Gas-phase chemical reactor and method of using same

FIELD OF THE DISCLOSURE The present disclosure relates generally to gas phase apparatus and processes. More specifically, exemplary embodiments of the present disclosure relate to gas phase chemical reactors suitable for precursor soak applications, systems including such reactors, and methods of using the reactors and systems.

Gas phase chemical reactors can be used for a variety of applications, such as to deposit and/or etch materials on the surface of a substrate. A typical gas phase chemical reactor includes a reaction chamber, a gate valve that opens to receive the substrate and closes during substrate processing, and one or more gas sources coupled to the reaction chamber.

During substrate processing, one or more precursors flow into the reaction chamber to deposit material on the substrate surface and/or react with and etch material on the substrate surface. Typically, during substrate processing, the gas flow reaches a steady state and is continuous, i.e., after a period of time, gas is introduced into the reaction chamber and unreacted gas and any gaseous by-products are continuously removed from the reaction chamber.

As an example, during a typical atomic layer deposition (ALD) process, a first precursor is provided to a reaction chamber in a continuous manner for a period of time or steps such that unreacted first precursor and/or any gaseous byproducts of the first precursor are removed during the step. This facilitates the precursor flowing across the surface of the substrate during the step. The substrate is then exposed to reduced pressure and/or a purge gas to further remove excess precursor and/or byproducts during a purge step. These steps can be repeated as necessary with the same and/or additional precursors until a film of the desired thickness is obtained.

While such techniques are relatively good for some applications, in other applications, continuous flow of one or more precursors during substrate processing may result in unreacted precursors with undesirable properties, undesirably long substrate processing times, and/or wasted film. Furthermore, using such techniques, it may be difficult to obtain the desired concentration, partial pressure, and/or absolute reaction chamber pressure to promote some reactions. For example, in some ALD processes (e.g., using SAM.24 (air-liquid) as the silicon precursor, the precursor may reach an initial growth rate saturation level quickly, but even with relatively long pulse times, the precursor may not reach full growth rate saturation at the partial pressure of the common precursor, and thus the growth rate of the deposited film may be lower than desired. In other processes, a relatively high concentration/partial pressure of one or more precursors is desirable to promote reaction at a desired rate (e.g., TiCl₄and N.H.₃In the case of TiN deposition from NH₃It is desirable to have a relatively high concentration or partial pressure to drive the film-forming reaction to completion before by-products generate undesirable/poisoning species). Such high partial pressures may be difficult to achieve in typical reactors. Furthermore, the formation of self-assembled monolayers may require relatively long exposure times and/or relatively high precursor concentrations/partial pressures to achieve the desired film properties, conditions that may be difficult to obtain in typical reactors. Furthermore, chemical vapor reactors often employ relatively expensive gas distribution equipment to distribute gases uniformly across the substrate surface, but such designs may be desirable when precursors flow continuously across the substrate surface. Thus, improved apparatus and methods for gas phase chemical processing are desired.

The discussion of problems provided in this section is included in the present disclosure solely for the purpose of providing a context for the invention, and should not be taken as an admission that any or all of the discussion was known at the time the invention was made.

Various embodiments of the present disclosure provide apparatus and methods that can provide extended residence times, partial pressures, and/or absolute pressures of one or more precursors in a reaction chamber of a gas phase chemical reactor. As described in more detail below, various systems and methods can allow for the use and evacuation of relatively fewer precursors compared to conventional apparatus and methods, reducing costs associated with processing a substrate. Exemplary systems and methods can also facilitate high growth rates and/or promotion of reactions that would not otherwise occur. Additionally or alternatively, exemplary embodiments can provide relatively rapid pumping/evacuation of gases from a reaction region or chamber in a gas phase chemical reactor. Furthermore, some exemplary systems and methods do not require the use of relatively expensive gas distribution equipment to achieve desired process uniformity.

