Patent ID: 12247286

It will be appreciated 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 illustrated embodiments of the present disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Although certain embodiments and examples are disclosed below, it will be understood by those in the art that the invention extends beyond the specifically disclosed embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the invention disclosed should not be limited by the particular disclosed embodiments described below.

The present disclosure generally relates to cooling methods and apparatus for use with a precursor source vessel, and assemblies and reactor systems that include such apparatus and vessels. As described in more detail below, exemplary methods can be used to maintain a heating element at a desired temperature, and to facilitate rapid cooling of a vessel for accessibility during maintenance. In addition, the reactor systems, assemblies, and vessels can be used to generate a desired temperature profile within the vessel to provide a precursor to a reaction chamber.

Exemplary precursor source vessels, assemblies, reactor systems, and methods discussed herein can be used for a variety of applications. For example, the vessels, assemblies, and reactor systems can be used for chemical vapor deposition (CVD) and/or atomic layer deposition (ALD) processes.

CVD includes forming thin film of materials on substrates using reactant vapors (including “precursor gases”) of different reactant chemicals that are delivered to one or more substrates in a reaction chamber. In many cases, the reaction chamber includes only a single substrate supported on a substrate holder (such as a susceptor), with the substrate and substrate holder being maintained at a desired process temperature. In typical CVD processes, reactive reactant vapors react with one another to form thin films on the substrate, with the growth rate being related to the temperature and the amounts of reactant gases. In some cases, energy to drive the deposition process is supplied in part by plasma, e.g., by a remote or direct plasma process.

In some applications, the reactant gases are stored in gaseous form in a reactant source vessel. In such applications, the reactants are often gaseous at standard pressures and temperatures of around 1 atmosphere and room temperature. Examples of such gases include nitrogen, oxygen, hydrogen, and ammonia. However, in some cases, the vapors of source chemicals or precursors that are liquid or solid (e.g. hafnium chloride, hafnium oxide, zirconium dioxide, or the like) at standard pressure and temperature are used. For some solid substances (referred to herein as “solid source precursors”), the vapor pressure at room temperature is so low that the substances are typically heated and/or maintained at very low pressures to produce a sufficient amount of reactant vapor for the reaction process. Once vaporized, it is important that the vapor phase reactant is kept at or above the vaporizing temperature through the processing system so as to prevent undesirable condensation in the valves, filters, conduits, and other components associated while delivering the vapor phase reactants to the reaction chamber. Vapor phase reactants from such naturally solid or liquid substances may be useful for chemical reactions in a variety of applications.

ALD is another process for forming thin films on substrates. In many applications, ALD uses a solid and/or liquid source chemical as described above. ALD is a type of vapor deposition wherein a film is built up through, e.g., self-saturating reactions performed in cycles. A thickness of an ALD-deposited film can be determined by the number of ALD cycles performed. In an ALD process, gaseous reactants are supplied, alternatingly and/or repeatedly, to the substrate to form a thin film of material on the substrate. One reactant absorbs in a self-limiting process on the substrate. A different, subsequently pulsed reactant reacts with the adsorbed material to form a single molecular layer of the desired material. Decomposition may occur through mutual reaction between the adsorbed species and with an appropriately selected reactant, such as in a ligand exchange or a gettering reaction. In a theoretical ALD reaction, no more than a molecular monolayer forms per cycle. Thicker films are produced through repeated growth cycles until the target thickness is achieved.

In theoretical ALD reactions, mutually reactive reactants are kept separate in the vapor phase with intervening removal processes between substrate exposures to the different reactants. For example, in time-divided ALD processes, reactants are provided in pulses to a stationary substrate, typically separated by purging or pump down phases; in space-divided ALD processes, a substrate is moved through zones with different reactants; and in some processes, aspects of both space-divided and time-divided ALD can be combined. Variants or hybrid processes of ALD and CVD allow some amount of CVD-like reactions, either through selection of the deposition conditions outside the normal ALD parameter windows and/or through allowing some amount of overlap between mutually reactive reactants during exposure to the substrate.

In this disclosure, an assembly may include a solid or liquid precursor source vessel, a heating element, and a cooling apparatus. The heating element is in thermal communication with the source vessel, and the cooling apparatus is in thermal contact with the heating element.

The cooling apparatus can be cooled, in order to cool a surrounding environment. In some embodiments, the cooling apparatus comprises a cooling plate. In some embodiments, the cooling plate is the same shape or a similar shape as the heating element. For example, the cooling plate can be rectangular, circular, hexagonal octagonal, or any other shape.

