Substrate support with symmetrical feed structure

Apparatus for processing a substrate is disclosed herein. In some embodiments, a substrate support may include a substrate support having a support surface for supporting a substrate the substrate support having a central axis; a first electrode disposed within the substrate support to provide RF power to a substrate when disposed on the support surface; an inner conductor coupled to the first electrode about a center of a surface of the first electrode opposing the support surface, wherein the inner conductor is tubular and extends from the first electrode parallel to and about the central axis in a direction away from the support surface of the substrate support; an outer conductor disposed about the inner conductor; and an outer dielectric layer disposed between the inner and outer conductors, the outer dielectric layer electrically isolating the outer conductor from the inner conductor. The outer conductor may be coupled to electrical ground.

FIELD

Embodiments of the present invention generally relate to substrate processing equipment.

BACKGROUND

As the critical dimensions of devices continue to shrink, factors that may have been irrelevant or of lesser import at large dimensions can become critical at smaller dimensions.

The inventors have provided an improved apparatus that may facilitate improved processing results when processing substrates.

SUMMARY

Apparatus for processing a substrate is disclosed herein. In some embodiments, a substrate support may include a substrate support having a support surface for supporting a substrate the substrate support having a central axis; a first electrode disposed within the substrate support to provide RF power to a substrate when disposed on the support surface; an inner conductor coupled to the first electrode about a center of a surface of the first electrode opposing the support surface, wherein the inner conductor is tubular and extends from the first electrode parallel to and about the central axis in a direction away from the support surface of the substrate support; an outer conductor disposed about the inner conductor; and an outer dielectric layer disposed between the inner and outer conductors, the outer dielectric layer electrically isolating the outer conductor from the inner conductor. In some embodiments, the outer conductor may be coupled to an electrical ground. In some embodiments DC energy may be provided to a second electrode via a second conductor extending along the central axis. In some embodiments, AC energy may be provided to one or more heater electrodes via a plurality of third conductors disposed symmetrically about the central axis. In some embodiments, the second and third conductors may be disposed within an axial opening of the inner conductor.

In some embodiments, a plasma processing apparatus may include a process chamber having an inner volume with a substrate support disposed in the inner volume, the substrate support having a support surface and a central axis; a first electrode disposed in the substrate support to provide RF power to a substrate when present on the substrate support; an inner conductor having a first end coupled to the first electrode about a center of a surface of the first electrode facing away from the support surface, wherein the inner conductor is tubular and extends away from the first electrode parallel to and about the central axis; a first conductor coupled to the inner conductor proximate a second end of the inner conductor, opposite the first end, the first conductor extending laterally from the central axis toward an RF power source disposed off-axis from the central axis, the RF power source to provide RF power to the first electrode; an outer conductor disposed about the inner conductor; and an outer dielectric layer disposed between the inner and outer conductors, the outer dielectric layer electrically isolating the outer conductor from the inner conductor.

DETAILED DESCRIPTION

Apparatus for processing a substrate is disclosed herein. The inventors have discovered that a substrate support having an asymmetric electrical feed structure to provide electrical power to an electrode disposed in the substrate support can cause process non-uniformities, for example, such as etch rate and etch dimension non-uniformities on a substrate disposed atop the substrate support. Thus, the inventors have provided a symmetrical electrical feed structure that may be incorporated within a substrate support to advantageously improve etch rate and/or etch dimension uniformities. In some embodiments, the inventive apparatus may advantageously reduce electromagnetic skew along the surface of a substrate by conducting electrical power to the various components of the substrate support via one or more conductors that are symmetrically arranged with respect to a central axis of the substrate support and/or by providing one or more elements for confining or uniformly distributing an electric and/or magnetic field.

FIG. 1depicts a schematic diagram of an illustrative etch reactor100of the kind that may be used to practice embodiments of the invention as discussed herein. The reactor100may be utilized alone or, more typically, as a processing module of an integrated semiconductor substrate processing system, or cluster tool, such as a CENTURA® integrated semiconductor substrate processing system, available from Applied Materials, Inc. of Santa Clara, Calif. Examples of suitable etch reactors100include the ADVANTEDGE® line of etch reactors (such as the AdvantEdge S or the AdvantEdge HT), the DPS® line of etch reactors (such as the DPS®, DPS® II, DPS® AE, DPS® HT, DPS® G3 poly etcher), or other etch reactors, available from Applied Materials, Inc. Other etch reactors and/or cluster tools, including those of other manufacturers may be used as well.

