Gas flow diffuser

A method and apparatus for providing flow into a processing chamber are provided. In one embodiment, a vacuum processing chamber is provided that includes a chamber body having an interior volume, a substrate support disposed in the interior volume and a gas distribution assembly having an asymmetrical distribution of gas injection ports. In another embodiment, a method for vacuum processing a substrate is provided that includes disposing a substrate on a substrate support within in a processing chamber, flowing process gas into laterally into a space defined above a gas distribution plate positioned in the processing chamber over the substrate, and processing the substrate in the presence of the processing gas.

BACKGROUND

1. Field of the Invention

Embodiments of the present invention relate to a semiconductor substrate processing system. More particularly, embodiments of the invention relate to a gas flow diffuser for controlling the flow of gases within a semiconductor substrate processing chamber.

2. Background of the Related Art

Integrated circuits have evolved into complex devices that can include millions of components (e.g., transistors, capacitors, resistors, and the like) on a single chip. The evolution of chip designs continually requires faster circuitry and greater circuit density. The demands for greater circuit density necessitate a reduction in the dimensions of the integrated circuit components. The minimal dimensions of features of such devices are commonly referred to in the art as critical dimensions. The critical dimensions generally include the minimal widths of the features, such as lines, columns, openings, spaces between the lines, and the like.

As these critical dimensions shrink, process uniformity across the substrate becomes paramount to maintain high yields. One problem associated with a conventional plasma etch process used in the manufacture of integrated circuits is the non-uniformity of the etch rate across the substrate, which may be due, in part, to a lateral offset between the reactive species and the substrate being etched. One factor contributing to the tendency of the reactive species to be offset from the center of the substrate is the radial location of the chamber exhaust port. As gases are more easily pumped from areas of the chamber that are closest to the exhaust port, the reactive species are pulled toward the exhaust port, thereby becoming offset with respect to the center of the chamber and the substrate positioned therein. This offset contributes to a loss of etch uniformity over the surface of the substrate which may significantly affect performance and increase the cost of fabricating integrated circuits.

A flow restricting device may be positioned within the chamber to change the chambers conductance in order to compensate for the offset of the pumping port. Although this technique has demonstrated good processing results, a level of process uniformity has not been achieved that will enable next generation devices, believed at least in part to be due to the inability to completely compensate for conductance non-uniformity above the substrate being processed within the processing chamber. Thus, as linewidths and critical dimensions continue to shrink, the need remains for a continued improvement in process uniformity in order to enable fabrication of next generation devices at a practical cost of manufacture.

Therefore, there is a need in the art for an improved apparatus for etching material layers during the manufacture of integrated circuits.

SUMMARY

A method and apparatus for providing flow into a processing chamber are provided. In one embodiment, a vacuum processing chamber is provided that includes a chamber body having an interior volume, a substrate support disposed in the interior volume and a pumping port disposed below a plane of a substrate supporting surface of the substrate support. The pumping port location and geometry of the interior volume have a configuration that produces an asymmetrical processing result on a substrate disposed on the substrate supporting surface of the substrate support. The processing chamber also includes a gas distribution assembly positioned above the plane of the substrate supporting surface of the substrate support, wherein a configuration of the gas distribution assembly is selected to tune the processing results so as to provide a symmetry of the processing results caused by the location of the pumping port and geometry of the interior volume.

In another embodiment, a vacuum processing chamber is provided that includes a chamber body having an interior volume, a substrate support disposed in the interior volume and a gas distribution assembly having an asymmetrical distribution of gas injection ports.

In yet another embodiment, a vacuum processing chamber is provided that includes a chamber body having sidewalls and a lid defining an interior volume, a substrate support disposed in the interior volume and a gas distribution assembly. The gas distribution assembly includes a gas distribution plate coupled to the lid and at least one ring positioned between the gas distribution plate and the lid, the ring having an asymmetrical distribution of gas injection ports.

