Sputtering apparatus and process for high rate coatings

A magnetron system for eroding and depositing target materials on a substrate, comprising:

• a first and a second cylindrical tubular target, each having a longitudinal axis and an outside surface and a fixed length, the first target composed of a material and the second target composed of a material that are different from each other, each tubular target rotatable about the longitudinal axis of the cylindrical target, wherein the second rotatable cylindrical tubular target is positioned relative to the first target such that axes of the first and second targets are parallel to each other and the surfaces of the first and second cylindrical tubular targets are in close proximity;
• a first and a second magnetic assembly respectively disposed within and along the length of the first and the second tubular target,
• each magnetic assembly configured to provide a magnetic field racetrack over an outer surface of each tubular target, the magnetic field racetrack confining a plasma gas to erode the material of each target from a pair of substantially parallel erosion zones along the length of the each tubular target, each pair of erosion zones defining a source plane for each target and being separated by a distance therebetween,
• each magnetic assembly configured to fix the distance between the erosion zones in each target to combine the flux from each zone so as to create an area at the substrate of substantially uniform target flux for each tubular target,
• wherein a greater fraction of the target flux from each target is utilized to deposit target material on the substrate than from a single erosion zone on each target;
• and
• a baffle disposed between the tubular targets and separating the areas of target flux from each target at the substrate such that the substrate receives first target material to form a first layer on the substrate and then receives second target material to form a second layer over the first layer on the substrate as the substrate is moved past the area of target flux from each target.

A method of operating a sputtering process to deposit material from a pair of targets onto a stationary substrate to achieve a given coating stoichiometry, the method comprising the steps of:

• introducing a flow of sputtering gas into an evacuated chamber in which the substrate and target material reside;
• introducing a flow of reactive gas into the evacuated chamber to cause the deposition of a combination of the target material and the reactive gas onto the substrate, the sputtering gas and reactive gas being pumped into the chamber at a specified speed;
• connecting each target material to a voltage source that provides a voltage to cause sputtering gas ions to erode each target material;
• forming an intense magnetic field over each target material to confine the sputtering gas ions over a pair of substantially parallel erosion zones on each target material, target material from the erosion zones combining to create an area of substantially uniform target material flux at the substrate,
• maintaining the sputtering gas flow, the voltage and the pumping speed approximately constant;
• and
• scanning the magnetic field synchronously over each target material to sweep the target material flux from each target across the substrate.

A magnetron for eroding a target and depositing target material onto a substrate, comprising:

• a cylindrical tubular target having a longitudinal axis, an inside surface and outside surface and a fixed length, the inside and outside surfaces having a certain inner and outer circumference, respectively, said target being rotatable about said longitudinal axis, said tubular target including
• a target material supporting assembly having:
• a target support tube;
• a cylindrical target backing tube for holding the tubular target material;
• first and second target backing tube supports, one at each end of the cylindrical target backing tube, the first tube support for holding the target backing tube in place over and coaxial with the target support tube, a cylindrical chamber being formed by the target backing tube and the target backing tube supports;
• and
• means for receiving rotational drive to rotate target material supporting assembly;
• and
• a magnetic assembly, disposed within and along the length the cylindrical tubular target, configured to provide a magnetic field racetrack over the outside surface of the tubular target, the magnetic field racetrack confining a plasma gas to erode the target material from a pair of substantially parallel erosion zones extending along the length of the tubular target, said assembly being configured to fix the distance between the erosion zones to create an area of substantially uniform target material flux at the substrate, wherein a greater fraction of the target flux is utilized to deposit target material uniformly on the substrate than with a single erosion zone.

