Dynamic ion radical sieve and ion radical aperture for an inductively coupled plasma (ICP) reactor

Embodiments described herein provide apparatus and methods of etching a substrate using an ion etch chamber having a movable aperture. The ion etch chamber has a chamber body enclosing a processing region, a substrate support disposed in the processing region and having a substrate receiving surface, a plasma source disposed at a wall of the chamber body facing the substrate receiving surface, an ion-radical shield disposed between the plasma source and the substrate receiving surface, and a movable aperture member between the ion-radical shield and the substrate receiving surface. The movable aperture member is actuated by a lift assembly comprising a lift ring and lift supports from the lift ring to the aperture member. The ion-radical shield is supported by shield supports disposed through the aperture member. The aperture size, shape, and/or central axis location may be changed using inserts.

FIELD

Embodiments described herein relate to semiconductor manufacturing methods and apparatus. More specifically, substrate etching methods and apparatus are disclosed.

BACKGROUND

Pattern etching is a staple of semiconductor manufacturing. A substrate is commonly exposed to a plasma of reactive ions and neutrals to etch a pattern into a surface of the substrate. Such processes are typically used to etch a pattern into a substrate that is subsequently used in photolithographic patterning of semiconductor substrates. The substrate is usually glass or quartz, with a layer of chromium and/or molybdenum-doped silicon nitride on one side. The layer is covered with an anti-reflective coating and a photosensitive resist, and patterned by exposure to patterned UV light. Exposed portions of the resist are dissolved, and the underlying chromium layer is patterned by plasma etching.

During plasma etching, a plasma is generally formed adjacent the substrate. Reactive ions and radicals from the plasma react with the substrate surface, removing material from the surface. The rate of material removal, or etching, at a location on the substrate surface is proportional to the density of reactive species adjacent to that location. Due to microloading, variation in aspect ratio, plasma effects, and chamber effects, uniformity of the density of reactive species across the surface of a substrate often varies, resulting in variation of etch rate across the substrate. In many cases, etch rate is observed to be higher near the center of a substrate and lower near the periphery.

Prior methods of addressing etch rate uniformity include chemical methods of etch rate control, thermal methods of controlling precursor temperature and thermal profile of the plasma, and electromagnetic methods featuring electrodes placed at different locations within the chamber. There remains, however, a need for methods and apparatus that influence the density profile of a plasma in a dynamic, adjustable way.

SUMMARY

Embodiments described herein provide apparatus and methods of etching a substrate using an ion etch chamber having a movable aperture. The ion etch chamber has a chamber body enclosing a processing region, a substrate support disposed in the processing region and having a substrate receiving surface, a plasma source disposed at a wall of the chamber body facing the substrate receiving surface, an ion-radical shield disposed between the plasma source and the substrate receiving surface, and a movable aperture member between the ion-radical shield and the substrate receiving surface. The movable aperture member is actuated by a lift assembly comprising a lift ring and lift supports from the lift ring to the aperture member. The ion-radical shield is supported by shield supports disposed through the aperture member. The aperture size, shape, and/or central axis location may be changed using inserts.

The lift ring may be actuated by a linear actuator to move the aperture member closer to or further from a substrate disposed on the substrate support. A method described herein of processing a substrate includes disposing an aperture member between an ion-radical shield and a substrate receiving surface of an ion etching chamber and controlling a density profile of reactive species near the substrate receiving surface by moving the aperture member closer to or further from the substrate receiving surface.

In another embodiment, the lift ring may be coupled to the ion-radical shield to move the ion-radical shield closer to or further from the aperture member, while the aperture member is supported from a fixed member.

DETAILED DESCRIPTION

Embodiments described herein provide a method and apparatus for etching a substrate using a movable aperture member.FIG. 1is a schematic sectional side view of a processing chamber100according to one embodiment. Suitable processing chambers that may be adapted for use with the teachings disclosed herein include, for example, the Decoupled Plasma Source (DPS®) II reactor, or the Tetra™ family of substrate etch systems, all of which are available from Applied Materials, Inc. of Santa Clara, Calif. The particular embodiment of the processing chamber100shown herein is provided for illustrative purposes and should not be used to limit the scope of the invention. It is contemplated that the invention may be utilized in other plasma processing chambers, including those from other manufacturers.

