Patent Application
20110312148
Embodiments of the present invention generally relate to semiconductor devices and methods of fabrication thereof.
As the feature size of dynamic random access memory (DRAM) devices is decreased, a higher capacitance density is required. Unfortunately, conventional capacitor designs, such as those having titanium nitride (TiN)/high-k dielectric material/titanium nitride (TiN) (TIT) structure cannot meet the requirement of effective oxide thickness (EOT) for the next generation (e.g., <45 nm) due to high leakage caused by the low work function of the metal electrode (TiN).
Ruthenium (Ru) is a candidate element for inclusion in the electrodes of a capacitor to achieve the EOT requirement of about 5 angstroms due to its high work function and low reactivity with high-k materials. For example, such high-k dielectric materials may have a dielectric constant of about 100 or more.
Unfortunately, the deposition of Ru is challenging. For example, the deposition may include such limitations as low deposition rate, poor step coverage, high resistivity, and poor adhesion to oxides. Although some Ru deposition techniques have been reported that satisfy some of these requirements, no satisfactory process has yet been developed that satisfies all of the requirements. For example, chemical vapor deposition (CVD) with triruthenium dodecacarbonyl (Ru3(CO)12) has shown good layer resistivity, but the adhesion, deposition rate, and step coverage were all poor and thus inadequate for device applications
Accordingly, the inventors have provided improved methods for depositing ruthenium-containing films.
Methods for depositing ruthenium-containing films are provided herein. In some embodiments a method of depositing a ruthenium film may include depositing a ruthenium film on a substrate via a chemical vapor deposition process using a metalorganic ruthenium precursor, the deposited ruthenium film having carbon incorporated therein; and exposing the deposited ruthenium film to oxygen to remove at least some of the carbon from the ruthenium film. In some embodiments, the deposition of the ruthenium film and the subsequent exposure to oxygen may be repeated. In some embodiments, the oxygen-exposed ruthenium film may be thermally annealed.
In some embodiments, a method of depositing a ruthenium-containing layer on a substrate may include depositing a ruthenium-containing film on a substrate using a ruthenium-containing precursor, the deposited ruthenium-containing film having carbon incorporated therein; and exposing the deposited ruthenium-containing layer to an oxygen-containing gas to remove at least some of the carbon from the deposited ruthenium-containing film. In some embodiments, the oxygen-containing gas exposed ruthenium-containing film may be annealed in a hydrogen-containing gas to remove at least some oxygen from the ruthenium-containing film. In some embodiments, the deposition, exposure, and annealing may be repeated to deposit the ruthenium-containing film to a desired thickness.
In some embodiments, an oxide layer may be deposited atop the ruthenium-containing film and a second ruthenium-containing film may be deposited atop the oxide layer. In some embodiments, the second ruthenium-containing film may be deposited and processed by a substantially similar method as the ruthenium-containing film. In some embodiments, the ruthenium-containing film, the second ruthenium-containing film, and the oxide layer form a capacitor, for example, that may be coupled to one of a source or drain of a transistor device via the substrate.
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.
Methods for depositing ruthenium-containing films are disclosed herein. The inventive methods may advantageously allow for a ruthenium-containing film to be deposited having any or all of adequate resistivity, adhesion, deposition rate, or step coverage for device applications. Exemplary device applications may include capacitors having one or more ruthenium-containing film formed by the inventive methods disclosed herein. In some embodiments, the exemplary capacitors may be part of a larger device such as a dynamic random access memory (DRAM) cell.
The method 100 begins at 102 where a first ruthenium-containing film 202 may be deposited on a substrate 200 as illustrated in
Chemical precursors that may be used to deposit the first ruthenium-containing film 202 as described above may include metalorganic precursors. In some embodiments, the precursor may include: dimethyl-butadienyl-ruthenium, cyclohexadine-Ru-tricarbonyl (C6H8—Ru(CO)3), butadiene-Ru-tricarbonyl (C4H6—Ru(CO)3), dimethylbutadiene-Ru-tricarbonyl ((CH3)2—C4H4—Ru—CO)3), or modified dienes with ruthenium tricarbonyl (Ru(CO)3). Each precursor may have a liquid form and may be provided in a bubbler through which a carrier gas is flowed to carry the precursor into the process chamber. The carrier gas may be any compatible inert gas, such as nitrogen or a noble gas, such as argon, helium, or the like. The carrier gas may be provided at about 100 to about 1000 sccm, or from about 300 to about 700 sccm. The quantity of the precursor delivered to the chamber may range from about 1 to about 50 sccm.
