Patent Application
20100075037
Deposition Systems, atomic layer deposition (ALD) systems, chemical vapor deposition (CVD) systems, deposition methods, ALD methods and CVD methods.
Integrated circuit fabrication frequently comprises deposition of materials across a semiconductor substrate. A semiconductor substrate may be, for example, a monocrystalline silicon wafer, either alone, or in combination with one or more other materials.
The deposited materials may be conductive, insulative, or semiconductive. The deposited materials may be incorporated into any of numerous structures associated with an integrated circuit, including, for example, electrical components, insulative material electrically isolating electrical components from one another, and wiring electrically connecting electrical components to one another.
ALD and CVD are two commonly utilized deposition methods. For ALD processing, reactive materials are sequentially provided in a reaction chamber at substantially non-overlapping times relative to one another to form a monolayer over a substrate. Multiple monolayers may be stacked to form a deposit to a desired thickness. ALD reactions are controlled so that a deposited material is formed along a substrate surface, rather than throughout a reaction chamber. In contrast, CVD processing comprises simultaneous provision of multiple reactive materials within a reaction chamber so that deposited material is formed throughout a reaction chamber, and then settles on a substrate within the chamber to form a deposit across the substrate.
Some reactive materials utilized for ALD and CVD are much more expensive than others. In some embodiments of this disclosure, the expensive reactive materials utilized for ALD and CVD may be categorized as being precursors, and the less expensive reactive materials may be categorized as being reactants. Precursors may contain metals; and may be complex molecules, such as metallorganic compositions. Reactants, in contrast, may be simple molecules, with common reactants being oxygen (O2), ozone, ammonia and chlorine (Cl2).
The precursors may be more valuable than their constituent parts. For instance, precursors comprising precious metals (e.g., gold, platinum, etc.) are often several times more expensive than the precious metals themselves. Also, precursors of relatively inexpensive materials (for instance, non-precious metals, like copper) may still be themselves expensive, particularly if complicated and/or low-yield processes are utilized in forming the precursors.
It would be desirable to develop systems and methods which reduce expenses associated with precursor materials.
One aspect common to both ALD and CVD is that some of the precursor material that is introduced into a reaction chamber will remain unreacted, and thus will be exhausted from the chamber in the same compositional form in which it entered the chamber. Some embodiments include methods and systems suitable for reclaiming the unreacted precursor material so that it may be reintroduced into a deposition process. Example embodiments are described with reference to
Referring to
A pump 16 is provided downstream of the reaction chamber and utilized to pull various materials through the system. Other components (not shown) may be provided in addition to, or alternatively to, pump 16 for assisting the flow of materials through the system. The materials flowing into and through the chamber may be considered to be flowed along a flow path that extends to the chamber along a line 18, through the chamber as illustrated by arrows 20, and then from the chamber along a line 22. The flow through the chamber may be continuous, or may comprise loading the chamber with a pulse of material, holding the material within the chamber for a duration of time, and then exhausting the material from the chamber with a purge cycle. If ALD is utilized, two or more sequential pulse/purge cycles may be utilized to form a monolayer of material.
The lines 18 and 22 may correspond to pipes or other suitable conduits for carrying materials to and from the reaction chamber. In addition to the lines 18 and 22, the system also includes lines 24, 26 and 28.
A valve 30 is shown along line 28, valves 32 and 34 are shown along line 24, and valves 36 and 38 are shown along line 26. The valves may be utilized to regulate flow of material along the flow path.
A pair of precursor traps 40 and 42 are shown along the lines 24 and 26, respectively. The precursor traps are configured to trap precursor under a first condition, and to release the trapped precursor under a second condition. For instance, the precursor traps may be cold traps and accordingly may be configured to trap precursor under a relatively low-temperature condition, and to release precursor under a relatively high-temperature condition. The terms “relatively low temperature” and “relatively high temperature” are utilized for comparison to one another so that the “relatively low-temperature” is a lower temperature than the “relatively high temperature”.
