GAS DISTRIBUTION SYSTEM

Abstract: The present invention generally provides a substrate processing chamber (14) having a gas distributor (54) that provides a uniform distribution of a gas concentration within the chamber. More particularly, the present invention provides an apparatus for distributing a process gas within a processing chamber that provides a uniform distribution of gas concentration within the processing chamber. Another aspect of the present invention provides for such an apparatus for gas distribution that can be used in CVD, PVD and etching chambers. The present invention generally provides an apparatus for distributing gas within a substrate processing chamber comprising a gas distributor (54) made of gas permeable material having a conduit (50) disposed within the gas distributor.

Description: GAS DISTRIBUTION SYSTEM BACKGROUND OF THE INVENTION Field of the Invention The present invention generally relates to the field of semiconductor substrate processing equipment. More particularly, the present invention relates to a gas distribution system that provides uniformity in the distribution and diffusion of a gas concentration within a processing chamber. Background of the Related Art In the fabrication of integrated circuits, vacuum process chambers are generally employed to process semiconductor substrates. The processes carried out in the vacuum chambers typically provide the deposition or etching of multiple metal, dielectric and semiconductor film layers on the surface of a substrate. Examples of such processes include chemical vapor deposition (CVD), physical vapor deposition (PVD), and etching processes. Typically, plasma reactor equipment is employed for depositing layers or films of conductive materials in various patterns, configurations and thicknesses to form microcircuits. Dry etching of semiconductor materials can also be conducted with chemical vapor transport systems to selectively remove desired areas of such materials to form a desired pattern or configuration. A variety of gases are required to be introduced into the process chamber for carrying out these processes. These gases are also commonly used in the processing of substrates to act as a system purge, e.g., nitrogen, or as a reactant, e.g., hydrogen and oxygen. To ensure a uniform progress of the process, a uniform distribution of gas concentration within the processing chamber is highly desirable. The reason for desiring uniform gas distribution is that variations in the gas concentration within the processing chamber produce non-uniform deposition or non-uniform etch resulting in a non-planar topography which can lead to yield loss, incomplete etch and device failures. Figure 1 is a partial schematic cross-sectional view of a conventional semiconductor processing chamber for a sputtering process. Figure 1 shows a PVD chamber wherein a sputtering gas is directly supplied from a nozzle 2 mounted on an upper portion of the processing chamber wall 4. In some chambers, a heating or cooling gas, is delivered through the pedestal (not shown) to heat or cool the backside of the substrate. In a non reactive process, the same gas may be used for the backside gas as used for sputtering. However, if the process is a reactive process, typically no reactive backside gas is used, because unwanted deposition may occur on the backside of the substrate 1 that may contaminate subsequent processing. Thus, in a non reactive process, the same gas may be delivered through the nozzle and the pedestal, whereas in a reactive process, the reactive gas source would principally be the nozzle and, if backside gas is desired, the backside gas may be some inert gas. Typically, only one or two units of nozzle 2 are provided in connection with the chamber, and the resulting distribution of gas concentration within the chamber is not uniform, because each individual nozzle provides a stream of gas which is highly concentrated along the stream path 6. The uniformity can be improved with additional nozzles proportionately spaced within the chamber, because more regions within the chamber obtain the same gas concentration as that along the gas stream path. However, the distribution of the gas concentration within the chamber remains inconsistent, because the gas concentration is still more highly concentrated along the gas stream path of each nozzle and less concentrated in the regions between the gas stream paths. Because of the inconsistent gas concentration within the chamber during reactive sputtering, the degree of reaction between a process gas and the sputtering materials varies between different positions within the chamber. As a result, the deposition rate and the quality of the film deposited on the substrate vary with the concentration of the processing gas. One attempt to provide a more uniform distribution of gas within a chamber utilizes a ring-shaped pipe having a plurality of gas jets distributed evenly around the ring. Figure 2 is a sectional view of a thin-film deposition apparatus having two ring shaped pipes 5a and 