During deposition of the first ruthenium-containing film 202 at 102, the temperature inside the chamber, or of the substrate, may range from about 150 to about 300 degrees Celsius, or from about 200 to about 250 degrees Celsius. The pressure in the chamber may range from about 3 to about 10 Torr, or from about 1 to about 30 Torr. The deposition process at 102 may be carried out for a first period of time suitable to provide a desired thickness of the first ruthenium-containing film 202 prior to proceeding to process the first ruthenium-containing film 202 as discussed below to reduce carbon content at 104 or reduce oxygen content at 106. In some embodiments, the first ruthenium-containing film 202 may be deposited to a desired thickness ranging from about 5 to about 50 Angstroms at 102. Alternatively, as discussed below at 108, the first ruthenium-containing film 202 may be deposited to a desired thickness by sequentially repeating the method 100, for example, repeating steps 102 and 104, or repeating steps 102, 104 and 106 until a desired thickness of the first ruthenium-containing film 202 is achieved.
The substrate may comprise any suitable material, such as a semiconducting material and/or combinations of semiconducting materials for forming a semiconductor structure. For example, the substrate may comprise one or more silicon-containing materials such as crystalline silicon (e.g., Si<100> or Si<111>), silicon oxide (SiO2), strained silicon, doped or undoped polysilicon, doped or undoped silicon wafers, patterned or non-patterned wafers, doped silicon, and/or other materials, such as silicon nitride (Si3N4), strontium titanium oxide (SrTiO3), titanium (Ti), titanium nitride (TiN) or combinations thereof. In some embodiments, the upper surface of the substrate includes an oxide or a nitride. For example, the oxide or nitride may serve as a barrier layer or the like to prevent one or more materials from the deposition of the first ruthenium-containing film 202 at 102 or subsequent processing steps of the method 100 from penetrating deeper into the substrate 200. For example, in some embodiments, the oxide or nitride may serve as a barrier layer to oxidation, such as from an oxygen-containing gas used to reduce carbon content in the first ruthenium-containing film 202 as discussed below at 104.
At 104, the deposited ruthenium-containing film 202 may be exposed to an oxygen-containing gas to remove at least some carbon (C) from the deposited first ruthenium-containing film 202 as depicted in
The deposited ruthenium-containing film 202 may be exposed to the oxygen-containing gas in the same CVD chamber as used for depositing the ruthenium-containing film 202, or alternatively, in a different chamber configured for providing the oxygen-containing gas, such as an oxidation chamber or the like. The oxygen-containing gas may be provided in a range of about 500 to about 1000 sccm. The ruthenium-containing film 202 may be exposed to the oxygen-containing gas for a second period of time. The duration of the second period of time may be dependent upon the thickness of the ruthenium-containing film 202 deposited at 102. In some embodiments, the second period of time may range from about 5 to about 60 seconds. The ruthenium-containing film 202 may be exposed to the oxygen-containing gas at the same pressure and temperature as disclosed above at 102 for depositing the ruthenium-containing film 202. The oxygen-containing gas may include one or more of oxygen (O2), water vapor (H2O), or hydrogen peroxide (H2O2). In some embodiments, the oxygen-containing gas may be O2.
The exposure to the oxygen-containing gas at 104 may result in incorporation of oxygen into the deposited ruthenium-containing film 202 in addition to the removal of carbon from the layer 202. The oxygen content in the deposited ruthenium-containing film 202 after exposure to the oxygen-containing gas at 104 may range from about 1 to about 15 atomic percent, or in some embodiments, about 5 to 10 atomic percent. In some embodiments, the oxygen content may be at least about 8 atomic percent. The removal of carbon from and/or incorporation of oxygen into the deposited ruthenium-containing film 202 may be most effective when the ruthenium-containing film 202 is thin. For example, and in some embodiments, “thin” may include a layer thickness ranging from about 10 to about 50 Angstroms.
Further, the oxygen content can be changed depending on the length of exposure time (e.g., the second period of time) to the oxygen-containing gas. For example, if lower resistivity and higher throughput is desired, the second period of time may be between about 5 to about 60 seconds. The oxygen content in the deposited ruthenium-containing film 202 may advantageously contributes to the adhesion of the ruthenium-containing film 202 on a surface of the substrate 202 surface of the substrate, for example, comprised of at least one of SiO2 or Si3N4. In some embodiments, at completion of 104, the resistively of deposited ruthenium-containing film 202 has been reduced to about 60 μOhm-cm or less.
Optionally, at 106 and depicted in
The hydrogen-containing gas may include one or more of hydrogen (H2), HCOOH, a hydrogen (H) radical, or a hydrogen (H2) plasma. In some embodiments, the hydrogen-containing gas may be H2. The removal of oxygen from the ruthenium-containing film 202 at 106 may further improve resistivity in the layer. For example, in some embodiments, after removing the oxygen, the resistivity of the ruthenium-containing film 202 may be further reduced to about 30 μOhm-cm or less.
