U.S. patent number 3,783,822 [Application Number 05/251,931] was granted by the patent office on 1974-01-08 for apparatus for use in deposition of films from a vapor phase.
Invention is credited to John S. Wollam.
United States Patent |
3,783,822 |
Wollam |
January 8, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
APPARATUS FOR USE IN DEPOSITION OF FILMS FROM A VAPOR PHASE
Abstract
Separate platform discs for carrying workpieces or substrates
such as slices or wafers of semiconductor material in a deposition
environment are moved in a common circular orbit and rotated by the
action of two co-axial annular support surfaces upon which each
disc rests at opposite areas of the lower periphery of the disc,
one of these support surfaces being driven with respect to the
other in rotation about the axis common to the two annular
supports. The temperature of the discs and/or substrates is
maintained by proximity to a heat or other energy source or sink,
with deposition occurring on the exposed upper surface of the
substrate resting on the disc.
Inventors: |
Wollam; John S. (Acton,
MA) |
Family
ID: |
22953985 |
Appl.
No.: |
05/251,931 |
Filed: |
May 10, 1972 |
Current U.S.
Class: |
118/725;
118/730 |
Current CPC
Class: |
H01L
21/68785 (20130101); H01L 21/6835 (20130101); H01L
21/68764 (20130101); H01L 21/67098 (20130101); C30B
25/14 (20130101); C30B 25/08 (20130101); C30B
25/12 (20130101); H01L 21/68771 (20130101); C23C
16/4584 (20130101); H01L 2924/3025 (20130101) |
Current International
Class: |
C30B
25/08 (20060101); C23C 16/458 (20060101); C30B
25/12 (20060101); C30B 25/14 (20060101); H01L
21/687 (20060101); H01L 21/683 (20060101); H01L
21/67 (20060101); H01L 21/00 (20060101); C23c
013/08 () |
Field of
Search: |
;118/48-49.5,500,503,53,319 ;117/107.1 ;269/55-57 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kaplan; Morris
Claims
What is claimed is:
1. In apparatus for use in uniformly treating the surfaces of
separate workpieces, a plurality of separate platform discs for
carrying the workpieces in a treating area and means in combination
therewith comprising,
first and second parts on a common axis for providing first and
second spaced concentric support surfaces, respectively, for the
disc,
each disc being large enough to span the space between said support
surfaces and rest at the bottom periphery of the disc at opposite
points thereof on the first and second surfaces, and
means for driving one of said disc support surfaces in rotation
about the common axis relative to the other support surface,
whereby the discs move in an orbit about the common axis and each
disc rotates on its own axis in the treating area
two sets of said platform discs being provided, an inner set and an
outer set,
the inner set resting on the first and second disc support
surfaces,
a third disc support surface for the outer set of discs on said
second part,
a fourth disc support surface for the outer set of discs on a third
part concentric with the first and second parts, and
drive means coupled to said second part for producing a relative
rotational motion about the common axis of the second part,
relative to the first and third parts,
whereby the inner set of discs moves in one orbit about the common
axis, the outer set of discs moves in a large orbit about the
common axis and each disc in both sets rotates on its own axis.
2. Apparatus as in claim 1 wherein,
the first and third parts are stationary and the second part is
driven in rotation.
3. Apparatus as in claim 2 wherein,
the first and third parts are annular plates the outside diameter
of the first plate being less than the inside diameter of the third
plate and defining an annular space in between in which the second
part is located,
the first annular support surface is substantially at the inner
edge of the first plate, and
the fourth annular support surface is substantially at the outer
edge of the third plate,
whereby a substantial area of the first and third parts are
adjacent the bottoms of the discs in the first and second sets,
respectively.
4. Apparatus as in claim 3 wherein,
the second part is attached to the end of a cylinder concentric
with the common axis, and
the drive means connects to the other end of the cylinder.
5. Apparatus as in claim 15 wherein, the apparatus is in a housing,
means are provided for introducing a vapor into the housing for
treating the workpieces.
6. Apparatus as in claim 1 and further including,
electrical heater elements contiguous with the first and third
parts for applying heat thereto.
