Patent Application
20100081284
1. Field
Embodiments of the present invention generally relate to semiconductor processing and, more particularly, to apparatus for processing substrates.
2. Description of the Related Art
Conventional process chambers that utilize a single pump to exhaust process gases from a side of the process chamber can lead to process non-uniformities (for example, non-uniform etch rates in an etch chamber) due, at least in part, to non-uniform flow of process gases in the process chamber. As the critical dimensions for semiconductor devices continue to shrink, process non-uniformities due to this effect are exacerbated by an increased need for more uniformly processed substrates.
Thus, there is a need in the art for an apparatus for processing substrates that can provide improved process uniformity.
Methods and apparatus for processing substrates are provided herein. In some embodiments, an apparatus for processing a substrate includes a flow equalizer configured to control the flow of gases between a process volume and an exhaust port of a process chamber. The flow equalizer includes at least one restrictor plate configured to be disposed in a plane proximate a surface of a substrate to be processed and defines an azimuthally non-uniform gap between an edge of the at least one restrictor plate and one of either a chamber wall or a substrate support when installed in the process chamber.
In some embodiments, an apparatus for processing a substrate includes a process chamber having a substrate support disposed in an inner volume thereof, the inner volume including a processing volume and a exhaust volume having an exhaust port disposed therein. A flow equalizer is disposed in the process chamber for controlling the flow of gases between the process volume and the exhaust port. The flow equalizer includes at least one restrictor plate disposed in a plane proximate the surface of a substrate to be processed and defining an azimuthally non-uniform gap between an edge of the at least one restrictor plate and one of either a chamber wall or the substrate support.
In some embodiments, a method for controlling flow in a process chamber includes providing a substrate to support surface of a substrate support disposed in an inner volume of a process chamber. The inner volume includes a processing volume and a exhaust volume having an exhaust port disposed therein. A gas is flowed into the processing volume. Flow non-uniformity over the substrate is reduced by flowing the gas from the processing volume to the exhaust volume past a flow equalizer disposed in the process chamber. The flow equalizer includes at least one restrictor plate disposed in a plane proximate a surface of the substrate and defines an azimuthally non-uniform gap between an edge of the at least one restrictor plate and one of either a chamber wall or the substrate support. Other and further embodiments and variations of the invention are described more fully below.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
Embodiments of the present invention generally relate to methods and apparatus for improving flow uniformity across a semiconductor substrate in a substrate processing chamber. The more uniform flow of process gases within the process chamber may advantageously facilitate more uniform flow of gases proximate the surface of a substrate, thereby facilitating more uniform processing of the substrate. The inventive apparatus may be utilized in any suitable process chamber having asymmetric pumping of exhaust. Suitable commercially available process chambers may include any of the DPS®, ENABLER®, ADVANTEDGE™, or other process chambers, available from Applied Materials, Inc. of Santa Clara, Calif.
Although described below with respect to a plasma etch reactor, other forms of plasma etch chambers may be modified in accordance with the teachings provided herein, including reactive ion etch (RIE) chambers, electron cyclotron resonance (ECR) chambers, and the like. Furthermore, 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.
The process chamber 102 has a chamber wall 103 defining an inner volume 105 that may include the processing volume 104 and the exhaust volume 106. The processing volume 104 may be defined, for example, between a substrate support 108 disposed within the process chamber 102 for supporting a substrate 110 thereupon during processing and one or more gas inlets, such as a showerhead 114 and/or nozzles provided at desired locations.
In some embodiments, the substrate support 108 may include a means for retaining the substrate 110 on the surface of the substrate support 108, such as an electrostatic chuck, a vacuum chuck, a substrate retaining clamp, or the like (not shown). In some embodiments, the substrate support 108 may include mechanisms for controlling the substrate temperature (such as heating and/or cooling devices, not shown) and/or for controlling the plasma flux proximate the substrate surface.
