Abstract:
The present invention relates generally to the field of semiconductor devices, including solar cells, and compositions and methods for processing semiconductor devices, passivation of semiconductor surfaces, semiconductor etching and anti-reflective coatings for semiconductor devices.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application claims the benefit, under 35 U.S.C. §119(e), of U.S. Provisional Application Ser. No. 62/026,282, filed Jul. 18, 2014, entitled “Compositions and Methods for Semiconductor Processing and Devices Formed Therefrom,” the entire contents of which is hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     The present invention relates generally to the field of semiconductor devices, including solar cells, and compositions and methods for processing semiconductor devices, passivation of semiconductor surfaces, semiconductor etching and anti-reflective coatings for semiconductor devices. 
     SUMMARY 
     In one embodiment, the present invention provides a composition for treating a semiconductor surface, wherein the composition comprises (a) an oxidant, (b) a compound comprising fluorine, (c) one or more additives, and (d) water. In some embodiments, the composition comprises A wt % of said oxidant, B wt % of said compound comprising fluorine, C wt % of said one or more additives, and D wt % water, wherein the sum of A, B, C, and D is about 100. In certain embodiments, the oxidant comprises one or more halogens and/or chalcogens. In some embodiments, the oxidant comprises one or more of oxygen, sulfur, selenium, or tellurium. In some embodiments, the oxidant is H 2 SeO 3 . In other embodiments, the oxidant comprises one or more of fluorine, chlorine, or bromine. In some embodiments, the oxidant is selected from chloric acid and bromic acid. In some embodiments, the oxidant is an oxyacid having the empirical formula H a R b O c . In certain embodiments, R is a halogen or a chalcogen. In some embodiments, a is 1, 2, 3 or 4. In other embodiments, b is 1, 2 or 3. In some embodiments, c is 1, 2, 3, 4, 5, 6, 7 or 8. In some embodiments, the oxidant is an oxyacid having the empirical formula HRO 3  or H 2 RO 3 . In some embodiments, the oxidant is an oxyacid having a trigonal pyramidal molecular geometry. In certain embodiments, A is from about 0.01 wt % to about 1 wt %. In some embodiments, B is from about 0.1 wt % to about 10 wt %. In other embodiments, C is from about 1 wt % to about 50 wt %. In some embodiments, the compound comprising fluorine comprises one or more of HF, H 2 SiF 6 , NH 4 F, H 2 TiF 6 , BaF, BF 4 , NaF, metal fluorides and non-metal fluorides. In some embodiments, the compound comprising fluorine is HF. In certain embodiments, the compound comprising fluorine is NH 4 F. In some embodiments, the one or more additives comprise one or more of HF, HCl, HBr, HI, H 3 PO4 and NH 4 OH. In certain embodiments, the one or more additives is NH 4 OH. In some embodiments, the ratio of B to C is from about 4:1 to about 1:20. In one embodiment, the oxidant is H 2 SeO 3  which is present in an amount of from about 0.01 g/L to about 1 g/L. 
     In another embodiment, the present invention provides a dilute aqueous solution comprising a composition as described herein, and water. In certain embodiments, the dilute aqueous solution comprises a composition as described herein and water in a ratio of from about 1:4 to about 1:10. 
     In another embodiment, the present invention provides a semiconductor device comprising at least one passivated oxide layer, wherein said passivated oxide layer is formed by treating said semiconductor device with a composition or dilute aqueous solution as described herein. In some embodiments, the semiconductor device comprises a passivated oxide layer having a thickness of from about 40 Å to about 200 Å. In some embodiments, the semiconductor device exhibits a sheet rho after forming said passivated oxide layer of from about 50 to about 120 ohm/sq. In certain embodiments, the semiconductor device exhibits a sheet rho after forming said passivated oxide layer of from about 60 to about 90 ohm/sq. In other embodiments, the semiconductor device exhibits a sheet rho delta after forming said passivated oxide layer of from about 3 to 20 ohm/sq. In some embodiments, the semiconductor device exhibits a sheet rho delta after forming said passivated oxide layer of from about 9 to 15 ohm/sq. In one embodiment, the semiconductor device exhibits a sheet rho delta after forming said passivated oxide layer of about 10 ohm/sq. 
