CN101265580A - Sputtering target pretreatment before sputtering - Google Patents

Abstract

The present invention discloses a method for pre-treating a sputtering target before it is used in a sputtering process by removing a damaged surface layer of the sputtering surface of the sputtering target. In one approach, the sputtering surface of the sputtering target is ground to remove a thickness of at least about 25 microns, resulting in a sputtering surface having an average surface roughness in the range of about 4 to about 32 microinches. In another approach, the layer is removed using an acidic etchant. In another approach, the damaged surface layer is annealed by heating the surface.

Description

Sputtering target pretreatment before sputtering

related application

This application is filed as a non-provisional application and claims priority to provisional application number 60/782,740, filed March 14, 2006, which is hereby incorporated by reference in its entirety.

technical field

Embodiments of the present invention relate to pre-treating a sputter target prior to use in a sputter process.

Background technique

In the manufacture of electronic circuits and displays, sputtering chambers are used to sputter deposition materials onto eg substrates, such as semiconductor wafers or displays. The sputtering chamber uses a sputtering target mounted in the chamber. The target comprises a sputtering surface consisting of a sputtering material, which may be, for example, a metal such as aluminum, copper, tantalum, titanium or tungsten. Compounds such as sputtered materials, eg, tantalum nitride, titanium nitride, and tungsten nitride, may also be deposited into the chamber. Typically, the chamber comprises an enclosure for enclosing the process region into which the process gas is introduced, a gas energizer for exciting the process gas to form a plasma, and an exhaust for exhausting the gas and controlling the pressure of the gas within the chamber. breath. In the sputtering process, a sputter target is bombarded by energetic plasma species, causing material to be sputtered away from the target and deposited onto the substrate.

However, the manufacturing process used to form a sputtering target often produces a damaged surface layer of the target, which can result in undesirable or inconsistent sputtering properties. Typically, the sputter target is machined into a disc shape by mechanical processes such as lathing or milling. These machining processes create shear forces on the surface of the target, thereby plastically deforming the surface grains and causing other defects in the surface grains. In plastic deformation, adjacent faces of atoms within each grain slide against each other, causing permanent lateral movement of the lattice faces relative to each other, resulting in a smeared grain structure. Typically, damaged surface layers also have a higher dislocation density. In a sputtering process, grain defects in a sputtering target affect the distribution of target material sputtered from the target. Damaged grains or surface layers with higher dislocation density lead to variable or non-uniform sputtering properties across the target surface. For example, a damaged surface layer may cause a change in the sputtering rate from the sputtering target until the surface grains are sputtered away from the target. This results in the deposition of non-uniform thicknesses of sputtered material on different substrates of a batch of substrates being processed, non-uniform deposition over the entire surface of a single substrate. Another problem arises when the sputtering surface of the target reacts with the surrounding or external environment to form an undesired surface layer affecting its sputtering properties. For example, sputtering target materials react with oxygen in the surrounding air to form an oxidized surface layer.

In order to remove the undesired damaged surface layer of the sputter target, a burn-in process step is typically performed after the sputter target has been installed in the sputter chamber. In the burn-in process, the sputtered surface of the target is exposed to a plasma to sputter off undesired surface layers of the target. For example, a target aging process step may be performed with a 150 kW-hour plasma to remove sufficient thickness of the target surface to provide a more uniform sputtering rate when the target is subsequently used in a production process. However, the target aging process takes time to complete, during which time the sputtering chamber cannot be used for production. Inefficient utilization of the sputtering chamber increases processing costs. Therefore, there is a need for a process for removing damaged surface layers on sputtering targets that is more efficient and does not affect the use of the sputtering chamber over extended target aging times.

Contents of the invention

The present invention provides several methods for removing or repairing damaged surface layers on sputtering targets. One method involves mechanically polishing away the damaged surface layer from the surface of the target. Another method involves etching away the damaged surface layer from the surface of the target. Yet another method includes repairing the damaged surface layer of the target by heating the surface layer to a temperature of at least about 400°C. Yet another method involves sputtering the damaged surface layer off the sputtered surface by applying a pulsed current and arcing the damaged layer away from the surface.

These methods can be used to remove or repair damaged surface layers on a sputter target without interfering with the use of the sputter chamber during extended target aging times.

Description of drawings

These features, aspects and advantages of the present invention will be better understood from the following description, appended claims and accompanying drawings, which illustrate embodiments of the invention. However, it should be understood that individual features may be used in the present invention in general, not limited to the context of a particular drawing, and that the present invention includes any combination of these features, wherein:

1 is a cross-sectional side view of an embodiment of a sputtering target having a sputtering surface;

2A is a partial cross-sectional side view of an embodiment of a sputtering target having a sputtering surface with a damaged surface layer;

2B is a partial cross-sectional side view of the sputtering target of FIG. 2A after removal of the damaged surface layer from the sputtering surface;

3 is an X-ray diffraction diagram of a sputtering surface of a sputtering target, which shows X-ray diffraction peaks obtained by different diffraction angles;

4A is a schematic diagram of an embodiment of a polishing apparatus for polishing a sputtering surface of a sputtering target;

4B is a schematic diagram of another embodiment of a polishing apparatus for polishing a sputtering surface of a sputtering target;

5 is a partial cross-sectional view of an embodiment of an acid etchant tank and a fixture for holding a sputtering target in the tank;

Figure 6 is a schematic view of a laser beam apparatus for laser processing a sputtering surface of a sputtering target;

Fig. 7 is the schematic diagram of electrical discharge machining equipment;

8 is a cross-sectional view of an embodiment of a sputtering chamber capable of using a sputtering target; and

9 is a schematic diagram of an electrolytic polishing apparatus for electrolytic polishing of a sputtering target.

