Patent Publication Number: US-8969217-B2

Title: Methods of treating semiconductor substrates, methods of forming openings during semiconductor fabrication, and methods of removing particles from over semiconductor substrates

Description:
RELATED PATENT DATA 
     This patent resulted from a continuation application of U.S. patent application Ser. No. 12/136,661 which was filed on Jun. 10, 2008 which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     Methods of treating semiconductor substrates, methods of forming openings during semiconductor fabrication, and methods of removing particles from over semiconductor substrates. 
     BACKGROUND 
     Semiconductor fabrication may comprise exposure of a semiconductor substrate to one or more etchants to remove materials from the substrate, followed by rinsing of the substrate to remove the etchants. 
     Problems may occur during the rinsing if an etchant is not rapidly quenched, in that over-etching may occur. In some applications, the etchant may be sufficiently rapidly quenched by simply flushing deionized water across a wafer to remove the etchant. In other applications, flushing with deionized water alone may not be sufficient to quench an etchant with desired rapidity. For instance, if a semiconductor substrate comprises a topography with deep openings (for instance, openings with high aspect ratios that may be utilized for forming capacitors for DRAM), etchant may remain in the bottoms of high aspect ratio features during a rinse, and continue to etch during the rinse. 
     One method for increasing the rapidity with which etchant is quenched at the bottoms of openings is to include a quench-inducing composition within a rinsing solution. For instance, if the etchant is an acid, a base may be included within the rinsing solution to assist in quenching the acid. Alternatively, if the etchant is a base, an acid may be included in the rinsing solution. Further, hydrogen peroxide and/or hydrogen chloride may be included in a rinsing solution as a quench-inducing composition. 
     Problems may occur, however, in utilizing quench-inducing compositions, in that such compositions may themselves be etchants for some materials that are along a semiconductor substrate surface. Accordingly, the utilization of the quench-inducing compositions may alleviate some problems, and yet induce other problems that occur from over-etching caused by the quench-inducing compositions. 
     It is desirable to develop methods which alleviate or prevent the above-discussed over-etching problems. 
     Other problems that may occur during semiconductor processing are that particles may form across a semiconductor substrate. Various methods have been developed for removing such particles, but yet problems associated with the particles persist. Accordingly, it is desired to develop new approaches for removing particles from semiconductor substrates. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-3  are graphical illustrations of dynamic changes in pH, concentration and temperature, relative to time, that may occur in some embodiments. 
         FIG. 4  is a diagrammatic cross-sectional view of an apparatus, shown in process for treating a batch of wafers, in accordance with an embodiment. 
         FIGS. 5-8  are diagrammatic, cross-sectional views of a semiconductor wafer fragment at various process stages of an embodiment. 
         FIGS. 9 and 10  are diagrammatic, cross-sectional views of a semiconductor wafer fragment at sequential process stages of an embodiment. 
         FIGS. 11 and 12  are diagrammatic, cross-sectional views of a semiconductor wafer fragment at sequential process stages of an embodiment. 
         FIGS. 13 and 14  are diagrammatic, cross-sectional views of a semiconductor wafer fragment at sequential process stages of an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     In some embodiments, it is recognized that improvements may be made to the utilization of rinses for removing residual etch chemicals, etch residue and particles from surfaces of semiconductor substrates. Conventional rinses may suffer from numerous problems. For instance, there may be a thick boundary layer formed between etchant solution and rinse solution within topographical features, which renders it difficult to effectively remove the etchant solution. Further, mass transport through such boundary layer may be diffusion limited, and thus too slow to enable rapid quenching of an etchant solution. This problem may be particularly prevalent when there are deep vias or complex structures present along the surface of a semiconductor substrate. 
     Problems may also occur during intended removal of particles. The particles may be chemically absorbed onto a semiconductor surface and/or retained on the surface by electrostatic forces. 
     In some embodiments, the problems are addressed by dynamically altering a rinse solution during utilization of the rinse solution. The dynamic alteration may comprise alteration of any of numerous properties of the solution, including, for example, a temperature of the solution, a pH of the solution, and/or concentrations of one or more components of the solution.  FIGS. 1-3  graphically illustrate dynamic alteration of pH, concentration of a component, and temperature, respectively. 
