Magnetron cathode sputtering method and apparatus

A magnetron sputtering cathode assembly provides an annular target of sputtering material located with a sputtering surface facing a substrate to be sputtered. An inner magnet and an outer ring magnet are positioned adjacent inner and outer edges of the sputtering surface. The outer ring magnet is oriented so that its North-to-South magnetic orientation is substantially parallel to the plane defined by the sputtering surface while the inner magnet is oriented so that its North-to-South magnetic orientation is substantially perpendicular to the plane defined by the sputtering surface. A pair of walls extend at the inner and outer edges of the annular target away from the sputtering surface and toward the substrate. The walls and the magnets define a closed-loop array of radial magnetic lines having improved target erosion and plasma-containing characteristics.

FIELD OF THE INVENTION 
This invention relates to a method and apparatus for sputtering a target 
material onto a substrate and more particularly to a magnetron sputtering 
cathode apparatus having an improved sputtering target and magnet assembly 
that provides more efficient utilization of the target. 
BACKGROUND OF THE INVENTION 
Magnetically-enhanced cathode sputtering devices have been used extensively 
to deposit a thin layer of a target material on a substrate. One common 
application for such devices is in the manufacture of compact discs (CDs) 
having a thin layer of aluminum target material along a surface of the 
polycarbonate substrate disc. Typically, the substrate is located in the 
presence of a vacuum (10.sup.-3 Torr) and a small concentration of Argon 
gas is introduced. The target is energized with a cathode voltage which 
ionizes the argon and generates a plasma. The target material is atomized 
by the plasma and is "sputtered" toward the disc, which is adjacent a 
grounded anode. A basic design for a magnetron sputtering device is 
disclosed in U.S. Pat. No. 4,166,018. Various improvements on this basic 
concept have also occurred. 
FIG. 1 schematically illustrates a magnetron sputtering device according to 
the prior art. The device 20 comprises a magnet assembly 22 located 
adjacent a target 24 along a back surface of the target 26 opposite a 
substrate 28 to be coated. The magnet assembly 22, according to this 
example, comprises permanent magnets mounted on a plate of 
magnetically-permeable material 32. A pair of outer magnet rows 30 
surround an inner magnet row 34. The outer rows 30 are generally joined 
together at their ends by curved sections (not shown) of magnetic material 
to form a closed loop around the inner row 34. The outer rows 30 are 
oriented so that their north poles (N) are adjacent the back surface 26 of 
the target 24. Similarly, the inner or center row 34 is oriented so that 
its south pole (S) is most closely adjacent the target's back surface 26. 
The north-to-south axis of each magnet is, likewise, aligned substantially 
perpendicularly to the back surface 26 of the target 24. 
The location of the magnet rows 30 and 34 and the orientation of their 
poles N and S generate a magnetic field defined by a series of magnetic 
flux lines 36 that penetrate the target 24 and that form a closed loop, 
tunnel-like, arched section 38 over the front or "sputtering" surface 40 
of the target. The midsection 42 of the arch 36 is approximately adjacent 
the sputtering surface 40 and defines flux lines that are substantially 
parallel to the plane of the sputtering surface 40. 
The flat arched section 42 confines the charged plasma in close proximity 
to the sputtering surface 40. This confinement facilitates the sputtering 
or projection of material onto a desired portion of the substrate 28. 
Similarly, the arched section 38 of the magnetic field prevents spreading 
of the plasma along the target's sputtering surface 40 and maintains the 
plasma laterally within the area of the arch. Thus, the transfer of 
sputtered material occurs within a well-defined region of the substrate 28 
based upon the shape of the arch. 
A disadvantage of sputtering according to FIG. 1 is that the sides 46, 48, 
50 and 52 of the magnetic field arch 36 concentrate erosion of sputtering 
target 24 toward the center of the arch 38 and result in the formation of 
erosion trenches 54 and 56 in the target that define an approximately 
V-shaped cross section. Hence, a large portion of target material adjacent 
the target's center and outer ends remains unused. The uneven erosion 
necessitates replacement of targets at shorter time intervals than if more 
of the target were actually sputtered. 
