECR) condition, the
electrons in the plasma experience a cyclotron (spiral) motion around the
static magnetic flux lines while gaining energy from the alternating
microwave eletric field. In a uniform magnetic field, the cross section of
the path traversed by the electrons is a circle. The frequency of the
cyclotron rotation (f.sub.c) is directly proportional to the magnetic flux
density (B) and inversely proportional to the electron mass (m.sub.e), as
shown below:
##EQU1##
where q is the electronic charge. Based on this equation, the frequency of
cyclotron rotation is calculated to be
##EQU2##
in cycles per second where B is the static magnetic flux density in Gauss.
Under ECR condition the electron cyclotron rotation frequency becomes
equal to the microwave frequency. For a microwave frequency of 2.45 GHz,
the ECR condition requires a magnetic flux density of 875 G. It should be
noted that the cyclotron frequency only depends on B and is independent of
the electron velocity. The curvature radius of the electron spiral path is
inversely proportional to the component of the magnetic flux density
perpendicular to the electron velocity vector.
The average power transferred to each electron in a microwave field is
maximized when the ECR condition is satisfied because the cyclotron motion
and the microwave electric field oscillations stay in phase with each
other. From an electrical point of view, the plasma impedance is highly
reactive (inefficient power absorption) at high frequencies. In an ECR
microwave plasma, an electron continuously absorbs energy from the
microwave field until it experiences a collision with a neutral gas
species. Higher gas pressures result in larger electron collision
probabilities and less energetic electrons in an ECR plasma because of a
more frequent disturbance of the electron free spiral motion. As a result,
ECR plasma processing effects will be more pronounced when the
electron-neutral collision frequency is made much less than the ECR or
microwave frequency. This implies that ECR is particularly useful for
lower pressure processing (few mTorr and below; 10.sup.-3 -10.sup.-5 Torr
range) where conventional RF discharge is rather inefficient.
ECR plasma generation techniques are capable of producing efficient plasmas
at low pressures with much higher densities (as much as several orders of
magnitude) compared to the conventional RF discharge or non-ECR microwave
plasma techniques. The ECR enhancement also extends the operating process
pressure domain down to very low pressures in the high-vacuum regime. ECR
plasma processing is applicable to a wide range of advanced semiconductor
device fabrication processes (dry clean-up, deposition, etching) as well
as sequential in-situ mutiprocessing.
Most of the existing ECR plasma system designs employ electromagnets in
order to generate a static magnetic field inside the plasma formation
chamber. FIG. 1 shows the general schematic of an ECR plasma processing
system which employs two electromagnets around a microwave discharge
cavity in order to establish a spatially varying magnetic flux density and
generate and ECR plasma stream. The electromagnets create a graded
magnetic field inside the microwave discharge cavity and the ECR field
condition (875 G) is satisfied at some point inside the cavity. The plasma
stream is extracted along a divergent magnetic field from the plasma
chamber to the reaction chamber. The magnetic flux density decreases
gradually from the plasma chamber towards the substrate holder.
This type of ECR plasma system design has a number of limitations which can
be summarized as follows:
The process uniformity on the wafer is very sensitive to the plasma
uniformity in the plasma chamber and the plasma cavity electromagnetic
mode of operation (standing wave patterns). The plasma nonuniformity
patterns can be easily projected onto the wafer because of the presence of
longitudinal magnetic field lines.
The system design is not easily scalable for larger wafer diameters. Larger
wafers dictate the use of larger plasma cavities and larger electromagnets
which can result in a less uniform plasma and a more complicatd reactor
design.
The diverging magnetic flux lines extend all the way to the wafer surface
and result in a less uniform process even if perfect plasma uniformity is
achieved in the plasma cavity. The process nonuniformity problems caused
by the field divergence effects are particularly more critical in dry
etching applications.
The large electromagnets require water cooling and a large amount of
electrical power to sustain the magnetic field.
Precise ion energy control is difficult because the wafer experiences
perpendicular magnetic field lines and the ions gain translational
acceleration by moving along the high-to-low magnetic flux lines extending
from the plasma chamber to the wafer. The field lines can also affect the
plasma electrical potential.
