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  Apparatus, method and system for monitoring chamber parameters associated with a deposition processUSPTO Application #: 20060054497Title: Apparatus, method and system for monitoring chamber parameters associated with a deposition process Abstract: Apparatus and methods for measuring characteristics of a metallic target as well as other interior surfaces of a sputtering chamber. The apparatus includes a sensor configured to emit an energy beam toward a surface of interest and to detect an energy beam therefrom, the detected energy beam being indicative of parameters of a characteristic of interest of the surface of interest. Quantitative and qualitative characteristics of interest may be determined. A sputtering system including the apparatus and operable according to the methods of the invention is also disclosed. (end of abstract) Agent: Trask Britt - Salt Lake City, UT, US Inventors: Mark A. Jaso, Terry L. Gilton USPTO Applicaton #: 20060054497 - Class: 204192130 (USPTO) Related Patent Categories: Chemistry: Electrical And Wave Energy, Non-distilling Bottoms Treatment, Coating, Forming Or Etching By Sputtering, Glow Discharge Sputter Deposition (e.g., Cathode Sputtering, Etc.), Measuring Or Testing (e.g., Of Operating Parameters, Property Of Article, Etc.) The Patent Description & Claims data below is from USPTO Patent Application 20060054497. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of application Ser. No. 10/609,297, filed Jun. 27, 2003, pending, which is a continuation-in-part of U.S. patent application Ser. No. 10/352,699, entitled "Device for Measuring the Profile of a Metal Film Sputter Deposition Target, and System and Method Employing Same," filed Jan. 27, 2003, now U.S. Pat. No. 6,811,657, issued Nov. 2, 2004, the disclosure of which is incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates generally to sputter deposition of materials on substrate surfaces. More specifically, the present invention relates to methods and apparatus for measuring characteristics of a sputtering target and other surfaces within a sputtering vacuum chamber. [0004] 2. State of the Art [0005] A thin film of metallic material may be deposited on a substrate using a sputter deposition process wherein a metallic target is attacked with ions, causing atoms or small particles of the target to be ejected from the target and deposited on the substrate surface. FIG. 1 illustrates a cross-sectional schematic of a conventional sputtering apparatus 10 comprising a vacuum chamber 12 having inner chamber walls 13, a gas inlet 14 and a gas outlet 16. The vacuum chamber 12 may further include a window 15 comprising a material that is transparent to predetermined wavelengths of electromagnetic radiation. The sputtering apparatus 10 further comprises a substrate support pedestal 24 and a metallic target 22 attached to a sputtering cathode assembly 18, each located within the vacuum chamber 12. The pedestal 24 may be configured to secure a substrate 26 thereto with a biasable electrostatic chuck, a vacuum chuck, a clamping structure, or a combination of methods. The substrate 26 may be transported to and from the pedestal 24 manually or with a robotic arm or blade (not shown). [0006] During the sputtering process, the vacuum chamber 12 is filled with an inert gas, such as argon, through the gas inlet 14 and then reduced to a near vacuum through the gas outlet 16. The target 22 is negatively charged to cause electrons to be emitted from an exposed surface 23 of the target 22 and move toward an anode (not shown). A portion of the moving electrons strike atoms of the inert gas, causing the atoms to become positively ionized and move towards the negatively charged target 22. The electrons, inert gas atoms, and ions form a plasma which is typically intensified and confined over the target surface 23 by a magnetic field generated by a magnet assembly 20 located proximate the target 22. The magnet assembly 20 may comprise one or more permanent magnets or electromagnets located behind and/or to the side of the target 22. A portion of the ions discharging from the plasma strikes the target surface 23 at a high velocity, causing atoms or small particles of the target 22 material to be ejected from the target surface 23. The ejected atoms or small particles then travel through the vacuum chamber 12 until they strike a surface, such as the surface of the substrate 26, forming a thin metallic film thereon. [0007] Residue deposits comprising the ejected atoms or small particles and byproducts are also deposited on the inner chamber walls 13 and other surfaces within the sealed vacuum chamber 12 during the deposition process. The accumulation of the residue deposits on the inner chamber walls 13 may be a source of contamination as a plurality of substrates 26 is successively processed in the vacuum chamber 12. Thus, the vacuum chamber 12 must be opened to atmosphere and cleaned after a predetermined amount of operation time has elapsed under vacuum or when contamination is detected on a substrate 26 that has undergone the deposition process. Opening and cleaning the vacuum chamber 12 is costly and time consuming. Therefore, it would be advantageous to clean the vacuum chamber 12 only when a predetermined amount of residue deposits have accumulated on the inner chamber walls 13 