Magnetron sputtering source and arrangement with adjustable secondary magnet arrangement

Abstract

The magnetron sputtering source comprises a target mount for mounting a target arrangement comprising a sputtering target having a sputtering surface; a primary magnet arrangement for generating close to said sputtering surface a magnetron magnetic field describing one tunnel-like closed loop having an arc-shaped cross-section; a secondary magnet arrangement for generating close to said sputtering surface an auxiliary magnetic field having a substantially arc-shaped cross-section, said auxiliary magnetic field superposing with said magnetron magnetic field and being substantially inversely polarized with respect to said magnetron magnetic field; and an adjustment unit for adjusting said auxiliary magnetic field. The vacuum treatment apparatus comprises such a magnetron sputtering source. The method for manufacturing coated substrates by magnetron sputtering using a magnetron sputtering source comprises the steps of a) generating close to a sputtering surface of a target said magnetron magnetic field; b) generating close to said sputtering surface said auxiliary magnetic field; and c) adjusting said auxiliary magnetic field. In particular, said secondary magnet arrangement comprises several separately adjustable segments. Using the invention, it is possible to determine gauge functions for precisely achieving target thickness distributions.

Claims

1. Magnetron sputtering source comprising a target mount for mounting a target arrangement comprising a sputtering target having a sputtering surface; a primary magnet arrangement for generating close to said sputtering surface a magnetron magnetic field describing one tunnel-like closed loop having an arc-shaped cross-section, wherein the primary magnet arrangement includes a first part and a second part with the magnetron magnetic field formed therebetween; and a secondary magnet arrangement having at least two segments for generating close to said sputtering surface an auxiliary magnetic field having a substantially arc-shaped cross-section, said auxiliary magnetic field superposing with said magnetron magnetic field and being substantially inversely polarized with respect to said magnetron magnetic field, wherein the secondary magnet arrangement is located between the first part and the second part of the primary magnet arrangement, the secondary magnet arrangement enclosing the second part of the primary magnet arrangement and the at least two segments of the secondary magnet arrangement being arranged asymmetrically about an axis extending longitudinally through the second part of the primary magnet arrangement, wherein the auxiliary magnetic field is generated within the tunnel-like closed loop of the magnetron magnetic field, wherein said magnetron sputtering source comprises an adjustment unit for adjusting said auxiliary magnetic field, wherein the closed loop of the magnetron magnetic field is arranged along said sputtering surface, and wherein the magnetron magnetic field forms an erosion trench on the target, the erosion trench having a shape of the tunnel-like closed loop.

2. The magnetron sputtering source according to claim 1, wherein said adjustment unit is an adjustment unit for adjusting said auxiliary magnetic field relative to said magnetron magnetic field.

3. The magnetron sputtering source according to claim 1, wherein said adjustment unit is an adjustment unit for adjusting said auxiliary magnetic field with respect to its shape.

4. The magnetron sputtering source according to claim 1, wherein said adjustment unit is an adjustment unit for adjusting said auxiliary magnetic field with respect to its position.

5. The magnetron sputtering source according to claim 1, wherein said adjustment unit is an adjustment unit for adjusting said auxiliary magnetic field with respect to its magnitude.

6. The magnetron sputtering source according to claim 1, wherein said adjustment unit is an adjustment unit for adjusting a relative position with respect to an axis substantially perpendicular to said target surface, of said primary magnet arrangement and of said primary magnet arrangement of at least a portion of said secondary magnet arrangement.

7. The magnetron sputtering source according to claim 1, wherein said secondary magnet arrangement comprises at least one coil, and wherein said adjustment unit is an adjustment unit for adjusting a current flowable through said coil.

8. The magnetron sputtering source according to claim 1, wherein said secondary magnet arrangement is segmented comprising at least two segments which can be adjusted independently from each other by means of said adjustment unit.

9. The magnetron sputtering source according to claim 1, wherein said secondary magnet arrangement is different from said primary magnet arrangement.

10. The magnetron sputtering source according to claim 1, wherein said primary magnet arrangement forms a magnetic circuit separate from a magnetic circuit formed by said secondary magnet arrangement.

11. The magnetron sputtering source according to claim 1, wherein said superposition is such that a magnetic field resulting from said superposition has a shape different from the shape of said magnetron magnetic field.

