The subject matter disclosed herein relates to etching of various films used in the semiconductor and allied industries. More specifically, the disclosed subject matter relates to removing tin oxide films from plasma process chambers and other surfaces.
As is known to a person of ordinary skill in the art, tin oxide (SnO2) films are used for a variety of applications including, for example, extreme ultraviolet (EUV) hard masks, patterning spacers and mandrels for double and quad patterning, gap-fill metal oxides, hard masks, and etch stop layers. Consequently, tin oxide films are deposited on various substrate types in a process chamber via, for example, capacitively-coupled plasma (CCP) techniques. For tin oxide to be able to serve in high-volume manufacturing (HVM), the process chamber should periodically be cleaned of the as-deposited tin oxide film, leaving little to no tin oxide residue on walls and other surfaces within the process chamber. As is known to a person of ordinary skill in the art, tin oxide residues can cause contamination and defects on fabricated devices. For example, if the tin oxide film is not etched or otherwise cleaned or removed from the process chamber, the unremoved tin oxide can result in defects on a substrate as a result of the tin oxide film peeling off chamber components (e.g., due to poor adhesion as a result of buildup of in-film stress).
Typically, metal oxide films, such as tin oxide, may be etched with various chemistries known in the art such as, for example, hydrogen (H2), methane (CH4), chlorine (Cl2), hydrochloric acid (HCl), bromide (Br), hydrobromic acid (HBr), boron trichloride (BCl3), hydrogen iodide (HI), and iodine (I2). Many contemporaneous process chambers comprise aluminum (Al) or aluminum-alloy components. Most of the above-listed chemistries (with the exception of hydrogen and methane) cannot be used in process chambers (e.g., CCP chambers) having aluminum components as each of the listed chemistries attacks Al, thus forming one or more volatile aluminum-halide byproducts (e.g., chloride, bromide, or iodide). The volatile byproducts can produce severe metal contamination on substrates (e.g., silicon wafers) and lead to chamber degradation. Therefore, unless properly removed, the tin oxide could produce a completely non-manufacturable solution. Out of the above-listed halide chemistries, chlorine chemistry would be the most favorable for etching tin oxide, because of the high vapor pressure of a resulting tin tetrachloride (SnCl4). However, using chlorine etchants requires changing materials used to produce the process chambers from aluminum to, for example, expensive ceramic parts or including yttrium coatings within the process chambers.
Chlorine chemistries, especially when operating in CCP chambers, reactive-ion etch (RIE) plasma-based chamber, or other types of plasma-based chambers known in the art, leads to formation of chloride ions. Chloride ions erode aluminum components by formation of volatile aluminum-chloride salts.
The information described in this section is provided to offer the skilled artisan a context for the following disclosed subject matter and should not be considered as admitted prior art.
The disclosed subject matter will now be described in detail with reference to a few general and specific embodiments as illustrated in various ones of the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the disclosed subject matter. It will be apparent, however, to one skilled in the art, that the disclosed subject matter may be practiced without some or all of these specific details. In other instances, well-known process steps or structures have not been described in detail so as not to obscure the disclosed subject matter.
With continued reference to
To prevent erosion of aluminum, anodized coatings on aluminum are typically used. However, anodized coatings also have limitations, as discussed in more detail with reference to
As noted above, contemporary technologies typically employ chlorine and chlorine-based chemistries to etch various metal oxides. In situations where chlorine does not react well with metal-oxide films, BCl3 is added to a gas mixture to etch the metal-oxide films. The use of such chemistries always or nearly always results in challenges associated with corrosion of anodized aluminum and aluminum components. For example, BCl3 may etch metal-oxide films better than Cl2. However, BCl3 also reacts with aluminum more violently than Cl2. Consequently, process chambers which deploy Cl2 or BCl3, as etch or clean gases, always or nearly always use ceramic components or expensive coatings (e.g., yttria) as noted above.
Consequently, there is a need for a chemistry that can etch tin oxide and other metal-oxide films, while continuing to use materials, such anodized aluminum and aluminum, in order to produce processing tools with a significantly lower cost as compared with using ceramic components and other expensive coatings.
In the disclosed subject matter, SOCl2 was considered as a chemistry to remove tin oxide while not etching aluminum and aluminum alloys. As discussed in greater detail below, SOCl2 has a lower corrosive impact on anodized aluminum and aluminum as compared with a chlorine-based chemistry.
Referring now to
In
In
Possible reactions using the SOCl2 combined with tin oxide or silicon dioxide are shown in
For example,
Referring now to
The Cl2 had an increasing selectivity with an increasing etch rate. The material compatibility analysis indicated that Cl2 exhibited a strong attack of aluminum even through anodization and oxide with an exposure to Cl2 of 720 minutes. In contrast, the SOCl2 showed little to no attack of aluminum through anodization even at a 720-minute exposure.
