HK1162619B - Ring cathode for use in a magnetron sputtering device - Google Patents

Description

Annular cathode for magnetron sputtering device

Technical Field

The present invention generally relates to a magnetron sputtering apparatus for depositing a material onto a substrate having a low defect level, wherein a film deposited on the substrate has a predetermined thickness profile. More particularly, the present invention relates to an annular cathode for use in a magnetron sputtering apparatus and a magnetron sputtering apparatus incorporating the same.

Background

Sputter coating is a widely used technique for depositing thin films of materials on substrates. In a sputter deposition process, ions are typically generated by collisions between gas atoms and electrons in a glow discharge. The ions are accelerated by the electric field into the target of coating material at the cathode causing atoms of the target material to be ejected from the target surface. The substrate is placed in a position such that it intercepts a portion of the ejected atoms. Thus, a coating of target material is deposited on the surface of the substrate. In reactive sputtering, gaseous species are also present at the substrate surface and react with, and in some embodiments combine with, atoms from the target surface to form the desired coating material.

In operation, when a sputtering gas, such as argon, is introduced into the coating chamber, a Direct Current (DC) voltage applied between the cathode and anode ionizes the argon into a plasma, and the positively charged argon ions are attracted to the negatively charged cathode. The ions strike the target in front of the cathode using considerable energy and cause target atoms or clusters of atoms to be sputtered from the target. Some of the target particles strike and deposit on the wafer or substrate material to be coated, forming a film.

To obtain increased deposition rates and lower operating pressures, magnetically enhanced cathodes are used. In a planar magnetron, the cathode comprises an array of permanent magnets arranged in a closed loop and mounted in a fixed position relative to a flat target plate of coating material. Thus, the magnetic field causes electrons to travel in a closed loop, commonly referred to as a "race track," which establishes a path or region along which sputtering or erosion of the target material occurs. In a magnetron cathode, the magnetic field confines the glow discharge plasma and increases the path length of electrons moving under the influence of the electric field. This results in an increase in the probability of gas atom-electron collisions, resulting in a much higher sputtering rate than would be obtained without the use of magnetic confinement. Furthermore, the sputtering process can be achieved at much lower gas pressures.

Typically, magnetron sputtering systems are at 2 x 10^ during sputtering^-2Pa-1*10^^-1Pa. In order to build up this pressureThe chamber is typically pumped down to<1*10^^-4And a controlled gas stream, typically argon (and in the case of reactive sputtering argon and oxygen), is fed into the chamber to maintain the desired pressure. In the case of diode systems, i.e. when magnets are not used, it is necessary to be able to ignite and sustain a plasma>A pressure of 2 Pa. High pressures have the disadvantage that the mean free path is greatly reduced, which leads to a large range of gas diffusion. This results in a hazy coating.

It is desirable to create a magnetron sputtering system that can increase the coating rate from one substrate to another and from run to run and produce uniformity across the individual substrates.

The cathode geometry, in particular the relation between the cathode shape, position and size and the object to be coated, has a significant influence on the deposition rate and the area to be coated as well as on the product quality and consistency. The variation in layer thickness across the substrate is known as the runoff. The amount of fluid loss can be predicted by modeling. It is desirable to provide good film thickness uniformity and low loss on large diameter substrates.

In many coating installations, masking is used to reduce coating rate variation to acceptable levels. But over time, the mask typically accumulates a significant amount of coating material. Once the material on the mask reaches a critical thickness, it can flake off and contribute to particles that compromise the quality of the coating. Moreover, trimming and maintaining such masks is a delicate process. In addition, as the masks are coated, they gradually change their shape, which continuously changes the coating profile. In some cases, a substantial portion of the sputtered particles are shielded, which reduces material utilization. In the prior art, a heavy mask that blocks up to 40% of the coating material is required to achieve an acceptable thickness distribution (loss) of +/-1.5% across a 100mm wafer. A stable system is needed to provide uniformity from one operation to another. It is desirable to provide a device that does not use a mask.

The anode provides a different charge than the negatively charged cathode. This can be provided as simply as a charge provided to the chamber walls. However, sputtered material is also deposited on any surface exposed to the sputtered atoms. If the coating is an electrically insulating material, such as a metal oxide, the accumulation of material on other parts of the sputtering apparatus can cause problems. In particular, the accumulation of the insulating coating on the anode interferes with the ability of the anode to remove electrons from the plasma, as is required to maintain the charge balance of the plasma. This destabilizes the plasma and interferes with deposition control. Coating build-up will move the anode position to another surface in the system. This instability affects the coating quality. Many prior art anodes have been proposed to overcome the problem of coating the anode with a coating material. Many prior art anodes operate at very high voltages, which also increases arcing problems, compromising coating quality. A low voltage anode that can provide a stable anode position is important to ensure consistent coating quality.

