U.S. patent number 3,643,625 [Application Number 04/864,377] was granted by the patent office on 1972-02-22 for thin-film deposition apparatus.
This patent grant is currently assigned to Carl Herrmann Associates, Inc.. Invention is credited to Gunard O. B. Mahl.
United States Patent |
3,643,625 |
Mahl |
February 22, 1972 |
THIN-FILM DEPOSITION APPARATUS
Abstract
A thin-film deposition apparatus having a holder and a plurality
of racks. Each of the racks has a surface which has the
conformation of a portion of the surface of a sphere. Means is
provided for rotatably mounting the racks on the holder in such a
manner that said surfaces of the racks lie generally on the surface
of a common sphere. Means is provided for rotating the holder upon
an axis centrally disposed with respect to the racks and for
rotating the racks about their own axes of rotation with respect to
the holder.
Inventors: |
Mahl; Gunard O. B. (San
Francisco, CA) |
Assignee: |
Carl Herrmann Associates, Inc.
(Menlo Park, CA)
|
Family
ID: |
25343138 |
Appl.
No.: |
04/864,377 |
Filed: |
October 7, 1969 |
Current U.S.
Class: |
118/725; 118/500;
118/730 |
Current CPC
Class: |
C23C
14/505 (20130101) |
Current International
Class: |
C23C
14/50 (20060101); C23c 011/02 () |
Field of
Search: |
;118/47-49.5,500,503
;204/298 ;117/106-107.2,93.2,93.1DH ;219/278 ;269/57 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kaplan; Morris
Claims
I claim:
1. In a thin-film deposition apparatus, a vacuum chamber, a
stationary support ring in said chamber, a holder in said chamber,
a plurality of circular racks in said chamber, each of said racks
having at least one surface having the conformation of a portion of
the outer surface of a sphere which can be generated within the
confines of said chamber, said surfaces of said racks lying
substantially on the outer surface of a common sphere, means in
said chamber for rotatably mounting said racks on said holder so
that the outer peripheral surfaces of said racks rest upon said
support ring and are adapted to travel on said support ring and so
that said one surface of each of said racks lies substantially on
the outer surface of said common sphere, and means for rotating
said holder about an axis centrally disposed with respect to said
racks so that said racks travel on said support ring whereby said
racks are orbited about an axis which is generally centrally
disposed with respect to said racks and are simultaneously rotated
about axes which are coincident with their respective axes of
rotation.
2. Apparatus as in claim 1 wherein said means for rotating said
holder includes a drive pin, said drive pin having a portion
thereof extending downwardly so that it is adapted to engage the
holder, and means for rotating said drive pin.
3. Apparatus as in claim 2 wherein said holder is provided with
three outwardly extending arms and wherein three of said racks are
provided and are mounted on the outer extremities of said arms, and
wherein said drive pin is adapted to engage one of said arms.
4. Apparatus as in claim 3 wherein a bearing retaining collar is
mounted on the outer ends of each of said arms and wherein said
means for rotatably mounting each of said racks includes a bearing
assembly mounted in said bearing retaining collar and means for
securing said racks to said bearings, said racks being removable
from said collars by lifting said bearing assemblies out of said
bearing collars.
5. Apparatus as in claim 4 wherein said holder and the racks are
constructed so that all of the weight of said holder rests upon
said racks.
6. Apparatus as in claim 1 wherein each of said racks is provided
with a plurality of openings, a spring clip mounted in each of said
racks adjacent to each of said openings and extending into the
opening, support members mounted on the racks adjacent to said
openings in the racks and positioned so that said spring clips are
adapted to yieldably engage said support members whereby substrates
may be placed between the same and held at angles with respect to
the surface of the racks.
7. Apparatus as in claim 1 together with the heater assembly
disposed below said support ring, said heater assembly including a
plurality of heaters and means for protecting the heaters from the
evaporation source.
8. Apparatus as in claim 7 together with an evaporation source
disposed so that it is generally in alignment with the axis of
rotation for the holder.
9. Apparatus as in claim 7 together with vertical support rods,
means for mounting said support ring upon said rods and means for
mounting said heater assembly on said support rods, said means for
protecting the heaters including a plate and wherein said means
mounting said heater assembly on said support rods includes a
plurality of collars slidably mounted on said support rods and
screws having eccentric heads mounted in said collars and adapted
to be rotated so that their heads frictionally engage the support
rods to hold the collars in predetermined positions on the support
rods.