According to at least one exemplary embodiment of the present disclosure, the gas phase chemical reactor includes a reaction chamber for processing a substrate, a fill/unload chamber with an opening for receiving the substrate and a valve (e.g., a gate valve) for sealing the opening, a susceptor having an upper surface for receiving the substrate, the susceptor being movable in the fill/unload chamber, the upper surface of the susceptor defining at least a portion of the bottom of the reaction chamber when the substrate is in the processing position, and a vacuum source for evacuating the fill/unload chamber. The gas phase chemical reactor may further include a controller for controlling, for example, a precursor delivery process and an evacuation process. The controller includes a memory programmed to enable the controller to perform the following steps: supplying a precursor to the reaction chamber while evacuating the fill/unload chamber while the susceptor is in the processing position, stopping the flow of the precursor, and evacuating the reaction chamber by moving the susceptor into the fill/unload chamber. Furthermore, the gas phase chemical reactor may include a protective shield (e.g., a plate) for protecting the valve. The protective shield may be attached to the valve. According to various aspects of these embodiments, the protective shield extends beyond at least a top surface of the gate valve. According to further exemplary aspects, the gas phase chemical reactor includes an inert gas source, and inert gas from the inert gas source is provided between an inner wall of the loading/unloading chamber and a surface of the protective shield. The gas phase chemical reactor can also include a movable shaft coupled to the susceptor. In these cases, the gas phase chemical reactor can include a protective cover (e.g., bellows) around at least a portion of the movable shaft and the shaft opening within the bottom of the loading/unloading chamber. As discussed in more detail below, according to various examples, the volumes of the reaction chamber and the loading/unloading chamber can be configured to facilitate rapid pumping of the reaction chamber. For example, the volume ratio of the interior volume of the reaction chamber to the interior volume of the loading/unloading chamber can range from about 1:5 to about 1:160, about 1:10 to about 1:80, or about 1:20 to about 1:60. The gas phase chemical reactor described herein can include a showerhead gas distribution device. In at least some cases, the exemplary gas phase chemical reactor may not include a showerhead gas distribution device or similar device, and therefore may be less complicated and/or less expensive than other gas phase chemical reactors. According to further aspects, the gas phase chemical reactor includes a guide for directing the flow of gas from the reaction chamber to the loading/unloading chamber, for example, during a purging step. The guide may be further configured to mitigate gas from the reaction chamber contacting the walls of the loading/unloading chamber. In these cases, the gas phase chemical reactor may not include a protective shield.

According to additional exemplary embodiments of the present disclosure, a system includes a gas phase chemical reactor, such as the gas phase chemical reactors described herein, and one or more other components, such as a vacuum source, one or more precursor sources, one or more purge gas sources, one or more carrier gas sources, a transport or robotic arm, etc.

According to yet further exemplary embodiments of the present disclosure, a method (e.g., for processing a substrate) includes moving a susceptor from a loading/unloading position to a processing position, providing a precursor to a reaction chamber while the susceptor is in the processing position (e.g., by evacuating the loading/unloading chamber by providing a vacuum or by maintaining a vacuum in the loading/unloading chamber), stopping the flow of the precursor, and moving the susceptor into the loading/unloading chamber. When the substrate moves to the loading/unloading chamber, the substrate may be exposed to a second pressure, e.g., lower than the first pressure. The method may further include opening a valve to receive the substrate, closing the valve to seal the opening, and/or protecting the valve with a protective shield. Additionally or alternatively, the method may include providing a carrier gas during all or a portion of the precursor providing step.

The foregoing summary and the following detailed description are exemplary and explanatory only and are not intended to limit the scope of the disclosure or the claimed invention.

A more complete understanding of the embodiments of the present disclosure can be obtained by reference to the detailed description and claims when considered in conjunction with the following illustrative drawings.

<figref num="1">FIG. 1 illustrates a system including a gas phase chemical reactor in a loading/unloading position in accordance with at least one embodiment of the present disclosure.</figref><figref num="2">FIG. 2 illustrates a system including a gas phase chemical reactor at a processing location in accordance with at least one embodiment of the present disclosure.</figref><figref num="3">FIG. 3 illustrates a portion of a system including a gas phase chemical reactor in a purge position in accordance with at least one embodiment of the present disclosure.</figref><figref num="4">FIG. 4 illustrates a valve and protective shield in accordance with at least one embodiment of the present disclosure.</figref><figref num="5">FIG. 5 illustrates a method in accordance with at least one embodiment of the present disclosure.</figref><figref num="6">FIG. 6 illustrates a pressure diagram in accordance with at least one embodiment of the present disclosure.</figref><figref num="7">FIG. 7 illustrates a portion of another system including a gas phase chemical reactor in accordance with at least one embodiment of the present disclosure.</figref>

It will be understood that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of the illustrated embodiments of the present disclosure.

