WO1996014653A2

WO1996014653A2 - Method and apparatus for reducing arcing in plasma processing chambers

Info

Publication number: WO1996014653A2
Application number: PCT/US1995/015324
Authority: WO
Inventors: Charles N. Vannutt; Bhola N. De; Jonathan Ishii
Original assignee: Materials Research Corporation
Priority date: 1994-11-04
Filing date: 1995-11-03
Publication date: 1996-05-17
Also published as: WO1996014653A3; JPH09511027A; AU4244896A

Abstract

Arcing in a plasma process is reduced by shaping the target (40) and dark space shield (13) so that their peripheral regions curve away from each other, reducing electric fields and the propensity for arcing between the target and dark space shield. Also disclosed is an improved system for detecting arcing and presenting data related to detected arcs for analysis; the system generates a graph of the number of arcs, or rate of arcing, as a function of total power consumed, or alternatively a histogram of bars (120) each indicating the number of arcs having an associated magnitude.

Description

METHOD AND APPARATUS FOR REDUCING ARCING IN PLASMA PROCESSING CHAMBERS

Field of the Invention The present invention relates to methods and apparatus for reducing arcing in sputtering chambers.

Background of the Invention

In a sputter coating process, a substrate mounted in a vacuum chamber filled with a generally chemically inert gas is coated with material sputtered from a target. The target is subjected to a negative electrical potential with respect to the chamber wall or other anode. The potential gradient adjacent the target surface causes electrons to be emitted from the target which, on their way to the chamber anode (usually formed in part by the grounded chamber wall) , strike and ionize some of the inert gas, forming a conductive plasma in the chamber. The positive ions which reach the edge of the plasma are attracted to and strike the negative target, transferring momentum to the target material, and ejecting particles of the material from the target surface. The substrate to be coated is positioned in the chamber with its surface facing the target, so that ejected particles adhere to and coat the substrate surface.

Magnetron sputtering is a sputter coating process in which a magnetic field is formed over the target surface, usually including magnetic field lines parallel to the target surface, and, in many applications, in the form of a closed magnetic tunnel. The magnetic field causes the electrons emitted to move in spiral paths, trapping the electrons in regions proximate the target surface enclosed by the field, thereby increasing the rate of electron collisions with gas atoms, which in turn increases the ionization of the gas and the efficiency of the sputtering process. Often a conductive target is used to sputter an insulating film on the substrate. Under these conditions, a common processing problem is arcing in the process chamber. Insulating material slowly accumulates on certain areas of the target surface. This leads to a space charge accumulation on the target, and, ultimately, an arc discharge to any nearby grounded surface, for example to the plasma in the chamber or to a grounded "dark space" shield surrounding the target. Arcs above a certain energy level damage the target, films on the substrate, and also generate particles inside the chamber which damage the substrate.

Arc suppression power supplies have been introduced by several vendors, which can be helpful in reducing arcing in plasma processes.

Essentially, these supplies include control circuitry to prevent spike currents in the chamber which are normally associated with arcing. Despite the introduction of arc suppression power supplies, there remains a need to further reduce arcing in plasma processing chambers. Furthermore, known measurement techniques have not quantified the level of arcing in plasma processing chambers with sufficient accuracy, nor presented the data in a sufficiently intuitive manner, frustrating efforts to reduce arcing in these chambers. fiu--nιιrγ nf the Invention

In accordance with principles of the present invention, there is provided a plasma processing chamber having significantly reduced arcing and correspondingly improved process reliability, and a technique for measuring chamber arcing to evaluate the level of arcing in a process, permitting accurate and intuitive measurements of the reductions in arcing achieved.

Thus, specifically, in one aspect the invention features a target for mounting in a sputtering chamber, in which a peripheral region of the sputtering surface of the target is sloped away from the periphery of the sputtering surface, decreasing the likelihood for arcing from the sputtering surface to the walls of the chamber. In specific embodiments, the target has a front section of sputtering material (a central region of which may be concavely curved) , bonded to a backing section manufactured of a different material. The sputtering surface is disk shaped, and the sloped region forms a circular rim completely surrounding the sputtering surface. In another aspect, the invention features a dark space shield of conductive material electrically connected to the chamber and surrounding the target. An inner peripheral edge of the dark space shield is sloped away from the peripheral region of the sputtering surface of the target, thereby decreasing the likelihood for arcing between the sputtering surface and the dark space shield. In specific embodiments, this dark space shield is combined with the target described in the preceding paragraph.

