Method of ionized physical vapor desposition sputter coating high aspect-ratio structures

A sputtering apparatus includes a chamber for containing a feed gas. An anode is positioned inside the chamber. A cathode assembly comprising target material is positioned adjacent to an anode inside the chamber. A magnet is positioned adjacent to cathode assembly. A platen that supports a substrate is positioned adjacent to the cathode assembly. An output of the power supply is electrically connected to the cathode assembly. The power supply generates a plurality of voltage pulse trains comprising at least a first and a second voltage pulse train. The first voltage pulse train generates a first discharge from the feed gas that causes sputtering of a first layer of target material having properties that are determined by at least one of a peak amplitude, a rise time, and a duration of pulses in the first voltage pulse train. The second voltage pulse train generates a second discharge from the feed gas that causes sputtering of a second layer of target material having properties that are determined by at least one of a peak amplitude, a rise time, and a duration of pulses in the second voltage pulse train.

BACKGROUND OF INVENTION

Physical Vapor Deposition (PVD) is a plasma process that is commonly used in the manufacturing of many products, such as semiconductors, flat panel displays, and optical devices. Physical vapor deposition causes ions in a plasma to dislodge or sputter material from a target. The dislodged or sputtered target material is then deposited on a surface of a workpiece to form a thin film.

Independently controlling the uniformity of the sputtered film and the density of the plasma generated during PVD becomes more difficult as the size of the workpiece increases. In magnetron sputtering, large targets are typically required to sputter coat large workpieces. However, processing large workpieces can result in problems, such as poor target utilization, target cooling problems, and non-uniform coating of the workpieces.

Complex rotating magnet configurations have been used to improve plasma uniformity and to prevent non-uniform erosion of the target. In some systems, workpieces are moved relative to the plasma in order to increase the uniformity of the sputtered film. However, moving the magnets and/or the workpieces can result in a lower deposition rate. In other systems, the power applied to the target is increased to increase the deposition rate. However, increasing the power applied to the target can result in undesirable target heating. Compensating for temperature increases associated with increasing the power applied to the target by cooling the target in the deposition system increases the cost and complexity of the deposition system.

DETAILED DESCRIPTION

The present invention relates to plasma systems having multiple or segmented magnetron cathodes instead of one single magnetron cathode. A plasma generated by a plasma system having a segmented magnetron cathode design according to the present invention creates a more uniform coating on a substrate at given level of plasma density than a plasma that is generated by a known plasma system having a single magnetron cathode geometry. The uniformity of a thin film generated with a plasma system having multiple magnetron cathode segments is relatively high because each of the multiple magnetron cathode segments can independently control a film thickness in a small localized area of the workpiece in order to generate a more uniform coating on the entire workpiece. Increasing the number of magnetron cathode segments increases the control over the coating thickness. The sputtered material generated by the segmented magnetron cathode can also be directed to different locations in the chamber depending on the geometry of the segmented magnetron cathode.

FIG. 1illustrates a diagram of a plasma source100including a segmented magnetron cathode102according to one embodiment of the invention. The segmented magnetron cathode102is located within a chamber101that confines a feed gas. The segmented magnetron cathode102includes a plurality of magnetron cathode segments. In some embodiments, the magnetron cathode segments are separate magnetrons. The segmented magnetron cathode102according to the present invention can be embodied as many different geometries. For example, the segmented magnetron cathode102of the present invention can include magnetron cathode segments that all have equal surface area. Alternatively, the segmented magnetron cathode of the present invention can include magnetron cathode segments that have different surface areas. The magnetic field associated with the segmented magnetron cathode can have any geometry and any strength depending upon the particular application. In addition, the segmented magnetron cathode can include a water cooling system (not shown) to control the temperature of the sputtering target.

The segmented magnetron cathode102includes a first102a, a second102b, and a third102cmagnetron cathode segment. The segmented magnetron cathode102can also include a fourth magnetron cathode segment102d. Additional magnetron cathode segments can be added as necessary depending on the specific plasma process, the size of the workpiece to be processed, and/or the desired uniformity of the coating. The magnetron cathode segments102a-dare typically electrically isolated from each other. In one embodiment, the segmented magnetron cathode102includes target material for sputtering. The target material can be integrated into or fixed onto each magnetron cathode segment102a-d.

The plasma source100also includes at least one anode that is positioned proximate to the plurality of magnetron cathode segments102a,102b, and102cin the chamber101. In one embodiment, the plasma source100includes a plurality of anode sections104a,104b. The plurality of anode sections104a,104bare positioned adjacent to the magnetron cathode segments102a,102b, and102c. An additional anode section104cis positioned adjacent to the optional fourth magnetron cathode segment102d. In one embodiment, the anode sections104a,104b, and104care coupled to ground105. In other embodiments, the anode sections104a,104b,104care coupled to a positive terminal of a power supply. Additional anodes and magnetron cathode segments can be added to form a larger plasma source for processing large workpieces, such as 300 mm wafers, architectural workpieces, and flat panel displays.

An input106of the first magnetron cathode segment102ais coupled to a first output108of a switch110. An input112of the second magnetron cathode segment102bis coupled to a second output114of the switch110. An input116of the third magnetron cathode segment102cis coupled to a third output118of the switch110. An input120of the optional fourth magnetron cathode segment102dis coupled to a fourth output122of the switch110. The switch110can be any type of electrical or mechanical switch that has the required response time, voltage capacity, and current capacity. In one embodiment, the switch110is programmable via a computer or processor. The switch110can include one or more insulated gate bipolar transistors (IGBTs). In some embodiments (not shown), at least one output108,114,118,122of the switch110can be coupled to more than one magnetron cathode segment102a-din the segmented magnetron cathode102. The switch110can be configured to apply one or more voltage pulses to each of the magnetron cathode segments102a-din a predetermined sequence. This allows a single pulsed DC power supply to apply independent voltage pulses to each magnetron cathode segment102a-d.

An input124of the switch110is coupled to a first output126of a power supply128. A second output130of the power supply128is coupled to ground105. The power supply128can be a pulsed power supply, a switched DC power supply, an alternating current (AC) power supply, or a radio-frequency (RF) power supply. In one embodiment, the power supply128generates a train of voltage pulses that are routed by the switch110to the magnetron cathode segments102a-d. The switch110can include a controller that controls the sequence of the individual voltage pulses in the train of voltage pulses that are routed to the magnetron cathode segments102a-d. Alternatively, an external controller (not shown) can be coupled between the power supply128and the switch110to control the sequence of the voltage pulses in the train of voltage pulses that are routed to the magnetron cathode segments102a-d. In some embodiments, the controller is a processor or a computer.

In one embodiment, the plasma source100is scalable to process large workpieces. In this embodiment, the power supply128is a single high-power pulsed direct current (DC) power supply. The single high-power pulsed DC power supply generates a high-density plasma with a power level between about 5 kW and 1,000 kW during each pulse. In one embodiment, the single pulsed DC power supply generates a high-density plasma with a power level that is between about 50 kW and 1,000 kW during each pulse depending on the surface area of each magnetron cathode segment102a-dof the segmented magnetron cathode102. The power level is chosen based on the surface area of the particular magnetron cathode segment102a-dto achieve a specific result. Thus, a power supply that generates a moderate amount of power during the pulse can be used in a plasma source100according to the present invention to generate the high-density plasma.

A power supply that generates a moderate amount of power during the pulse can be used in the plasma source100to generate a high-density plasma. A pulsed power supply having an extremely high-power output would be required in some systems in order to generate a comparable power density on a single magnetron cathode. However, the duty cycle of the pulsed power supply used in the plasma source100is typically higher than the duty cycle for a power supply used for a single magnetron cathode in order to maintain the same average power.

The magnetron size of the segmented magnetron of the present invention can be scaled up while maintaining the same power density as a small magnetron. This is achieved by segmenting the magnetron into a plurality of magnetron segments. The duty cycle of the pulsed power supply is increased in order to apply the same average power. This approach allows the segmented magnetron cathode102to operate with a moderate power level and a moderate current level. The segmented magnetron cathode102can use the same pulsed power supply128for a small or a large area magnetron in order to generate the same plasma density during the pulse, although the duty cycle is changed in order to maintain the same average power.

For example, if the magnetron has an area S1, and the power applied during the pulse is P1, then the power density can be expressed as P1/S. Assuming that the power supply has duty cycle of about ten percent, then the average power that is applied to the magnetron is about 0.1P1. If another magnetron has an area 4S1, then in order to keep the same power density and average power, the power supply applies a power of 4P1during the pulse at the same duty cycle. In the case of a segmented magnetron cathode that consists of four magnetron cathode segments each with area S1, the same power P1can be applied to each of the four magnetron segments. In order to apply the same average power to the segmented magnetron, the duty cycle of the power supply is increased from ten percent to forty percent. In this case, the switch can route pulses to the different magnetron segments to provide the same power density and average power. The size of the magnetron can be increased until the duty cycle of the power supply reaches almost one hundred percent. At that point, the power level during the pulse is increased and a compromise is made between modifying the pulse power level and the duty cycle.

The number of magnetron cathode segments102a-d, the duty cycle, and the maximum power of the pulsed power supply128can be chosen for a particular application. For example, a smaller number of magnetron cathode segments102a-din the segmented magnetron cathode102can require a high-power pulsed power supply having a low duty cycle while a larger number of magnetron cathode segments102a-dcan require a lower-power pulsed power supply having a higher duty cycle in order to generate a similar power density and average power.

In one embodiment, the pulse width of the voltage pulses generated by the power supply128is between about 50 microseconds and 10 seconds. The duty cycle of the voltage pulses generated by the power supply128can be anywhere between a few percent and ninety-nine percent. In one embodiment, the duty cycle is about twenty percent. The duty cycle of the power supply128depends on the number of magnetron cathode segments102a-din the segmented magnetron cathode102and the time required for the switch110to operate. The repetition rate of the voltage pulses generated by the power supply128can be between about 4 Hz and 1000 Hz. In one embodiment, the repetition rate of the voltage pulses is at about 200 Hz. Thus, for a pulse width of 1,000 μsec, the time period between pulses for a repetition rate of 200 Hz is approximately 4,020 μsec. The switch110redirects the voltage pulses to the various magnetron cathode segments102a-dduring the time period between pulses.

The average power generated by the power supply128is between about 5 kW and 100 kW. However, the peak power generated by the power supply can be much greater. For example, the peak power is about 330 kW for a plasma having a discharge current of 600 A that is generated with voltage pulses having a magnitude of 550V. The power supply128generates an average power of about 20 kW for voltage pulses having a pulse width of 1,000 μsec and a repetition rate of 200 Hz.

The power supply128can vary the rise time of the voltage pulse, the magnitude, the pulse duration, the fall time, the frequency, and the pulse shape of the voltage pulses depending on the desired parameters of the plasma. The term “pulse shape” is defined herein to mean the actual shape of the pulse, which can be a complex shape that includes multiple rise times, fall times, and peaks. A pulse train generated by the power supply128can include voltage pulses with different voltage levels and/or different pulse widths. The switch110can route one or more of the voltage pulses to each of the magnetron cathode segments102a-din a predetermined sequence depending on several factors, such as the size of the segmented magnetron cathode102, the number of magnetron cathode segments102a-d, and the desired uniformity of the coating and density of the plasma. Each individual voltage pulse in the train of voltage pulses can have a different shape including different pulse widths, number of rise times and/or different amplitudes. The particular rise times and/or amplitudes of the voltage pulses can be selected to achieve a desired result, such as a desired sputtered metal ion density and/or a desired uniformity of a coating.

The segmented magnetron cathode102reduces cathode heating because voltage pulses are independently applied to each of the magnetron cathode segments102a-d. Thus, when a voltage pulse is applied to one of the magnetron cathode segments102a-d, the heat previously generated on the other magnetron cathode segments102a-ddissipates. Therefore, the segmented magnetron cathode102can operate with relatively high peak plasma densities by permitting higher voltage pulses to be applied to each of the magnetron cathode segments102a-d. Thus, the segmented magnetron cathode102can operate with relatively high overall power applied to the plasma without overheating the individual magnetron cathode segments102a-d. In some embodiments, the uniformity of the thin film deposited by the segmented magnetron cathode can be optimized by adjusting the shape, frequency, duration, and sequence of the voltage pulses for the various magnetron cathode segments.