     In another embodiment, the semiconductor device comprising at least one passivated oxide layer exhibits a reflectance minimum at a wavelength greater than a substantially similar semiconductor device which does not comprise a passivated oxide layer. In certain embodiments, the wavelength of light incident on the surface of the semiconductor device is red-shifted by from about 20 nm to about 45 nm. 
     In another embodiment, the present invention provides a method of growing an oxide layer on a semiconductor device, the method comprising comprises contacting at least one surface of a semiconductor device with a composition or dilute aqueous solution as described herein. In some embodiments, contacting is conducted for a time of from about 3 sec to about 1000 sec. In certain embodiments, the oxide layer has a thickness of from about 40 Å to about 200 Å. 
     In another embodiment, the present invention provides a method of making the compositions described herein, comprising admixing: (a) an oxidant, (b) a compound comprising fluorine, (c) one or more additives, and (d) water. In certain embodiments of a method of making the compositions described herein, the composition comprises A wt % of said oxidant, B wt % of said compound comprising fluorine, C wt % of one or more additives, and D wt % water, wherein the sum of sum of A, B, C, and D is about 100. In some embodiments, A is from about 0.01 wt % to about 1.0 wt %. In other embodiments, B is from about 0.1 wt % to about 10 wt %. In some embodiments, C is from about 1 wt % to about 50 wt %. In one embodiment, B is less than 10. In other embodiments, B is less than 7. 
     In another embodiment, the present invention provides a method of preparing a dilute aqueous solution as described herein, comprising admixing a composition as described herein with water. In some embodiments the ratio of the composition to water is from about 1:4 to about 1:10. 
     It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The skilled artisan will understand that the drawings primarily are for illustrative purposes and are not intended to limit the scope of the inventive subject matter described herein. The drawings are not necessarily to scale; in some instances, various aspects of the inventive subject matter disclosed herein may be shown exaggerated or enlarged in the drawings to facilitate an understanding of different features. In the drawings, like reference characters generally refer to like features (e.g., functionally similar and/or structurally similar elements). 
         FIG. 1A  is a plot of the change in sheet resistance of a surface of silicon as a function of time due to the growth of an oxide layer on the surface of the silicon wafer for different acidity levels of the composition used to treat the surface. 
         FIG. 1B  is a plot of the amount of iodic acid left in its acidic and deprotonated forms in a composition used to treat semiconductor surfaces as the acidity of the composition decreases. 
         FIG. 2  is a plot of the change in sheet resistance of a surface of silicon as a function of time for different concentrations of the oxidizing agent iodic acid in the composition used to treat the surface. In all three experiments, the composition includes no hydrochloric acid. 
         FIG. 3A  is a plot showing the effect of sulfuric acid on the change in sheet resistance of a surface of silicon as a function of time for different concentrations of the oxidizing agent iodic acid in the composition used to treat the surface. 
         FIG. 3B  is a plot showing the effect of nitric acid on the change in sheet resistance of a surface of silicon as a function of time for different concentrations of the oxidizing agent iodic acid in the composition used to treat the surface. 
         FIG. 4  is a table of oxidants that can be used in compositions to etch the surface of a silicon wafer, and the effects of the oxidants in growth of an oxide film on the surface, as detected by color change of the surface. 
         FIG. 5A  is a plot showing the change in sheet resistance of a surface of silicon as a function of time for composition or varying acidity used to treat a surface, with selenous acid as the oxidizing agent in the composition. 
