The invention relates to an end-block that is used to rotatably carry a sputtering target in a sputtering apparatus. More in particular it relates to end-blocks that are relatively flat when considered along the symmetry axis of the target, while still housing inside all or some of the necessary means to energise, cool, seal, support and rotate the target.
Sputtering material from a target to cover a substrate has become common practice in a wide range of technical fields such as integrated circuit manufacture, large area glass coating and nowadays more and more for the coating of flat panel displays. Such sputtering takes place under a reduced pressure atmosphere wherein sputtering or reactive gases or mixtures of both are admitted in a controlled way. Free electrons hopping in a magnetically confined racetrack ionise the gas atoms or molecules in the vicinity of the target surface. These ions are subsequently accelerated towards the target that is negatively biased, thereby dislodging the target atoms and giving them enough kinetic energy to reach the substrate and coat it. The shape of the racetrack is defined by a static magnetic array, close to that target surface that is opposite to the surface that is being sputtered. Such a deposition process is commonly called “magnetron sputtering” due to the presence of the magnetic array.
A plethora of apparatus has been developed, designed and built with a specific application in mind. The first, smaller magnetron sputtering apparatus used stationary planar targets initially prevalently circular in form (i.e. like the silicon wafer that was sputtered upon). Later also elongated, rectangular shapes for coating of larger substrates that pass under the target became available (e.g. as described in U.S. Pat. No. 3,878,085). Such elongated planar targets are now commonly used in dedicated ‘display coaters’ for the manufacturing of flat panel displays like liquid crystal displays (LCD) and plasma screens. These planar targets are usually mounted in the access doors of the apparatus; the target surface being easily accessible (with doors open) and spanning the length of and even extending over the substrate width. In a display coater the substrate to be coated is held under a slant angle (7° to 15°) out of the vertical and leans on a conveying system. As the target must be parallel to the substrate in order to obtain a uniform coating, the target must be mounted under substantially the same angle.
Stationary targets are easy to cool and energise (as they are static with respect to the apparatus), but they have the disadvantage that the target material is only eroded away beneath the racetrack. The useable lifetime of the target thus being limited to that point in time just before the target is first punctured. The problem of non-uniform erosion can be dealt with by introducing a magnet array that rotates relative to the target surface (such as e.g. introduced in U.S. Pat. No. 4,995,958 for circular planar magnetrons) or that translates relative to the target surface (such as e.g. described in U.S. Pat. No. 6,322,679 for elongated planar magnetrons). Such constructions—although alleviating the uneven erosion problem to a great extent—make the system more complex.
Large area coaters to coat e.g. window glass with all kinds of stacks of functional coatings are usually equipped with a rotating, tubular sputtering target. In this application the economic driver is throughput at a low material cost and a good quality. Rotating tubular targets are the ideal choice for that, as they can span large widths and can be used for a long period of time. The trade-off is that the target itself is rotating relative to the apparatus and hence a complex and space occupying ‘end-block’ is needed to bear, rotate, energise, cool and isolate (coolant, air and electricity) the rotating target while holding the magnet array fixed inside. Two types of arrangement exist:
It is a general object of the invention to reduce or eliminate the problems associated with the prior art. It is an object of the invention to make rotating sputtering targets available to display coaters, either as original equipment or as a retrofit to existing installations. It is a further object of the invention to reduce the end-block's length in the direction of the rotation axis of the target i.e. to provide a ‘flat’ end-block. According another aspect of the invention, a sputtering apparatus is provided that uses flat end-blocks.
While thinking about a solution to the problem, it struck the inventors that all prior-art—such as U.S. Pat. No. 5,096,562, U.S. Pat. No. 5,200,049, US 2003/0173217—hitherto mounted the different means for bearing, rotating, energising, cooling and isolation (air, coolant and electrical), nicely one after the other along the rotation axis of the target tube inside an end-block. Out-of-the-box thinking brought them to the basic principle of putting these means substantially radial to one another, in order to save space in the rotation axis direction. This new way of designing end-blocks is described in the claims attached that will now be explained in more detail.
A first aspect of the invention relates to the end-block with the combination of features of claim 1. Specific features for preferred embodiments of the inventive end-block are set out in the dependent claims 2 to 21.