Increased coating capacity can be achieved by an increase in deposition rate or an increase in load size or a combination of both. To increase the deposition rate, the power density at the target must be increased. However, higher power densities result in increased arc formation and, in some targets, such as silicon, in increased target cracking. Larger targets allow higher material removal rates without increasing power density. Greater oxidation efficiency of the deposited film may also increase the deposition rate of reactive sputtering. Maintaining the loss limit is a challenge to increase the load size. In a concentric system where the cathode and the planetary drive share a common center point, increasing the planetary drive system requires an increase in throw distance for a larger or larger number of substrates. This increases the problem of gas diffusion by increasing the probability of particle collisions, also known as "reduction in mean free path". The result is an increase in the surface roughness of the coating, which is understood to be an increase in diffusion or haze. It is desirable to increase throughput to greater than 3600cm2/hr for 3 micron thick applications while maintaining a loss of +/-0.5%. For some industries, the capacity to coat 300mm substrates is essential. It is desirable to increase capacity without sacrificing coating quality. It is also desirable to maintain a low temperature process despite increased power input in order to be able to process temperature sensitive materials.

Disclosure of Invention

It is an object of the present invention to provide an annular cathode for use in a magnetron sputter coating apparatus having a geometry that provides fast coating over a large surface area while maintaining high coating quality and minimizing material waste.

It is another object of the present invention to provide a magnetron sputter coating apparatus including a ring cathode geometry that produces a high quality coating without the use of a mask.

The invention aims to provide a magnetron sputtering coating device with a ring-shaped cathode in combination with a low-voltage anode container.

It is an object of the present invention to provide a ring cathode for use in a magnetron sputter coating apparatus, said ring cathode having an anode container at the centre of the cathode ring.

It is another object of the present invention to provide an annular cathode for use in a magnetron sputter coating apparatus, the annular cathode having a reactant gas outlet at the center of the cathode ring.

It is an object of the present invention to provide an annular cathode for use in a magnetron sputter coating apparatus, said annular cathode having an anode container at the center of a cathode ring which can transport active reaction gases.

The present invention provides an annular cathode geometry that increases the coating area and target material efficiency in a magnetron sputtering device having a planetary drive system, wherein the cathode axis is offset from the planetary drive. The annular cathode geometry and the eccentric dual rotation system of the substrate allow good coating uniformity across large substrates to be achieved without the use of masking. The low defect level is maintained by reducing the power density on the cathode.

Accordingly, the present invention provides a magnetron sputtering apparatus comprising:

a planetary drive system having a central axis of rotation C for the main rotation and supporting a plurality of planets each having a planet center point C_sAnd each planet represents a radius r of the planet_wThe described coating zone, planetary drive system, has a central axis of rotation C to a planetary center point C_sRadius r of the bracket_C；

A chamber for housing the cathode and the planetary drive system, adapted to be evacuated in operation;

a gas delivery system for providing a sputtering gas flow into the chamber;

a cathode including a target including a material for forming a plating layer;

wherein the cathode is an annular cathode, the target is an annular target, and the cathode has a center point Cc and an outer diameter r larger than the planet radius₂(r₂>r_W) And an inner diameter r greater than one quarter of the outer diameter₁(r₂>r₁>1/4*r₂)；

Wherein the center point C of the cathode_cIs arranged at an offset distance r from the central rotation axis C_TAt the offset distance r_TAt the radius r of the bracket_C2/3 and 4/3 (2/3 r)_C<r_T<4/3*r_C)；

And an offset distance r_TGreater than half the outer diameter (r) of the cathode_T>1/2*r₂)；

And wherein the throw h from the target surface perpendicularly to the planet surface is at the outer diameter r of the cathode₂Between one third and one time the outer diameter of the cathode (1/3 r)₂<h<r₂)。

A magnetron sputtering apparatus as described herein for providing a sputtered coating to a substrate without the use of a mask.

The magnetron sputtering apparatus as described herein, further comprising a reactive source for the reactive gas.

The magnetron sputtering apparatus as described above, wherein the active source for the reaction gas is located at the center of the annular cathode.

A magnetron sputtering apparatus as described herein, further comprising an anode for providing a voltage differential to the cathode such that the anode is the preferred return path for electrons, the anode comprising an inner conductive surface of the container, the container having an insulated outer surface electrically isolated from the chamber wall, the container having an opening communicating with the interior of the chamber, the opening being substantially smaller than the circumference of the container to shield the inner conductive surface from most sputtered material.

The magnetron sputtering apparatus as described herein, wherein a sputtering gas source is coupled into the container for providing sputtering gas into the chamber through the opening, and the opening is sized to allow the gas flow to locally increase the pressure within the anode container above the pressure of the evacuated chamber.

The magnetron sputtering apparatus as described herein also includes a reactive source for the reactive gas.

Magnetron sputtering apparatus as described herein, wherein the anode includes a source for sputtering gas, the anode being positioned such that the opening of the vessel communicating with the chamber interior is at the center of the annular cathode.

A magnetron sputtering apparatus as described herein includes an active source for the reactant gases, wherein the anode is positioned such that the opening of the vessel communicating with the chamber interior is at the center of the annular cathode.

The magnetron sputtering apparatus according to the present application includes an anode as a source of a sputtering gas, wherein an active source for a reaction gas is located at the center of an annular cathode.