In some existing ECR reactor designs the process uniformity is somewhat
improved by using a third electromagnet under the wafer holder in order to
produce a more uniform perpendicular magnetic field and reduce its
divergence on the wafer. Moreover, the substrate holder may be coupled to
an RF source (13.56 MHz) in order to control the wafer potential with
respect to the plasma to enhance the incoming ion energies and to reduce
the divergent magnetic field effects. Nonetheless, these designs do not
remove the other limitations of this type of reactor design.
Besides the ECR reactor designs similar to the schematic shown in FIG. 1, a
multipolar distributed ECR reactor has also been discussed in the
literature. FIG. 2 shows the schematic of a multipolar ECR equipment
design where the energetic electrons are confined to the magnetic cusps at
the outer edge of the process chamber. In this system, plasma is produced
near the chamber wall and diffuses towards the chamber center. The
magnetic field lines at the center of the chamber are rather weak and
parallel to the wafer surface. The multipolar field created by the
permanent magnets creates the ECR condition and reduces plasma losses to
the chamber walls by magnetic confinement of the plasma. The multipolar
ECR design may have some advantages over the conventional ECR systems (and
also some disadvantages). Some of its limitations are as follows:
The plasma formation chamber is the same as the process chamber. This
restricts the system applications to the processes with one composite
plasma medium. Any gas injected into the vacuum chamber will be subjected
to microwave discharge and the system design does not allow selective
plasma formation simultaneous with injection of non-plasma gases onto the
wafer. Therefore, the system application will be mostly for etching
processes.
The entire process chamber and the wafer are immersed in a microwave field.
As a result, the plasma and process uniformity on the wafer may be
affected by the microwave standing wave and power absorption patterns.
The total volume of the ECR plasma formation regions is a small fraction of
the total process chamber volume. This may limit the plasma density on the
wafer.
Accordingly it would be useful to be able to provide a distributed ECR
device that has process uniformity, is scalable, has low power
consumption, causes less substrate damage, has an independent non-plasma
gas injection capability provides a remotely generated ECR plasma allows
independent control over plasma density, and allows sequential in-situ
multiprocessing.
SUMMARY OF THE INVENTION
The present invention overcomes the problems of existing ECR plasma
techniques and provides improvements over existing broad beam,
divergent-field ECR and multi polar ECR systems.
According to one embodiment of the present invention there is provided a
distributed electron cyclotron resonance remote plasma processing
apparatus, comprising: a processing chamber; a main transfer chamber in
fluid communicatin with the processing chamber; a plurality of peripheral
magnet bars surrounding the main tranfer chamber; a plurality of electron
cyclotron resonance plasma formation regions peripherally distributed
around the periphery of, remote from, and in fluid communication with the
main transfer chamber; and a plurality of magnet bars substantially
surrounding external surfaces of said plasma formation regions.
In another embodiment, there is a distributed electron cyclotron resonance
remote plasma processing apparatus, comprising: a processing chamber; a
main transfer chamber in fluid communication with the processing chamber;
a plurality peripheal magnet bars surrounding the main transfer chamber; a
toroidal plasma formation region of trapezoidal cross section around the
periphery of, remote from, and in fluid communication with the main
transfer chamber; a plurality of magnet bars substantially surrounding
external surfaces of the plasma formation region; and a plurality of
plasma generators peripherally distributed in the plasma formation region.
In yet another embodiment there is indicated a method for distributed
electron cyclotron resonance remote plasma processing of a workpiece,
comprising: generating electron cyclotron resonance activated species in
plasma formation regions distributed peripherally, remote from and in
fluid communication with a main transfer chamber; containing the activated
species using a magnetic field in the plasma formation regions;
introducing the activated species to the main transfer chamber; creating a
magnetic mirror in the main transfer chamber using a magnetic field; and
introducing the activated species to hte process chamber and to a face of
the workpiece.
The present invention provides at least the following advantages, in
addition to others mentioned in this application:
The module design comprises multiple distributed ECR plasma formation
chambers connected to a main cylindrical transfer chamber.
The system design allows independent control over each of the multiple a
plurality of ECR plasma formation chambers.
The process chamber and wafer are free of static magnetic field and
microwave power. Microwave power is only fed to the ECR plasma formation
chambers and does not leak into the main transfer chamber.
