FOR TUNING ELECTRICAL SKEWS

BACKGROUND OF THE INVENTION

Field of the invention

[0001 ] The present invention relates generally to a plasma processing apparatus for fabricating electronic substrates in which plasma is excited by RF power applied between electrodes. More specifically, the present invention relates to a liner assembly disposed inside the plasma processing apparatus for balancing RF current flow launched from the electrodes.

Description of the prior art

[0002] Electronic devices, such as flat panel displays and integrated circuits, commonly are fabricated by a series of process steps in which layers are deposited on a substrate and the deposited material is etched into desired patterns. The process steps commonly include physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma enhanced CVD (PECVD) and plasma process. Specifically, the plasma process requires supplying a process gas mixture to a vacuum chamber called a chamber body, and then applying electrical or electromagnetic power (RF power) to excite the process gas to a plasma state. In other words, the process gas is excited into the plasma by the RF current launched from electrodes. The plasma decomposes the gas mixture into ion species that perform the desired deposition or etch process. [0003] Generally, the substrate can be delivered from the transfer chamber to the chamber body via transfer mechanisms (e.g. robot blade) and be placed on a support assembly (e.g. susceptor or pedestal) of each chamber body for processing.

Furthermore, the chamber body may also comprise a chamber liner to protect the inner walls of the chamber body. Please refer to FIG. 1A. FIG. 1 A illustrates a perspective view of the traditional chamber liner. As shown in FIG. 1 A, to receive the substrate delivered from the transfer chamber, the chamber liner 90, disposed inside a chamber body, usually has a corresponding slot 902 for receiving the substrate which is aligned with the slit valve tunnel of the chamber body.

[0004] During substrate processing, RF currently launched from the electrodes returns to the power source on the surface of the chamber liner. Since the RF return current does not travel across the gap defined by the slot 902, the RF return current travels "around" the slot 902. This causes an area of RF current concentration at the lateral edges of the slot 902, and an area of low RF current to the top and bottom of the slot, thereby causing an azimuthal asymmetric perturbation in RF current flow, as illustrated in FIG. 1 B.

[0005] FIG. 1 B illustrates a schematic view of the traditional chamber liner 90 from line A-A to line B-B for indicating asymmetric RF current flow according to FIG. 1 A. As shown in FIG. 1 B, RF current flow (shown by dotted lines l ₉₀ ) is perturbed by the slot 902, that is, the slot 902 creates area of high concentration l ₉₂ which can lead to an azimuthal asymmetry in the electromagnetic fields and ultimately the plasma causing a non-uniform etch rate relative to the slot 902. [0006] The electrical skews could hardly be prevented in the plasma process because the traditional chamber liner failed to provide a balanced RF current flow and led to the defective plasma process. It is important that the RF current distribution within the chamber be symmetric, such that the electromagnetic fields for the plasma to provide the uniform azimuthal etch or deposition rate. Therefore, a need exists for balancing RF current flow along the chamber liner that prevents the above-mentioned problems.

SUMMARY OF THE INVENTION

[0007] Embodiments of the invention provide a liner assembly configured to balancing RF current flowing thereon. According to one embodiment of the invention, a liner is provided that comprises two or more slots to provide an axial symmetric RF current path, wherein one slot is a substrate access port.

[0008] In another embodiment of the invention, a plasma processing apparatus is provided that includes a liner for balancing RF current flow within the apparatus.

[0009] In one embodiment of the invention, the plasma processing apparatus includes a chamber body having a liner disposed therein. The line includes two or more slots formed therethrough for providing an axial symmetric RF current path.

[0010] The additional embodiments of the present invention will no doubt become understood to those of ordinary skill in the art after reading the following detailed description, which is illustrated in following figures and drawings. BRIEF DESCRIPTION OF THE APPENDED DRAWINGS

[0011] The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:

[0012] FIG. 1 A illustrates a perspective view of the conventional chamber liner.

[0013] FIG. 1 B illustrates a projection of the conventional chamber liner of FIG. 1 A taken along section line A-A to line B-B for indicating asymmetric RF current distribution of the surface of the liner.

[0014] FIG. 2 illustrates a schematic view of a plasma processing apparatus according to one embodiment of the invention.

[0015] FIG. 3A illustrates a perspective view of the chamber liner according to one embodiment of the invention.

[0016] FIG. 3B illustrates a projection of the chamber liner from line C-C to line D-D for indicating substantially symmetric RF current flow according to FIG. 3A.

[0017] FIG. 4 is a flow chart illustrating one embodiment of a plasma process according to one embodiment.