5b with a plurality of gas jets 7 as described by U.S. Patent No. 4,817,558 entitled "Thin-Film Depositing Apparatus". Each gas jet 7 directs reaction gas downward toward the substrate surface to be processed. However, this apparatus suffers similar shortcomings as a chamber having multiple gas nozzles, because the gas distribution is still non-uniform and concentrated along the gas stream of each gas jet. Another attempt to provide uniform distribution of gas flow in a chamber combines a filter and a spiral gas supply nozzle, having a plurality of gas venting holes pointing away from the filter disposed within a region defined by the top portion of the chamber and the filter as described by U.S. Patent No. 4,986,216, entitled "Semiconductor Manufacturing Apparatus". Figure 3 is a sectional view of a deposition apparatus, having a spiral gas supply 60 and a filter 62. The gas is supplied into the region A defined by the filter 62 and the upper portion of the chamber through gas nozzles 64 on the spiral gas supply 60. The gas pressure build-up within this region forces the gas through the filter 62 into the processing region B of the chamber. A similar filter 66 and spiral exhaust nozzle 68 are also provided at the bottom portion C of the chamber to extract the gas out of the chamber. Although this supply and filter combination may provide a more uniform gas flow, the uniform gas flow is only provided in the area directly under the gas distributor. Furthermore, this gas distributor can only be used in a CVD or etching chamber, but not in a PVD chamber because the PVD sputtering target generally is positioned directly above the surface of the substrate at the same region designed to be occupied by the gas distributor. Therefore, there is a need for a gas distribution apparatus that provides uniformity in the distribution of a gas concentration within a processing chamber which can be utilized in both a PVD chamber and a CVD chamber, as well as perhaps an etching chamber and other chambers. SUMMARY OF THE INVENTION The present invention generally provides a substrate processing chamber having a gas distribution system that provides a uniform distribution of gas concentration within the processing chamber. The present invention also provides an apparatus for distributing gas within a substrate processing chamber comprising a tubular gas distributor made of gas permeable material having a conduit disposed within the gas distributor. Another aspect of the present invention provides an auxiliary shield made of an air permeable structure, such as a mesh made of sintered material, disposed between a gas distributor and a sputtering target. Another aspect of the present invention provides for such an apparatus for gas distribution that can be used in PVD, CVD, etching, and other chambers. BRIEF DESCRIPTION OF THE DRAWINGS So that the manner in which the above recited features, advantages and objects of the present invention are attained can be understood in detail, a more particular description of the invention, briefly summarized i όve, tήay be had by reference to the embodiments thereof which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. Figure 1 is a partial schematic cross-sectional view of a conventional semiconductor processing chamber for a sputtering process. Figure 2 is a sectional view of a conventional thin-film deposition apparatus having two ring shaped pipes with a plurality of gas jets. Figure 3 is a sectional view of a conventional deposition apparatus having a spiral gas supply and a filter. Figure 4 is a cross-sectional schematic view having a simplified sputtering apparatus with a gas distribution apparatus of the present invention disposed therein. Figure 5 is a partial schematic view of an embodiment of the present invention in a PVD chamber showing the resulting gas distribution within the chamber. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention generally provides a gas distribution apparatus that provides uniformity in the distribution of a gas concentration within a processing chamber. Another aspect of the present invention provides a gas distribution apparatus that can be utilized in CVD, PVD and etching processing chambers. For clarity and ease of description, the following description refers primarily to a PVD processing chamber and system although die present invention is equally applicable to other types of processes that utilize gas delivery systems such as a CVD or etching system. A substrate processing system typically comprises a combination of loadlocks through which the substrates are introduced into the system, a transfer chamber which houses a robot that moves the substrates within the system, and a plurality of process chambers each adapted to perform a specific process step on the substrates. Typically, the processes performed in the process chambers involve the deposition of a thin film of material on the surface of the substrate by either PVD or CVD. In a PVD system, a gas is introduced into the chamber and excited into a plasma to sputter