12. The magnetron sputtering source according to claim 1, wherein said magnetron sputtering source comprises said target arrangement.

13. Vacuum treatment apparatus comprising a magnetron sputtering source according to claim 1, and comprising a vacuum chamber in which said target arrangement is arranged, and a gas inlet system for introducing a sputtering gas or a reactive gas or both, a sputtering gas and a reactive, into said vacuum chamber.

14. The vacuum treatment apparatus according to claim 13, wherein said secondary magnet arrangement is arranged outside said vacuum chamber.

15. Vacuum treatment apparatus according to claim 13, wherein said adjustment unit is operable from outside said vacuum chamber.

16. Vacuum treatment apparatus according to claim 13, comprising a pumping arrangement for evacuating said vacuum chamber.

17. Method for manufacturing coated substrates by magnetron sputtering using a magnetron sputtering source, said method comprising the steps of a) generating close to a sputtering surface of a target a magnetron magnetic field describing one tunnel-like closed loop having an arc-shaped cross-section; b) generating close to said sputtering surface an auxiliary magnetic field having a substantially arc-shaped cross-section within the tunnel-like closed loop of the magnetron magnetic field, said auxiliary magnetic field superposing with said magnetron magnetic field and being substantially inversely polarized with respect to said magnetron magnetic field, and said auxiliary magnetic field being generated by a secondary magnet arrangement comprising at least two segments; and c) coating a substrate using said magnetron sputtering source with said at least two segments in initial physical states; d) determining a thickness distribution of the coating obtained in step c); for at least one of said at least two segments: e) adjusting a physical state of said at least one segment, thereby adjusting said auxiliary magnetic field; f) coating the substrate using said magnetron sputtering source with said at least one segment and said auxiliary magnetic field as adjusted in step e); g) determining a thickness distribution of the coating obtained in step f); h) determining a distribution function related to a relationship between the thickness distribution determined in step g) and the thickness distribution determined in step d; and i) weighting said distribution function determined in step h) according to the adjustment of step e); j) using the weighted distribution function obtained in step i) to determine physical states of said at least two segments for achieving a target thickness distribution; k) adjusting physical states of said at least two segments according to the physical states determined in step j), thereby adjusting said auxiliary magnetic field; l) coating the substrate using said magnetron sputtering source with said segments as adjusted in step k); and m) iteratively or recursively carrying out steps j), k), and l), wherein the closed loop of the magnetron magnetic field is arranged along said sputtering surface, and wherein the magnetron magnetic field forms an erosion trench on the target, the erosion trench having a shape of the tunnel-like closed loop.

18. The method according to claim 17, wherein step k) is carried out using an adjustment unit of said magnetron sputtering source.

19. The method according to claim 17, wherein step k) comprises adjusting said auxiliary magnetic field relative to said magnetron magnetic field.

20. The method according to claim 17, wherein step k) comprises adjusting said auxiliary magnetic field with respect to its shape.

21. The method according to claim 17, wherein step k) comprises adjusting said auxiliary magnetic field with respect to its position.

22. The method according to claim 17, wherein step k) comprises adjusting said auxiliary magnetic field with respect to its magnitude.

23. The method according to claim 17, wherein step k) comprises adjusting a relative position with respect to an axis substantially perpendicular to said target surface, of said primary magnet arrangement and of at least a portion of said secondary magnet arrangement.

24. The method according to claim 17, wherein step k) comprises adjusting a current flowable through a coil.

25. The magnetron sputtering source according to claim 1, wherein each of the magnets of the secondary magnet arrangement is horizontally aligned or yoke-shaped.

26. The method for manufacturing coated substrates according to claim 17, wherein each of the magnets for generating said auxiliary magnetic field is horizontally aligned or yoke-shaped.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Below, the invention is described in more detail by means of examples and the included drawings. The figures show:

(2) FIG. 1 a schematized illustration of a vacuum treatment apparatus with a secondary magnet arrangement externally adjustable with respect to its position, in a cross-sectional view;

(3) FIG. 2a a schematized illustration of a top-view onto a magnet system of a rectangular magnetron with a segmented secondary magnet arrangement;

(4) FIG. 2b a schematized illustration of a top-view onto an erosion area (race track) on a target of a rectangular magnetron;

(5) FIG. 3a a schematized illustration of a detail of a vacuum treatment apparatus with a secondary magnet arrangement comprising several segments, in a cross-sectional view, and a curve;