7. Apparatus as in claim 1 wherein,
the discs are composed of a material relatively highly susceptible
to predetermined radiation,
means are provided for directing said radiation to the discs to
heat the discs, and
the first and second parts are made of a material not relatively
highly susceptible to the radiation.
8. Apparatus as in claim 6 wherein,
the discs are of high purity iron.
9. Apparatus as in claim 7 wherein,
the radiation is rf radiation, and
the discs are composed at least partially of graphite.
Description
This invention relates to apparatus used in the formation of films
on workpieces such as substrates of semiconductor material where
the workpieces are exposed in an environment of vapor or gas to be
etched or to produce a condensed film on the substrate. The
invention is particularly applicable to the deposition of films of
material formed at the substrate surface by a chemical reaction of
gaseous substances, wherein the chemical reaction which produces
the material of the film is initiated or enhanced by heat or other
energy imparted to the reactants at or near the surfaces to be
coated.
In semiconductor technology, the treatment of a substrate or slice
or wafer of semiconductor material often includes etching or the
deposition of films from the vapor phase such as epitaxial
single-crystal silicon, polycrystalline silicon or metals, or
amorphous silicon dioxide, or silicon nitride, or other films on
the substrate. The deposition occurs when the wafer is heated while
exposed to a mixture of gaseous materials which react to form a
condensible substance which then deposits on the wafer. The
uniformity of these films is highly dependent upon the success
achieved in eliminating or minimizing variations in temperature
across the surface of the wafer and eliminating or minimizing
differences in flow and composition of the vapor or gaseous
reactant materials at the wafer surfaces.
Methods of eliminating or minimizing variations in the factors
affecting film uniformity have been the subject of much study and
experimentation. Some efforts to ensure that all wafers in a
multi-wafer deposition apparatus, or that all areas of a single
wafer in a lot of wafers, are exposed to essentially indentical
conditions during deposition have entailed provision for the
movement of rotation of the wafer or wafers and/or the source of
the gaseous materials, with the objective of averaging out the
effects of variations in these conditions. Some of these efforts
have included a planetary rotating system supporting the wafers
during the deposition process.
Heretofore, some planetary drive systems used to move the wafers
throughout the gaseous and thermal environment during deposition
have consisted of a multitude of planetary gears with a sun gear
inside the planetary orbit and a ring gear outside the planetary
orbit. Either the sun gear or ring gear is held stationary while
the other is rotated to move the planet gears in orbit and at the
same time rotate each about its own axis. The planetary gears carry
the wafers or substrates and so they are, in effect, disc shaped
orbiting, rotating platforms for supporting the wafers in the
gaseous and thermal environment during deposition. The wafers are
heated to control the rate of deposition by heating the planetary
gears which carry the wafers and so there is a substantial amount
of deposition and formation of matter on the gears as well as on
the wafers. This raises the requirement for frequency cleaning
and/or replacement of the gears.
These planetary rotating systems using orbital gears as described
above are limited in temperature by the characteristics of
materials suitable for use in constructing gear drives. Materials
of sufficient strength and toughness to perform well as planetary
gears are usually not appropriate for use in vapor deposition
apparatus, while materials such as quartz, alumina, silicon
carbide, silicon, or graphite which are suitable for the high
temperatures, sometimes required for a particular process, cannot
be used for constructing gear drive systems, because they are
either not machineable, or are too brittle or too soft for
satisfactory operation.
It is one object of the present invention to provide a planetary
rotating system for carrying a multitude of substrates in an
environment for etching or deposition of films on the
substrate.
It is another object to provide such a planetary rotating system
which does not have any gears exposed to the gaseous and thermal
environment needed for etching or deposition.
It is another object of the present invention to provide a
structure for carrying substrates during etching or vapor
deposition on orbiting rotating platforms, each platform
experiencing no more stress in operation than that imposed by the
platforms own weight and the weight of the substrate or substrates
carried thereon.
It is another object to provide such a planetary rotating system
for etching substrates or for vapor deposition on substrates,
wherein deposition on the planetary support disc for the substrates
produces little or no deleterious consequences.
It is another object of the present invention to provide a
planetary structure which allows the orbiting components to be
fabricated of materials which are not usually incorporated into
gear drive systems, including materials such as quartz, alumina,
silicon carbide, silicon, or graphite.