Magnetron sputtering apparatus as described herein, comprising an anode as a source of sputtering gas, wherein the anode further comprises a source for a reactive gas coupled into the vessel for providing a reactive gas and sputtering gas into the chamber through the opening.

The magnetron sputtering apparatus according to the present application includes an anode as a source of a sputtering gas and a reaction gas, wherein an opening into a chamber of a container including the anode is located at a center of an annular cathode. A magnetron sputtering apparatus includes a cathode as a source of a sputtering gas and an active gas at the center of an annular cathode, and an auxiliary active reaction source at a distance from the cathode. Magnetron sputtering apparatus, wherein the inner diameter r₁Greater than the outer diameter r₂Is one half of (a), such that r₂>r₁>1/2*r₂。

Magnetron sputtering apparatus as described herein, wherein the inner diameter r₁Greater than the outer diameter r₂0.70 of (a), so that r₂>r₁>0.70*r₂。

The magnetron sputtering device according to the present application, wherein 0.95 r₂>r1>0.6*r₂。

Magnetron sputtering apparatus as described herein, wherein the cathode radius r₂Equal to or greater than 1.11 times the planet radius (r2)>1.11*r_W)。

A magnetron sputtering apparatus as described herein, wherein the cathode includes inner and outer concentric rings of permanent magnet material on opposite sides of the target material of the cathode, the inner and outer concentric rings having opposite polarities for providing a magnetic field proximate to the surface of the target, the axes of the inner and outer concentric rings being perpendicular to the surface of the target.

The magnetron sputtering apparatus as described herein further includes one or more alternating annular cathodes within the chamber that include an annular target comprising a material for forming a coating, wherein the offset distance r_TGreater than the outer diameter r₂One time (r) of_T>1*r₂)。

The magnetron sputtering apparatus as described herein further includes means for adjusting the throw distance between the target surface plane and the object plane.

Advantageously, the present invention increases coating uniformity in loss and planet-to-planet results over the prior art. The tolerance to mechanical deviations in vertical and horizontal positioning is significantly relaxed. Thus, a significant planet-to-planet uniformity improvement can be achieved due to the tight mechanical control. This quality control can be maintained over relatively large substrates (300mm) while maintaining a relatively short throw distance despite the proportional increase in increased load. According to the present invention, this uniformity can be achieved without using a mask.

Drawings

Exemplary embodiments of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is an isometric view of a coating system of the present invention with portions of the outer wall removed;

FIG. 2A is a schematic cross-sectional view of a ring cathode incorporating an anode container with respect to a planetary substrate to be coated, the ring cathode including a source of active reactant gas at its center;

FIG. 2B is a schematic top view of the cathode and anode with the active reactant gas source of FIG. 2A relative to a planetary substrate to be coated;

FIG. 2C is a schematic top view of a cathode and anode with separate radially positioned sources of active reactant gas;

FIG. 3A is a schematic top view of an annular cathode target and a planetary substrate according to an embodiment of the invention;

FIG. 3B is a schematic side view of the annular cathode target and the planetary substrate drive;

FIG. 4A is a top view of an annular cathode;

FIG. 4B is a cross section of the ring cathode taken along line IV-IV of FIG. 4A, showing the target material, the magnet, and the magnetic field lines;

FIG. 5 is a cross-section of an anode container used in a magnetron sputtering apparatus;

FIG. 6 is a plot of calculated loss versus the variable inside diameter to outside diameter ratio of the annular cathode;

FIG. 7A is a plot of calculated loss and height versus relative tray radius and cathode position;

FIG. 7B is a plot of calculated number of substrates versus relative carrier radius and cathode position;

FIG. 8A is a graph of calculated loss versus normalized bracket radius r_C/r_TThe relationship curve of (1);

FIG. 8B is a calculated throw distance versus normalized carrier radius r_C/r_TThe relationship curve of (1);

FIG. 9A is for the cathode ring size r₁/r₂Calculated loss and relative substrate dimension r_W/r₂The relationship curve of (1);

FIG. 9B is a calculated normalized throw distance h/r₂And the relative substrate size r_W/r₂The relationship curve of (1);

the calculated fluid loss versus relative planetary size r of FIG. 10A_W/r₂The relationship curve of (1);

FIG. 10B is the calculated relative throw distance h/r₂And relative planetary size r_W/r₂The relationship curve of (1);

fig. 11 is a measured loss profile for a device constructed in accordance with the present invention.