10. In a thin-film deposition apparatus, a vacuum chamber, a holder
mounted in said chamber, a plurality of racks disposed in said
chamber, each of said racks having at least one surface having the
conformation of a portion of the outer surface of a sphere which
can be generated within the confines of said chamber, said surfaces
of said racks lying substantially on the outer surface of a common
sphere, means in said chamber rotatably mounting said racks on said
holder to permit rotation of each of said racks about its own axis
and for positioning said racks so that said racks are mounted in
such a manner that said one surface of each of said racks lies
substantially in the outer surface of said common sphere, and means
for causing rotation of said holder about an axis centrally
disposed with respect to said racks and to cause orbital movement
of said racks about said centrally disposed axis and also for
causing rotational movement of said racks about their own
individual axes of rotation while at all times maintaining said one
surface of each of said racks substantially in the outer surface of
said common sphere.
11. Apparatus as in claim 10 wherein said holder is provided with
three outwardly extending arms and wherein three of said racks are
provided with one of the racks mounted on each of said arms.
12. In a thin-film deposition apparatus, a vacuum chamber; a holder
mounted in said chamber; a plurality of racks disposed in said
chamber, each of said racks having at least one surface having the
conformation of a portion of the outer surface of a sphere which
can be generated within the confines of said chamber, said surfaces
of said racks lying substantially on the outer surface of a common
sphere; means in said chamber rotatably mounting said racks on said
holder to permit rotation of each of said racks about its own axis
and for positioning said racks so that said racks are mounted in
such a manner that said one surface of each of said racks lies
substantially in the outer surface of said common sphere; means for
causing rotation of said holder about an axis centrally disposed
with respect to said racks and to cause orbital movement of said
racks about said centrally disposed axis and also for causing
rotational movement of said racks about their own individual axes
of rotation while at all times maintaining said one surface of each
of said racks substantially in the outer surface of said common
sphere; and means for supporting a series of substrates to be
coated on each of said racks comprising a series of angularly
adjustable clamping members mounted on each of said racks at
predetermined locations, each of said clamping members projecting
from said one surface thereof, and a series of spring members
mounted on each of said racks in association with said clamping
members for holding substrates to be coated on said racks at
predetermined angles relative to the source of deposition material
so that uniform coating of said substrates may be insured.
13. The apparatus of claim 12 in which said racks are three in
number and are carried by said holder at equally spaced locations
relative to said centrally disposed axis.
Description
BACKGROUND OF THE INVENTION
In depositing thin films there is a need for obtaining a very
uniform deposition of coating materials on surfaces. This has been
particularly true with respect to parts which have irregular
surfaces such as parts with grooves, slots, steps and/or windows
therein and in which it is desirable to obtain a uniform deposition
of material in the slots. There is, therefore, need for a new and
improved thin-film deposition film apparatus.
SUMMARY OF THE INVENTION AND OBJECTS
The thin-film deposition apparatus consists of a holder and a
plurality of racks. Each rack has a surface which has a
conformation generally in the form of a portion of a surface of a
sphere. Means is also provided for rotatably mounting each of the
racks on the holder in such a manner that the surfaces of the racks
are disposed generally on the surface of a common sphere. Means is
provided for rotating the holder upon an axis centrally disposed
with respect to the racks so that the racks rotate about said
central axis. Means is also provided for rotating the racks about
their axes of rotation with respect to the holder during the time
the holder is being rotated.
In general, it is an object of the present invention to provide a
thin-film deposition apparatus in which it is possible to obtain a
very uniform deposition of the coating materials by utilization of
the principle of the cosine law distribution.
Another object of the invention is to provide apparatus of the
above character in which a relatively simple and unique double
rotation system is utilized.
Another object of the invention is to provide apparatus of the
above character in which it is possible to achieve a relatively
uniform coating in any grooves, slots or other depressions in the
substrates.
Another object of the invention is to provide apparatus of the
above character in which the racks can be readily removed for
loading and unloading.
Another object of the invention is to provide apparatus of the
above character in which very simple means is provided for rotating
the racks.