The specific temperatures may be any temperatures suitable for trapping and releasing precursors utilized during deposition with system 10. For instance, in some embodiments the platinum precursor (CH3)3(CH3C5H4)Pt may be utilized. Such precursor may be trapped at a temperature less than about 0° C., such as, for example, a temperature of less than or equal to about −10° C. for ALD applications, and possibly less than or equal to about −20° C. for CVD applications; and such precursor may be released from the trap at a temperature greater than about 25° C., such as, for example, a temperature greater than about 40° C. In some embodiments, the trapping temperature may be low enough so that oxygen-sensitive material do not oxidize when exposed to air in a trapping line. For instance, if Rh is to be trapped, the trap may be at a temperature of less than or equal to −40° C. (where the term “−40° C.” means 40 degrees below 0° C.) during the trapping of the Rh, and during the retention of the Rh on the trap, to avoid oxidation of the Rh by oxygen that may be passed through the trap. The maintaining of a trapping temperature at a level cold enough to preclude oxidation of an oxygen-sensitive precursor (which may be an air sensitive precursor in some applications) may be considered to be one example of embodiments in which the trapping temperature is kept cold enough to preclude undesired side reactions from occurring relative to trapped materials. Such embodiments may be particularly suitable when trapping is utilized relative to CVD applications, since multiple reactive materials will be passed through traps while the traps are being utilized to retain desired precursors.
Coils 44 are diagrammatically illustrated adjacent the traps 40 and 42. The coils represent heating/cooling units that may be provided proximate the traps to control trapping and release of precursor from the traps in embodiments in which the traps may be thermally controlled (for instance, in embodiments in which the traps are cold traps).
The traps 40 and 42 may be considered to be in fluid communication with reaction chamber 14, and may be considered to be connected in parallel relative to one another along the flow path of material within system 10.
In operation, one of the traps 40 and 42 may be utilized as a source of precursor to chamber 14, while the other is utilized for trapping precursor present in the exhaust from chamber 14. In the shown embodiment, a carrier gas source 46 is illustrated to be in fluid communication with traps 40 and 42 through lines 48 and 50, respectively. Valves 52 and 54 are shown along lines 48 and 50 for controlling flow of the carrier gas to the traps 40 and 42. The carrier gas can assist in removing precursor from the traps. The carrier gas may be a composition inert relative to reaction with the precursor material under the conditions in which the precursor is released from the traps, and may, for example, comprise one or more of N2, argon and helium.
The traps 40 and 42 may be alternately cycled between trapping and releasing modes relative to one another so that each of the traps is ultimately utilized as a source of precursor upstream of the reaction chamber, and is utilized for trapping unreacted precursor downstream of the reaction chamber.
Although two precursor traps are illustrated in the shown embodiment, in other embodiments there may be more than two precursor traps. For instance, multiple different precursors may be flowed through reaction chamber 14 during a deposition process, and it may be desired to trap the different precursors on separate traps relative to one another. In some embodiments, two traps arranged in parallel with one another may be utilized for trapping and releasing each of the different precursors. For instance, if a deposition process forms a mixed-metal material, such as platinum-ruthenium-oxide, each metal may be deposited from a separate precursor. It may be desired to trap the different metal-containing precursors separately from one another. The traps utilized for trapping different precursor materials may be identical to one another and utilized under different conditions from one another, or may be of different types relative to one another.
In embodiments in which reactant is utilized in addition to precursor, it may be desired to trap the precursor (in other words, to trap the expensive starting material), and to not trap the reactant (in other words, to not trap the cheap starting material). If the deposition process is an ALD process, the reactant may be exhausted from the system by a bypass similar to that discussed below with reference to
The system 10 of
The system 10 of
System 60 includes a reaction chamber 62, a pair of reservoirs 64 and 66 for retaining starting materials, and a pump 68 configured to be utilized for pulling various materials through the system. Other components (not shown) may be provided in addition to, or alternatively to, pump 68 for assisting the flow of materials through the system. The materials flowing into and through the chamber may be considered to be flowed along a flow path that extends to the chamber along a line 65, through the chamber as illustrated by arrows 70, and then from the chamber along a line 67. The line 67 splits into two alternative flow paths 72 and 74. The flow path 72 extends through a precursor trap 76, and the flow path 74 bypasses the precursor trap.