The use of thicker targets in the process of FIG. 1 is not generally 
effective. The thickness of the target is limited by the strength of the 
magnets. The arch 38 becomes too distant from the magnets and thus the 
field becomes too weak to properly contain the plasma. 
An alternate configuration for a magnetron sputtering apparatus is 
disclosed in U.S. Pat. No. 4,486,287. This configuration is shown 
generally in FIG. 2 and can be used for coating of circular CD surfaces. 
The magnet assembly 51 comprises a pair of concentric inner and outer 
annular magnets 55 and 57, respectively, centered about an axis 59. The 
magnets are aligned so that their north and south poles, N and S, 
respectively, are oriented along an alignment that is parallel to the 
plane of the target 60 and the plane of the substrate 61. 
The target 60 in this example comprises an annular ring of sputtering 
material having a sputtering surface 62 located adjacent the inner and 
outer magnets 55 and 57. The magnets 55 and 57 generate a magnetic field 
defining a plurality of substantially parallel flux lines 64 that are 
located in front of and behind the sputtering surface of the target 60. 
The target 60 also includes a pair of concentric confining walls 66 and 68 
at the inner and outer edges of the target that enable plasma generated 
from the sputtering surface 62 to be confined within the area of the flux 
lines 64 directly adjacent the sputtering surface 62. 
The configuration of FIG. 2 enables efficient utilization of the target and 
facilitates sputtering over the entire target sputtering surface 62. This 
configuration also enables the use of thicker targets for prolonged 
sputtering without target replacement. However, orientation of the inner 
magnet 55 poles N and S parallel to the substrate plane necessitates a 
relatively large diameter for the inner magnet assembly. The enlarged 
diameter of the inner magnet reduces the area of the substrate center that 
can be sputtered effectively. Thus, the magnet configuration of FIG. 2 is 
sometimes unacceptable when an area close to the center of the substrate 
61 must be sputtered. 
In view of the disadvantages of the prior art, it is an object of this 
invention to provide a magnetron sputtering cathode assembly having an 
increased target life with an improved target erosion pattern. The cathode 
assembly should be able to accept relatively thick targets and should 
enable long term use without target replacement or readjustment. The 
cathode should be able to sputter magnetic materials and nonmagnetic 
materials and should enable sputtering of a large area of the substrate. 
SUMMARY OF THE INVENTION 
A magnetron sputtering cathode assembly according to this invention 
provides a housing that is generally attached to a vacuum chamber. The end 
of the housing includes an opening typically adapted to receive a 
substrate which, according to a preferred embodiment, comprises a 
conventional compact disc (CD). A target constructed, in one embodiment, 
from 6061 aluminum alloy, is located in a face-to-face relationship with 
the substrate spaced at a predetermined distance from the substrate. The 
target defines an annulus having inner and outer edges that are generally 
circular. The inner edge defines an open center section within which is 
positioned a magnet assembly according to this invention. The outer edge 
is adjacent a ring magnet. The target includes a sputtering surface that 
faces the substrate and that defines a plane. A pair of walls extending 
from the plane in a direction toward the substrate along each of the inner 
and outer edges. 
The magnets are polarized so that the North-to-South orientation of the 
inner magnet poles is aligned perpendicularly relative to the plane of the 
sputtering surface. The North-to-South orientation of the outer magnet 
poles is aligned parallel relative to the plane of sputtering surface. 
Both the inner magnet and the outer magnet are positioned so that they are 
adjacent the plane of the sputtering surface aside each of the inner and 
outer edges of the target. The magnets are each mounted to a 
magnetically-permeable material base. The inner and outer magnets define a 
magnetic closed-loop array of radial flux lines in close proximity to the 
sputtering surface. The flux lines defined by the magnetic field pass 
through the walls of the target. The flux lines defined by the field are 
substantially flat adjacent the sputtering surface. 
When the target is energized, a plasma of ionized Argon gas is generated 
above the target. The plasma is contained with the magnetic field. The 
geometry of the field serves to maintain an even erosion of sputtering 
material from the target and the walls of the target prevent undue spread 
of the plasma outside the edges of the target. This even erosion extends 
the life of the target and improves efficiency of the sputtering 
operation. 