In another aspect, the invention features a method of detecting arcing in a plasma processing chamber by detecting rapid changes in voltage or current in the power supply, indicative of an arc, storing a record indicative of when said arc was detected, and generating a visual presentation of the number of arcs detected over the passage of time. In specific embodiments, the visual presentation is points plotted on an two-axis graph, where one axis identifies the total number of arcs recorded, or the rate at which arcs were recorded, and the second axis identifies total electrical energy input to the process.

In another aspect, the invention features an alternative method of detecting arcing in a plasma processing chamber, by detecting rapid changes in voltage or current at the power supply, indicative of an arc, storing a record of the magnitude of voltage or current variation at the power supply caused by the arc, and generating a visual presentation of the magnitude of arcs indicated by said records. In specific embodiments, the visual presentation is a histogram of bars each representing a number of arcs having an associated magnitude.

The above and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof. Brief Description of the Drawing

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.

Fig. 1 is a cross-sectional view through a sputter coating apparatus embodying principles of the present invention, and Figs. IA and IB are detail views of Fig. 1 in accordance with two embodiments of the present invention;

Fig. 1C is a plan view, taken along line 1C-1C of Fig. 1, of a magnet structure 60 in accordance with one embodiment of the present invention;

Fig. 2 is a schematic block diagram of an arc measurement system embodying principles of the present invention;

Figs. 3A, 3B and 3C are exemplary traces stored by the digital storage oscilloscope 82 of Fig. 2 when used to detect arcing in the sputter coating apparatus of Fig. 1; Fig. 4 is a flow chart of a process carried out in computer 86 of Fig. 2 for acquiring and processing traces and other data stored by digital oscilloscope 82;

Figs. 5A and 5B are histograms produced by computer 86 of arcing measured by the system of Fig. 2, showing improvements in arc suppression resulting from the use of an arc suppressing power supply;

Figs. 6A, 6B and 6C are charts produced by computer 86, respectively identifying, over the life of various target configurations, the total count of arcs, and the rate (in arcs per 10 k h and arcs per second) of arcing measured by the system of Fig. 2. Detailed Description of Specific Embodiments

Sputtering machines of the type to which the present invention relates are described in the following commonly assigned U.S. patents, which are hereby expressly incorporated by reference into this application in their entirety:

U.S. Patent No. 4,855,033 entitled "Cathode and Target Design for a Sputter Coating Apparatus"; U.S. Patents Nos. 4,909,695 and 4,915,564 entitled "Method and Apparatus for Handling and Processing Wafer-Like Materials";

U.S. Patent No. 4,957,605, entitled "Method and Apparatus for Sputter Coating Stepped Wafers";

U.S. Patent No. 5,130,005, entitled "Magnetron Sputter Coating Method and Apparatus with Rotating Magnet Cathode"; and,

U.S. Patent No. 5,284,561, entitled "Method and Apparatus for Sputter Coating Employing Machine Readable Indicia Carried by Target Assembly".

Referring to Fig. 1, shown in cross- section is a sputter coating processing chamber 10 of a sputter coating apparatus in accordance with principles of the present invention. Chamber 10 is a portion of the sputter processing apparatus disclosed in U.S. Patent 4,909,695.

Chamber 10 is a vacuum chamber, enclosed by cylindrical walls 11 and 12, annular dark space shield 13 and cathode assembly 20. Annular vacuum seals 14 and 15 between dark space shield 13, walls 11 and cathode assembly 20 prevent air leakage into chamber 10. Within the processing chamber 10, generally above the cathode assembly 20, is a substrate or workpiece 21 in the form of a flat silicon wafer or disk, surface 22 of which is coated by the sputter coating process performed within the processing chamber 10. The wafer 21 is supported in a wafer holder 25, perpendicular to, and concentric with, central axis 27 of the processing chamber 10.