The processing chamber100generally includes a processing volume106defined by chamber walls102and a chamber lid104. The processing chamber100includes a plasma source122for supplying or generating a plasma in the processing volume106. The plasma source122may include an antenna110disposed above the chamber lid104for generating an inductively coupled plasma in the processing volume106. The antenna110may include one or more co-axial coils110a,110b. The antenna110may be coupled to a plasma power source112via a matching network114.

A supporting assembly108is disposed within the processing volume106for supporting the substrate101being processed on a raised portion130. The raised portion130may function as a stage for positioning the substrate101at a desired location within the processing volume106. A top surface182of the raised portion130functions as a substrate receiving surface. The supporting assembly108may include an electrostatic chuck116, which has at least one clamping electrode118connected to a chuck power supply126by an electrical connection128. The supporting assembly108may include other substrate retention mechanisms such as a susceptor clamp ring, a mechanical chuck, a vacuum chuck, and the like. The supporting assembly108may include a resistive heater124coupled to a heater power supply120and a heat sink129for temperature control.

The chuck power supply126may be an RF generator in some embodiments, so an impedance match circuit127may be interposed between the chuck power supply126and the clamping electrode118. The bias power from the chuck power supply126or the source power from the plasma power source112, or both, may be pulsed or continuous. The chuck power supply126and/or the plasma power source112may be operable to provide pulsed RF power at a frequency between about 1 kHz and about 10 kHz, a duty cycle between about 10% and about 90%, with a minimum pulse duration of about 10 μsec. The match circuit114and/or the match circuit127may be operable to provide a stable plasma at load of about 50Ω.

The supporting assembly108also includes an adaptor134for transferring the substrate101between the raised portion130and an exterior transfer device, such as an exterior robot. The adaptor134is disposed over the electrostatic chuck116and may have an opening136allowing the raised portion130to extend therethrough. The adaptor134may be lifted from the electrostatic chuck116by a plurality of lift pins140coupled to a lift mechanism138. Exemplary adaptors are described in U.S. Pat. No. 7,128,806, entitled “Mask Etch Processing Apparatus”.

The processing chamber100may also include an ion-radical shield142disposed above the supporting assembly108. The ion-radical shield142may be electrically isolated from the chamber walls102and the supporting assembly108. The ion-radical shield142includes a substantially flat plate146having a plurality of through holes148and a plurality of shield supports150supporting the flat plate146and positioning the flat plate146at a certain distance above the supporting assembly108. The plurality of shield supports150may be disposed on the electrostatic chuck116, the adaptor134or a baffle156. The plurality of through holes148may be confined to an open area152of the flat plate146. The open area152controls the amount of ions that pass from a plasma formed in an upper volume154of the processing volume106to a lower volume144located between the ion-radical shield142and the supporting assembly108. The areal extent covered by the through holes148may be larger than an areal extent of the top surface182. Exemplary ion-radical shields may be found in U.S. Pat. No. 7,909,961, entitled “Method and Apparatus for Substrate Plasma Etching”.

A gas panel158is connected to inlets160for supplying one or more processing gases towards the processing volume106. A vacuum pump164is coupled to the processing volume106via a throttle valve162. The baffle156may be disposed around the supporting assembly108upstream to the throttle valve162to enable even flow distribution and compensate for conductance asymmetries in the processing volume106.

An aperture assembly166includes an aperture member168supported between the ion-radical shield142and the supporting assembly108on a plurality of lift supports170, which may be support pins, coupled to a lift ring172. The aperture member168separates the lower volume144from a processing zone145between the aperture member and the top surface182of the raised portion130. An actuator176, such as a linear actuator, for example a hydraulic cylinder, pneumatic cylinder or electrically driven screw actuator, coupled to the lift ring172through a shaft174, moves the aperture member168closer to, or further from, the supporting assembly108. Moving the aperture member168adjusts the distribution of reactive species near a substrate on the supporting assembly108.

An edge shield188may be coupled to the aperture member168. The edge shield188is generally an annular member that has an extension toward the supporting assembly108beyond the aperture member168. The extension of the edge shield188prevents process gases flowing around the aperture member168to the supporting assembly108and any substrate disposed thereon.