Detailed ways

FIG. 1 shows an embodiment of a sputter target 20 capable of sputtering deposition material onto a substrate 104 . Target 20 includes a sputtering plate 22 composed of a sputtering material, wherein the sputtering material may comprise, for example, a metal, eg, at least one of titanium, tantalum, tungsten, or an alloy comprising one of these elements or another metal. Sputtering plate 22 includes a sputtering surface 24 from which material may be removed to deposit material onto substrate 104, eg, by sputtering with an energetic gas. Sputter plate 22 may be fabricated by any suitable method, including, for example, chemical vapor deposition, casting, physical vapor deposition, electroplating, hot isostatic pressing, and others. For the processing of circular semiconductor wafers, sputter plate 22 is typically disc-shaped. Sputter plate 22 may also have a diameter in the range of about 200 mm to about 500 mm, and a thickness in the range of about 2.5 mm to about 25 mm. However, sputter target 20 is not limited to a particular geometry, but may have other shapes or other dimensions depending on the shape of substrate 104 . For example, sputter target 20 may be rectangular or square for processing displays and rectangular substrates. In another solution, the sputtering target 20 also includes a ring coil 25 (as shown in FIG. 8 ), which is mounted on the side wall of the chamber 106 and located on the top of the sputtering plate 22 mounted on the top of the chamber 106. around. Both the top mounted sputtering plate 22 and the sidewall mounted toroidal coil 25 comprise a sputtering surface 24 and both serve as sputtering targets 20 in this arrangement.

In one aspect, sputtering target 20 includes sputtering plate 22 mounted on a backing plate 26 for supporting sputtering plate 22 on top of sputtering chamber 106 . Typically, the back plate 26 is composed of a metal such as copper or a metal alloy such as a copper-zinc alloy, which provides good heat conduction to allow the sputter plate 22 to cool during the sputtering process. Back plate 26 includes a peripheral ledge 27 disposed on an annular ring within sputtering chamber 106 . The back side 29 of the backing plate 26 also contacts a heat exchanger in the chamber to further cool the sputtering plate 22 during the sputtering process. Typically, sputter plate 22 is diffusion bonded to back plate 26 . The sidewall mounted loop coil 25 may also have a sputtering surface 24 to provide sputtered species deposited around the peripheral region of the substrate 104 to provide better or more uniform sputtered material.

Processing of substrate 104 using sputtering target 20 (which may be sputtering plate 22 or loop coil 25 ) is improved by pre-treating target 20 by removing a thickness of sputtering surface 24 including damaged surface layer 32 . For example, as shown in FIG. 2A , in some targets, the damaged surface layer 32 consists primarily of plastically deformed grains 28 forming a "smearing" surface grain structure along the sputtering surface 24 . Underneath the trailing grain structure 28 remain undeformed grains 30 which generally provide better or more uniform sputtering characteristics. The damaged surface layer 32 may also have, or alternatively only have, a high dislocation density. The thickness of damaged surface layer 32 on the surface of target 20 depends on the grain size of the target and is typically at least about 25 microns, more typically about 50 microns to about 300 microns. Sputtering surface 24 may also have a metal oxide or other layer (not shown) formed on the exposed surface.

FIG. 3 is an X-ray diffraction pattern of sputtering surface 24 of sputtering target 20 showing X-ray diffraction peaks as a function of diffraction angle. When the damaged surface layer 32 contains plastically deformed crystal grains 28, the distance between the crystal planes differs from one crystal grain to another, thereby broadening the diffraction peak. The FWHM (full width at half maximum) of the diffraction peak at a 2Θ angle of about 38° is a measure of non-uniform microstrains caused by plastic deformation of crystal planes. Larger FWHM values indicate higher strain levels and greater degrees of change in the crystal plane positions of trailing grains 28 . After initial processing, as shown in Figure 3, it can be seen that the FWHM of the sputtered surface is about 0.69. When the damaged surface layer 32 is substantially removed from the sputtering surface 24, as shown in FIG. 2B, the underlying undeformed grains 30 are exposed on the sputtering surface 24, and the FWHM of the diffraction peak decreases to below about 0.4 .