The cathode assembly 20 supports the sputtering target, which includes a sputtering plate 40 of sputtering material mounted on and supported by a backing plate 42 of heat conductive and electrically conductive material, forming a circular target assembly 40/42 having a continuous, smooth concave sputtering surface 41. The target assembly 40/42 is removably mounted to cathode assembly 20 by bolts 49, permitting removal and replacement of the target when the sputtering material of sputtering plate 40 has been consumed.

The cathode assembly module 20 supports the target assembly 40/42 with its axis in alignment with the axis 27 of the chamber 10 and with its sputtering surface 41 facing and exposed to the interior of chamber 10 and the surface 22 of the wafer 21 to be coated.

The back surface 39 of the sputtering plate 40 is preferably soldered or otherwise bonded to the front surface 43 of the backing plate 42, in intimate thermal contact therewith. The back surface 39 of the sputtering plate 40 is a cooling surface which conforms to and lies in close cooling contact with the front surface 43 of the backing plate 42. Behind the backing plate 42, opposite the cooling surface 43 thereof, is a space 44 for the circulation of cooling liquid, e.g. water, to remove heat generated in the target 40/42 during sputtering, by cooling the heat conductive backing plate 42, when the target plate 40 is mounted in cathode assembly module 20. The cooling fluid is circulated into and out of space 44 from an inlet port 45 to an outlet port 46, through a magnet assembly 50. Space 44 is completely enclosed between backing plate 42 of the target and housing structure 48 onto which the target is rigidly supported by bolts 49.

Sputtering plate 40 i_s formed by turning a block of sputtering material such as silicon nitride or silicon oxide on a lathe. The target backing plate 42 is similarly formed by turning a block of heat conductive and electrically conductive material, preferably hard tempered OFHC copper or alloy.

In the illustrated embodiment of the invention, the magnet assembly 50 includes a shaft

51 having a threaded end 52 by which the shaft 51 is rigidly mounted in a threaded bore 53 at the center of the back surface of the backing plate 42. The assembly 50 also includes a rotatable magnet carrier 55 which includes a circular disk 56 of non-magnetic stainless steel or other such material having a central hole 57 therein at which the disk 56 is rigidly mounted to a sleeve assembly 58. Sleeve assembly 58 is rotatably mounted through a bearing 59 through the housing 48 and to the backing plate 42 to rotate about the shaft 51 on axis 27. The rotatable magnet assembly further includes a magnet structure 60 (omitted for clarity, see Fig. 1C below) rigidly mounted on the disk 56 to rotate therewith. The magnet structure 60 surrounds the axis 27 and lies beneath or behind the backing plate 42, opposite the front surface 43 thereof, and close enough thereto to generate a magnetic field above the sputtering surface 41 of the target assembly 40/42.

Shaft 51 has a cooling fluid inlet duct 62 extending therethrough which communicates with the inlet port 45 to the interior cooling chamber 44 between the backing plate 42 and the housing 48. The housing 48 has mounted near the edge thereof a cooling fluid outlet duct 63 which communicates with the fluid outlet port 46 in the cooling space 44.

Mounted to the back of the housing 48 is a bracket 64 to which is mounted a magnet rotary drive motor 65. The motor 65 has an output shaft 66 with a cogged drive wheel 67 mounted at the end thereof for driving a cogged drive belt 68. The belt 68 extends around a cogged drive wheel 69 attached to a drive shaft 70 which is rotatably mounted on the housing 48, extending therethrough, and having a free end 71 to which is mounted a drive gear 72. The drive gear 72 is positioned within the space 44 where it engages a mating gear 72a attached to the disk 56 of the rotatable magnet assembly 50. Accordingly, the motor 65, when energized, rotates the magnet assembly 50 to rotate the magnet structure 60 behind the target backing plate 42 to rotate the magnetic field over the sputtering surface 41 of the target assembly 40/42. Further details of the construction of the magnet structure 60 and its arrangement on the magnet assembly 50 appear in the above-referenced U.S. patents.

During processing, electrical power from power supply 74 is applied to cathode assembly 20 relative to walls 11 and 12 of chamber 10. (Seals 14 are electrically insulating, preventing current flow from cathode assembly 20 to walls 11.) The electrical power creates a plasma in chamber 10 in the area generally above surface 41 of target plate 40, causing material from surface 41 of target plate 40 to sputter onto surface 22 of wafer 21. Control unit 73 is connected to power supply 74 and controls parameters of the process such as the power applied to the target during the sputtering operation, as more particularly described in the above incorporated U.S. Patent No. 5,130,005.