[0018] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. DETAILED DESCRIPTION

[0019] FIG. 2 illustrates a schematic view of a plasma processing apparatus according to one embodiment of the invention. The plasma processing apparatus may be a plasma etch chamber, a plasma enhanced chemical vapor deposition chamber, a physical vapor deposition chamber, a plasma treatment chamber, an ion implantation chamber or other suitable vacuum processing chamber. As shown in FIG. 2, the plasma processing apparatus 1 comprises a chamber lid 10, a chamber body 12 and a substrate support assembly 14. The chamber body 12 supports the chamber lid 10 to enclose a processing region. The substrate support assembly 14 is disposed in the chamber body 12 below the lid 10. All components of the plasma processing apparatus 1 are described below respectively.

[0020] In one embodiment, the chamber lid 10 includes a showerhead assembly 102, a lid plate 104, an insulator 106 and a spacer 108. The lid plate 104 is generally seated on the chamber body 12 and is typically coupled thereto by a hinge (not shown) to allow the chamber lid 10 to be opened, exposing the interior of the chamber body 12. The showerhead assembly 102 is typically comprised of a conductive material and coupled to a RF power source 42 to serve as an electrode for driving a plasma 16 formed within the chamber body 12. In other embodiments, an RF power source 44 may be coupled to the substrate support assembly 14, such that the support serves as the electrode. The chamber lid 10 is generally connected to a gas source 40 for introducing a process gas into the processing volume.

Specifically, the lid plate 104 may comprise of an injection port 104a for receiving the process gases from the gas source 40, the gases then flowing into the interior of the chamber body 12 through the showerhead assembly 102. The showerhead assembly 102 facilitates uniform process gas delivery to a substrate 2 disposed on the substrate support assembly 14.

[0021 ] The showerhead assembly 102 is electrically isolated from the chamber lid 10 by the insulator 106. The insulator 106 may comprise an inner ledge (not shown) for supporting the showerhead assembly 102. The spacers 108 are RF conductive and disposed between the chamber body 12 and the lid plate 104 and provide part of an RF return path, as further discussed below.

[0022] The chamber body 12 comprises a chamber sidewall 122 and a bottom wall 124. The chamber sidewall 122 and bottom wall 124 may be fabricated from a unitary block of aluminum. The chamber sidewall 122 and the bottom wall 124 of the chamber body 12 define a processing volume for confining the plasma 16. The processing volume is typically accessed through a slit valve tunnel 1222 in the chamber sidewall 122 that facilitates movement of a substrate 2 into and out of the chamber body 12. In practice, a slit valve tunnel 1222 is formed on the chamber sidewall 122 for allowing entry and egress of the substrate 2 to/from the chamber body 12.

[0023] A liner assembly 3 is disposed inside the processing volume. In one embodiment, the liner assembly 3 includes a chamber liner 30 and a bottom liner 32. The liner assembly 3 is removable to allow periodic cleaning and maintenance. The liner assembly 3 may also include a passage 202 for flowing a coolant therethrough so that the temperature of the liner may be regulated. The chamber liner 30 includes two or more slots 34 and is generally cylindrically-shaped, but may alternatively take the shape of the interior wall of chambers having other geometries. At least one of the slots 34 is suitable for passage of the substrate 2, and is aligned with the slit valve tunnel 1222. In one embodiment, the slots 34 have an elongated horizontal orientation. The bottom liner 32, engaged to the chamber liner 30, comprises a bowl portion and an optional innermost cylindrically portion, wherein the chamber sidewall 122 and the bottom wall 124 are shielded from the plasma 16 by the chamber liner 30 and the bottom liner 32. In practice, the liner assembly 3 is disposed about the substrate support assembly 14 and circumscribes the interior, vertical surfaces of the chamber body 12. The liner assembly 3 may further comprise an outer ledge (not shown) for being detachably fixed the liner assembly 3 to the chamber sidewall 122. The liner assembly 3 may be constructed of any process compatible material, such as aluminum or yttria.