Detailed Description

FIG. 1 shows an isometric view of a coating chamber 2 of a magnetron sputter coating apparatus 10. The pump 8 evacuates the coating chamber 2 so that the coating chamber 2 operates under vacuum conditions, which is understood to mean a pressure in which the pressure is below atmospheric pressure. The chamber wall 32 is grounded and connected to the positively charged anode 20Isolated from the negatively charged cathode 12. The planetary drive 14, seen in more detail in fig. 3A and 3B, comprises a carrier 16 or carrier rotatable about a central axis of rotation C about which a plurality (e.g. 7 or 8) of planets 17 are radially supported. Radius of the bracket r_CIs defined between the central axis C and the planet axis Cs. Shown are annular cathodes 12 (two cathodes 12 in this embodiment), each having a central axis Cc offset from the central axis C of the planetary drive 14. The anode 20 (the anode 20 being in the form of a container having an opening communicating with the coating chamber 2) is shielded from coating material and from direct access to the target material of the cathode 12 in a straight line. A source of active reactant gas 36 is shown at the center of cathode 12. These positions can be reversed into the following form: 36 includes an anode at the center of cathode 12 and 20 is an active reaction source disposed at a distance from cathode 12. Although the preferred location of the active source 36 is at a radial position r from C_CAs seen in fig. 2C. Fig. 2A and 2B show an alternative embodiment in which an anode container 20' is located at the center of the annular cathode 12, also serving as a reactant gas source. If the anode 20' is a source of active reactant gas (36 in FIG. 1) at the center of the cathode, a supplemental source of active oxygen gas may be located at 20 in FIG. 1 to achieve a higher deposition rate. The magnetron sputtering coating device 10 includes a load lock 1 for loading or unloading a substrate or other object 23 for coating. This allows the coating chamber 2 to be kept under vacuum conditions at all times. The apparatus is depicted here in an upward sputtering configuration. However, the geometry of the present invention is equally applicable to a downward sputtering, horizontal or other orientation.

Pulsed DC magnetron sputtering is the preferred process. Alternatively, the invention can also be implemented in DC magnetron, AC magnetron sputtering and rf magnetron sputtering.

Many optical coatings have distinguishable characteristics in their spectral response. For example, edge filters for color separation pass one color while rejecting other colors. For the purposes of this disclosure, the accuracy requirement for the coating is assumed to be 0.5% across a 200mm or 300mm substrate. For the above example, if the edge is at 500nm, this will translate to an absolute edge position change of 2.5 nm. The location of the spectral feature is related to the thickness of the layer in the coating design. Therefore, the variation in the plating rate over the entire substrate needs to be below 0.5%. If multiple substrates are coated in the same batch, the change from one substrate to another needs to be a fraction of that value. The change in the position of the spectral feature is also referred to as the loss.

The planetary drive 14 and the annular cathode 12 are schematically shown in more detail in fig. 3A and 3B. The planetary drive 14 comprises a central axis C about which the transmission rotates and a plurality of secondary axes Cs about which each planet 17 rotates independently. The distance between the central axis C and the secondary axis Cs is the radius r of the carrier_C. Each planet 17 has a radius r_WThe radius r_WThe maximum available coating area is defined. The size of the planetary drive 14 and the capacity of the device 10 are determined by the number and size of planets 17 required.

The planets 17 in the planetary coating geometry are supported at a common distance r from the central axis of rotation C_CTo (3). It is generally desirable to arrange the planets 17 as closely as possible for optimal use of the coating material. Each planet 17 may support a single or multiple substrates, optical prisms, lenses, or other objects 23. The object 23 to be coated may comprise a plurality of smaller separate parts mounted on a support substrate. Radius of the planet r_wBut merely to define the available coating area for each planet 17. The planet 17 itself need not be of this size in construction, but need to be able to support a substrate 23 of this radius, or a plurality of objects 23 coated in this region. In a preferred embodiment, a large object (e.g., a large optical device) may have a thickness of up to 32 mm. With controlled height adjustment, a well-defined target surface to object surface distance results in minimal loss.

The independent planetary rotations may include coordinated rotation rates relative to rotation about the central rotation axis C. The secondary axis Cs is preferably parallel to the central rotational axis C, but may be at some other angle. Each planet 17 is arranged to experience substantially the same conditions as each other planet 17. As best seen in fig. 3B, the object plane 46 is shown at the coating surface of the substrate or other object 23. The throw h between the object plane 46 and the target surface plane 44 of the cathode 12 is measured.

The annular cathode 12 has a radius r greater than the planet radius_WLarge radius r of₂. According to the size and number of planets to be coated, the radius r of the cathode₂Can be optimized to maintain the desired amount of fluid loss. One other factor is the loop width. The cathode has an inner diameter r₁. The narrower the ring, i.e. r₁/r₂The larger the support or substrate 17 may be to achieve the same uniformity. A larger cathode radius requires a lower power density to achieve a high deposition rate despite the high total power in the cathode 12. This minimizes charge build-up on the target 24 and the resulting arc formation. Central axis C of cathode 12_cIs translated by an offset distance r from the central axis C_T. The translation or offset distance r_TEqual to the radius r of the bracket_C2/3 and 4/3. Most preferably the offset is equal to the bracket radius r_C(rT＝r_C) While a similar loss control is achieved in the range of 0.7 to 1.3 times the radius of the carrier. These values are a function of the cathode ring width r₁/r₂And the determined loss limit, as can be seen in fig. 8A. The offset distance varies depending on the size or number of substrates to be coated.