An end-block is claimed. Such an end-block links the sputtering target in the sputtering apparatus to the outside of the sputtering apparatus. Such an end-block is preferably mountable as a single unit on a sputtering apparatus, although a wall-integrated end-block could be envisaged as well. Within an end-block the pressure is higher than in the evacuable apparatus, preferably the pressure is atmospheric. Means that are removable with the target tube or the removable magnet bar assembly are considered as not to belong to the end-block. The primary function of the end-block is to carry and to revolve the target around an axis of rotation. As sputtering is performed under a low gas pressure, the end-block must be gastight at all times and surely when it is rotating. As the sputtering of the target generates a lot of heat on the target surface, the target must be cooled which is normally done with water or another suitable coolant. This coolant must be fed and evacuated through the end-block. Also the target must be fed with an electrical current in order to maintain the target above a certain electric potential. Again this electrical current must pass through the end-block. In order to incorporate all these functions, an end-block may comprise different means:
The inventive end-block comprises at least two of the above-identified five means (A, B, C, D and E). Hence, the inventive end-block may comprise a subset of those means as long as there are two or more of them in the subset while the other means or incorporated in another end-block (this adds up to exactly 14 technologically meaningful subsets). The set of all five means is also considered as a subset.
The basic idea of mounting these different means radial instead of longitudinally (one after the other) can now be expressed conveniently with the characterising portion of claim 1. Two means are considered to be mounted radial relative to one another when the two ranges corresponding with those means overlap one another on the axis of rotation. The overlapping between the ranges can be partial i.e. when both ranges only have a part in common. Or it can be complete, in which case one means is completely covered, either radial inward or radial outward by the other means. In the inventive end-block, at least two means overlap one another. It is thus not excluded that more than one pair of overlapping means are present for example that two pairs of overlapping means exist within one single end-block (which implies of course that three means must be present within the end-block). It is also not excluded that three means overlap one another (which is equivalent to three pairs wise overlaps). The person skilled in the art will readily realise that building more means radial, the maximum being of course five, can reduce the axial length of the end-block further.
In the depending claims 2 to 9, particularly useful subsets of means comprised in an end-block are claimed wherein each time at least two different means are mounted radial to one another.
In a first preferred embodiment—claim 2—the drive means (A), the electrical contact means (B) and coolant seal means (D) are combined in a single end-block (other means being implemented in e.g. the end-block at the other end of the target). With this preferred combination the minimum means for having all interconnections (coolant, electricity, movement) through a single end-block are present. At least two of the mentioned means must overlap one another.
A second preferred subset—claim 3—comprises the drive means (A), bearing means (C) and vacuum seal means (E) in a single end-block (the other block must than accommodate for the remaining means). Such a block is described in US 2003/0136672, FIG. 3. Again at least two means must overlap in order to have an end-block according the invention. More pairs of overlapping means are not excluded.
In a third claimed subset—claim 4—the end-block houses the rotatable electrical contact means (B), the bearing means (C) and the vacuum seal means (E) compactly. At least two of the means must overlap, more overlaps of course not being excluded.
A fourth subset—claim 5—incorporates the bearing means (C), the rotatable coolant seal means (D) and the rotatable vacuum seal means (E) in a single end-block (a combination depicted e.g. in U.S. Pat. No. 5,096,562, FIG. 6, left block). The inventive concept requires that at least two, and possibly more, of them must pair wise overlap.
A fifth subset—claim 6—incorporates four means namely the drive means (A), the bearing means (C), the rotatable coolant seal means (D) and the rotatable vacuum seal means (E) into a single end-block (much like U.S. Pat. No. 5,096,562, FIG. 2, left block). The inventive end-block has at least two out of the four means in an overlapping position, more overlapping pairs of means being possible as well.
A sixth subset—claim 7—embodies a drive means (A), a rotatable electrical contact means (B), a bearing means (C) and a rotatable vacuum seal means (E) in a single end-block (cfr. U.S. Pat. No. 5,096,562, FIG. 6, right block). Again in the inventive end-block, at least two of the means are mounted radial and overlapping. Likewise more pairs of overlapping means are possible.
A seventh subset—claim 8—comprises the rotatable electrical contact (B), the bearing means (C), the rotatable coolant seal (D) and the rotatable vacuum seal (E) in one end-block (as in US 2003/0136672 FIG. 6). According the inventive concept at least two out of the four means must be situated in an overlapping position. However, more pairs of overlapping means are equally well possible, the maximum being six.