According to a preferred embodiment, the target includes lugs that 
interengage respective retaining lugs within the housing. There are gaps 
between the housing lugs and the target lugs that enable the target to be 
passed axially into and out of the housing upon rotation to a 
predetermined rotational position. Likewise, rotation to another 
rotational position causes the housing lugs to overlie the target lugs to 
prevent axial movement of the target out of the housing. A plurality of 
eccentric bolts are provided for axially moving the retaining lugs toward 
and away from the lugs of the target. Thus, a positive locking of the 
target can occur. The housing also includes various cooling channels 
through which cooling fluid flows to counteract the effects of the high 
temperature plasma generated by energizing of the target.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
A magnet and target configuration for a magnetron cathode sputtering 
apparatus according to a preferred embodiment of this invention is 
detailed in FIG. 3. The magnet assembly 70, shown schematically, is 
adapted for applying material to a circular substrate 72 that can comprise 
a conventional compact disc (CD) according to this embodiment. The 
circular substrate 72 has a central axis 74 that is aligned with the 
center of the magnet assembly 70. It is contemplated, however, that the 
structure shown and described herein can be ovular, rather than circular, 
for sputtering a variety of substrate shapes. 
As depicted, the magnet assembly 70 comprises an outer ring magnet 76 and 
inner cylindrical magnet 78 located coaxially about the center axis 74. 
The magnet assembly 70 includes outer and inner permanent magnets 78, 76, 
respectively, having North-to-South magnetic orientations aligned 
perpendicularly to one another. The outer ring magnet 76 includes a 
North-to-South pole (N-S) orientation that is aligned parallel to the 
plane defined by the substrate 72. It is generally contemplated that the 
outer magnet define a closed-loop of magnetic material regardless of 
perimeter shape to maintain electron drift around the structure. 
Conversely, the inner magnet 78 includes a North-to-South pole (N-S) 
orientation aligned perpendicularly to the plane defined by the substrate 
72 and generally parallel with the axis 74. The inner magnet 78 and outer 
magnet 76 are each mounted to a base 79 constructed from a 
magnetically-permeable material such as steel. 
The target 80 comprises an approximately-rectangular cross section annulus, 
according to this embodiment. It includes a front or sputtering surface 82 
defining a plane that is approximately parallel with the front surface 84 
of the inner magnet 78. The outer ring magnet 76 is aligned so that its 
inner side 86 is transected by the plane defined by the target sputtering 
surface 82. In general, the magnets of this embodiment are located "aside" 
the edges of the target rather than "behind" the target as exemplified by 
FIG. 1. 
The orientation of the poles of the outer and inner magnets 76 and 78, 
respectively, generates a magnetic field therebetween, defined by flux 
lines 88, that passes through the target cross section and is 
approximately flat adjacent the sputtering surface 82 of the target 80. 
Note that the sputtering surface of this embodiment is planar. Such 
surfaces typically define a plane upon initiation of sputtering. For the 
purposes of this discussion, it shall be assumed that the sputtering 
surface shall approximately define a plane. Other directions shall be 
taken with reference to this plane. However, where the sputtering surface 
shall be nonplanar, the term plane shall refer to a plane passing through 
a forward face of the sputtering surface and approximately perpendicular 
with a direction in which sputtered target material is meant to travel. 
The flux lines, forwardly of the sputtering surface 82 of the target 80 
(and below the substrate deposition surface 90) define an arch over the 
target sputtering surface 82. The flux lines 88 within the target, 
likewise, define an arch that projects into the target in a direction away 
from the sputtering surface 82. 
The target according to this embodiment includes a pair of inner and outer 
raised walls 92 and 94, respectively, through which the magnetic field 
flux lines 88 pass. When a sufficient voltage (approximately 600 VDC) is 
applied to the target 80, a plasma is generated adjacent the sputtering 
surface 82. The plasma is contained within the area of the target by the 
flux lines 88 and the walls 92 and 94. Ejected atoms of target material 
passes through the plasma along paths defined generally by arrows A onto 
the surface 90 of the substrate 72, causing the surface to be coated with 
the target material. 
