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.

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.

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.