As illustrated in Figs. IA and IB, target plate 40 includes at its periphery a convexly shaped region 40a, and dark space shield 13 has an annular notch 78 surrounding the periphery of target plate 40. The peripheral region of target plate 40 can take any number of shapes, including a curve and bevel as shown in Fig. IA, a single angle bevel as shown in Fig. IB, a smoothly convex or concave curved surface, or any other structure which curves or angles away from the dark space shield. Similarly, the peripheral region of dark space shield 13 can take any number of shapes such as a bevel, notch, smooth curve, or any other structure which curves or angles away from the periphery of target plate 40. These various shapes, and other similarly effective shapes, will be referred to in the following a "sloping" shapes. Any sloping shape in the peripheral region of the target or dark space shield which curves or bends outwardly from the dark space shield or target, respectively, can be suitably used in accordance with principles of the present invention. Figs. IA and IB illustrate in dotted outline the typical profile 77 of the outer edge of the target sputtering plate 40 and the typical profile 79 of the inner edge of the dark space shield 13. The nature of the curves, bevels, and notches used in accordance with the invention is apparent by comparing the profiles 77 and 79 to the locations of the target and shield edges illustrated in Fig. IA and IB. The rounded, beveled or notched structures

40a and 78 reduce the likelihood of arcing between target plate 40 and dark space shield 13 by increasing the distance between plate 40 and shield 13, and eliminating sharp corners, and thereby reducing the intensity of electric field lines between the plate 40 and shield 13. Although shield 13 remains relatively close to backing plate 42, arcing is less likely in this area because, unlike target plate 40, backing plate 42 does not accumulate significant insulating material during processing and thus is less likely to develop sufficient space charge accumulation to produce an arc. Furthermore, depending on the backing plate material in use, arcing from backing plate 42 is less likely to generate particulate than arcing from target plate 40.

In one embodiment, as shown in Fig. IA, the convex target edge 40a follows a bevel angle of 82 degrees from vertical, terminating in a rounded edge 40b having a radius of curvature of .14 inches. In the embodiment shown in Fig. IB, the target edge follows a bevel angle of 34 degrees from vertical, terminating in a vertical edge of .05 inches. Referring to Fig. IC, in accordance with a further embodiment of the invention, the magnet structure 60 is configured to prevent "dead spots" on the surface of the sputtering plate 40. Such dead spots accumulate insulating material and result in space charge accumulation and increased arcing. In one embodiment, the magnet structure is that disclosed in above-referenced U.S. Patent 5,130,005, including a ribbon magnet 75 having a north-south magnetic axis oriented generally perpendicular to axis 27, and auxiliary magnets 81 having their north-south magnetic axes oriented generally parallel to axis 27 with their north poles directed toward sputtering plate 40 and backing plate 42. Furthermore, in another embodiment this magnet structure may be improved as shown in Fig. IC by the inclusion of an additional auxiliary magnet 61 of the same type and orientation as magnets 81, but having its south pole directed toward sputtering plate 40 and backing plate 42. As elaborated in further detail below, experimental analysis has shown that a sputtering system having a modified target plate 40 and backing plate 42 of the types illustrated in Figs. IA and IB, and/or a modified magnet structure of the type illustrated in Fig. IC, can exhibit reductions in arc intensity and/or frequency of a factor of at least 10. Further reductions can be achieved by use of an advanced design arc suppressing power supply 74, such as an ENI Model DCG100, available from ENI, a division of Astec America, Inc., 100 High Power

Road, Rochester, NY 14623 or an Advanced Energy MDX- 10 with SPARC-LE, available from Advanced Energies Industries, Inc. 1600 Prospect Parkway, Fort Collins, CO 84525. The measurement system of Fig. 2 is suitable for non-invasively detecting arcs and evaluating the intensity of arcs in a sputtering system such as illustrated in Fig. 1. The system of Fig. 2 includes a current and voltage probe 80 coupled to line 76 between power supply 74 and cathode assembly 20. Probe 80 senses the voltage of target assembly 20 directly via a high-resistance, low capacitance probe, and senses the current on line 76 by detecting the voltage drop across a low- value high-power resistor in series with line 76. Probe 80 may be a model AM6303 or AM503A probe, available from Tektronix, Inc. at P.O. Box 500, Beaverton, OR 97077. These probes allow non- invasive monitoring of the activity in the chamber, that is, the monitoring does not significantly change the behavior of the chamber.