It is another object to provide a planetary rotating system for
supporting and heating substrates in an etching or a deposition
process in which all moving parts in the vicinity of the etching or
deposition area, exposed substantially to the etching or the
deposition environment, are driven by simple friction forces.
It is another object of the present invention to provide etching or
deposition apparatus having orbiting rotating platforms for
substrates, the platforms being heated or maintained at a
predetermined temperature by proximity to energy sources or a
temperature sink to maintain the substrates at the predetermined
temperature; the apparatus being so constructed that it is readily
disassembled for cleaning and/or replacement of parts.
It is another object to provide an etching or deposition system for
substrates having at least one set of orbiting rotating platforms
for the support of substrates in an atmosphere of gases and vapors
which are fed into a reaction space above the substrates via an
axial conduit supported by the base of the apparatus, whereby a
cover closing the apparatus does not have any connection to sources
of the gases and vapors.
Embodiments of the present invention described herein include
single and double circular arrays or sets of orbiting, rotating
disc platforms for carrying substrates during etching or deposition
on the exposed surfaces of the substrates, the platforms being
heated to heat the substrates as a control of the etching or the
deposition rate and all movement of the discs being induced by
friction forces. Thus, deposition on the discs or on the parts in
contact therewith does not interfere with operation of the
apparatus and the discs can be made of the most suitable materials
available both from the view of inertness of the material to the
deposition environment and the effectiveness of heating the discs
and/or substrates either by the transfer of heat energy, or by
induced electrical energy or radiation, in an effort to achieve
uniform temperature distribution throughout each disc and from disc
to disc and, therefore, throughout all parts of all substrates
concerned. A substantially uniform mixture of vapor and/or gaseous
material for the etching or the deposition is produced in the space
above the discs either by introducing the vapor or gas through
ports in a lid enclosing that space or by carrying the vapor or gas
through axial conduits supported by the base of the apparatus and
extending into and discharging into the reaction space.
Other objects and features of the invention will be more apparent
from the following specific description of several embodiments of
the invention. These embodiments represent the best known uses of
the invention and are illustrated by the figures in which:
FIG. 1 is a plan view of one embodiment showing apparatus with the
cover removed revealing four planetary disc-shaped platforms driven
in orbit and rotation by a central simple friction drive race and
heated by induction coils below the discs;
FIG. 2 is a front sectional view of the apparatus in FIG. 1 shown
with the cover attached whereby vapor and gas is introduced through
ports in the cover;
FIG. 3 is a front sectional view of apparatus similar to the
apparatus in FIGS. 1 and 2 with the discs tilted so that the
substrates face toward the axis of the apparatus;
FIG. 4 is a front sectional view of another similar embodiment
wherein the discs are tilted so that the substrates face away from
the center of the apparatus;
FIGS. 5 and 6 are plan and front sectional views of another
embodiment of the invention including two sets of orbiting platform
discs having a common drive ring or annular support surface, all
drives to the discs being simple friction forces, and an axial
rotating branched conduit, or nozzle array, for carrying gaseous or
vapor deposition materials into the deposition space above the
discs and mechanically stirring the gas by a drive which is common
to the drive for the disc drive ring; and
FIGS. 7 and 8 are plan and front section views of another
embodiment having heater elements imbedded in the supports for the
orbiting discs, leveling posts for the supports, a common drive
ring for the discs which has very low thermal mass and low thermal
conduction and axial conduits supported by the base of the
apparatus for carrying more than one gas or vapor into the reaction
space above the discs for mixing and etching or deposition on the
substrates carried on the discs.
Turning first to FIGS. 1 and 2, there is shown apparatus for
etching or for carrying out vapor or gaseous deposition on the
exposed surfaces of substrates which may be wafers or slices of
semiconductor material carried on a single set of orbiting,
rotating discs driven in orbit and rotation by simple friction
forces and heated by an induction coil below the discs. Apart from
the parts of the apparatus shown in this and other embodiments of
the invention described herein, the apparatus can be used for other
treatment of the substrates in addition to etching and deposition.