material off a target onto a substrate. In a CVD processing system, the films are deposited by introducing the material to be deposited on the substrate into the process chamber in the form of a gas so that more uniform films may be created. Often, the material to be deposited is in the form of a liquid at room temperature. Therefore, the material is vaporized into a carrier gas in an evaporator, such as a bubbler. The carrier gas supporting the material is then passed into the process chamber for deposition of the material onto the substrate. The process system generally includes a gas delivery system having inlet and outlet valves, a liquid flow meter, communication lines, an injection control valve, bypass lines, and an evaporator including a liquid supply, to direct and control the flow of the carrier gas containing the material to the process chamber. Other typical components include measurement devices, (e.g., thermocouples), monitor displays, degassers, gas supplies, pumps, and temperature control systems (e.g., heaters). The gas delivery system supplies and controls all of the gases necessary for the process in each process chamber. Figure 4 is a cross-sectional schematic view of a simplified sputtering apparatus, having a gas distribution apparatus of the present invention disposed therein. The processing chamber 14 generally includes a chamber enclosure wall 24, having at least one gas inlet 26 and an exhaust outlet 28 connected to an exhaust pump (not shown). The pedestal 18 includes a generally planar surface 22 for receiving the substrate 16 thereon, so that the top surface 20 of the substrate 16 is generally parallel to the planar surface 22 of the pedestal 18. The substrate support pedestal 18 is typically disposed at a lower portion of the chamber 14, and the target 10, having a sputtering surface 12, is typically situated at an upper portion of the chamber 14. The target 10 is electrically isolated from the enclosure wall 24 by an insulating member 30, and the enclosure wall 24 is preferably grounded, so that a negative voltage may be maintained on the target 10 with respect to the grounded enclosure wall 24. A power supply 52 applies a negative voltage to the target 10 with respect to the enclosure wall 24, so as to excite the gas into a plasma state. The power supply 52 used for biasing purposes may be any type of power supply as desired, including DC, pulsed DC, AC, RF and combinations thereof. It is preferred that the chamber 14 further includes an inductive coil (not shown) coupled to a power supply (not shown) to provide an inductively coupled plasma. The enclosure wall includes a slit valve 48 through which the substrate 16 is typically passed through a load lock (not shown). Pedestal 18 is lowered by a drive mechanism 32 below the clamp ring 34 suspended on the shield 36, so that the bottom of the pedestal 18 is close to a pin positioning platform 38. The pedestal 18 typically includes three or more vertical bores (not shown), each of which allows a vertically slidable pin 40 to pass therethrough. The vertically slidable pin 40 is connected to a pin platform 38 which is operated by a second lift mechanism 42. An annular clamp ring 34 may be used in the chamber, so that the inner portion 44 contacts the substrate 16 during deposition and rests on the upturned wall portion 46 of the shield 36 when the substrate is lowered, as explained below. The inner portion 44 of the clamp ring 34 is slightly smaller than the diameter of the substrate 16, such that the clamp ring 34 shields the circumferential edge of the substrate 16 from receiving deposition. The gas inlet 26 communicates with a conduit 50 of the gas distributor 54, having pores 58. In the preferred embodiment, the conduit 50 is large enough to allow enough flow of the gas from the gas inlet 26 throughout the gas distributor 54, so that gas pressure builds up within the conduit 50 and diffuses the gas out through the pores 58 substantially evenly into the chamber 14, so as to provide a substantially uniform deposit on the substrate. Typically, the conduit 50 has a diameter on the order of millimeters (mm) while the pores 58 have diameters on the order of micrometers (μm). However, the sizes of the pores 58 and the conduit 50 can be selected according to the gas pressure of the processing gas supplied into the gas distributor 54 and the required flow rate of the processing gas out of the gas distributor 54 into the processing chamber. In a PVD chamber, the gas distributor 54 is preferably situated around the sputtering target 10 and above the sputtering surface 12. Preferably, an auxiliary shield 56 is installed between the gas distributor 54 and the sputtering target 10 to prevent sputtered particles from adhering to the gas distributor 54 and thus blocking the small pores 58 on the gas distributor 54. As shown in Figure 5, the auxiliary shield may be an annular screen surrounding the lateral surface of the sputtering target 10 and extends from the top portion of the PVD chamber to a distance below the sputtering surface