     Referring to  FIG. 1 , a graph  10  comprises an x-axis corresponding to time, and a y-axis corresponding to pH. A curve  12  shows the variation of the pH of a rinse solution with time, and specifically shows that the pH is continuously variable over a period of time. In other words, the pH is non-static over the period of time, as opposed to reaching a static equilibrium. The shown curve corresponds to a pH gradient. The example curve may be considered to comprise two iterations of a process in which the pH goes from a first value  14  (shown as a low value) to a second value  16  (shown as a high value), and then back to the first value; with one of the iterations comprising a peak  18  of curve  12 , and the other comprising a peak  20  of the curve. Although the shown iterations go from a low pH to a high pH, and then back; in other embodiments the iterations may go from a high pH to a low pH, and then back. 
     The low pH  14  and high pH of  16  may differ from one another by five or more pH units, and in some embodiments may differ from one another by eight or more pH units. For instance, the low pH  14  may correspond to 2 (or another suitable acidic pH), and the high pH  16  may correspond to 10 (or another suitable basic pH). 
     The time for each iteration from a low pH to a high pH, and back, may be any suitable duration; and may be, for example, at least a few seconds. 
     The curve  12  is shown to be continuously variable during the entire duration illustrated in graph  10 . The fluctuation of the pH between the low and high pH&#39;s may be referred to as pH sweeping. 
     The pH-sweeping may provide benefits during the rinsing of a substrate including, for example, inhibition of etch conditions as discussed below with reference to  FIGS. 5-8 , and assistance in particle removal as discussed below with reference to  FIGS. 9-14 . 
     Referring to  FIG. 2 , a graph  30  comprises an x-axis corresponding to time, and a y-axis corresponding to concentration. A curve  32  shows the variation of the concentration of a composition within a rinse solution with time, and specifically shows that the concentration of the composition is continuously variable over a period of time. In other words, the concentration of the composition is non-static over the period time, as opposed to reaching a static equilibrium. 
     The shown curve corresponds to a concentration gradient. The curve may be considered to comprise two iterations of a process in which the concentration of the composition goes from a first value  34  to a second value  36 , and then back to the first value; with one of the iterations comprising a peak  38  of curve  32 , and the other comprising a peak  40  of the curve. Although the shown iterations go from a low concentration of the composition to a high concentration of the composition, and then back; in other embodiments the iterations may go from a high concentration of the composition to a low concentration of the composition, and then back. 
     The low concentration  34  and high concentration  36  may differ from one another by several fold, and in some embodiments may differ from one another by one or more orders of magnitude. For instance, the composition may comprise hydrogen chloride (i.e., hydrochloric acid) utilized to quench an etch, the low concentration may correspond to about 1 ppm (part per million), and the high concentration may correspond to about 1000 ppm. In other embodiments, the low concentration of the hydrogen chloride may correspond to about 10 ppm and the high concentration to about 1000 ppm. In yet other embodiments, the low concentration of the hydrogen chloride may correspond to about 1 ppm and the high concentration to about 10 ppm. 
     The composition having the variable concentration may be any suitable composition for treating a substrate during a rinse, and in some embodiments multiple compositions may simultaneously be varied in concentration during the treatment of a substrate. Example compositions that may be utilized in addition to, or alternatively to, the above-discussed hydrogen chloride are inorganic acids (for instance, hydrofluoric acid, nitric acid, sulfuric acid, phosphoric acid, etc.), organic acids (for instance, acetic acid, trichloroacetic acid, etc.) and bases (for instance, ammonium hydroxide, tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, etc.). The bases may be inorganic bases (for instance, ammonium hydroxide) or organic bases (for instance, tetramethyl ammonium hydroxide). Any of the compositions may be provided to the high and low concentrations discussed above with reference to the hydrogen chloride, or may be provided to other high and low concentrations appropriate for particular applications. 
     The time for each iteration from a low concentration to a high concentration, and back, may be any suitable duration; and may be, for example, at least three seconds in embodiments in which the low concentration and high concentration differ from one another by an order of magnitude or more. 
     The curve  32  is shown to be continuously variable during the entire duration illustrated in graph  30 . The fluctuation of the concentration between the low and high concentrations of a particular composition may be ceased at some point, and the substrate exposed to a static, equilibrium, concentration of the composition. 
     The alteration of a concentration of one more compositions may provide benefits during the rinsing of a substrate including, for example, inhibition of etch conditions as discussed below with reference to  FIGS. 5-8 , and assistance in particle removal as discussed below with reference to  FIGS. 9-14 . 