In still yet another embodiment, a method for vacuum processing a substrate is provided that includes disposing a substrate on a substrate support within in a processing chamber, flowing process gas into laterally into a space defined above a gas distribution plate positioned in the processing chamber over the substrate, and processing the substrate in the presence of the processing gas.

In a further embodiment, a gas distribution assembly is provide that includes a gas distribution plate having a plurality of apertures formed through the plate, the apertures having an orientation substantially parallel to a centerline of the plate, and at least one ring coupled to the gas distribution plate, the ring having a plurality of gas injection ports having an orientation different than the orientation of the apertures of the plate.

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. It is also contemplated that features of one embodiment may be beneficially utilized in other embodiments without further recitation.

DETAILED DESCRIPTION

Embodiments of the present invention generally relate to an apparatus for improving process uniformity across a semiconductor substrate in a plasma processing chamber. Those skilled in the art will understand that other forms of plasma etch chambers may be used to practice the invention, including reactive ion etch (RIE) chambers, electron cyclotron resonance (ECR) chambers, and the like. Furthermore, embodiments of the present invention may be useful in any processing chamber where flow control may improve process uniformity across the surface of a substrate during processing, such as atomic layer deposition (ALD) chambers, chemical vapor deposition (CVD) chambers, plasma enhanced chemical vapor deposition (PECVD) chambers, magnetically enhanced plasma processing chambers, and the like.

FIG. 1depicts a schematic, cross-sectional diagram of vacuum processing chamber102having a gas diffuser132in accordance to an embodiment of the present invention. In the embodiment illustrated inFIG. 1, the gas diffuser132tunes process uniformity, enabling compensation for conductance or other chamber attributes that cause asymmetrical processing (e.g., processing results that are not symmetrically relative to a centerline of the substrate). In another embodiment, the gas diffuser132may be used to create an asymmetrical processing result. One example of a processing chamber in which the invention may be beneficially utilized is an ENABLER™ processing chamber available from Applied Materials, Inc., of Santa Clara, Calif. It is also contemplated that the invention may be used to advantage in other processing chambers, including those from other manufacturers.

In one embodiment, a processing chamber102comprises a vacuum chamber body110having a conductive chamber wall130and bottom108. The chamber wall130is connected to an electrical ground134. A lid170is disposed on the chamber wall130to enclose an interior volume178defined within the chamber body110. At least one solenoid segment112is positioned exterior to the chamber wall130. The solenoid segment(s)112may be selectively energized by a DC power source154that is capable of producing at least 5V to provide a control knob for plasma processes formed within the processing chamber102.

A ceramic liner131is disposed within the interior volume178to facilitate cleaning of the chamber102. The byproducts and residue of the etch process may be readily removed from the liner131at selected intervals.

A substrate support pedestal116is disposed on the bottom108of the process chamber102below the gas diffuser132. A process region180is defined within the interior volume178between the substrate support pedestal116and the diffuser132. The substrate support pedestal116may include an electrostatic chuck126for retaining a substrate114on a surface140of the pedestal116beneath the gas diffuser132during processing. The electrostatic chuck126is controlled by a DC power supply120.

The support pedestal116may be coupled to an RF bias source122through a matching network124. The bias source122is generally capable of producing an RF signal having a tunable frequency of 50 kHz to 13.56 MHz and a power of between 0 and 5000 Watts. Optionally, the bias source122may be a DC or pulsed DC source.

The support pedestal116may also include inner and outer temperature regulating zones174,176. Each174,176may include at least one temperature regulating device, such as a resistive heater or a conduit for circulating coolant, so that the radial temperature gradient of the substrate disposed on the pedestal may be controlled. An example of one suitable pedestal with inner and outer temperature regulating zones is described in U.S. patent application Ser. Nos. 10/960,874 and 11/531,474, which are incorporated by reference in their entireties.

The interior of the chamber102is a high vacuum vessel that is coupled to a vacuum pump136through an exhaust port135formed through the chamber wall130and/or chamber bottom108. A throttle valve127disposed in the exhaust port135is used in conjunction with the vacuum pump136to control the pressure inside the processing chamber102. The position of the exhaust port135and other flow restrictions within the interior volume178of the chamber body110greatly influence the conductance and gas flow distribution within the processing chamber102.