The aperture member168has an aperture178formed in a central region of the aperture member168through which process gases flow to contact the substrate101. The aperture is shown inFIG. 1as having a dimension larger than a corresponding dimension of the substrate101, but the dimension of the aperture may be smaller than, or about the same size as, the corresponding dimension of the substrate101in some embodiments. The dimension of the aperture and its proximity to the substrate influence the distribution of reactive species across the substrate surface. In some embodiments, the aperture member168may be a focus plate that focuses reactive species to a desired distribution at the top surface182of the raised portion130.

The lift ring172is disposed in the processing volume106radially outwards of the supporting assembly108. The lift ring172is mounted on the shaft174in a substantially horizontal orientation. The shaft174is driven by the actuator176to move the lift ring172vertically in the processing volume106. The three or more lift supports170are extending upward from the lift ring172and positioning the aperture member168above the supporting assembly108. The three or more lift supports170fixedly attach the aperture member168to the lift ring172. The aperture member168moves vertically with the lift ring172in the processing volume106so that the aperture member168can be positioned at a desired distance above the substrate101and/or an exterior substrate handling device can enter the processing volume106between the aperture member168and the supporting assembly108to transfer the substrate101.

The three or more lift supports170may be positioned to allow the substrate101to be transferred in and out the processing chamber100. In one embodiment, each of the three or more lift supports170may be positioned close to one of the plurality of shield supports150supporting the ion-radical shield to maximize access to the substrate101.

The aperture member168may be a planar plate in a size substantially similar to the inner dimension of the chamber wall102so that the aperture member168can block the downward flow of the processing gas or plasma in the processing volume106. In one embodiment, the chamber wall102is cylindrical and the aperture member168may be a disk having an outer diameter slightly smaller than an inner diameter of the chamber wall102. The aperture178is aligned with the raised portion130of the electrostatic chuck116, and may be positioned substantially parallel to the substrate101. The aperture178provides a restricted path for the processing gas, or active species, to flow downwards toward the raised portion130where the substrate101is positioned, thus, controlling the plasma-exposure of the substrate101.

The aperture178of the aperture member168has an edge179that may be contoured for supporting a second member, such as an insert, as described in more detail in connection withFIG. 5B. The cross-sectional shape of the contour may be one of beveled, curved, or stepped. The contour of the edge179faces the ion-radical shield142, such that a second member may be supported in the aperture178in substantially parallel relationship with the aperture member168. In an embodiment wherein the edge179has a bevel, the bevel may be a straight bevel machined at any angle up to about 75° referenced to the plane of the aperture member168. In other embodiments, the bevel may be curved or faceted, if desired. The edge179may be partially beveled in some embodiments, with a beveled portion and a straight portion. For example, a first portion of the edge179proximate a surface of the aperture member168facing the ion-radical shield142may be beveled while a second portion of the edge179proximate a surface of the aperture member168facing the top surface182of the raised portion130may be straight (i.e. substantially perpendicular to the top surface182). Such a partially beveled edge may improve stability of a sizing insert nested with the aperture member168.

The aperture178may be shaped substantially similar to the shape of the substrate101being processed. The aperture178may be slightly larger than a top surface of the substrate101to provide a suitable process window for affecting distribution of reactive species across the surface of the substrate101. For example, the aperture178may be larger than about 6×6 inches. A distance180between the aperture member168and the top surface182of the raised portion130can be adjusted to achieve desired plasma-exposure of the substrate101.

By operating the lift ring172, the aperture member168may be movably positioned below the ion-radical shield142and above the supporting assembly108. The aperture member168may have a plurality of openings184to accommodate the plurality of shield supports150that support the flat plate146of the ion-radical shield142. The openings184may be through holes, cutouts, notches, or other types of openings formed to allow the aperture member168to move freely without impacting the shield supports150.