For example, the apparatus can be used for sputtering processes
whereby material is added to or removed from the exposed surfaces
of the substrates. The apparatus in FIGS. 1 and 2 consists of a
base plate 1 and a cylindrical housing 2 for containing and
supporting the induction heating coil and the orbiting, rotating
discs. A cover 3 is fitted on top of the housing defining the
reaction space 4 above the discs and selected gases and vapors are
introduced into the space by a mixing port 5 at the top of the
cover centrally located along the axis 6 of the apparatus.
Each of the platform discs 7, 8, 9, and 10 such as disc 7 is a
composite or assembly of two discs; a quartz disc 11 beneath a
graphite susceptor disc 12. The lower or quartz disc in each of
these oribiting disc platforms rests on an inside annular drive
surface 14 which is part of the central support rotor 15, and also
rests on the outer annular support surface 16 which may be part of
the lower housing 2. The driven surface 14 is defined by a step 17
in the support rotor 15 (also called the drive race) and the outer
annular support surface 16 is defined by a step 18 on the inside of
the lower housing 2 (also called the fixed race). The orbiting disc
assemblies are prevented from leaving the desired circular orbit by
the rise 19 on the step 17 and by the rise 20 on the step 18.
The graphite susceptor discs, such as discs 12, on each of the
platforms discs 7 to 10 are directly heated by radiation from a
radio -frequency (rf) induction coil 21 below the discs. This coil
is powered by energy from an rf source 22 which is outside of the
apparatus. Transmission lines 23 couple rf energy from the source
to the coil. The coil is substantially flat and may be disposed
immediately beneath the composite platform discs 7 to 10 in close
proximity to the quartz discs, such as quartz disc 11, on the
bottom thereof. The rf coil 21 is preferably supported over a
highly electrically conductive plate 24 which does not absorb, but
reflects the rf energy towards the platform discs 7 to 10. Between
the rf coil and the discs may be interposed a dielectric plate 25
made of a material which is substantially transparent to the rf
energy and so does not reflect nor absorb the energy, but tends to
focus the rf energy onto the graphite susceptor disc above. The
quartz disc beneath the graphite susceptor disc also does not
absorb or reflect the rf energy and tends to focus it into the
graphite susceptor. The support rotor 15 is also preferably quartz
and so is the drive shaft 26 which extends through the base plate 1
to a gear box 27 and drive motor 28. Thus, the materials composing
the parts surrounding the rf coil are such that these parts are not
heated by the rf energy; only the graphite susceptor 12 on which
the substrate (which may be a wafer or slice of semiconductor)
rests is heated. The quartz disc 11 which is the bottom part of
each of the platform discs 7 to 10 provide a hard non-wearing
surface for contact with the driven and stationary annular support
surfaces defined by the driven and fixed races, 14 and 16
respectively, and so there is no frictional wear on the softer
graphite susceptor material. Other hand refractory materials such
as alumina or silicon carbide could be used in place of quartz for
the quartz discs 11.
This apparatus is particularly designed for high temperature
deposition processes up to about 1,300.degree. C, for example,
deposition reactions such as the pyrolysis of silane or silicon
tetrachloride in the growth of epitaxial silicon films. At this
temperature range, quartz and silicon carbide coated graphite are
satisfactory for use in enclosing the reaction or deposition space
4 as they are substantially inert to the vapors and gases used and
do not produce undesirable gases or vapors. The rest of the parts
of the apparatus below the reaction space 4 are compatible with the
environment in that they absorb no power from the rf field which
heats the graphite susceptors in the orbiting platform discs.
Accordingly, these parts are made of materials which are either
good insulators such as alumina or other ceramics, or good
conductors of electricity such as copper, silver, or red brass.
These same considerations apply to the materials used in the
construction of the vapor and gas ports 5 and the drive shaft 26.
They apply to a lesser extent to the base plate 1 and housing 2
which are substantially shielded from the rf coil by the plate
24.
This shielding effect as well as the position of the rf coil may be
varied by moving the plate 24 up and down on its support legs
29.
