GB2460456A

GB2460456A - Sputtering apparatus

Info

Publication number: GB2460456A
Application number: GB0809889A
Authority: GB
Inventors: Lars Allers; Alistair Henderson Kean
Original assignee: Mantis Deposition Ltd
Current assignee: Mantis Deposition Ltd
Priority date: 2008-05-30
Filing date: 2008-05-30
Publication date: 2009-12-02
Also published as: GB0809889D0

Abstract

Sputter deposition apparatus comprises a magnetron 20 and a target 24, consisting essentially of the material to be deposited, positioned in front thereof. The target is mounted so as to be moveable sideways relative to the magnetron. This enables the region of the target immediately in front of the magnetron, i.e. the part of the target being etched away, to be continuously or semi-continuously replenished. The target can be a film of material, which can be mounted on a spool (22, fig 3) with one end of the roll extending past the front of the magnetron. If desired, the film can extend past the magnetron to a further spool at which the film is taken up (34, fig 3). The target travels into the low pressure deposition chamber via a seal 44 and exits the chamber via a further seal 50.

Description

Sputter deposition apparatus

FIELD OF THE INVENTION

The present invention relates to the deposition of materials.

BACKGROUND ART

One established method for the deposition of materials is sputter deposition. According to this method, a target composed of the material to be * ** deposited is placed in front of a magnetron in a chamber containing a low :::::: pressure inert gas such as Argon. A plasma is then created immediately above the target, and repeated collisions between high-energy atoms in the plasma : *** and the target surface cause (in effect) forced evaporation of the atoms of the a...

*. target into the low pressure chamber. The evaporated material is not in thermodynamic equilibrium and will condense onto nearby surfaces, creating a thin film coating. Alternatively, the evaporated atoms can be caused to travel through appropriate conditions to create nanoparticles.

This will obviously cause the target 10 to be eroded. Generally, the plasma is formed in a "racetrack" shape 12, i.e. an oval when viewed from above as in figure 1. This makes reasonable use of the available surface area.

As shown in figures 2a through 2b to 2c which show successive stages in a sputter deposition process, as deposition progresses the target 10 in front of the magnetron 14 will principally erode beneath the plasma 16, eventually forming a racetrack-shaped pit 18. This should not be allowed to penetrate through the target 10, else the magnetron 14 will be damaged and the deposited layer will be contaminated with the material of the magnetron. Thus, the target must be replaced regularly, and (for valuable materials) the unused material must be reclaimed.

SUMMARY OF THE INVENTION

The present invention therefore provides sputter deposition apparatus comprising a magnetron and, in front of the magnetron, a target consisting essentially of the material to be deposited, the target being mounted so as to be moveable sideways relative to the magnetron. This enables the region of the target immediately in front of the magnetron, i.e. the part of the target being etched away, to be continuously or semi-continuously replenished.

The target can be a film of material, which can be mounted on a spool with one end of the roll extending past the front of the magnetron. If desired, the film can extend past the magnetron to a further spool at which the film is taken up. In that case, the further spool can be driven thereby to draw the *:*::* target past the magnetron.

Sputter deposition apparatus will usually include a low pressure chamber * of some form, in which the magnetron is disposed. This low pressure chamber can have at least one seal through which the target passes, to allow more I..

* continuity of the process and allow continuous or near-continuous operation.

The target can travel into the low pressure chamber via the seal, for example, *:*. although it will usually be preferable to allow the target to exit the chamber via a further seal.

Experience shows that the nature of nanoparticle formation depends on the exact state of the target. Accordingly, the maintenance of a steady state target face will be beneficial to a mass production' process for nanoparticle deposition, in that nanoparticles of a consistent and reliable quality and nature will be easier to achieve.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way of example, with reference to the accompanying figures in which; Figure 1 shows a view from above of a conventional sputtering target during deposition; Figures 2a, 2b and 2c show sequential development of the sputter target of figure 1 in transverse section as deposition progresses; Figure 3 shows a transverse section through a sputter deposition target according to the present invention; Figure 4 shows the target of figure 3 from above; and Figure 5 shows a sputter deposition target according to a second embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Figures 1, 2a, 2b and 2c have been described already and will not be . described further.

::. Figure 3 shows an embodiment of the present invention. A magnetron 20 of any conventional design is provided. A supply spool 22 holds a long length of a thin film target 24, in the form of a web. Depending on the nature of the target material, this may be a thin flexible sheet of the target material, or it may : be a relatively thick film deposited on a suitable carrier material such as a polymeric substrate. The thin film target 24 is roughly the width W of a conventional target 10, but significantly longer in a transverse direction -typically some orders of magnitude longer. It will typically be somewhat thinner than a conventional target 10; the precise thickness will be a compromise between ease of handling and the required speed of movement past the magnetron 20, so long as the target 24 is sufficiently thin as to be flexible.

