Complex Motion Mechanism For Thin Film Coating Apparatuses

Abstract

Apparatus is described for providing complex rotation about three axes of a plurality of objects being coated by deposition. The apparatus includes a frame adapted to be supported within a conventional deposition coating chamber having a source providing within the chamber an atmosphere of molecularly-sized particles of the desired coating material. A substrate holding disc having a face to which a plurality of substrate objects can be secured is mounted to the frame for rotation with the face in line-of-sight of the material source. The disc is mounted to the frame for orbiting about an axis which extends toward the source and rotation about its own axis. Each of the substrate object supporting members on the face of the disc is rotatably mounted thereon for rotation of the surface of the object to be coated about an axis which is oblique to the source. A prime mover is provided causing rotation about the various axes during the coating operation with the result that the surfaces being coated of the substrate objects will receive a uniform coating irrespective of irregularities in such surfaces.

Description

BACKGROUND OF THE INVENTION

This invention relates to the coating of one or more films of material onto a plurality of substrate objects such as microelectronic wafers and, more particularly, to improved apparatus for providing complex motion to substrate objects during the coating operation in order to assure uniform coating of irregular surfaces of such objects.

Many microelectronic components, as well as other objects, are now produced by coating a substrate object or wafer with one or more thin films of a material which is generally an electrical conducting or semiconducting material. In order to achieve the desired film thinness, as well as for other reasons, those working in the field generally effect the coating by forming an atmosphere of molecularly sized particles of the desired coating material in a coating chamber for deposition onto the substrate surface. There are several techniques employed to provide the atmosphere of particles. For example, one which is fairly commonly used is that of "sputtering" the particles from a target electrode of the material by bombarding the target with high energy positive ions. Another technique used to form the atmosphere relies simply on the evaporation of the particles from a body of the material. No matter how the atmosphere of particles is formed, the atmosphere generally does not have a uniform density of the material particles throughout the coating chamber. This nonuniformity is caused by various factors. For one thing, the density of the particles within the atmosphere decreases as the distance from the source of such particles increases. Moreover, the inclusion in the atmosphere of necessary mechanical structures and the like will disrupt the spacial distribution of the particles.

The nonuniform density of the particles within the coating atmosphere can effect the rate of particle deposition and, therefore, the coating rate on substrate objects. That is, the rate of deposition and, hence, coating at any given location within the chamber will depend upon the density of the particles at such location Either time or space varying differences in the density in the chamber will thus cause corresponding changes in the coating rate. Those in the art have therefore been unable to control the uniformity and thickness of an applied coating to the degree that one would like. This is especially true when one attempts to coat a plurality of substrate objects at one time. Such a plurality of objects must necessarily be located at different positions within the particle atmosphere with resulting different coating rates on each object.

Many substrate objects desired to be coated, such as integrated circuit wafers, have irregular surfaces on which the material is to be deposited. These irregularities can further detrimentally affect the uniformity of the resulting coating. That is, the ridges, depressions, etc. in the surface tend to shade one another and prevent deposition at certain locations on the surface while enhancing the deposition at other locations. The result is that for many applications the coated product will not meet designed specifications.

SUMMARY OF THE INVENTION

It is a primary object of the instant invention to assure uniform coating of the surfaces of a plurality of substrate objects subjected to a coating atmosphere. As a particularly salient feature of the invention, it assures uniform coating of a substrate object surface irrespective of irregularities in the surface. In its basic aspects, the apparatus of the invention includes a frame which is adapted to be supported within a conventional coating chamber having a material source to provide a particulate atmosphere within the chamber of the desired coating material. A holder for a plurality of substrates is mounted on the frame for orbiting about a first axis which is spaced from such holder and extends generally toward the source and rotation about a second axis which passes through the face of the holder on which the substrate objects are to be secured. A plurality of separate object supporting means are mounted on a face of the holder which is in the line-of-sight of the source of material. By orbiting the holder during the coating operation about the first axis and rotating it about the second axis as discussed above, all substrates supported on the holder face will be moved throughout the same portion of the coating atmosphere to thereby subject all of the substrate objects to generally the same deposition conditions. In this connection, each of the objects will be moved both laterally of the source and longitudinally toward and away from the source.