Another object of the invention is to provide apparatus of the
above character in which the racks are mounted on a spider assembly
which can be removed as a unitary assembly.
Additional objects and features of the invention will appear from
the following description in which the preferred embodiment is set
forth in detail in conjunction with the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a side elevational view with certain portions broken away
of a thin-film apparatus incorporating the present invention.
FIG. 2 is an enlarged side elevational view of the deposition
apparatus shown in FIG. 1 with the cage and bell jar removed.
FIG. 3 is a still further enlarged side elevational view of a
portion of the deposition apparatus shown in FIG. 2.
FIG. 4 is a top plan view looking along the line 3--3 of FIG.
2.
FIG. 5 is a cross-sectional view looking along the line 5--5 of
FIG. 2.
FIG. 6 is a cross-sectional view taken along the line 6--6 of FIG.
5.
FIG. 7 is an enlarged detail view of a portion of the apparatus
shown in FIG. 5.
FIG. 8 is an enlarged detail view of the clips utilized in
conjunction with the racks in the thin-film deposition
apparatus.
FIG. 9 is a cross-sectional view taken along the line 9--9 of FIG.
8.
BRIEF DESCRIPTION OF PREFERRED EMBODIMENT
The thin-film deposition apparatus consists of a base plate 11 upon
which are mounted a plurality of vertical upstanding support rods
12. The source 13 is of a conventional type and is mounted upon the
base plate 11 so that it is centrally disposed on the base plate
11. The source 13 is provided with means for evaporating material
placed in the source 13 for deposition on substrates as hereinafter
described. A shutter 14 is carried by a rod 16 which is rotatably
mounted in a support member 17 carried by one of the support rods
12. A knob 18 is mounted on the rod and is adapted to move the
shutter 14 into position in which it overlies the source 13 or into
a position in which it is away from the source 13.
A cooling coil assembly 21 of a conventional type is mounted upon
the base plate 11 and encircles the source 13 as shown particularly
in FIG. 2. A heater assembly 22 is mounted adjacent to the upper
extremity of the cooling assembly 21 and is carried by the support
rods 12 in a manner hereinafter described.
Means is provided for carrying the substrates which are to be
coated in the apparatus and includes a stationary support ring 24
which is mounted upon the upper ends of the support rods or posts
12. The support ring 24 is provided with four pins 26 which are
secured to the bottom of the support ring 24 by suitable means such
as welding. The pins 26 extend into holes 27 provided in upper ends
of the support rods 12 and are retained therein by set screws 28.
The support ring 24 is provided with a large opening 31 which has
inwardly and downwardly inclined annular wall 32. In addition, the
ring 24 is provided with annular recesses 33 and 34 of differing
diameters as shown particularly in FIG. 3. The recesses 33 and 34
are generally in the form of right angles in cross section as shown
particularly in FIG. 3. The inner recess or groove 33 serves as a
track as hereinafter described, whereas the second larger recess 34
serves as a catch or retainer. The support ring 24 is provided with
an outwardly facing annular slot 36 which is covered by a strip 37
which is welded thereto so that a fluid passage is formed for
cooling water.
The means for carrying the substrates in the apparatus also
includes a holder or spider 38 which is provided with a central hub
39 and three downwardly and outwardly curved arms 41 spaced
120.degree. apart which are secured to the central hub and extend
radially therefrom. A plurality of racks 43, namely three, are
carried by the holder. As can be seen from the drawings, the racks
43 are circular and have at least one surface which has a
conformation that corresponds to a portion of the surface of a
sphere. In the arrangement shown in the drawings, the three racks
43 are in fact in such a form that they can be considered to be
three spherical sections of a large common sphere.
Means is provided for rotating and mounting the racks 43 on the
ends of the arms 41 in such a manner that when the outer
peripheries of the racks 43 are within the track formed by the
recess 33, they will travel in the surface of a sphere as they are
rotated or orbited as hereinafter described. Each of the arms 41
carries a split bearing retaining collar 46 which has slidably
mounted therein ball bearing assemblies 47. A post 48 is mounted on
each of the racks 43 and is mounted in the roller bearing
assemblies 47 and is retained therein by a retaining clip 49. Each
rack 43 with its bearing assembly 47 can be readily slipped
downwardly and outwardly out of the collar 46 to facilitate loading
of the rack. The collar 46 is provided with an inwardly extending
lip 46a to retain the bearing assembly 47 so that the bearing
assembly can only be removed in one direction. A small annular
shield 50 is provided on each of the posts 48 to protect the
bearing assemblies 47 from the vapor stream.