The descriptions of exemplary embodiments of reactors, systems, and methods provided below are intended to be merely exemplary and explanatory only, and the following descriptions are not intended to limit the scope of the disclosure or claims. Moreover, the recitation of multiple embodiments having recited features is not intended to exclude other embodiments having additional features or other embodiments incorporating different combinations of the recited features.

Any ranges given in this disclosure can include or exclude the endpoints. Additionally, any values for the variables given (whether they are indicated as "about" or not) can refer to exact or approximate values, including equivalents, and can refer to the average, median, representative value, or majority, etc.

As used herein, precursor refers to one or more gases that participate in a chemical reaction. The chemical reaction may take place in the gas phase and/or between the gas phase and the surface of the substrate and/or with species on the surface of the substrate.

The systems, reactors, and methods described herein may be used in a variety of applications where, for example, a relatively high concentration, relatively high partial pressure, and/or relatively high residence time of one or more gases, such as one or more precursors, in the reaction chamber is desired, mitigation of precursor waste that may otherwise occur is desired, and/or a relatively high absolute pressure in the reaction chamber is desired. By way of example, the exemplary systems, reactors, and methods may be used in atomic layer deposition (ALD) applications where an increase in the partial pressure and/or concentration of one or more precursors is desired to drive the film formation process and/or to prevent undesirable by-product formation/poisoning, such as TiCl, in ALD applications where a precursor reaches soft growth rate saturation (e.g., using SAM.24 precursor in oxygen plasma) using typical ALD processing techniques.₄and N.H.₃The ALD method may be used in ALD reactions where high partial pressures are desired, such as during the formation of self-assembled monolayers (e.g., single precursor reactions), in ALD reactions where high partial pressures of precursors are desirable, such as to mitigate the ALD deposition of TiN using, and in conventional ALD processes (e.g., formation of aluminum oxide from an oxidizer such as trimethylaluminum (TMA) and water), where relatively expensive gas distribution equipment (e.g., showerheads) are often used to distribute one or more precursors across the surface of a substrate. Although the systems, reactors, and methods are described below in the context of ALD reactors, the systems, reactors, and methods are not limited unless otherwise noted.

Turning now to the figures, Figures 1-3 show a system 100 in accordance with at least one embodiment of the present disclosure. Figure 1 shows the system 100 in a fill/unload position. Figure 2 shows the system 100 in a processing position. Figure 3 shows a portion of the system 100 in a purge position.

The system 100 includes a gas phase chemical reactor 102 including a reaction chamber 104 and a fill/unload chamber 106, a first precursor source 107, a second precursor source 108, a purge gas source 110, a gas distributor 112, a susceptor 114, a vacuum source 116, and a controller 134. The system 100 also includes a valve (e.g., a gate valve) 124 that seals an opening 120 in the fill/unload chamber 106, and a protective shield 126 that protects the valve 124 from exposure to process gases used in the reaction chamber 104 and purged through the fill/unload chamber 106. A valve actuator 136, which may be coupled to the controller 134, may be used to open and close the valve 124. The system 100 may optionally include a remote plasma unit 144 to activate one or more gas precursor sources 1-7, 1-8 and/or the purge/carrier source 110. Additionally or alternatively, the system 100 can include a direct plasma system, e.g., the susceptor 144 or a portion thereof can form an electrode of a direct plasma apparatus and the gas distribution apparatus 112 can form another electrode, and/or the system 100 can include an inductively coupled plasma apparatus.