FIG. 2Aillustrates a cross-sectional view of the plasma source100including the segmented magnetron cathode102ofFIG. 1. The plasma source100includes at least one magnet assembly134apositioned adjacent to the first magnetron cathode segment102a. Additional magnet assemblies134b,134c,134dare positioned adjacent to the other respective magnetron cathode segments102b,102c,102d. The magnet assembly134acreates a magnetic field136aproximate to the first magnetron cathode segment102a. The magnetic field136atraps electrons in the plasma proximate to the first magnetron cathode segment102a. Additional magnetic fields136b,136c, and136dtrap electrons in the plasma proximate to the their respective magnetron cathode segments102b-d. The strength of each magnetic field136a-dgenerated by each magnet assembly134a-dcan vary depending on the desired properties of the coating, such as the desired coating uniformity.

One or more of the magnetic assemblies134a-dcan generate unbalanced magnetic fields. The term “unbalanced magnetic field” is defined herein as a magnetic field that includes non-terminating magnetic field lines. For example, unbalanced magnetic fields can be generated by magnets having different pole strengths. Unbalanced magnetic fields can increase the ionization rate of atoms sputtered from the segmented magnetron cathode102in an ionized physical vapor deposition (I-PVD) process. The unbalanced magnetic field can also increase the ion density of the ionized sputtered atoms. In one embodiment, the sputtered atoms are metal atoms and the unbalanced magnetic field increases the ionization rate of the sputtered metal atoms to create a high density of metal ions.

A first138a, a second138b, and a third plurality of feed gas injectors138ccan be positioned to inject feed gas between the corresponding cathode segments102a-dand anode sections104a-c. Each of the plurality of feed gas injectors138a-ccan be positioned to inject feed gas so that a desired uniformly is achieved around the circumference of each respective magnetron cathode segment102a-d.

The pluralities of feed gas injectors138a-care coupled to one or more gas sources139through gas valves140a-c. The gas source139can include non-reactive gases, reactive gases, or a mixture of non-reactive and reactive gases. The gas valves140a-ccan precisely meter feed gas to each of the pluralities of feed gas injectors138a-cin a controlled sequence. In one embodiment, the gas valves140a-ccan pulse feed gas to the each of the pluralities of feed gas injectors138a-c. In one embodiment, an excited atom source (not shown) supplies excited atoms through the feed gas injectors138a-c.

A substrate141or workpiece is positioned adjacent to the segmented magnetron cathode102. The potential of the substrate141can be at a floating potential, can be biased to a predetermined DC or RF potential, or can be coupled to ground. In one embodiment, the substrate141is coupled to a DC or a radio-frequency (RF) power supply142. In one embodiment, the substrate141is positioned on a platen or holder (also shown as141) that provides a linear movement relative to the magnetron. A linear motion in the range of 0.1 cm/sec and 100 cm/sec can be used to improve uniformity. Also, in one embodiment, the substrate141is positioned on a platen or holder that is rotated around an axis near the center of the magnetron. Rotating the substrate141can also improve the film uniformity. In one embodiment, the platen or substrate141is rotated with speed that is in the range of 0.001 revolution per second to 100 revolutions per second. In one embodiment, the substrate141is positioned on a platen or holder that provides both rotation and a linear motion.

The plasma source100can be used to sputter deposit a coating on the substrate141. In this embodiment, each of the magnetron cathode segments102a-dincludes target material. The power supply128generates the train of voltage pulses and the switch110routes the individual voltage pulses in the train of voltage pulses to the various magnetron cathode segments102a-din a predetermined sequence. The target material from each of the magnetron cathode segments102a-dsputter coats the substrate141to generate coatings that are represented by thickness profiles144a-dthat correspond to the thickness of the coating material that is deposited by each of the cathode segments102a-d.

In some embodiments, a plurality of plasma sources is used that include at least two magnetrons. The at least two magnetrons can include cathodes with different target materials. For example, one magnetron can include Ti target material and the other magnetron can include W target material. Each plasma source can include a separate power supply128that generates a unique voltage pulse train. The duration of each voltage pulse train and particular voltage pulse shape in the trains can be optimized in order to sputter combinations of different films, such as combinations of TiN and WN.

In one embodiment, an optional ring-shaped pre-ionizing electrode145is positioned proximate to the segmented magnetron cathode102. The pre-ionizing electrode145is coupled to an output of a power supply146. Another output of the power supply146is coupled to ground105. For example, the power supply146can be a RF power supply, a DC power supply, a pulsed power supply, or an AC power supply. A grounded electrode147is positioned proximate to the pre-ionizing electrode145so that the power supply146can generate a plasma discharge between the grounded electrode147and the pre-ionizing electrode145.

The discharge can ignite a feed gas to create a weakly-ionized plasma proximate to the segmented magnetron cathode102. The discharge can also create an additional amount of electrons inside the chamber without igniting the discharge such as by emitting electrons under high temperature due to electrical current flowing through pre-ionizing electrode. The additional electrons can reduce the ignition voltage from the pulsed power supply that is required to create a weakly-ionized plasma. The properties of the discharge depend on the design of the magnetic field and the position of the pre-ionizing electrode. Generating a weakly-ionized plasma using a pre-ionizing electrode is described in co-pending U.S. patent application Ser. No. 10/065,629, entitled Methods and Apparatus for Generating High-Density Plasma, which is assigned to the present assignee. The entire disclosure of U.S. patent application Ser. No. 10/065,629 is incorporated herein by reference.

The rise time, the amplitude, the pulse duration, the fall time, and the pulse shape of each voltage pulse in the train of voltage pulses generated by the power supply128as well as the sequence with which the voltage pulses are routed by the switch110can be adjusted to improve the homogeneity of the thickness profiles144a-d, thereby improving the coating uniformity144across the substrate141. Also, selecting the parameters of the voltage pulses can increase the amount of sputtered material arriving on the substrate in the form of ions. The amount of sputtered material arriving on the substrate can be adjusted independently from an adjustment of the coating uniformity. In one embodiment, modifying the rise time of the voltage pulse can be used to adjust the amount of sputtered metal ions and modifying the pulse duration can be used to control the film uniformity. A highly uniform coating generated by ions of sputtered material can substantially fill high-aspect ratio contacts, trenches, and vias, for example. Therefore, the plasma source100can be used for ionized physical vapor deposition (I-PVD). Also, since the deposition rate and the plasma density from each magnetron cathode segment102a-dcan be adjusted independently, a coating can be uniformly deposited across the entire surface of the substrate141. In one embodiment, the segmented magnetron cathode102including the target material is about the same size as the substrate141. Reducing the size of the magnetron cathode reduces the overall size of the plasma source100and the overall cost of the system.

The switch110can also route the voltage pulses to the various magnetron cathode segments102a-dto create particular thickness profiles across the surface of the substrate141. For example, a particular thickness profile can include a film that is thinner in the center of the substrate141than on the outer edge of the substrate141.

The plasma source100can also be used to uniformly etch the substrate141. The plasma generated by the segmented magnetron cathode102can be highly uniform across the surface of the substrate141. The plasma source100can also be used for ionized physical vapor deposition (I-PVD), reactive sputtering, compound sputtering, reactive ion etch (RIE), ion beam processing, or any other plasma process.

The plasma source100can be used to generate a high-density plasma for I-PVD processing. For example, the plasma source100can be used to generate a high-density plasma for I-PVD of copper ions in order to efficiently sputter coat high-aspect ratio structures on the substrate141with or without using a RF bias on the substrate141. The high-density plasma generated by the segmented magnetron cathode102sputters copper atoms from a copper target. The copper atoms collide with electrons in the high-density plasma creating a multitude of copper ions.

The plasma generates a so-called “dark space” between the edge of the plasma and the surface of an electrically floating substrate141. The high-density plasma generated by the segmented magnetron cathode102has a high electron temperature which creates a negative bias on the substrate104. The negative bias attracts the copper ions and accelerates the copper ions through the dark space towards the substrate141. An electric field develops between the positively charged plasma and the negatively charged substrate141. The copper ions are accelerated along electric field lines and uniformly sputter coat the high-aspect-ratio structures on the substrate141. A RF bias can be applied to the substrate141to further improve the uniformity of the coating process or to sputter coat high-aspect-ratio features.

FIG. 2Billustrates a cross-sectional view of a plasma source150including the segmented magnetron cathode102ofFIG. 1having an alternative magnet assembly152. The magnet assembly152includes at least one magnet152athat is positioned adjacent to the first magnetron cathode segment102a. Additional magnets152b-eare positioned adjacent to each respective anode section104a-d. In one embodiment, the magnets152a-ehave magnetic field strengths that result in an unbalanced magnetic field. Generating an unbalanced magnetic field can increase the density of the plasma proximate to a substrate (not shown inFIG. 2B) and thus increase the rate of ionization of metal atoms and the density of metal ions in an I-PVD process.

The magnet152acreates a magnetic field154aproximate to the first magnetron cathode segment102a. The magnetic field154atraps electrons in the plasma proximate to the first magnetron cathode segment102a. Additional magnetic fields154b-dtrap electrons in the plasma proximate to the other respective magnetron cathode segments102b-d. The strength of each magnetic field154a-dgenerated by each magnet152a-dcan vary depending on the desired properties of the coating, such as the desired coating uniformity at the desired plasma density level.

The first output126of the power supply128is coupled to the input124of the switch110. The first output108of the switch110is coupled to the first magnetron cathode segment102a. The second output114of the switch110is coupled to the second magnetron cathode segment102b. The third output118of the switch110is coupled to the third magnetron cathode segment102c. The fourth output122of the switch110is coupled to the fourth magnetron cathode segment102d.

The second output130of the power supply128and the anode sections104a-dare coupled to ground105. In other embodiments, the second output130of the power supply128is coupled to the anodes104a-dand the anodes104a-dare biased at a positive voltage.

Magnetic coupling of the magnetron cathode segments102a-dis achieved by positioning the magnets152a-ebetween the magnetron cathode segments102a-d. The magnetic coupling can expand the plasma across the surface of the segmented magnetron cathode102as described below. The power supply128generates a train of voltage pulses at the first output126. The switch110directs the individual voltage pulses to the various magnetron cathode segments102a-din a predetermined sequence. One of the voltage pulses is applied to the first magnetron cathode segment102ain order to ignite a plasma proximate to the first magnetron cathode segment102a. In other embodiments, the voltage pulse can be applied to one of the other magnetron cathode segments102b-din order to ignite the plasma proximate to that magnetron cathode segment102b-d.

Electrons156in the plasma are trapped by the magnetic field154a. The trapped electrons156migrate toward the poles of the magnets152aand152balong magnetic field lines. Some of the electrons156that migrate towards the magnet152bare reflected into the magnetic field154bproximate to the second magnetron cathode segment102b. The migrating reflected electrons158expand the plasma proximate to the second magnetron cathode segment102b. As the plasma develops proximate to the other magnetron cathode segments102b-d, the electrons in the plasma migrate along magnetic field lines of the various magnetic fields154b-d. The electron migration that is caused by the magnetic coupling assists in creating additional plasma coupling across the surface of the segmented magnetron cathode102. This can reduce the voltage level required to ignite a weakly-ionized plasma for a particular magnetron cathode segment102a-d.

In one embodiment, an excited atom source170, such as a metastable atom source is positioned to supply excited atoms172including metastable atoms proximate to the segmented magnetron cathode102. The excited atoms172generated by the excited atom source170can increase the number of sputtered metal ions as well as the number of non-metal ions in the plasma and improve the uniformity of a coating generated by the plasma. For example, the energy of a metastable Argon atom (Ar*) is about 11 eV and the ionization energy for a copper atom (Cu) is about 7.7 eV. In a reaction described by Ar*+Cu=Ar+Cu++e, Cu ions are created that can increase the density and improve the uniformity of the Cu ions that are distributed near the substrate. The excited atoms172can also improve the process of igniting the plasma and can increase the density of the plasma. Generating a plasma using excited atoms, such as metastable atoms, is described in co-pending U.S. patent application Ser. No. 10/249,844, entitled High-Density Plasma Source Using Excited Atoms, which is assigned to the present assignee. The entire disclosure of U.S. patent application Ser. No. 10/249,844 is incorporated herein by reference.