(6) FIG. 3b a schematized illustration of a mechanical guiding appliance for a height-adjustable segment, in a side view;

(7) FIG. 4 a schematized illustration of a detail of a vacuum treatment apparatus with a secondary magnet arrangement comprising several segments, in a cross-sectional view, and a several gauge curves W.sub.k(y);

(8) FIG. 5 a coating thickness profile G(y) on a substrate, a calculated thickness correction profile K(y), and a coating thickness profile G(y) obtained after applying corresponding corrections;

(9) FIG. 6a a schematized illustration of a magnet arrangement comprising a secondary magnet arrangement comprising several coils with shunts, in a cross-sectional view;

(10) FIG. 6b a schematized illustration of a magnet arrangement comprising a secondary magnet arrangement comprising several coils with shunts, in a top view;

(11) FIG. 7 a schematized illustration of a top-view onto a magnet system of a rectangular magnetron comprising a segmented secondary magnet arrangement with non-symmetrically arranged segments;

(12) FIG. 8a a schematized illustration of a top-view onto a magnet system of a round magnetron;

(13) FIG. 8b a schematized illustration of a side-view of a magnet system of a round magnetron;

(14) FIG. 9 a schematized illustration of several examples of segments for secondary magnet arrangements;

(15) FIG. 10 a block-diagrammatical illustration of a method for iteratively optimizing the agreement between an actual thickness distribution and a target thickness distribution.

(16) The reference symbols used in the figures and their meaning are summarized in the list of reference symbols. The described embodiments are meant as examples and shall not confine the invention.

DETAILED DESCRIPTION OF THE INVENTION

(17) FIG. 1 shows a schematized illustration of a vacuum treatment apparatus with a secondary magnet arrangement 13 externally adjustable with respect to its position (along coordinate axis z; target surface 4a being aligned parallel to plane x-y), in a cross-sectional view. Several components of the vacuum treatment apparatus and their functions have been described before in the discussion of the state of the art; for the sake of conciseness, this will not all be repeated here.

(18) Primary magnet arrangement 1,2 generates a magnetron magnetic field (field lines referenced as 12), part 1 of the primary magnet arrangement forming an outer closed loop of magnets, part 2 an inner line of magnets.

(19) Secondary magnet arrangement 13 is arranged between part 1 and part 2 generating an inversely polarized auxiliary magnetic field (field lines referenced as 16). In a very simple case, the secondary magnet arrangement 13 can comprise two or more horizontally aligned permanent magnets or yoke-shaped permanent magnets.

(20) FIG. 9 shows several exemplary segments of which secondary magnet arrangement 13 can be composed. Each segment may comprise one or more permanent magnets, one or more shunts and/or one or more coils. The upper-most example comprises a coil on a shunt, the lower two examples each comprise two permanent magnets connected by a shunt.

(21) Using pairs of oppositely-polarized permanent magnets interconnected by a shunt or ferromagnetic back plate (cf. lower-most example in FIG. 9) allows to efficiently optimize the magnetic field above the target 4, thus achieving a particularly broad area with field lines 17 of the superposition of the magnetron magnetic field (cf. 12 in FIG. 1) and the auxiliary magnetic field (cf. 16 in FIG. 1) substantially parallel to the target surface 4a. The movement of the segments of the secondary magnet arrangement 13 is preferably carried out in a precise way, so as to achieve a precise and well-controlled thickness distribution of a coating 7 on a substrate 6. In practice, it is advantageous to provide an adjustment precision of better than 1 mm or rather of the order of 0.1 mm or better. This can be achieved, e.g., by external units 15 for mechanical displacement mechanically connected to the segments of the secondary magnet arrangement 13 via rigid mechanical connections 14 functioning as guidances 14 for the segment movement. Units 15 belong to an adjustment unit 30 and have to ensure a reproducible precise shifting of the segments. For example, a unit 15 can be or comprise a micrometer screw with an adjustment scale or, preferably, comprise a stepper motor. Adjustment unit 30 further comprises a control unit 35 which controls the units 15.