The reactor100comprises a process chamber110having a substrate support116disposed within a processing volume117formed within a conductive body (wall)130, and a controller140. A symmetric electrical feed through150may be provided to coupled electrical energy to one or more electrodes disposed within the substrate support116, as discussed below. The chamber110may be supplied with a substantially flat dielectric ceiling120. Alternatively, the chamber110may have other types of ceilings, e.g., a dome-shaped ceiling. An antenna comprising at least one inductive coil element112is disposed above the ceiling120(two co-axial elements112are shown). The inductive coil element112is coupled to a plasma power source118through a first matching network119. The plasma power source118typically may be capable of producing up to 3000 W at a tunable frequency in a range from 50 kHz to 13.56 MHz.

As illustrated inFIG. 1, the substrate support116may include a plurality of components, such as electrodes, heaters, and the like, which may operated by one or more mechanisms148disposed below the substrate support116. For example, and as shown inFIG. 1, the one or more mechanisms may be coupled to the substrate support116through an opening115disposed through the conductive body130. A bellows152may be provided to facilitate maintaining a seal between the interior of the process chamber and the outside of the process chamber while allowing the substrate support to move relative to the process chamber. For example, the bellows152may compress or expand as the substrate support116is raised or lowered within the processing volume117. The one or more mechanisms148may include a lift mechanism154that may be utilized to raise and lower the substrate support116relative to one or more plasma generating elements, such as the inductive coil elements112, disposed above the substrate support116. The one or more mechanisms148are described in further detail below and with respect toFIG. 4.

FIG. 2depicts a schematic side view of the substrate support116and symmetric electrical feed structure150in accordance with some embodiments of the present invention. As illustrated inFIG. 2, the substrate support may include a base200having a central opening202. The central opening202may be utilized, for example, to provide one or more conductors therethrough to couple one or more of radio frequency (RF), alternating current (AC), or direct current (DC) power from the one or more mechanisms148disposed below the substrate support116. The base200may have a protruding portion204to facilitate coupling the base200to other components of the process chamber.

The substrate support116may include a first electrode206disposed within the substrate support116to provide RF power to a substrate, such as the substrate114(shown inFIG. 1), when disposed on the substrate support116. The first electrode206may include a central axis208. An inner conductor210may be coupled to the first electrode206. The inner conductor210may be a cylindrical tube having a central axis aligned with the central axis208such that the inner conductor210may provide RF energy to the first electrode206in a symmetrical manner. The inner conductor210generally extends away from the first electrode206parallel to and about the central axis208. The inner conductor210may extend through the central opening202in the base200(as shown), through the bellows152(shown inFIG. 1), and into the one or more mechanisms148(as illustrated inFIG. 4, described below). The inner conductor210may comprise any suitable conducting material, such as copper (Cu), aluminum (Al), gold-plated copper, or the like. In some embodiments, the inner conductor may comprise copper.

The substrate support116further includes an outer conductor212disposed about at least portions of the inner conductor210. The outer conductor212, similar to the inner conductor210, may be tubular in shape and extend generally parallel to and about the central axis208. The outer conductor212may comprise any suitable conducting material, such as aluminum (Al), copper (Cu), or the like. In some embodiments, the outer conductor212may comprise Al. The outer conductor212may extend away from a conductive plate214disposed above the base200. The outer conductor212may be coupled to an electrical ground, such as by having an opposing end of the outer conductor212coupled to a case400which contains the one or more mechanisms148as shown inFIG. 4and described below. Alternatively, the outer conductor212may be separately grounded (not shown).