In operation, the motor 28 drives the shaft 26 with its support
rotor 15 in the counter-clockwise direction indicated by arrow 30
as viewed from above. The frictional forces between the bottom
peripheral edge of the quartz disc, such as 11, under each of the
platform discs 7 to 10, where the quartz disc of each engages the
annular support surface 14, causes each of the platform discs to
rotate in the clockwise direction, indicated by arrow 30' as viewed
from the top and so the discs roll along the outer annular support
surface 16 following an orbital path indicated by arrow 30' in the
counter-clockwise direction about the axis 6 as viewed from the
top. Clearly, each of the composite platform discs 7 to 10 is
supported at small areas at opposite ends of the bottom periphery
of the composite disc and so there is a minimum of heat conduction
from the disc to the points of support.
The platform discs 7 to 10 are spaced from each other by their own
dimensions as they substantially fill the annulus between the two
annular support surfaces 14 and 16 with equal contiguous circles
and they are constrained in the orbital path by the rises 19 and 20
on their rotating and stationary races. This orbiting, rotating
motion imparted to the substrates, such as semiconductor wafers, on
the graphite susceptors insures a uniform temperature thorughout
the exposed surface of the substrates and insures an average
uniformity in the flow and composition of the reactant gases
delivered to the exposed surfaces.
Modifications of the apparatus shown in FIGS. 1 and 2 for tilting
the platform discs 7 to 10 relative to the axis of the apparatus so
that the discs tilt toward or away from the axis are illustrated in
FIGS. 3 and 4. In FIG. 3, the housing 32 on base 31 provides an
outer annular support surface 33 which is raised above the inner
annular support surface 34 defined by the driven race 35 on the
support rotor 36. The dielectric and metal plates 37 and 38 between
which the rf coil 39 is sandwiched are conical in shape, the cone
being upside down, to fit the contour defined by the inward tilt of
the discs 7 to 10. This configuration tends to promote a normal
incidence of flow of the ingredients for deposition to the
deposition surfaces of the workpieces carried by the discs 7 to
10.
Another purpose for tilting the discs and workpieces toward the
axis is that this configuration lends itself conveniently to
heating the substrates by infra-red or other radiation whose source
is exterior to a transparent cover of the reaction chamber.
The structure shown in FIG. 4 tilts the discs away from the axis.
Here, the housing 40 on the base 41 provides the outer step or race
42 including annular support surface 43 lower than the inner
annular support surface 44 on the support rotor 45. The dielectric
and metal plates 46 and 47 with the rf coil 48 in between have
conical shapes to conform with the tilted positions of the discs.
Here, the conical confirmation of these parts is upright. The
purpose for tilting the substrates away from the axis 6 may be to
insure that there is no direct or normal projection of the
ingredients for the deposition reaction onto the exposed surfaces
of the substrates on the disc. Another purpose for tilting the
discs and substrates away from the axis 6 is that this
configuration lends itself conveniently to heating the workpieces
by infra-red or other radiation whose source is exterior to a
transparent wall of the reaction chamber. This configuration also
increases the firctional forces on each disc at the outer race 42.
The quartz disc in each of the support discs abuts the surface or
rise 49 defined by the outer race 42 and since the frictional
forces are greater here, at least because of greater contact
surface, than at the inner driven annular support surface 44, each
disc is inclined to roll along the race 42 without slipping and so
the orbital rate of rotation of the discs in the apparatus is very
constant.
The planetary deposition system illustrated in FIGS. 5 and 6
contains two sets of orbiting rotating platform discs for carrying
the substrates or workpieces, an axial mechanically driven branched
conduit for the vapors and gases supported at the base of the
apparatus for carrying the vapors and gases to the reaction space
above the substrates and resistance heaters attached to stationary
plates beneath the discs for heating the plates so that they in
turn heat the discs resting thereon. This apparatus is particularly
designed for operation in the temperature range of 300.degree. to
600.degree. C. One common deposition reaction carried out at this
temperature range is the reaction of gaseous silane with oxygen to
produce a deposited amorphous film of silicon dioxide. In an
atmosphere of silane and oxygen at temperatures up to 600.degree.
C, ordinary steel can be used and since resistance heaters are used
rather than induction heating, the electrical qualitites of the
materials used for the various parts are not important. On the
other hand, it becomes most important to conduct heat by radiation,
conduction, or convection from the races to the discs and so there
must be an intimacy between the races and discs such as will
accomplish this.