In one version of the process, as shown in FIG. 2B, after machining the shape of the target on the lath, the sputtering surface 24 of the sputtering plate 22 is polished by a polishing process in a polishing apparatus 34 to substantially remove the sputtering surface 24. The entire damaged surface layer 32 and expose the underlying undeformed grains 30 or grains with lower dislocation density. In one version of the process, as shown in FIG. 4A , the target 20 is held on a lapping wheel 40 while a polishing slurry 42 is applied to the wheel 40 from a slurry distributor 44 including a slurry supply 46 . The wheel 40 and target 20 are rotated opposite each other to rub away the exposed surface 24 of the sputter plate 22 . The polishing process is typically a low pressure, low speed operation to obtain a good surface finish of the sputtering surface 24 . The slurry includes abrasive particles having a predetermined range of particle size and hardness. Sputtering surface 24 is polished to remove a thickness of surface 24 sufficient to remove plastically deformed grains and any surface oxide layer. For example, sputtering surface 24 of sputtering target 20 may be polished to remove layer 32, which may have a thickness of at least about 25 microns, and obtain a sputtering surface having an average surface roughness in the range of about 4 to about 32 microinches.

In one embodiment of the polishing method, the target 20 is placed on the grinding wheel 40, and the weight of the sputtering target 20, including the sputtering plate 22 and the backing plate 26, firmly presses the sputtering surface 24 against the grinding plane of the wheel 40. superior. Grinding wheel 40 may be mounted to a platform of load bearing wheels 48 that minimize shock and vibration during rotation or oscillation of wheel 40 . As the target 20 and the grinding wheel 40 are pressed against each other and rotate, a polishing slurry 42 of abrasive particles is introduced between the two surfaces. The target 20 moves toward and is stopped by a pair of roller cylinders 50a and 50b supported by a mounting plate 52 . The polished flatness of the sputtering surface 24 is controlled by the grain size of the abrasive particles. The abrasive particles may be particles of aluminum oxide, corundum or even diamond particles. More suitably, the abrasive slurry 42 of abrasive particles comprising diamond particles having a size of about 2 to 12 microns, eg 6 microns, is suspended in a medium, such as deionized water. In one embodiment, the FWHM of the X-ray diffraction peak at 38° of the sputtering surface 24 is reduced to about 0.48 when tested after polishing with a slurry 42 comprising diamond particles having a size of 6 microns for about 30 minutes , which represents an improvement of about 30% over the original FWHM value of 0.69.

Although one type of polishing process has been described, it should be understood that other polishing methods may also be used. For example, sputtering surface 24 of target 20 may also be polished in a slat (not shown) using a suitable polishing or grinding tool attached to the slat while substrate 20 is rotated about its axis. Equally, other schemes of the polishing process can also be used, for example, as shown in FIG. 4B , the sputtering surface 24 of the target 20 can be held upward, and the polishing brush 47 can be pressed downward against the sputtering surface 24 along the sputtering surface 24. for polishing. In this approach, brush 47 and sputtering surface 24 rotate or oscillate relative to each other as polishing slurry 42 of diamond particles is added from polishing slurry dispenser 44 containing slurry supply 46 .

In another polishing process scheme, an electrochemical polishing process is used, wherein during polishing, a current is applied to the sputtering surface 24 of the target 20 using a power supply 56 . Current may be applied through first brush electrode 57 in contact with target 20 and second brush electrode 59 in contact with polishing slurry 42 . A current of approximately 5 to 70 mAmps/cm ² is applied to the target 20 . In this version, the polishing slurry 42 is a conductive solution comprising an acid solution such as HF acid and mixtures thereof with other acids. Advantageously, the electrochemical polishing process provides better removal of the plastically deformed layer 32 due to the application of electric current as well as chemical and mechanical polishing.

In yet another aspect, as shown in FIG. 9 , an electrolytic polishing apparatus 300 is used to remove the damaged surface layer 32 from the sputtering surface 24 of the target 20 . During the electrolytic polishing process, the target 20 is immersed in an electrolytic solution 302 within an electrolytic polishing bath 304 . Depending on the target material, electrolytic solution 302 may be an acid solution, such as a dilute solution of HCl, HNO ₃ or H ₂ SO ₄ or a mixture thereof. Electropolishing power supply 312 is used to apply voltage to sputter target 20 serving as an anode while also immersing cathode 306 in solution 302 . In one embodiment, the sputtering surface 24 of the tantalum target 20 may be etched by applying a direct current in the range of from about 5 to about 75 volts, such as about 50 volts. Through solution 302, electropolishing power supply 312 provides a current of up to 100 mAmps, eg, from about 5 to 70 mAmps/ ^cm2 , based on the area of sputtering surface 24 to be electropolished. In one embodiment, the electrolytic solution 302 includes alcohol, such as methanol or ethanol, with added sulfuric acid. The volume ratio of alcohol to acid may be from about 5:1 to about 40:1, for example 20:1. Other acids such as HF may also be added to the electrolytic solution 302. In electrolytic polishing apparatus 300, for an anode comprising tantalum target 20, cathode 306 may be made of stainless steel. Also, preferably, the backside 29 of the target 20 is masked by a masking fixture 310 as shown, to protect the backside 29 material which would otherwise be corroded by the electrolytic solution 302 .