     Referring to  FIG. 3 , a graph  50  comprises an x-axis corresponding to time, and a y-axis corresponding to temperature. A curve  52  shows the variation of the temperature of a rinse solution with time, and specifically shows that the temperature is continuously variable over a period of time. In other words, the temperature is non-static over the period time, as opposed to reaching a static equilibrium. The shown curve corresponds to a temperature gradient. The curve may be considered to comprise two iterations of a process in which the temperature goes from a first value  54  to a second value  56 , and then back to the first value; with one of the iterations comprising a peak  58  of curve  52 , and the other comprising a peak  60  of the curve. Although the shown iterations go from a low temperature to a high temperature, and then back; in other embodiments the iterations may go from a high temperature to a low temperature, and then back. 
     The low temperature  54  and high temperature of  56  may differ from one another by at least about 30° C., and in some embodiments may differ from one another by at least about 60° C. For instance, the low temperature  54  may correspond to about room temperature (23° C.), and the high temperature  56  may correspond to about 90° C. 
     The time for each iteration from a low temperature to a high temperature, and back, may be any suitable duration; and may be, for example, at least a few seconds in embodiments in which the low temperature and high temperature differ from one another by at least about 30° C. 
     The curve  52  is shown to be continuously variable during the entire duration illustrated in graph  50 . The fluctuation of the temperature between the low and high temperatures may be referred to as temperature sweeping. At some point the temperature sweeping may be ceased, and the substrate exposed to a static, equilibrium, temperature. Such may be accomplished by flowing a static temperature rinse solution across the substrate. 
     The temperature sweeping may provide benefits during the rinsing of a substrate by enhancing kinetics of reactions in some embodiments, or by inhibiting kinetics of reactions in other embodiments. Some examples of such effects on kinetics are discussed below with reference to  FIGS. 9-14 . 
     The dynamic alteration of various properties of the rinse solution may be accomplished by any suitable method. An example method is described with reference to  FIG. 4 . 
       FIG. 4  shows an apparatus  70  comprising a vessel  72  that retains a rinse solution bath  74 . A pair of feed lines  76  and  78  are in fluid connection with the bath and configured for feeding liquid into the bath, and an outlet line  80  is in fluid connection with the bath and configured for draining liquid from the bath. Flow of liquid through the bath is illustrated by arrows  77 . The liquid may flow continuously during the dynamic alteration of one or more properties of the bath solution. 
     Although two feed lines are illustrated, in other embodiments there may be more than two feed lines. Also, although the feed lines are shown passing liquid directly to the vessel, in other embodiments the feed lines may merge upstream of the vessel so that liquid is provided from the feed lines to the bath through an intermediate carrier line. 
     Feed line  76  is shown to be in fluid connection with a reservoir  90 , and feed line  78  is shown to be in fluid connection with a reservoir  92 . In operation, one of the reservoirs may contain rinse solution under a first condition, and the other reservoir may contain rinse solution under a second condition, and the relative ratio of the amount of liquid passed through feed lines  76  and  78  may then determine the condition of the bath  74 . The feed lines  76  and  78  may each be connected to a processor  75  which controls the amount of liquid passing through each of the lines. The control of liquid through the lines may comprise utilization of one or more valves (not shown). 
     In embodiments in which a continuously variable pH is desired, one of the reservoirs  90  and  92  may comprise rinse liquid at a pH that is at or below a lowest pH of the continuously variable pH (in other words, at or below the pH  14  of  FIG. 1 ), and the other of the reservoirs may comprise the rinse liquid at a pH that is at or above the highest pH of the continuously variable pH (in other words, at or above the pH  16  of  FIG. 1 ). The amount of rinse liquid provided through feed line  76  relative to that provided through feed line  78  may then be continuously varied to achieve the continuously varying pH. 
     In embodiments in which a continuously variable concentration of a component is desired, one of the reservoirs  90  and  92  may comprise rinse liquid with a first concentration of the component that is at or below a lowest component concentration of the continuously variable component concentration (in other words, at or below the component concentration  34  of  FIG. 2 ), and the other of the reservoirs may comprise the rinse liquid having a component concentration that is at or above the highest component concentration of the continuously variable component concentration (in other words, at or above the component concentration  36  of  FIG. 2 ). The amount of rinse liquid provided through feed line  76  relative to that provided through feed line  78  may then be continuously varied to achieve the continuously varying component concentration. 
     In embodiments in which a continuously variable temperature is desired, one of the reservoirs  90  and  92  may comprise rinse liquid at a temperature that is at or below a lowest temperature of the continuously variable temperature (in other words, at or below the temperature  54  of  FIG. 3 ), and the other of the reservoirs may comprise the rinse liquid at a temperature that is at or above the highest temperature of the continuously variable temperature (in other words, at or above the temperature  56  of  FIG. 3 ). The amount of rinse liquid provided through feed line  76  relative to that provided through feed line  78  may then be continuously varied to achieve the continuously varying temperature. 