Finally an eighth subset as claimed in claim 9 comprises all means—the drive means (A), the rotatable electrical contact means (B), the bearing means (C), the coolant seal means (D) and the vacuum seal means (E)—in a single end-block (FIG. 1 of U.S. Pat. No. 5,200,049). It is not excluded that the other end is held by a bearing means. At least two means must be arranged radial according the inventive concept, but it applies equally well if more pairs of overlapping means are present.
The overlapping of two functionalities is further described in dependent claims 10 to 19. All combinations can depend on claim 1. For some subsets of means, only a number of overlapping pairs are possible. In a first preferred combination, at least the drive means range and the electrical contact means range overlap (claim 10). In a second combination (claim 11), the drive means and the bearing means are mounted radial to one another. Claim 12 describes a preferred compact embodiment where the drive means is radial with respect to the coolant seal. Alternatively, the vacuum seal can be mounted radial with respect to the drive means (Claim 13). Claims 14, 15 and 16 define preferred combinations where one of the group consisting of the bearing means, the coolant seal and the vacuum seal is situated radial to the electrical contact means: compact embodiments that are easy to implement. A combination of radial mounted bearing means and coolant means (claim 17) or bearing means and vacuum seal means (claim 18) is fairly easy to implement and thus preferred to compact the end-block. The same applies to the radial combination of coolant seal means and vacuum seal means (claim 19).
Again: the combinations as defined in claims 10 to 19 do not exclude the possibility that more than one pairs of means overlap in a single end-block. Even more overlaps are possible in a single end-block e.g. three means radial to one another. Indeed it is perfectly well possible—for example—to mount the bearing means, the electrical contact means and the coolant sealant radial to one another as will be demonstrated in the embodiments.
The end-block according the invention can be of the right-angled type (claim 20) wherein the axis of rotation of the target is parallel to the wall on which the end-block is mounted. Or it can be of the straight-through type (claim 21) i.e. wherein the axis of rotation of the target is perpendicular to the wall.
A second aspect of the invention relates to the sputtering apparatus using the inventive end-block according the features of claim 22. Specific features for preferred mountings of the end-block in the sputtering apparatus are defined in the dependent claims 23 to 24.
As was explained in the objects of the invention, the end-blocks according the invention are particularly intended—without being limited thereto—to be mounted inside a sputtering apparatus such as a display coater. Such a sputtering apparatus has an evacuable space delimited by walls. The sputtering apparatus with the inventive end-block or end-blocks situated on one of these walls is particularly claimed (claim 22). More preferred is that the end-block(s) is (are) mounted on a removable wall of the chamber for ease of servicing (claim 23). Most preferred is if the end-block(s) is (are) mounted on an access door (claim 24).
The invention will now be described into more detail with reference to the accompanying drawings wherein
The target 220 is rotary driven by the gear wheel 204 through the holder ring 226 thus providing a drive means (A). The gear teeth engage with a worm shaft 205 that on its turn is driven by e.g. an electrical motor (not shown). A mounting ring 207 holds an axial bearing 208 functioning as a bearing means (C). A rotatable electrical contact means (B) is provided by a series of brushes 206 mounted as annular segments coaxial to the rotation axis 222. These brushes 206 are spring mounted in an electrically conductive ring 290 and slide against a slide ring 203. The brushes 206 receive electrical current through the conductive ring 290 that on its turn is fed by the electrical lead 209. The sliding ring 203 is in electrical contact with the target 220 through the gear 204 and the holder ring 226. Two rotatable vacuum seal means (E) are provided by the lip seals 212. The rotatable coolant seal means (D) is incorporated by the coolant seal 210 that is a labyrinth seal. The coolant seal 210 is mounted between the holder ring 226 and the coolant collector 229.
Each of the above means occupies some length along the axis of rotation. For example, the width of the gear wheel 204 occupies a range ‘a’ as indicated in
wherein ‘P’ denotes a Partial overlap and ‘F’ denotes a Full overlap. An empty cell indicates no overlap at all. The person skilled in the art will readily appreciate that the above arrangement leads to an end-block that does not take much space along the longitudinal axis of rotation.