An outer dielectric layer216may be disposed between the inner and outer conductors210,212to electrically isolate the outer conductor212from the inner conductor210. The outer dielectric layer216may comprise any suitable dielectric material, such as a polytetrafluoroethylene (PTFE)-containing material, such as TEFLON® (available from DuPont of Wilmington, Del.), or the like. In some embodiments, the outer dielectric layer216may comprise PTFE. In operation, electrical energy, such as RF energy, may flow through the inner conductor210to the first electrode206. An electric field may typically exist between the inner conductor210and any other conductive element proximate the inner conductor210. Further, a magnetic field may be induced by the electrical current flowing through the inner conductor210. The outer conductor212may act to confine the electric and magnetic fields to the region between the inner and outer conductor210,212, e.g., to the region which includes the outer dielectric layer216. The confinement of the electric and magnetic fields to this region may result in improved uniformity in the distribution of the electric and magnetic fields, which can result in improved etch rate and etch dimension uniformity on the substrate114disposed atop the substrate support116. Further the conductive plate214may similarly act to confine the electric and magnetic fields and/or symmetrically distribute the electric and magnetic fields about the conductive plate214. Additionally, the conductive plate214may act as a shield to isolate the substrate214from asymmetric electric and magnetic fields caused by other components, such as a first conductor408illustrated inFIG. 4, described below.

The substrate support116may further include a dielectric layer218disposed between the first electrode206and the conductive plate214. The dielectric layer218may comprise a process compatible dielectric material, such as Rexolite®, a cross-linked polystyrene, available from C-Lec Plastics, Inc. of Philadelphia, Pa., or the like. The dielectric layer218may be utilized to limit power losses, for example, between the first electrode206and the conductive plate214.

In some embodiments, the substrate support116may include an electrostatic chuck (ESC)220disposed above the first electrode206. The ESC may generally comprise a base layer226having a dielectric layer248disposed over the base layer226. The base layer226may be a cooling plate to facilitate keeping the electrostatic chuck220at a desired temperature during operation. For example, the base layer226may comprise a highly heat conductive material, such as aluminum or copper, and may have one or more channels for flowing a heat transfer fluid through the channels.

The ESC220may include a second electrode222. In some embodiments the second electrode222may be disposed within the dielectric layer248. The second electrode222may be coupled to a source of DC energy to electrostatically secure the substrate114to the substrate support116via a second conductor236. In some embodiments, the second conductor236may be disposed along the axis208and within the axial opening of the inner conductor210in order to minimize any RF interference from the DC energy being provided and to make any such RF interference symmetrical. In some embodiments, the second conductor236may be a conductive rod. The second conductor236may be fabricated from any suitable process-compatible conductive material. In some embodiments, the second conductor236comprises copper.

In some embodiments, the ESC220may further include one or more heater electrodes238. In some embodiments the one or more heater electrodes238may be disposed within the dielectric layer248. The one or more heater electrodes238may be provided in any suitable pattern and may be arranged in one or more heater zones to provide a desired heating pattern for heating the substrate. The one or more heater electrodes238may be coupled to a source of AC energy via a plurality of third conductors234. Application of AC energy to the one or more heater electrodes238causes the electrodes to heat up by resistive heating (i.e., Joule heating). In some embodiments, the third conductors234may be conductive rods. The third conductors234may be fabricated from any suitable process-compatible conductive material. In some embodiments, the third conductors234comprise copper.

In some embodiments, an electrical distribution plate240may be provided to route the connections from the plurality of third conductors234to the one or more heater electrodes238. For example, in some embodiments, the electrical distribution plate240may include a printed circuit board (PCB)242, or the like, for connecting to the plurality of third conductors234and for providing conductive paths (e.g., electrical traces) to a plurality of AC terminals224. An AC terminal insulator plate244may be disposed over the PCB242to insulate the conductive paths and the AC terminals224from adjacent conductive elements, such as the base layer226of the ESC220. Conductors246may be provided to couple the AC terminals224to respective ones of the plurality of third conductors234. In some embodiments, the conductors246may be conductive rods. In some embodiments, the conductors246may comprise copper.

In some embodiments, the third conductors234may be symmetrically disposed about the central axis208. In some embodiments, the third conductors234may be symmetrically disposed about the central axis208and may be disposed within the axial opening of the inner conductor210(as shown). In some embodiments, the AC terminals224may be symmetrically disposed about the central axis208, for example, having each AC terminal224in alignment with a respective one of the plurality of third conductors234. The inventors have found that the symmetrical arrangement of the third conductors234about the central axis208can further minimize RF interference and improve process performance, such as improving etch rate uniformity and/or etch dimension uniformity on a substrate.