and other surfaces within the vacuum chamber 12. [0008] The magnetic field formed over the target surface 23 by the magnet assembly 20 confines the electrons emitted from the target 22 to an area near the target surface 23. This greatly increases the electron density and the likelihood of collisions between the electrons and the atoms of the inert gas in the space near the target surface 23. Therefore, there is a higher rate of ion production in plasma regions near the target surface 23 where the magnetic field intensity is stronger. Varying rates of ion production in different plasma regions causes the target surface 23 to erode unevenly. Typically, the configuration of the magnet assembly 20 produces a radial variation of thick and thin areas, or grooves, within a diameter of the target surface 23. FIG. 2 illustrates a cross-sectional perspective view of a typical erosion profile of a cylindrical metallic target 22, such as the metallic target 22 shown in FIG. 1, which has been used in a sputtering process. FIG. 2 illustrates a target surface 23 before erosion has occurred as well as an eroded target surface 32 that has eroded unevenly across the length of a diameter of the target 22. Due to the geometry of a magnetic field surrounding the target 22, the target surface 32 has eroded nearly symmetrically about a center line 30 dividing the length of the diameter. [0009] Referring now to FIGS. 1 and 2, the target 22 may comprise a rare metal, such as gold, platinum, palladium or silver, or may comprise, for example, aluminum, titanium, tungsten or any other target material conventionally employed in the semiconductor industry. Therefore, it is advantageous to consume as much of the target 22 material during sputter deposition processes as possible before replacing an eroded target 22. Further, replacing an eroded target 22 before the end of its useful life may be a difficult and time-consuming task. However, it is important to replace the target 22 before a groove "punches through" the target 22 material and exposes portions of the cathode assembly 18 to erosion, causing damage to the cathode assembly 18 and contaminating the sputtering apparatus 10. For example, the target 22 material in the area of grooves 28 shown in FIG. 2 may erode before the remainder of the target 22 material and expose the cathode assembly 18 to ionic bombardment from the surrounding plasma. [0010] It may also be advantageous to replace or condition the sputtering target 22 when certain characteristics of the target surface 23 become degraded during the sputtering process. For example, the smoothness of the target surface 23 may degrade over time. The roughened target surface 23 may affect the consistency of the deposition formation on the substrate 26 and may also be an indication of the amount of target 22 consumption. Therefore, it may be advantageous to replace the target 22 when the target surface 23 reaches a predetermined roughness level. [0011] As another example of degraded target surface 23 characteristics, certain targets 22, such as targets 22 comprising Ag.sub.2Se (hereinafter "silver selenide"), may exhibit hair-like growths or asperities (not shown) during the sputtering process. A portion of the asperities may be ejected from the target surface 23 during the plasma ion bombardment and land on substrate 26, forming defects therein. Typically, by the time the asperities have grown on the target surface 23 so as to create noticeable defects on the substrate 26, the target 22 is no longer useful and must be replaced. Therefore, to avoid forming defects on the substrate 26 and to prolong the useful life of the target 22, it may be advantageous to detect the asperities while the vacuum chamber 12 is under vacuum. [0012] The useful life of a metallic sputtering target 22 is typically estimated by determining the cumulative deposition time for the target 22. A deposition time is chosen in an attempt to guarantee that the target 22 material will never be completely removed at any given location and may take into account the thickness of the target 22, the material used for the target 22, and the effect of intensifying and confining the plasma over the target surface 23 by a magnetic field generated by the magnet assembly 20 in a predetermined configuration. However, if the characteristics of the plasma distribution change due, for example, to reconfiguring the magnet assembly 20 to produce a magnetic field with a different geometry, the erosion of the target surface 23 may be changed and could result in localized enhanced metal removal and the possible punching through of target 22 to the cathode assembly 18 before the expiration of the estimated deposition time. [0013] Directly measuring the characteristics of the target surface 23 or the vacuum chamber 12 is difficult and time consuming. Opening the vacuum chamber 12 to inspect the target surface 23 or inner chamber walls 13 requires several hours of idle time while the vacuum chamber 12 is baked out under post-vacuum inspection. Accurate measurement of the target surface 23 while the sputtering apparatus 10 is under vacuum is difficult because the gap distance d between the target 22 and the pedestal 24 may be as small as 25 millimeters. Typical measurement devices are too large to be inserted into the gap between the target 22 and the pedestal 24 to profile the target