         FIG. 5B  is a plot showing of the pKa values for selenous acid in compositions used to treat semiconductor surfaces. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention discloses provides compositions for treating the semiconductor devices to obtain certain desired properties. For example, in etching silicon (Si) wafers to obtain a certain surface texture, a composition comprising an oxidant, and an acid or base to remove the oxidized surface may be used. In some embodiments, the composition may also include a buffering agent and/or a diluent. The buffering agent may be used to control the acidity of the composition and further replenish ions that are used up in the etching process, thereby contributing to the maintenance of a stable etching rate. The diluent may be used to transport out products of the surface treatment process and other excess reactants. The performance of the composition may be measured by, for example, the change in the sheet resistance rho (Δρ) of the surface of the semiconductor device being treated by the composition. 
       FIG. 1A  shows an exemplary plot of Δρ of a semiconductor device comprising silicon wafer due to the growth of passivated oxide layer on surfaces of the device for different pH levels of the composition used to treat the device. In some embodiments of the present invention herein, the composition used to etch the semiconductor surface comprises iodic acid (HIO 3 ) as the oxidant. For example, for the device comprising silicon, iodic acid may interact with silicon to produce silicon dioxide (SiO 2 ) as shown in the following chemical reaction:
 
Si+4HIO 3 →SiO 2 +4IO 2 +2H 2 O.
 
     The efficiency of the above chemical reaction depends on the acidity of the composition and/or the concentration of iodic acid in the composition. For example, iodic acid is a stronger oxidant in an acidic solution as opposed to a basic one. In some embodiments, hydrocholoric acid (HCl) may be used to regulate the pH level of the composition. The oxidizing ability of the composition may also depend on how strongly iodic acid dissociates in a solution, a property that can be quantitatively measured by the acid dissociation constant K a , or more commonly by the logarithm of the acid dissociation constant pK a . The pK a  of iodic acid (i.e., half the amount of the iodic acid has dissociated into the conjugate base IO 3   −  and hydrogen ions H + ) is 0.75, indicating an acid that dissociates strongly and may not be as effective of an oxidant in a composition with a higher pH value. For example, as shown in  FIG. 1B , iodic acid deprotonates (dissociate into H +  and IO 3   − ) rather rapidly as the acidity of the solution decreases (although remaining acidic). For example, the concentration  140  of the deprotonated form of iodic acid (IO 3   − ) reaches about 99% while the composition itself has a strong acidity level of pH about 2.6, whereas the concentration  150  of the acidic form (HIO 3 ) falls to about 1%. At this level of iodic acid concentration, the composition may lose its oxidizing capacity to a large extent, as can be seen in  FIG. 1A . For example, the change in the sheet resistance  110  of a silicon wafer etched with a composition comprising iodic acid and at a pH level of about 1.4 is significant, with the exemplary embodiment in  FIG. 1A  showing an increase of about 40Ω in about a minute. This corresponds to the growth of a film of oxide layer (e.g., SiO 2 ) on the surface of the wafer. When the pH of the composition increases to 2.6 and further to 3, corresponding to a decreasing concentration of HIO 3 , the changes in the sheet resistance  120  and  130  hardly change over a course of a minute indicating that SiO 2  was not being formed on the wafer surface. 
     In the exemplary embodiments shown in  FIG. 1 , the composition used to treat the surface of the semiconductor device comprises nitric acid (HNO 3 ) as an oxidant and hydrofluoric acid (HF) as an agent capable of etching the oxidized surface. For example, the oxidation of a silicon surface by an acid such as iodic acid may result in SiO 2  forming on the surface of the wafer. To texture or pattern the surface, in some embodiments, a dissolving agent such as hydrofluoric acid (HF) may be used. For example, HF may dissolve a layer of SiO 2  formed on a silicon layer as shown in the following chemical reaction:
 
SiO 2 +HF→H 2 SiF 6 +2H 2 O.
 
     In some embodiments, additional additives (e.g., non-oxidizing acids or bases) may be included in the composition used to treat the wafer surface. For example, ammonium fluoride (NH 4 F) may be used as a buffering agent to control the pH of the composition and serve as source of additional fluoride ions. In addition, diluents such as acetic acid and/or water may be used as medium to transport reactants/by-products out of the silicon surface. This results in a more stable and controllable etching rate. 