The cathode 12 has an inner diameter r measured at the erosion zone of the target₁And outer diameter r₂This is clearly shown in fig. 4B. Together, these radii define a preferably narrow ring. The cathode 12 and target 24 of the coating material both have substantially the same annular shape and size. The inner diameter may be as long as 0.98 r₂And should be at least 0.25 ar₂. And at 0.55 ar₂Improved results are seen. For a 300mm substrate, r of 0.70 or more is used₁/r₂The narrow cathode ring of (a) achieves the optimum amount of loss. Outer diameter r₂Depending on the radius r of the planet 17_W. Radius r₂Greater than the planet radius (r)₂>r_W) To arrangeDesirably 2 times the radius of the planet 17. The radius of the cathode can be larger than r₂>2*r_WAlthough this depends on the space constraints in the chamber. When comparing rings of equal width (e.g. r)₂-r₁) The larger radius (r2) ring cathode results in better coating uniformity. This can be seen in fig. 6. It is important to note that a single large target does not necessarily result in good uniformity. Simulations show that a round (non-circular) highly utilized cathode results in poor uniformity. The simulated data are shown in fig. 6. The performance of the geometry of the present invention is predicted by numerical modeling. Simulations of this geometry show that for a given target and substrate size (outer diameter), the narrower the raceway ring, the better the coating uniformity across the substrate, and for the inner diameter r₁Up to about 0.98 r₂Practical limitations of (c). It was further observed that a larger diameter ring cathode resulted in better coating uniformity when comparing rings of equal width. FIG. 6 shows the dimension r for a substrate_W/r₂Radius loss versus relative ring radius r1/r2 is 0.69. As the loop narrows, the curve clearly shows a reduced amount of fluid loss. At r₁/r₂>Less than 2% loss was seen at 0.25. Paired rings r₁/r₂>0.55, a better loss is predicted. The ideal range occurs at 0.9>r₁/r₂>Between 0.55. On opposite axes, throw distance h is dependent on relative ring radius r₁/r₂Are drawn. From r₁/r₂0.25 to r₁/r₂The throw h from the target plane 44 to the object plane 46 increases from 90mm to 240mm, 0.9.

As shown in fig. 4A and 4B, the large ring-shaped cathode 12 includes an inner magnetic ring 35 and an outer magnetic ring 37. The annular target may be described as having an inner race track radius and an outer race track radius. The racetrack of the magnetron cathode describes the area where the material is ejected. The main contributor to this mode is the horizontal magnetic field strength in front of the target 24. The magnetic field is generated by permanent magnets 35, 37 in two concentric rings beneath the target. The inner magnetic ring 35 has a magnetic flux density substantially equal to or less than r₁And outer magnetic ring 37 has a radius substantially equal to or greater than r₂Of (c) is used. The two magnetic rings 35, 37 have opposite polarity with their axes perpendicular to the surface 44 of the target 24. Due to the relatively narrow ring, it is possible to achieve a high magnetic field, which results in a low target voltage (between-250V and-650V) and generally reduces the stress in the deposited layer. In a large ring cathode, there is sufficient space inside the ring to include additional magnets to optimize the magnetic field shape for better target utilization. Any electrical mode (e.g., RF, DC, pulsed DC, MF, double cathode-AC, single cathode AC) can be used to drive the cathode.

The geometry according to the invention allows the coating apparatus to be scaled up for larger capacities without a large increase in throw distance. This helps to maintain coating quality while increasing capacity. FIGS. 7A and 8A graphically illustrate the relationship between carrier radius r_CThe effect on surface uniformity. FIG. 7B shows the bracket radius r_CThe number of planets, and thus the number of substrates, may be increased. FIG. 8 graphically illustrates the variation with bracket radius r_CIncrease in distance, optimal throw distance. In FIG. 7, a constant r of the cathode is used₂The radius is calculated. In FIGS. 8A and 8B, a fixed target location r is used_TPerforming a calculation wherein r_C＝r_TIs normalized. As can be seen from the graph in fig. 8A, in order to increase the load size or substrate dimension, deviation from this optimum position can be tolerated without a large influence on the amount of flow loss. The curves in FIG. 8B show that for different target ring sizes r₁/r₂The required increase in throw distance h of (a), wherein the pair r is also used_CThe rT normalized fixation target position is calculated. The throw distance affects the coating rate and the efficiency of use of the target material. It also has a significant effect on the coating quality. The greater the target-to-substrate distance, the higher the probability that sputtered atoms will diffuse into the remaining working gas (argon and oxygen). This diffusion results in a reduction in the energy and a change in direction of the sputtered particles. Both mechanisms have a negative impact on the coating quality, resulting in rough coatings and, in the case of dielectric films, haze and light scattering. The lower throw distance h in the present invention is important to improve coating capacity and improve the quality of the larger coating capacity.