In some embodiments, the second conductor236and the plurality of third conductors234may be routed through the open central portion of the inner conductor210. An inner dielectric layer228may be disposed within the inner conductor210and may have the second conductor236and the plurality of third conductors234routed through passages disposed through the inner dielectric layer228. The passages of the inner dielectric layer228may insulate the second conductor236and the plurality of third conductors234from each other, from the inner conductor210, and from other adjacent electrically conductive components or layers. The passages of the inner dielectric layer228may further position the second conductor236and the plurality of third conductors234in a desired location or pattern, such as a symmetric pattern. The inner dielectric layer228may comprise similar dielectric materials as discussed above for the outer dielectric layer216.

The inner dielectric layer228, as shown inFIG. 2and in top cross sectional view inFIG. 3, is generally disposed within the inner conductor210, but may extend beyond the end of the inner conductor210to surround at least a portion of the lengths of the second conductor236and the plurality of third conductors234that extend beyond the end of the inner conductor210. For example, the inner dielectric layer228may include a first portion230surrounding a portion of the plurality of third conductors234that extend past the end of the inner conductor210toward the electrical distribution plate242. A second portion232may surround a portion of the second conductor236that extends past the end of the inner conductor210toward the second electrode222.

FIG. 3illustrates a schematic partial top view of the symmetric electrical feed structure150in accordance with at least some embodiments of the present invention. As shown inFIG. 3, the symmetric electrical feed structure150includes the inner conductor210and the outer conductor212separated by the outer dielectric layer216. The inner dielectric layer228insulates and positions the second conductor236and the plurality of third conductors234in a desired pattern (e.g., symmetrically). For example, the second conductor236may be centrally disposed in the inner dielectric layer228along the central axis208and the plurality of third conductors234may be disposed symmetrically about the central axis208.

FIG. 4depicts a schematic side view of a lower portion of the symmetric electrical feed structure150showing the one or more mechanisms148coupled to the substrate support116in accordance with at least some embodiments of the present invention. As shown inFIG. 4, the lower portion of the symmetric electrical feed structure150may provide for the connection to a source of RF energy and optionally, one or more of AC or DC energy. For example, the inner conductor210may be coupled to an RF power source406, for example, via a first conductor408, to provide RF energy to the first electrode206via the first conductor408. In some embodiments, the second conductor236may be coupled to a DC power source402to provide DC energy to the second electrode222to electrostatically retain a substrate on the substrate support116. In some embodiments, the plurality of third conductors234may be coupled to an AC power supply404to provide AC energy to the electrodes238to provide heat to the substrate.

The first conductor408may be coupled to the inner conductor210about the outer surface of the inner conductor210to provide the RF energy symmetrically to the inner conductor210. The first conductor408may extend laterally from the central axis208toward the RF power source406, which may be disposed to the side of the central axis208. The RF power source406may be coupled to the first conductor408via a match network410. The RF power source406may provide RF energy at any suitable frequency and power for a particular application. In some embodiments, the RF power source406may be capable of providing up to about 1500 W of RF energy at a frequency of about 13.56 MHz. The RF power may be provided either in a continuous wave or pulsed mode.

In some embodiments, a second dielectric layer414may be provided to electrically isolate the first conductor408from adjacent electrically conductive components (such as a grounding case400, discussed below, that encloses the lower portion of the electrical feed structure150). In some embodiments, and as shown inFIG. 4, the first conductor408may be embedded within the second dielectric layer414.

Although the first conductor408is disposed at an angle to the inner conductor210, which may result in a disturbance in the electromagnetic field created by the RF current, the conductive plate214may function to limit the electromagnetic effect caused by the orientation of the first conductor408. As such, any asymmetries in the electric field that might be generated due to the orientation of the first conductor should have limited or no affect on processes being performed on a substrate disposed on the substrate support116.