As described in more detail below, during operation of the system 100, a substrate (not shown) is transported through the opening 120 to the susceptor 114 in the load/unload chamber 106 and moved (e.g., using shaft 128) to the reaction chamber 104. During processing, the reaction chamber 104 can be isolated from the load/unload chamber 106, and the substrate can be exposed to one or more precursors (e.g., sources 107, 108) in the reaction chamber 104 while a vacuum (e.g., a pressure lower than the pressure in the reaction chamber 104) is maintained in the load/unload chamber 106. As used herein, the term isolated does not require a complete seal, but can also include a substantial seal and/or a tortuous path between the reaction chamber 104 and the loading/unloading chamber 106 such that gas from the precursor sources 107, 108 does not flow continuously through the reaction chamber 104, but rather the amount of precursor continues to rise over a period of time during the soak period and can remain substantially constant (e.g., within 10 percent, 5 percent, or 1 percent of the peak value minus any reduction due to chemical reaction in the reaction chamber 104). During the soak period, the substrate can remain in the reaction chamber 104 while the precursor is introduced into the reaction chamber 104. As used herein, the soak period refers to the period after the flow of gas from the precursor source is stopped, while the reaction chamber 104 is isolated from the loading/unloading chamber 106, so that the substrate remains in contact with the precursor in the reaction chamber 104 for a period of time after the precursor flow is stopped. At the end of the soak period, the substrate is lowered into the loading/unloading chamber 106. At this point, the reaction chamber 104 can be evacuated using the pressure differential between the reaction chamber 104 and the load/unload chamber 106 and the vacuum provided by the vacuum source 116. A purge gas (e.g., from a purge gas source 110) can optionally be provided to further facilitate purging of any unreacted precursors and/or by-products. These steps can be repeated with the same or different precursors until the desired film is formed on the surface of the substrate.

1, the reactor 102 may be formed, for example, from stainless steel, titanium, and/or aluminum, or the like. Additionally, the reactor 102 may be an independently operating reactor or may form part of a cluster tool, which may include similar or different reaction chambers. According to an exemplary embodiment of the present disclosure, the reaction chamber 104 is relatively small (e.g., for processing a substrate having a diameter of about 300 mm, the internal volume of the reaction chamber 104 may be about 0.5 to about 1 or about 0.7 dm³). The relatively small internal volume allows high partial and/or absolute pressures to be reached quickly using a relatively small amount of precursor, thereby facilitating rapid and inexpensive processing of substrates. By way of further example, the internal volume ratio of the internal volume of the loading/unloading chamber 106 to the internal volume of the reaction chamber 104 may be relatively high. For example, the internal volume ratio of the internal volume of the loading/unloading chamber 106 to the internal volume of the reaction chamber 104 may range from about 5:1 to about 160:1, from about 10:1 to about 80:1, or from about 20:1 to about 60:1, or greater than 5, 60, or 160. The relatively high volume ratio allows for rapid purging of the reaction chamber 104, and facilitates rapid processing of substrates when the loading/unloading chamber 106 is maintained at a lower pressure than the reaction chamber 104.

According to some embodiments of the present disclosure, the fill/unload chamber 106 may have a relatively simple design, such as a substantially hollow cylindrical shape with a bottom (e.g., the portion of the fill/unload chamber below where the gate is attached to the actuator 136). This allows the bottom to be easily removed for replacement and/or cleaning. Additionally or alternatively, the system 100 may include a removable (e.g., disposable) liner, as shown in FIG. 7. Additionally or alternatively, the fill/unload chamber 106 may include a purge gas inlet near the interface with the reaction chamber 104 to further facilitate purging of reactants and reduce contact of reactants with the interior surfaces of the fill/unload chamber 106. One or more of the walls of the fill/unload chamber 106, e.g., walls 146, 148, and/or 150, may be heated to reduce any condensation thereon (e.g., to a temperature above the condensation temperature of the precursors and/or any reaction by-products).

The first and second precursor sources 107, 108 may include any material suitable for gas phase reactions. The precursors in the sources 107, 108 may initially be solids, liquids or gases. In the case of solids and liquids, the precursors may be converted to a gaseous state by heating, using a bubbler, etc.