A relatively flat magnetic field flux line is defined adjacent the 
sputtering surface 82 in a preferred embodiment. However, the positioning 
of the flux lines of the magnetic field according to this embodiment can 
be utilized to alter the area of erosion of the target. For example, by 
moving the outer magnet 76 further toward the substrate 72, the erosion 
pattern can be moved toward the outside of the target. Since a larger 
volume of target material is located radially outwardly on the target 72, 
axial relocation of the ring magnet 76 can enable more efficient 
utilization of the target. Additionally, by varying the intensity of the 
outer magnet 76, similar variations in erosion pattern can be obtained. 
The relative locations of the magnets 76 and 78 and their intensities 
(described further below) can, thus, be varied to obtain an optimum 
erosion pattern for a given target shape, size and materials. The 
parameters according to this embodiment are, therefore, preferred 
primarily for the target described and depicted. 
A magnetron sputtering cathode assembly utilizing the magnet configuration, 
substantially of the type detailed in FIG. 3, according to a preferred 
embodiment, is shown in greater detail in FIGS. 4 and 5. The cathode 
assembly 100 is interconnected with a vacuum chamber 101 at an opening 103 
in the chamber 101. As discussed above, a vacuum of 10.sup.-3 Torr is 
maintained and Argon gas is present in the chamber according to this 
embodiment. 
The cathode assembly 100 includes a feed cable 102 that carries cooling 
water and power, a cathode cover 104 that encloses the power and cooling 
water feed connections and a sputtering assembly 106 that houses the 
target 150 and receives substrate elements (conventional compact discs in 
this example) at a frontmost end 108. It is contemplated that the front 
end 108 is mounted in a vacuum chamber (not shown) to facilitate the 
migration of sputtering material onto the surface of the substrate 110. 
The substrate 110 is typically brought into contact with the front end 108 
by a cup-like structure of conventional design (also not shown) that 
transfers substrates 108 to and from conventional storage magazines. 
The substrate 110 is supported relative to the sputtering assembly 106 on a 
generally cylindrical outer mask 112 and a generally cylindrical inner 
mask 114. The outer mask 112 is constructed from stainless steel according 
to a preferred embodiment. The inner mask 114 is constructed from copper. 
Other materials having suitable resistance to a high temperature plasma 
can be substituted for the masks. The inner mask 114 and outer mask 112 
prevent migration of target material onto the inner and outer areas of the 
substrate, ensuring a smooth transition between coated and uncoated 
substrate areas. For example, a compact disc is uncoated at its center and 
outer edge. The masks 112 and 114 facilitate such a pattern by blocking 
the migration of excess target material. The masks must occasionally be 
cleaned to remove any excess. 
To prevent mask or substrate damage, the outer mask 112 and the inner mask 
114 each receive circulated cooling fluid to counteract the extreme 
temperatures generated by the sputtering process. Water or another 
suitable coolant, such as ethylene glycol, can be utilized according to 
this embodiment. The outer mask 112 is cooled by cooling water from an 
inlet 115. The water is routed through a channel 120 in the outer mask 112 
that surrounds the perimeter of the outer mask. Water exits through an 
opposing outlet 117. The inlet 115 and outlet 117 are engaged to the mask 
112 with quick-disconnect water fittings 123 and 261. The mask 112 is 
sealed to the water fittings 123 and 261 by O-rings 119 and 121, 
respectively. These fittings 123 and 261 are biased toward the mask 112 by 
springs 125 and 260, respectively. Likewise, the mask 112 is sealed 
against the vacuum chamber walls 127 with an O-ring 129. 
Similarly, the inner mask 114 receives cooling water from a central cooling 
assembly 124 (FIG. 5). Water passes along the central axis through a 
central cooling channel 125 and returns through a coaxial channel that 
communicates with cooling outlet assembly 126 (FIG. 5). As depicted 
generally in FIG. 4, the inner magnet 160 defines a hollow center that 
houses the coaxial cooling channel 164. Water passes from the center 
channel to the outer channel 165 at the front end 131 of the channel. The 
outer cooling channel 165 is joined with a T-connector 135 that enables 
cooling water to exit the outer cooling channel 165. 
The O-ring 130 forms a seal between the sputtering assembly base plate 131 
and the lower rim 133 of the outer mask 112. This ring enables a vacuum to 
be maintained within the interior of the outer mask 112 and the vacuum 
chamber 101 to which it is connected. 