       FIG. 2  shows exemplary plots of Δρ as a function of time for different concentrations of iodic acid in the composition used to treat the semiconductor device. The compositions used in the exemplary embodiments of  FIG. 2  comprise iodic acid as an oxidant and HF as a dissolving agent. Furthermore, the composition does not comprise hydrochloric acid (HCl), and yet all the plots show growth of surface oxide over time as measured by Δρ. In some embodiments, the rate of growth depends on the concentration of the oxidizing agent, with higher concentrations resulting in faster growth. For example, for composition  230  comprising iodic acid, the rate of surface oxide growth is about six times that of a composition  210  with a lower iodic acid concentration. Nevertheless, all three plots  210 ,  220  and  230  with HIO 3  at varying concentrations exhibit surface oxide growth, indicating that HCl is not needed in the etching composition to allow the formation of oxide layer on the semiconductor surface. 
     In some embodiments, it may be desirous to use other types of acids in etching compositions instead of, or in conjunction with, HCl. Examples of other acids that may be used in an etching composition are sulfuric acid (H 2 SO 4 ), nitric acid, or other mineral acids. The effect of some of the acids on the growth of oxide layers on semiconductor surfaces may depend on the concentration of the oxidant in the composition. For example,  FIG. 3A  illustrates surface layer growth as measured by Δρ when the etching composition comprises H 2 SO 4  and the oxidant is iodic acid. For low concentrations of the oxidant HIO 3 , the presence of sulfuric acid in the composition increases the growth rate of oxide formation on the semiconductor surface as can be seen by the higher value of Δρ  360  compared to that of Δρ  350  where the surface was treated with a composition without sulfuric acid. However, as the concentration of the oxidant HIO 3  increases, the addition of sulfuric acid into the composition starts to exhibit the opposite effect, reducing the sheet resistance Δρ  340  compared to Δρ  330  for the majority of the etching duration when there is no H 2 SO 4  in the composition. When the oxidant HIO 3  concentration is increased, in some embodiments, the effect of H 2 SO 4  in a composition used to treat semiconductor surfaces is to retard the growth rate of oxide formation on the surface, as can be inferred from the lower values of Δρ  320  where the composition comprises H 2 SO 4  compared to that of Δρ  310  where the amount of sulfuric acid in the composition is about zero. 
     In contrast, in some embodiments, the effect of adding nitric acid in an etching composition for treating semiconductor surfaces remains qualitatively similar for concentrations of the oxidant HIO 3 . For example, the change in the sheet resistances Δρ  322 ,  342  and  362  of a semiconductor device treated with a compositions comprising HIO 3 , when the composition comprises little or no HNO 3 , are lower than Δρ  312 ,  332  and  352 , respectively, for about same levels of HIO 3  concentration in compositions comprising nitric acid. 
       FIG. 4  shows a list of exemplary compounds that are candidates for use as oxidants in a composition to treat surfaces of semiconductor device. Using the color change that occurs on the treated surfaces of the semiconductor device when the composition comprises iodic acid as a benchmark for film growth, in some embodiments, oxidants such as ammonium peroxide sulfate ((NH 4 )S 2 O 8 ), hydrogen peroxide (H 2 O 2 ), potassium bromate (KBrO 3 ), ammonium chlorate ((NH 4 )ClO 4 ), and potassium chlorate (KClO 3 ) fail to result in the formation oxide layers on the surfaces. In some embodiments, the amount of oxidants added into the composition may not have appreciable affect on whether film growth takes place or not. For example, film growth on surfaces of silicon, as determined based on color change of the surfaces, remains nearly or completely non-existent when the amount of KBrO 3  in the composition  420  is ten times than the one in an initial composition  410  that also failed to result in film growth. The addition of potassium iodide in an amount about same as the amount of KBrO 3  used in a same composition may result in a very rapid etching but still no film growth. For example, a composition comprising 860 mg of KBrO 3  as oxidant, 25 mL of HF (49% in water concentration) as an additive, and 86 mg of KI as an additive may result in 300 Ω/sq of sheet resistance in about 80 s. However, despite the very fast etching rate, there is very little or no film growth on the surfaces of the semiconductor device. Similarly, in some embodiments, the use of different amounts of KClO 3  and addition of KI in the composition comprising KClO 3  and used to treat semiconductor surfaces may not lead to appreciable amount of film growth on the surfaces. 