     If it is desired to continuously vary two or more parameters, multiple feed lines and reservoirs may be provided so that the parameters may be altered independently of one another; or, in other embodiments, multiple parameters may be simultaneously varied with two or more common reservoirs so that the parameters are linked to one another. In some embodiments, one or more of the properties of temperature, acid concentration, base concentration, passivating material concentration and pH may be altered within the bath  74 . If two or more of the properties are altered, they may be altered simultaneously with one another in some embodiments, and/or sequentially with one another in other embodiments. 
     A plurality of semiconductor substrates  94 ,  96  and  98  are shown within bath  74 . The substrates may be held within a support structure (not shown). The substrates are treated simultaneously with one another, and accordingly correspond to a batch of substrates treated within apparatus  70 . In other embodiments (not shown), semiconductor substrates may be treated singly, rather than in batch. 
     The semiconductor substrates may correspond to monocrystalline silicon wafers having one or more layers of integrated circuit components formed thereover. The terms “semiconductive substrate,” “semiconductor construction” and “semiconductor substrate” mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above. 
     Although two inlet lines (i.e., feed lines) are shown extending into bath  74 , in other embodiments only one feed line may be utilized if there are one or more mixing points along the feed line prior to the line entering the bath. 
     One or more of the embodiments of  FIGS. 1-4  may be incorporated into any semiconductor fabrication process in which it is desired to expose a semiconductor substrate to dynamic conditions. An example fabrication process in which one or more of the embodiments of  FIGS. 1-4  may be utilized during rinsing of etchant and/or quenching of an etch is described with reference to  FIGS. 5-8 ; and examples of fabrication processes in which one or more of the embodiments of  FIGS. 1-4  are utilized during particle removal are described with reference to  FIGS. 9-14 . 
     Referring to  FIG. 5 , a semiconductor construction  100  is illustrated. The construction includes a semiconductor base  102  which may, for example, comprise, consist essentially of, or consist of monocrystalline silicon lightly doped with background p-type dopant. Although base  102  is shown to be homogenous, it is to be understood that the base may comprise numerous layers in some embodiments. For instance, base  102  may correspond to a semiconductor substrate containing one or more layers associated with integrated circuit fabrication. In such embodiments, such layers may correspond to one or more of metal interconnect layers, barrier layers, diffusion layers, insulator layers, etc. 
     A material  104  is formed over base  102 . Material  104  may comprise any suitable material, and in some embodiments may be an electrically insulative material comprising one or more compositions selected from the group consisting of borophosphosilicate glass (BPSG), silicon dioxide, silicon nitride, etc. 
     A patterned masking material  106  is formed over material  104 . The masking material  106  may comprise, for example, photolithographically-patterned photoresist. The patterned masking material forms a patterned mask having a pair of openings  108  extending therethrough. 
     Referring to  FIG. 6 , openings  108  are extended into material  104  with one or more suitable etches. Some etchant  110  is diagrammatically illustrated as fluid within openings  108 . Such may occur if at least part of the etch utilized to form openings  108  is conducted with wet etching. 
     The etchant  110  comprises one or more compositions suitable for removing material  104 . Such compositions will vary depending on the composition of material  104 . In an example embodiment, material  104  may comprise silicon dioxide and the etchant may comprise hydrofluoric acid (either alone, or with ammonium ion as a buffered oxide etch). In another example embodiment, there may be at least some organic material exposed within openings  108 , and the etchant may comprise piranha solution (hydrogen peroxide in combination with sulfuric acid, phosphoric acid and/or ammonium hydroxide) for removing at least a portion of the organic material. In another example embodiment, there may be at least some oxide material exposed within openings  108  (silicon dioxide or metal oxides), and the etchant may comprise QE2 solution (NH 4  in combination with phosphoric acid and other components, such as HF) for removing at least a portion of the oxide material. The fluid-based etch may be isotropic, and accordingly may undercut masking material  106 , as shown. 
     The openings  108  within material  104  may be utilized for forming any of numerous components utilized in integrated circuitry. In some embodiments, the openings may be high aspect ratio openings suitable for fabrication of tightly-stacked capacitors for highly-integrated dynamic random access memory (DRAM) arrays. 