Probe 80 is coupled to a digital storage oscilloscope 82, e.g. a Tektronix model 7200A oscilloscope using a LeCroy model 7242B plug-in module, available from LeCroy Corp., 700 Chestnut Ridge Rd. , Chestnut Ridge, NY 10977. Oscilloscope 82 is adjusted to trigger and produce a trace upon detection of a voltage or current value indicating an arc in the processing chamber 10. Storage oscilloscope 82 is coupled via a

GPIB communication cable 84 to a computer 86 which processes stored waveforms obtained by oscilloscope 82. In accordance with the standard GPIB interface of the 7200A oscilloscope, when the oscilloscope triggers, a message is transferred to computer 86, --

which responds by reading the digital samples captured by oscilloscope 82 and processing the samples as discussed below with reference to Fig. 4. The apparatus described above was used in a series of operational tests, under the following conditions. A Silicon Nitride (SiN) target was used to deposit insulating films via DC reactive sputtering. The chamber pressure was 5 milliTorr and the electrical power consumption was approximately 5 kilowatts. A mixture of Argon and Nitrogen gas was flowed into the chamber at a flow rate of 75 seem of Argon and 75 seem of Nitrogen.

Referring to Figs. 3A-3C, during a plasma process, oscilloscope 82 will generate a current, voltage, and power (current x voltage) waveform.

The waveforms stored by oscilloscope 82 will include a large disturbance indicating the occurrence of an arc which triggered the oscilloscope. As shown in the Figs. , an exemplary arc produced a spike 90 of approximately 100 Amperes of current for a time period of approximately 5 microseconds (see Fig. 3A) , resulting in a drop 91 in the target voltage of approximately 600 volts over a time period 92 of approximately 30 microseconds (see Fig. 3B) . The normal power level is slightly above 5 kilowatts; the arc produces 4 microsecond burst 93 during which the chamber absorbs an additional 10 kilowatts of electrical power, followed by a 30 microsecond period 94 where the electrical power is reduced below the normal level (see Fig. 3C) .

Traces captured by oscilloscope are processed by computer 86, which is preferably a PC- compatible computer using an 80486 microprocessor. The GPIB cable 84 from oscilloscope 86 is interfaced to the computer's microprocessor by an interface card in an expansion slot of the computer, such as an NI488 interface card, available from National Instruments, Inc., 6504 Bridge Point Parkway, Austin, TX 78730-5039. Referring to Fig. 4, when oscilloscope 82 detects an arc and stores a trace, it sends a trigger signal through the GPIB-488 cable 84, triggering processing in computer 86. When computer 86 detects 100 the trigger signal, it generates a record, e.g. in a file in memory or on a hard disk, corresponding to the detected arc. The computer first stores 102 in the record the time that the arc was detected. Next, the computer reads 104 from the oscilloscope digital samples corresponding to the trace produced by the arc. These samples are analyzed to compute 106 the maximum peak-to-peak voltage and current variations in the samples. At the same time, the maximum voltage and maximum current values are computed 108, and the minimum peak-to-peak variation of voltage and current are computed 110. These computed values are then stored 112 in the record.