     Applicants have appreciated that some of the components of the composition utilized in treating surfaces of semiconductor devices such as but not limited to silicon may not be desirable for various reasons. For example, HF is known for being a very dangerous material. It is capable of penetrating skin and attacking flesh and bones even in its diluted form, while a victim may not feel any indication until it is too late due to HF&#39;s weak acidity in the dilute state. Similarly, it may be desirable to use other acids in the compositions instead of, or perhaps along with, HCl. For example, one may wish to control the acidity of the compositions (for example, change the pH level) for different reasons. For example, some oxidants, such as but not limited to iodic acid, are better oxidants in an acidic environment, and keeping the acidity of the composition from deteriorating (i.e., keeping the pH level low) may help with preventing the degradation of the oxidants&#39; performance when treating semiconductor devices. Applicants have appreciated the need to accommodate these priorities, and have discovered components for compositions to treat semiconductor surfaces whose performances are not degraded when the pH level is increased, and result in oxide film growth on the surfaces. 
       FIG. 5  illustrates one such inventive embodiment of a composition comprising selenous acid (H 2 SeO 3 ) as an oxidant, HF as an oxide dissolving agent, and water as a diluent wherein the composition was used to treat surfaces of silicon wafers. In contrast to the performance of a HIO 3  ( FIG. 1A ), H 2 SeO 3  remains effective as an oxidant even when the composition used to treat the surfaces becomes less acidic. For example,  FIG. 5A  shows that the sheet resistance Δρ of a silicon surface increases over time when it is treated with a composition comprising H 2 SeO 3  even when the pH of the composition is about 2.6, which is markedly different from the case of a composition comprising HIO 3  and may indicate the formation of passivated oxides on the silicon surfaces. In some embodiments, H 2 SeO 3  is effective as an oxidant in compositions whose pH values are even greater than 2.6. For example,  FIG. 5A  shows H 2 SeO 3  is effective as an oxidant, as shown by the increasing values of Δρ over time when treating silicon surfaces, in compositions whose pH values are as high as about 3.9. Some of the explanation for this effect may be seen in  FIG. 5B , where the amount  510  of selenous acid (in its acidic form H 2 SeO 3 ) in a composition whose pH value is about 3.9 (in fact as high as 5) is seen to be finite. Furthermore, selenous acid in its singly-deprotonated form (HSeO 3   − ) may also be effective as an oxidant. This follows from the fact that while the amount  510  of H 2 SeO 3  in its acidic form decreases with H 2 SeO 3  converting into the singly-deprotonated (HSeO 3   − ) form, thereby increasing the amount  520  the HSeO 3   −  in the composition,  FIG. 5A  shows that oxidation takes place on the surfaces of a semiconductor device treated by the composition (e.g., for compositions with pH values of about 3.9 and less). The acidity of the composition approaches neutrality as the singly deprotonated form starts converting into the doubly-deprotonated  530  form SeO 3   2− . 