The purge/carrier gas source 110 can include any suitable gas or material capable of purging the reaction chamber 104 and/or suitable as a carrier gas. Exemplary purge and/or carrier gases include argon, nitrogen, and/or hydrogen. When a carrier gas is provided, the carrier gas can be mixed with one or more gases, for example, from the first precursor source 107 and/or the second precursor source 108, at the mixer 122, and/or before the mixer 122. Although the system 100 is illustrated with two precursor sources and one purge/carrier gas source, the system 100 can include any suitable number of precursor sources, purge gas sources, and/or carrier gas sources, and in some cases need not include a purge gas source and/or carrier gas source. Further, although illustrated as being coupled to the gas distribution apparatus 112, as described below, the purge gas source 110 or another purge gas source may additionally or alternatively be coupled to the loading/unloading chamber 106 or for directly purging the loading/unloading chamber 106 and/or for use as a gas curtain.

The gas distribution apparatus 112 may be configured to provide a vertical (as shown) or horizontal gas flow to the reaction chamber 104. Exemplary gas mixtures and gas distribution apparatus are described in U.S. Patent No. 8,152,922, entitled "Gas Mixer and Manifold Assembly for ALD Reactor," issued April 10, 2012, the contents of which are incorporated herein by reference to the extent not inconsistent with this disclosure. As an example, the gas distribution apparatus 112 may include a showerhead. However, according to other embodiments, the gas distribution apparatus 112 need not include a showerhead, but may include a relatively simple gas inlet.

The susceptor 114 may be formed of, for example, SiC or SiC-coated graphite. According to some embodiments of the present disclosure, the susceptor 114 may include openings such that lift pins are housed within the susceptor 114 during processing and protrude above the upper surface 115 of the susceptor 114 during the substrate transfer process. An exemplary susceptor and lift pin mechanism is described in U.S. patent application Ser. No. 15/672,096, entitled "SUBSTRATE LIFT MECHANISM AND REACTOR INCLUDING SAME," the contents of which are incorporated herein by reference to the extent not inconsistent with the present disclosure.

The vacuum source 116 can include any suitable vacuum source capable of providing the desired pressure to the reaction chamber 104. The vacuum source 116 can include, for example, a dry vacuum pump alone or in combination with a turbomolecular pump. According to various embodiments of the present disclosure, the vacuum source 116 can provide a pressure within the reactor 102, particularly a pressure of about 1 to about 10^-6, about 0.1 to about 10^-4, or about 10^-2~ approx. 10^-3 The reaction chamber 104 is configured to provide a pressure of 100 Torr to the fill/unload chamber 106. One or more vacuum sources 116 may be coupled to the reaction chamber 104 and/or the fill/unload chamber 106.

Valve 124 may include any suitable valve, such as a gate valve, for sealing opening 120 in load/unload chamber 106. According to an exemplary embodiment of the present disclosure, valve 124 is a gate valve including plate 402 shown in FIG. 4. Valve 124 may be opened and closed (e.g., moved up and down) using actuator 136, which may be coupled to controller 134.

A protective shield 126 can be used to protect the valve 124 from reactive species when species are purged from the reaction chamber 104 to the load/unload chamber 106. The protective shield 126 can be formed, for example, of stainless steel, titanium, or aluminum, having dimensions that are slightly (e.g., about 2%, 5%, 10%, 15%, or 20%) larger in height (H) and/or length (L) than the valve 124. As shown in FIG. 4, the protective shield 126 can be fixedly or removably attached to the valley 124 using one or more fasteners 404, 406, which can be or include, for example, welds, bolts, screws, and the like. Alternatively, the valve 124 and the protective shield 126 can be of unitary construction. To further protect the valve 124, a flow (e.g., 25-100 sccm) of an inert gas (e.g., nitrogen, argon, etc.) can be provided between the valve 124 and/or the inner wall 137 of the reactor 102/loading/unloading chamber 106 and the protective shield 126 to form a gas curtain that prevents or mitigates gas from the reaction chamber 104 reaching the valve 124 during the purge process. Additionally, the protective shield 126 can be configured such that the protective shield 126 does not touch the inner wall of the loading/unloading chamber 106 when the protective shield 126 moves. Alternatively, the protective shield 126 can be configured such that the protective shield 126 forms a tight seal with the top inner surface of the loading/unloading chamber 106 (e.g., above the opening 120) to partially or completely mitigate the need for a sealing gas flow when the valve 124 is closed.