One hypothesis for the higher etch rate observed with SOCl2 is its ability to getter oxygen out of the metal-oxide film to form SO2 (a volatile byproduct) along with the formation of the volatile chemical tin tetrachloride (SnCl4). In the case of using chlorine chemistry, the oxygen in the metal-oxide film leads to formation of SnOCl2 or SnOCl4 which is not as volatile as SnCl4 and thus leads to a slowdown in reaction rates.
A hypothesis for the SOCl2 chemistry showing less attack on aluminum and anodized aluminum is the possibility of oxygen species acting as a self-passivation species, leading to formation of aluminum oxide instead of aluminum chloride when both oxygen species and chlorine species are present. There is also a possibility that the breakdown of SOCl2 in a plasma state is such that S═O bonds absorbs a lot of the energy, leading to formation of chloride ions with lower energy, which are not that harmful on the anodized components.
Although the results were conducted in CCP chambers, the skilled artisan will recognize that similar results should be expected in RIE plasma, high-density plasma (HDP)-based devices and tools, inductively-coupled plasma (ICP)-based devices and tools, and others, as a way to etch metal-oxide films and also a way to use chlorine-based chemistry with anodized aluminum and aluminum parts.
Therefore, the use of SOCl2 as a way to supply chloride ions/species to clean/etch metal oxides in, for example, CCP or RIE chambers in such a way that it etches the metal oxide at significantly higher etch rates compared with chlorine itself. Also, the ability of the SOCl2 to provide these high etch-rates while not attacking the anodized aluminum and minimal attack on aluminum components is unique and provides an opportunity to use this chemistry to etch metal-oxide films with anodized parts, without the need of going to ceramic parts or yttrria-coated parts which are extremely expensive.
Use of the chemistry SOCl2 provides unique advantages in terms of etching metal-oxide films with chlorine ions while not attacking the anodization and aluminum components of the chambers in which such films are formed. Not attacking aluminum components is in stark contrast with chlorine or BCl3 chemistries that are typically used by the semiconductor and related industries.
As noted herein, when comparing etch rates of SnO2 films in chlorine and SOCl2 in CCP chambers, an etch rate of SnO2 of up to 10-times higher in SOCl2 chemistry compared to Cl2 chemistry for similar volumetric flow-rates and process conditions. The high etch-rate observed for SnO2 in SOCl2 stems from the fact that the SOCl2 is able to getter the oxygen species from the SnO2 films, thereby forming volatile SO2 and volatile SnCl4.
2SOCl2+SnO2→SnCl4+2SO2
An additional factor to consider is that, for a given application, the boiling point of SnCl4 is 114° C.
In the case of Cl2, the reaction produces less volatile SnOCl4.
SnO2+Cl2→Cl2OSn+OCl2
with decomposition ½ Cl2.
SnO2+SnCl4
Decomposition of Cl2OSn reaction would happen with additional chlorine and would lead to formation of:
SnCl4 and SnO2→SnO2+SnCl4
The reaction of Cl2 is unfavorable due to the formation of less-volatile SnOCl2 while the reaction with SOCl2 is more favorable and, consequently, etch rates are higher with SOCl2.
In addition to higher etch rates seen with SOCl2 chemistry compared to Cl2 chemistry with SnO2 film, the SOCl2 chemistry doesn't attack anodized aluminum and very minimally attacks aluminum. As disclosed herein, this behavior is very different than what was observed with Cl2 chemistry where aluminum components were corroded heavily and even completely destroyed. Even anodized aluminum showed signs of erosion in the aluminum layer below the anodized layer (anodization also suffered a loss in thickness).
The ability to use this SOCl2 chemistry provides a pathway to etch and clean metal-oxide films such as SnO2 from process chambers while still using anodization components, while not resorting to ceramic components or yttria-based coatings which are typically extremely expensive and can make the entire tool cost highly prohibitive.
In a first example, the disclosed subject matter includes a method of etching tin oxide (SnO2) films from surfaces. The method includes using thionyl chloride (SOCl2 ) chemistry to etch at least a portion of the SnO2 films, and gettering oxygen species from the SnO2 films by using the SOCl2 chemistry, thereby forming volatile SO2 and volatile SnCl4.
A second example includes the method of the first example, where the surfaces comprise at least one material including materials of aluminum and anodized aluminum.
A third example includes any one of the preceding examples, and where the SOCl2 chemistry used to etch at least a portion of the SnO2 films produces an etch rate of the SnO2 films of up to ten-times higher as compared with chlorine Cl2 chemistry for comparable flow-rates and process conditions.
A fourth example includes any one of the preceding examples, and further includes avoiding using one or more of the following chemistries to avoid forming one or more volatile aluminum-halide byproducts, the chemistries including chlorine (Cl2), hydrochloric acid (HCl), bromide (Br), hydrobromic acid (HBr), boron trichloride (BCl3), hydrogen iodide (HI), and iodine (I2).
A fifth example includes any one of the preceding examples, where the surfaces include interior portions of plasma-based processing chambers.