Each of the separate object supporting means on the holder is mounted thereon for rotation of the substrate surface to be coated about an axis which is oblique to the source, and means are included for rotating each of the objects simultaneously with orbiting and rotation of the holder about its respective first and second axes. As will become more clear hereinafter, this will assure that all topographical features of each substrate object will be uniformly coated by virtue of such rotation changing the orientation of each object relative to the source. The combination of this rotation of each object on the holder with the orbiting and of the holder about the above-described first and second axes will result in complete uniform coating of a plurality of objects in a controlled environment irrespective of nonuniformities in the coating atmosphere and irregularities in the surfaces of the objects. The apparatus of the invention provides the substrate movement responsible for this uniformity in a quite simple but yet effective manner, and the particular structure providing this motion has other features and advantages which will become apparent from the following more detailed description of a preferred embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the accompanying two sheets of drawings:

FIG. 1 is a partially broken away and sectional side view of a coating apparatus having incorporated therein a preferred embodiment of the apparatus of the invention;

FIG. 2 is an enlarged view taken on a plane indicated by the line 2-2 in FIG. 1 and illustrating the rear side of the substrate holder element of the invention;

FIG. 3 is a top sectional view taken on a plane indicated by the line 3-3 in FIG. 1 illustrating a portion of the drive mechanism for the apparatus of the invention; and

FIG. 4 is an enlarged partial sectional view taken on a plane indicated by line 4-4 in FIG. 2 and illustrating details of an object supporting element of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIG. 1 of the drawing, the apparatus of the invention, generally referred to by the reference numeral 11, is shown mounted within a conventional coating chamber 12. Coating chamber 12 is defined by a vacuum envelope 13 mounted upon a base 14 which, in turn, has a vacuum system (not shown) connected thereto for evacuating the chamber in accordance with usual practice.

A source for providing an atmosphere within chamber 12 of molecularly sized particles of the desired material is also provided. While this source can be designed to provide the particulate atmosphere in any appropriate manner, the source is diagrammatically shown for illustrative purposes as a crucible 16 for holding a body of the material for evaporation. Means (not shown) are included for heating the material within crucible 16 in order to evaporate the same to provide the particulate atmosphere of the material. It will be appreciated that although one source of coating material is illustrated, a plurality of such sources may be provided to enable either simultaneous or sequential coating of substrate objects with different materials.

In accordance with conventional practice, a shutter mechanism 17 is provided to enable selective blocking of the upward flow of particles of the coating material toward the substrate objects. More particularly, a shutter plate 18 is supported at a location blocking line-of-sight between crucible 16 and the substrate objects. Plate 18 is mounted via a gear transfer case 19 on a shaft 21 which is connected to suitable mechanism (not shown) outside of base 14 for rotation by a flexible rotary cable 22. Plate 18 is selectively rotatable by shaft 21 to an open position, i.e. to a location out of the line-of-sight of evaporated material flowing from source crucible 16.

After the coating chamber 12 is conventionally evacuated, energization of the source of the coating material and movement of the shutter plate 18 to the open position will result in molecularly sized particles of the coating material flowing upward from the source and providing a particulate atmosphere of the coating material within the coating chamber. To assure good adherence of the particles to substrate objects, it is preferred that the atmosphere be heated. For this purpose, an annular array of heaters in the form of quartz halide lamps 23 are supported upon a frame ring 24 above the location of the source crucible 16. As illustrated, lamps 23 define the perimeter of a passage through which the coating material passes as it travels to the upper portion of chamber 13. An angle bracket shield 26 is associated with each of the lamps 23 to block line-of-sight deposition of coating material from crucible 16 onto the lamps.

As mentioned previously, the density of particles of the coating material in the coating atmosphere will not be uniform throughout the coating chamber 12. For example, the density of the particulate atmosphere will generally tend to decrease as the distance from the source crucible 16 increases. Moreover, in view of the presence of fixtures, such as the shutter arrangement 17 and the lamps 23, the spacial distribution of the particles laterally throughout the chamber will also not be uniform and can be time varying. This nonuniformity in the particulate density will result in nonuniform deposition rates and coatings. The consequential inability to obtain on many substrate objects coatings of a controlled, uniform thickness has placed serious limitations on the usefulness of coating apparatuses of this type. This is particularly true with respect to substrate objects, such as certain microelectronic wafers, which have irregular surfaces on which the coating is to be applied.