The shaft 128 may be configured to move up and down to facilitate loading and unloading of the substrate through the opening 120 and to move the substrate to a processing position within the reaction chamber 104. In some embodiments, the shaft 128 may also rotate during substrate processing and/or during substrate loading/unloading operations, although in some examples, it may not be necessary or desirable to rotate the shaft 128. The shaft 128 may also receive and hold various wiring, for example, for heaters integrated and/or attached to the susceptor 114, thermocouples, and the like. Although the system 100 is described in connection with a shaft that moves up and down according to other exemplary embodiments of the present disclosure, the susceptor may move horizontally between the loading/unloading chamber and the reaction chamber, and the susceptor may remain stationary and the reaction chamber and/or the loading/unloading chamber may move relative to the susceptor.

In the illustrated example, the system 100 also includes a protective cover 130 (e.g., a bellows) that seals the shaft 128 and the loading/unloading chamber 106 from the outside environment of the reactor 102 and protects portions of the shaft and/or components attached thereto) from exposure to chemicals.

The system 100 may also include a guide 132 for directing the flow of gas from the reaction chamber 104 to the load/unload chamber 106 and away from the valve 120 during the purging process. The guide 132 may be formed, for example, from stainless steel, titanium, or aluminum, and may include a slope or curved surface that directs the flow of gas from the reaction chamber 104 away from the valve 124.

The controller 134 may be coupled to mass flow controllers coupled to one or more of the shaft 128, the valve actuator 136 and/or the valves 138-142, the first precursor source 107, the second precursor source 108, and the purge/carrier source 110, etc., to perform various steps described herein. For example, the controller 134 may include a memory in which the controller 134 is programmed to perform the following: providing precursor to the reaction chamber while the susceptor is in the processing position, while the loading/unloading chamber is evacuated with a vacuum source, stopping the flow of precursor, and evacuating the reaction chamber by moving the susceptor into the loading/unloading chamber.

The memory can be programmed to enable the controller to perform the following steps after stopping the flow of precursor: exposing the substrate to the precursor in the reaction chamber for a soak period, and evacuating the reaction chamber by moving the susceptor to the load/unload chamber after the soak period.

Additionally or alternatively, the controller 134 may be configured to cause the system 100 to automatically perform any of the methods described herein.

As mentioned above, FIG. 1 shows the system 100 in a load/unload position. In this position, the valve 124 is in an open position, allowing a substrate to be loaded and/or unloaded onto the surface 115 of the susceptor 114 using a robot or transport arm 118. Once the substrate is loaded onto the susceptor, the valve 124 is closed to seal the load/unload chamber 106 and expose the load/unload chamber 106 (and reaction chamber 104) to the vacuum source 116. For example, exposing the load/unload chamber 106 to the vacuum source 116 may increase the pressure within the load/unload chamber 106 to between about 1 and about 10.^-6, about 0.1 to about 10^-4, or about 10^-2~About 10-³ Torr.

After the substrate is loaded onto the susceptor 114, the susceptor 114 is raised to a processing position, as shown in FIG. 2. In this position, the top surface 115 of the susceptor 114 forms at least a portion or bottom of the reaction chamber 104. With the substrate in the processing position, one or more precursor gases flow across the surface of the substrate. The flow of precursors can then be stopped for a soaking period. During this period, the partial pressure of the one or more precursors and/or absolute pressure in the reaction chamber 104 can be maintained at a relatively high level by sealing the reaction chamber 104 from the loading/unloading chamber 106. A seal can be formed between the susceptor surface 302 and the interior surface 304 of the reaction chamber 104. The surfaces 302 and 304 can be machined and mated (e.g., having linear mating inclined surfaces as shown) to provide a substantial seal between the reaction chamber 104 and the loading/unloading chamber 106.