In FIG 6, the base plate 51 carries the whole structure, the
housing 52 and cover 53 serving merely to enclose the
structure.
The inner stationary race and heating plate 54 coaxial with the
axis 55 of the apparatus is supported from the base by support legs
56. This part is circular and contains the inner stationary race 57
which defines the first or inner annular support surface 58 for
supporting the inner edge of the first set of discs 59 consisting
of seven discs in all denoted 60 to 66. The inner plate 54 carries
a ring shaped resistor element 67 beneath on the portion thereof
that extends beneath the annular space occupied by the discs 60 to
66, and so the heater is positioned substantially in registration
with that space and is directly below the first set of discs.
The outer stationary race and heating plate 68 concentric with the
axis 55 provides the outer stationary race 69 which defines the
outer annular support surface 70 for supporting the discs in a
second set of discs 71 at their outer edges. This second set
includes the discs 72 and 73 shown in cross section in FIG. 6. The
outer plate 68 carries beneath it a resistor heater element 74
substantially in registration with the portion thereof that extends
beneath the discs in the set 71 and so the heater element 74 is in
registration with the discs in this set. A support for the plate 68
includes legs 75.
The outer edges of the discs in the set 59 and the inner edges of
the discs in the set 71 are supported by the driven race sleeve or
cylinder 77. The driven races 78 and 79 at the end of this sleeve
for the disc sets 59 and 71 define the annular support surfaces 80
and 81 for supporting discs in the sets 59 and 71, respectively.
These driven support surfaces, 80 and 81, are referred to also as
the second and third support surfaces and the stationary support
surfaces 58 and 70 are referred to also as the first and fourth
support surfaces, respectively.
A ring gear 83 attached to the opposite end of the drive cylinder
77 is driven by planetary drive gear 84 at the end of drive shaft
85 from a gear box 86 driven by motor 87. Drive gear 84 also drives
axial gear 88 connected to the lower end of shaft 89 which supports
the rotating gas nozzles 90 at the other end of the shaft for
conducting vapor or gaseous materials into the reaction or
deposition space 91 above the discs. The shaft 89 passes through an
opening 92 at the center of the inner plate 54, this opening being
just sufficient to pass the shaft without friction and so limit the
escape paths for the dispensed deposition products into the heater
space 93 below the race plates.
The vapors and gases for deposition are introduced to the apparatus
via tube 94 which passes axially through the drive shaft 89 for the
nozzles and empties these ingredients into the nozzle tube 95 in
the interaction space. These vapors and gases are injected into the
interaction space from the nozzle via orifices 96.
The rotating nozzle 90 may include two or four or more arms which
reach across the sets of discs, each having orifices distributed
therealong to insure uniform spraying of the gases and vapors for
deposition over the surfaces of the disc. The nozzle and its drive
shaft are supported on the inlet pipe 94 by bearings such as 97 and
98 at each end thereof. This pipe provides a clear passage without
moving or slipping parts from outside the apparatus to inside the
nozzle in the reaction space 91 above the discs and workpieces. The
nozzles are rotated mechanically as the driven races 78 and 79 for
the inner and outer sets of discs are driven and the arrangement of
gears may quite easily be such that the nozzles rotate in the same
direction or in the opposite direction to the direction of orbiting
of the discs.
With the drive system shown and the planetary drive gear 84 driving
in the direction of arrow 99, the nozzles will rotate in the
clockwise direction viewed from the top as indicated by FIG. 5 and
the race drive cylinder 77 will drive in the counter-clockwise
direction as indicated by arrow 101 in FIG. 5. This will cause both
sets of discs 59 and 71 to orbit in the direction of arrow 101 in
the annular spaces in which they are contained. The inner discs 59
will individually rotate counter-clockwise and the discs in the
outer sets will rotate clockwise as indicated by direction arrows
on the discs in FIG. 5. In this structure, the relative orbiting
and rotational directions of the discs in these sets are determined
by the driven races at the inside of the outer set and at the
outside of the inner set of discs. However, the relative direction
or rotation of the nozzles depends upon the drive mechanism
arranged by the gears in space 93.