For example, in some embodiments, the substrate support 108 may include an RF bias electrode 140. The RF bias electrode 140 may be coupled to one or more bias power sources (one bias power source 138 shown) through one or more respective matching networks (matching network 136 shown). The one or more bias power sources may be capable of producing up to 12000 W at a frequency of about 2 MHz, or about 13.56 MHz, or about 60 MHz. In some embodiments, two bias power sources may be provided for coupling RF power through respective matching networks to the RF bias electrode 140 at a frequency of about 2 MHz and about 13.56 MHz. In some embodiments, three bias power sources may be provided for coupling RF power through respective matching networks to the RF bias electrode 140 at a frequency of about 2 MHz, about 13.56 MHz, and about 60 MHz. The at least one bias power source may provide either continuous or pulsed power. In some embodiments, the bias power source may be a DC or pulsed DC source.
In some embodiments, the position, or height, of the substrate support 108 within the process chamber 102 may be adjustable. For example, in some embodiments, a lift mechanism 134 may be coupled to the substrate support 108 to position the substrate support 108 in at least a lower position, for example, to facilitate the transfer of the substrate 110 into or out of the process chamber, such as through a slit valve (not shown), and an upper position, for example, to control the distance between the substrate 110 and the showerhead 114. The selection of the position of the substrate support 108 may alter the flow profile of a process gas on the substrate surface. Accordingly, in embodiments where the height of the substrate support 108 is changed, the ratio of the processing volume 104 to the exhaust volume 106 necessarily changes, which may result in a different flow profile across the substrate surface. In some embodiments, the flow equalizer 180 may be configured, for example, by design, to facilitate the uniform flow of process gases between the processing volume 104 and the exhaust volume 106 over the full range of heights accessible by the substrate support 108 (or a range of processing heights utilized during processing). For example, the flow equalizer 180 may be designed to provide an optimum flow uniformity over the aggregate range, and may not be optimized at a particular height accessible by the substrate support 108.
The one or more gas inlets (e.g., the showerhead 114) may be coupled to a gas supply 116 for providing one or more process gases into the processing volume 104 of the process chamber 102. Although a showerhead 114 is shown in
In some embodiments, the apparatus 100 may utilize inductively coupled RF power for processing. For example, the process chamber 102 may have a ceiling 142 made from a dielectric material and a dielectric showerhead 114. The ceiling 142 may be substantially flat, although other types of ceilings, such as dome-shaped ceilings or the like, may also be utilized. An antenna comprising at least one inductive coil element 144 is disposed above the ceiling 142 (two co-axial elements 144 are shown). The inductive coil elements 144 are coupled to one or more RF power sources (one RF power source 148 shown) through one or more respective matching networks (matching network 146 shown). The one or more plasma sources may be capable of producing up to 5000 W at a frequency of about 60 MHz and/or about 162 MHz. In some embodiments, two RF power sources may be coupled to the inductive coil elements 144 through respective matching networks for providing RF power at frequencies of about 2 MHz and about 13.56 MHz.
The exhaust volume 106 may be defined, for example, as the chamber volume beneath the plane of the surface of the substrate support 108. The exhaust volume 106 may be fluidly coupled to an exhaust system 120, wherein the exhaust system 120 includes a pumping plenum 124 and an exhaust port 122. The exhaust volume 106 may be fluidly coupled to the pumping plenum 124 via the exhaust port 122.
The flow equalizer 180 may be disposed proximate the surface of the substrate support 108 (e.g., at the interface between the processing volume 104 and the exhaust volume 106) to facilitate the uniform flow of process gases from the processing volume 104 to the exhaust volume 106. For example, the flow equalizer 180 forms an azimuthally non-uniform gap between the flow equalizer 180 and the substrate support 108 (e.g., a radially non-uniform gap). The azimuthally non-uniform gap may be smaller proximate the exhaust port 122 (the smaller gap labeled 190 in
The flow equalizer 180 provides a varied gap between the substrate support and chamber wall that is larger in areas that would otherwise have lower flow rates (e.g., further from the exhaust port 122) and smaller in areas that would otherwise have higher flow rates (e.g., closer to the exhaust port 122). The varying gap facilitates increasing the flow rate in areas that would otherwise be lower (by providing larger gap) while decreasing the flow rate in areas that would otherwise be higher (by providing smaller gap), thereby making the overall flow azimuthally (or radially) more uniform.