The gas diffuser132provides a conduit through which at least one process gas is introduced into the processing region180in an asymmetrical manner that may be utilized to tune the conductance and gas flow distribution described above that are caused by the other chamber components (e.g., location of the exhaust port, geometry of the substrate support pedestal or other chamber component) so that the flow of gases and species are delivered to the substrate in a uniform, or selected, distribution. The gas diffuser132is used to control or tune various processing parameters in the chamber to provide symmetry of processing results. The gas diffuser132may alternatively be used to control or tune various processing parameters in the chamber to create asymmetry of processing results. Moreover, the gas diffuser132may be utilized to position the plasma relative to the centerline of the substrate114(which is concentrically disposed on the pedestal116). Moreover, the configuration of the gas diffuser132may be selected to improve process uniformity, or alternatively, create a predefined offset in processing results. For example, the configuration of the gas diffuser132may be selected to direct the flow of gas entering the process region180above the substrate support pedestal116in a manner that compensates for the chamber conductance. This may be accomplished by configuring the gas diffuser132to deliver gas into the process chamber with an asymmetry that offsets the asymmetric effects of the chamber conductance on plasma location and/or the delivery of ions and/or reactive species to the surface of the substrate during processing.

In an embodiment such as the one depicted inFIG. 1, the gas diffuser132includes at least two gas distributors160,162, a mounting plate128and a gas distribution plate164. The gas distributors160,162are coupled to one or more gas panels138through the lid170of the processing chamber102. The flow of gas through the gas distributors160,162may be independently controlled. Although the gas distributors160,162are shown coupled to a single gas panel138, it is contemplated that the gas distributors160,162may be coupled to one or more shared and/or separate gas sources. Gases provided from the gas panel138are delivered into a region172defined between the plates128,164, then exit through a plurality of holes168formed through the gas distribution plate164into the processing region180.

The mounting plate128is coupled to the lid170opposite the support pedestal116. The mounting plate128is fabricated from or covered by an RF conductive material. The mounting plate128is coupled to an RF source118through an impedance transformer119(e.g., a quarter wavelength matching stub). The source118is generally capable of producing an RF signal having a tunable frequency of about 162 MHz and a power between about 0 and 2000 Watts. The mounting plate128and/or gas distribution plate164is powered by the RF source118to maintain a plasma formed from the process gas present in the process region180of the processing chamber102.

The gas distributors160,162are coupled to at least one of the mounting or gas distribution plates128,164. In one embodiment, the gas distributor160may be positioned radially inward of the gas distributor162. The gas distributors160,162may be concentrically oriented relative to each other, both concentrically oriented relative to the centerline of the pedestal116, both non-concentrically oriented relative to the centerline of the pedestal116, one concentrically oriented and one non-concentrically oriented relative to the centerline of the pedestal116, or other suitable configuration. In the embodiment depicted inFIG. 1, the gas distributors160,162are, but not limited to, concentric rings.

The asymmetry of the gas flow exiting the diffuser132into the processing region180may be created by the non-concentricity of the gas distributors160,162to each other and/or the centerline of the pedestal116. The asymmetry of the gas flow exiting the diffuser132into the processing region180may also or alternatively be created by a radial non-uniformity of gases flowing out of at least one of the gas distributors160,162as further discussed below.

FIG. 2depicts a bottom cut-away view of one embodiment of the gas diffuser132depicted inFIG. 1. The gas distribution plate164is cut-away to shown an exemplary concentric orientation of the gas distributors160,162. In the embodiment depicted inFIG. 2, the gas distributors160,162are shown as concentric rings. The gas distributors160,162may alternatively have a variety of other orientations, for example at least one gas distributor702may have an oval or ellipsoidal shape, as shown inFIG. 7A. In another example, at least one gas distributor712may be non-concentric with the outer gas distributor162, as shown inFIG. 7B. Although the outer gas distributor is shown above as a circular ring, it may alternatively have any of the configurations described above, either with a circular inner gas distributor or with a non-circular inner gas distributor. It is also contemplated that none, one or all of the gas distributors may be concentrically oriented relative to the centerline the mounting plate128. The mounting plate128is generally coaxially aligned with the centerline of the pedestal116, and consequently, the substrate positioned thereon.