Each of the platform discs in sets 59 and 71 preferably contains at
the bottom thereof a projecting disc-shaped protuberance such as
102 on the disc 60. This protuberance or projection projects toward
the extending portion of the race plate immediately below, but does
not touch the extending portion. The only points of contact of the
disc with anything but the workpieces remains still the stationary
and driven annular support surfaces such as 58 and 80 for the disc
60. The purpose of the projection 102 is to place as much surface
area of the disc immediately adjacent, but not touching, the heated
plate 54 as it is feasible so that the heat is carried with
reasonable efficiency by convection, conduction, and radiation from
the plate into the discs.
In operation of the apparatus shown in FIGS. 5 and 6 electrical
power to the heaters is carried via terminals 103 and 104 and
cables 105 and 106 to the heaters 67 and 74. The motor drive drives
the sets of discs carrying workpieces which may be wafers of
semiconductor such as 107 in orbit and rotation while the driven
nozzle dispenses the vapors 108 for deposition in the space 91
immediately above. The effective uniform distribution of heat
throughout the discs is insured by the continual movement and
rotation of each of the discs and so the wafers carried by the
discs are heated uniformly throughout. The vapor and gases for
deposition are distributed evenly throughout the space 91 by the
distribution of the orifices and the stirring action of the
rotating nozzles. This in combination with the heating technique
and motion of the discs insures even deposition on the exposed
surfaces of the wafers 107. Since the only contacting moving parts
are the friction contacts at the annular support surfaces defined
by the stationary and driven races, the effects of deposition on
the parts in the reaction space are insignificant. In the heater
space and drive area 93 beneath, some deposition occurs on the
hotter parts due to gases and vapors leaking into this area.
However, the moving parts which are the gears are not heated and so
they accrue very little deposition.
Another embodiment of the invention containing two sets of rotating
orbiting platform discs and particularly adapted for operation at
the lower temperature range of 300.degree. to 600.degree. C is
illustrated in FIGS. 7 and 8. Here, the vapors or gases 109 for
deposition are introduced to the reaction space 110 axially through
the base and also through a port in the cover. Resistor heater
elements are imbedded in the inner and outer stationary heating and
race plates and means are provided for clearing vapors and gases
from the drive gears in the space 111 beneath the heaters. This
structure is constructed to facilitate quick disassembly to clean
or replace parts and replace the heaters imbedded in the stationary
plates.
All these structures inside the apparatus are mounted to the base
plate 112 and enclosed by the cylindrical housing 113 and cover
114. Some of the reactants for deposition are introduced through
two coaxial pipes 115 and 116 extending through the base and sealed
thereto and into the reaction space 110 where the reactants are
discharged from the pipes. Other vapors or gases may be introduced
through port 117 in the cover.
The inner heating and race plate 118 has the inner annular support
surface 119 for carrying the inner set of discs 120 at the inner
edge of each of the discs such as 121 in the inner set. The outer
heating and race plate 122 provides the outer annular support
surface 123 for supporting the twelve discs in the outer set 124 at
the outer edges of discs in that set such as the disc 125.
In the relatively narrow annular space between the outer plate 122
and the outside edge of the inner plate 118 is located the drive
ring 126 at the end of a thin walled cylinder 127 which extends
toward the bottom of the apparatus into the drive space 111. The
top surface 128 of the drive ring 126 provides an annular support
surface for both sets of discs. This is also referred to as the
driven race. On this surface rest the inner edges of the outer set
of discs and the outer edges of the inner set of discs.
The drive mechanism is similar to the drive mechanism in the
embodiment shown in FIGS. 5 and 6. It may include a ring gear 131
attached to the end of cylinder 127 and engaged by a planetary
drive gear 132 all held in position by a central sun gear 133 and
idling planetary gears 134 suitably placed between the sun gear and
the ring gear. At the planetary drive gear 132 and at the planetary
idle gears thrust bearings such as thrust bearing 135 are provided
against the meshing points of these gears with the ring gear and
sun gear and a support pad such as 136 to the base is provided for
each. The sun gear 133 may be mounted to a bearing 137 attached to
the central pipe 116 which carries deposition ingredients into the
apparatus.