In the embodiments shown in
Alternatively, and as depicted in a partial side view in
Returning to
The flow equalizer 180 facilitates uniform flow of the exhaust gases from the inner volume 105 of the process chamber 102. For example, the flow equalizer 180 may provide reduced variance of flow resistance azimuthally (or symmetrically) about the substrate support 108 (e.g., substantially equal flow resistance). Accordingly, in some embodiments, the azimuthally non uniform gap may have a substantially equal conductance, flow rate, or flow resistance across all portions of the gap, include those proximate to (gap 190) and farther (gap 192) from the exhaust port 122. As used herein, the term substantially equivalent, or substantially equal, is understood to mean within about 10 percent of each other).
The flow equalizer may be a singular component or may include many parts that together define the shape, or profile, or the flow equalizer. Generally, the flow equalizer partially fills the space between the substrate support and the chamber wall at the level of the support surface of the substrate support (or the surface of s substrate disposed thereon). The flow equalizer may be disposed adjacent to either the chamber wall (or liner), or the substrate support, such that all exhaust flowing from the processing volume to the exhaust volume flows through a gap defined between the flow equalizer and one of the substrate support or the chamber wall (or liner). The gap is generally azimuthally non-uniform and larger in regions of low pressure (e.g., farther from the pump port) and smaller in regions of high pressure (e.g., nearer to the pump port). The size and shape of the gap is defined by the profile, or shape, or the flow equalizer (as the support pedestal and the chamber wall geometry are generally fixed). The flow equalizer may have a profile (e.g., a shape when viewed from above) that is ovular, elliptical, circular, wavy, discontinuous, continuous, or the like. In some embodiments the profile is ovular or elliptical.
Embodiments of a flow equalizer which may be utilized in the apparatus 100 are provided in
In some embodiments, the support ring 206 may be of varying thickness, and may be used to orient the angle of the at least one restrictor plate 208 with respect to the substrate support surface such that the at least one restrictor plate 208 is not parallel to a support surface of the substrate support, and, therefore, to the surface of a substrate being processed in the process chamber.
The at least one restrictor plate 208 operates as a baffle to alter the flow of gases passing over and around it. The at least one restrictor plate 208 may restrict a process gas flowing from a gas inlet (e.g., a showerhead or the like) to the exhaust port and is configured to provide uniform gas flow over the surface of the substrate 110 by providing maximum restriction of the gas flow near the exhaust port (e.g., regions of higher pressure) and minimal restriction to flow opposite the exhaust port (e.g., regions of lower pressure). The substantially equal gas flow alleviates the tendency of the plasma to be pulled towards the exhaust port.
In some embodiments, the at least one restrictor plate 208 is may be a singular ovular plate with a varying radial width oriented such that the maximum gas flow restriction is proximate the exhaust port and the minimum gas flow restriction is opposite the exhaust port. Alternatively, the at least one restrictor plate 208 may be a plurality of ovular segments of the same or varying radial widths that may be disposed proximate each other on the support ring 206 to form an ovular plate of the desired size and profile to optimize gas flow within the chamber during processing. It is contemplated that other configurations may be utilized in processing chambers with different geometries and varying exhaust port locations and or numbers.