FIG. 2Cillustrates a cross-sectional view of a plasma source175that includes the segmented magnetron cathode102ofFIG. 1with a magnet assembly176having an unbalanced magnet configuration that generates an unbalanced magnetic field. In this embodiment, the magnet176ahas a pole strength that is different than another cooperating magnet176b. In this example, the pole strength of the magnet176ais greater than the pole strength of the magnet176b. In an unbalanced magnetron, the magnets176a,176bof the magnet assembly176create some closed magnetic field lines178that form an electron trap that confines the plasma proximate to the surface of the magnetron cathode section102a. In addition, the magnets176a,176bof the magnet assembly176also create magnetic field lines180that project away from the magnetron cathode section102a. The magnetic field lines180are referred to as open field lines and can extend away from the magnetron cathode section102aand proximate to the substrate182to be coated. Other magnets176b-dcan generate balanced magnetic fields184b-cor unbalanced magnetic fields (not shown) proximate to the other magnetron cathode segments102b-c.

An unbalanced segmented magnetron according to the invention can increase the density of the plasma proximate to the substrate182to be coated. The increase in the density of the plasma is caused by electrons that are accelerated along the open magnetic field lines180towards the substrate182. The electrons ionize atoms in the vicinity of the substrate182. Additionally, some electrons that are accelerated along the open magnetic field lines180can charge the substrate182and create a bias on the substrate182. In one embodiment, a power supply186negatively biases the substrate182which accelerates ions in the plasma towards the substrate182.

The unbalanced segmented magnetron175can increase the ionization rate and the density of metal ions in an ionized physical vapor deposition (I-PVD) process. In one embodiment, the segmented magnetron cathode102includes copper target material. The copper target material is sputtered by ions in the plasma that bombard the segmented magnetron cathode102. Copper atoms moving towards the substrate182can interact with the plasma that is located near the surface of the segmented magnetron cathode102. Some of the copper atoms are ionized by electrons in the plasma. Maximizing the number of copper ions moving towards the substrate182is desirable in a I-PVD process. Other copper atoms that are not ionized pass through the plasma and are deposited on the substrate182and on the walls of the chamber (not shown).

An unbalanced magnetic field having open magnetic field lines180can increase the rate of ionization of metal ions and can increase the density of metal ions compared with a balanced magnetic field184bhaving closed magnetic field lines. Referring toFIG. 2C, copper atoms sputtered from the magnetron cathode segment102bpass through a volume188of plasma that is trapped by the balanced magnetic field184b. Electrons in the plasma ionize some of the copper atoms passing through the plasma.

A volume189of plasma generated proximate to the first segmented magnetron cathode102ais significantly larger than the volume188of plasma generated proximate to the second segmented magnetron cathode102b. The open magnetic field lines180in the unbalanced magnetic field allow the plasma to expand towards the substrate182. Copper atoms sputtered from the first magnetron cathode segment102apass through the volume189of plasma and are more likely to collide with an electron in the plasma and become ionized than copper atoms passing through the smaller volume188of plasma. Thus, the density of copper ions as well as the rate of ionization of copper atoms increases in an unbalanced magnetron compared to a balanced magnetron. An increased density of metal ions can improve an I-PVD process as previously discussed. An aluminum target can be used in the I-PVD process instead of a copper target. Also, many other metals, compounds, or alloys can be used in an I-PVD process according to the invention.

FIG. 2Dillustrates a cross-sectional view of a plasma source190that includes a segmented magnetron cathode102that can be used for reactive sputtering. The segmented magnetron cathode102includes three magnetron cathode segments102a-c. The magnetron cathode segments102a-ccan each include target material. The target material can be the same on each of the magnetron cathode segments102a-c. In a compound sputtering process, there can be different target material included on each of the magnetron cathode segments102a-c. The switch110includes a plurality of outputs that are coupled to the magnetron cathode segments102a-c. An output126of the power supply128is coupled to an input124of the switch110. The segmented magnetron cathode102also includes a magnet assembly152. The magnet assembly152includes a plurality of magnets152a-dthat generate magnetic fields154a-cproximate to the magnetron cathode segments102a-c. The magnetic fields154a-ccan be balanced or unbalanced.

The plasma source190also includes a plurality of anode sections191a-c. The anode sections191a-care shaped to deliver feed gas from the gas source139across the surface of each magnetron cathode segment102a-c. The gas source139can include ground state gas atoms, excited gas atoms, or a combination of ground state atoms and excited atoms. In one embodiment, an excited atom source (not shown) is positioned between the gas source139and the chamber192. The gas source139delivers ground state gas atoms to the excited atom source. The excited atom source raises the energy of the ground state atoms to create excited atoms and then the excited atoms are delivered to the chamber192.

The shape of each of the anode sections191a-ccan be chosen to increase a rate of ionization of the feed gas by modifying the pressure of the feed gas entering the chamber192. In some embodiments (not shown), the anode sections191a-cinclude internal gas injectors that supply the feed gas directly into the gap between each specific anode section191a-cand the corresponding magnetron cathode segment102a-c. The gas injectors can each supply different gases and/or excited atoms depending on the specific plasma process.

A reactive gas source193supplies reactive gas through a plurality of gas injectors194. The reactive gas can include oxygen, nitrogen, nitrous oxide, carbon dioxide, chlorine, fluorine, or any other reactive gas or combination of gases. The reactive gas source193can supply any combination of ground state and/or excited gas atoms. Gas valves (not shown) or other gas controllers (not shown) can precisely meter the reactive gas into the chamber192. In one embodiment, an excited atom source (not shown) is positioned between the reactive gas source193and the gas injectors194. The reactive gas source193delivers ground state reactive gas atoms to the excited atom source. The excited atom source raises the energy of the ground state atoms to create excited atoms and then the excited atoms are supplied to the chamber192through the gas injectors194.

The reactive gas is supplied near the substrate182. A shield195can be used to reduce the quantity of reactive gas that can directly travel towards the segmented magnetron cathode102. The shield does not, however, completely prevent the reactive gas from diffusing towards the segmented magnetron cathode102and eventually interacting with the segmented magnetron cathode102. A segmented magnetron cathode102including target material can be damaged during the interaction with a reactive gas.

The operation of the plasma source190is similar to the operation of the plasma source100ofFIG. 1. The gas source139provides feed gas between the anode sections191a-cand the magnetron cathode segments102a-cincluding the target material. The gas pressure can be adjusted to optimize the ionization process by modifying the flow rate of the gas and modifying the shape and position of the anode sections191a-crelative to the corresponding magnetron cathode segments102a-c. The power supply128provides voltage pulses to the switch110. The switch110routes the voltage pulses to the various magnetron cathode segments102a-cto ignite and maintain a high density plasma. The reactive gas source193supplies reactive gas in the vicinity of the substrate182. Some of the reactive gas diffuses towards the segmented magnetron cathode102. The reactive gas can interact with the target material and eventually damage the target material. The pressure of the gas flowing across the surface of the magnetron cathode segments102a-ccan be adjusted to reduce the amount of reactive gas that might interact with and eventually poison the target material.

Positively-charged ions in the high-density plasma are accelerated towards the negatively-charged segmented magnetron cathode102. The highly accelerated ions sputter target material from the segmented magnetron cathode102. The bombardment of the segmented magnetron cathode102with highly accelerated ions and the resulting intensive sputtering of the target material can also prevent the reactive gas from damaging the target material. During the sputtering process, a large fraction of the sputtered material is directed towards the substrate182and passes through the reactive gas. The reactive gas interacts with the sputtered material and changes the properties of the sputtered material, thereby creating a new material that sputter coats the substrate182. In one embodiment, a reactive sputtering process and an I-PVD process can be performed together in a combined process. For example, in order to sputter TaN or TiN or other compounds to fill high-aspect-ratio structures on the substrate182, a reactive sputtering process and an I-PVD process can be used.

FIG. 3Ais a graphical representation of an exemplary voltage pulse train200for energizing the plasma source100ofFIG. 1. The power supply128generates the individual square voltage pulses201,202,203,204,205,206,207,208,209,210at the first output126. The switch110receives the individual voltage pulses201,202,203,204,205,206,207,208,209,210at the input124and routes the voltage pulses201,202,203,204,205,206,207,208,209,210in a predetermined sequence to various outputs108,114,118,122of the switch110which are coupled to the various respective magnetron cathode segments102a-d. The sequence can be altered during the process to achieve certain process parameters, such as improved uniformity of the sputtered coating.

In one embodiment, the switch110routes each of the voltage pulses201,202,203,204,205,206,207,208,209,210from the first output126of power supply128to each of the magnetron cathode segments102a-din the following manner. The first voltage pulse201is applied to the first magnetron cathode segment102a, which ignites and sustains a plasma proximate to the first magnetron cathode segment102a. The second voltage pulse202is applied to the second magnetron cathode segment102b, which ignites and sustains a plasma proximate to the second magnetron cathode segment102b. During these pulses, magnetron cathode segments deposit coatings on the substrate. The third voltage pulse203is applied to the third magnetron cathode segment102c, which ignites a plasma proximate to the third magnetron cathode segment102c.

The fourth voltage pulse204is applied to the fourth magnetron cathode segment102dto ignite and sustain a plasma proximate to the fourth magnetron cathode segment102d. The fifth voltage pulse205is applied to the fourth magnetron cathode segment102dto increase coating thickness sputtered on the substrate proximate to the magnetron cathode segment102d.

The sixth voltage pulse206is applied to the first magnetron cathode segment102ato increase coating thickness sputtered on the substrate proximate to the magnetron cathode segment102d. The seventh voltage pulse207is applied to the second magnetron cathode segment102bto increase coating thickness sputtered on the substrate proximate to the magnetron cathode segment102b.

The eighth voltage pulse208is applied to the third magnetron cathode segment102c. The ninth209and the tenth voltage pulses210are applied to the fourth magnetron cathode segment102d. The switch110controls the routing of the individual voltage pulses201,202,203,204,205,206,207,208,209, and210in order to control the uniformity of the coating on the substrate141and the density of the plasma across the segmented magnetron cathode102.

The preceding example illustrates the flexibility that can be achieved with the plasma source100including the segmented magnetron cathode102ofFIG. 1. The switch110can be a programmable switch that routes one or more voltage pulses to the various magnetron cathode segments102a-din a predetermined manner in order to determine the precise distribution of the plasma across the magnetron cathode segments102a-d, which controls the uniformity of the coating on the substrate141. The switch110can also include a controller that modifies the sequence of the individual voltage pulses to the various magnetron cathode segments102a-din response to feedback from measurements taken during a plasma process.

FIG. 3Bis a graphical representation of another exemplary voltage pulse train220for energizing the plasma source100ofFIG. 1that is chosen to generate a plasma having particular properties. The power supply128generates the individual voltage pulses221,222,223,224,225,226,227,228,229,230at the first output126. The switch110receives the individual voltage pulses221,222,223,224,225,226,227,228,229,230at the input124and routes the individual voltage pulses221,222,223,224,225,226,227,228,229,230to various outputs108,114,118,122of the switch110which are coupled to the various magnetron cathode segments102a-d.

In one embodiment, the switch110routes each of the individual voltage pulses221,222,223,224,225,226,227,228,229,230from the first output126of the power supply128to each of the magnetron cathode segments102a-din the following manner. The first voltage pulse221is applied to the fourth magnetron cathode segment102d. The first voltage pulse221ignites and sustains a plasma proximate to the fourth magnetron cathode segment102a. The second voltage pulse222is applied to the third magnetron cathode segment102cto ignite and sustain a plasma proximate to the third magnetron cathode segment102c. The third voltage pulse223is applied to the first magnetron cathode segment102ato ignite and sustain a plasma proximate to the first magnetron cathode segment102a. The plasma proximate to the first102aand the third magnetron cathode segments102cwill tend to migrate towards the second magnetron cathode segment102bbecause of the magnetic coupling described herein.

The fourth voltage pulse224is applied to the second magnetron cathode segment102bto ignite and sustain a plasma proximate to the second magnetron cathode segment102b. During this pulse, the second magnetron cathode segment102deposit coatings on the substrate. The fifth voltage pulse225is applied to the first magnetron cathode segment102ato increase coating thickness on the substrate proximate to the magnetron cathode segment102a. The sixth voltage pulse226is applied to the fourth magnetron cathode segment102dto increase coating thickness on the substrate proximate to the magnetron cathode segment102d. The seventh voltage pulse227is applied to the third magnetron cathode segment102cto increase coating thickness on the substrate proximate to the magnetron cathode segment102c. The eighth voltage pulse228is applied to the second magnetron cathode segment102bto increase coating thickness on the substrate proximate to the magnetron cathode segment102b. The ninth voltage pulse229is applied to the first magnetron cathode segment102a. The tenth voltage pulse230is applied to the fourth magnetron cathode segment102d.