The main transfer chamber provides a full-scale view of the wafer front
face through a sapphire window at one end. This important design feature
provides capability for photon-assisted processing using incoherent deep
UV lamps or excimer laser sources. The other port of the transfer chamber
couples the wafer to the heating or cooling source, RF chuck, etc.
In contrast to the conventional ECR systems, the distributed, ECR remote
plasma system design is easily scalable for larger wafer diameters without
any degradation of process uniformity. There is no limitation in terms of
the size of the wafer.
Both ECR plasma generation and confinement are achieved by ceramic
permanent magnetic circuitry instead of electromagnets. Therefore, there
is no need for electrical power and water cooling in the magnetic
circuitry.
The system is capable of simultaneous generation of multiple ECR plasma
streams of more than one gas (spatially resolved plasma streams) in the
peripheral ECR plasma formation chambers, avoiding the possible
complications of composite gas discharge media. The plasma streams of
different gases are intermixed in the main transfer chamber only after
their formation.
The ECR remote plasma streams are freely superimposed and mixed in the
transfer chamber before arriving on the wafer surface and without any
magnetic field effects. The center of the cylindrical transfer chamber is
free of magnetic field lines and allows free diffusion and intermixing of
the ionic species. Therefore, excellent process uniformity should be
easily obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be described with reference to the accompanying
drawings, wherein:
FIG. 1 shows a prior art ECR plasma system.
FIGS. 2(a) and (b) show a prior art multipolar ECR microwave plasma system.
FIG. 3 shows a useful embodiment distributed multipolar ECR processing
module.
FIG. 4 shows another useful embodiment of the distributed multipolar ECR
processing module.
FIG. 5 shows a horizontal cross section of one embodiment of the main
transfer chamber of FIGS. 3 and 4.
FIG. 6 shows a horizontal cross section of another embodiment of the main
transfer chamber of FIGS. 3 and 4.
FIG. 7 shows a horizontal cross section of the plasma formation region
chamber of a useful embodiment of the processing module of FIG. 3.
FIGS. 8(a) and (b) show a vertical cross section of a useful embodiment of
one of the plasma formation regions of the distributed multipolar ECR
processing module.
FIG. 9 shows a horizontal cross section of the plasma formation region
chamber of another useful embodiment of the processing module of FIG. 3.
FIGS. 10(a) and (b) show a vertical cross section of a useful embodiment of
one of the plasma formation regions of the distributed multipolar ECR
processing module of FIG. 9.
FIGS. 11 shows a cross section of another useful embodiment of one of the
plasma formation regions of the distributed multipolar ECR processing
module.
FIGS. 12(a) an (b) show a horizontal cross section of a useful embodiment
of one of the plasma formation regions of the distributed multipolar ECR
processing module embodied in FIG. 11.
FIG. 13 shows a vertical cross section of a useful embodiment of one of the
plasma formation regions of the distributed multipolar ECR processing
module also embodied in FIG. 11.
FIGS. 14(a) and (b) show a horizontal cross section of a useful embodiment
of the plasma formation regions of the distributed multipolar ECR
processing module also embodied in FIG. 11.
In the various figures the same reference numerals are used to denote
similar parts. Additionally, in the drawings, the sizes and dimensions of
the various parts have been exaggerated or distorted for clarity of
illustration and ease of description.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
FIG. 3 shows a useful embodiment of a distributed multipolar ECR processing
module 10. Processing module 10 has a processing chamber 12 wherein a
wafer 14 can be processed in a various ways, e.g. etching, deposition, or
ashing etc. Processing module 10 can be formed from many materials (e.g.
aluminum, stainless steel, etc.). In order to minimize contamination of
the wafer 14, the inner walls 36 of processing module 10 are properly
passivated and the permanent magnets are placed in such a way as to keep
the reactants away from the inner walls 36. Processing chamber 12 is
typically maintained at a vacuum.
Wafer 14 is supoported with a face to be processed 16 facing downward by
wafer support 17. The wafer 14, however, can have its face to be processed
16 facing up, down or have a normal to its face parallel to the ground.