The apparatus 11 of the invention is designed to assure uniform coating of a plurality of substrate objects within the coating chamber, irrespective of nonuniformities in the coating atmosphere and of irregularities in the surface configuration of such objects. To accomplish this, the invention provides a predetermined complex motion in a simple manner to each of the objects. Apparatus 11 includes a frame adapted to be supported within envelope 13 of coating chamber 12. More particularly, the apparatus includes a lower frame ring 27 which extends around the inner periphery of chamber 12 adjacent its base and is supported therein by an annular flange 28. A plurality of spaced apart support posts 29 extend upwardly within envelope 13 from frame ring 27 to a location adjacent the top of chamber 12. Such posts act as supporting members to suspend within the chamber the remainder of the structure of the apparatus. Also, as shown, the posts support the ring 24 on which the lamps 23 are mounted.

A plate 31 is supported laterally within the chamber on the upper ends of the posts 29. As best illustrated in FIG. 3, plate 31 is in the shape of a disc with a segment thereof removed for a purpose which will be described hereinafter.

A rotor in the form of a rectangular plate 32 is mounted for rotation on the underneath surface of plate 31 axially of envelope 13. As illustrated, rotor 32 is in opposed, facing relationship to crucible source 16 and is mounted for rotation on an axis 33 which extends toward source crucible 16 and in a plane which is parallel to plate 31 and lateral of such source 16. Throughout this specification, whenever a direction with reference to the source of material is stated, reference to the source is to be construed as reference to the general direction at which the molecularly sized particles emanate from such source.

A pair of hooks 34 projects outwardly from each of the four sides of rectangular rotor plate 32. As illustrated, the hooks 34 of each pair are equally spaced from the axis of rotation 33 of rotor 32 on opposite sides thereof. Each pair of hooks 34 acts as means for removably securing a corresponding arm 35 to rotor 32. In this connection, each arm has at its upper end a pair of oppositely directed ears 36 from each of which protrudes a pin 37 engageable within a corresponding one of the hooks 34.

Each of the arms 35 extends in a direction toward the source 16 and outwardly away from rotor 32. Rotatably mounted on the free end of each arm 35 is a substrate holder in the form of a disc 38. As illustrated, each of the discs 38 is mounted to a corresponding arm at its center for rotation about an axis 39 which extends normally to the disc and through a front face 40 thereof.

Each disc 38 is circumferentially provided with spur gear teeth 41 which mesh with a plurality of pins 42 defining the teeth of a ring bevel gear 43. Bevel gear 43 extends peripherally around the inner wall of envelope 13 at a location below rotor 32. As illustrated, such ring bevel gear 43 is supported in position laterally of chamber 12 as a part of the frame of the apparatus by blocks 44 secured to posts 29.

The substrate holders 38 are annularly disposed within the chamber 12 with the front face 40 of each in the line-of-sight of material emanating from crucible source 16. A plurality of separate objects supporting means are rotatably mounted at discrete locations on the face 40 of each of the discs. More particularly, a circular array of object supporting means are provided on each face 40 with such supporting means being equally spaced from the axis of rotation 39 of the holder.

As a particularly salient feature of the instant invention, each of the object supporting means is itself rotatable with respect to the holder on which it is mounted. That is, each object supporting means is mounted for rotation of the surface of the substrate held thereby about an axis which is oblique to the source. In this connection, and as is shown in FIG. 4, each object supporting means, generally referred to by the reference numeral 46, includes a bearing 47 rotatably mounting a sleeve 48 to its associated holder 38. A spur gear 49 is secured to sleeve 48 on the rear side of holder 36 in order to provide rotation of such object supporting means in the manner described in more detail hereinafter.

Each of the supporting means includes an arrangement by which the substrate object, schematically illustrated as a microelectronic wafer 51, can be easily and quickly secured to or removed from the holder 38. That is, each object supporting means includes a plurality of fingers 52 which project outwardly from the interior of sleeve 48 in order to grip the wafer 51 at selected positions around its periphery. Spring fingers 52 are normally urged toward one another in order to provide the gripping action. More particularly, the fingers 52 are secured to the end 53 of a plunger rod 54 which is normally urged to the right as viewed in FIG. 4 by a compression spring 56 acting upon a piston 57 secured to plunger 54, to draw the spring fingers 52 into sleeve 48, and thereby urge such fingers toward one another.