The preceding example illustrates the flexibility of the plasma source100having the segmented magnetron cathode102. Each of the individual voltage pulses221,222,223,224,225,226,227,228,229,230generated by the power supply128can have a different shape, different pulse width, and a different repetition rate. The power supply128is programmable and can generate voltage pulses that each have different pulse parameters. Additionally, the switch110can route one or more of the voltage pulses221,222,223,224,225,226,227,228,229,230to one or more of the magnetron cathode segments102a-dto control the density of the plasma and the uniformity of the sputtered coating.

FIG. 3Cis a graphical representation of another exemplary voltage pulse train240for energizing the plasma source100ofFIG. 1that is chosen to generate a plasma having particular properties. The power supply128generates the individual voltage pulses241,242,243,244,245,246,247,248,249,250at the first output126. The voltage pulses241,242,243,244,245,246,247,248,249,250in this example are substantially saw tooth in shape. The first241and the second242voltage pulses have magnitudes and rise times that are different than the other voltage pulses in the voltage pulse train240. These first two voltage pulses241,242generate a plasma having the desired plasma density. The switch110receives the individual voltage pulses241,242,243,244,245,246,247,248,249,250at the input124and routes the voltage pulses241,242,243,244,245,246,247,248,249,250to particular outputs108,114,118,122of the switch110that are coupled to particular magnetron cathode segments102a-d.

In one embodiment, the switch110routes each of the voltage pulses241,242,243,244,245,246,247,248,249,250from the first output126power supply128to each of the magnetron cathode segments102a-din the following manner. The first voltage pulse241is applied to the first magnetron cathode segment102a. The first voltage pulse241has a sufficient magnitude and rise time to ignite a weakly-ionized plasma and to increase the density of the weakly-ionized plasma to create a strongly-ionized plasma proximate to the first magnetron cathode segment102a. The second voltage pulse242is also applied to the first magnetron cathode segment102a. In one embodiment, the rise time of the voltage pulses241,242,243,244,245,246,247,248,249,250is less than about 400V per 1 μsec. Controlling the rise time of the voltage pulses241,242,243,244,245,246,247,248,249,250can control the density of the plasma though various ionization processes as follows.

The second voltage pulse242has a magnitude and a rise time that is sufficient to ignite a weakly-ionized plasma and to drive the weakly-ionized plasma to a strongly-ionized state. The rise time of the second voltage pulse242is chosen to be sharp enough to ignite the weakly-ionized plasma and to shift the electron energy distribution of the weakly-ionized plasma to higher energy levels to generate ionizational instabilities that create many excited and ionized atoms.

The magnitude of the second voltage pulse242is chosen to generate a strong enough electric field between the first magnetron cathode segment102aand the anode section104ato shift the electron energy distribution to higher energies. The higher electron energies create excitation, ionization, and recombination processes that transition the state of the weakly-ionized plasma to the strongly-ionized state.

The strong electric field generated by the second voltage pulse242between the first magnetron cathode segment102aand the anode section104acauses several different ionization processes. The strong electric field causes some direct ionization of ground state atoms in the weakly-ionized plasma. There are many ground state atoms in the weakly-ionized plasma because of its relatively low-level of ionization. In addition, the strong electric field heats electrons initiating several other different types of ionization processes, such as electron impact, Penning ionization, and associative ionization. Plasma radiation can also assist in the formation and maintenance of the high current discharge. The direct and other ionization processes of the ground state atoms in the weakly-ionized plasma significantly increase the rate at which a strongly-ionized plasma is formed. Some of these ionization processes are further described in co-pending U.S. patent application Ser. No. 10/708,281, entitled Methods and Apparatus for Generating Strongly-Ionized Plasmas with Ionizational Instabilities which is assigned to the present assignee. The entire disclosure of U.S. patent application Ser. No. 10/708,281 is incorporated herein by reference.

The third voltage pulse243is applied to the second magnetron cathode segment102band ignites a plasma proximate to the second magnetron cathode segment102b. The fourth voltage pulse244is applied to the third magnetron cathode segment102cand ignites a plasma proximate to the third magnetron cathode segment102c. The fifth voltage pulse245is applied to the fourth magnetron cathode segment102band ignites a plasma proximate to the fourth magnetron cathode segment102d. The sixth voltage pulse246is applied to the first magnetron cathode segment102aand maintains the plasma proximate to the first magnetron cathode segment102aat the desired plasma density and the desired plasma uniformity in order to obtain the desired coating uniformity on the substrate.

The seventh voltage pulse247is applied to the second magnetron cathode segment102b. The eighth voltage pulse248is applied to the third magnetron cathode segment102c. The ninth voltage pulse249is applied to the fourth magnetron cathode segment102d. The tenth voltage pulse250is applied to the first magnetron cathode segment102a. The third243through the tenth voltage pulse250maintain the plasma at the desired plasma density and the desired plasma uniformity. The magnitude, rise time, fall time, shape, and duration of the first241and the second voltage pulses242are chosen to generate a plasma having the desired density and uniformity to create a uniform coating on the substrate141.

The saw-tooth shape of the voltage pulse train240does not sustain the strongly-ionized plasma because each of the voltage pulses241,242,243,244,245,246,247,248,249,250is abruptly terminated. Each of the voltage pulses241,242,243,244,245,246,247,248,249,250can have different rise times and/or different voltage levels. The preceding example illustrates the flexibility of the plasma source100having the power supply128and the switch110. One or more of the voltage pulses241,242,243,244,245,246,247,248,249,250generated by the power supply128can have a different magnitude and/or rise time. Additionally, the switch110can route one or more of the individual voltage pulses241,242,243,244,245,246,247,248,249,250to one or more of the magnetron cathode segments102a-din a predetermined sequence.

FIG. 3Dis a graphical representation of another exemplary voltage pulse train260for energizing the plasma source100ofFIG. 1that is chosen to generate a plasma having particular properties. The power supply128generates the voltage pulses261,262,263,264,265in the voltage pulse train260at the first output126. The voltage pulses261,262,263,264,265in this example have a magnitude of about 500V, a pulse width of about 1 ms, and a repetition rate of about 5 Hz. The switch110receives the voltage pulses261,262,263,264,265at the input124and routes the individual voltage pulses261,262,263,264,265to specific outputs108,114,118,122of the switch110which are coupled to specific magnetron cathode segments102a-d.

In one embodiment, the switch110routes each of the voltage pulses261,262,263,264,265from the power supply128to each of the magnetron cathode segments102a-din the following manner. The first voltage pulse261is applied to the first magnetron cathode segment102a. The first voltage pulse261has a magnitude of 500V and a pulse width of 1 ms which is sufficient to ignite a plasma proximate to the first magnetron cathode segment102a. The second voltage pulse262is applied to the second magnetron cathode segment102a. The second voltage pulse262has a magnitude of 500V and a pulse width of 1 ms that is sufficient to ignite a plasma proximate to the second magnetron cathode segment102b.

The third voltage pulse263is applied to the third magnetron cathode segment102cand ignites a plasma proximate to the third magnetron cathode segment102c. The fourth voltage pulse264is applied to the fourth magnetron cathode segment102dand ignites a plasma proximate to the fourth magnetron cathode segment102d. The fifth voltage pulse265is applied to the first magnetron cathode segment102aand maintains the plasma proximate to the first magnetron cathode segment102aat the desired plasma density and uniformity. In this example, the voltage pulses261,262,263,264,265are identical.

The preceding example illustrates the flexibility of the plasma source100including the switch110. The switching speed of the switch110in this example should be less than 249 ms in order to route each of the voltage pulses261,262,263,264,265to the various magnetron cathode segments102a-dduring the desired time period. This switching speed can be achieved using various mechanical or electronic switching technology.

FIG. 3Eis a graphical representation of another exemplary voltage pulse train270for energizing the plasma source100ofFIG. 1that is chosen to generate a plasma having particular properties. The power supply128generates the voltage pulses271,272,273,274,275at the first output126. Each individual voltage pulse271,272,273,274,275in this example has two voltage levels. In other embodiments, at least two of the individual voltage pulses271,272,273,274,275have different voltage levels.

The first voltage level Vpreis a pre-ionization voltage level that is used to generate a pre-ionization plasma. The pre-ionization plasma is a weakly-ionized plasma. The weakly-ionized plasma has a plasma density that is less than about 1012 cm−3. In one embodiment, the pre-ionization voltage level has a magnitude that is between about 300V and 2000V. The second voltage level Vmain, is the main voltage level that generates a plasma having the desired plasma density. In one embodiment, two voltage levels are used to generate a plasma having a relatively high plasma density. The plasma having the relatively high plasma density is referred to as a high-density plasma or a strongly-ionized plasma. Typically, high-density plasmas will generate films at a high deposition rate compared with weakly-ionized plasmas. The density of the strongly-ionized plasma is greater than about 1012 cm−3.

The difference in magnitude between the second voltage level Vmainand the first voltage level Vpreis between about 1V and 500V in some embodiments. The switch110receives the individual voltage pulses271,272,273,274,275at the input124and routes the voltage pulses271,272,273,274,275to particular outputs108,114,118,122of the switch110which are coupled to particular magnetron cathode segments102a-d.

In one embodiment, the switch110routes each of the voltage pulses271,272,273,274,275from the output126of the power supply128to each of the magnetron cathode segments102a-din the following manner. The first voltage pulse271is applied to the first magnetron cathode segment102a. A first time period276corresponding to an ignition phase of the pre-ionization plasma has a rise time τignand a magnitude Vprethat are sufficient to ignite a weakly-ionized plasma proximate to the first magnetron cathode segment102a.

A second time period277having a value of between about 1 microsecond and 10 seconds is sufficient to maintain the weakly-ionized plasma. The voltage level during the second time period277can be constant or can decrease for a time period277′ according to a fall time τ1′. The value of the fall time τ1′ is in the range of between about 1 microsecond and 10 seconds. A third time period278of the first voltage pulse271has a rise time τ1that is less than about 400V/usec and a magnitude Vmainthat is sufficient to increase the density of the plasma proximate to the first magnetron cathode segment102a. The rise time τ1of the third time period278of the first voltage pulse271can be varied to control the density of the plasma including the amount the sputtered metal ions. A fourth time period279of the first voltage pulse271corresponds to the main phase of the first voltage pulse271. The fourth time period279maintains the plasma at the desired plasma density. The magnitude of the voltage Vmainduring the fourth time period279is in the range of between about 350V and 2500 V depending upon the particular application.

The second voltage pulse272is applied to the second magnetron cathode segment102b. The first time period276of the second voltage pulse272corresponds to the ignition phase of the second voltage pulse272and has a rise time τignand a magnitude Vprethat is sufficient to ignite a plasma proximate to the second magnetron cathode segment102b. A second time period280of the second voltage pulse272is sufficient to maintain a weakly-ionized plasma proximate to the second magnetron cathode segment102b. The voltage level during the second time period280can be constant or can decrease for a time period280′ according to a fall time τ2′. A third time period281of the second voltage pulse272has a rise time τ2and a magnitude Vmainthat is sufficient to increase the density of the plasma proximate to the second magnetron cathode segment102b.

The rise time τ2of the third time period281of the second voltage pulse272is sharper than the rise time τ1of the third time period278of the first voltage pulse271. This sharper rise time τ2generates a higher-density plasma proximate to the second magnetron cathode segment102bthan the plasma generated proximate to the first magnetron cathode segment102a. The fourth time period282of the second voltage pulse272corresponds to the main phase of the second voltage pulse272.

The rise times τ1-τ5of the voltage pulses271-275can be chosen so that the voltage pulses217-275provide sufficient energy to the electrons in the weakly-ionized plasma to excite atoms in the plasma, ionize ground state or excited atoms, and/or increase the electron density in order to generate a strongly-ionized plasma. The desired rise time depends on the mean free time between collisions of the electrons between atoms and molecules in the weakly-ionized plasma that is generated from the feed gas. Also, the magnetic field from the magnetron can strongly affect on the electron mean free time between the collisions. Therefore, the chosen rise time depends on several factors, such as the type of feed gas, the magnetic field, and the gas pressure.