The graph in FIG. 9A shows the planet dimension r_WThe effect on uniformity. It can be seen that the narrower the cathode ring, r1/r2 being 0.90, the larger the planets can be to achieve the same uniformity. For 2% loss:

for r₁/r₂>＝0.48，r_w<0.67*r₂Or for r₁/r₂>＝0.48，r₂>1.50*rw

For r₁/r₂>＝0.55，r_w<0.69*r₂Or for r₁/r₂>＝0.55，r₂>1.45*rw

For r₁/r₂>＝0.76，r_w<0.80*r₂Or for r₁/r₂>＝0.76，r₂>1.25*rw

For r₁/r₂>＝0.90，r_w<0.90*r₂Or for r₁/r₂>＝0.90，r₂>1.11*rw

For a loss of 5%:

for r₁/r₂>＝0.48，r_w<0.50*r₂Or for r₁/r₂>＝0.48，r₂>2.00*r_w

For r₁/r₂>＝0.55，r_w<0.52*r₂Or for r₁/r₂>＝0.55，r₂>1.92*r_w

For r₁/r₂>＝0.76，r_w<0.58*r₂Or for r₁/r₂>＝0.76，r₂>1.72*r_w

For r₁/r₂>＝0.90，r_w<0.65*r₂Or for r₁/r₂>＝0.90，r₂>1.54*r_w

Similarly, FIG. 10A shows different inner diameters r for the target 24 and cathode 12₁Uniformity varies with planet size. Narrowest ring (largest r)₁) Again resulting in the lowest amount of fluid loss. FIG. 10B shows a relatively flat throw versus cathode radius (r)₂) The ratio of (a) to (b) relative to the relative planet size.

Comprising seven radii r of 150mm_WAnd has an outer diameter r of 290mm₂Is constructed in accordance with an example of this geometry of the annular cathode. Radius r of inner cathode₁Is 220mm, r1/r2 equals 0.76. Radius of the bracket r_CEqual to the offset distance r at 400mm_T. FIG. 11 shows data for the prototype, which shows the relative amount of flow loss for different throw distances h, relative to the total 300mm substrate (r)_W+150 mm). A throw distance of 210mm shows the best loss results.

In a preferred embodiment, as shown in FIG. 1, two cathodes 12 are included in coating chamber 2, coating chamber 2 having different targets 24 to provide different materials for the multilayer coating. Each cathode 12 is operated independently, while the vacant cathodes may be shielded to avoid contamination. Target 24 (not shown) may be, for example, to form SiO₂And silicon to form Ta₂O₅The tantalum target of (1). For mounting two cathodes 12 in one chamber 2, the offset distance r_TMust be larger than the outer diameter r of the cathode₂. Because the design is to offset r_TIs relatively insensitive in that additional and different target materials can be provided in this way without sacrificing coating quality. Relationship r of each cathode 12 to the planetary drive 14_TAre the same. Thus, multiple cathodes may be arranged in the chamber to provide additional material or reduce run time. The number of cathodes will be determined in part by considerations of cross-contamination between different targets, the space available in the coating chamber 2 and the additional pump cost for larger chambers.

The position of the cathode 12 can be adjusted to vary the throw distance by moving the mounting platform of the cathode 12 or the rotary drive 14 or both. This can be done manually or by starting the motor. Such adjustments may also be made to improve the geometry for different materials, or to maintain distance as the target erodes from use. The conditioning may be performed using a process chamber under vacuum. The height adjustment mechanism in the planetary drive mounting or cathode mounting allows for throw compensation for different substrate or object thicknesses. In operation, the height adjustment can provide continuous compensation for target erosion to maintain the correct throw distance h throughout the coating cycle.

For a standard layer thickness of about 100nm, the rotation speed of the planets 17 should be higher than 300 rpm. In the case of very thin layers (around 10nm), higher planetary rotation speeds (>600rpm) are required to result in good fluid loss. This assumes that the planetary drive 14 rotates at 40-80 rpm.

Anode 20 provides a different charge than the negatively charged cathode. A preferred anode 20 shown in detail in fig. 5 for use in the present invention is disclosed in related application US SN11/074,249 filed on 7/3/2005, owned by the assignee of the present invention and incorporated herein by reference. Referring now to fig. 5, there is shown an anode 20 in the form of a container or vessel having an inner conductive surface 22 of copper or stainless steel, the container having an opening 21 at a first end for communicating with the vacuum chamber 2, the opening 21 being directly coupled to the vacuum chamber 2. The outer surface 26 of the container 20 is electrically insulating. In the cross-sectional view, a water cooling tube 28 is shown substantially around the anode 20 for maintaining the temperature of the anode in operation. A gas inlet 29 is shown for providing a conduit into which sputtering gas can enter the anode vessel. The size of the opening 21 and the flow rate of the sputtering gas may be selected to locally pressurize the anode 20. The anode body 20 may be disposed outside or inside the vacuum coating chamber 2. Furthermore, the opening 21 may be located on the side or end of the anode container. The relatively small (significantly smaller than the container circumference) opening 21 and the out-of-sight opening 21 to the target location prevent coating material from entering and coating the inner conductive surface of the anode container. In operation, anode 20 is pressurized with argon gas, which promotes plasma formation in coating chamber 2 in the presence of a suitable ignition voltage and subsequent maintenance voltage. The higher pressure within vessel 20 than the rest of vacuum coating chamber 2 allows for a lower anode voltage and more stable sputtering conditions. A positive power lead 25 connects the power source to the inner conductive wall 22 of the anode 20. The anode shown in fig. 5 is designed to operate with a low anode voltage with little or no arcing. A low anode voltage of about +15 to +60 volts is preferred to reduce process variation. Anode 20 is electrically insulated from grounded chamber wall 32 by insulating material 33.