The O-rings 134 and 136 are located at the rear side of the sputtering 
target 150 according to this invention. The cooling water from inlet 
assembly 116 is channeled into the cavity 152 behind the target 150 and 
provides cooling to the target 150 during plasma generation. Water 
circulates around the base of the target and exits through the cooling 
outlet 122. The inlet 116 and outlet 122 are each provided as take-offs 
that project through the sputtering assembly base 131 (See also FIG. 5) 
These take-offs are insulated from the base plate by an insulating grommet 
(137 for inlet 116). 
The base plate 131 is part of an overall machined steel outer shell or 
housing 140. The elements of the sputtering assembly 106 are mounted on 
the housing 140. As described further below, the housing 140 is 
constructed from a magnetically permeable material (steel). It is in 
direct contact with the magnets (160, 162) of this embodiment and forms a 
bridge between them. 
The target 150 is electrically isolated from the housing 140. The housing, 
conversely, forms part of the grounded anode with the vacuum chamber 
according to this embodiment. An insulator 153 is located on the base 
plate 131. It insulates the grounded base plate from a target base 240. 
The target base 240 is constructed in the form of a ring from conductive 
material such as steel. The target base 240 includes stems (147 for inlet 
116) that project through the base 240 and outwardly from the base plate 
131. The stems 147 define open passageways to allow coolant to pass 
through the thickness of the base 240 so that coolant can communicate with 
the rear of the target 150. The stems 147 enable attachment of the inlet 
116 and outlet 122 take-offs using a pressure fitting 149 or similar 
coupling device. 
The target base 240 is also interconnected with a power take-off 142 (FIG. 
5) that passes through the base plate 131 and contacts the target base 240 
along the rear side of the base 240. The power take-off 142 is insulated 
from the base plate 131 by a grommet-shaped insulator similar to the 
insulator 137 provided to the take-off hole of the cooling inlet 116. The 
insulators used according to this embodiment can be constructed from any 
appropriate insulating material such as Delrin.RTM., Teflon.RTM., 
fiberglass, rubber or other insulating compounds. Note that the target 
base 240 is also sealed relative to each of the take-off holes in the base 
plate 131 by an O-ring (such as O-ring 157 for inlet 116) to prevent air 
infiltration through any take-off hole. 
The target base 240 is electrically interconnected with the target 150 by a 
set of target retaining or mounting rings 144 and 146. These rings engage 
the inner and outer perimeters of the target and are described further 
below. 
The target 150 is energized with approximately 600 volts DC during 
sputtering. In the presence of an Argon-filled vacuum chamber, this 
cathode voltage is sufficient to generate a plasma according to this 
embodiment. 
The outer shell 140 also supports the inner magnet 160 and the outer magnet 
162 according to this invention. The inner magnet 160 comprises cylinder 
having an outer diameter of approximately 1.4 inches, an inner diameter of 
approximately 0.50 inch (for coolant passage) and a length of 
approximately 2.12 inches. The magnet 160, according to this invention, 
can be formed preferably from a Neodymium-Iron-Boron material available, 
for example, from the Cookson Magnet Company, having stock numbers 35, 
35H, 37, 39H, 40, 42H or 45 and a B constant of between 12,300 and 13,500 
gauss. 
The outer ring magnet 162, according to this embodiment, is constructed 
from a plurality of flexible magnetic strips that are assembled together 
on a cylindrical form to create the large laminated ring magnet shown in 
FIG. 4. The strips are available from the Electrodyne Company under the 
trademark Reance 90. Each strip is 0.030 inch thick and 0.5 inch in width, 
the strips having B.sub.r constant of approximately 6,500 gauss. The 
completed outer magnet 162 is approximately 0.625 in cross sectional width 
and has a maximum outer diameter of approximately 8.75 inches and a height 
of approximately 0.5 inch. When mounted in the housing 140, the outer ring 
magnet 162 is provided with a magnet shield 180 in the shape of a ring 
that covers the ring magnet where it faces the outer mask 112. 