In one embodiment, the rise time τ2of the third time period281of the second voltage pulse272is sufficient to cause a multi-step ionization process (instead of direct ionization process by electron impact). In a first step, the second voltage pulse272initially raises the energy of the ground state atoms in the weakly-ionized plasma to a level where the atoms are excited. For example, argon atoms require an energy of about 11.55 eV to become excited. In a second step, the magnitude and rise time in the third time period281of the second voltage pulse272are chosen to create a strong electric field that ionizes the exited atoms. Excited atoms ionize at a much high rate than neutral atoms. For example, argon excited atoms only require about 4 eV of energy to ionize while neutral atoms require about 15.76 eV of energy to ionize. Additionally, the collisions between excited argon atoms and ground state sputtered atoms, such as copper atoms, can create additional ions and electron that will increase plasma density. The multi-step ionization process is described in co-pending U.S. patent application Ser. No. 10/249,844, entitled High-Density Plasma Source using Excited Atoms, which is assigned to the present assignee. The entire disclosure of U.S. patent application Ser. No. 10/249,844 is incorporated herein by reference.

The multi-step ionization process can be described as follows:
Ar+e−→Ar*+e−
Ar*+e−→Ar++2e−

where Ar represents a neutral argon atom in the initial plasma, e− represents an ionizing electron generated in response to an electric field, and Ar* represents an excited argon atom in the initial plasma. The collision between the excited argon atom and the ionizing electron results in the formation of an argon ion (Ar+) and two electrons.

In one embodiment, ions in the developing plasma strike the second magnetron cathode segment102bcausing secondary electron emission. These secondary electrons interact with neutral or excited atoms in the developing plasma. The interaction of the secondary electrons with the neutral or excited atoms further increases the density of ions in the developing plasma as feed gas is replenished. Thus, the excited atoms tend to more rapidly ionize near the surface of the second magnetron cathode segment102bthan the neutral argon atoms. As the density of the excited atoms in the plasma increases, the efficiency of the ionization process rapidly increases. The increased efficiency can result in an avalanche-like increase in the density of the plasma that creates a strongly-ionized plasma proximate to the second magnetron cathode segment102b.

The magnetic field136b(FIG. 2A) generated by the magnet assembly134bcan also increase the density of the plasma. The magnetic field136bthat is located proximate to the second magnetron cathode segment102bis sufficient to generate a significant electron ExB Hall current which causes the electron density in the plasma to form a soliton or other non-linear waveform that increases the density of the plasma. In some embodiments, the strength of the magnetic field136brequired to cause the electron density in the plasma to form such a soliton or non-linear waveform is in the range of fifty to ten thousand gauss.

An electron ExB Hall current is generated when the voltage pulse train270applied between the segmented magnetron cathode102a,b,c, dand the anode sections104a, b, c, dgenerates primary electrons and secondary electrons that move in a substantially circular motion proximate to the cathode segments102a, b, c, daccording to crossed electric and magnetic fields. The magnitude of the electron ExB Hall current is proportional to the magnitude of the discharge current in the plasma. In some embodiments, the electron ExB Hall current is approximately in the range of three to ten times the magnitude of the discharge current.

In one embodiment, the electron density increases in an avalanche-like manner because of electron overheating instability. Electron overheating instabilities can occur when heat is exchanged between the electrons in the plasma, the feed gas, and the walls of the chamber. For example, electron overheating instabilities can be caused when electrons in a weakly-ionized plasma are heated by an external field and then lose energy in elastic collisions with atoms in the feed gas. The elastic collisions with the atoms in the feed gas raise the temperature and lower the density of the feed gas. The decrease in the density of the gas results in an increase in the electron temperature because the frequency of elastic collisions in the feed gas decreases. The increase in the electron temperature again enhances the heating of the gas. The electron heating effect develops in an avalanche-like manner and can drive the weakly-ionized plasma into a strongly-ionized state.

The third273, fourth274, and fifth voltage pulses275can include time periods having various shapes and durations depending on the desired properties of the plasma. The preceding example illustrates the flexibility of the plasma source100having the power supply128and the switch110. The power supply128can generate voltage pulses having various shapes and rise-times depending on the desired properties of the plasma. The switch can route each of the individual voltage pulses271,272,273,274,275to the particular magnetron cathode segments102a-ddepending on the desired uniformity of the sputtered coating and the desired density of the plasma.

In some embodiments of the present invention, the plasma source100is configured with the power supply128(FIG. 1) connected directly to all segments of the magnetron cathode102without the use of the switch110. Such a plasma source can be driven using the voltage pulse train270shown inFIG. 3Ethat generates a plasma having particular properties. When the first voltage pulse271is applied to the magnetron cathode102, a weakly ionized plasma is established in the first time period276. The weakly ionized plasma is maintained for during the second time period277. During the second period277where the weakly ionized plasma is maintained, a relatively low deposition rate and a relatively low level of ionization of sputtered gas atoms or/and molecules is produced. Consequently, the number of sputtered ions generated is very low. In one embodiment, the ratio of total ions (NI) to neutral atoms (NN) in the plasma volume proximate to the substrate is in the range 0.1 and 0.01. The resulting sputtered film will have a column-like structure with a relatively high level of porosity, surface roughness, and stress.

In the third time period278, the weakly ionized plasma transitions to a strongly ionized plasma. In the fourth time period279, the high density plasma is maintained. While the high density plasma is maintained, there is a high deposition rate and a high level of ionization of feed gas and sputtered material atoms. For example, while the high density plasma is maintained, the ratio of total ions (NI) to neutral atoms (NN) in the plasma volume proximate to the substrate can be in the range of 0.1 to 1.0. Also, while the high density plasma is maintained, the resulting sputtered film will have a dense microstructure, with low porosity, low surface roughness, and a low level of stress.

Thus, the present invention is in part the recognition that the shape of the voltage pulse applied to the magnetron cathode102shown inFIG. 1and also to some conventional magnetron cathodes102, determines the ratio of ions to neutral atoms. By adjusting the amplitude, duration and rise time of the voltage pulse applied to the magnetron cathode102, a ratio between neutral atoms and ions can be adjusted to the desired ratio. Changing the ratio between neutral atoms and ions changes the film micro structure and the properties of the film. For example, by changing the ratio between neutral atoms and ions, the film properties, such as the porosity, surface roughness, and the film stress (degree of tensile or compressive strength) can be changed.

FIG. 3Fis a graphical representation of another exemplary voltage pulse train285for energizing the plasma source100ofFIG. 1that is chosen to generate a plasma having particular properties. The power supply128generates the voltage pulses286,287,288,289at the first output126. In this example, the voltage pulses286,287,288,289are identical and each voltage pulse has three voltage levels. In other embodiments, at least two of the voltage pulses286,287,288,289have different voltage levels and/or include different rise times. The first voltage level Vprehas a magnitude that is between about 300V and 2000V. The difference in magnitude between the second voltage level Vmain1and the first voltage level Vpreis between about 1V and 500V. The difference in magnitude between the third voltage level Vmain2and the second voltage level Vmain1is between about 1V and 500V.

In one embodiment, the switch110routes each of the individual voltage pulses286,287,288,289to the first102a, the second102b, the third102c, and the fourth magnetron cathode segments102d, respectively. Each of the voltage pulses286,287,288,289includes six time periods. An ignition time period290of the first voltage pulse286has a rise time τign. A second time period291of the first voltage pulse286has a magnitude Vprethat is between about 300 V and 2000 V and a duration that is between about 1 microsecond and 10 seconds that is sufficient to ignite a weakly-ionized plasma proximate to the first magnetron cathode segment102a. The voltage level during the second time period291can be constant or can decrease for a time period291′ according to a fall time τ1′.

A third time period292of the first voltage pulse286has a rise time τ1that is sufficient to increase the density of the plasma proximate to the first magnetron cathode segment102a. The rise time τ1is less than about 300 V/μsec. The increase in the density of the plasma due to the sharpness of the rise time τ1generates a high-density plasma or a strongly-ionized plasma from the weakly-ionized plasma proximate to the first magnetron cathode segment102a.

A fourth time period293of the first voltage pulse286has a duration that is between about one microsecond and 10 seconds and a magnitude Vmain1that is between about 300V and 2000 V, which is sufficient to maintain the high-density plasma. The voltage level during the fourth time period293can be constant or can decrease for a time period293′ according to a fall time τ2′. A fifth time period294of the first voltage pulse286has a rise time τ2that is sufficient to increase the density of the high-density plasma proximate to the first magnetron cathode segment102a. The rise time τ2is less than about 300 V/μsec. The increase in the density of the high-density plasma due to the sharpness of the rise time τ2generates a higher-density plasma or an almost fully-ionized plasma from the high-density plasma proximate to the first magnetron cathode segment102a. A sixth time period295of the first voltage pulse286has a duration that is between about 1 microsecond and 10 seconds and a magnitude Vmain2that is between about 400V and 3000V, which is sufficient to maintain the almost fully-ionized plasma.

The second287, third288, and fourth voltage pulses289include the same time periods as the first voltage pulse286and are each routed to particular magnetron cathode segments102b-ddepending on the desired properties of the plasma, such as the desired plasma density, deposition rate, and the uniformity of the sputtered coating.

FIG. 3Gis a graphical representation of another exemplary voltage pulse train296for energizing the plasma source100ofFIG. 1that is chosen to generate a plasma having particular properties. In this example, the voltage pulses297are identical. In other embodiments, at least two of the voltage pulses297have different voltage levels and/or include different rise times. The power supply128generates the voltage pulses297at the first output126. The voltage pulses297in this example each have only one voltage level. The voltage level Vmainhas a magnitude that is between about 300V and 2000V.

In one embodiment, the switch110routes each of the voltage pulses297to the first102a, the second102b, the third102c, and the fourth magnetron cathode segments102d. Each of the voltage pulses297includes two time periods. A first time period298of each of the voltage pulses297has a rise time τ1that is sufficient to both ignite a weakly-ionized plasma and to increase the density of the weakly-ionized plasma. The rise time τ1is less than about 400 V/μsec. A second time period299of each of the voltage pulses297has a duration that is between about 5 microseconds and 10 seconds and a magnitude Vmainthat is between about 300V and 2000V, which is sufficient to maintain the plasma at the increased density level.

In this example, the voltage pulses297are applied to the magnetron cathode segment102awithout the express pre-ionization time period that was described in connection with previous examples. In this example, a plasma condition exists when the rise time τ1of the first phase298is such that a plasma develops having a plasma density that can absorb the power generated by the power supply128. This plasma condition corresponds to a rapidly developing initial plasma that can absorb the power generated by the application of the voltage pulse297without the plasma contracting. Thus, the weakly-ionized plasma and the strongly-ionized plasma both develop in a single phase298of the voltage pulse297. The strongly-ionized plasma is sustained in the phase299of the voltage pulse297.

Referring to bothFIGS. 3F and 3G, in some embodiments of the present invention, the plasma source100is configured with the power supply128(FIG. 1) connected directly to all segments of the magnetron cathode102without the use of the switch110as described in connection withFIG. 3E. Such a plasma source can be driven using the voltage pulse trains285and296shown inFIGS. 3F, 3Gthat generates a plasma having particular properties. For example, experiments have been performed where the power supply128first generates the train of voltage pulses285a period of one second. During the first train of voltage pulses285, the ratio of total ions (NI) to neutral atoms (NN) in the plasma volume proximate to the substrate was about 0.4 and a first sputtered layer about 10 Å thick was deposited.

The power supply128then generates the train of voltage pulses296for a period of seven seconds. During the second train of voltage pulses296, the ratio of total ions (NI) to neutral atoms (NN) in the plasma volume proximate to the substrate was about 0.6 and a second sputtered layer about 5 Å thick was deposited. The layers sputtered using the first train of voltage pulses285and using the second train of voltage pulses296had different film structures. The film structures were different because the ratio of total ions (NI) to neutral atoms (NN) in the first sputtered layer plasma volume was different from the ratio of total ions (NI) to neutral atoms (NN) in the second sputtered layer.

An alternating or modulated thin film structure was achieved by alternating between applying the first train of voltage pulses285to the magnetron cathode102and applying the second train of voltage pulses296to the magnetron cathode a plurality of times. The number of alternating thin films and the ratio of total ions (NI) to neutral atoms (NN) in the plasma volume which generates each of the thin films can be chosen to achieve certain mechanical, electrical, magnetic film properties.

FIG. 3His a graphical representation of yet another exemplary voltage pulse train300for energizing the plasma source100ofFIG. 1that is chosen to generate a plasma having particular properties. In this example, the voltage pulses302,304each include four time periods. However, the magnitudes and rise times of the four time periods are different for each voltage pulse302,304.