     In some embodiments, the composition used to treat semiconductor surfaces may comprise different proportions of oxidants, compounds, additives, and diluent (e.g., water). For example, the composition may comprise A wt % of an oxidant, B wt % of a compound comprising fluorine, C wt % of one or more additives, and D wt % water, wherein the sum of A, B, C, and D is about 100. In some embodiments, A ranges from about 0.01 to about 1; B ranges from about 0.1 to about 10, C ranges from about 1 to about 50, etc. As such, for example, in some embodiments, the ratio of B to C may range from about 4:1 to about 1:20. The oxidants in the composition may include one or more of halogens (e.g., fluorine, chlorine, bromine, iodine, astatine) and/or chalcogens (e.g., oxygen, sulfur, selenium, tellurium, polonium). For example, the oxidant in the composition may be selenous acid, and in such embodiments, selenous acid may be present in the composition in an amount ranging from about 0.01 g/L to about 1 g/L. As another example, the oxidant comprising one or more of halogens may be chloric acid or bromic acid. In some embodiments, the oxidants may be oxyacids (i.e., oxygen containing acids), exemplary embodiments of which have the empirical chemical formula H a R b O c . In such embodiments, a in the chemical formula may assume the values 1, 2, 3 or 4; b may assume 1, 2 or 3; and c may assume the values 1, 2, 3, 4, 5, 6, 7 or 8. In other embodiments, the oxyacid may have chemical formula of HRO 3  or H 2 RO 3 . In these embodiments, i.e., in the embodiments where the oxyacid has one of the chemical formulae H a R b O c , HRO 3  and H 2 RO 3 , R may comprise a halogen or a chalcogen. In some embodiments, the oxyacid may have a trigonal pyramidal molecular geometry. In some embodiments, one may form a dilute aqueous solution comprising water and any of the embodiments of the compositions disclosed herein. In such embodiments, the ratio of composition to water may be from about 1:4 to about 1:10. 
     In some embodiments, the compound included in the composition to treat semiconductor surfaces may comprise fluorine. Examples of such compounds are HF and NH 4 F. In some embodiments, the compound comprising fluorine may comprise one or more of HF, hydrofluosilicic acid (H 2 SiF 6 ), NH 4 F, fluorotitanic acid (H 2 TiF 6 ), barium fluoride (BaF), barium ferrite (BF 4 ), sodium fluoride (NaF), metal fluorides and non-metal fluorides. In some embodiments, the additives included in the composition to treat semiconductor surfaces may comprise ammonium hydroxide, HF, HCl, Hydrogen bromide (HBr), Hydrogen Iodide (HI), phosphoric acid (H 3 PO 4 ) and ammonium hydroxide. 
     In some embodiments, the compositions described in the present invention may be used to treat surfaces of semiconductor devices, an exemplary embodiment of a semiconductor material being silicon. In some embodiments, one may also use an aqueous solution comprising the compositions and water to treat the semiconductor devices. Such semiconductor devices, when treated by either the compositions or the aqueous solution comprising the composition, may have a passivated oxide layer formed on their surfaces. Such oxide layers may have a wide range of thicknesses, ranging from about 40 Å to about 200 Å. The growth of passivated oxide layer may contribute to surface resistance (sheet rho(ρ)) of the semiconductor device. For example, the contribution coming from being treated by a composition or an aqueous solution may increase the surface resistance by some amount, i.e., it may change the sheet rho by an amount Δρ. In some embodiments, the sheet rho delta Δρ may range from about 3 Ω/sq to about 20 Ω/sq. In some embodiments, the change Δρ may be about 9 to about 15 Ω/sq. And in yet some embodiments, sheet rho delta may be about 10 Ω/sq. Changes in the surface resistance of a semiconductor device as consequences of passivated oxide layers forming on its surfaces from being treated by compositions or aqueous solutions described herein may lead to an increase in the total sheet rho of the semiconductor device. For example, the sheet rho of such semiconductor devices may range from about 50 Ω/sq to about 120 Ω/sq. In some embodiments, the sheet rho may be from about 60 Ω/sq to about 90 Ω/sq. Another consequence of the growth of passivated oxide layers may be a red shift in the location of the wavelength at which reflectance minimum takes place. For example, a composition treated semiconductor device with a passivated layer may have a reflectance minimum at a wavelength greater than a substantially similar semiconductor device which may not comprise a passivated layer. As an example, the red shift of a light incident on a surface of a composition treated semiconductor with passivated layer may range from about 20 nm to about 45 nm. 
     While various inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure. 
     Also, various inventive concepts may be embodied as one or more methods, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments. 
     All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and/or ordinary meanings of the defined terms. 
     The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” 
     The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc. 
     As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law. 
     As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc. 
     In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.