A magnetron for eroding a target and depositing target material onto a substrate, comprising:

• a cylindrical tubular target having a longitudinal axis, an inside surface and outside surface and a fixed length, the inside and outside surfaces having a certain inner and outer circumference, respectively, said target being rotatable about said longitudinal axis;
• a magnetic assembly, disposed within and along the length the cylindrical tubular target, configured to provide a magnetic field racetrack over the outside surface of the tubular target, the magnetic field racetrack confining a plasma gas to erode the target material from a pair of substantially parallel erosion zones extending along the length of the tubular target, said assembly being configured to fix the distance between the erosion zones to create an area of substantially uniform target material flux at the substrate, wherein a greater fraction of the target flux is utilized to deposit target material uniformly on the substrate than with a single erosion zone, said magnetic assembly including
• a backing plate constructed from a magnetic alloy;
• a semi-circular non-magnetic housing having a curved portion fitted within a portion of the inner circumference of the tubular target, resting on and sealed to the backing plate and defining a plurality of magnet cavities between the housing and the backing plate, a plurality of cooling cavities formed between the inside surface of the tubular target and the curved portion of the housing;
• a plurality of magnets disposed within the cavities for creating the magnetic field over the target material;
• and
• a dark space shield having a tubular shape and fitted over the tubular targets, a gap of a fixed size existing between the shield and the tubular target, the shield having an opening for exposing the tubular target to the plasma gas to define the erosion zone of the tubular target subject to erosion by the plasma gas.

A sputtering module for depositing a target material on a substrate, comprising;

• a sputtering enclosure;
• a vacuum system mounted on the enclosure for evacuating gases from the sputtering enclosure;
• a pair of cylindrical magnetrons disposed proximate and parallel one to the other within the enclosure, each magnetron including:
• a cylindrical tubular target having a longitudinal axis and an outside surface and a fixed length, rotatable about the longitudinal axis of the cylindrical target;
• and
• a magnetic assembly disposed within and along the length of the cylindrical tubular target, the magnetic assembly configured to provide a magnetic field racetrack over an outer surface of the tubular target, the magnetic field racetrack confining a plasma gas to erode the target material from a pair of substantially parallel erosion zones along the length of the tubular target, each pair of erosion zones defining a source plane for each target and being separated by a distance therebetween, and the magnetic assembly configured to fix the distance between the erosion zones to create an area of substantially uniform target material flux at the substrate, wherein a greater fraction of the target flux is utilized to deposit target material uniformly on the substrate than with a single zone;
• wherein the magnetic assemblies are oriented relative to each other such that, at the substrate, an included angle is formed between a pair of planes, normal to the source planes and passing through the axis of each target, and the target flux of each of the targets combines to create a wider area of uniform flux at the substrate than from each target separately;
• and
• wherein each magnetron has an electrode so that an electric field can be established between the magnetrons to enable the plasma gas of a certain density to form;
• rotation means for imparting to each of the tubular targets a speed of rotation with respect to the magnetic assemblies so that a substantial fraction of the outside surface is caused to pass by the magnetic assemblies in a single rotation, wherein the speed of rotation and the density of the plasma gas in the erosion zones are such as to substantially prevent accumulation of target material on regions of the target away from the sputtering zones during a rotation of the tubular target;
• and
• an alternating current electrical power supply having a first and second pole that alternate in polarity, the first pole being connected to the electrode of one of the magnetrons and the second pole being connected to the electrode of the other of the magnetrons, and the alternating current electrical power supply being operated at a preselected constant voltage, wherein each magnetron alternately deposits target material on the substrate as the poles alternate in polarity.

A magnetron assembly comprising:

• a tubular target having an inner and outer surface;
• a target supporting assembly for supporting the tubular target, the target support assembly including:
• means for receiving rotation from an external drive source;
• a first and second tubular target support for holding the tubular target, the first tubular target support fastened to one opening of the tubular target and the second tubular target support fastened to the other opening;
• a target support tube that connects the rotation receiving means to the first tubular target support;
• a first and second set of sealing static O-rings for sealing the first and second tubular target supports, respectively, against the tubular target;
• and
• a set of bearings disposed in an annular ring between the rotation receiving means and the target tube support tube to permit rotation therebetween;
• a mounting assembly for securing the target supporting assembly for rotation, the mounting assembly including:
• insulated mounting flange having a bore and fastened to a stationary support plane;
• a rotary vacuum feedthrough having a bore and disposed within the bore of the mounting flange, the bore of the rotary vacuum feedthrough receiving the target support tube, the first tubular target support positioned against one opening of the feedthrough bore and the rotation receiving means positioned near the other opening of the feedthrough bore;
• a set of static O-rings for sealing the feedthrough against the mounting flange;
• a set of O-ring seals for sealing the feedthrough against the target support tube disposed within the feedthrough bore;
• a first and second set of bearings disposed with a first and second annular rings, respectively, between the rotary vacuum feedthrough and the target support tube for rotation therebetween;
• and
• an insulating alignment flange for receiving, within a cylindrical pocket in the flange and supporting for rotation, the second tubular target support, the insulating alignment flange having a set of bearings disposed within the annular ring between the flange pocket and the lower tubular target support;
• a magnet assembly disposed within the tubular target and along its length, the magnet assembly for providing magnetic field over the tubular target defining an erosion zone of the tubular target and having a passage through which a cooling fluid flows to cool the assembly;
• a stationary assembly including:
• secondary support tube disposed within the target support tube and concentrically within the tubular target and along the length of the tubular target;
• an electrical commutator connected to the secondary support tube and making electrical contact with the rotation receiving means;
• at least two magnet assembly support clamps fastened about the secondary support tube to support the magnet assembly in proximity to the inner surface of the tubular target;
• and
• a first and second set of bearings disposed in first and second annular gaps between the secondary support tube and the first and second target supports, respectively, to permit rotation of the first and second target supports relative to the secondary support tube;
• and
• a cooling assembly including:
• a cooling tube disposed within and along the length of the secondary support tube, the cooling tube connected to the cooling passage in the magnet assembly to convey cooling fluid through the magnet assembly and near the erosion zone of the tubular target;
• and
• a fluid input and output port for injecting cool fluid and extracting the heated fluid from the cooling tube.

A method of operating a sputtering process to deposit target material onto a moving substrate to achieve a given coating stoichiometry, the method comprising the steps of:

• introducing a flow of a sputtering gas into an evacuated chamber in which the substrate and target material reside;
• introducing a flow of reactive gas into the evacuated chamber to cause the deposition of a combination of the target material and the reactive gas onto the substrate;
• connecting the target material to a voltage source that provides a voltage to cause sputtering gas ions to erode the target material, said voltage source maintaining an electric current in the sputtering gas ions;
• forming an intense magnetic field over the target material to confine the sputtering gas ions over a pair of substantially parallel erosion zones on the target material, the target material from the erosion zones combining to create an area of substantially uniform target material flux at the substrate;
• maintaining the sputtering gas flow and the voltage approximately constant;
• and
• controlling the reactive gas flow with a feedback loop to maintain the electric current approximately constant and to compensate for coating variations caused by the variations in pumping speed due to the moving substrate.

A method of operating a sputtering process to alternately deposit layers from first material and second material from first and second targets, respectively, onto a stationary substrate, the method comprising the steps of:

• introducing a flow of sputtering gas into an evacuated chamber in which the substrate and first and second target material reside, the sputtering gas being pumped into the chamber at a specified speed;
• connecting the first and second target each to a voltage source that provides a voltage to cause sputtering gas ions to erode the target material, the voltage source alternately activating each target to alternately deposit layers from first and second material onto the substrate;
• forming an intense magnetic field over the first target material to confine the sputtering gas ions over a pair of substantially parallel erosion zones on the first target material;
• forming an intense magnetic field over the second target material to confine the sputtering gas ions over a pair of substantially parallel erosion zones on the second target material, the erosion zones on each target material combining to create an area of substantially uniform target material flux at the substrate;
• maintaining the sputtering gas flow, the voltage and the pumping speed approximately constant;
• and
• scanning separately each magnetic field over the target that is activated to sweep the target material flux across the substrate and alternately deposit layers from the first and second target material onto the substrate.