Having wafer 14 face to be processed 16 facing downward or having its
normal parallel to the ground reduces the potential for particulate
contamination. A vacuum is drawn through a vacuum pumping ports 18. The
placement of the vacuum pumping ports 18 adds to the process uniformity
across the face to be processed 16. Nonplasma process gas injectors 19 are
arranged around the periphery of wafer 14 to provide uniform distribution
of non-plasma process gasses.
The processing temperature of wafer 14 can be established in various ways
with minimal hardware modifications. In FIG. 3, wafer 14 is shown as being
heated by a radiant heater 20 which radiatively coupled to wafer 14
through a window 22 which can be transparent to visible light, for
example, quartz or sapphire. Radiant heater 20 can be one of several types
currently known in the art, e.g. tungsten-halogen or an arc lamp. Wafer
support 17 supports the wafer a small distance from window 22. Other
energy sources can be coupled to the wafer 14 or the processing chamber 12
and will be described in detail below.
Processing module 10 also contains a plurality of ECR plasma formation
regions 48. An ECR plasma is generated in each plasma generating region 48
and the position of these regions results in a reactive plasma which is
distributed uniformly around the circumference of the processing chamber
12. Although the number of plasma generating regions 48 shown is 6, any
number of regions could be used. The plasma products then flow diffusively
passed a suppression grid 66 into main transfer chamber chamber 34.
Suppression grid 66 merely suppresses the microwave power transfer into
the main transfer chamber 34 but does not affect the flow. Main transfer
chamber 34 reduces the ion loss during transfer reduces contamination due
to reactant interaction with the walls of the main transfer chamber and
allows mixing of all reactants in an embodiment which is free of
electromagnetic or magnetic fields. Both the main transfer chamber 34 and
the plurality of ECR plasma formation regions 48 will be described in
greater detail below.
A process gas is supplied through gas injectors 50. Gas injectors 50 are
plates with small holes made in them such that a uniform reactant gas flow
rate exists at the exit of the gas injector 50. It is activated to a
plasma state by applying a microwave energy through a plurality of
antennae 52 which are downstream of gas injectors 50. The reactant gas
supplied to each of the gas injectors can be individually controlled to
allow the generation of several reactive plasmas with separate control of
each.
Each of the plurality of antennae 52 described above is optimally spaced
from its corresponding gas injectors 50 for the most efficient power
transfer to the reactant gas each of the antennae 52 is supplied with
microwave energy via a conductor 54, e.g. coaxial cable each is
encapsulated in a sheath 58 made of a non-conductive material, e.g.
sapphire and is movable axially inside sheath 58. Optimal power transfer
of the microwave energy to the injected gas and chamber is achieved
through the the adjustment of an adjustable tuning probe 56 and its
respective microwave antenna 52 which is contained in sheath 58. The
microwave antennae 52 are cooled by circulating gas through supply ports
60 and returns 62.
The bottom of the main transfer chamber 34 is terminated by a window 72
which allows radiative coupling of electromagnetic energy sources in the
visible range (e.g., ultraviolet energy or excimer LASER). Each energy
source can be controlled independently of the ECR plasma formation region
48 and operated either simultaneously or serially, in any order. When such
an energy source is coupled to the wafer through window 72, an inert
purge, (e.g. argon) is applied to the inner wall of the window 74 via
purge ports 76. The window also allows various non-contact, real-time
measurements of the wafer 14, (e.g., interferometric temperature
measurement).
FIG. 4 shows another useful embodiment of the multipolar ECR processing
module 10. In this embodiment, wafer 14 is conductively heated or cooled
by a substrate 24. Wafer 14 is supported in substantial contact with
substrate 24 by wafer support 17. Substrate 24 and, consequently, wafer 14
can be heated by resistive heater 26 or cooled by cooling water supplied
to the substrate through cooling water supplies 28 and return 30. This
arrangement allows optimal temperature control process no matter what
combination of multiple energy sources is coupled to the wafer 14, and
process chamber 12. Therefore, the coupling of these other energy sources
into the processing chamber 12 and to the wafer 14 allows a broader range
of processes to be performed than the single power source processing
module, for example, low temperature depositions, anisotropic etching. The
listed energy sources have been shown as examples of how multiple energy
sources can be coupled in to this processing module 10, however, other
energy sources and combinations may provide significant processing
flexibilty and efficiency.