During processing, a plasma is usually formed in the processing volume106. Species in the plasma, such as radicals and ions, pass through the flat plate146and the aperture178of the aperture member168to the substrate101. The aperture member168controls a distribution of the radicals and ions proximate the upper surface of the substrate101by creating a flow pathway for the radicals and ions from the lower volume144to the processing zone145. The aperture178may be shaped and/or positioned so that species passing through the aperture178do not reach the edge and/or sides of the substrate101. The aperture178may also be shaped, sized, and/or positioned to control a density of active species across the substrate101. In one embodiment, the density of active species near a central region of the substrate101may be reduced, and the density near a peripheral region of the substrate increased, by positioning the aperture member168closer to the ion-radical shield142than to the substrate101.

The aperture member168may be formed from materials that are compatible with the processing chemistry. In one embodiment, the aperture member168may be formed from quartz or ceramics, such as alumina, yttria (yttrium oxide), and K140 (a proprietary material available from Kyocera), among others, including combinations and alloys thereof. The aperture member168may be coated in some embodiments. A ceramic coated metal material may be useful, for example anodized aluminum or aluminum coated with a deposited or sprayed ceramic coating, such as alumina (Al2O3) or yttria (Y2O3).

The aperture member168may be electrically isolated from the chamber, or may be electrically energized to provide a bias voltage, if desired, or to remove buildup of voltage from exposure to plasma processing. An electrical connection181may be provided with a path to ground, such as the chamber wall102, to remove voltage buildup. A control element such as a switch, not shown, may be provided. A bias voltage may be applied to the aperture member168by coupling a power source to the electrical connection181. An RF source177is shown inFIG. 1, with a filter circuit183, which may also be or include an impedance match circuit. For biasing the aperture member168, the electrical connection181is generally coupled to a conductive portion of the aperture member168, such as a metal portion if the aperture member168is a ceramic coated metal member.

FIG. 2is a partial perspective view of the aperture assembly266according to one embodiment, with the chamber lid104, chamber walls102and supporting assembly108removed.

The plurality of lift supports170penetrate the baffle156to position the aperture member168between the baffle156and the flat plate146. The plurality of through holes184accommodate the shield supports150supporting the flat plate146on the baffle156. The staggered arrangement of shield supports150and lift supports170allows the aperture member168to move independently from the baffle156and the flat plate146.

The aperture member168is moved vertically by the lift ring172. The lift ring172may include a ring shaped body204having a side extension202. The ring shaped body204has an inner opening206large enough to surround the supporting assembly108(FIG. 1). The side extension202is located radially outwards from the ring shaped body204. The side extension202allows the lift loop172to connect with an actuator from the side. The side driven arrangement enables the lift ring172and the aperture member168to have a separate driven mechanism from the baffle156and the flat plate146of the ion-radical shield142, thus, improving the process flexibility of the processing chamber100.

The aperture member168may be positioned at different distances above the supporting assembly108(FIG. 1) to control distribution of active species across the surface of the substrate101and/or enable movements of the substrate101and other chamber components.

FIG. 3Ais a sectional side view showing the aperture member168in a lower processing position. A lower surface306is positioned at a distance302above the raised portion130of the supporting assembly108. At the lower processing position, the distance302is less than about 1.0 inches, such as between about 0.4 inches and about 0.6 inches, for example about 0.42 inches, placing the aperture member168close to the substrate101being processed. At the lower processing position, the aperture member168constrains radicals and ions flowing through the aperture178from spreading laterally, resulting in a relatively uniform density of active species across the substrate101.

FIG. 3Bis a sectional side view showing the aperture member168in an upper processing position. The lower surface306is positioned at a distance304above the raised portion130of the supporting assembly108. At the upper processing position, the aperture member168allows radicals and ions flowing through the aperture178to spread laterally before contacting the substrate101. As the radicals and ions spread laterally, density of active species near a peripheral portion of the substrate101becomes lower than density of active species near a central portion of the substrate101. Thus, adjusting a distance between the aperture member168and the substrate101may control the density distribution of active species near the substrate101. At the upper processing position, the distance302may be at least about 1.5 inches, such as between about 1.6 inches and about 2.2 inches, for example about 2.1 inches.

FIG. 3Cis a sectional side view showing the aperture member168in a transferring position so that the substrate101can be transferred to and from the supporting assembly108. The lift ring172and the aperture member168are raised to create space between the aperture member168and the raised portion130for substrate transferring.