A plate 138 which shields the gears from the deposition gases and
vapors is located inside the cylinder 127 between the bottom of the
inner plate 118 and the gears. This plate is supported by three
pedestals such as pedestal 139 mounted to the base 112. These
pedestals 139 also support the inner plate 118 and parts attached
thereto. Between the shield plate 138 and gears and carried by this
plate is a pipe 140 which conducts an inert purging or cleaning gas
into the gear space 111 and discharges the gas through nozzles 141
which direct the gas particularly to the ring gear 131 clearing the
teeth of that gear of deposition gases and particles which could
tend to clog gears. The inert gas is fed to the ring tube 140
through a flexible tube 142 which goes through the base plate for
external access.
The inner and outer heating and race plates 118 and 122 are
generally washer-shaped, the inner fitting inside the outer and
defining the annular space in between for the drive race ring 126.
To the bottom of each of these plates is attached a plurality of
layers of thermally insulating material such as the layers 143
attached to the bottom of the inner plate and layers 144 attached
to the bottom of the outer plate which thermally insulate the gear
space 111 from the heated plates. These layers are attached to the
bottom of the inner and outer plates by bolts such as 145 and 146,
respectively.
The inner and outer plates with their attached layers of insulation
are each supported from the base 112 by at least three adjustable
support pedestals. The inner plate is supported by adjustable
pedestals such as 139 and the outer plate is supported by
adjustable support pedestals 147. In addition, the inner supports
139 carry the shielding plate 138. Otherwise the support pedestals
139 and 147 are identical.
Each support pedestal such as 147, consists of a pillar 148
attached to the base 112. A support rod 149 screws into the pillar
and is locked thereto by lock nut 151. The rod 149 extends into the
bottom end of a hole 152 bored through the layers of insulator 143
and the plate 122 emerging from the top of the plate beneath the
outer set of discs. This bored hole provides a substantial
clearance for the rod 149 to allow for lateral thermal expansion of
the various parts during operation. The portion of the hole bored
in the plate 122 is tapped and a leveling set screw 155 screws into
this and abuts the end 156 of the rod. With three such support
points provided for each of the inner and outer plates, the plates
can be quickly leveled by merely removing the cover 114 and a few
of the discs to gain access to the screws 155 and then turning
these screws from above to level the plates.
The axial position of the shielding plate 138 carrying the ring
tube for discharging cleaning gas is less critical, however, this
can be adjusted by adjusting the nut 157 on the support pedestals
139.
Heating elements are contained in holes bored in the inner and
outer heating and race plates. These holes are bored through each
plate parallel to the plane of the plate and located so that they
do not cross the taps for the bolts 145 or 146 and do not cross the
holes such as 152 bored for the support pedestals. Three heating
element bored holes such as holes 161 to 163 are provided in the
inner plate 118 and four holes 164 to 167 are provided in the outer
plate 122. The heating elements denoted generally 168 are loaded in
these holes and may be electrical cartridge heaters each made to
the length of the hole in which it is located. The cartridge
heating elements may connect in electrical series or in parallel by
wires which are not shown and which emerge through the base plate
for coupling to an electrical power source. The leads to the
elements are preferably sufficiently long that the inner and outer
heating and race plates can be lifted from their support posts
sufficiently so that the heating elements can be individually
removed from the plates and replaced when necessary. The
disconnection of the lead wires to these elements and reconnection
of the wires to the replacement elements can all be done while the
plates are lifted vertically from the apparatus. Thereafter, the
plates are simply returned to the support pedestals. Once the
plates are correctly adjusted, the levelling set screws such as
screw 155 generally need no further attention but may be readjusted
as necessary to bring the plates into the proper level aspect.
Numerous embodiments of the invention are described herein each
incorporating certain features of the invention whereby certain
advantages for relatively high and low temperature deposition
operation are gained. These embodiments are intended to represent
the best known uses of the invention. The various structural
features described herein with relationship to the different
embodiments may be combined in somewhat different manners from
described herein and some modifications and variations may be made
to these within the state of the art without deviating from the
spirit and scope of the invention as set forth in the appended
claims.
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