In another approach, the sputtering surface 24 of the sputtering target 20 is etched by an acidic etchant to remove the damaged layer 32 , which may be used with or without polishing the sputtering surface 24 . One method of etching the sputtering surface of a sputtering target includes immersing the sputtering surface 24 of the target 20 in an acidic etchant 58 comprising a mixture of hydrofluoric acid and nitric acid. The hydrofluoric acid may have a concentration of about 10% to about 52% by weight, for example, about 49.5% by weight. Nitric acid may have a concentration of about 50% to about 80% by weight, for example, about 69.5% by weight. A suitable ratio of hydrofluoric acid to nitric acid is from about 15% to about 20% by volume. In one approach, such as shown in FIG. 5 , an acidic etchant 58 is provided in a tank 60 and the target 20 is immersed in the etchant 58 . The acid etchant 58 may be contained in a tank 60 with a circulation pump and optionally a filtration system (not shown) to remove filter residue from the acid etchant 58 . Acid etchant 58 in tank 60 may also be agitated, for example, by superwave vibrations provided by an ultrasonic oscillator (not shown) attached to the tank 60 wall. Other methods of agitation, including mechanical propeller agitation, can also be used to agitate the acid etchant 58.

Clamp 68 may be used to secure sputter target 20 in contact with acid etchant 58 without exposing backing plate 26 to acid mist. A suitable clamp 68 includes a base plate 70 and a circular clamp ring 72 secured to the base plate by screws 74 . The target 20 is disposed on a base plate 70 and a circular clamping ring 72 is secured to the base plate by a screw 74 . The assembled fixture 68 is then flipped over to expose the sputtering surface 24 of the sputtering plate 22 to the acid etchant. O-ring seal 76 seals backside 29 and backplate 26 of target 20 from acid etchant 58 . Clamp 68 may be made of TEFLON ^(TM) , polytetrafluoroethylene (PTFE), fluorinated ethylene polymer, or a high density polyurethane material available from Dupont de Nemours, Delaware, USA. Polyurethane tubing 78 may also be used to pass an inert gas, such as argon or nitrogen, to the back side 29 of the backing plate 26 .

In one embodiment, the FWHM of the (38°) peak of the sputtered surface 24 is reduced to about 0.49 after chemically etching the sputtered surface 24 in an acid etchant ₅₈ comprising HF and HNO for about 30 minutes at room temperature, This again represents an improvement of approximately 30% over the original FWHM value of 0.69. In another embodiment, the FWHM of the (38°) peak of the sputtered surface 24 is reduced to about 0.46 after chemical etching of the sputtered surface 24 at room temperature for about 180 minutes in an acid etchant ₅₈ comprising HF and HNO , which again represents an improvement of approximately 30% over the original FWHM value of 0.69. Thus, the chemical etching significantly removes the damaged layer 32 of the sputtering surface 24 .

In another chemical etching protocol, the chemical etchant containing tank 60 is heated in a water bath 64, alternately heated by heater 62, to maintain the temperature of tank 60 at least about 50°C. It was determined that this temperature provided an etch rate approximately 5 times faster than the room temperature etch rate. Pot 60 may include a water bath 64 to maintain the temperature within a tightly controlled range, eg, ±2° C., for optimal etching of sputtering surface 24 of target 20 . Since the etching reaction is an exothermic reaction, it is desirable to precisely control the temperature of the acid etchant 58 to prevent the etching reaction from proceeding too quickly. The sputtered surface 24 of the target 20 is exposed to the acidic etchant for a period of about 90 to about 180 minutes.

In yet another approach, the sputtering surface 24 of the target 20 is first ground to obtain a surface roughness of about 4 to about 32 microinches. Typically, sputtering surface 24 is abraded to remove a thickness of at least about 25 microns, or more typically a thickness in the range of about 25 to about 300 microns. Thereafter, the sputtered surface 24 is chemically etched in an acid etchant to remove about 25 to about 200 microns of additional thickness. The initial polishing process smoothes the sputtering surface 24 so that the subsequent chemical etching process (smoothing the surface) produces an acceptable surface roughness and provides consistent sputtering properties of the target 20 in the sputtering chamber 106 . In such an embodiment, the sputtering surface 24 is polished for about 15 minutes with a polishing slurry 42 comprising diamond particles having a size of 6 microns. Thereafter, the ground target 20 was chemically etched in the acidic etchant solution described above for about 60 minutes. The FWHM of the (38°) peak of the sputtered surface 24 is reduced to about 0.39, which represents an improvement of about 40% over the original FWHM value of 0.69. In another embodiment, the sputtering surface 24 is abraded and polished for about 15 minutes with a polishing slurry comprising diamond particles having a size of about 6 microns. Thereafter, the ground target 20 is chemically etched in an acidic etchant solution for about 120 minutes. The FWHM of the (55°) peak of the sputtering surface 24 of the target 20 is reduced to about 0.4.