The power supply128generates the voltage pulses302,304at the output126. The voltage pulses302,304in this example each have two voltage levels. In one embodiment, the switch110routes both of the voltage pulses302,304to the first magnetron cathode segment102a. Each of the voltage pulses302,304having the four time periods generates a plasma having different plasma properties, such as different plasma densities. In other embodiments, subsequent voltage pulses (not shown) are routed by the switch110to the other magnetron cathode segments102b-d.

A first time period306of the first voltage pulse302has a rise time τignthat is sufficient to ignite a plasma proximate to the first magnetron cathode segment102a. In one embodiment, the rise time τignis less than about 400 V/μsec. The developing plasma has a discharge current308which increases as the magnitude of the voltage increases. Relatively few electrons exist before the plasma is ignited, therefore, the developing discharge current308lags behind the first time period306of the first voltage pulse302in time. The power310can be determined by taking the product of the voltage and the discharge current. The power310initially tracks the discharge current308in this example.

A second time period312of the first voltage pulse302has a duration and a magnitude Vprethat is sufficient to sustain a weakly-ionized plasma. In one embodiment, the magnitude of Vpreis between about 300V and 2000V. In one embodiment, the duration of the time period312is between about 1 microsecond and 10 seconds. During the second time period312, the discharge current314corresponding to the voltage Vpreplateaus at a value that corresponds to a relatively low density of the plasma. The power316during the second time period312is also at a relatively low level that corresponds to the relatively low density of the weakly-ionized plasma.

A third time period318of the first voltage pulse302has a rise time τ1that is sufficient to slightly increase the density of the weakly-ionized plasma. The rise time τ1is relatively long and therefore the voltage in the third time period318increases relatively slowly to a peak voltage V1. The discharge current320also increases relatively slowly and reaches a relatively low peak current level I1. The peak current I1corresponds to a plasma density where there is insufficient electron energy gained in the third time period318to substantially increase the plasma density.

The power322reaches an intermediate peak power level P1that corresponds to the peak discharge current I1. If the duration of the third time period318of the first voltage302was extended to the duty cycle limit of the power supply128, the peak discharge current I1would slowly increase, and the intermediate peak power level P1would remain at a level that corresponds to a plasma having an intermediate plasma density.

A fourth time period324of the first voltage pulse302has a duration and a magnitude V1that is sufficient to maintain the plasma having the intermediate plasma density. During the fourth time period324, the discharge current326plateaus at a value that corresponds to the intermediate plasma density. The power328during the fourth time period324is also at a moderate level corresponding to a moderate density of the plasma.

A first time period306′ of the second voltage pulse304has a rise time τignthat is the same as the rise time τignof the first time period306of the first voltage pulse302. This rise time is sufficient to ignite a plasma proximate to the first magnetron cathode segment102a. The developing plasma has a discharge current308′ which increases as the magnitude of the voltage increases and behaves similarly to the plasma ignited by the first time period306of the first voltage pulse302. The developing discharge current308′ lags behind the first time period306′ of the second voltage pulse304in time. The power310′ initially tracks the discharge current308′.

A second time period312′ of the second voltage pulse304has a duration and a magnitude Vprethat is the same as the duration and the magnitude Vpreof the second time period312of the first voltage pulse302. The second time period312′ of the second voltage pulse304is sufficient to pre-ionize or precondition the plasma to maintain the plasma in a weakly-ionized condition. During the second time period312′, the discharge current314′ plateaus at a value that corresponds to the relatively low density of the plasma. The power316′ during the second time period312′ is also at a relatively low level that corresponds to the relatively low density of the weakly-ionized plasma.

A third time period330of the second voltage pulse304has a rise time τ2that is sufficient to rapidly increase the density of the plasma. The rise time τ2is relatively fast and, therefore, the voltage in the third phase330increases very quickly to a peak voltage having a magnitude V2. In one embodiment, the rise time τ2is less than about 300 V/μsec. The density of the plasma and the uniformity of the sputtered coating can be modified by modifying at least one of the rise time τ2, the peak voltage V2(amplitude), the fall time, the shape, and the duration of the second voltage pulse304.

The sharp rise time τ2dramatically increases the number of electrons in the plasma that can absorb the power generated by the power supply128(FIG. 1). This increase in the number of electrons results in a discharge current332that increases relatively quickly and reaches a peak current level12that corresponds to a high-density plasma condition. The peak current level12corresponds to a point in which the plasma is strongly-ionized. The peak current level12, and therefore the plasma density, can be controlled by adjusting the rise time τ2of the third time period330of the second voltage pulse304. Slower rise times generate lower density plasmas, whereas faster rise times generate higher density plasmas. A higher density plasma will generate coatings at a higher deposition rate.

The amplitude and rise time τ2during the third time period330of the second voltage pulse304can also support additional ionization processes. For example, the rise time τ2in the second voltage pulse304can be chosen to be sharp enough to shift the electron energy distribution of the weakly-ionized plasma to higher energy levels to generate ionizational instabilities that create many excited and ionized atoms. The higher electron energies create excitation, ionization, and recombination processes that transition the state of the weakly-ionized plasma to the strongly-ionized state.

The strong electric field generated by the second voltage pulse304can support several different ionization processes. The strong electric field causes some direct ionization of ground state atoms in the weakly-ionized plasma. There are many ground state atoms in the weakly-ionized plasma because of its relatively low-level of ionization. In addition, the strong electric field heats electrons initiating several other different types of ionization processes, such as electron impact, Penning ionization, and associative ionization. Plasma radiation can also assist in the formation and maintenance of the high current discharge. The direct and other ionization processes of the ground state atoms in the weakly-ionized plasma significantly increase the rate at which a strongly-ionized plasma is formed.

A fourth time period336of the second voltage pulse304has a duration that is between about 1 microsecond and 10 seconds and a magnitude V2that is between about 300V and 2000V, which is sufficient to maintain a strongly-ionized plasma. During the fourth time period336, the discharge current338plateaus at a level that corresponds to a relatively high plasma density. The power340during the fourth time period336is also at a relatively high-level that corresponds to the relatively high plasma density.

In some embodiments, voltage pulses having additional time periods with particular rise times can be used to control the density of the plasma. For example, in one embodiment the second voltage pulse304includes a fifth time period having an even sharper rise time. In this embodiment, the density of the strongly-ionized plasma is even further increased.

Thus, the density of the plasma as well as the uniformity of the resulting sputtered film generated by the plasma source100can be adjusted by adjusting at least one of a rise time, a fall time, an amplitude, a shape, and a duration of the voltage pulses.FIG. 3Hillustrates that the third time period318of the first voltage pulse302having the relatively slow rise time τ1generates a relatively low peak current level τ1that corresponds to a relatively low plasma density. In contrast, the third time period330of the second voltage pulse304has a rise time τ2that generates a relatively high peak current level12that corresponds to a relatively high plasma density.

A sputtering system including the plasma source100(FIG. 2A) can deposit a highly uniform film with a high deposition rate. In addition, a sputtering system including a plasma source100having a segmented target corresponding to the segmented magnetron cathode102can be designed and operated so that the target material on the segmented target erodes in a uniform manner, resulting in full face erosion of the segmented target. The power supply128can also be effectively used to generate uniform high-density plasmas in magnetrons having one-piece planar magnetron cathodes.

The plasma source100ofFIG. 2Ais well suited for I-PVD systems. An I-PVD system including the plasma source100(FIG. 2A) can independently generate a more uniform coating, have a higher deposition rate, and have an increased ion flux compared with known I-PVD systems having one-piece planar cathodes.

FIG. 3Iis a graphical representation of exemplary voltage pulse train340for energizing the plasma source100ofFIG. 1that is chosen to generate a plasma having particular properties. The voltage pulse train340includes individual voltage pulses341that are identical. Each of the individual voltage pulses341can include multiple peaks as shown inFIG. 3I. The power supply128generates the voltage pulses341at the first output126. The voltage pulses341in this example each have two voltage levels. The voltage level Vprehas a magnitude that is between about 300V and 1,000V. The voltage level Vmainhas a magnitude that is between about 300V and 2,000V.

Each of the voltage pulses341include multiple rise times and fall times. A first rise time342is sufficient to ignite a plasma from a feed gas. The first rise time can be less than 400V/usec. The magnitude343of the first voltage peak is sufficient to maintain a plasma in a weakly-ionized state. The time period t1of the first voltage peak is between about 10 microseconds and 1 second. A second rise time344and magnitude345of the second voltage peak is sufficient to increase the density of the weakly-ionized plasma to generate a strongly-ionized plasma from the weakly-ionized plasma. The second rise time344can be less than 400V/μsec. A fall time346of the second voltage peak is chosen to control the density of the strongly-ionized plasma in preparation for a third voltage peak. The fall time can be less than 400V/μsec. The second voltage peak is terminated after a time period t2. The time period t2of the second voltage peak is between about 10 microseconds and 1 second.

After the termination of the second voltage peak, the voltage345drops to a voltage level347that corresponds to the voltage343of the first voltage peak. The voltage level347is chosen to maintain a sufficient density of the plasma in preparation for the third voltage peak. The rise time348and the magnitude349of the third voltage peak is sufficient to increase the density of the plasma to create a strongly-ionized plasma. Additional voltage peaks can also be used to condition the plasma depending on the specific plasma process. The voltage peaks can have various rise times, fall times, magnitudes, and durations depending on the desired properties of the plasma. The voltage pulses341ofFIG. 3Ican decrease the occurrence of arcing in the chamber by supplying very high power to the plasma in small increments that correspond to the voltage peaks. The incremental power is small enough to prevent an electrical breakdown condition from occurring in the chamber, but large enough to develop a strongly-ionized or high-density plasma that is suitable for high deposition rate sputtering. Additionally, the incremental power can prevent a sputtering target from overheating by holding the average temperature of the sputtering target relatively low.

An operation of the plasma source100ofFIG. 2Ais described with reference toFIG. 4. This operation relates to generating a plasma and controlling the uniformity of the sputtered coating.FIG. 4is a flowchart350of a method for generating a plasma according to one embodiment of the invention. The uniformity of the sputtered coating can be controlled by varying one or more parameters in the plasma source100. Many parameters can be varied. For example, parameters related to the power supply128, parameters related to the switch110, parameters related to the gas source139, and/or parameters related to the magnet assemblies134a-dcan be varied.

In step352, the power supply128generates a pulse train at the output126comprising voltage pulses. In step354, the switch110routes the voltage pulses to individual magnetron cathode segments102a-dof the segmented magnetron cathode102. The plasma sputters material from the individual magnetron cathode segments102a-d. The material is deposited on a substrate to create a sputtered film or coating. The uniformity of the coating is measured in step356. In step358, the uniformity of the coating is evaluated. If the coating uniformity is found to be sufficient, the generation of the plasma continues in step360.

If the coating uniformity is found to be insufficient, the sequence of the voltage pulses applied to the magnetron cathode segments102a-dis modified in step362. The sequence of the voltage pulses can be modified such that one or more voltage pulses are applied to each of the magnetron cathode segments102a-din any order that optimizes the uniformity of the sputtered coating.

Once the sequence of the voltage pulses is modified in step362, the voltage pulses are routed to the various magnetron cathode segments102a-din step364. The uniformity of the coating is again measured in step366. In step368, the uniformity of the coating is again evaluated. If the coating uniformity is found to be sufficient, the generation of the plasma continues in step370.

If the coating uniformity is found to be insufficient in step368, one or more parameters of the voltage pulses are modified in step372. For example, the pulse width, the pulse shape, the rise time, the fall time, the magnitude, the frequency, and/or any other parameters that define the voltage pulses can be modified by the power supply128. In step374, the switch110routes the voltage pulses to the magnetron cathode segments102a-d. The uniformity of the coating is again measured in step376. In step378, the uniformity of the coating is again evaluated. If the coating uniformity is found to be sufficient, the generation of the plasma continues in step379.

If the coating uniformity is found to be insufficient in step378, the sequence of the voltage pulses applied to the magnetron cathode segments102a-dis again modified in step362and the process continues until the coating uniformity is sufficient for the specific plasma process.

FIG. 5is a table380of exemplary voltage pulse parameters that can be associated with particular magnetron cathode segments102a-d(FIG. 1). The table380illustrates the many different voltage pulses parameters that can be applied to particular magnetron cathode segments102a-din order to achieve certain plasma densities and plasma uniformity.