(22) Units 15 are, as shown in FIG. 1 and FIG. 3a, preferably mechanically connected (coupled) to ferromagnetic back plate 3 of primary magnet arrangement 1,2, so as to provide a geometrically well-defined positioning of the segments of secondary magnet arrangement 13 with respect to the primary magnet arrangement 1,2, thus ensuring that the resulting magnetic field above the target 4 is (in shape and strength) as little as possible influenced by external influences. Note that in FIG. 3a, five segments M1, M3, M5, M7, M9 of the secondary magnet arrangement 13 are shown.

(23) Preferably, the z-movement of each segment is accomplished by means of a micrometer screw aligned along the z-axis, as shown in FIG. 3b, which shows in a side view a schematized illustration of a mechanical guiding appliance 19 for a segment M1. This, because strong forces in z-direction are exterted on the segments of the secondary magnet arrangement 13 which result from magnetic interactions with magnets of the primary magnet arrangement 1,2. Because of these forces, the screw is always mechanically stressed (usually tensile stress), which advantageously results in the fact that no mechanical play exists when moving the segments for adjusting their z-position. This ensures a great reproducibility of the z-movements of the segments.

(24) Furthermore, it is also advantageous to provide the segments of the secondary magnet arrangement 13 with at least one additional mechanical guidance 19 for the linear movement along the z-direction, since in case of different adjustments for neighboring segments, torques and forces will occur because of magnetic interactions between these segments, said torques and forces resulting, in case of a non-specific mechanical guidance, in a turning, a tilting or a shifting of the segments, which can result in the movement mechanics getting stuck or in a non-reproducible adjustment of the segment position or in a change of the magnetic field (in particular its shape) due to a tilt of a segment. The mechanical guidance can be realized by one or more pins in conjunction with corresponding holes in the segment, see FIG. 3b (reference 19 and segment M1).

(25) The screws 18 are preferably realized with precise micrometer threads small thread pitch (typically 0.1 to 1 mm path per turn), so as to ensure a sufficient precision. In addition, the screws 18 can be provided with readable scales, so as to allow an adjustment as reproducible as possible. The screws can also be operable by a motor, wherein stepper motors are particularly suited, by means of which precise and reproducible changes of the rotation angle of their driving axle can be accomplished.

(26) In order to achieve a locally variable adjustability of the deposition rate across the target, the movements of the segments of the secondary magnet arrangement 13 (each segment having a certain length) have to be controllable independently. The finer the segmentation of the secondary magnet arrangement 13, the more precisely the local field strength can be adjusted, i.e. a precise adjustability of the local deposition rate necessitates a large number of short segments. In practice, nevertheless, the number of segments will be limited in order to keep the efforts for the adjustment manageable. In order to achieve a high target utilization, the secondary segments (be it permanent magnets or shunts or coils or combinations thereof) will usually be located several millimeters behind the target. The distance to the region 5 of high plasma density located several millimeters above the target typically amounts to 15 to 30 mm, in which case a thickness of the target arrangement (target 4 including a cooling plate not shown in the figures) of 10 to 15 mm has been assumed.

(27) Because of the distance of the segments (M1, M3, M5, M9, see FIG. 3a) to the region 5 of high plasma density, a shift along z of a segment results in an effect affecting the magnetic field above the target 4 over a length along y which is significantly larger than the physical length b (along y) of the shifted segment (cf. FIG. 3a).

(28) The upper part of FIG. 3a illustrates the effect that a movement of a segment (segment M5) can have in terms of changes t in a coating thickness distribution resulting therefrom (when coating a substrate). The change t in the coating thickness distribution (comparing thickness distributions of coatings deposited before and after the movement of the segment) results from a change in the deposition rate distribution. In the illustration of FIG. 3a, it is assumed that the substrate 6 is moved across the target along x during the sputter coating. The change t in the coating thickness distribution has a maximum above the middle of the segment M5, decreasing with increasing distance in y-direction from that middle. The wide extension of the t curve comes about from the physical width b of the segment (M5) and an instrinsic quantity w which comes about from the extension of the magnetic field (along y) of segment M5 (above the target surface) and the three-dimensional sputtering effect of target material because of the ions from the plasma region above the target 4. The value of the quantity w can be used as a lower limit for a selection of a physical width of the segments. The extension (along y) of the effect of shift (along z) of a segment amounts to at least 2 w along the y-axis, independent of the physical width of the segment.

(29) For the case of a rectangular magnetron (cf., e.g., FIG. 2a) having a target width (along x) of 12.5 cm and a length (along y) of 62 cm, a value of 60 to 70 mm results for the intrinsic quantity (intrinsic width) w. In case of that example, it makes sense to use segments of a width (along y) of 60 to 70 mm.