In some embodiments, a dielectric end cap416may be provided about the end of the RF feed structure150. For example, the dielectric end cap416may be placed about a portion of the inner dielectric layer228that extends beyond the inner conductor210. In some embodiments, the dielectric end cap416may cover a portion of the inner dielectric layer228that extends beyond the second dielectric layer414. The dielectric end cap416may have a plurality of openings to allow the conductors of the electrical feed structure150to extend therethrough. The conductors may be respectively coupled to the DC power supply402and/or the AC power supply404by respective conductive paths coupled to the plurality of conductors234and the conductor236. For example, a printed circuit board (PCB)418may be provided having electrical traces formed therein or thereon to route the plurality of conductors234to the AC power supply404. A separate conductive path may be provided to couple the conductor236to the DC power supply402. In some embodiments, a terminal420(shown in dotted lines) may be provided to facilitate coupling of the conductor236to the DC power supply402. The terminal420may extend through the entire PCB418or just a portion of the PCB418. In some embodiments, the PCB418may comprise a base422, a substrate424supported by the base422, and a cover426. The cover426may cover the substrate424and retain the substrate424between the base422and the cover426. Openings may be provided in the cover426to facilitate making electrical connections to the conductors234,236, the terminal420, and/or any electrical traces in or on the substrate424or passing through the substrate424.

In some embodiments, a grounding case400may be provided to substantially enclose the lower portion of the symmetric electrical feed structure150, for example, in the region where RF energy is coupled to the inner conductor210. The grounding case400may include an opening401through which one or more components of the symmetric electrical feed structure150, such as the outer dielectric layer216, inner conductor210, inner dielectric layer228, second conductor236, and plurality of third conductors234, may be disposed. In some embodiments, and as shown inFIG. 4, an end of the bellows152and an end of the outer conductor212may be coupled to the grounding case400proximate the opening401. In some embodiments, the grounding case400may provide the electrical ground for the outer conductor212.

The grounding case400may also have an opening403to facilitate routing the second conductor236and the plurality of third conductors234to the respective DC and AC power sources. The inner dielectric layer228and/or the dielectric and416may electrically isolate the second and third conductors234,236from the grounding case400, as shown. In some embodiments, additional conductors may be provided to respectively couple the second conductor236and the plurality of third conductors234to the DC power source402and the AC power source404.

Returning toFIG. 1, the controller140comprises a central processing unit (CPU)144, a memory142, and support circuits146for the CPU144and facilitates control of the components of the chamber110. To facilitate control of the process chamber110as described above, the controller140may be one of any form of general-purpose computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory142, or computer-readable medium, of the CPU144may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The support circuits146are coupled to the CPU144for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. The methods, such as etch process recipes or the like used to process the substrate114may be generally stored in the memory142as a software routine. The software routine may also be stored and/or executed by a second CPU (not shown) that is remotely located from the hardware being controlled by the CPU144.

In operation, the substrate114is placed on the substrate support116and process gases are supplied from a gas panel138through entry ports126and form a gaseous mixture. The gaseous mixture is ignited into a plasma155in the chamber110by applying power from the plasma source118and RF power source406to the inductive coil element312and the first electrode206, respectively. The pressure within the interior of the chamber110is controlled using a throttle valve127and a vacuum pump136. Typically, the chamber wall130is coupled to an electrical ground134. The temperature of the wall130is controlled using liquid-containing conduits (not shown) that run through the wall130.

The temperature of the substrate114may be controlled by stabilizing a temperature of the substrate support116. In one embodiment (not shown), helium gas from a gas source may be provided via a gas conduit to channels (not shown) formed in the surface of the substrate support116under the substrate114. The helium gas may be used to facilitate heat transfer between the substrate support116and the substrate114. During processing, the substrate support116may be heated by a resistive heater, such as the plurality of AC terminals224discussed above, to a steady state temperature and then the helium gas facilitates uniform heating of the substrate114. Using such thermal control, the substrate114may be maintained at a temperature of about 0 to about 150 degrees Celsius.

Although described with respect to an inductively coupled plasma etch chamber, other etch chambers may be used to practice the invention, including chambers with remote plasma sources, electron cyclotron resonance (ECR) plasma chambers, and the like. In addition, other non-etch chambers that provide RF energy to an electrode disposed in a substrate support may also be modified in accordance with the teachings provided herein.

Thus, apparatus for processing a substrate has been disclosed herein. At least some embodiments of the inventive apparatus may include a symmetric electrical feed structure that may advantageously improve substrate processing, such as etch rate and/or etch dimension uniformities. The inventive symmetric electrical feed structure and substrate supports incorporating same may advantageously reduce electromagnetic skew along the surface of a substrate by conducting electrical power to the various components of the substrate support via one or more conductors that are symmetrically arranged with respect to a central axis of the substrate support and/or by providing one or more elements for confining or uniformly distributing an electric and/or magnetic field.