Patent Application
20130105483
Embodiments of the present invention generally relate to semiconductor processing.
The inventors have observed that conventionally used precursor systems (e.g., gas, liquid vapor, liquid w/inert gas carrier, solid evaporation, solid sublimation, reactive carrier, etc.) used for deposition processes (e.g., epitaxial growth or atomic layer deposition processes) provide precursors that are not of sufficient purity for current semiconductor processing requirements. Moreover, pre-prepared precursors conventionally used are unstable and may decompose, condense, or change states with time.
Therefore, the inventors have provided an improved apparatus for delivering precursors having an improved purity as compared to conventionally generated precursors.
Apparatus for sublimating solid state precursors are provided herein. In some embodiments, an apparatus for sublimating solid state precursors may include a container having a body, a lid, and a removable bottom, wherein the removable bottom is sealable to the body to seal the container when coupled to the body; a tray insertable into the container from a bottom of the container—wherein the tray may include a gas permeable base to support a solid state precursor, the gas permeable base having a through hole disposed proximate the center of the gas permeable base; an outer ring disposed around an outer edge of the base and extending upwardly from the base, the outer ring configured to interface with the lid of the container; and an inner ring disposed within the through hole, the inner ring configured to interface with the lid of the container—an inlet disposed through the lid of the container, the inlet configured to provide a gas through the inner ring of the tray to an area beneath the tray; and an outlet disposed through the lid of the container to allow a gaseous form of the solid state precursor to flow out of the container.
In some embodiments, an apparatus for sublimating solid state precursors may include a container having a body, a lid, and a removable bottom that is sealable to the body to seal the container when coupled to the body; a first tray insertable into the container from a bottom of the container, the first tray comprising a gas permeable base to support a solid state precursor and having a central opening formed through the base, an inner wall disposed about the central opening of the base, and an outer wall disposed about an outer edge of the base, wherein the inner and outer walls interface with the lid of the container to provide an airtight seal between the first tray and the lid; an inlet, disposed through the lid of the container and coupled to an inlet channel passing through the central opening of the base and defined at least in part by the inner wall of the first tray, to provide a gas to an area beneath the first tray; and an outlet, disposed through the lid of the container in a region generally above a region of the first tray between the inner and outer walls of the first tray, to allow a gaseous form of the solid state precursor to flow out of the container.
Other and further embodiments of the present invention are described below.
Embodiments of the present invention, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the invention depicted 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.
Apparatus for sublimating solid state precursors are provided herein. In some embodiments, the inventive apparatus may advantageously provide one or more solid state precursor supporting trays that are easily installed and removed from the apparatus, thereby providing an easier and more efficient mechanism for providing solid state precursors to a solid state precursor sublimation system as compared to conventional precursor sublimation systems. The inventive apparatus may further advantageously provide a point of use generation of precursors, thereby reducing the risk of the precursor condensing, changing state or reacting with the distribution system. The inventive apparatus may further advantageously provide a pressure gradient within the apparatus to facilitate more uniform sublimation of a solid state precursor, thereby providing improved process consistency and material utilization. Although not intended to be limiting in scope, the inventors have observed that the inventive apparatus may be utilized to provide precursors for epitaxial and atomic layer deposition processes.
The process chamber 100 may generally comprise a chamber body 110, support systems 130, and a controller 140. An apparatus for sublimating solid state precursors 180 may be coupled to the process chamber 100 via, for example, a process gas intake port, or inlet 114. The apparatus for sublimating solid state precursors 180 may generally be utilized to sublimate any compatible type of solid state precursor needed for a desired application, for example, such as the exemplary solid state precursors described below.