After polishing, etching, or any other surface treatment process, the surface roughness of the sputtering surface 24 of the sputtering plate 22 may be measured using a profilometer (not shown). The surface properties are useful for characterizing the properties of the grains 28 on the sputtering surface 24 . For example, the surface average roughness, which is the average of the absolute value of the displacement along the surface 24 from the centerline of the peaks and valleys of the roughness features, can be used as a rough measure of the smoothness of the surface 24 . A surface that is too rough is undesirable because it provides undesirable variability in the sputtering process. A profilometer typically consists of a probe mounted on a surface transverse arm attached to a cylinder and driven by a motor. Probes are interchangeable with different protocols for different surface properties or measurements. The cylinder is mounted on a stable base, such as a heavy metal or granite platform. The surface properties of the sputtered surface 24 are measured by dragging a probe over the evaluation length of the surface 24 . As the probe moves up and down contacting the sputtering surface 24, it produces a surface profile signal trace with highly fluctuating roughness on the surface, which signal trace is transmitted to a sensor such as an inductive sensor to convert the vibration of the probe into a sensor signal, and then processed by a computer. The selected sample length and signal trace are used to determine a set of surface profile numbers corresponding to different locations on the surface, and are also used to provide a visual surface profile trace on the display. A suitable surface profiler is a FormTalysurf Model 12 Probe Profiler from Taylor Hobson, Leicester, England. A scanning electron microscope, which uses a beam of electrons reflected from surface 24 to produce an image of that surface, may also be used. In one measurement method, the sputtering plate 22 is cut into a plurality of test pieces and a plurality of measurements are performed on each test piece. The surface roughness measurements are then averaged to determine the surface 24 average. In one embodiment, three test pieces are used, and four surface profile traces of height variation in peak-to-valley roughness are provided for each test piece. In one approach, a suitable average roughness value can be determined to be, for example, from about 4 to about 32 microinches. These measurements were made using the international standard ANSI/ASME B.46.1-1995, which specifies appropriate fixed-point lengths and evaluation lengths.

In yet another embodiment, an energy source such as a laser beam or lamp is used to heat the sputtering surface 24 of the target. The characteristics of the energy source, such as focal length, beam shape, and beam diameter, are set to selectively heat damaged surface layer 32 of sputtering surface 24 to a temperature sufficient to anneal grains 28 . In one embodiment, an energy source is used to heat the sputtering surface 24 to a deep thickness of less than 300 microns, more particularly less than 200 microns. For example, a focused laser beam can be used to selectively heat the localized surface 24 of the sputter plate 22 to a temperature sufficient to reduce the dislocation density in the damaged layer 32 without unduly increasing the overall temperature of the entire target 20 . A suitable temperature for reducing dislocations is at least about 400°C. Typically, the annealing temperature is less than 2/3 of the melting point of the material of the sputtering surface 24 . For example, the temperature may be from about 400°C to about 1000°C. In another embodiment, a suitable temperature for sputtering surface 24 comprising tantalum having a melting temperature of about 3017°C is about 600°C. The local thermal energy provided by the laser to the damaged surface layer 32 of the sputtering surface 24 causes softening and melting of the localized heated regions, causing dislocations in the layer 32 to move within the grains to reduce mechanical damage and strain. After heating the damaged surface layer 32 of the sputtering surface 24 to anneal it, rapid quenching may occur simply by conducting heat from the surface to the surrounding environment.

Annealing of the grains in the sputtering surface 24 of the sputtering plate 22 may be performed using a laser annealing apparatus 80 , an exemplary embodiment of which is shown in FIG. 6 . Laser annealing apparatus 80 includes a laser 82 within a laser beam enclosure 84 . Powered by and controlled by a controller 86 , laser 82 may also include a scanning mechanism 88 to scan laser beam 90 across sputtering surface 24 . Suitable lasers 82 that may be used include, for example, Ar, CO ₂ and KrF lasers. Argon lasers emit at a visible wavelength of about 5145 Angstroms. The _CO2 laser is an infrared energy source with a wavelength of 10.6 μm and can provide a beam with an energy level of 10 kilowatts. _CO2 lasers are more than 100 times more efficient and have higher intensity than argon lasers, allowing faster scan speeds and larger spot sizes compared to argon lasers. Another type of laser is a KrF excimer laser with a wavelength of about 248 nm, an Eg of 5.0 eV, an efficiency of about 3%, and an output energy of 350 mJ. Laser beam 90 is typically a circular beam having a beam diameter of less than about 10 nm, more typically about 0.5 mm to about 4 mm. A suitable laser beam 90 may have a wavelength from about 190 nm to about 10,600 nm. The laser 82 is typically operated at a power level of about 50 watts to about 2000 watts.

Although laser beam annealing is described as an exemplary annealing process, other surface annealing processes may also be used. For example, an alternative annealing process includes a rapid thermal annealing system using a set of lamps, such as quartz lamps, to heat the sputtering surface 24 of the target 20 . In one approach, the annealing process is performed by heating the sputtering surface 24 by irradiating infrared light directly onto the sputtering surface 24 of the target 20, for example, via a set of quartz lamps mounted above the target 20 in a rapid thermal annealing chamber. . The target 20 may also be heated by placing a heater, such as a resistive heater adjacent to the target, or by placing the target in a furnace. The radiant heat energy rapidly heats sputtering surface 24 to reorient and/or regenerate plastically deformed grains 28 in surface 24 . Radiant energy may also be scanned across the surface 24 of the target 20 to provide the desired thermal treatment. Yet other heating methods and systems include plasma stream heating, arc heating, and flame heating. Therefore, the scope of the present invention should not be limited to the exemplary schemes described herein, and the present invention also includes other partial surface annealing processes and equipment, which will be apparent to those of ordinary skill in the art.