[0024] The slots 34 are formed symmetrically through the chamber liner 30 for providing an axial symmetric RF current path. As discussed above, one of the slots 34 is aligned with the slit valve tunnel 1222, while the other slots 34 are distributed around the chamber liner 30 in a position that compensates for changes RF current density and/or distribution present on the liner 30 due to the apertures of the slot 34 aligned with the slit valve tunnel 1222. In one embodiment, the slots 34 are arranged in a polar array, and may be spaced apart equidistantly in a substantially horizontal orientation (i.e., in an orientation perpendicular to a center axis of the liner assembly 3. [0025] The substrate support assembly 14 supports the substrate 2 during the processes within the chamber body 12. In practice, the substrate support assembly 14 may include at least one embedded heating element (not shown). Moreover, the substrate 2 can be, but not limited to, a flat panel display, round wafer, liquid crystal display, glass panel substrate, plastic substrate, and the like. The substrate support assembly 14 may also be electrically connected to a RF power source 44 to provide the substrate 2 bias as desired for particular processes. In this embodiment, the showerhead assembly 102 (first electrode) and the substrate support assembly 14 (second electrode) can apply an RF power across processing volume for exciting the process gases into the plasma 16.

[0026] According to one embodiment of the invention, the symmetrically slotted chamber liner 30 can be further shown in FIG.3A. FIG. 3A illustrates a perspective view of the chamber liner according to one embodiment of the invention. As shown in FIG. 3A, the chamber liner 30 has a plurality of symmetrically formed slots 34, wherein one of the slots 34 sized for transferring substrates. The other slots 34, for example, are designed for tuning the electrical skews in the plasma process, for example, to compensate of the RF current density concentrations at the edges of the slot 34 utilized for substrate transfer through the liner. It should be noticed that the slots shall be spaced symmetrically (i.e., in a polar array about the centerline of the liner 30) to provide an axial and azimuthally symmetric RF current return path for the RF current launched from the electrode(s) and returning to the power source through chamber liner 30. [0027] In one embodiment, the plurality of slots 34 of the have the same size. In another embodiment, the plurality of slots 34 are two slots spaced 180 degrees apart. In another embodiment, the plurality of slots 34 are three slots spaced 120 degrees apart. In another embodiment, the plurality of slots 34 are four slots spaced 90 degrees apart.

[0028] FIG. 3B illustrates a schematic projection of the chamber liner 30 taken from line C-C to line D-D, illustrating symmetric RF current flow across the liner 30. As shown in FIG. 3B, the slots 34 are of equal size and symmetrically formed through the chamber liner 30 such that the paths of RF current flow (shown by dotted lines l ₃₀ ) are symmetrically perturbed by the slots 34. This causes symmetric areas of increase current density l ₃₂ to be uniformly distributed around the chamber liner 30. It should be noticed that the slots 34 do not need to be disposed on the chamber liner 30 at the same vertical level as long as the pattern of slots 34 are symmetric. Designers can create a desired path of the RF current flow l ₃₀ by changing the pattern/ location of the slots 34. In practice, the symmetry of RF current flow l ₃₀ can enhance azimuthal symmetry of the electromagnetic fields, and thereby enhance the uniformity of plasma processing results. It is also contemplated that the position of the slots 34 may be located to create an asymmetry of RF return current flow through the liner assembly 3 to tune out another electrical or conductance asymmetry within the processing apparatus 1 such that the resultant effect is a more uniformly distributed plasma within the processing chamber, thereby substantially eliminating azimuthal plasma skews. [0029] To clearly describe the features and spirits of the invention, a flow diagram is provided in FIG. 4 for illustrating one embodiment of a plasma process 400 performed in accordance to one embodiment of the invention. The process 400 begins at S50 by transferring a substrate into a plasma processing apparatus 1 having a liner assembly 3 with two or more slots 34 formed therethrough, the slots 34 selected to provide a symmetrical distribution of RF current flow through the liner assembly 3 during processing. At S52, process gases are introduced into the chamber body 12 from the gas source 40. At S54, power is provided to the electrode (i.e., from one or both of the showerhead assembly 102 or substrate support assembly 14) to excite the process gases within the processing apparatus 1 into the plasma 16. At S56, the substrate is processed in the presence of the plasma. While the power is applied to the electrode during processing, RF current flows symmetrically through the liner assembly 3 to return to the power source as discussed above. The symmetrical RF current flow through the liner assembly 3 enhances azimuthal uniformity of the plasma within the chamber, thereby enhancing processing results. Plasma processing the substrate may include, but is not limited to, performing an plasma etch process, a plasma enhanced chemical vapor deposition process, a physical vapor deposition process, a plasma treatment process, an ion implantation process or other plasma assisted semiconductor process.

[0030] In summary, the present invention provides the liner assembly with symmetric slots for balancing RF current flow coupled to the liner assembly.

Furthermore, the slots can also be formed in certain patterns for creating desired path of the RF current flow to tune the azimuthal plasma skews. [0031 ] With the example and explanations above, the features and spirits of the embodiments of the invention are described. Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teaching of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.