The chamber body 110 generally includes an upper portion 102, a lower portion 104, and an enclosure 120. A vacuum system 123 may be coupled to the chamber body 110 to facilitate maintaining a desired pressure within the chamber body 110. In some embodiments, the vacuum system 123 may comprise a throttle valve (not shown) and vacuum pump 119 which are used to exhaust the chamber body 110. In some embodiments, the pressure inside the chamber body 110 may be regulated by adjusting the throttle valve and/or vacuum pump 119. The upper portion 102 is disposed on the lower portion 104 and includes a lid 106, a clamp ring 108, a liner 116, a baseplate 112, one or more upper heating lamps 136 and one or more lower heating lamps 152, and an upper pyrometer 156. In some embodiments, the lid 106 has a dome-like form factor, however, lids having other form factors (e.g., flat or reverse curve lids) are also contemplated. The lower portion 104 is coupled to a process gas intake port 114 and an exhaust port 118 and comprises a baseplate assembly 121, a lower dome 132, a substrate support 124, a pre-heat ring 122, a substrate lift assembly 160, a substrate support assembly 164, one or more upper heating lamps 138 and one or more lower heating lamps 154, and a lower pyrometer 158. Although the term “ring” is used to describe certain components of the process chamber 100, such as the pre-heat ring 122, it is contemplated that the shape of these components need not be circular and may include any shape, including but not limited to, rectangles, polygons, ovals, and the like.
During processing, the substrate 101 is disposed on the substrate support 124. The lamps 136, 138, 152, and 154 are sources of infrared (IR) radiation (e.g., heat) and, in operation, generate a pre-determined temperature distribution across the substrate 101. The lid 106, the clamp ring 108, and the lower dome 132 are formed from quartz; however, other IR-transparent and process compatible materials may also be used to form these components.
The substrate support assembly 164 generally includes a support bracket 134 having a plurality of support pins 166 coupled to the substrate support 124. The substrate lift assembly 160 comprises a substrate lift shaft 126 and a plurality of lift pin modules 161 selectively resting on respective pads 127 of the substrate lift shaft 126. In one embodiment, a lift pin module 161 comprises an optional upper portion of the lift pin 128 is movably disposed through a first opening 162 in the substrate support 124. In operation, the substrate lift shaft 126 is moved to engage the lift pins 128. When engaged, the lift pins 128 may raise the substrate 101 above the substrate support 124 or lower the substrate 101 onto the substrate support 124.
The support systems 130 include components used to execute and monitor pre-determined processes (e.g., growing epitaxial films) in the process chamber 100. Such components generally include various sub-systems. (e.g., gas panel(s), gas distribution conduits, vacuum and exhaust sub-systems, and the like) and devices (e.g., power supplies, process control instruments, and the like) of the process chamber 100. These components are well known to those skilled in the art and are omitted from the drawings for clarity.
The controller 140 may be provided and coupled to the process chamber 100 for controlling the components of the process chamber 100. The controller 140 may be any suitable controller for controlling the operation of a substrate process chamber. The controller 140 generally comprises a Central Processing Unit (CPU) 142, a memory 144, and support circuits 146 and is coupled to and controls the process chamber 100 and support systems 130, directly (as shown in
The CPU 142 may be any form of a general purpose computer processor that can be used in an industrial setting. The support circuits 146 are coupled to the CPU 142 and may comprise cache, clock circuits, input/output subsystems, power supplies, and the like. Software routines, such as the methods for processing substrates disclosed herein, for example with respect to
A gas source 117 may be coupled to the apparatus for sublimating solid state precursors 180 to provide one or more gases to facilitate sublimation of the solid state precursor and/or delivery of the sublimated precursor (e.g., as described below). For example, in some embodiments, the gas source 117 may provide a reactive gas, such as hydrogen (H2), hydrogen chloride (HCl), chorine (Cl2), bromine (Br), oxygen (O2), methane (CH4), or the like. Alternatively, or in combination, in some embodiments the gas source may provide an inert gas or a carrier gas, for example such as helium (He), argon (Ar), xenon (Xe), or the like.
Referring to
The container 210 generally comprises a body 206, a lid 226 and a removable bottom 228 configured to seal the container 210 when the bottom 228 is coupled to the body 206. In some embodiments, the lid 226 may include an inlet 230 to provide a gas to the container 210 and an outlet 232 to allow a gaseous form of a solid state precursor to flow out of the container 210. In some embodiments, each of the inlet 230 and outlet 232 may include or may be coupled to a temperature control mechanism 246, 248 (e.g., a heater) to control a temperature of the gases flowing through each of the inlet 230 and outlet 232. In some embodiments, a pressure gauge (e.g., 247, 249) may be coupled to each of the inlet 230 and outlet 232 to allow the pressure of within the container 210 to be monitored. By monitoring the pressure within the container 210, the amount of precursor within the container 210 may also be monitored. The container 210 may be fabricated from any material that is non-reactive with the precursor (e.g., the precursors discussed below) to be sublimed. For example, in some embodiments, the container 210 may be fabricated from quartz or stainless steel.