FIG. 5 shows a horizontal cross section of section A--A' of main transfer
chamber 34 of either FIGS. 3 or 4. The projected image of the wafer 19 is
shown concentric with the main transfer chamber 34 inner wall 36. Main
transfer chamber 34 inner wall 36 is properly passivated (e.g. hard
anodized aluminum) and has a radius somewhat greater, for example 50 mm,
than the radius of the projected image of the wafer 19. Inner wall 36 can
be cooled if necesssary using cooling water supplies (not shown). A
plurality of individual main transfer permanent magnet bars 43 surround
the inner wall 36. In this embodiment, magnet bars 43 are polarized along
a radius of the main transfer chamber 34. This generates magnetic flux
lines parallel to the face to be processed 16 of wafer 14. The inner
surface 42 of adjacent magnet bars is oppositely polarized which results
in magnetic cusp being formed which confines the plasma via magnetic
mirror effects. The intensity of the magnetic flux and thus the
penetration of the magnetic cusps into the main transfer chamber 34 can be
adjusted by decreasing the thickness of the magnet bars or inserting iron
plates (not shown) in the radial directions between magnet bars 38 and
connecting them to external cylinder 46 which can be fabricated of any
magnetic material, e.g. iron.
FIG. 6 shows a horizontal cross section A--A' another embodiment of the
main transfer chamber of FIGS. 3 and 4. It is similar to the embodiment
shown in FIG. 5, however, the magnets 43 are polarized perpendicular to
the radius of the main transfer chamber 34. The lines of flux are still
parallel to the face 16 of the wafer 14. This configuration generates a
magnetic mirror which contains the plasma.
FIG. 7 shows a horizontal cross section of section B--B' of plasma
formation region 48 of either FIGS. 3 or 4. The projected image of the
main transfer chamber inner walls 37 and the projected image of the wafer
19 is shown concentric with the plasma formation regions 48. Each ECR
plasma formation region 48 has a gas injector 50, a microwave antenna, and
a sheath 58 which were described above and each 48 contains a first
sidewall magnet 78 and a first backwall magnet 90. A second sidewall
magnet 80 and a second backwall magnet 92. These magnets are usefully
formed of a permanently magnetic material (e.g. a ceramic) covered by a
nickel coated pure iron (soft magnetic material). Each ECR plasma
formation chamber 48 has a trapezoidal shape as shown in FIG. 7. This
trapezoidal shape, the magnet arrangement and the gradient in the
thickness of the magnets results in the existence of a graded magnetic
(i.e., a much higher magnetic field at the end wall) field. Consequently
an ECR region in only one portion of the ECR plasma formation region 48
(for example, as is well known, where a 2.450 GHz energy signal is applied
ECR will occur where the magnetic flux is 875 Gauss).
FIG. 8(a) shows a cross section of section C--C' i.e. the backwall of one
of the plasma formation regions 48 of FIG. 7. As mentioned above each ECR
plasma formation region has a number of permanent magnets around is
periphery. The first backwall magnet 90 and the second backwall magnet 92
are polarized along the radius of the main tranfer chamber 34 and have
opposite polarities.
FIG. 8(b) shows a cross section of section D--D' of the plasma formation
region 48 of FIG. 7. First top magnet 82, first side magnet 76, first
bottom magnet 86 have which are themselves all perpendicular to the radius
of the main transfer chamber and all are in the same direciton, second
side magnet 78, second top magnet 84, and second bottom magnet 88 have
parallel polarity axis. This creates magnetic cusps which contain the
plasma on the top, bottom and at the end of the plasma formation region
48.
FIG. 9 shows horizontal cross section A--A' of the plasma formation region
48 chamber of another useful embodiment of the processing module 10 of
FIGS. 3 and 4, i.e., cross section of section A--A'. This embodiment is
similar to that shown in FIG. 7, except that it shows the polarity axis of
each of the magnets generally parallel to the radius of the plasma
formation regions 48.
FIGS. 10(a) and (b) show vertical cross section E--E' and F--F' of a useful
embodiment of one of the plasma formation regions of the distributed
multipolar ECR processing module of FIG. 9. It is analogous to the
configuration shown in FIGS. 8(a) and (b) and performs the same function.