surface 23 while the vacuum chamber 12 is under vacuum. Further, measurement devices placed near the target 22 during a sputtering process may be damaged by exposure to metal deposition. [0014] In view of the above-noted shortcomings in the art, it would be advantageous to prevent contamination from residue deposits on the inner chamber walls 13 and other surfaces and to prevent premature replacement, over-consumption or degradation of the target 22 by providing a technique and device to measure the inner chamber walls 13 and the target surface 23 while the vacuum chamber 12 is under vacuum. BRIEF SUMMARY OF THE INVENTION [0015] The present invention, in a number of embodiments, relates to methods and apparatus for measuring the characteristics of a metallic sputtering target and other surfaces within a sputtering chamber. [0016] An apparatus according to one embodiment of the present invention may comprise a sensor configured to emit a first energy beam toward a target surface and to detect a second energy beam emitted from the target surface. The sensor may be coupled to a thin profile arm configured to move or transport the sensor over the target surface between the target and a substrate support pedestal to a plurality of measurement locations. The arm may be configured to attach to a robotic device. The sensor and the arm are configured, positioned and sized to be inserted into a narrow gap existing between the target surface and the pedestal. The arm may also be configured to remove the sensor from the gap and to shield the sensor during a sputtering process. [0017] In another embodiment of the present invention, the sensor may comprise a source element configured to emit a collimated light beam and at least one detector. According to one aspect of the invention, the at least one detector is arranged as a linear array of detection elements and the source element is positioned so as to emit the collimated light beam at an acute angle with respect to the linear array. The linear array is positioned relative to the source element so as to be illuminated by a reflection of the collimated light beam. The distance from the sensor to the target surface or the percentage of target erosion may be calculated by determining the location in the array of the detection element or elements illuminated by the reflection of the collimated light beam. According to another aspect of the invention, the at least one detector may be configured, positioned and sized to collect a coherent reflection of the collimated light beam and a substantial portion of scattered light beams from the target surface. The roughness of the target surface may be calculated by comparing the coherent reflection and scattered light beams. According to a further aspect of the invention, the sensor may comprise a source configured to emit an energy beam substantially parallel to the target surface toward the at least one detector. The presence of asperities on the target surface may be detected by analyzing the energy beam after passing proximate to the target surface. [0018] An apparatus according to yet another embodiment of the present invention may comprise a sensor configured to emit a first energy beam toward a surface in a chamber and to detect a second energy beam emitted from the surface to analyze residue deposits thereon. The sensor may be coupled to a thin profile arm configured to move or transport the sensor proximate to the surface. Alternatively, the sensor may be positioned outside the chamber and configured to emit the energy beam through a window in the chamber. The sensor may be configured to perform a spectral analysis on the second energy beam. [0019] In yet another embodiment of the present invention, a sensor may comprise a transmitter optically coupled to a source collimator configured to collimate a light beam as it exits an optical fiber. The sensor may further comprise a receiver optically coupled to one or more collection collimators, each collection collimator being configured to collect a light beam incident thereon into a corresponding optical fiber. [0020] The present invention, in additional embodiments, also encompasses a sputter deposition system incorporating the sensors of the present invention and methods of measuring surface characteristics. [0021] One method according to the present invention comprises emitting an energy beam, illuminating a first location on a target surface, detecting a reflection of the energy beam from the first location, and analyzing the detected reflection of the energy beam to determine a distance from the point of emission to the first location. Another method according to the present invention comprises detecting a coherently reflected portion of an energy beam from a target surface, detecting a scattered portion of the energy beam, and relating the coherently reflected portion and the scattered portion to a surface roughness. Yet another method according to the present invention comprises emitting an energy beam substantially parallel to a target surface, measuring a change to the energy beam, and relating the change to a presence of asperities on the target surface. A further method according to the present invention comprises performing a spectral analysis on an energy beam received from a surface. Continue reading... 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