The bearing support collars 46 are stabilized by means of a
stabilizing ring 51 which extends between the same and is secured
thereto by suitable means such as welding.
Each of the racks 43 is provided with a plurality of circular
openings 53 which are spaced relatively uniformly over the surface
of the rack. The openings 53 are generally of the size of the
substrates which are to be coated to facilitate loading of the
substrates in the rack. A spring clip 54 is provided for holding
the substrate in the desired position on the rack. The spring clips
54 are formed of a suitable material such as Inconel which has been
heat treated so it can withstand the high-temperature conditions
encountered during deposition. The spring clip 54, generally
U-shaped as shown in FIG. 8, is provided with a pair of spaced end
portions 54a which extend through and are secured to the rack
adjacent to one of the openings 53. The spring clip is provided
with a downwardly depending portion 54b which is yieldably urged
into engagement with a clamping member 56 which is secured to the
rack 43 at a point adjacent to the other side of the opening 53.
The clamping member 56 is provided with a support surface 57 which
extends away from the inner curved surface of the rack 43. Thus,
there is shown a substrate 58 of a suitable type such as silicon
wafer which has one edge of the same clamped between the support
surface 57 and the spring clip 54. The clip 54 can hold wafers of
various sizes and can even hold pieces of wafers. By bending the
clamping member 56, it is possible to hold the wafer or substrate
at different angles to thereby change the angle of incidence of the
vapor stream to the wafer or substrate.
Means is provided for causing rotation of the holder or spider 38
so that it will be rotated about an axis which is centrally
disposed with respect to the racks 43. Such means consists of a
Z-shaped drive pin 61 which has its lower end free but which is
adapted to engage one of the arms 41 as shown particularly in FIG.
3. The other end of the drive pin 61 is mounted in a drive member
62. The drive member 62 is rotatably mounted in a pair of ball
bearing assemblies 63 and is provided with a central opening 65 to
permit direct source monitoring with suitable monitoring equipment.
The ball bearing assemblies 63 are carried by a support collar 64
mounted upon the end of a gusset 66. The gusset 66 is mounted upon
a drive support member 67 which is secured to one side of the
support ring 24 by suitable means such as welding. The ball bearing
assemblies 63 are retained within the collar 64 by a retaining clip
68. A sprocket 69 is formed integral with the upper end of the
drive member 62. The sprocket 69 is driven by a chain 72 and the
chain 72 is driven by a sprocket 73. An eccentrically mounted idler
sprocket 74 is rotatably mounted upon the pin 76 and mounted in a
boss 77 carried by cross member 78 mounted upon the gusset 66.
The sprocket 73 is secured to a drive shaft 81 by a set screw 82.
The drive shaft 81 is rotatably mounted in ball bearing assemblies
83 mounted in the upper and lower ends of the drive support member
67 and retained therein by retaining rings 84. A sprocket 86 is
mounted on the lower end of the drive shaft 81 and is secured
thereto by a set screw 87. The sprocket 86 is driven by a chain 88
and the chain 88 is driven by a sprocket 89. The sprocket 89 is
secured by a set screw 91 to another drive shaft 92. The upper end
of the drive shaft 92 is mounted in a ball bearing assembly 93
mounted within a collar 94 secured to the support ring 24. The
lower end of the shaft 92 is connected by a coupling 96 to another
drive shaft 97. The shaft 97 extends through a sealed bearing
assembly 98 of a conventional type which is mounted in the base
plate 11. A rough vacuum can be applied to the sealed bearing
assembly 98 through a connector 99. Another coupling 101 (see FIG.
2) is adapted to be connected to the output shaft 102 of a gear
motor (not shown) so that the shaft 97 is driven at a speed ranging
from 0 to 20 r.p.m.
The heater assembly 22 which is provided consists of a circular
plate 106 which is carried by the support rods 12 at a point which
is below the support ring 24. Four quartz heaters 107 are mounted
upon the upper surface of the plate 106 so that the plate 106
protects the heaters from the evaporation source. The heaters 107
are mounted in brackets 108 carried by the plate 106. Reflectors
109 are mounted on the plate 106 and underlie the heaters 107.