The annealing process can also be used in conjunction with other processes described herein. In one embodiment, after machining the target 20, the sputtering surface 24 of the target 20 is polished using a polishing process. After the polishing process, the sputtering surface 24 of the target 20 is etched in the acidic etchant 58 as described. Thereafter, the sputtering surface 24 of the target 20 is annealed by heating it to a temperature of about 400°C to 1000°C. Combining polishing, etching, and annealing, it is expected to provide a target 20 with a lower defect amount and fewer damaged surface grains 28 .

In another method, known as electrical discharge machining (EDM), the layer of plastically deformed grains on the sputtered surface 24 may be removed by electrical discharge. As shown in FIG. 7 , in a typical EDM apparatus 200 , a high frequency spark discharge from an electrode 202 is used to break down the conductive material of the sputtering surface 24 to remove the layer of the sputtering plate 22 having plastically deformed grains 28 . In this contemplated embodiment, the electrode 202 and sputtering surface 24 are immersed in the insulating material 204 in the tank 210, and the electrode movement mechanism 206 is used to maintain the spark between the electrode 202 and the target 20 by about 0.013 to about 0.5 mm Gap. The electrode movement mechanism 206 , which may be a screw thread or a hydraulic cylinder, is used to move the electrode 202 vertically up and down across the surface 24 and also to set the size of the gap between the electrode 202 and the sputtering surface 24 . The spark formed in the gap melts or vaporizes small particles of the target 20 which are washed away as the electrode 202 travels over the surface 24 . Electrode 202 removes material from sputtering surface 24 using electric discharges, each spark generating a temperature between 10,000 and 20,000°C. The resulting arc erodes away portions of the sputtering surface 24 as the electrode 202 moves across the sputtering surface. In one version, the electrode 202 is a metal wire, such as Al, Cr, Cr/Ni, Cu/Co, Cu/Mn, Cu/Sn, Cu/W, Ni, Ni/Co, Ni/Fe, Ni/Mn, Ni/Si, Ti, Ti/Al, TiC/Ni, W/CrC/Cu or WC/Co, where copper wire is typically used. EDM can use die-sinking or wire-sinking, where die-sinking uses machined graphite or copper electrodes to burn the sputter plate 22 into the desired shape, and wire-sinking uses very fine wire to cut the sputter plate 22. damaged portion of the firing surface 24.

During the EDM process, the discharge power supply 208 maintains the electrode 202 at a negative polarity while applying a positive polarity to the sputter plate 22 at a voltage of, for example, about 100 to about 400 volts. Controller 212 controls power supply 208 to apply low pulse current to electrode 202 at steady repeat intervals while also controlling electrode movement mechanism 206 to move electrode 202 across sputtering surface 24 . The power supply 208 may include a pulsed current generating power unit that controls the generated current to form pulses. For example, the power supply 208 may generate pulses of 1000 Amp current at intervals of less than one microsecond during the discharge process. In finishing, the pulse can be set to a nanosecond duration level to stably and repeatedly generate a small pulse current.

In one approach, in the embodiment shown in FIG. 8 , after pretreatment, a sputtering target 20 may be used in the sputtering chamber 106 to sputter deposit layers, such as tantalum, tantalum nitrogen, etc., on the substrate 104 . One or more of aluminum, aluminum nitride, titanium, titanium nitride, tungsten, tungsten nitride, and copper. A substrate holder 108 is provided in the chamber 106 to support the substrate 104 . A substrate 104 is introduced into the chamber 106 through a substrate loading port (not shown) in a side wall of the chamber 106 and placed on a holder 108 . The stand 108 may be raised or lowered by stand lift bellows (not shown).

Sputtering gas supply 103 introduces sputtering gas into chamber 106 to maintain the sputtering gas in process region 109 at sub-atmospheric pressure. Sputtering gas is introduced into chamber 106 through gas inlet 133, which is connected to one or more gas sources 124 and 127 through gas inputs 125a and 125b, respectively. One or more flow controllers 126 are used to control the flow rates of the gases, which may be premixed in the mixing manifold 131 or introduced separately into the chamber 106 prior to introduction into the chamber 106 . The sputtering gas, typically comprising a non-reactive gas such as argon or xenon, which when energized will form a plasma, vigorously strikes and bombards the target 20 to sputter material from the target 20 . The sputtering gas may also contain reactive gases, such as nitrogen. Likewise, other compositions of sputtering gases including other reactive gases or other types of non-reactive gases may be used as will be apparent to those of ordinary skill in the art.