After the plasma process has finished, computer 86 reads 114 the stored records into a plotting program, presentation graphics program or spreadsheet program (such as the "123" program, commercially available from Lotus Development Corporation, 55 Cambridge Parkway, Cambridge, MA 02142) , to produce output plots depicting the amount of arcing measured during the plasma process. In one embodiment, computer 86 produces 116 and displays and/or prints a histogram depicting the number of arcs measured with specific peak-to-peak voltage or current values, as discussed below with reference to Figs. 5A and 5B. In a second embodiment, computer 86 produces 118 and displays and/or prints curves of the number of arcs and/or the rate at which arcs were generated vs. the elapsed time of the plasma process, as discussed below with reference to Figs. 6A-6C. Referring to Fig. 5A, a histogram produced in accordance with the first embodiment noted above includes bars 120 showing the number of arcs measured at each peak to peak current level. To produce the histogram of Fig. 6A, the plasma process was operated using a standard target and dark space shield (i.e., a target and dark space shield having sharp corners, as shown in dotted outline profiles 77 and 79 in Figs. IA and IB) , for approximately 100 hours, for a total energy consumption of 573 kiloWatt-hours. As is apparent from Fig. 5A, the largest number of arcs had a peak-to-peak current amplitude of 120 Amperes, and most arcs had current amplitudes in this approximate range. Fig. 5B was generated using the same process parameters, time duration and chamber as Fig. 5A, but with a current-limiting power supply (specifically, a SPARC-LE power supply discussed above) in place of a standard power supply. The resulting histogram clearly and intuitively illustrates the beneficial result of using a current-limiting power supply: the bars 120 are clustered around a maximum peak-to-peak amplitude of 22 Amperes, compared to 120 Amperes in Fig. 5A. Thus, the use of a current-limiting power supply reduced the arc current amplitude by almost a factor of 6. Similar reductions have been observed in voltage and power.

Figs. 5A and 5B also illustrate the efficiency and intuitive nature of the results produced by the measurement system of Fig. 2. The histograms show, in a clear and intuitive way, the magnitude and consistency of the arcing produced in the process chamber. This can be an invaluable tool in evaluating the effect of power supply or chamber design changes on arcing.

Referring to Fig. 6A, in the second embodiment noted above, computer 86 produces curves 130, 132 representing the total arc count as a function of the total power consumed by the process.

Curve 130 represents the total arc count of a standard chamber layout (including sharp corners on target plate 40 and dark space shield 13, as shown by profiles 77, 79 in Figs. IA and IB) using a standard power supply. As can be seen in Fig. 6A, this configuration produces arcs at a fairly regular rate, producing a nearly straight curve 130.

Curve 132, however, represents the total arc count using the same chamber layout and processing conditions, but substituting a current- limiting power supply (specifically, ENI Model DCG100 power supply discussed above) in place of a standard power supply. As is apparent from Fig. 6A, a substantially smaller number of arcs is produced. Furthermore, the arcs are produced at an increasing rate as the process continues, indicating that target wear (which is directly related to the total power consumption) increases arcing. The effect of target wear can be seen more dramatically in Fig. 6B. Fig. 6B is a plot of the rate of arc generation, i.e., the number of arcs measured for each 10 kiloWatt-hours of power consumed, vs. the total kiloWatt-hours expended. The curves in Fig. 6B therefore essentially represent the slope of the curves in Fig. 6A.

Curve 130' shows the rate of arc generation for the standard chamber and power supply configuration. As noted above, the rate of arc generation is relatively constant throughout the target life. Curve 132' shows the rate of arc generation for the current limiting power supply, which, as noted above, increases over the life of the target. Figs. 6A and 6B illustrate the reduction in arcing brought about by a current-limiting power supply, and show this reduction in an intuitive and effective manner. As illustrated below, further reductions may be achieved using different magnet configurations such as that shown in Fig. IC, and using the target and dark space shield configurations illustrated in Figs. 1, IA and IB.

Referring to Fig. 6C, curves 140, 142 and 144 illustrate the arc rates (in arcs per second of elapsed time) achieved with various target configurations. Curve 140 represents the arc rate of a standard chamber layout (including sharp corners on target plate 40 and dark space shield 13, following profiles 77, 79 of Figs. IA and IB) using a standard power supply. As can be seen in Fig. 6A, this configuration produces arcs at a rate of up to 2 arcs per second.

Curve 142 represents the arc rate of a chamber having the same configuration as that which produced curve 140, but including a center-modified magnet structure such as that shown in Fig. IC (a modification of the structure shown in above- referenced U.S. Patent 5,130,005). This center- modified magnet structure reduces accumulation of sputtered insulating material at the center of the target and accordingly reduces arcing from the center of the target, e.g. limiting arcing to a rate of approximately 1 arc per second, as shown in Fig. 6C.