3, the susceptor 114 can be lowered to purge the reaction chamber 104. Purging of the reaction chamber 104 can occur, at least in part, from a pressure differential between the load/unload chamber 106 and the reaction chamber 104 and/or by providing a source of purge gas, for example from a barge gas source 110, through a gas distribution device 112.

FIG. 7 illustrates another system 700 according to an exemplary embodiment of the present disclosure. System 700 is similar to system 100, except that system 700 includes a relatively simple inlet port 722 rather than a gas distribution device 112. System 700 also includes a reaction chamber 704 defined by a top surface 702 of the reaction chamber rather than a gas distribution device. This relatively simple design may be easier and/or less expensive to manufacture relative to system 100. System 700 is also illustrated with a liner 740 and a cooler/condenser plate 716, which may be used to getter precursors and/or by-products during a purge step. Any combination of liner 740 and cooler/condenser plate 716 may be included in system 100 as well.

5 illustrates a method 500 according to an exemplary embodiment of the present disclosure. The method 500 includes loading a substrate onto a susceptor (step 502), closing a valve (step 504), reducing the pressure in the loading/unloading chamber of the reactor (step 506), moving the susceptor to a processing position (step 508), optionally reducing, i.e., reducing the pressure in the reaction chamber (step 510), starting the flow of precursor gas (step 512), optionally flowing a carrier gas (step 514), stopping the flow of precursor gas and optionally stopping the flow of carrier gas (step 516), immersing the substrate in the presence of one or more precursors (step 518), lowering the susceptor and starting a purge process (step 520), optionally repeating steps 506-520 with the same or different precursors (step 522), and unloading the substrate (step 524).

During step 502, the valve (e.g., valve 124) is in an open position so that a substrate can be placed on a susceptor (e.g., susceptor 114) in the loading/unloading chamber (e.g., loading/unloading chamber 106) of the reactor. The valve is then closed during step 504. When the valve is closed, an inert gas can be provided between the valve or the reactor's internal surface (e.g., the internal surface of the loading/unloading chamber) and a protective plate to protect the valve from chemicals used during substrate processing. Alternatively, the gas curtain can be provided continuously between the valve/internal surface and the protective plate or can be provided any time before the purge process. After the valve is closed, during step 506, the loading/unloading chamber, as well as the reaction chamber, can be exposed to a vacuum source (e.g., vacuum source 116) to obtain a desired pressure in the reactor and/or the loading/unloading chamber. The substrate can then be placed in the reaction chamber by moving the susceptor during step 508, and the reaction chamber can be optionally exposed to the same or a different vacuum source during step 510. During step 508, a seal or a substantial seal (e.g., a tortuous path) can be formed between the reaction chamber and the loading/unloading chamber so that relatively little gas flows between the chambers. Alternatively, a small space can be maintained between the reaction chamber and the loading/unloading chamber during a flow-type reaction step that can be performed in addition to or instead of the soaking step described below. In step 512, one or more precursor gases flow over the substrate surface for a period of time. Heat can be applied to one or more precursor sources and/or bubblers can be used to facilitate the provision of one or more precursors. A carrier gas can flow simultaneously with one or more precursor gases, can be mixed in the mixer 122 and/or carrier, and can be mixed with the precursor gas in the precursor source (e.g., sources 107, 108). According to some embodiments of the present disclosure, the carrier gas flows for only a portion of the time that the precursor gas is flowing, e.g., the latter half. In step 516, the flow of the precursor gas and any carrier gas is stopped for a soaking period (step 518). During the soak period, the reaction chamber may be non-isothermal, e.g., the susceptor may be at one temperature and the top surface of the reaction chamber may be at another temperature, changing the temperature within the reaction chamber as precursor, carrier, and/or purge gases are introduced into the reaction chamber. For example, the temperature of the top surface of the reaction chamber may be higher than the temperature of the susceptor, causing the substrate surface to receive heat from the top surface as the susceptor moves to the processing position. Similarly, the substrate may be cooled away from the top surface. The duration of the soak period (step 518) varies depending on the application and may range, for example, from about 0.2 to about 600, from about 1 to about 60, or from about 5 to about 30 seconds. After the soak period, the susceptor is lowered (step 520) so that unreacted precursors and/or reaction by-products may be purged from the reaction chamber, through the load/unload chamber, and toward the vacuum source. Once the susceptor is moved during step 520, the reaction chamber and/or the fill/unload chamber can continue to be exposed to a vacuum source during steps 506-520 to facilitate purging of the reaction chamber. For example, the fill/unload chamber can be maintained at a desired pressure during one or more of steps 506-518 or 520. Additionally or alternatively, the reaction chamber can be exposed to a vacuum source before moving the susceptor, which has the advantage of keeping the fill/unload chamber relatively clean. As shown, the method 500 can repeat steps 506-520 for the same (e.g., of a self-assembled monolayer) or different precursors (e.g., different precursors used in ALD deposition). To facilitate the purge step, one or more purge gases can be supplied to the reaction chamber and/or the fill/unload chamber. The substrate can then be removed by moving the susceptor to a fill/unload position and opening the valves in step 524.