The one or more trays 208 are insertable into the container 210 from the bottom 231 of the container 210. By configuring the one or more trays in such a manner, the inventors have observed that the one or more trays 208 may be easily and quickly provided to, and removed from, the apparatus for sublimating solid state precursors 180, thereby providing an easier and more efficient mechanism for providing solid state precursors to the solid state precursor sublimation system 180, as compared to conventional precursor sublimation systems.
Although four trays 208 are shown, any number of trays 208 needed to perform a desired sublimation process may be provided. For example, in some embodiments, less than four, such as one, two, or three trays 208 may be provided. Alternatively, in some embodiments, more than four trays 208 may be provided.
Each tray 208 generally comprises a gas permeable base 242 having a through hole 243, an outer ring 222 (or outer wall) disposed about an outer edge 219 of the gas permeable base 242 and an inner ring 240 (or inner wall) disposed within the through hole 243. The outer ring 222 and inner ring 240 may be fabricated from any material that is non-reactive with the particular precursors used (e.g., the precursors discussed below) to be sublimed. For example, in some embodiments, the outer ring 222 and inner ring 240 may be fabricated from quartz or stainless steel. In some embodiments, the outer ring 222 and inner ring 240 may interface with the lid 226 of the container 210 to provide an airtight seal between the tray 208 and the lid 226 to facilitate a flow of gas (e.g., sublimed precursor) towards the outlet 232. Alternatively, or in combination, in some embodiments, for example, where the apparatus for sublimating solid state precursors 180 comprises a plurality of trays 208 stacked atop one another within the container 210 (e.g., as depicted in
The inventors have observed that conventional precursor ampoules heated by an external heat source typically display slow temperature response time due to poor thermal coupling. Accordingly, and referring back to
The temperature control unit 224 may comprise any mechanism suitable to control the temperature within the container 210. For example, in some embodiments, the temperature control unit 224 may comprise an active temperature control system, for example a heater, such as a resistive heater. Alternatively, or in combination, in some embodiments, the temperature control unit 224 may comprise a passive temperature control system, for example, such as a series of conduits configured to allow a flow of a temperature control fluid through the temperature control unit 224.
The gas source 117 provides the one or more gases (e.g., the one or more gases discussed above) to the annulus 251 via the inlet 230 which flow to an area 213 beneath a bottom most tray (e.g. tray 215) of the one or more trays 208. For example, in some embodiments, an inlet channel may pass through the central opening of the base of the tray. The inlet channel may is defined at least in part by the inner walls, or inner rings, of the trays 208, to provide the one or more gases to the area beneath the tray. In some embodiments, a gas manifold 212 may be disposed within the area 213 beneath a bottom most tray 215 and coupled to the annulus to provide a uniform distribution of the gases to the one or more trays 208. The gas manifold 212 may be fabricated from any material that is non-reactive to the gases provided by the gas source, for example, such as quartz or stainless steel.
The gas permeable base 242 supports the solid state precursor and allows the sublimated solid state precursor to pass through. The gas permeable base 242 may comprise any materials suitable to allow a flow of gas (e.g., the sublimed precursor) through the gas permeable base 242. For example, in some embodiments, the gas permeable base 242 may comprise a frit, for example such as a quartz frit or stainless steel frit. In such embodiments, the frit may comprise any pore size suitable to allow the flow of sublimed precursor through the frit while substantially preventing larger particles of the solid precursor from passing through the gas permeable base 242. For example, in some embodiments, the frit may comprise a pore size of about 25 to about 150 microns, or in some embodiments, about 100 microns.
In some embodiments, by varying the pore size of the gas permeable base 242 of each tray 208, the pressure within each tray 208 may be controlled, thereby allowing the rate of sublimation of the solid state precursor within each tray 208 to be controlled. For example, as the pore size of the gas permeable base 242 of the tray 208 decreases, the pressure within the tray increases and the reaction rate of the precursor within the tray decreases.