The spur gears 49 of all of the object supporting means of each holder are coupled with one another and with arm 35 in a manner assuring rotation of each of the object supporting means about its own axis 58 upon rotation of the holder about the axis 39. For this purpose, it will be seen with reference to FIG. 2 that a planetary drive arrangement including a chain 59 connects each of the object supporting means with a gear 60 which is rigid with respect to arm 34 coaxially with the axis of rotation of holder 38. Means for adjusting the tension of the chain 59 is also provided in the form of an idler gear 61 which is adjustably positionable along the length of a slot 62 in order to tighten or slacken the chain. It will be appreciated that upon rotation of holder 38 about axis 39, each of the object supporting means on the holder face 40 will also be rotated about the axis 58 passing through such supporting means and through the surface to be coated of the object being supported.

Driving means are provided for rotating the apparatus about its various axes to provide the desired complex motion. A prime mover, such as an electric motor schematically represented at 66, provides axial rotation via a motion-transmitting flexible cable 67 to a drive rod 68 which extends upwardly within envelope 13 through plate 31. The upper end of drive rod 68 terminates above plate 31 in a gear 69 which is linked by a chain 71 to a drive gear 73. Drive gear 73 is, in turn, axially secured to rotor 32 by a shaft 73 which extends through plate 31 and provides rotation of the rotor about axis 33. A takeup idle roller 74 is mounted on plate 31 to facilitate tensioning of chain 71.

In view of the above construction, energization of motor 66 will provide motion of any substrate object secured within the apparatus upon one of the object supporting means about three different axes. As will become more clear hereinafter, this motion will assure uniform coating of the surface of the object desired to be coated irrespective of irregularities in such surface. More particularly, energization of motor 66 will provide rotation of rotor 32 about axis 33 in view of the linkage discussed immediately above. Since the substrate holders 38 are mounted on the arms 35 for rotation with rotor 32, each substrate object on the holder will therefore be moved laterally through chamber 12 around axis 33. Thus, all of the substrate objects will be subjected to the same differences in density of the coating atmosphere which may exist laterally in the chamber 12 in the space in which the substrate objects are located.

Rotation of rotor 32 will also cause rotation of each of the substrate holders about its own axis 39. That is, by virtue of the cooperation between the gear teeth 41 on each holder with the pins 42 of bevel gear 43, movement of each holder about gear ring 43 by rotation of plate 32 will also cause the holder to rotate about its axis 39. Thus, all of the substrate objects will also be moved vertically of the coating chamber throughout the same space in such chamber. This will assure that all of the objects will be exposed to the same density differentials which may exist vertically in the chamber along their path of travel.

Upon rotation of each substrate holder 36 about its axis 37, each of the object supporting means thereon will be driven for rotation about its own axis. That is, in view of the planetary and chain arrangement by which each of the object supporting means is secured to the gear 59 which is stationary with respect to arm 34, as the holder 36 rotates with respect to arm 34, chain 58 will rotatably drive the gears 49 and, hence, the object supporting means and any substrate held thereby.

It is to be noted that because each of the arms 34 extends outwardly from rotor 32, i.e., that the substrate holders are held further apart at their lower extremities than at their upper portion, the axis 39 of rotation of each of the holders has a directional component which extends horizontally or laterally with respect to the chamber 12 and crucible source 16 even though the face 40 of each of such holders is in the line-of-sight of particles emanating. This results in the axis 39 being oblique to the direction of flow of particles from source 16. The axes 58 of the separate object supporting means are parallel to axis 39 and are therefore also oblique to source 16. The object supporting means grip the object to be supported in a manner holding the surface to be coated generally perpendicular to the rotational axis 58. Thus, the surface of the substrate object is also at an oblique angle with respect to the source 16. The result is that any irregularities in the form of ridges in the surface of the object, or depressions, which irregularities will be generally perpendicular to the surface of the object if it is a microelectronic wafer, will be angularly related to the path of coating particles flowing thereto from source 16. The rotation of the surface when it is in this orientation will assure that generally all surfaces formed by the ridges and indentations will be brought into direct line-of-sight alignment with such flow, thereby assuring deposition on such surfaces. It is to be noted that in order for the substrate surface to be coated to be oblique to the source, i.e., oblique to the direction of flow at the surface being coated of the particles emanating from the source, it may not be necessary that such surface be obliquely oriented in the envelope 13. That is, the orientation of the surface and its axis of rotation in the envelope will depend on the direction of flow of the material particles at the location of such surface.