As discussed generally with reference to FIG. 3 and magnets 78 and 76, 
respectively, the inner magnet 160 and outer magnet 162 are oriented so 
that the inner magnet is polarized substantially perpendicular to the 
plane of the substrate 110 and the plane of the target sputtering surface 
170. The outer magnet 162 is polarized substantially parallel to the plane 
of the substrate 110 and sputtering surface 170. Hence, the magnets 160 
and 162 generate a magnetic field having flux lines as defined generally 
in FIG. 3 with a relatively parallel flux line passing across the 
sputtering surface 170 of the target 150. The use of such a field 
facilitates relatively even erosion of the target 150 across its entire 
surface enabling longer target life and, hence, less idle time due to 
target replacement. 
To contain the plasma generated above the sputtering surface 170, the 
target 150 includes a pair of raised walls 172 and 174 (see also FIG. 7) 
through which flux lines of the magnetic field pass. The walls 172, 174, 
according to this embodiment, are spaced from each other at a radial 
distance of approximately 2 inches. The walls 172 and 174 are 
approximately 3/16 inch thick and are approximately 0.25 inch in height 
from the sputtering surface 170. The walls 172 and 174 and other target 
structures can be formed, according to this embodiment, by machining a 
solid billet of 6061 aluminum alloy. 
The orientation of magnetic fields according to this invention extends the 
life of the target and reduces idle time between target replacement. Idle 
time is further reduced by an improved retaining mechanism that enables 
rapid target attachment and detachment according to this invention. With 
further reference to FIGS. 6-13 the target 150 (FIGS. 6 and 7) includes 
inner lugs 190 and outer lugs 192 that radially project from the 
respective recessed rims 197 and 199 on the rear side 198 of the target 
150. Four inner lugs 190 and four outer lugs 192 are provided on the rims. 
The lugs 190 and 192 have a height of approximately 0.12 inch. They 
radially extend approximately 0.125 inch from their respective recessed 
rims 197 and 199. The recessed rims 197 and 199 are radially recessed 
approximately 0.25 inch from the inner edge 201 and the outer edge 203, 
respectively, of the target 150. The lugs 190, 192 span an arc P which, 
according to this embodiment, is approximately 45.degree.. The lugs 190 
and 192 are centered at 90.degree. angles relative to each other. However, 
it is contemplated that a larger or smaller number of lugs can be utilized 
according to this invention and that the lugs can be spaced at a variety 
of circumferential locations relative to each other. 
The outer retaining ring or base 146 (FIGS. 8 and 9) includes corresponding 
lugs 200 that face radially inwardly and are constructed to interengage 
with the outer lugs 192 of the target 150. The retaining ring lugs 200 are 
also located at 90.degree. intervals about the ring 146. The lugs 200, 
similarly, encompass an arc P of 45.degree.. The lugs 200 are sized and 
shaped similarly to the target's outer lugs 192. The target 150 can pass 
axially with its outer lugs 192 positioned between the retaining ring lugs 
200 in the corresponding retaining ring spaces 202, because spaces 202 
also trace a 45.degree. arc. Thus, the spaces 202 are sized to accommodate 
the outer lugs 192 of the target 150. Similarly, the inner retaining ring 
or base 144 (FIGS. 10 and 11) also includes a set of four lugs 208 that 
project radially outwardly and are spaced at 90.degree. intervals about 
the circumference of the inner retaining ring 144. These lugs each trace 
an arc P of 45.degree. about the ring's circumference and are aligned with 
the lugs 200 of the outer ring. Thus, the inner lugs 190 of the target can 
pass axially between the inner ring lugs 208 at the same time that the 
outer target lugs 192 pass between the outer ring lugs 200. Accordingly, 
the orientation of the inner and outer retaining rings 144 and 146, 
respectively, establishes a release position, in which the target lugs 
pass between the corresponding retaining ring lugs and a retained position 
in which the retaining ring lugs interengage the target lugs. These 
positions are selectable by rotating the target. As detailed in FIG. 5, a 
retaining pin 210 is provided in the outer ring (see also FIG. 8). The 
retaining pin limits rotation since the retaining pin 210 binds upon one 
of the outer target lugs 192. The retaining pin 210 enables rotation of 
the target by approximately 45.degree. between the fully-retained and a 
fully-removable circumferential orientation. 