of the sputtering target 10. The auxiliary shield 56 is preferably an air permeable structure, such as a mesh made of sintered metal. Because the auxiliary shield 56 is gas permeable, the process gas can pass through the auxiliary shield 56 substantially unhindered, but the sputtered particles are blocked off by the auxiliary shield 56 and prevented from adhering to the gas distributor 54. Figure 5 is a partial schematic view of an embodiment of the present invention in a PVD chamber showing a detailed view of the gas distributor 54 and resulting gas distribution in the chamber. The gas distributor 54 is preferably a circular tube made of a porous material, such as a ceramic, although other tubular shapes could be used, including rectangular, square, and elliptical geometries. The gas distributor 54 may be manufactured through a sintering process that allows control of the resulting porosity of the gas distributor. Preferably, the gas distributor 54 is homogeneously porous, so that it provides substantially uniform gas permeability and diffusion. Alternatively, the gas distributor 54 can be constructed with no hole patterns associated with the material, and the pores can be manufactured with a random distribution within the material itself, as long as a high number of pores are manufactured in the gas distributor, so that the pores appear to be evenly distributed for a substantially uniform dispersion from the gas distributor. The process gases are preferably supplied through a plurality of gas inlets 26 connected to the gas distributor 54, even though one gas inlet is sufficient to provide for the process gases to travel freely within the gas distributor 54 in the conduit 50 and through the porous material into the processing chamber. However, a plurality of gas inlets 26 evenly spaced about the circumference of the processing chamber 14 enhances the flow of gas within the conduit 50 of the gas distributor 54. Also, having more gas inlets can reduce the required size (i.e., diameter) of the conduit 50 and the overall size of the gas distributor 54. In operation, before a material layer can be sputtered onto the substrate 16, the substrate 16 is typically passed through a load lock (not shown) communicating with a slit valve 48 in the enclosure wall 24, and positioned within the chamber 14 by a robot arm, blade or other substrate handling device (not shown) to be received on the support pedestal 18. In preparation for receiving a substrate, the substrate support pedestal 18 is lowered by a drive mechanism 32 well below the clamp ring 34 suspended on the shield 36, so that the bottom of the pedestal 18 is close to a pin positioning platform 38. When the pedestal 18 is in the lowered position just described, the upper tip of each pin 40 protrudes above the upper surface of the pedestal 18. The upper tips of the pins 40 define a plane parallel to the upper surface of the pedestal 18. A conventional robot arm (not shown) having a robot blade (not shown) typically carries the substrate 16 into the chamber 14 and places the substrate 16 above the upper tips of the pins 40. A second lift mechanism 42 moves the pin platform 38 upwardly, to place the upper tips of the pins 40 against the underside of the substrate 16 and additionally lift the substrate 16 off the robot blade (not shown). The robot blade then retracts from the chamber 14, and the lift mechanism 32 raises the pedestal 18 above the tips of the pins 40, thereby placing the substrate 16 onto the top surface of the pedestal 18. The lift mechanism 32 continues to raise the pedestal 18 until the substrate 16 is an appropriate distance from the target 10 and the sputtering surface 12, so that the film deposition process can begin. When an annular clamp ring 34 is used, the substrate 16 contacts the inner portion 44 of the annular clamp ring 34, resting on the upturned wall portion 46 of the shield 36. The inner diameter of the clamp ring 34 is slightly smaller than the diameter of the substrate 16, such that the clamp ring 34 shields the circumferential edge of the substrate 16 from receiving deposition. Sputter deposition processes are typically performed with a gas, such as argon. The gas is pumped into the vacuum chamber 14 through the gas inlet 26 at a selected flow rate regulated by a mass flow controller (not shown). The supply gas flows from the gas inlet 26 into the conduit 50 and fills the conduit 50 before exiting through the pores 58. In the preferred embodiment, the gas flows through the gas distributor 54 and diffuses the gas out through the pores 58 substantially evenly into the chamber 14, so as to provide a substantially uniform deposit on the substrate. The power supply 52 applies a negative voltage to the target 10 with respect to the enclosure wall 24 and excites the gas into a plasma state. Argon ions from the plasma bombard the target sputtering surface 12 and sputter atoms and other particles of target material from the target 10. The sputtered material then deposits on the substrate 16, except for the periphery thereof