Returning toFIG. 2, the gas distributors160,162may be secured to at least one of the plates128,164. In one embodiment, the gas distributors160,162are secured to the mounting plate128by a plurality of brackets202or by other suitable manner. Alternatively, the gas distributors160,162may be compressed between the plates128,164.

FIG. 3depicts a sectional view of one embodiment of the bracket202securing the outer gas distributor162to the mounting plate132. The inner gas distributor160is similarly retained. The bracket202includes a tab302and a finger308. A fastener304extends through a hole in the tab302and is engaged with a threaded hole306formed in the mounting plate128. The finger308may be curved or otherwise formed to retain the gas distributor162proximate the plate132upon installation of the fastener304. It is contemplated that the gas distributors may be held in position utilizing other techniques.

FIG. 4Adepicts a sectional view of a coupling400of the outer gas distributor162utilized to connect the outer gas distributor162to the gas panel138. The inner gas distributor160includes a similar coupling402, as shown inFIG. 2. Although the couplings400,402are shown offset 180 degrees in the embodiment depicted inFIG. 2, the orientation of the couplings400,402may be arranged in any convenient manner.

Returning primarily toFIG. 4A, the coupling400includes a body408and a stem404. The stem404extends through a hole412formed in the mounting plate128. In one embodiment, the stem404includes a male threaded portion410which enables a panel nut414or other fastener to secure the coupling400to the mounting plate128. The stem404also includes a threaded port406which enables connection of the coupling400to a gas delivery line (not shown) routed from the gas panel138. It is contemplated that the coupling may have other configurations suitable for easy attachment to the gas panel and/or mounting plate.

The body408includes a mounting flange420. The mounting flange420has a o-ring gland422that accommodates a seal (not shown) which is compressed upon tightening of the panel nut414to prevent leakage through the hole412.

The body408includes a passage430that couples the port406to a cross hole432. The cross hole432has a counterbore that accepts an open end440of the gas distributor162. The open end440of the gas distributor162may be sealed to body408by any suitable method, for example, by adhesive, brazing, welding, pressfit, swaging or by a suitable gas-tight fitting. A second counterbore accepts a closed end442of the gas distributor162such that gases flowing into the coupling400through the port406the open end440of the gas distributor162and flow to the closed end442. The gases exit the gas distributor162through a plurality of asymmetrically distributed ports, as discussed further below with reference toFIG. 5.

FIG. 4Bdepicts a sectional view of an alternative embodiment of a coupling450. The coupling450is substantially similar to the coupling400described above, except for a crosshole452that extends through the body408to allow two open ends440of the gas distributor462to receive gas flowing through the passage430from the port406.

FIG. 5is a sectional view of the gas distributor162taken along section line5-5ofFIG. 2. The gas distributor162may be similarly configured. The gas distributor162includes a plurality of holes that allow gases into the region172. In one embodiment, inner and outer gas injection ports502,504are formed through the gas distributor162. The gas injection ports502,504may have any angular orientation in both the vertical and horizontal planes selected to produce a desired flow and/or pressure distribution within the gas diffuser132. In the embodiment depicted inFIG. 5, the inner and outer gas injection ports502,504are arranged concentrically, and have a centerline parallel to the plane of the gas distribution plate164.

The diameters of the gas injection ports502,504may be different or equal. For example, the diameter of the radially inner facing gas injection port504may be larger than the diameter of the radially outer facing gas injection port502to provide more gas to the inner regions of the gas diffuser132. Alternatively, the diameter of the radially outer facing gas injection port502may be larger than the diameter of the radially inner facing gas injection port504to provide more gas to the outer regions of the gas diffuser132.