(30) Considering the fact that the uniformity of the coating thickness strongly decreases towards both edge regions (in y) of the magnetron (corresponding to the curves of the race track 11, cf. FIG. 2a, 2b), and that for this reason, for the above-sketched exemplary case, a width of only 20 cm around the middle of the target 4 can be used for obtaining a uniform coating of substrates, a number of 5 to maximum approximately 8 segments (distributed along y) results as a suitable number of segments per side (left L and right R, respectively, of the magnetron) for correcting the coating thickness profile.

(31) The length (along y) of these segments does not necessarily have to be identical, see, e.g., FIGS. 2a, 3a, 4. As experience has shown, the field distribution in the middle of a magnetron changes less than near its ends, for which reason it can be advantageous to choose a larger length of the segments near the middle of the magnetron and a smaller length towards the ends of the magnetron (with respect to the y direction), as shown in FIGS. 2a, 3a.

(32) The left region L and right region R (cf., e.g., FIGS. 2a, 6b and 7) of a linear magnetron contribute equally to the deposition rate if the segments on the left (L) and right (R) are adjusted equally with respect to their position. For an improved and more precise adjustability of the coating thickness distribution, it can be advantageous to shift the y-locations of the segments on the left (L) with respect to the y-position of the segments on the right (R) by an offset (see FIG. 7). Accordingly, the set of segments in the left region L, i.e. M1, M3, M5, M7, M9, is arranged with respect to a symmetry plane A of the primary magnet arrangement 1,2 in a non-symmetrical manner with respect to the set of segments in the right region R, i.e. M2, M4, M6, M8 M10. This way, the influences on the coating thickness distribution of the different sets of segments on the left L and right R of the magnetron, respectively, affect the coating thickness distribution at shifted locations (with respect to the y position). This makes particularly much sense in the case of substrates being moved in x direction during the coating. The magnets MX shown, e.g., in FIG. 7, which are located close to the ends of the magnetron, can be dispensed with, in which case part 1 of the primary magnet arrangement will usually be configured accordingly. In some Figures, no magnets MX are shown, accordingly. If present, magnets MX will in many cases be not adjustable and, accordingly not contribute to the adjustability of the auxiliary magnetic field. Magnets MX will rather be shunts than permanent magnets.

(33) In the following, a method for specifically correcting a coating thickness distribution will be discussed, more specifically, a method for specifically correcting a coating thickness distribution by means of externally adjustable positions (with respect to a direction perpendicular to the target surface, i.e. along z) of segments of a secondary magnet arrangement 13, in particular a method accomplishing this at substantially constant target use.

(34) Firstly, the z-positions of the segments are adjusted for reaching an initial position each, in particular a pre-defined initial position, see, e.g., FIG. 4, segments M1, M3, M5, M7, M9. With these initial positions, a resulting basic thickness distribution G(y) is determined by coating a substrate and measuring, e.g., by reflection or transmission measurements or other suitable methods, preferably in-situ methods. FIG. 5 shows such an exemplary basic distribution G(y).

(35) In order to achieve a calibration, the z-position of a segment k (M.sub.k) is readjusted (shifted) in a defined way by a value p.sub.k (a length, along z), and the relative change V.sub.k(y) in the coating thickness distribution is determined, e.g., by dividing a coating thickness distribution obtained with segment k readjusted as described by the basic distribution G(y). V.sub.k(y) is then divided by the shift p.sub.k. The resulting distribution function

(36) $W_{k} (y) = \frac{1}{p_{k}} .Math. V_{k} (y)$

(37) is a gauge function for the influence of segment k on the thickness distribution. Such a calibration function is determined for each of the segments of the secondary magnet arrangement 13. FIG. 4 schematically shows in its upper portion several such gauge functions. Of course, before determining a gauge function for another segment, the formerly readjusted segment is repositioned to its initial position, so as to really separate the influence of the currently examined segment from the influences of all other segments and to base on the same set of initial positions. The so-determined gauge functions W.sub.k(y) are used for calculating adjustments required in the future for carrying out specific corrections.