Additionally, the distance between the aperture member168and the raised portion130may be dynamically adjusted during processing or between processing of successive substrates to achieve optimal reactive species uniformity for each substrate. When the distance between the aperture member168and the raised portion130is maximized, the difference between center etch rate and peripheral etch rate will be maximized, and when the distance is minimized, the etch rate difference will be minimized. This feature may be used to compensate for pattern effects on etch rate uniformity.

FIG. 4Ais a top view of the aperture member168.FIG. 4Bis a sectional side view of the aperture member168. The aperture member168has a planar disk shaped body402. The planar disk shaped body402may be circular for using in a processing chamber having cylindrical sidewalls. The aperture178is formed through a central area of the planar disk shaped body402. The aperture178may be squared for processing a squared substrate101. The aperture is generally shaped to follow the shape of substrates to be processed in the plasma chamber. The aperture178is defined by inner walls404, which in the embodiments described herein are beveled, but may be substantially vertical in other embodiments. In one embodiment, the size of the aperture178may be slightly larger than the size of the substrate101, such that the substrate101is visible through the aperture178inFIG. 4A. For example, the aperture178may be slightly greater than 6×6 inches in size. During processing, the aperture178is configured to be coaxially aligned with the substrate101to provide uniform processing of the substrate101. It should be noted that the aperture178may be offset from a central axis of the substrate101, if desired, to achieve a density profile that is not symmetric about a center of the substrate101.

In one embodiment, three or more through holes184are formed along the periphery of the planar disk shaped body402. The through holes184are configured to accommodate shield supports150for the ion-radical shield142. Supporting features, such as lift supports170, may be attached to the planar disk shaped body402at locations406. Alternately, the locations406may be recesses adapted to receive support members such as the lift supports170. The locations406may be positioned close to the through holes184so that the substrate101may be transferred through the space between neighboring lift supports170.

It should be noted that the aperture member168and the aperture178may have different shapes depending on the shape of the chamber and the shape of the substrate respectively.

Referring toFIG. 4B, one or more ring-shaped inserts408may be used with the aperture member168. The insert408has an outer dimension slightly larger than the dimension of the aperture178and an outer edge contoured to match the contoured wall179of the aperture178such that the insert408cannot pass through the aperture178when the insert408and the aperture member168are in a parallel mating orientation. The insert408rests on the contoured edge179of the aperture178, reducing the size of the aperture178and potentially changing the shape and/or the central axis location of the aperture178.

Various inserts408may have apertures of different size, and multiple inserts408may be used, if desired, to vary the aperture size, shape, and/or central axis location. For example, a first insert may have a first aperture that is between about ⅛″ and about ¼″ smaller in dimension that the aperture178of the aperture member168. A second insert may have a second aperture that is between about ⅛″ and about ¼″ smaller than the first aperture, and may nest within the first aperture. Up to about five inserts may be nested within the aperture168of the aperture member178to reduce the aperture size by up to about 3″, if desired. Varying the open area of the aperture using one or more inserts adds a method of control that may be used to adjust performance of the aperture member168for different substrates and chambers without having to take the chamber out of service to change major chamber components.

FIG. 5is a schematic sectional side view of a processing chamber500according to another embodiment. The embodiment ofFIG. 5is generally similar to the embodiment ofFIG. 1, but the aperture member568ofFIG. 5has an aperture578that is smaller than the substrate101, and the lift supports170and shield supports184ofFIG. 1are swapped inFIG. 5for lift supports570and aperture support584. The lift supports570couple the ion-radical shield146to the lift ring172, while the aperture supports584support the aperture member568from the adaptor134. In the embodiment ofFIG. 5, the ion-radical shield146may be moved closer to or further from the substrate101, while the aperture member568remains stationary with respect to the substrate101.

The embodiment ofFIG. 5incorporates another method of controlling the distribution of reactive species across the surface of the substrate101. As the ion-radical shield142is moved with respect to the aperture member568, the density profile of reactive species passing through the aperture578changes, resulting in a changing density profile at the substrate101. It should be noted that embodiments are contemplated in which both the aperture member568and the ion-radical shield146are actuated.