As discussed above, the method 100 may be performed in any of several combinations of the processes discussed above. For example, the layer 202 may be deposited to the desired thickness at 102, and then exposed to the oxygen-containing gas, and then, optionally, exposed to the hydrogen-containing gas at 106. Alternatively, at 108, one or more processes at 102, 104, and 106 may be repeated to form the layer 202 to the desired thickness. For example, if the desired thickness is substantially thicker than that which is sufficient to effectively remove carbon at 104 and/or remove oxygen at 106, then an iterative deposition process may be most effective. For example, the iterative process at 108 may include repeating 102, 104, and optional 106 in the same order and for the same periods of time to achieve the same carbon content and/or oxygen content at each iteration. Alternatively, 102, 104, and 106 may be repeated in any suitable order to tailor the layer 202 to a desired thickness and/or scaling of carbon content and/or oxygen content. For example, it may be more desirable to have higher oxygen content proximate the surface of substrate 200 for improved adhesion and less at a terminal surface of the layer 202 for a desired resistivity. Other combinations which tailor properties of the layer 202, such as adhesion, resistivity, crystallinity, step coverage, deposition rate or the like between the surface of the substrate 200 and the terminal surface of the layer 202 may be utilized. For example, the carbon content and/or oxygen content can be graded in any suitable manner between the surfaces of the layer 202 to achieve a desired property.
Thus, method 100 may provide a ruthenium-containing film 202 comprising ruthenium, carbon and oxygen. For example, in some embodiments, the ruthenium-containing film may be predominantly ruthenium oxide (RuO2). Further, the ruthenium-containing film may include at least some carbon to the extent that carbon provides desirable layer properties as discussed above. Alternatively, in some embodiments, the ruthenium-containing film 202 may have substantially all carbon removed at 104 and comprise substantially ruthenium and oxygen. In some embodiments, upon completion of method 100, the ruthenium-containing film may have a high deposition rate (e.g., >about 60 Angstroms/min), low resistivity (e.g., <about 60 μOhm-cm, or in some embodiments, such as after annealing, <about 40 μOhm-cm), good step coverage (e.g., about 95% or greater), and good adhesion on surfaces includes at least one of oxides or nitrides.
The methods discussed above may be utilized to form a device, for example, such as a pedestal or crown capacitor which may be coupled to one or a source or drain of a transistor to form a DRAM cell. Exemplary capacitor devices are illustrated in
For example,
The method 300 begins at 302 by depositing a first ruthenium-containing film 402 on a substrate 400. The first ruthenium-containing film 402 may be substantially similar to the first ruthenium-containing film 202 and formed by any embodiments of the method 100 discussed above. As illustrated in
The substrate 400 may include one or more layers. For example, as illustrated in
The first layer 406 may include a conducting or semiconducting material, or alternatively, may be a dielectric material. For example, and in some embodiments, the first layer 406 may be formed from a semiconducting material, such as silicon (Si) and having a doped region 416 (shown by dotted lines in
At 304, an oxide layer 418 is formed atop the first ruthenium-containing film 402. For example, the oxide layer 418 may be utilized as a dielectric material between the electrodes of a capacitor device, where the electrodes may be the first ruthenium-containing film 402 and a second ruthenium-containing film 420 discussed below. The oxide layer 418 may include one or more of strontium titanium oxide (SrTiO3), a multi-layer oxide layer such as ZAZ (ZrO2/AL2O3/ZrO2), or the like. In some embodiments, the oxide layer 418 may be SrTiO3. The oxide layer 418 may have a thickness ranging from about 10 to about 100 angstroms. In some embodiments, the oxide layer thickness is about 30 to about 50 angstroms.
The oxide layer 418 may be deposited by any suitable method know in the art. For example, the oxide layer 418 may be deposited by thermal oxidation, CVD, ALD, PVD, or the like. Similar to embodiments discussed above for method 100, the oxide layer 418 may be formed in the same CVD process chamber used to form the first ruthenium-containing film 402, or alternatively, a second process chamber configured for an oxidation process may be used.
At 306, the second ruthenium-containing film 420 may be deposited atop the oxide layer 418 as illustrated in
The first and second ruthenium-containing films 402, 420 and the oxide layer 418 may be used to for a device such as a capacitor 422 illustrated in
Thus, methods for depositing ruthenium-containing films have been disclosed herein. The inventive methods may advantageously allow for a ruthenium-containing film to be deposited having any or all of adequate resistivity, adhesion, deposition rate, or step coverage for device applications. Exemplary device applications may include capacitors having one or more ruthenium-containing films formed by the inventive methods disclosed herein. In some embodiments, the exemplary capacitors may be part of a larger device such as a dynamic random access memory (DRAM) cell.
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.
This application claims benefit of U.S. provisional patent application Ser. No. 61/356,391, filed Jun. 18, 2011, which is herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61356391 | Jun 2010 | US |