A plurality of valves 80, 82, 84, 86 and 88 are provided to enable regulation of the flow of various materials along the various flow paths extending to and from the reaction chamber. Other valves may be utilized in addition to, or alternatively to, the shown valves.
A flow control structure 90 is provided along flow path 74 and configured to preclude back-flow along the flow path. Flow control structure 90 may be any suitable structure, and may, for example, correspond to a turbopump, cryopump, destruct unit (i.e., a unit which breaks down one or more chemical compositions), or check-valve.
In operation, a precursor material may be provided in reservoir 64 and a reactant may be provided in reservoir 66. Valves 80 and 82 are utilized to control flow of the reactant and precursor so that only one of them is introduced into chamber 62 at any given time. Accordingly, the two different materials (specifically, the precursor and the reactant) are in chamber 62 at different and substantially non-overlapping times relative to one another. This may occur by removing substantially all of one of the materials from within the reaction chamber prior to introducing the other of the materials into the chamber. The term “substantially all” indicates that an amount of material within the reaction chamber is reduced to a level where gas phase reactions with subsequent materials do not degrade the properties of a deposit formed on a substrate from the material. Such can, in some embodiments, indicate that all of a first material is removed from the reaction chamber prior to introducing a second material, or that at least all measurable amounts of the first material are removed from the reaction chamber prior to introducing the second material into the chamber.
At times that precursor flows out of chamber 62, the exhaust from the chamber may be flowed along the flow path 72. Accordingly, the precursor may be trapped on the precursor trap 76 whereupon it may be subsequently reclaimed. The precursor is likely to flow out of chamber 62 during a flow of material through the chamber to fill the chamber with the precursor material, and during a flush of the chamber to remove precursor material from within the chamber.
At times when precursor is not being flowed out of the chamber, but instead materials other than precursor are flowed out of the chamber, the exhaust from the chamber may be flowed along bypass path 74. An advantage of flowing reactant along the bypass path 74 is that such may preclude undesired interaction of the reactant with precursor retained by trap 76, which could degrade the quality of the retained precursor.
Utilization of the flow control structure 90 along the bypass path 74 may advantageously preclude backflow of reactant into chamber 62. If reactant back flows into chamber 62, it may remain in the chamber when precursor is subsequently introduced to the chamber, which can lead to undesired CVD reactions between the precursor and reactant. Even if the reaction chamber is carefully monitored to ensure that substantially all reactant has been removed from the chamber prior to introduction of precursor, the backflow of reactant may lead to undesired consequences. Specifically, the backflow of reactant may lead to a much longer evacuation time than may be accomplished utilizing the shown embodiment in which a control structure 90 is provided to preclude backflow. A prior art ALD system is described in U.S. Patent Publication No. 2005/0016453. Such system lacks a flow control structure analogous to structure 90, and thus the system 60 shown and described with reference to
Valve 86 may advantageously allow trap 76 to be isolated from a pumping line, which may improve precursor recovery rates relative to systems that leave the trap under dynamic vacuum.
An example pulse/purge sequence that may be utilized with the system 60 of
After the precursor has been provided within the reaction chamber and given sufficient time to react with a surface of a substrate, a purge is utilized to remove the precursor from the chamber. Such purge is illustrated by the path 102 in
The exhaust from chamber 62 (
After precursor has been purged from the chamber, reactant is introduced into the chamber with a pulse as indicated by path 104 of
After the pulse of reactant has been provided within the reaction chamber, a purge is utilized to remove the reactant from the chamber. Such purge is illustrated by the path 106 of
The exhaust from chamber 62 (
The pulse/purge sequence of
It is noted that the could be pump cycles (no gas flow) after the purge cycles of
The system of
System 120 includes a reaction chamber 122, a plurality of reservoirs 123, 124 and 126 for retaining starting materials, and a pump 128 configured to be utilized for pulling various materials through the system. Other components (not shown) may be provided in addition to, or alternatively to, pump 128 for assisting the flow of materials through the system. The materials flowing into and through the chamber may be considered to be flowed along a flow path that extends to the chamber along a line 125, through the chamber as illustrated by arrows 130, and then from the chamber along a line 127. The line 127 splits into two alternative flow paths 132 and 134. The flow path 132 extends through a pair of precursor traps 136 and 138 that are arranged in series with one another, and the flow path 134 bypasses the precursor traps.