Exhaust system 128 controls the pressure of the sputtering gases in chamber 106 and exhausts excess and by-product gases from chamber 106 . Exhaust system 128 includes an exhaust port 129 in chamber 106 that is connected to an exhaust line 134 that leads to one or more exhaust pumps 139 . A throttle valve 137 in exhaust line 134 may be used to control the pressure of the sputtering gas within chamber 106 . Typically, the pressure of the sputtering gas within chamber 106 is set to sub-atmospheric pressure.

Sputtering chamber 106 includes sputtering target 20 opposite substrate 104 to deposit material on substrate 104 . The sputtering chamber 106 may also have a shield 120 to protect the walls 112 of the chamber 106 from the sputtered material, which shield 120 may also serve as a ground plane. The target 20 may be electrically isolated from the chamber 106 and connected to a power source 122, such as a DC or RF power source. In one aspect, the power supply 122 , target 20 and shield 120 operate as a gas energizer 190 capable of exciting a sputtering gas to sputter material from the target 20 . Power source 122 may electrically bias target 20 relative to shield 120 to excite sputtering gases within chamber 106 to form a plasma that sputters material from target 20 . The material sputtered from the target 20 by the plasma is deposited onto the substrate 104 and may react with the gas components of the plasma to form a sputter-deposited layer on the substrate 104 .

Chamber 106 may further include a magnetic field generator 135 that generates magnetic field 105 proximate target 20 to increase ion density in high density plasma region 138 proximate target 20 to improve sputtering of the target material. Additionally, a modified magnetic field generator 135 may be used to allow for sustained self-sputtering of copper or sputtering of aluminum, titanium, or other metals; while minimizing the need for non-reactive gases for target bombardment, e.g., in grants to Fu And U.S. Patent No. 6,183,614 entitled "Rotating Sputter Magnetron Assembly (rotating sputtering magnetron device)" and granted to Gopalraja et al. and entitled "Integrated Process for Copper Via Filling )” in U.S. Patent No. 6,274,008, which are incorporated herein by reference in their entirety. In one aspect, magnetic field generator 135 generates a half helical magnetic field at target 20 . In another aspect, the magnetic field generator 135 includes a motor 306 to rotate the magnetic field generator 135 about an axis of rotation.

The chamber 106 may be controlled by a chamber controller 54 that includes program code with an instruction set to operate the components of the chamber 106 to process the substrate 104 in the chamber 106 . For example, the controller 54 may include a set of substrate positioning instructions to operate one or more substrate holders 108 and substrate conveyors to position the substrate 104 within the chamber 106; a set of gas flow control instructions to operate the sputtering gas supply 103 and flow controller 126; gas pressure control instruction set to operate exhaust system 128 and throttle valve 137 to maintain pressure in chamber 106; gas actuator control instruction set to operate gas actuator 190 to The gas excitation level is set; the temperature control instruction set is used to control the temperature in the chamber 106; and the process monitoring instruction set is used to monitor the process in the chamber 106.

The sputtering target 20 of the present invention can be used with any sputtering process. Exemplary sputtering processes are described in the following patents, the entire contents of which are incorporated herein by reference: U.S. Patent No. 6,616,402 to Kumagai entitled "Sputtering Method and Apparatus," US Patent No. 3,617,463 granted to Gregor et al., entitled "Apparatus and Method for Sputter Etching (apparatus and method for sputter etching)", and awarded to Macaulay et al. U.S. Patent No. 4,450,062, granted to Makino et al., entitled "Method for Producing a Specified Zirconium-Silicon Amorphous Oxide Film Composition by Sputtering" Method for Sputtering and Integrated Circuit Device (U.S. Patent No. 5,209,835) to Nihei et al. No. 5,175,608 and U.S. Patent No. 5,160,534 entitled "Titanium-Tungsten Target Material for Sputtering and Manufacturing Method Therefor" to Hiraki et al.

Although the exemplary embodiments of the present invention have been shown and described, those skilled in the art can design other embodiments in combination with the present invention, and these also belong to the protection scope of the present invention. For example, target 20 may comprise materials other than the exemplary materials described herein, and other processing steps may also be performed on target 20 . Likewise, targets 20 having different shapes or different compositions may be processed other than those explicitly described. Additionally, relative or positional terms shown in the exemplary embodiments may be interchanged. Therefore, the appended claims should not be limited to the descriptions herein described which serve to explain the preferred versions, materials or spatial arrangements of the invention.

Claims (19)

1. the method for this sputtering target of pre-treatment before sputtering target is used for sputtering technology, described method comprises:

(a) provide the sputtering target of sputtering surface with impaired upper layer; And

(b) the described sputtering surface of the described sputtering target of polishing to be removing the thickness at least about 25 microns, and obtains to have about 4 sputtering surfaces to the average surface roughness of about 32 microinchs.

2. method according to claim 1 is characterized in that, described (b) comprises electrochemical etching, wherein during described glossing, electric current is applied to the described sputtering surface of described target.

3. method according to claim 2 is characterized in that, comprises applying from about 5 to about 70mAmps/cm ²Electric current.