In a preferred embodiment, the anode comprises a cylindrical container having a diameter of at least d-10 cm and a length of at least h-20 cm, with an opening 21 to the vacuum chamber 2 at one end and closed at the opposite end as shown in fig. 5. For low diffusion processes, the chamber pressure is below 0.267Pa (2 mTorr.). The higher pressure at the anode is achieved by the narrow opening 21 of the anode 20 and the controlled flow of working gas into the anode 20 via the inlet 29. The optimum opening has about 20cm²And is preferably circular. In operation, anode 20 may be pressurized to greater than 0.400Pa (3 mTorr.). This anode 20 can be operated in nearly continuous operation for an extended period of time. The anode vessel 20 may conveniently be located in a chamber wall 32 adjacent the cathode 12, as shown in fig. 1, and also serves as a source of sputtering gas.

The anode container 20 may be incorporated into the center of the ring cathode as shown in fig. 2 because the anode opening is relatively far from the strong magnetic field. This improves the symmetry of the system, which improves target utilization.

Many optical coatings require the deposition of oxides or other compounds. Such materials are preferably produced in a reactive sputtering mode in which a metal target is sputtered and oxygen, nitrogen or another reactive gas is added to the process. The sputtered material and the reactive oxygen species reach the substrate simultaneously. For example, for an optimal oxygen partial pressure, an optimal oxygen flow rate needs to be found. If the oxygen flux is too low, the membrane is not stoichiometric and has high absorption losses. If it is too high, the target surface becomes more oxidized than necessary, preventing operation at the highest possible deposition rate. The sputtering rate of the metal target can be 10 times higher than that of a fully oxidized target. In its basic form, the reactant gases flow through mass flow controllers and enter the coating chamber through simple gas lines or complex manifolds. If oxygen is activated and directed at the substrate, the oxidation efficiency may increase, thus increasing the possible deposition rate.

In a preferred embodiment of this aspect of the invention, the output of the inductively coupled reactive source 36 is located at the center of the annular cathode 12. Experiments have shown that a higher deposition rate of metal oxides with low absorption can be achieved when the plume of sputtered material from the target and the plume of activated and ionized oxygen overlap and reach the substrate to be coated at the same time. Therefore, a reactive gas source 36 in the center of the target is an almost ideal solution. The use of the directional oxygen activation or acceleration device 36 described in fig. 1 aids in the formation of stoichiometric films while minimizing target oxidation. Such means may be an inductively or capacitively coupled plasma source with or without an extraction or acceleration system. The source output may be an ionized or otherwise activated oxygen species (e.g., atomic oxygen, ozone). Examples include JDSU PAS sources, Taurion sources from Pro Vac, APS sources from Loybold, or other commercially available ion or active sources. The source of reactive oxygen gas 36 is located just at the target surface plane 44 in the center of the cathode 12. If the active reactive source is separate from the cathode, it should be oriented so that cathode 12 is between oxygen source 36 and object plane 46 that is outside the line of sight from sputter target surface 24, since it is important to prevent substantial coating build-up at oxygen source 36. As shown in FIG. 2C, the oxygen source 36 may be mounted at a radius r from C_CAnd its opening is inclined towards the target plane 24 and the planet 17. The opening should be at a vertical distance greater than or equal to h from the object plane 46. The distance h is preferred. Moving the target surface plane 44 closer to the object plane 46, as achieved by the present geometry, allows the oxygen reactive source 36 to be positioned closer to the substrate 23 while keeping it free of substantial coating build-up. This increases the oxidation efficiency and allows plating at a higher rate. Reactive sputtering processes for oxides are disclosed. All aspects may be similarlyApplied to nitride or other reaction processes.

In another preferred embodiment, anode container 20 is found to be a suitable structure for providing reactive reactant gases. We observe that the anode container 20 comprises a plasma in its general arrangement. The plasma is ignited by high density electrons from the cathode 12 and returned to the power supply through the anode 20. The effect of ion generation and generation of active species is similar to the reaction occurring at the cathode: high energy e- + Ar ≥ 2e- + Ar + or high energy e- + Ar ═>e- + Ar. Without this activation of the argon atoms, these would not be a visible plasma at the anode. If we decided to test the addition of oxygen to the anode to test if it would produce active and ionized oxygen. By coupling an oxygen feed into the anode vessel 20', we were able to deposit SiO free of impurities₂A single layer. This is a clear indication that anodes operating with argon and oxygen appear to be the anode and the source of the active reactant gas. Furthermore, we did not observe oxidation of the inner wall of the anode. This configuration is shown in fig. 2A. When the anode and oxidizing source are separated, large variations in target wear are observed, which limits target utilization. On the side close to the oxidation source, the target wear is low due to the increase in target oxidation, while on the side close to the anode, the target wear is high due to the increase in plasma density. By including the anode 20 in the center of the cathode 12, one asymmetric source is eliminated. By including the oxygen source in the center of the cathode 12 along with the anode vessel 20', a very symmetrical system is created and target wear is expected to be uniform. In addition to achieving higher deposition rates, an auxiliary active reaction source (e.g., at 20 shown in FIG. 1) located at a distance from cathode 12 may be provided.