The inventive end-block 300 carries a (partly shown) target 302 around an axis of rotation 304. The target 302 is removably fixed to the end-block through mounting ring 303. The mounting ring is attached to a rotatable intermediate piece 311. The end-block 300 is attached to the wall 306 of a sputtering installation. The end-block has cavities for feeding 305 and extracting coolant 307, the arrows indicating the flow direction of the coolant. The magnet bar (not shown) is held stationary through a connector 309 that tangentially locks into the inner tube 308 that is fixedly connected inside the end-block 300.
The target 302 is driven by a crossed axis, conical gear pair 310-312 whereby gear 312 is actuated by an electrical motor (not shown) through axis 314. The main gear 310 is fixed to the target 302 through rotatable intermediate piece 311. Also attached to the intermediate piece 311 is a commutator ring 320 comprising six brushes 322 that are segment wise distributed over the circumference of the ring 320. The brushes 322 slide against the inside of the stationary contacting ring 324. The target 302 therefore receives its current from the current source (not shown) through leads (not shown), the contacting ring 324, the brushes 322, commutator ring 320 and intermediate piece 311. The target is rotatably carried by two bearings: a ball bearing 332 and a needle bearing 330. The coolant is held in the circuit by two rotary lip seals: the primary seal 342 and the secondary seal 340. Vacuum integrity of the end-block is ensured through two rotary lip seals 350 and 352.
Again the different ranges associated with these means can be identified. They are summarised in Table 2. Small letters refer to the ranges as indicated in
Here the same meaning has been used as in Table 1 for the letters P, F and the empty cell likewise denotes the absence of an overlap. It will be clear from the table that—although the different means only show a small degree of overlapping—the end-block of
The target (not shown) is driven by a toothed belt 412 that engages with a toothed wheel 410. This toothed wheel connects to the 401 target receiving flange through intermediate piece 405. Inside this toothed wheel 410, there is provided a stationary commutator 420 fixed to a connecting electrode 421 that is embedded in the inner body 408. The commutator is provided with six brushes 422, each covering a segment of the circumference of the commutator 420. The brushes are spring mounted and slide against the inner ring 424 fixed inside the toothed wheel 410. The current thus follows the following path from current source (not shown) to target (not shown): electrode 421, stationary commutator ring 420, stationary brushes 422, rotating ring 424, toothed wheel 410, intermediate piece 405, target receiving flange 401. A needle bearing 430 and a larger ball bearing 432 provide the necessary bearing means. A mechanical seal cassette 443 provides a first coolant seal. Such a cassette has two rings of equal diameter that are axially pressed against on another. The contacting faces are polished so precisely that no coolant can escape through the contacting faces 442. The one side of the mechanical seal cassette 443 is tangentially locked in position by means of the pins 441, 441′. The facing tungsten carbide ring 444 tightly fits the rotating intermediate piece 405 and is sealed from the coolant flow by means of two stationary O-rings. A secondary lip seal 440 further secures coolant circuit integrity. Vacuum integrity is ensured through primary vacuum lip seal 450′ and secondary lip seal 450.
Again a table—table 3—can be drawn up that summarises the overlapping regions of this design. The various ranges occupied on the axis of rotation by the different means are identified by the small letters—a, b, c1, c2, d1, d2, e1, e2—on
450′
The embodiments described above have all the necessary means incorporated in one single end-block. The other end of the end-block can thus be left free standing or held centred by means of a centring pin connected to the same wall as the wall the end-block is mounted on.
The person skilled in the art will have little trouble to redistribute the means necessary to make the apparatus operate over two end-blocks—one at each end of the target—by taking these preferred embodiments and eliminating specific means out of them. It will be readily understood that as long as these amended embodiments do show overlapping means, that they fall under the scope of the invention.
Likewise all of the end-blocks described are of right-angled type, i.e. the axis of rotation is parallel to the wall the end-block is mounted on. The person skilled in the art will have little trouble in converting these right-angled types to straight-through types i.e. end-blocks where the axis of rotation is perpendicular to the wall the end-block is mounted on. For example the embodiment of
Accordingly, it is intended that the claims cover all such alterations and modifications that fall within the true spirit and scope of the invention.
Number | Date | Country | Kind |
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04 10 116.0 | Oct 2004 | EP | regional |
05 101 905.7 | Mar 2005 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP05/55143 | 10/11/2005 | WO | 00 | 11/9/2007 |