Further reductions in arc rate can be achieved by the target and dark space shield modifications shown in Figs. IA and IB. Curve 144 represents the arc rate for a chamber having the same configuration as that which produced curve 142, but including a target with a beveled and rounded outer edge 40a, 40b, and a dark space shield having an annular notch 78, such as shown in Fig. IA. As seen in Fig. 6C, the arc rate is reduced substantially over the life of the target, achieving a maximum of approximately 0.6 arcs per second.

The foregoing has described a target and chamber configuration which reduces arcing in a processing chamber, and a measurement apparatus and method which demonstrates arcing in an efficient and intuitive manner. Although this invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative example shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept. What is claimed is:

Claims

1. A sputtering apparatus for sputtering a surface of a substrate, comprising a vacuum chamber for supporting said substrate in vacuo in an interior cavity, a target including a sputtering surface manufactured of sputtering material, said sputtering surface being exposed to said interior cavity of said vacuum chamber such that, when said sputtering surface is bombarded with ions from said chamber, material from said sputtering surface sputters into said chamber, and a dark space shield of conductive material electrically connected to said chamber, an inner peripheral edge of said dark space shield surrounding, but spaced a distance away from, a peripheral region of said sputtering surface of said target, said inner peripheral edge of said dark space shield being sloped away from said peripheral region of said sputtering surface of said target, to thereby decrease the likelihood for arcing between said sputtering surface and said dark space shield.

2. The sputtering apparatus of claim 1, wherein said peripheral region of said sputtering surface is sloped away from said dark space shield to thereby decrease the likelihood for arcing between said sputtering surface and said dark space shield.

3. The sputtering apparatus of claim 1 wherein a central region of said sputtering surface is concavely curved.

4. The sputtering apparatus of claim 1 further comprising a backing section manufactured of a material different from said sputtering material.

5. The sputtering apparatus of claim 1 wherein said peripheral region forms a rim completely surrounding said sputtering surface.

6. The sputtering apparatus of claim 1, wherein said target is disk-shaped, said peripheral region of said sputtering surface of said target forms a circular rim surrounding said sputtering surface, and said inner peripheral edge of said dark space shield is also circular.

7. A method of detecting arcing in a plasma processing chamber subjected to power from an electrical power supply to produce a plasma, and presenting data related to detected arcs for analysis, comprising detecting a rapid change in voltage or current at said electrical power supply indicative of an arc within said chamber, • storing a record indicative of when said arc was detected, repeating said detecting and storing in response to subsequent arcs, retrieving the stored records and deriving therefrom information correlated to the number of arcs detected over the passage of time, and in response thereto generating a visual presentation of the number of arcs detected over the passage of time.

8. The method of claim 7 wherein said visual presentation comprises coordinates plotted on a graph having two coordinate axes.

9. The method of claim 8 wherein a first axis of said graph identifies the total number of arcs recorded, a second axis of said graph identifies total electrical energy input to said plasma process, deriving information correlated to the number of arcs detected over the passage of time comprises deriving, from a stored record, a total number of arcs detected and a total amount of electrical energy expended, and generating a visual presentation comprises plotting a coordinate on said graph at a location corresponding to said derived number of arcs detected and amount of energy expended.

10. The method of claim 8 wherein a first axis of said graph identifies the rate at which arcs were detected, a second axis of said graph identifies total electrical energy input to said plasma process, deriving information correlated to the number of arcs detected over the passage of time comprises deriving, from a stored record, a rate at which arcs were detected over a period of time and a total amount of electrical energy expended over this period of time, and generating a visual presentation comprises plotting a coordinate on said graph at a location corresponding to said derived rate and amount of energy expended.

11. A method of detecting arcing in a plasma processing chamber subjected to power from an electrical power supply to produce a plasma, and presenting data related to detected arcs for analysis, comprising detecting a rapid change in voltage or current at said power supply indicative of an arc within said chamber, ^• storing a record indicative of a magnitude of voltage or current variation at said power supply when said arc was detected, repeating said detecting and storing in response to subsequent arcs, retrieving the stored records and deriving therefrom information correlated to the magnitude of arcs detected, and generating a visual presentation of the magnitude of arcs indicated by said records.

12. The method of claim 11 wherein said visual presentation is a histogram of bars each representing a number of arcs having an associated magnitude.