FIGS.1and2illustrate a cooling apparatus100according to some embodiments. The cooling apparatus100comprises a cooling plate150. Cooling apparatus100has a top side160, as depicted inFIG.1, which thermally contacts the heating element. A bottom side170of cooling apparatus100, as depicted inFIG.2can include or be in thermal contact with one or more cooling lines110, which define a fluid path that runs across a portion of the bottom side170of cooling apparatus100. In some embodiments, the bottom side170of cooling apparatus100includes one or more recesses120for receiving cooling lines110. In some embodiments, cooling lines110run through the cooling plate150in a serpentine fluid path, where the fluid can run vertically and/or horizontally proximate a center portion of cooling apparatus100several times, as illustrated inFIG.2. Other fluid paths may be used (e.g. a zig-zag fluid path, a wave fluid path, etc.). In some embodiments, cooling lines110are secured to cooling plate150by clamps130. Other mechanical attachments may be used (e.g. bolts, screws, etc.).

In some embodiments, cooling lines110are configured to receive fluid from a fluid source. In some embodiments, the fluid enters cooling lines110through valves140. In some embodiments, the fluid is water. In some embodiments, the fluid is chilled water. In some embodiments, the fluid is air. In some embodiments, the fluid is ethylene glycol. The fluid can be maintained at a temperature that can cool cooling apparatus100to a temperature that draws thermal energy from heating element200. As thermal energy is (e.g., continuously) dissipated away from heating element200, heating element200can maintain a desired, e.g., steady, temperature without having to stop emitting heat. In some embodiments, cooling element100maintains heating element200at temperature that does not increase or decrease more than 5° C., 3° C., or 1.5° C., during the operation of reactor systems, assemblies, and vessels, e.g. during a CVD and/or ALD process.

With reference toFIG.5, in some embodiments, a control system500is used to control one or more of a flow rate of the fluid in cooling lines110and a temperature of the fluid in cooling lines110. The control system500can be configured to communicate with one or more sensors510configured to detect a running temperature of heating element200. When the temperature of heating element200increases to an upper threshold temperature, the flow rate of the fluid in cooling lines110can increase and/or the temperature of the fluid in cooling lines110can decrease in order to actively cool the heating element. When the temperature of heating element200decreases to a lower threshold temperature, the flow rate of the fluid in cooling lines110can decrease and/or the temperature of the fluid in cooling lines110can increase in order to reduce the function of cooling element100.

As discussed above, in some embodiments, cooling element100is of the same shape or a similar shape as heating element200. In some embodiments heating element200is a heating plate.

In some embodiments, cooling plate150comprises an element that is a good conductor of heat. In some embodiments, cooling plate150comprises aluminum, stainless steel, nickel, or hastelloy. In some embodiments, cooling lines110and clamps130comprise stainless steel, aluminum, nickel, or hastelloy. However, any suitable materials may be used for cooling plate150, cooling lines110, clamps130, and any other attachment means used in cooling apparatus100.

Cooling apparatus100may be designed to accommodate any source vessel300, illustrated inFIG.5. For example,FIGS.3and4illustrate a cooling apparatus100and a heating element200disposed on the top side of cooling apparatus100, which is configured for use with a different source vessel than that ofFIGS.1and2.

With reference again toFIG.5, a solid source delivery assembly according to an embodiment includes source vessel300, heating element200, and cooling apparatus100. In some embodiments, heating element200is disposed at the base of source vessel300. In other embodiments, heating element200may be additionally or alternatively disposed above the source vessel300. Heating element200may be disposed at any location surrounding source vessel300. In some embodiments, cooling apparatus100is in thermal contact with heating element200. In some embodiments, heating element200is a resistive heater, such as a heating plate.

An exemplary source vessel for use with the present invention is shown in greater detail inFIG.6. In some embodiments, source vessel300includes a base340, a filter frame320, a filter330, and a housing310. Filter330can have a porosity configured to restrict a passage (or transfer) of a chemical reactant through the filter330. Source vessel300may define a source vessel axis304. In some embodiments, base340is configured to hold a solid source chemical. Base340may comprise a substantially planar surface for holding the chemical reactant, but other shapes and variants are possible. In some embodiments, source vessel300defines an interior314, encompassing the space between the walls of housing310and between a ceiling of housing310and a floor of base340. In some embodiments, the interior314is configured to contain a chemical reactant such as a solid source chemical.

FIG.6should not be viewed as limiting the number of elements source vessel300can contain. For example, in addition to heating element200, the assembly typically also includes one or more separate heaters. In some embodiments, one or more of the separate heaters800can be disposed vertically adjacent or vertically proximate to source vessel300. In some embodiments, the one or more separate heaters are configured to heat source vessel300by conduction. In some embodiments, one or more valves many be heated conductively and/or radiantly. In some embodiments, one or more feed throughs810for receiving one or more heaters can be included in the walls and/or center (e.g. in interior314) of source vessel300to provide more direct heat to the chemical reactant.

In some embodiments, the precursor source vessel300can have a height: diameter aspect ratio in the range of about 1-4. In some embodiments, the source vessel occupies a shape approximating a cylinder, but other shapes are possible. As such, in some embodiments, housing310comprises, consists essentially of, or consists of a cylindrical shape. In some embodiments, the mass of the source vessel300(unfilled) in various embodiments described herein can range from about 1 kg to about 100 kg, or about 10 kg to about 50 kg. In some embodiments, the mass of the filled source vessel300can range from about 10 kg to about 180 kg, or about 35 kg to about 85 kg. Lower masses of vessels can allow for easier transportation, but higher masses can facilitate higher volume reactant and necessitate fewer refills.