From the supply spool 22, the thin film target 24 passes a first idler roller 26 which it exits in the direction of arrow 28, to pass immediately in front of the magnetron 20. At that point, a plasma 30 in the form of a conventional racetrack layout is able to sputter the material of the target 24. The target 24 then continues to a second idler roller 32 and then to a take-up spool 34 where the target 24 is collected.

In this embodiment, the take-up spool is driven at an appropriate speed so that the target 24 is drawn past the magnetron 20 at a sufficient rate in the light of the target material thickness and the erosion rate during sputtering to use most of the thickness of the target material except for a suitably thin insurance layer.

At any instantaneous point during deposition, the target 24 is likely to resemble figure 4 when viewed from above; an unused portion 36 is yet to reach the plasma 30. A part-etched region 38 enclosed by the racetrack-shaped plasma 30 has only passed through one arm of the racetrack, while a used portion 40 has passed through both arms of the racetrack and has been etched * * to the fullest extent intended. Some thickness will preferably remain, to prevent etching of the magnetron material and to provide for some physical support for the material on the take-up spool 34. * **

Indeed, the thickness of and/or the presence of some remaining material in the region 40 can act as a quality control reassurance that the speed of :..: movement of the target material 24 is correct. In a further development, the *:*. thickness could be monitored by electronic, optical, acoustic or other means and used as a feedback control for the drive speed of the take-up spool 34 or other drive means for the target material 24. If the thickness of the region 40 increases above a set level, the drive speed could be reduced. Likewise, if the thickness decreases below a set level then the drive speed could be increased.

If the thickness were to be observed to have fallen to zero, then appropriate warnings could be issued that recently coated items may be contaminated with the material of the magnetron. To act as an insurance, a thin layer of target material could be placed beneath the moving layer 24; the alarm would then alert an operator that this "insurance" layer needed to be replenished.

Such a magnetron and target device would then be used in generally the same manner as conventional sputter deposition apparatus, i.e. to produce thin film coatings, to produce nanoparticles, and so on. However, the apparatus of this embodiment has the advantage that the target material is continually replenished until the supply spool 22 is emptied. This allows for a potentially very much longer operation time as compared with a conventional sputter deposition apparatus and allows the process to move towards a quasi-continuous mode of operation, rather than the discrete batch mode that is required by conventional arrangements. Such a change makes sputter deposition much more suitable for commercial use rather than just for laboratory use.

Figure 5 shows an alternative embodiment that offers essentially continuous operation. The supply spool 22 and the take-up spool 34 are removed entirely from the low-pressure chamber 42 and are located outside where they are accessible to an operator. The target 24 leaves the supply spool and passes through one or more additional vacuum chambers (not shown) *a. before entering the low pressure chamber 42 via a pair of suitable sealing rollers 44 such as rubber, copper, VitonTM or the like, set in its wall. The use of additional vacuum chambers between the low pressure chamber 42 and the :.:::i outside atmosphere allows the maintenance of a high vacuum and therefore cleanliness in the low pressure chamber 42. Once inside the low pressure * chamber 42, the target 24 is then guided into its position in front of the :.:; magnetron 20 by idler rollers 46.

After passing the magnetron 20 and being etched, further idler rollers 48 then guide the target 24 to a further, exit, pair of sealing rollers 50 from which it can proceed to a take-up spool (or other destination as desired) via the previously-mentioned additional vacuum chambers or further such chambers.

Again, the exit side of the device will generally be the preferred location for a drive means adapted to draw the target material 24 through the device.

In this embodiment, as and when the web of target material 24 is exhausted, the start of a fresh web can be attached so that deposition can continue indefinitely. The process then becomes continuous in nature.

It will of course be understood that many variations may be made to the above-described embodiment without departing from the scope of the present invention. * ** * * * * ** * * ***. * ** * S S **** * I.. 4 ** * * S 4*. S *5 5 * * S * **

Claims

CLAIMS34 1. Sputter deposition apparatus, comprising a magnetron and, in front of the magnetron, a target consisting essentially of the material to be deposited, the target being mounted so as to be moveable sideways relative to the magnetron.
2. Sputter deposition apparatus according to claim 1 in which the target is a film of material.
3. Sputter deposition apparatus according to claim 2 in which the film of material is mounted on a spool, one end of the roll extending past the front of the magnetron.
4. Sputter deposition apparatus according to claim 3 in which the film extends past the magnetron to a further spool at which the film is taken up.
5. Sputter deposition apparatus according to claim 4 in which the further spool is driven, thereby to draw the target past the magnetron.
6. Sputter deposition apparatus according to any one of the preceding claims, further comprising a low pressure chamber in which the magnetron is disposed, the low pressure chamber having at least one seal through which the target passes.
7. Sputter deposition apparatus according to claim 6 in which the target travels into the low pressure chamber via the seal.
8. Sputter deposition apparatus according to claim 7 in which the target exits *:*. the chamber via a further seal.
9. Sputter deposition apparatus substantially as herein described with reference to and/or as illustrated in the accompanying claims.