(38) With s.sub.k a set of adjustments (shifts along z) of the segments, a correction or change of the distribution of approximately

(39) $K (y) = \underset{k}{.Math.} s_{k} .Math. W_{k} (y) .$

(40) results. A new thickness distribution S(y) achievable with a set s.sub.k of adjustments (shifts) can, accordingly, be obtained as the sum of basic distribution G(y) and correction K(y):
S(y)=G(y)+K(y)

(41) When a given target thickness distribution T(y) has to be achieved, the values s.sub.k can be found by means of a mathematical optimization method, in particular one which minimizes the differences between the resulting thickness distribution S(y) and the target distribution T(y). E.g., this can be formulated as a minimization of the following sum r of the differences over all positions y

(42) $r = \underset{Pos . y}{.Math.} {(G (y) + \underset{k}{.Math.} s_{k} .Math. W_{k} (y) - T (y))}^{2}$

(43) which has to be as small as possible; or a corresponding integral can be minimized. Solving this mathematical optimization problem means obtaining a set of values s.sub.k which shall be used as correcting adjustments of the segment-z-positions for a subsequent coating process. Using these positions, a coating will be produced, and its thickness distribution function, referred to as new thickness distribution function G(y), will be determined (by measuring). G(y) will be much more similar to target distribution function T(y) than G(y). FIG. 5 shows, in its lower portion, an example where T(y)=0 was assumed.

(44) It is now preferably possible to iteratively apply the above-described method to G(y), so as to further optimize deviations of obtained distributions from the target distribution. In other words, using the new G(y) in the way G(y) has been used above, another set of corrections (with usually much smaller readjustments than the former set s.sub.k)which are now position changes with respect to the most recently used positionscan be determined and applied to the recent-most positions, so as to approximate T(y) better and better. Additional drifts and changes in the (relative) thickness distribution function of the coating process possibly occurring will be, by means of the above-described method, corrected quasi-continuously, namely after each newly-determined new set of adjustments, which can be after each substrate coating, or only after every m'th coating has been produced, with m=2 or 5 or 10 or more, depending on the quality requirements and the process stability.

(45) FIG. 10 shows a block-diagrammatical illustration of a method for iteratively optimizing the agreement between an actual thickness distribution and a target thickness distribution.

(46) It is, of course, also possible to iteratively repeat the gauging, in particular in the sense that, once a quite reasonable agreement between actual thickness distribution and target thickness distribution has been achieved (in the above-described way), the corresponding positions are used as initial positions for another gauging procedure, in which for each of the segments the influence of a z-position change of the corresponding segment is determined, such as to yield improved gauge functions.

(47) Of course, it is not possible to produce any arbitrary distribution function T(y) using the above-described procedure; the target distribution function T(y) has to be at least approximately composable of the gauge functions W.sub.k(y) of the segments. The target distribution functions may not strongly change within a width comparable to the width given by the above-discussed intrinsic width w.sub.k (index k designating each segment). The probably most often requested case also having the greatest relevance in practice, namely the case of a uniform distribution, i.e. T(y)=0, has these properties and therefore is well susceptible to optimizations of the above-described kind.

(48) The correction of coating thickness distributions as mainly discussed so far is accomplished mainly by locally changing the magnetic field strength in the region of high plasma density above the target. Since the corrections are usually in the range of 0% to 10%, it can be assumed with a reasonable degree of precision that the interrelation between the (z) position of the segments of the secondary magnet arrangement 13 and the corresponding changes in the thickness distribution function are (in a first approximation) linear. When the above-described method is carried out iteratively, the deviation between actually obtained distribution G(y) and target distribution T(y) will be smaller step by step, and accordingly, the precision of the linear approximation will be increasing.

(49) Instead of changing the magnetic field in the region 5 of high plasma density by changing the z-position of the segments of the secondary magnet arrangement 13, one can also do so by means of electromagnets, i.e. by means of coils, see FIGS. 6a and 6b, through which an adjustable current flows. Around shunts (ferromagnetic material) generating an auxiliary magnetic field, wire can be wound, i.e. the shunts can be provided with a coil each. When no electric current flows through a coil, the corresponding shunt has its usual effect of flattening the magnetic field lines above the target. By means of current flowing through the coil, an additional magnetic field is induced in the shunt which superposes with the field of magnetization induced in the shunt (from the magnetron magnetic field). Since for the correction of distribution functions, magnetic field strengths of the order of some percent are needed, while the absolute field strength of the magnetron magnetic field is in the range of ten Gauss to several hundred Gauss, it is mostly sufficient to provide changes of the magnetic field strength in the range of about 1 to 10 Gauss. Magnetic fields of this order of magnitude are easily generatable by means of coils. An advantage of controlling the auxiliary magnetic field for thickness distribution corrections is, that a correction can be accomplished by setting electrical currents in the power supplies (in FIG. 6a: P1, P3, P5, P7) and therefore without a mechanical movement having to take place. The above-mentioned parameters (adjustments) s.sub.k therefore correspond to electric currents (in the coils) in this case.