Source vessel300is configured to operate at an operating temperature. For example, the operating temperature may be determined based on a desired subliming rate of the chemical precursor/reactant. In some embodiments, the operating temperature is in the range of about 20° C.-250° C. The selected operating temperature may depend upon the chemical to be vaporized. For example, the operating temperature may be about 160° C.-240° C., particularly about 170° C.-190° C. for HfCl4; about 170° C.-250° C., particularly about 180° C.-200° C. for ZrCl4; about 90° C.-110° C. for Al2Cl3; or about 90° C.-120° C. for SiI4. The skilled artisan will appreciate other temperatures may be selected for other source chemicals.

Source vessels are typically supplied with gas lines extending from the inlet and outlet, isolation valves on the lines, and fittings on the valves, the fittings being configured to connect to the gas flow lines of a reaction chamber. It is often desirable to provide a number of heaters for heating the various valves and gas flow lines between the source vessel and the reaction chamber, to prevent the source vapor from condensing and depositing on such components. Accordingly, the gas-conveying components between the source vessel and the reaction chamber are sometimes referred to as a “hot zone” in which the temperature is maintained above the vaporization/condensation/sublimation temperature of the reactant.

In some embodiments, the source vessel, e.g. within the housing310, is set to a target vacuum pressure. In some embodiments, the target vacuum pressure is in the range of about a vacuum pressure to 760 Torr, or about 100 and 2000 Torr. In some embodiments, the target vacuum pressure is between about 3 Torr and 350 Torr. In some embodiments, the target vacuum pressure is between about 50 and 250 Torr. In preferred embodiments, the vacuum pressure is between 5 and 50 Torr. In some embodiments, the vacuum pressure is 25 Torr. The vacuum pressure generates a uniform temperature profile within the source vessel.

As illustrated inFIG.5, as cooling apparatus100continuously draws thermal energy from heating element200, a heat gradient is formed. The gradient is cooler at the base of source vessel300, where the precursor source is predisposed, and gradually gets hotter at the ceiling of vessel300. This controlled temperature gradient prevents or can mitigate hot spots, cold spots, and undesired condensation within the vessel, and can keep the precursor source at a cooler temperature than the surroundings within and exterior to vessel300, which, in turn, can prevent or mitigate undesired decomposition or degradation of the precursor. In other embodiments, where heating element and cooling apparatus are disposed at other locations surrounding the source vessel, the temperature gradient is cooler at the location of the heating element and cooling apparatus and gradually gets hotter at the opposite end of the vessel.

As illustrated inFIG.7, the assembly may be used in a reactor system700. The system700may comprise a precursor source vessel300, a heating element200, and a cooling apparatus100, as well as a reactor400. System700can also include a controller, such as controller500described above. The precursor is fed from the vessel300to the reactor400through one or more gas lines600.

In some embodiments, a method is provided for controlling the temperature of an interior of a source vessel, comprising heating the source vessel with a heating element, and cooling the heating element with a cooling apparatus. The heating element can continually provide heat (e.g., not power off) to the interior of the source vessel in order to maintain a desired operating temperature of the source vessel—e.g., a temperature between about 90° C. and about 250° C., or between about 110° C. and about 210° C. Generally, an operating temperature is greater than the sublimation temperature of the precursor and less than the decomposition temperature of the precursor. The cooling apparatus, as described above, can be used to actively cool the heating element in order to maintain the desired operating temperature of the heating element and/or vessel and/or precursor within the vessel and to provide a desired temperature gradient within precursor source vessel300.

In some embodiments, a method is provided for rapidly reducing the temperature of the interior of the precursor source vessel by powering off the heating element, and cooling the heating element using the cooling apparatus.

In this disclosure, any two numbers of a variable can constitute a workable range of the variable, and any ranges indicated may include or exclude the endpoints. Additionally, any values of variables indicated (regardless of whether they are indicated with “about” or not) may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments. Further, in this disclosure, the terms “including,” “constituted by” and “having” refer independently to “typically or broadly comprising,” “comprising,” “consisting essentially of” or “consisting of” in some embodiments. In this disclosure, any defined meanings do not necessarily exclude ordinary and customary meanings in some embodiments.

In this disclosure, “continuously” can refer to one or more of without breaking a vacuum, without interruption as a timeline, without any material intervening step, without changing treatment conditions, immediately thereafter, as a next step, or without an intervening discrete physical or chemical structure between two structures other than the two structures in some embodiments.

The example embodiments of the disclosure described above do not limit the scope of the invention, since these embodiments are merely examples of the embodiments of the invention. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the disclosure, in addition to the embodiments shown and described herein, such as alternative useful combinations of the elements described, may become apparent to those skilled in the art from the description. Such modifications and embodiments are also intended to fall within the scope of the appended claims.