To attach or remove a target, one aligns the target lugs 190 and 192 with 
the spaces between retaining ring lugs 208 and 200, respectively, and 
moves the target 150 through the retaining ring structure in an axial 
direction (perpendicular to the plane of the target sputtering surface 
170). To lock the target 150 one rotates the target until the target lugs 
190 and 192 are brought into full interengaging contact with the retaining 
ring lugs 208 and 200, respectively, and the retaining pin 210 restricts 
further rotational movement. 
For further target security, the retaining rings 144 and 146 according to 
this embodiment are provided with respective holes 212 and 214. The holes 
212 and 214 receive ends of an eccentric bolt 220 (FIGS. 12 and 13) having 
a central shaft 222, an inner end 224 and an outer head 226 that are each 
eccentrically located relative to the central shaft 222. The outer shaft 
diameter is approximately 0.315 inch. The eccentricity EC is approximately 
0.025 inch. The head 226 of the bolt 220 according to this embodiment 
includes a recess for an Allen wrench or similar torque-transmitting 
adjustment tool. By rotating the bolt 220 the inner and outer retaining 
rings 144 and 146 can be moved toward and away from the target 150. The 
bolt is secured within the base 240 upon which the target 150 rests. 
Hence, the rings 144 and 146 float relative to the base 240 and enable the 
target to be pressed tightly against the base 240. The locking action of 
the rings 144 and 146 also causes the O-rings 134 and 136 to seal against 
the bottom surface of the target 150. 
A circumferential recess 244 (FIG. 12) is provided in the bolt 220. The 
recess 244 interengages a locking pin 246 (FIG. 4) to prevent axial 
movement of the bolt once it is mounted within the base 240. Rotational 
movement of the bolt 220 about the pin 246 is enabled. Four bolts (220) 
are provided at 90.degree. intervals adjacent each of the retaining ring 
lugs. To attach or remove a target 150 the user must rotate each of the 
bolts so that the retaining rings 144 and 146 are moved upwardly toward 
the target (away from the base 240) enabling the target to be rotated. The 
retaining ring lugs 200, 208 can be engaged or disengaged from the target 
lugs 190, 192 during such rotation. When the lugs 190, 192 of a target are 
located in an interengaging relationship with the retaining ring lugs 200, 
208, the bolts are turned to translate the retaining rings 144 and 146 
toward the base 240 and the target is secure within the sputtering 
apparatus. Note that access to each bolt is gained through a hole 250 
(FIG. 4) on the side of the outer shell 140. However, to move a target 150 
into or out of the sputtering assembly 106, the outer mask 112 must 
generally be separated from the outer shell 140. The water jacket's quick 
release assembly (described above) facilitates separation of the outer 
mask 112. It should be clear that removal and attachment of targets 
according to this embodiment requires relatively few steps and, with 
practice, can be accomplished rapidly and precisely. 
The foregoing has been a detailed description of a preferred embodiment. 
Various modifications and additions to this embodiment are contemplated 
and are believed to be within the scope of the invention. This description 
is, therefore, meant to be taken only by way of example and to otherwise 
limit the scope of the invention. For example, while screws are utilized 
to attach various components, clips or clamps can be utilized, while lugs 
are preferably used as an engagement or retaining means for attaching the 
target to the housing, other quick-disconnect attachments can be used. For 
example, spring or resilient clips, bayonet fasteners or other joiners can 
be employed. In all cases, the housing of this invention can be made to 
permit quick, unobstructed, access to the target for replacement. 
Similarly, the magnet materials utilized herein can be substituted with 
other magnetic materials having similar properties. Likewise, while the 
substrate of this embodiment is located adjacent the opening defined by 
the sputtering assembly 106, it is contemplated that an article to be 
coated with target material can be located remote form the opening. Such 
an article can be of any shape and can be located in the vacuum chamber at 
any position that places it in the path of sputtering material. In fact, 
the article can be omitted and sputtering into the chamber will still 
occur. Finally, while the structures of FIG. 4 are generally cylindrical 
about a central axis, it is contemplated that other shapes, such as ovals 
and multisided shapes can be used.