A sixth example includes any one of the preceding examples, where the SOCl2 chemistry does not etch anodized aluminum.
In a seventh example, the disclosed subject matter includes a method of cleaning tin oxide from interior portions of a plasma-based processing chamber. The method includes introducing methane into the processing chamber, maintaining a temperature of greater than about 135° C. within the processing chamber to maintain a concentration level of the methane, and introducing thionyl chloride into the processing chamber and avoiding introducing chlorine into the processing chamber.
An eighth example includes the method of the seventh example, where the interior portions of the plasma-based processing chamber comprise at least one material including materials of aluminum and anodized aluminum.
A ninth example includes the method of the eighth example, and further includes avoiding introducing one or more of the following chemistries into the processing chamber to avoid forming one or more volatile aluminum-halide byproducts, the chemistries including hydrochloric acid (HCl), bromide (Br), hydrobromic acid (HBr), boron trichloride (BCl3), hydrogen iodide (HI), and iodine (I2).
In a tenth example, the disclosed subject matter includes a method for removing metal-oxide films from aluminum and aluminum-based surfaces of plasma-based processing chambers. The method includes introducing methane (CH4) into the processing chamber, introducing hydrogen (H2) into the processing chamber, maintaining a temperature of greater than about 135° C. within the processing chamber to maintain a concentration level of the methane, and introducing thionyl chloride (SOCl2) into the processing chamber and avoiding introducing chlorine (Cl2) into the processing chamber.
An eleventh example includes the method of the tenth example, and further includes avoiding introducing one or more of the following chemistries into the processing chamber to avoid forming one or more volatile aluminum-halide byproducts, the chemistries including hydrochloric acid (HCl), bromide (Br), hydrobromic acid (HBr), boron trichloride (BCl3), hydrogen iodide (HI), and iodine (I2).
A twelfth example includes any one of the preceding examples, where the metal-oxide film is tin oxide (SnO2).
A thirteenth example includes the method of the twelfth example, where a reaction using two thionyl chloride (SOCl2) molecules to etch the tin oxide (SnO2) produces tin tetrachloride (SnCl4) plus two sulfur dioxide (SO2) molecules.
A fourteenth example includes any one of the preceding examples, and further includes etching dielectric materials from the surfaces of the of plasma-based processing chambers.
A fifteenth example includes the method of the fourteenth example, where the dielectric material is silicon dioxide (SiO2).
A sixteenth example includes the method of the fifteenth example, where a reaction using two thionyl chloride (SOCl2) molecules to etch the silicon dioxide (SiO2) produces silicon tetrachloride (SiCl4) plus two sulfur dioxide (SO2) molecules.
Throughout this specification, plural instances may implement components, operations, chemistries, or structures described as a single instance. Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated. Structures and functionality presented as separate components in example configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein.
Certain embodiments may be described herein as including logic or a number of components, modules, mechanisms, or particular chemistries. In various embodiments, one or more computer systems (e.g., a standalone computer system, a client computer system, or a server computer system) or one or more hardware modules of a computer system (e.g., a processor or a group of processors) may be configured by software (e.g., an application or application portion) as a hardware module that operates to perform certain operations (e.g., various process recipes) as described herein.
As used herein, the term “or” may be construed in an inclusive or exclusive sense. Further, other embodiments will be understood by a person of ordinary skill in the art upon reading and understanding the disclosure provided. Further, upon reading and understanding the disclosure provided herein, the person of ordinary skill in the art will readily understand that various combinations of the chemistries, techniques, and examples provided herein may all be applied in various combinations.
Although various embodiments are discussed separately, these separate embodiments are not intended to be considered as independent techniques or designs. As indicated above, each of the various portions may be inter-related and each may be used separately or in combination with other portions and embodiments discussed herein. For example, although various embodiments of methods, operations, chemistries, and processes have been described, these methods, operations, chemistries, and processes may be used either separately or in various combinations.
Consequently, many modifications and variations can be made, as will be apparent to a person of ordinary skill in the art upon reading and understanding the disclosure provided herein. Functionally equivalent methods and devices within the scope of the disclosure, in addition to those enumerated herein, will be apparent to the skilled artisan from the foregoing descriptions. Portions and features of some embodiments may be included in, or substituted for, those of others. Such modifications and variations are intended to fall within a scope of the appended claims. Therefore, the present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.
The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. The abstract is submitted with the understanding that it will not be used to interpret or limit the claims. In addition, in the foregoing Detailed Description, it may be seen that various features may be grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as limiting the claims. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.
This patent application claims priority to U.S. Provisional Application Ser. No. 62/734,648, entitled, “ETCHING METAL-OXIDE FILMS AND PROTECTING CHAMBER COMPONENTS FROM HALOGEN (CHLORINE) CHEMISTRIES,” filed 21 Sep. 2018; the disclosure of which is incorporated herein by reference in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US2019/052208 | 9/20/2019 | WO | 00 |
Number | Date | Country | |
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62734648 | Sep 2018 | US |