FIGS. 11 shows horizontal cross section B--B' of another useful embodiment
of one of the plasma formation regions 48 of the distributed multipolar
ECR processing module 10 as shown in FIGS. 3 and 4. It is analogous to the
embodiments 7 and 9 and differs in that the plasma formation regions 48
are no longer partitioned. A minimal array of antennae 52 and gas
injectors 50 are arranged, as shown in FIG. 11, to obtain the best
microwave power matching. A suppression grid 66, as shown in FIG. 11, can
be used to suppreess the microwave power transmission from the plasma
formation region 48 to the main transfer chamber 34.
FIGS. 12(a) and (b) show vertical cross sections G--G' and H--H' of one of
the plasma formation regions of the distributed multipolar ECR processing
module embodied in FIG. 11. In FIG. 12(a) magnets 90 and 92 are polarized
along an axis parallel to the radius of the plasma formation region 48.
The top end magnet 90 the bottom end magnet 92 have opposite polarities.
The first bottom magnet 86, the first top magnet 82 are polarized
vertically and perpendicular to the radius of plasma formation regions 48.
FIG. 13 shows a vertical cross section of a useful embodiment of one of the
plasma formation regions of the distributed multipolar ECR processing
module also embodied in FIG. 11, and FIGS. 12(a) and (b). FIG. 13 shows
another useful embodiment of the plasma formation region 48 which is a
cross section of section J--J' of plasma formation region 48 as shown in
FIG. 11. In this embodiment, the top magnet 82 and bottom magnet 88 are
polarized substantially vertical and substantially perpendicular to radius
of the plasma formation region 48. The first end magnet 90 and the second
end magnet 92 have a polarity axis horizontal and parallel to a radius of
the plasma formation chamber 48 and opposing polarities. The magnetic
lines of flux are vertical and graded. The differences in the flux from
the end to the interface with the main transfer chamber 34 is graded and
again forms ECR only in one region and allows diffusion in the main
transfer chamber 34.
FIGS. 14(a) shows horizontal cross section A--A' of a useful embodiment of
the plasma formation regions of the distributed multipolar ECR processing
module also embodied in FIG. 11. This embodiment uses top ring magnets
45(a), 45(b) and sidewall magnets 45(c) and 45(d) with their polarities as
shown in FIG. 14(a). FIG. 14(b) shows a vertical cross section K--K' of
FIG. 14(a) which shows bottom ring magnets 45(e) and 45(f).
This processing module can be utilized in conjunction with advanced vacuum
processing systems such as that disclosed in U.S. Pat. No. 4,685,999,
issued Aug. 11, 1987 or any other single wafer processing module or
modular processing system.
OPERATION
In operation, a wafer 14 is transferred into the processing chamber 12.
Wafer 14 is then radiatively heated through window 22, if necessary, for
the particular process by supplying electrical power to radiant heater 20.
If a the embodiment in use has other multiple energy sources, such as the
RF power source 32, an ultraviolet energy source or an excimer LASER, they
can be activated, as desired. When the wafer 14 is at the appropriate
temperature as determined, for example, by a non-contact, real time
measurement through window 74, appropriate process gasses can be supplied
to the plasma formation regions 48. The types of process gas or gasses
depend on the type of processing to be performed. A variety of process
gasses can be admitted to each of the plasma formation regions 48 via gas
injectors 50, if desired, for plasma generation as indicated below. In
addition, if desired, additional process gasses can be admitted to the
vicinity of the face to be processed 16 via non-plasma gas injectors 96.
After the process gas flows have been initiated, microwave power is
supplied to antennae 52 through conductors 54, as desired, to generate a
plasma in the plasma formation regions 48. As described above, the
combination of the microwave power and magnetic flux leads to the
generation of electron cyclotron resonance. The plasma products then flow
by diffusion from the plasma formation regions 48 into the main transfer
chamber 34 while being conducted away from t the walls of the plasma
formation chamber 48 by the arrangement of permanent magnets as described
above. After passing through the suppression grid 66 and into the main
transfer chamber 34, the ECR plasma products are conducted away from the
inner wall 36 of the main transfer chamber 34 by the action of the
permanent magnets as described above.