The plate 106 rests upon collars 111 (see FIG. 7). Cap screws 112
with eccentric heads are mounted within the collars 111 and by
rotation of a quarter turn are adapted to lock the collar in a
predetermined vertical position on the support rod. It has been
found that these screws 112 are far superior to set screws because
they do not mar the support rods 12 which permits the collars 111
to be readily adjusted vertically of the support rods.
The thin-film deposition apparatus also includes additional
conventional parts as, for example, a glass bell jar 116 and a
protective cage 117 (see FIG. 1). Such apparatus also includes
means for supplying a vacuum to the bell jar. However, since such
means is conventional, they will not be disclosed in detail.
Operation of the thin-film deposition apparatus may now be briefly
described as follows. Let it be assumed that the cage 117 and the
bell jar 116 have been removed. When this has been accomplished,
the holder or spider 38 with the racks 43 mounted thereon can be
lifted as a subassembly from the support ring 24. This is possible
because there is no direct solid connection between the spider and
the drive pin 61. Since the racks and holder can be readily
removed, it is very easy to load the substrates into the racks. Let
it be assumed that substrates such as silicon wafers are mounted on
the racks by use of the spring clips to assume positions such as
that shown in FIG. 9.
After the three racks have been loaded, the entire subassembly can
then be positioned upon the support ring 24 with the outer lower
extremities of the racks engaging the grooved recess 33 and with
the weight of the holder 38 upon the racks 43. The bell jar 116 and
the cage 117 can be replaced and the apparatus can be pumped down.
Thereafter, the heater assembly can be operated if desired to bake
out the silicon wafers. During this time the substrates which are
to be coated are rotated. This is accomplished by energizing the
drive motor which is connected to the coupling 101 which causes
rotation of the shaft 81 and the drive member 62. Rotation of the
drive member 62 causes rotation of the drive pin 61. The drive pin
61 engages the spider or holder 38 and causes it to rotate on the
axis of rotation for the holder or spider which is centrally
disposed between the racks 43. At the same time that this rotation
is occurring, the racks are rotated about their own axes of
rotation because their lower extremities frictionally engage the
support ring 24 which causes the same to be rotated. Thus, it can
be seen that the drive system is such that a double rotation is
simultaneously provided for the substrates. The first rotation or
orbital movement is rotation about the central axis for the spider
or holder 38 and the second or other rotation is about the axis of
rotation which is coincident with the axis of rotation for the
rack. The spider assembly rotation and the rack rotation are
stabilized by the use of the double bearings.
After the bake-out has been completed, the double rotation of the
racks with the substrates carried thereby can be continued.
Thereafter, the source can be energized to evaporate material to
cause coatings to be deposited upon the substrates carried by the
racks. The double rotation which is provided for the substrates in
the manner hereinbefore described facilitates obtaining a much more
uniform distribution of the coating material on the exposed
surfaces of all of the substrates. In addition, it will be noted
that since the substrates are placed at an angle with respect to
the spherical surface of the racks, the substrates will be
presented at different angles to the evaporation source. This
change of angle of the substrates is particularly desirable when it
is desired to deposit the evaporated material into grooves or slots
carried by the substrates. In other words, this apparatus makes it
possible to obtain a more uniform distribution of the coating over
the entire exposed surface of the substrate and, in addition, makes
it possible to obtain a more uniform distribution of the coating
material in the windows or slots in the substrate. As pointed out
previously, the angle of the chips relative to the rack can be
adjusted by bending the retaining members 56 to different
angles.
It is apparent from the foregoing that there has been provided a
thin-film deposition apparatus which has many advantages. Because
of the construction of the holder and the rack mounting upon the
holder, the entire subassembly can be removed to facilitate ready
loading and unloading of substrates. In addition, the substrates
are rotated about two axes of rotation to obtain much greater
uniformity in the coating of the material on the substrates. Also,
the substrates are carried at an angle with respect to the surface
of the common sphere in which the racks rotate so that the
substrates may be presented at continuously varying angles to the
source to facilitate a more uniform distribution of the coating in
slots or openings provided on the substrates.
* * * * *