Additionally, the density and/or distribution of the radially inner facing holes502along the gas distributor162may vary. For example, the number of the radially inner facing holes504may be greater per unit length of the distributor162in one region relative to another. In the embodiment depicted inFIG. 2, the number and/or open area of radially inner facing holes504increases per unit length along the gas distributor162further from the coupling400as measured from the open end440. This arrangement may be utilized to allow more gas to be delivered near the coupling400(or other selected region), or to compensate for pressure drop along the length of the distributor so holes504near the closed end442receive a greater amount of gas as compared to a distributor with a symmetrical distribution of holes.

It is contemplated that the density, open area and/or distribution of the radially outer facing holes504may be the same as, or different from, that of the radially inner facing holes502. It is also contemplated that the relative diameters of individual gas injection ports502,504may be selected to deliver more gas near the coupling400(or other selected region), or to compensate for pressure drop along the length of the distributor so gas injection ports502,504near the closed end (or other selected region) receive a greater amount of gas as compared to a distributor with a symmetrical distribution of holes.

The configuration of the inner gas distributor160may be similar to, or different from, the configuration of the outer gas distributor162. In the embodiment depicted inFIG. 2, the inner and outer gas distributors160,162are configured with increasing hole density and/or open area per unit length as measured from the open end of the distributors. Additionally in the embodiment depicted inFIG. 2, the location of the couplings400,402of the distributors160,162are arranged 180 degrees out of phase, along with the direction in that the distributor extends from the coupling toward the closed end. In an alternative embodiment, the inner and outer gas distributors160,162are configured with substantially uniform hole density between the open and closed ends, but have decreasing hole diameters from the open to closed end of the distributors160,162. It is also contemplated that the gas distributors160,162may be arranged in any combination of the above.

FIGS. 6A-Bdepicts sectional views of the how the places128,164of the diffuser132are coupled together and how the diffuser132is coupled to the lid assembly170. As depicted in the sectional view ofFIG. 6A, a fastener602is passed through a clearance hole in the distribution plate164and engaged with a threaded hole in the mounting plate132. As depicted in the sectional view ofFIG. 6B, a fastener612is passed through a clearance holes formed through the distribution and mounting plates164,132and engaged with a threaded hole in the lid assembly170. This mounting arrangement allows for the diffuser132to be readily removed from the lid assembly170, thereby facilitating exchange for a diffuser having a different flow configuration. Additionally, the plates164,132may be easily separated to allow one or more of the gas distributors160,162to be exchanged by removing and/or loosening the bracket202, thereby allowing quick reconfiguration of the diffuser132and adaptation for other process control attributes.

FIG. 8is a block diagram of one embodiment of an exemplary method800for selecting a configuration for the gas distributors160,162. The method800begins at box802by determining a process result due to chamber conductance utilizing a conventional gas diffuser (e.g., a diffuser with symmetric gas delivery). Process results900for an etch process obtained at box802are depicted inFIG. 9A, which illustrates both lateral and azimuthal non-uniformity. At box804, a configuration for the diffuser132is selected to an asymmetrical processing result, assuming the process was run in a chamber having a substantially uniform conductance. The configuration for the diffuser132selected at box804compensates for the non-uniformity of box802, such that a desired processing result are obtained at box806. Process results902obtained at box806are depicted inFIG. 9B, which illustrates substantial improvement for both the lateral and azimuthal etch results. The configuration of the diffuser132may be selected to center the processing results, as shown inFIG. 9B, or to minimize non-uniformity and control the lateral offset of processing results.

This process is particularly useful when changing process recipes. If one or more of flow rates, spacing, RF power, electrical or magnetic fields, substrate pedestal temperature gradients or other process parameter is changed which results in a shift in the conductance or plasma position within the chamber, the shift may be adjusted to provide a desired processing result by changing the configuration of the diffuser132. This may be accomplished by replacing the diffuser or one or more of the gas distributors within the diffuser. As such, timely and cost effective process tuning may be realized.