The first column382of table380illustrates the specific magnetron cathode segment102a-nto which a voltage pulse is applied. The second column384illustrates an exemplary pulse sequence that can be applied to the magnetron cathode segments102a-d. In this exemplary pulse sequence: (1) the first pulse is applied to the fourth magnetron cathode segment102d; (2) the second pulse is applied to the third magnetron cathode segment102c; (3) the third pulse is applied to the second magnetron cathode segment102b; (4) the fourth pulse is applied to the first magnetron cathode segment102a; (5) the fifth pulse is applied to the fourth magnetron cathode segment102d; (6) the sixth pulse is applied to the second magnetron cathode segment102b; (7) the seventh pulse is applied to the first magnetron cathode segment102a; (8) the eighth pulse is applied to the fourth magnetron cathode segment102d; and (9) the ninth and tenth pulses are applied to third magnetron cathode segment102c. In some embodiments, the pulses (first pulse through tenth pulse) are pulse trains each including at least two pulses. The specific pulse sequence can affect the density of the plasma and the uniformity of a resulting sputtered film across a workpiece.

The third column388illustrates exemplary voltage pulse widths in microseconds that are applied to each magnetron cathode segment102a-d. In this example, a voltage pulse having a pulse width of 1,000 μsec is applied to the first magnetron cathode segment102a. A voltage pulse having a pulse width of 1,200 μsec is applied to the second magnetron cathode segment102b. Voltage pulses having pulse widths of 2,000 μsec are applied to each of the third102cand the fourth magnetron cathode segments102d. The pulse width or pulse duration of each voltage pulse can affect the plasma density and properties of a resulting sputtered film.

The fourth column390illustrates exemplary rise times of the voltage pulses applied to the various magnetron cathode segments102a-d. The rise times in the fifth column390correspond to the rise times τ1, τ2of the third time periods278,281of the voltage pulses271,272illustrated inFIG. 3E. The fifth column390illustrates that voltage pulses having different rise times can be applied to different magnetron cathode segments102a-d. The different rise times can generate plasmas having different plasma densities that are proximate to the various magnetron cathode segments102a-d. As described herein, the rise times of the voltage pulses can strongly influence the rate of ionization and the density of the plasma.

In this example, a voltage pulse having a rise time of 1V/μsec is applied to the first magnetron cathode segment102a. A voltage pulse having a rise time of 0.5V/μsec is applied to the second magnetron cathode segment102b. A voltage pulse having a rise time of 2V/μsec is applied to the third magnetron cathode segment102c. A voltage pulse having a rise time of 2V/μsec is applied to the fourth magnetron cathode segment102d. The voltage pulses applied to the magnetron cathode segments102a-dcan have faster rise times depending upon the design of the plasma source and the desired plasma conditions. A voltage pulse271(FIG. 3E) can include different time periods277,279having different voltage levels and different durations that sustain plasmas having different plasma densities.

The fifth column392indicates the amount of power generated by the voltage pulses that are applied to each magnetron cathode segment102a-d. In this example, the power generated by applying the voltage pulse to the first magnetron cathode segment102ais 80 kW. The power generated by applying the voltage pulse to the second magnetron cathode segment102bis 60 kW. The power generated by applying the voltage pulse to the third102cand the fourth magnetron cathode segments102dis 120 kW. The power applied to each of the magnetron cathode segments102a-dcan affect the density of the plasma as well as the uniformity of a sputtered film across the substrate.

FIG. 6illustrates a cross-sectional view of a plasma source400including a segmented magnetron cathode402according to one embodiment of the invention. The plasma source400includes the power supply128and the switch110. The segmented magnetron cathode402includes a plurality of magnetron cathode segments402a-d. The plurality of magnetron cathode segments402a-dis typically electrically isolated from each other. Anodes404a-care positioned adjacent to the respective magnetron cathode segments402a-d.

The plasma source400also includes magnet assemblies406a-dthat are positioned adjacent to the respective magnetron cathode segments402a-d. The first magnet assembly406acreates a magnetic field (not shown) proximate to the first magnetron cathode segment402a. The magnetic field traps electrons in the plasma proximate to the first magnetron cathode segment402a. Additional magnetic fields trap electrons in the plasma proximate to the other respective magnetron cathode segments402b-d.

The magnet assemblies406a-dcan create magnetic fields having different geometrical shapes and different magnetic field strengths. Creating magnetic fields having different magnetic fields strengths can improve the uniformity of a sputtered film on a substrate408. For example, the first magnet assembly406acan include strong magnets that create a stronger magnetic field than magnets that are included in the fourth magnet assembly406d. A stronger magnetic field may be required proximate to the first magnetron cathode segment402a, since the first magnet assembly406ais further away from the substrate408than the fourth magnet assembly406d.

The substrate408or workpiece is positioned proximate to the segmented magnetron cathode402. The plasma source400can be used to sputter coat the substrate408. In this embodiment, each of the magnetron cathode segments402a-dincludes target material. The power supply128and the switch110control the voltage pulses applied to each of the magnetron cathode segments402a-dincluding the target material. The target material from each of the magnetron cathode segments402a-dsputter coats the substrate408to generate coatings410a-dthat correspond to each of the magnetron cathode segments402a-d.

The plasma source400illustrates that the magnetron cathode segments402a-din the segmented magnetron cathode402do not have to be in the same horizontal planes with respect to the substrate408. In the example shown inFIG. 6, each of the magnetron cathode segments402a-dis in a unique horizontal plane with respect to a plane that is parallel to the substrate408. Each of the magnetron cathode segments402a-dis also in a unique vertical plane with respect to a plane that is perpendicular to the substrate408. For example, the distance D1from the first magnetron cathode segment402ato the substrate408is greater than the distance D2from the second magnetron cathode segment402bto the substrate408.

In one embodiment, the distances D1-D4between the respective magnetron cathode segments402a-dand the substrate408can be varied to increase the uniformity of the sputtered coating or to optimize the plasma process. In addition to varying the distances D1-D4in order to optimize the plasma process, the parameters of the power supply128and the switch110can be adjusted to affect the uniformity of the coatings410a-dacross the substrate408. The coating uniformity412can be varied to create a predefined thickness profile across the substrate408.

In one embodiment, the plasma source400is used to etch the substrate408. In this embodiment, the plasma generated by segmented magnetron cathode402can have different densities at different locations across the surface of the substrate408. Therefore, the plasma source400can be used to etch a substrate with a particular etch profile.

The operation of the plasma source400is similar to the operation of the plasma source100ofFIG. 1. The switch110routes the voltage pulses from the power supply128to the various magnetron cathode segments402a-dof the segmented magnetron cathode402. The magnitude, shape, rise time, fall time, pulse width, and frequency of the voltage pulses, as well as the sequencing of the various voltage pulses are adjustable by the user to meet the requirements of a particular plasma process.

FIG. 7illustrates a diagram of a plasma source450including a segmented cathode452having an oval shape according to one embodiment of the invention. The segmented cathode452is formed in the shape of an oval to facilitate processing large workpieces, such as architectural pieces or flat screen displays. In other embodiments, the segmented cathode452is formed into other shapes that generate desired plasma profiles across a particular workpiece. In the embodiment shown inFIG. 7, the plasma source450is not a segmented magnetron, and therefore, the segmented cathode452does not include magnets. However, in other embodiments, the plasma source450is a segmented magnetron and the segmented cathode452does include magnets.

The segmented cathode452includes a plurality of cathode segments452a,452b, and452c. The plurality of cathode segments452a-cis typically electrically isolated from each other. Some embodiments include additional cathode segments that meet the requirements of a specific plasma process. In one embodiment, the segmented cathode452includes target material that is used for sputtering. The target material can be integrated into or fixed onto each cathode segment452a-c.

The plasma source450also includes a plurality of anodes454a,454b. The anodes454a,454bare positioned between the cathode segments452a,452b,452c. Additional anodes can be positioned adjacent to additional cathode segments. In one embodiment, the anodes454a,454bare coupled to ground105. In other embodiments (not shown), the anodes454a,454bare coupled to a positive terminal of a power supply.

An input456of the first cathode segment452ais coupled to a first output458of the switch110. An input460of the second cathode segment452bis coupled to a second output462of the switch110. An input464of the third cathode segment452cis coupled to a third output466of the switch110.

An input468of the switch110is coupled to a first output470of the power supply128. A second output472of the power supply128is coupled to ground105. In other embodiments (not shown), the second output472of the power supply128is coupled to the anodes454a,454b. The power supply128can be a pulsed power supply, a switched DC power supply, an alternating current (AC) power supply, or a radio-frequency (RF) power supply. The power supply128generates a pulse train of voltage pulses that are routed by the switch110to the cathode segments452a-c.

The power supply128can vary the magnitude, the pulse width, the rise time, the fall time, the frequency, and the pulse shape of the voltage pulses depending on the desired parameters of the plasma and/or the desired uniformity of a sputtered coating. The switch110can include a controller or a processor and can route one or more of the voltage pulses to each of the cathode segments452a-cin a predetermined sequence depending on the shape and size of the segmented cathode452and the desired uniformity of the coating, and the density and volume of the plasma. An optional external controller or processor (not shown) can be coupled to the switch110to control the routing of the voltage pulses in the pulse train.

The operation of the plasma source450is similar to the operation of the plasma source100ofFIG. 1. The switch110routes the voltage pulses from the power supply128to the particular cathode segments452a-cof the segmented cathode452. The size and shape of the segmented cathode452can be adjusted depending on the size and shape of the workpiece to be processed. The shape, pulse width, rise time, fall time, and frequency of the voltage pulses, as well as the sequencing of the various voltage pulses can be varied depending on the specific plasma process.

FIG. 8illustrates a diagram of a plasma source500including a segmented magnetron cathode502in the shape of a hollow cathode magnetron (HCM) according to one embodiment of the invention. The plasma source500includes at least one magnet assembly504athat is positioned adjacent to a third magnetron cathode segment502c. Additional magnet assemblies504b-hare positioned adjacent to fourth502d, fifth502e, and sixth magnetron cathode segments502f. The magnet assemblies504a-hcreate magnetic fields proximate to the magnetron cathode segment502a-f. The magnetic fields trap electrons in the plasma proximate to the magnetron cathode segments502a-f.

In some embodiments, the magnet assemblies504a-hare electro-magnetic coils. The shape and strength of the magnetic fields generated by the coils vary depending on the current applied to the coil. The magnetic fields can be used to direct and focus the plasma in the HCM. In some embodiments, one or more of the magnet assemblies504a-hgenerate unbalanced magnetic fields. The unbalanced magnetic fields can improve the plasma process as previously described.

A first anode508is positioned proximate to the first502aand the second magnetron cathode segments502b. The first anode508is coupled to a first output510of the power supply128. A second anode512is positioned proximate to the third magnetron cathode segment502cand is coupled to the first output510of the power supply128. A third anode514is positioned proximate to the fourth magnetron cathode segment502dand is coupled to the first output510of the power supply128. A fourth anode516is positioned proximate to the fifth magnetron cathode segment502eand is coupled to the first output510of the power supply128. A fifth anode518is positioned proximate to the sixth magnetron cathode segment502fand is coupled to the first output510of the power supply128. A sixth anode520is also positioned proximate to the sixth magnetron cathode segment502fand is coupled to the first output510of the power supply128. In other embodiments, the number of anode and magnetron cathode segments is different.

Each of the plurality of magnetron cathode segments502a-fis coupled to an output of the switch110. The plurality of magnetron cathode segments502a-fis typically electrically isolated from each other. However, there are embodiments in which two or more magnetron cathode segments502a-fcan be electrically coupled together.

A substrate or workpiece (not shown) is positioned adjacent to the segmented magnetron cathode502. The plasma source500can be used to coat the substrate. In this embodiment, each of the magnetron cathode segments502a-fincludes target material. The power supply128and the switch110control the voltage pulses applied to each of the magnetron cathode segments502a-fincluding the target material. The target material from each of the magnetron cathode segments502a-fsputter coats the substrate. Parameters of the power supply128, the switch110, and the magnet assembly504, can be adjusted to increase the uniformity of the sputtered coating and to adjust the density of the plasma to improve the plasma process.

FIG. 9illustrates a diagram of a plasma source550including a segmented magnetron cathode552in the shape of a conical cathode magnetron according to one embodiment of the invention. The plasma source550includes a first magnet assembly554athat is positioned adjacent to a first magnetron cathode segment552a. A second magnet assembly554bis positioned adjacent to a second magnetron cathode segment552b. A third magnet assembly554cis positioned adjacent to a third magnetron cathode segment552c. Each of the magnet assemblies554a-ccan generate magnetic fields having different strengths and different geometries that are chosen to optimize the specific plasma process.