Claims (20)

1. A magnetron sputtering apparatus comprising:

a planetary drive system having a central axis of rotation C for the main rotation and supporting a plurality of planets each having a planet center point C_sAnd each planet has a radius r defined by the planet radius_wThe described coating zone, the planetary drive system having a central axis of rotation C to each of the planetary center points C_sRadius r of the bracket_C；

A chamber for housing the cathode and the planetary drive system, adapted to be evacuated in operation;

a gas delivery system for providing a flow of sputtering gas into the chamber; and

a cathode including a target including a material for forming a plating layer;

characterized in that the cathode is an annular cathode, the target is an annular target, and the cathode has a cathode center point C_cGreater than the planet radius r_WOuter diameter r of cathode₂，r₂>r_WAnd at the cathode outer diameter r₂And the outer diameter r of the cathode₂Of one time of the cathode inner diameter r₁So that 1/4 r₂<r₁<r₂；

Wherein the cathode center point C_cIs arranged at an offset distance r from the central rotation axis C_TAt the offset distance r_TAt the radius r of the bracket_C2/3 and the bracket radius r_C4/3, so that 2/3 r_C<r_T<4/3*r_C；

And the offset distance r_TIs larger than the outer diameter r of the cathode₂So that r is_T>1/2*r₂；

And wherein the vertical throw h from the target surface to the planet surface is at the cathode outer diameter r₂One third of and the cathode outer diameter r₂Between one time of (c), so that 1/3 r₂<h<r₂。

2. The magnetron sputtering apparatus of claim 1 for providing a sputtered coating to a substrate without using a mask.

3. The magnetron sputtering device of claim 2, further comprising a source of reactive gas.

4. The magnetron sputtering device of claim 3, wherein the source of active reactant gas is located in the center of the annular cathode.

5. The magnetron sputtering apparatus of claim 2, further comprising an anode for providing a voltage differential to the cathode such that the anode is a preferred return path for electrons, the anode comprising a conductive inner surface of a container having an insulated outer surface electrically isolated from a chamber wall of the chamber, the container having an opening communicating with the chamber interior of the chamber, the opening having a circumference substantially smaller than a circumference of the container to shield the conductive inner surface from most sputtered material.

6. The magnetron sputtering apparatus of claim 5, wherein the gas delivery system comprises a sputtering gas source coupled into the container for providing the flow of sputtering gas into the chamber through the opening of the container, and wherein the opening of the container is sized to allow the flow of sputtering gas to locally increase the pressure within the container above the pressure of the evacuated chamber.

7. The magnetron sputtering device of claim 6, wherein the cathode is positioned such that an opening of the container communicating with the chamber interior is at a center of the annular cathode.

8. The magnetron sputtering apparatus of claim 6, wherein the gas delivery system further comprises a reactive gas source coupled into the container for providing a flow of reactive gas and a flow of the sputtering gas into the chamber through the opening of the container.

9. The magnetron sputtering device of claim 8, wherein the anode is positioned such that the opening of the container communicating with the chamber interior is located at the center of the annular cathode.

10. The magnetron sputtering apparatus of claim 9 further comprising a secondary source of reactive gas spaced from the cathode.

11. The magnetron sputtering device of claim 6, further comprising a source of reactive gas.

12. The magnetron sputtering device of claim 11, wherein the anode is positioned such that an opening of the container communicating with the chamber interior is at a center of the annular cathode.

13. The magnetron sputtering device of claim 11, wherein the source of active reactant gas is located in the center of the annular cathode.

14. The magnetron sputtering device of claim 1, wherein the cathode inner diameter r₁At the outer diameter r of the cathode₂One half of (d) and the cathode outer diameter r₂Between one time of (c), so that 1/2 r₂<r₁<r₂。

15. The magnetron sputtering device of claim 1, wherein the cathode inner diameter r₁At the outer diameter r₂0.70 times of the cathode outer diameter r₂Between one time of (c), so that 0.70 r₂<r₁<r₂。

16. The magnetron sputtering device of claim 1, wherein the cathode inner diameter r₁At the outer diameter r of the cathode₂0.6 times of the cathode outer diameter r₂Between 0.95 times, so that 0.6 r₂<r₁<0.95*r₂。

17. The magnetron sputtering device of claim 1, wherein the cathode outer diameter r₂Equal to or greater than the planet radius r_W1.11 times of so that r₂≥1.11*r_W。

18. The magnetron sputtering device of claim 1, wherein the cathode further comprises inner and outer concentric rings of permanent magnet material on the cathode on opposite sides of the target for providing a magnetic field proximate to the surface of the target, the inner and outer concentric rings having opposite polarities, the axes of the inner and outer concentric rings being perpendicular to the surface of the target.

19. The magnetron sputtering device of claim 1, further comprising one or more additional ring cathodes within the chamber, each of the ring cathodes comprising a ring target comprising a material for forming a plating layer, wherein the offset distance r of each of the ring cathodes_TIs larger than the outer diameter r of the cathode₂Is one time higher than r_T>1*r₂。

20. The magnetron sputtering device of claim 1, further comprising means for adjusting the vertical throw distance h.