The at least one restrictor plate 208 may be coupled to the support ring 206 in any conventional manner such as by bolting, screwing, bonding, or the like. It is contemplated that the at least one restrictor plate may be coupled directly to the substrate support surface or be supported by the liner without the support ring 206. In the embodiment depicted in
In the embodiment depicted in
In some embodiments, altering the width, w, changes the size of the azimuthally non-uniform gap defined by the flow equalizer 180. The width, w, may also vary within a single restrictor plate 208. This allows control of the gas flow around the edge of the flow equalizer and through the gap. In some embodiments, the width, w, of at least a portion of the at least one restrictor plate 208 may be sufficient to substantially close the gap, thereby substantially restricting gas flow through the gap. The variation in the size of the gap may be smooth, such as by using at least one restrictor plate with a tapering width. Alternatively, the variation in the size of the gap 192A may be stepped, such as by using multiple restrictor plates each with a different width.
For example,
In this embodiment, eight restrictor plates 208(a)-(h) are illustratively abutted to substantially surround the substrate support 108. Each restrictor plate has an angle, α, of about 45 degrees, such that the assembled restrictor plates 208 surround about 360 degrees, or about the entire substrate support 108. Each restrictor plate also has a width, w, that defines the size of the azimuthally non uniform gap formed between the outer edge of each restrictor plate and the chamber wall 305 or optionally a liner (not shown in
Alternatively,
Although shown in
In some embodiments, and as depicted in
Referring back to
For example, in
In some embodiments, as illustrated in
In some embodiments, illustrated in
In
In
Thus, as described in the embodiments above, a flow equalizer facilitates substantially uniform flow of a process gas across the surface of a substrate disposed on a substrate support via the formation of an azimuthally non-uniform gap that at least partially circumscribes the substrate support. The varied gap width provides similar flow resistance for a process gas to traverse the gap and reach the pump, thereby improving process characteristics such as pressure and/or velocity profiles above the substrate during processing. In some embodiments, a substantially uniform flow means a ratio of a maximum flow to a minimum flow through the flow equalizer gap of less than or equal to about 1.2, or in some embodiments, less than or equal to about 1.15, or in some embodiments, less than or equal to about 1.1. The measurement of the flow through the gap may be determined by modeling rather than by actual in-situ measurements.
For example, in some embodiments, flowing a gas from a processing volume of a processing chamber to an exhaust volume of the processing chamber through a single azimuthally non-uniform gap having a width that varies inversely with the distance of the gap from a pumping port of the process chamber. The azimuthally non-uniform gap is defined between an edge of a flow equalizer disposed in the process chamber and one of either a chamber wall or a substrate support disposed in the process chamber. The flow equalizer may be disposed in a plane proximate a support surface of the substrate support. As another example, in some embodiments, a gas may be flowed into the processing volume of the process chamber. Flow non-uniformity over the substrate may be reduced by flowing the gas from the processing volume to the exhaust volume past a flow equalizer disposed in the process chamber. The flow equalizer includes at least one restrictor plate disposed in a plane proximate a surface of the substrate and defines an azimuthally non-uniform gap between an edge of the at least one restrictor plate and one of either a chamber wall or the substrate support.
For an additional example, referring to
Referring to any embodiments of the flow equalizer as discussed above (for example, the flow equalizer 180 depicted in
Without the use of the inventive apparatus disclosed herein, the location of the showerhead, substrate support, and exhaust port of conventional process chambers causes an uneven distribution of pressure and velocity of the process gases across the surface of the substrate as the gases flow into and out of the process chamber. It is believed that this uneven pressure and velocity distribution affects the distribution of process gases in the chamber (for example, the location of a plasma or the uniformity of gaseous compositions in the chamber) and, therefore, the uniformity of the process being performed (for example, etch rate uniformity, deposition uniformity, or the like).
For example,
Thus, flow equalizers for processing substrates have been provided herein that provides improved uniformity of gas flow proximate the surface of a substrate. The improved uniformity of gas flow facilitates improvement of substrate processing, such as etching, deposition, or other processes that may benefit from uniformity of gas flow.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