The magnet assemblies554a-ccan include coils or can include permanent magnets. The first magnet assembly554acreates a magnetic field (not shown) proximate to the first magnetron cathode segment552a. The first magnetic field traps electrons in the plasma proximate to the first magnetron cathode segment552a. The second magnetic field (not shown) traps electrons in the plasma proximate to the second magnetron cathode segment552b. The third magnetic field (not shown) traps electrons in the plasma proximate to the third magnetron cathode segment552c. In some embodiments, one or more of the magnet assemblies554a-cgenerate unbalanced magnetic fields. The unbalanced magnetic fields can be used to optimize the particular plasma process.

A first anode556is positioned proximate to the first magnetron cathode segment552a. A second anode558is positioned proximate to the second magnetron cathode segment552b. A third anode560is positioned proximate to the third magnetron cathode segment552c. In one embodiment, the first556, the second558, and the third anodes560are formed in the shape of a ring. The first556, the second558, and the third anodes560are coupled to ground105.

A substrate562is positioned adjacent to the segmented magnetron cathode552. The plasma source550can be used to coat the substrate562. In this embodiment, each of the magnetron cathode segments552a-cincludes target material. The power supply128and the switch110control the voltage pulses applied to each of the magnetron cathode segments552a-cincluding the target material. The target material from each of the magnetron cathode segments552a-csputter coats the substrate. Parameters of the power supply128, the switch110, and the magnet assemblies554a-c, can be adjusted to increase the uniformity of the plasma to improve the plasma process.

For example, if the sputtered film on the substrate562is non-uniform such that the film is thicker on the edge564of the substrate562than in the center566of the substrate562, the switch110can route a greater number of voltage pulses to the first magnetron cathode segment552athan to the third magnetron cathode segment552cin order to increase the thickness of the sputtered film proximate to the center566of the substrate562. Alternatively, the switch110can route voltage pulses having longer pulse widths to the first magnetron cathode segment552aand voltage pulses having shorter pulse widths to the third magnetron cathode segment552c. Numerous other combination of applying different numbers of voltage pulses and/or voltage pulses having different pulse widths can be used.

Conversely, if the sputtered coating on the substrate562is non-uniform such that the film is thicker in the center566of the substrate562than on the edge564of the substrate562, the switch110can route a greater number of voltage pulses to the third magnetron cathode segment552cin order to increase the thickness of the sputtered film on the edge564of the substrate562. Alternatively, the switch110can route voltage pulses having longer pulse widths to the third magnetron cathode segment552cand voltage pulses having shorter pulse widths to the first magnetron cathode segment552a.

In addition, the power supply128can change the plasma density proximate to the various magnetron cathode segments552a-cby varying the rise times of the voltage pulses applied to the various magnetron cathode segments552a-c. For example, voltage pulses having very fast rise times can generate higher density plasmas that increase the sputtering rate of the target material.

FIG. 10illustrates a diagram of a plasma source600including a segmented magnetron cathode602in the shape of a plurality of small circular magnetron cathode segments602a-gaccording to one embodiment of the invention. The plurality of small circular magnetron cathode segments602a-gis surrounded by a housing603.

Each of the small circular magnetron cathode segments602a-gincludes a magnet assembly604a-g(only604b-dare shown for clarity) that generates a magnetic field606a-g(only606b-dare shown for clarity) proximate to each respective small circular magnetron cathode segment602a-g. The magnet assemblies604a-gcan include coils or can include permanent magnets. Each magnetic field606a-gtraps electrons in the plasma proximate to each respective small circular magnetron cathode segment602a-g. Alternative magnet assemblies can be used to generate magnetic fields across one or more of the small circular magnetron cathode segments602a-g. Each of the magnet assemblies604a-gcan generate magnetic fields having different strengths and geometries. One or more of the magnet assemblies604a-gcan also generate an unbalanced magnetic field.

The plasma source600also includes a power supply608. A first output610of the power supply608is coupled to an input612of a switch614. A second output616of the power supply608is coupled to ground105. The switch614includes multiple outputs618a-gthat are each coupled to a respective one of the small circular magnetron cathode segments602a-g. In one embodiment, the switch614includes an integrated controller or processor. The plurality of magnetron cathode segments602a-gare typically electrically isolated from each other, but two or more can be electrically coupled together in some embodiments.

Each of the small circular magnetron cathode segments602a-gis surrounded by a respective anode620a-g. In one embodiment, the anodes620a-gare formed in the shape of a ring. The anodes620a-gare coupled to ground105. In one embodiment, the anodes620a-gare coupled to the second output616of the power supply608.

A substrate (not shown) is positioned adjacent to the segmented magnetron cathode602. The plasma source600can be used to coat the substrate. In this embodiment, each of the small circular magnetron cathode segments602a-gincludes target material. The power supply608and the switch614control the voltage pulses applied to each of the small circular magnetron cathode segments602a-gincluding the target material. The target material from each of the small circular magnetron cathode segments602a-gsputter coats the substrate. Parameters of the power supply608, the switch614, and the magnet assemblies604a-g, can be changed to adjust the uniformity of the plasma to create customized thickness profiles.

For example, to sputter a thicker coating in the center of the substrate, the switch614can route a greater number of voltage pulses to the small circular magnetron cathode segment602ain the center of the segmented magnetron cathode602than to the other small circular magnetron cathode segments602b-gthat surround the center small circular magnetron cathode segment602a. The switch routing sequence in this example will increase the sputtering rate from the small circular magnetron cathode segment602aand will increase the thickness of the sputtered film proximate to the center of the substrate. Alternatively, the switch614can route voltage pulses having longer pulse widths to the center small circular magnetron cathode segment602aand voltage pulses having shorter pulse widths to the other small circular magnetron cathode segments602b-g. Any combination of applying different numbers of voltage pulses and/or voltage pulses having different pulse widths can be used. The switch614can route any number of voltage pulses to the various small circular magnetron cathode segments602a-g.

In addition, the power supply608can change the plasma density proximate to the various small circular magnetron cathode segments602a-gby varying the rise times of the voltage pulses that are applied to the various small circular magnetron cathode segments602a-g. For example, voltage pulses having very fast rise times that generate higher density plasmas that increase the sputtering rate of the target material can be applied to particular circular magnetron cathode segments602a-gto change the plasma density distribution.

FIG. 11illustrates a diagram of a plasma source650that includes a segmented magnetron cathode652having a plurality of concentric magnetron cathode segments652a-daccording to one embodiment of the invention. The concentric magnetron cathode segments652a-dare configured into multiple isolated hollow cathodes. The plasma source650also includes a first654and a second anode656that are ring-shaped. The anodes654,656can include multiple gas injector ports658. The gas injector ports658supply feed gas between the magnetron cathode segments652a-d. The pressure of the feed gas can be adjusted to optimize the plasma process. For example, in a reactive sputtering process, feed gas flowing across surfaces660a-dof the magnetron cathode segments652a-dcan prevent reactive gas from interacting with and damaging the surfaces660a-dof the magnetron cathode segments652a-d. In some embodiments, the gas injector ports658supply excited atoms such as metastable atoms between the magnetron cathode segments652a-d. The excited atoms can improve the plasma process by increasing the rate of ionization of the plasma and the density of the plasma.

The segmented magnetron cathode652also includes groups662a-cof magnets664that are positioned in rings around each of the magnetron cathode segments652a-d. Each of the magnets664are positioned with their magnetic poles aligned in the same direction. The magnets664generate magnetic fields666having magnetic field lines668. The magnetic fields666repel each other causing the magnetic field lines668to become more parallel to the surfaces of the magnetron cathode segments652a-d. The parallel magnetic field lines can improve target utilization in sputtering processes in which the magnetron cathode segments652a-dinclude target material. The parallel magnetic field lines can also improve ion bombardment of the target material because a substantial portion of the plasma is trapped close to the surfaces of the magnetron cathode segments652a-dwhere the target material is located.

In one embodiment, at least two of the magnetron cathode segments652a-dhave different shapes and/or areas that are chosen to improve the uniformity of the coating. Additionally, in one embodiment, at least two of the magnetron cathode segments652a-dhave different target materials that are used in a compound sputtering process. The plasma source650can also be used for ionized physical vapor deposition (I-PVD).

FIGS. 12A-12Dillustrate four segmented cathodes700,700′,700″,700′″ having various shapes according to the invention. The first segmented cathode700illustrated inFIG. 12Aincludes two cathode segments702,704that are substantially parallel to each other. The surfaces706,708,710, and712of the segmented cathode700can include target material for sputtering. Alternatively, the segmented cathode700can each be formed from a target material. An anode714is positioned proximate to the segmented cathode700. A plasma can be ignited by generating a discharge between the anode714and the segmented cathode700. The anode714can include one or more gas injector ports716. The injector ports716can supply feed gas between the two cathode segments702,704. The injector ports716can also supply excited atoms such as metastable atoms between the two cathode segments702,704.

FIG. 12Billustrates the second segmented cathode700′. The second segmented cathode700′ includes a substantially U-shaped cathode segment720. The U-shaped cathode segment720can include target material positioned on each of the inside surfaces722,724,726. In one embodiment, the U-shaped cathode segment720is formed from the target material. The U-shaped cathode segment has a larger surface area and provides more target material as compared with the first segmented cathode700ofFIG. 12A. An anode728is positioned proximate to the second segmented cathode700′. A plasma can be ignited by a discharge between the anode728and the second segmented cathode700′.

FIG. 12Cillustrates the third segmented cathode700″. The third segmented cathode700″ is similar to the first segmented cathode700, except that the two cathode segments730,732are positioned non-parallel relative to each other. The non-parallel configuration can improve a sputtering process by exposing a larger surface area of target material towards the substrate (not shown). An anode734is positioned proximate to the segmented cathode700″. A plasma can be ignited by a discharge between the anode734and the segmented cathode700″. The anode734can include one or more gas injector ports736that supply feed gas between the two cathode segments730,732.

FIG. 12Dillustrates the fourth segmented cathode700′″. The fourth segmented cathode700′″ is similar to the second segmented cathode700′, except that the cathode segment740is substantially V-shaped. The V-shaped cathode segment740can include target material on each of the inside surfaces742,744. An anode746is positioned proximate to the fourth segmented cathode700′″. A plasma can be ignited by a discharge between the anode746and the fourth segmented cathode700′″.

In one embodiment of the present invention, thin films are engineered to achieve certain mechanical, electrical, and/or magnetic properties of the deposited film by controlling the ratio of total ions (NI) to neutral atoms (NN) in the plasma volume. In some embodiments, at least two thin film layers are deposited using different ratios of total ions (NI) to neutral atoms (NN) in the plasma volume of each film.

Substrate bias can also be used to engineer the deposited films. The DC or radio-frequency (RF) bias applied to the substrate141(FIG. 2A) by the power supply142controls the energy of the ions impacting the substrate141. In various embodiments, the bias voltage applied to the substrate141by the power supply142is a DC voltage, a voltage pulse or an RF signal that is chosen to change the energy of ions impacting the surface of the substrate to achieve a certain mechanical, electrical, and/or magnetic properties of the deposited film. For example, in one embodiment, the substrate is negatively biased with a DC voltage in the range between 0 V and −5000 V.

In addition, the temperature of the substrate can be selected to achieve a certain mechanical, electrical, and/or magnetic property of the deposited film. The substrate temperature determines the mobility of atoms in the growing film. By controlling the mobility of the atoms in the growing film, the properties of the deposited thin film can be changed.

There are numerous applications of such engineered thin films. For example, thin films can be engineered according to the present invention which provides a specialized hard coating for various applications, such as for cutting tools and razor blades.

Referring toFIGS. 1, 2A, 3fand3G, in one experiment, a modulated TiN film structure was formed by alternating between applying the first train of voltage pulses285to the magnetron cathode102and applying the second train of voltage pulses296to the magnetron cathode102one hundred times. The ratio of total ions (NI) to neutral atoms (NN) in the plasma volume was in the range of 0.9 and 0.5. The substrate bias was −50 V. The substrate temperature was 200 degrees C. A total sputtered film thickness of 1500 Å was achieved. The resulting film had a hardness of more than 35 GPa.

EQUIVALENTS