The purge time during step 520 can be relatively short. By way of example, the purge time can range from about 0.1 to about 300, from about 1 to about 60, or from about 2 to about 10 seconds.

It may be desirable to clean parts of the system, such as the reaction chamber and/or the loading/unloading chamber. In these cases, the loading/unloading chamber will generally need to be cleaned less frequently than the reaction chamber, since any deposition reactants are likely to be highly diluted in the loading/unloading chamber and the residence time of the reaction is much lower. An optional exemplary cleaning compound includes NF3.

FIG. 6 shows a pressure diagram illustrating an example pressure 602 in a fill/unload chamber (e.g., fill/unload chamber 106), a pressure 604 in a reaction chamber (e.g., reaction chamber 104), and a pressure 606 in a precursor source container during a process. The illustrated process begins with the susceptor in the processing position. As shown, the pressure in the fill/unload chamber decreases at the beginning of the process and can continue to decrease as precursors flow until the pressure reaches a low value). The pressure can be maintained at or near a low value until the purge process begins, at which point the pressure increases in the fill/unload chamber. Meanwhile, the pressure in the reaction chamber can be initially low and increases as precursor and/or carrier gas are introduced into the reaction chamber. In the illustrated example, the carrier gas flow begins after the precursor flow begins. The pressure can then remain substantially constant in the reaction chamber during the soak period, and then the substrate is moved from the processing position to the purge position (e.g., as shown in FIG. 3). The pressure in the reaction chamber can be further reduced after the soaking period and by exposing the reaction chamber to a vacuum source before or during the step of moving the susceptor. Also, the pressure in the precursor source vessel can be initially high (e.g., as a result of heating the vessel) and can be lowered as the precursor gas is introduced into the reaction chamber. The pressure in the precursor source vessel can be increased again, for example, when the source precursor is shut off from the reaction chamber (e.g., at the beginning of the soaking period) and/or at the end of the soaking period.

As mentioned above, for some types of reactions, it may be desirable to have a relatively high partial pressure of one or more precursors and/or a high absolute pressure in the reaction chamber. One technique for obtaining a desired precursor partial pressure is to heat the precursor source to increase the evaporation rate of the precursor and increase the saturated vapor pressure of the precursor. Additionally or alternatively, an inert gas pad can be used to increase the pressure in the reaction chamber during the soak period. An exemplary inert gas pad is disclosed in U.S. Patent Application Serial No. 12/763,037, entitled "PRECURSOR DELIVERY SYSTEM," the contents of which are incorporated herein to the extent not inconsistent with this disclosure. While the use of a gas pad does not necessarily increase the dose of precursor in the reaction chamber, the gas pad can be used to increase the total pressure in the reaction, and thus the amount of gas surface impingement can be increased using a precursor gas pad.

Although exemplary embodiments of the present disclosure are described herein, it should be understood that the present disclosure is not limited thereto. For example, while the apparatus and methods are described in connection with various specific components, the present disclosure is not necessarily limited to these configurations. Various modifications, variations, and enhancements of the apparatus and methods described herein can be made without departing from the spirit and scope of the present disclosure.