     Referring to  FIG. 7 , a rinse solution  112  is utilized to remove etchant  110  from within openings  108 . The rinse solution quickly removes most of the etchant  110 , but eddies  114  of etchant  110  remain within the bottoms of the openings, or remain in a diluted form anywhere in the openings. The etchant remaining within the openings may problematically continue etching until the rinse solution manages to disperse the material  110  from the openings. 
     In some embodiments, one or more of the procedures of  FIGS. 1-3  is utilized to dynamically alter the rinse solution and thereby reduce problematic etching occurring from etchant remaining in the eddies  114  at the bottoms of the openings. 
     For instance, if the etchant comprises acid, then the rinse solution may have the fluctuating pH of  FIG. 1  so that the acid is at least partially neutralized while the rinse solution is removing the acid from the openings. The fluctuating pH may avoid problems that could occur with a rinse solution having a static basic pH; with an example problem being undesired etching of base-sensitive materials. 
     As another example, if the etching induced by the etchant has a rate significantly influenced by temperature, the rinse solution may have the fluctuating temperature of  FIG. 3  while the rinse solution is removing the etchant  110  from within the openings. The fluctuating temperature may avoid problems that could occur with a static low-temperature rinse solution or static high-temperature rinse solution, such as undesired thermal stresses on materials. Such thermal stresses may occur if adjacent materials have substantially different thermal coefficients. 
     As yet another example, the etchant may be passivated (i.e., quenched) by various materials. For instance, acids may be quenched by bases; bases may be quenched by acids; and various etchants may be quenched by oxidants, such as hydrogen peroxide or ozone, or by reductants. The rinse solution may have the fluctuating concentration of  FIG. 2  while the rinse solution is removing the etchant  110  from within the openings, with such fluctuating concentration being the concentration of a passivating material. The fluctuating concentration may avoid problems that could occur with a static concentration of the passivating material in the rinse solution, such as undesired etching induced by the passivating material. 
     In some embodiments, two or more of the procedures of  FIGS. 1-3  may be utilized simultaneously with one another. For instance, the concentration of passivating material within a rinse solution may be fluctuated together with a temperature of the rinse solution during utilization of the rinse solution to remove etchant. Also, in some embodiments, first fluctuating conditions for quenching an etch may be followed by second fluctuating conditions for removing contaminants. 
     After the rinse solution is utilized to remove the etchant, deionized water may be utilized to remove the rinse solution, and then construction  100  may be dried to leave the construction shown in  FIG. 8 . Subsequently, integrated circuit components may be formed within the openings. For instance, capacitors may be formed within the openings during fabrication of DRAM. 
       FIGS. 9 and 10  illustrate an example embodiment for removing particles from over a semiconductor substrate. Referring to  FIG. 9 , a semiconductor construction  120  is shown to comprise a semiconductor substrate  122  having particles  124  thereover. The substrate  122  may comprise, for example, a monocrystalline silicon wafer. The substrate may have a silicon-containing surface  123 , such as a surface comprising, consisting essentially of, or consisting of one or more of silicon, silicon dioxide or silicon nitride. The particles  124  may comprise particles formed during etching or other semiconductor processing. The particles may comprise, consist essentially of, or consist of any of various materials; including, for example, one or more of metals, silicon, silicon dioxide, silicon nitride, organic materials, etc. 
     Particles  124  may adhere to surface  123  through chemical bonds and/or electrostatic interactions. If the particles adhere solely through electrostatic interactions, one or both of the surface  123  and the particles  124  may comprise pH-sensitive charged groups. For instance, particles  124  may comprise carboxylate groups that are negatively charged above a threshold pH, and neutrally charged below the threshold pH. As another example, particles  124  may comprise amine groups that are positively charged below a threshold pH, and neutrally charged above the threshold pH. 
     In some embodiments, surface  123  will comprise a negative charge (for example, from hydroxyl groups extending from the surface), and particles  124  will be electrostatically retained to the surface through positively-charged amine groups. The electrostatic interaction can thus be disrupted by exposing particles  124  to a pH which neutralizes the positively charged amine groups, or changes a charge to be negative. 