After the desired process is complete the microwave power source and other
power sources can be shut off. The processing chamber 12 can be purged
using either the gas injectors 50, the non-plasma gas injectors 96, or
purge ports 76. Multiple, sequential processing steps can be performed by
varying the combination of the power sources and the process gasses. When
all of the desired processing is complete, the wafer 14 is transferred
from the processing chamber 12, to e.g. a load lock and patentailly so.
EXEMPLARY PROCESSES
The processing module 10 can perform different, as well as multiple
sequential processes. Processing module 10 is capable of performing, for
example, low temperature chemical vapor deposition, low temperature
epitaxial growth, surface cleaning, and anisotropic etching.
A typical low temperature chemical vapor deposition process could be the
deposition of silicon nitride on mercury cadmium telluride. Nitrogen is
passes through the activated in the plasma formation chamber 48 using 50
watts of microwave power and flows through the main transfer chamber 34 to
the process chamber 12 where silane is then added to the process chamber
through the non plasma gas injectors 96. The result is silicon nitride
thin film with no substrate heating required.
A low temperature epitaxial layer could be grown using argon passed through
plasma formation chamber 48 along with silane and hydrogen being pased
through the non plasma gas injectors 96. The pressure in the chamber could
be 1.times.10.sup.-3 at 750.degree. C.
Several surface cleanup processes are possible using porcessing module 10.
A clean up of organics and hydrocarbons can be accomplished by passing
oxygen through the plasma formation chamber 48. A clean up of any native
oxide or oxide grown during the first clean up step can then be performed
in the same chamber as the first clean up step by passing hydrogen through
plasma formation chamber 48. Finally, a clean up of mettalic contaminants
can be performed by passing argon through the plasma formation chamber 48
and adding either hydrochloric or hydrofluoric gas to the process chamber
12 through the non plasma gas injectors 96.
Another typical low temperature chemical vapor deposition process is oxide
planarization technology for deposition of a planarized oxide layer on a
surface having an uneven surface, e.g. hills and valleys. In this process,
oxygen and argon are activated in plasma formation chambers 48. Silane is
added through the non plasma gas injectors 96 to the process chamber 12. A
large RF signal is applied to the substrate for a short planarization time
which effects the actual planarization.
One possible anisotropic etch process could be the etching of silicon
dioxide with selectivity to silicon. This is accomplished by passing
C.sub.3 F.sub.8 gas through the plasma formation chambers 48 and using 60
watts of microwave power as well as 200 volts peak to peak RF at 800 kHz
and 5.times.10.sup.-4 Torr.
Another possible anisotropic etch process could be the etching of silicon.
This is accomplished by passing SF.sub.6 and argon gas through the plasma
formation chambers 48 and using 600 watts of microwave power as well as
100 volts peak to peak RF at 13.56 MHz and 3.times.10.sup.10-4 Torr.
Unless specifically stated otherwise above the power and frequencies used
for RF and W plasma and ultraviolet light can be widely varied, as can the
other process parameters.
The products of the processing the wafer 14 can be electronic devices, for
example, integrated circuits or discrete semiconductor devices. Once the
processing is completed the wafers are divided into devices. The circuits
and devices are enclosed into packages, for example, as shown in U.S. Pat.
Nos. 4,465,817 issued to Orcutt et al on Aug. 14, 1974 and 3,439,238
issued to Birchler et al on Apr. 15, 1969, which are incorporated hereinto
by reference. These packages are then utilized in the construction of
printed circuit boards. The printer circuits boards, which cannot operate
without the packaged integrated circuits and devices to perform their
intended functions, are the required electrical components within
computers, photocopiers, printers, telecommunication equipment,
calculators, and all of the other electronic equipment which are an
essential ingredients of the electronic and information age. Thus
electronic equipment cannot function with the circuits and devices.
Although the invention has been described and illustrated with a certain
degree of particularity, it is understood that the present disclosure has
been made by way of example only and that numerous changes in the
combination and arrangement of parts may be resorted to without departing
from the spirit and scope of the invention as hereinafter claimed.
* * * * *
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