The system 120 may be configured to utilize multiple different precursors simultaneously in a CVD process, and the traps 136 and 138 may be configured to separately trap different precursors relative to one another. For instance, if the CVD process utilizes a mixture of metal-containing precursors, one of the traps 136 and 138 may be configured to trap one type of metal-containing precursor, and the other of the traps may be configured to trap a different type of metal-containing precursor.
In some embodiments, the traps 136 and 138 may both be cold traps, with one of the traps operated at a different temperature than the other so that each trap selectively retains a particular precursor. For instance, the upstream trap 136 may be utilized at a temperature such that one precursor is retained, and another flows through; and the downstream trap 138 may be utilized at a temperature low enough to trap the precursor that flowed through the upstream trap.
In some embodiments, traps 136 and 138 may be different types of traps from one another. For instance, one may be a cold trap and the other may be a solvent-based trap.
Although two traps are shown, in other embodiments only a single trap may be utilized, and in yet other embodiments more than two traps may be utilized.
A plurality of valves 140, 141, 142, 144, 146 and 148 are provided to enable regulation of the flow of various materials along the various flow paths extending to and from the reaction chamber. Other valves may be utilized in addition to, or alternatively to, the shown valves.
In operation, precursor materials may be provided in reservoirs 123 and 124, and a reactant may be provided in reservoir 126. Valves 140, 141 and 142 are utilized to control flow of the reactant and precursors so that all them are in chamber 122 at the same time. The reactant and precursors react together form a deposit across a substrate (not shown) which is present within the chamber. The substrate may be, for example, a semiconductor wafer, and the deposit may be, for example, a mixed metal oxide (i.e., hafnium-aluminum oxide).
If exhaust from the chamber contains unreacted precursors, the exhaust may be flowed along the flow path 132 so that the unreacted precursors are trapped on the precursor traps 136 and 138. The unreacted precursors may then be subsequently reclaimed from the traps.
The traps may be operated under conditions so that trapped precursor does not react with reactant flowing past the precursor. Specifically, the exhaust from the CVD process may be a mixture that comprises, for example, reactant, reaction by-products, partially reacted precursor, and unreacted precursor. It may be desired for the traps to specifically trap unreacted precursor, and to then retain such unreacted precursor under conditions that avoid degradation of the precursor. Such conditions may be thermal conditions of a cold trap that are sufficiently cold to preclude reaction of the unreacted precursor with other materials in the exhaust from the CVD process and/or to preclude other mechanisms by which the unreacted precursor may be degraded on the trap. For instance, one of the trapped precursors may correspond to (CH3)3(CH3C5H4)Pt, the reactant may include O2, and the (CH3)3(CH3C5H4)Pt may be retained on the trap at a temperature of less than or equal to about −20° C. The trapping temperature utilized during CVD applications may be lower than that of the above-discussed ALD applications both to prevent undesired reaction of trapped precursor with other materials flowing past the trapped precursor, and/or to keep the trapped precursor from being swept off of the trap by the various materials flowing past the trapped precursor.
The system 120 may be subjected to cleaning or other processes in which materials are flowed to the chamber, and in which it is desired that the materials not be flowed across the precursor traps. At such times, the exhaust from the chamber may be flowed along bypass path 134.
The precursors trapped on traps 136 and 138 may be removed from the traps by any suitable methods. For instance, if one or both of the traps is a cold trap, then coils analogous to the coils 44 of
The embodiment of
Numerous advantages may be provided by the trapping of precursors, including saving of costs; reducing wastes; and providing for a mechanism of removing of unreacted precursor which may assist in evacuation of a system, and in some embodiments may eliminate utilization of a turbo pump. Among the precursors that may be trapped are precursors comprises metals (either precious metals or non-precious metals); and precursors that may non-expensive, but that are utilized in large quantity, such as, for example, tetraethylorthosilicate.
In compliance with the statute, the subject matter disclosed herein has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the claims are not limited to the specific features shown and described, since the means herein disclosed comprise example embodiments. The claims are thus to be afforded full scope as literally worded, and to be appropriately interpreted in accordance with the doctrine of equivalents.