       FIG. 10  shows construction  120  as particles  124  are exposed to a rinse solution  126  comprising a pH which neutralizes the electrostatic interactions and causes particles  124  to be dispersed into the rinse solution (as illustrated by arrows  125 ). The rinse solution may have a dynamically changing pH utilizing methodology described above with reference to  FIG. 1 . The dynamically changing pH enables appropriate pH&#39;s to be found for rinsing different types of particles from a substrate. Specifically, there may be many types of particles with many varying electrostatic interactions that retain the particles to different types of surfaces across a semiconductor substrate. Utilization of the pH sweeping of  FIG. 1  within a rinse solution may enable each type of particle to be removed. Specifically, the pH sweep may be configured to pass through the particular pH&#39;s that neutralize electrostatic interaction of each type of particle so that eventually each type of particle will be neutralized and removed from the surface. In some embodiments, at least some of the particles may have their charge reversed relative to the charge of the substrate during the pH sweeping so that the electrostatic interactions between the substrate and particles change form attractive to repulsive, which may aid in removing the particles from the substrate. 
     A problem that may occur is that the strength of the electrostatic interactions between particular types of particles and the substrate may fluctuate as the pH fluctuates within the rinse solution. Accordingly, particles ejected from one location of the substrate may settle onto another location of the substrate. For instance, there are often many more particles along the edges of a semiconductor substrate than across a central region of the substrate, and the pH sweeping within the rinse solution may cause particles to migrate from the edges of the semiconductor substrate to the central region. If such problems occur, the pH sweeping may be conducted through several iterations until the number of particles remaining on the substrate has been reduced to a level below a desired tolerance. 
     If the particles are retained on substrate  122  through chemical bonds, as well as electrostatic interactions, etchant may be included within the rinse solution to weaken the chemical bonds. The etchant may comprise a composition which removes material from surface  123  of the substrate, and/or may comprise a composition which removes material from the particles. 
       FIGS. 11 and 12  illustrate an embodiment in which the rinse solution comprises a composition which removes material from surface  123 .  FIG. 11  shows construction  120  at a processing stage subsequent to  FIG. 9 , and as surface  123  is initially exposed to rinse solution  126 . The etchant within the rinse solution removes substrate  122  from under the particles. Such undercuts the particles, and specifically forms voids  128  extending under particles  124 . The undercutting of the particles weakens chemical bonding between the particles  124  and the substrate  122 . In an example embodiment, surface  123  may comprise silicon dioxide, and the etchant may comprise hydrofluoric acid. 
     The concentration of the etchant within the rinse solution may be dynamically altered utilizing the methodology of  FIG. 2 . Such may avoid, or at least alleviate, undesired etching of substrate  122 . 
     If the etchant has an etch rate significantly influenced by temperature, the temperature of the rinse solution may be dynamically altered utilizing the methodology of  FIG. 3 , either additionally, or alternatively, to the alteration of the concentration of the etchant within the rinse solution. 
     Referring to  FIG. 12 , particles  124  are dispersed from surface  123 . Such dispersal may be due entirely to the undercutting of the particles induced by the etching, and accordingly may occur without pH sweeping within the rinse solution. Alternatively, the dispersal may be enhanced by reducing electrostatic attraction between the particles and the substrate through pH sweeping within the rinse solution. Such pH sweeping may occur during or after the utilization of the etchant to undercut the particles. 
       FIGS. 13 and 14  illustrate an embodiment in which the rinse solution comprises a composition which removes material from particles  124 .  FIG. 13  shows construction  120  at a processing stage subsequent to  FIG. 9 , and as particles  124  are initially exposed to rinse solution  126 . The etchant within the rinse solution removes material from the particles, and alters the outer surface of the particles to reduce the area of the interfaces between the particles and the substrate. The etching of the particles thus weakens chemical bonding between the particles  124  and the substrate  122 . In an example embodiment, the particles may comprise organic material, and the etchant may be a piranha mixture. 
     The concentration of the etchant within the rinse solution may be dynamically altered utilizing the methodology of  FIG. 2 . Such may avoid, or at least alleviate, undesired etching of substrate  122 . 
     If the etchant has an etch rate significantly influenced by temperature, the temperature of the rinse solution may be dynamically altered utilizing the methodology of  FIG. 3 , either additionally, or alternatively, to the alteration of the concentration of the etchant within the rinse solution. 
     Referring to  FIG. 14 , particles  124  are dispersed from surface  123 . Such dispersal may be due entirely to the reduction of the amount of interface between the particles and substrate induced by the etching, and accordingly may occur without pH sweeping within the rinse solution. Alternatively, the dispersal may be enhanced by reducing electrostatic attraction between the particles and the substrate through pH sweeping within the rinse solution. Such pH sweeping may occur during or after the etching of the particles. 
     Although  FIGS. 10-14  illustrate embodiments in which the etching of the substrate occurs separately from the etching of the particles, in other embodiments etchant may be chosen which etches both the substrate and the particles. 
     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.