The inventors have observed that in conventional precursor sublimating systems using multiple stages (e.g., shelves), the solid state precursor in the first stages are consumed from the first stages at a higher rate than the later stages. Because of this disparity in rate of consumption of the solid state precursor and the changing of the packing of the solid state precursor over time, the solid state precursor in the later stages need to be impacted in order to settle the material and recover sublimation rate, thereby making the process inefficient. Accordingly, the inventors have observed that by creating a pressure gradient (e.g., by varying the pore size of the gas permeable base 242 of each tray 208) across the trays 208 wherein the lowest tray of the trays 208 has the highest pressure and the highest tray of the trays 208 has the lowest pressure, the rate of consumption of the solid state precursor in each tray 208 may be more uniform, thereby providing a more consistent sublimation rate across all of the trays and allowing maximum solid state precursor utilization prior to refilling or replacing the trays 208, thus improving process consistency and increasing the efficiency of the sublimation process.
In some embodiments, a cover frit (shown in phantom at 245) may be disposed atop the gas permeable base 242. The cover frit 245 may be fabricated from the same, or in some embodiments, a different, material than that of the gas permeable base 242 discussed above. In addition, the cover frit 245 may comprise any pore size suitable to allow the flow of sublimed precursor through the cover frit 245, for example, such as within the pore size range discussed above with respect to the gas permeable base 242. When present, the solid state precursor may be disposed between the gas permeable base 242 and the cover frit 245, thereby allowing the tray 208 to be “pre-charged” or loaded with the precursor prior to use. In some embodiments, the pre-filled tray may be hermitically sealed to reduce exposure of the precursor to an atmosphere outside of the container 210, thereby increasing stability and decreasing decomposition of the precursor. In such embodiments, the hermetic seal may be broken (e.g., the tray may be unpackaged) prior to use of the tray.
In some embodiments, a pressure monitor (pressure monitors 220, 221, 223, 225, 227) may be coupled to each of the one or more trays 208 to monitor an inter-stage pressure (pressure within each of the one or more trays 208). By monitoring the pressure at each of the one or more trays 208, the amount of precursor disposed on each of the one or more trays 208 may be monitored.
In some embodiments, a shell 202 may be disposed around an outer surface 234 of the container 210. The shell 202 generally comprises a body 206, bottom 216, and an optional top (shown in phantom at 236). In some embodiments a seal 218 may disposed between the bottom 216 and body 206 and/or the top 236 and body 206 to provide a vacuum seal between the components of the shell 202. The seal 218 may be any type of seal, for example, such as an o-ring fabricated from, for example, a high temperature resistant polymer, such as polytetrafluoroethylene (PTFE).
When present, the shell 202 may facilitate enhanced control over a temperature of the container by increasing or decreasing a rate of heat transfer to or from the container 210 during use. For example, in some embodiments, the shell 202 may comprise an insulative material to reduce heat loss from the container 210, thus allowing the container 210 maintained at a higher temperature while not requiring additional heating. Alternatively, or in combination, the shell 202 may provide an active heating or cooling of the container 210. For example, in some embodiments, the shell 202 may include one or more conduits disposed within the shell and configured to allow a flow of a heat transfer fluid through the shell 202. Alternatively, or in combination, in some embodiments, the shell 202 may comprise one or more embedded heaters, such as resistive heaters or the like. In some embodiments, an external heat source, such as an IR lamp, may be disposed external to the shell 202 to provide heat energy to the shell 202. In some embodiments, a liner 204 may be disposed between the shell 202 and container 210. The liner 204 may be fabricated from any material suitable to provide a desired amount of heat transfer, for example, such as quartz.
In preparation of the apparatus for sublimating solid state precursors 180, first the one or more trays 208 are loaded with a solid state precursor, such as a powdered, pellet or sintered solid state precursor. The trays 208 are then stacked atop the bottom plate 228 and interlocked together (e.g., via mating features such as the tabs 304, 308 and cavities 310, 312 described above). The trays 208 and bottom plate 228 may then installed into the body 206 of the container 210. The container 210 may then be optionally purged and pressurized with an inert gas (e.g., helium (He), argon (Ar), xenon (Xe), or the like). When pressurized, a sniffing procedure may be utilized to determine whether the container 210 is air tight. A pressure drop within the container is then recorded within the container 310 to provide a baseline pressure to later determine consumption of the solid state precursor. The apparatus for sublimating solid state precursors 180 is then installed in the process system (e.g., coupled to the process chamber 100 described above). The process parameters (e.g., process gases, pressure and temperature required for sublimation, or the like) are then determined and entered into a controller (e.g., controller 140 described above). Initial process conditions of the and the sublimation process may begin.