(50) The above-described methods not only offer the possibility of manual corrections during the coating process, it also enables, via a suitable control system, an automated correction of the distribution. This will be described by means of the example of changing the auxiliary magnetic field by means of coils. For this, an in-situ registration of the thickness distributions during the coating process, more particularly without breaking the vacuum in the vacuum chamber, is recommended and can even be considered required. It is not necessary, but possible, that a coating is measured while it is still being deposited. When one coating is deposited in several subsequent coating steps (partial coatings), as it is for example often the case when substrates are arranged on a rotating drum so as to periodically have them located close to the high-density plasma region and the target, it is well possible to determine thickness distributions also of the not-yet completed coatings, namely between two of such partial depositions. In such cases, it is even possible to carry out correcting adjustments in the time between the first and the last partial deposition, based on the thickness distributions of those not-yet completed coatings. This allows to very precisely achieve a target thickness distribution. In any event, it is desirable to have coating thicknesses available soon after a coating is completed and without having to break the vacuum in the process chamber.

(51) From a measured thickness distribution, new adjustments s.sub.k for the secondary magnet arrangement will be obtained (which in this case represent coil currents) using a computer-executed algorithm implementing the above-described optimization method, and these adjustments s.sub.k are automatically fed to the power supplies of the coils. Of course, coils do not represent the sole possibility for carrying out the correction process in a remote-controlled automated fashion. E.g., the z-movement of the segments of the secondary magnet arrangement 13 can be accomplished via suitable mechanical drives and individual motors, which are controlled by a control unit 35 (FIGS. 1, 3a, 4, 6a), wherein control unit 35 is part of adjustment unit 30 and receives data (data descriptive of a thickness distribution) from a thickness measuring system (not shown); and control unit 35 may also carry out the computing tasks required for the optimization process.

(52) The external adjustability of the segmented secondary magnet arrangement is, of course, not limited to rectangular magnetrons, but can also applied to other magnetrons such as round (circular) magnetrons. Such a round magnetron is illustrated in FIGS. 8a and 8b.

(53) In case of such round magnetrons, the complete magnet system (primary magnet arrangement 1,2 and secondary magnet arrangement 13) is frequently kept, during operation, in a rotating movement around an axis 20 through the middle of the round target 3, so as to achieve a rotationally symmetric high erosion off the target and a high coating thickness uniformity in azimuthal direction on the substrates. An exemplary magnet configuration of such a magnetron is schematically shown in FIGS. 8a, 8b.

(54) Like in the case of a rectangular magnetron, a high plasma density forms above the target in a region describing a closed curve. Due to the rotation of the magnet system that high plasma density region continually rotates above the target surface and thus leads to a rotationally symmetric erosion of target material and to a corresponding deposition on a substrate above the target. The thickness distribution in radial direction, however, can show an undesired deviation from a desired target distribution (typically flat, i.e. maximum homogeneity). By means of shunts or permanent magnets which are adjustable with respect to their z-position (or with coils fed by adjustable power supplies), the erosion rate can be, in analogy to the methods discussed above for a rectangular magnetron, influenced or adjusted. Like in the case of the rectangular magnetron, the adjustment can be accomplished from the outside (from external to the process chamber), but for practical reasons, it will usually be preferred to stop the rotational movement for doing so. The interrelation between position of segment (or current flowing through coil) is, because of the rotational movement of the magnet system, more complicated, but, like in the case of the rectangular magnetron, a gauging is possible by specifically adjusting the adjustment states (i.e. the positions and/or currents) of the segments.