that is shielded by the clamp ring 34. The material layer may, if desired, be formed over one or more dielectric, metal or other layers previously formed on the substrate 16, and may fill holes in the dielectric or other layer to form a via, line or contact. After the film layer has been deposited on the substrate 16, the substrate 16 is removed from the chamber 14 by reversing the sequence of steps by which it is carried into the chamber 14. Specifically, the lift mechanism 32 lowers the pedestal 18 below the upturned wall portion 46, so that the clamp ring 34 descends so that the weight of the clamp ring 34 is supported by the shield 36, not by the substrate 16 and pedestal 18. The second lift mechanism 42 then raises the pins 40 until the substrate 16 is lifted above the surface of the pedestal 18. The robot blade is then able to enter the chamber 14 to a position below the substrate 16 before the pins 40 are lowered which places the substrate 16 onto the robot blade. Then the robot blade retracts with the processed substrate 16 thereon out of the chamber 14. An alternative embodiment of the present invention includes a plurality of bulb- shaped gas nozzles made of a porous material, such as a ceramic. Preferably, the bulb- shaped gas nozzles are disposed evenly around the top portion of the processing chamber. Each bulb-shaped gas nozzle has a hollow central region connected to a gas inlet, and the supply gas flows from the gas inlet into the hollow region and then is diffused into the chamber evenly through the pores. Uniformity in the distribution of the gas concentration is enhanced by the present invention because the gas distributor 54 provides approximately an equal amount of gas through the gas distributor 54 into the processing chamber. In contrast, conventional gas nozzles provide individual streams or jets of gas into the chamber where the distribution of gas concentration is concentrated at each individual nozzle's stream path. Thus, because the gas distributor of the present invention provides a uniform distribution of a gas concentration in the processing chamber, a uniform reaction between the process gas and the sputtering target results in a uniform deposition process which provides a quality uniform film on the entire substrate surface. While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims which follow.

Claims: What is Claimed Is: 1. An apparatus for distributing gas in a substrate processing chamber comprising: a. a tubular gas distributor made of gas permeable material disposed within the substrate processing chamber; and b. a gas supply inlet connected to the gas distributor. 2. The apparatus of claim 1 wherein the gas distributor comprises a porous ceramic tube. 3. The apparatus of claim 1 wherein the gas distributor comprises a porous sintered metal. 4. The apparatus of claim 1 wherein the gas distributor extends circumferentially within the processing chamber. 5. An apparatus for processing substrates comprising: a. a processing chamber; b. a substrate support disposed in the processing chamber; c. a gas distributor made of gas permeable material disposed in the chamber; and d. a gas supply inlet connected to the gas distributor. 6. The apparatus of claim 5 further comprising: a. a sputtering target surrounded by the gas distributor; and b. a shield disposed between the sputtering target and the gas distributor. 7. The apparatus of claim 6 wherein the shield comprises a mesh. 8. The apparatus of claim 6 wherein the shield comprises a gas permeable sintered metal. 9. The apparatus of claim 5 wherein the gas distributor comprises a porous ceramic tube. 10. The apparatus of claim 5 wherein the gas distributor is made of a porous sintered metal. 11. The apparatus of claim 5 wherein the gas distributor extends circumferentially within the processing chamber. 12. A method of distributing gas in a substrate processing chamber comprised of: a. providing a substrate processing chamber; b. allowing gas into a conduit connected to the chamber; c. distributing the gas from the conduit through a gas permeable material into the chamber. 13. The method of claim 12 wherein distributing the gas comprises distributing circumferentially within the processing chamber. 14. The method of claim 13 wherein distributing the gas comprises distributing substantially independently of individual jets of gas. 15. The method of claim 12 wherein distributing the gas comprises distributing substantially uniformly circumferentially. 16. The method of claim 14 wherein distributing the gas comprises distributing substantially uniformly circumferentially. 17. The method of claim 12 further comprising shielding the gas distributor from a sputtering target. 18. The method of claim 17 wherein shielding the gas distributor comprises restricting a flow of the sputtered material from the sputtering target through a shield.

Inventors: IKEDA TOWL, IKEDA, TOWL
Applicants: APPLIED MATERIALS INC, APPLIED MATERIALS, INC.
Application year: 1999
Main classification: H01J37
IPC codes: C23C14, C23C16, H01J37