In operation of the apparatus for sublimating solid state precursors 180, the one or more process gases provided by the gas source 117 are provided to the annulus 241 formed by the inner ring 240 of the one or more trays 208. The one or more process gases flow down the annulus 241 to an area 213 beneath a bottom most tray (e.g. tray 215) of the one or more trays 208 and is distributed to the bottom most tray. The gas manifold 212 provides a uniform distribution of the one or more gases to the bottom tray. The one or more process gases then pass through the gas permeable base 242 and react with, or carry, the sublimated precursor (wherein the sublimation may be controlled by one or more of a reaction with the one or more process gases, temperature, or pressure at each tray 208) up the container through each of the one or more trays 208. The sublimated precursor then flows to the outlet 232 and is provided to the process chamber 100.
In an exemplary application of the apparatus for sublimating solid state precursors 180 described above, in some embodiments, the apparatus for sublimating solid state precursors 180 may be utilized to provide a tin (Sn) precursor to a process chamber. The inventors have observed that tin (Sn) may be utilized as a stressor in certain deposition process, for example, such as in a germanium (Ge) based epitaxial or atomic layer deposition (ALD) processes. However, ultra high purity precursors are not readily available. Moreover, pre-prepared hydrides of tin (e.g., stannane (SnH4)) are unstable and organotin compounds contain an impermissibly large amount of carbon. Accordingly, in some embodiments the apparatus for sublimating solid state precursors 180 may be utilized as a point of use precursor source to provide tin (Sn) precursors, including high purity precursors. For example, in such embodiments a solid state tin (Sn) precursor may be provided to the trays 208 and a process gas comprising one or hydrogen chloride gas (HCl), chlorine (Cl2), deuterium (D) or hydrogen (H2) may be provided to the container 210. The tin precursor may be then generated in accordance with the following equations:
Sn(s)+2HCl(G)→SnCL2+H2(G) (1)
Sn(s)+2Cl2(G)→SnCl4(G) (2)
Sn(s)+2H2(G)→SnH4(G) (3)
Sn(s)+2D(G)→SnD4(G) (4)
In another exemplary application of the apparatus for sublimating solid state precursors 180 described above, in some embodiments, the apparatus for sublimating solid state precursors 180 may be utilized to provide a serial conversion for multistep reactions. In such embodiments, each tray 208 of the apparatus for sublimating solid state precursors 180 may be utilized to perform one step of the multistep reaction, or in some embodiments, a single apparatus for sublimating solid state precursors 180 may be utilized to perform one step of the multistep reaction. An exemplary multistep reaction may include a first step of generation of a precursor, a second step of a conversion of the precursor and a third step of purifying the precursor. For example, in some embodiments, the apparatus for sublimating solid state precursors 180 may be utilized to generate a tin precursor (e.g., SnH4) using lithium aluminum hydrate (LiAlH4).
In such embodiments, a solid state tin (Sn) precursor may be provided to a first tray of the one or more trays 208, lithium aluminum hydrate LiAlH4 may be provided to a second tray of the one or more trays 208 and a third tray may be used as a cold trap to trap unwanted solids. The tin precursor may be then generated in accordance with the following equations/steps:
Sn(s)+2Cl2(g)→SnCl4(G) (1)
SnCl4(G)+LiAlH4(s)→SnH4(G)+LiCl(S)+AlCl3(s) (2)
solid AlCl3(s) trapped in upper most tray (3)
Thus, apparatus for sublimating solid state precursors have been provided herein. In some embodiments, the inventive apparatus may advantageously provide one or more solid state precursor supporting trays that are easily installed and removed from the apparatus, thereby providing an easier and more efficient mechanism for providing solid state precursors to a solid state precursor sublimation system as compared to conventional precursor sublimation systems. The inventive apparatus may further advantageously provide a point of use generation of precursors, thereby reducing the risk of the precursor condensing, changing state or reacting with the distribution system. The inventive apparatus may further advantageously provide a pressure gradient within the apparatus to facilitate uniform sublimation of a solid state precursor, therefore providing an improved process consistency and material utilization.
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.