(55) We can summarize that a magnetron sputtering source is used which comprises a primary magnet arrangement having an inner part 1 and an outer part 2 and a secondary magnet arrangement 13, wherein a change or adjustment of the resulting magnetic field (field lines referenced as 17) above the target 4 is accomplished by shifting one or more (preferably all) segments of the secondary magnet arrangement relative to the primary magnet arrangement 1,2 towards the target 4 or away therefrom, i.e. along the z-axis (cf. FIG. 3). The resulting magnetic field above the target is weakened in case of segments closer to the target and strengthened in case of segments farther away from the target. Accordingly, the deposition rate will locally be lower and higher, respectively.

(56) A change in position of the segments of the secondary magnet arrangement 13 has direct influence on the form (shape) of the resulting magnetic field (more precisely: of the shape of the field lines 17 of the resulting magnetic field) and also on the local field strength. Since the segments are positioned such that they cause the flat shape of the field lines 17 above the target 4 needed for the improved target utilization, a small position shift in z direction of the segments changes the shape of the field lines 17 above the target 4 only slightly, such that the target utilization is, in a first approximation, hardly influenced. On the other hand, by means of said small position shift in z direction of the segments, the field strength (which is an absolute value) changes locally in a substantial way. As a consequence, the plasma density changes locally and, accordingly, the local ion density relevant for the sputtering process changes. The deposition rate on the substrate is thus influenced locally and changes locally the resulting coating thickness. Since the change of the plasma density takes place only locally, the voltage of the plasma discharge changes only insubstantially, and, accordingly, the average deposition rate across the magnetron sputtering source changes only insubstantially.

(57) The segments of the secondary magnet arrangement 13 are preferably moved by suitable mechanical means, which are accessible directly from the outside of the cathode, i.e. their position can be controlled from the outside while the vacuum chamber 10 remains closed (and vacuumized). This is facilitated if the segments are located outside the vacuum chamber 10.

(58) As an alternative for changing an adjustment state of a secondary magnet arrangement 13 or of a segment thereof, the use of coils and electromagnets, respectively, has been described. Of course, one can also combine z-movements of segments and adjustable currents flowing through coils of the segments.

(59) Of course, it is also possible to carry out the invention in case of stationary substrates, i.e. substrates that are, during at least most of their deposition time, substantially fixed in position with respect to the target 4. In this case, the thickness distributions will preferably be two-dimensional distributions (along x and y).

(60) The invention can allow to locally change thickness distributions (on a coated substrate) and deposition rate distributions (achievable with the target).

(61) Aspects of the embodiments have been described in terms of functional units such as control unit 35 and adjustment unit 30. As is readily understood, these functional units may be realized in virtually any number of hardware and/or software components adapted to performing the specified functions.

LIST OF REFERENCE SYMBOLS

(62) 1 first part of primary magnet arrangement 2 second part of primary magnet arrangement 3 back plate, ferromagnetic back plate 4 target, sputtering target 4 a target surface 5 region of high plasma density 6 substrate, workpiece 7 coating, film 8 gas inlet 9 power supply (for plasma discharge) 10 vacuum chamber, process chamber 11 target erosion trench, race track 12 magnetic field lines (of magnetron magnetic field) 13 secondary magnet arrangement 14 guidance for segment movement 15 unit for mechanical displacement 16 magnetic field lines (of auxiliary magnetic field) 17 magnetic field lines (of magnetic field of superposition) 18 micrometer screw, thread 19 mechanical guidance, guiding appliance 20 axis of rotation (of magnet system) 30 adjustment unit 35 control unit 40 target mount 50 direction of movement of substrate 60 substrate transport means A symmetry plane b (physical) width of segment L left region M1, . . . , M10, MX segments, magnets N north, north pole P1, . . . , P9 power supplies R right region S south, south pole S1, S2 shunts t thickness, coating thickness t change in thickness, change in coating thickness x, y, z coordinates w,w.sub.k intrinsic quantity, intrinsic width offset

Magnetron sputtering source and arrangement with adjustable secondary magnet arrangement

Assignee

Inventors

Cpc classification

Classification Explorer

H01J37/3455

ELECTRICITY

Classification Explorer

H01J37/3408

ELECTRICITY

Classification Explorer

H01J37/3402

ELECTRICITY

Classification Explorer

H01J37/3405

ELECTRICITY

International classification

Classification Explorer

C23C14/34

CHEMISTRY; METALLURGY

Classification Explorer

H01J37/34

ELECTRICITY

Abstract

Claims

Description