As another feature of the instant invention, it is designed to facilitate ready access to the substrate objects secured thereto. That is, each of the arms 35 is simply and quickly separable from the rotor 32 by virtue of the hook and pin arrangement by which it is connected to such rotor. After the arm is so disconnected from the rotor, the full holder and the arm can be easily removed from the apparatus. In this connection, it will be noted from FIG. 3 that because a segment of plate 31 is removed, ready access can be had to any holder positioned for removal in line with such segment. Once a holder is removed from the apparatus, coated substrate objects held by the object supporting means can easily be disengaged therefrom and replaced by uncoated objects by merely depressing the plunger 54 of each object supporting means. For assembly line coating, one can provide a table or the like on which the holder can be rested with each of the plungers 54 in engagement therewith to simultaneously release for replacement all of the objects held by the object supporting means of the holder.

Claims

What we claim is:

1. Apparatus for providing complex motion to a plurality of substrate objects in order to assure uniform coating by deposition on a surface of each of such objects, said apparatus comprising a frame adapted to be supported within a coating chamber having a source of the desired coating material to provide an atmosphere in the chamber of particles of the coating material, a substrate holder having separate object supporting means rotatably mounted at discrete locations on a face thereof which is in line-of-sight of said source of material, said holder being mounted on said frame for orbiting about a first axis which is spaced from said holder and which extends generally toward said source and for rotation about a second axis which passes through said face of said holder, and means for orbiting and rotating said holder about said first and second axes respectively while simultaneously rotating each of said object supporting means on said holder face during the coating operation to rotate the surface to be coated of each object held thereby about an axis which is oblique to said source whereby substrate objects held by the object supporting means are rotated about three axes relative to said source during deposition thereon of the coating material.

2. The apparatus of claim 1 wherein said separate object supporting means are rotatably mounted on said face of said holder at positions equally spaced from the location at which said second axis passes through said face.

3. The apparatus of claim 1 wherein each of said object supporting means includes a plurality of spring fingers normally urged toward one another to grip therebetween a substrate object to be coated.

4. The apparatus of claim 1 wherein said substrate holder is selectively removable from said frame to facilitate access to said object supporting means thereon.

5. The apparatus of claim 1 wherein said means for orbiting and rotating said holder about said first and second axes respectively includes a prime mover coupled to said holder for rotatably driving said holder in an orbit about one of said first and second axes, and means linking said holder with said frame for rotating said holder about the other of said first and second axes upon the orbiting thereof about said one axis.

6. The apparatus of claim 5 wherein means are included coupling each of said object supporting means on said holder with said frame for rotatably driving each of said object supporting means upon rotation of said holder about said second axis.

7. The apparatus of claim 5 wherein said prime mover is drivingly coupled to said holder through a central rotor facing said source and mounted on said frame for coaxial rotation about said first axis, an arm extending outwardly from said rotor and toward said source, said holder being rotatably mounted on said arm for rotation on an axis generally perpendicular thereto to provide said rotation about said second axis, and wherein said means coupling each of said object supporting means with said frame includes a planetary gear arrangement linking each of said object supporting means with said arm whereby upon rotation of said holder about said second axis relative to said arm each of said object supporting means is rotatably driven on said face.

8. The apparatus of claim 7 wherein said substrate holder includes a gear cooperable with a corresponding gear on said frame to automatically provide rotation of said holder about said second axis upon the orbiting thereof by said rotor and arm about said first axis.

9. The apparatus of claim 5 wherein said arm is selectively separable from said rotor to enable removal of said substrate holder from the remainder of said frame for access to the object supporting means thereon.