4. method according to claim 1 is characterized in that, described (b) comprises the described sputtering surface that polishes described sputtering target by following arbitrary method:

(1) described sputtering surface is pressed to grinding miller with himself weight, between described plate and described sputtering surface, apply rubbing paste simultaneously;

(2) use the rubbing paste that is included in the diamond particles in the deionized water;

(3) use comprises that size is at about 2 rubbing pastes to about 15 microns diamond particles;

(4) sputtering surface that described sputtering target is set towards top and with polish brush towards sputtering surface to pressing down.

5. method according to claim 1 is characterized in that, is included in described (b) carries out following steps afterwards at least one:

(1) the described sputtering surface by the described sputtering target of electrochemical etching etching; And

(2) utilize the described sputtering surface of the described sputtering target of acidic etchant etching.

6. method according to claim 5 is characterized in that, comprises hydrofluoric acid and nitric acid in acidic etchant described in described (2), and comprise following at least one of them:

(1) described hydrofluoric acid comprises about 10% concentration to about 52% weight percent;

(2) described nitric acid comprises about 50% concentration to about 80% weight percent;

(3) volume ratio of described hydrofluoric acid and nitric acid is about 10% to about 20%.

7. method according to claim 1 is characterized in that, also is included at least one of described (b) following steps afterwards:

(i) utilize the described sputtering surface of the described sputtering target of acidic etchant etching; And

(ii) described sputtering surface is heated to about 400 ℃ to about 1000 ℃ temperature.

8. method according to claim 1 is characterized in that, comprising provides the sputtering target that comprises the sputtering surface of being made up of titanium, tantalum or tungsten.

9. method according to claim 1 is characterized in that, described sputtering target comprise following at least one of them:

(i) sputtering plates, it is to have about 200 disks to about 500mm diameter;

(ii) has 2.5 to about 25mm thickness; And

The backboard that (iii) comprises copper-zinc alloy.

10. method according to claim 1 is characterized in that, also comprises:

(1) described sputtering target is installed in sputtering zone;

(2) in described sputtering zone, be positioned adjacent the substrate of described target; And

(3) form plasma body to sputter material to described substrate from described sputtering target.

11. the method for the described sputtering target of pre-treatment before sputtering target is used for sputtering technology, described method comprises:

(a) provide the sputtering target of sputtering surface with impaired upper layer; And

(b) the described sputtering surface of the described sputtering target of etching in the acidic etchant that comprises hydrofluoric acid and nitric acid, described hydrofluoric acid comprises about 30% concentration to about 52% weight percent, described nitric acid comprises about 50% concentration to about 80% weight percent, and the volume ratio of described hydrofluoric acid and nitric acid is about 10% to about 20%.

12. method according to claim 11 is characterized in that, also comprises by described sputtering surface is exposed in the electrolytic solution applying electric current by described electrolytic solution simultaneously, makes the described sputtering surface of the described sputtering target of electropolish.

13. method according to claim 12 is characterized in that, comprises to described electrolytic solution applying about 5 to 70mAmps/cm ²Electric current.

14. method according to claim 11 is characterized in that, also comprises following at least one:

(1) the described sputtering surface of electrochemical etching; Perhaps

(2) by under the own wt of described sputtering surface, being pressed to grinding miller and simultaneously applying rubbing paste and polish described sputtering surface to described the wheel.

15. the method for the described sputtering target of pre-treatment before sputtering target is used for sputtering technology, described method comprises:

(a) provide the sputtering target of sputtering surface with impaired upper layer; And

(b) the described impaired upper layer of described sputtering surface is heated to temperature at least about 400 ℃.

16. method according to claim 15 is characterized in that, is included in the described sputtering surface of heating under following at least one condition:

(1) described sputtering surface is heated to 2/3 temperature less than the described fusing point of the described material of described sputtering surface;

(2) described sputtering surface is heated to less than about 1000 ℃ temperature;

(3) described sputtering surface is heated to deep thickness less than 300 microns;

(4) use the described sputtering surface of laser beam heats; And

(5) use one group of quartz lamp to heat described sputtering surface.

17. the method for the described sputtering target of pre-treatment before sputtering target is used for sputtering technology, described method comprises:

(a) provide the sputtering target of sputtering surface with impaired upper layer; And

(b) keep described sputtering surface one clearance distance of electrode distance; And

(c) apply pulsed current between described electrode and described sputtering surface, forming electric arc to described electrode, thereby remove the described impaired upper layer of described sputtering surface basically.

18. the method for the described sputtering target of pre-treatment before sputtering target is used for sputtering technology, described method comprises:

(a) sputtering surface with sputtering target is immersed in the electrolytic solution, and described sputtering surface has impaired upper layer; And

(b) apply electric current to remove the described impaired upper layer of described sputtering surface by described electrolytic solution.

19. method according to claim 18 is characterized in that, comprise following at least one of them:

(1) applies about 5 to about 70mAmps/cm by described electrolytic solution ²Electric current;

(2) described sputtering surface is immersed in comprises HCl, HNO ₃, H ₂SO ₄Perhaps in the electrolytic solution of its mixture; And

(3) apply volts DS to described target and electrode in described electrolytic solution, described volts DS is about 5 to about 75 volts.

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