Abstract:
A high voltage inspection system that includes a vacuum chamber; electron optics that is configured to direct an electron beam towards an upper surface of a substrate; a substrate support module that comprises a chuck and a housing; wherein the chuck is configured to support a substrate; wherein the housing is configured to surround the substrate without masking the electron beam, when the substrate is positioned on the chuck during a first operational mode of the high voltage inspection system; and wherein the substrate, the chuck and the housing are configured to (a) receive a high voltage bias signal of a high voltage level that exceeds ten thousand volts, and (b) to maintain at substantially the high voltage level during the first operational mode of the high voltage inspection system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 62/325,391, filed Apr. 20, 2016, the entire contents of which are incorporated herein by reference in their entirety for all purposes. 
     
    
     BACKGROUND 
       [0002]    Scanning electron microscopes review an object with a charged electron beam. The electrons of the charged electron beam are accelerated by an acceleration voltage. 
         [0003]    Increasing the acceleration voltage may provide various benefits but may expose the scanning electron microscope to the formation of arcs, breakdowns and other hazards that accompany high voltage devices. 
         [0004]    There is a growing need to reduce the hazards associated with high voltage in a scanning electron microscope. 
       SUMMARY 
       [0005]    According to an embodiment of the invention there may be provided a high voltage inspection system, modules of the high voltage inspection system and a method for inspecting using the high voltage inspection system. The inspection system may be used for inspection, metrology, and the like. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The objects, features, and advantages of embodiments described herein may best be understood by reference to the following detailed description when read with the accompanying drawings in which: 
           [0007]      FIG. 1  is a cross sectional view of a substrate and a high voltage inspection system according to an embodiment; 
           [0008]      FIG. 2  is a cross sectional view of a substrate and a high voltage inspection system according to an embodiment; 
           [0009]      FIG. 3  is a top view of top conductive module, optical microscope electron optics and different positions of the housing according to various embodiments; 
           [0010]      FIG. 4  illustrates the high voltage inspection system according to an embodiment; 
           [0011]      FIG. 5  illustrates the vacuum chamber and the top surface of the X-Y stage according to an embodiment; 
           [0012]      FIG. 6  illustrates base and bottom insulators according to an embodiment; 
           [0013]      FIG. 7  illustrates a top surface, base, and bottom insulators according to an embodiment; 
           [0014]      FIG. 8  illustrates a lower part of a housing of the insulating module and some components of the insulating module according to an embodiment; 
           [0015]      FIG. 9  illustrates a cover of the housing of the insulating module, cables, lower plate, upper plate and terminals according to an embodiment; 
           [0016]      FIG. 10  illustrates that the bottom conductive shield is positioned below the housing and above the bottom insulators and base according to an embodiment; 
           [0017]      FIG. 11  illustrates a chuck, housing, bottom conductive shield and bottom insulators according to an embodiment; 
           [0018]      FIG. 12  illustrates an upper shield, chuck, housing, bottom conductive shield and bottom insulators according to an embodiment; 
           [0019]      FIG. 13  illustrates the top conductive module according to an embodiment; 
           [0020]      FIG. 14  includes a perspective view and a cross-sectional view of a resistor having a first port, a second port and a creepage reduction element according to an embodiment; 
           [0021]      FIG. 15  illustrates the insulating module according to an embodiment; and 
           [0022]      FIG. 16  illustrates the insulating module according to an embodiment. 
       
    
    
       [0023]    It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. 
       DETAILED DESCRIPTION 
       [0024]    In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those skilled in the art that the various embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure other features. 
         [0025]    Because some embodiments may, for the most part, be implemented using electronic components and circuits known to those skilled in the art, details will not be explained in any greater extent than considered necessary for the understanding and appreciation of the underlying concepts and in order not to obfuscate or distract from the teachings described herein. 
         [0026]    Any reference in the specification to a method should be applied mutatis mutandis to a system capable of executing the method and should be applied mutatis mutandis to a non-transitory computer readable medium that stores instructions that once executed by a computer result in the execution of the method. 
         [0027]    Any reference in the specification to a system should be applied mutatis mutandis to a method that may be executed by the system and should be applied mutatis mutandis to a non-transitory computer readable medium that stores instructions that may be executed by the system. 
         [0028]    Any reference in the specification to a non-transitory computer readable medium should be applied mutatis mutandis to a system capable of executing the instructions stored in the non-transitory computer readable medium and should be applied mutatis mutandis to method that may be executed by a computer that reads the instructions stored in the non-transitory computer readable medium. 
         [0029]    The term “high voltage” refers to voltage levels that exceed 10000 volts and may reach, for example, 20000 volts, 30000 volts, or more. 
         [0030]      FIG. 1  is a cross sectional view of a substrate  20  and a high voltage inspection system  10  according to an embodiment. 
         [0031]    The high voltage inspection system  10  is illustrated as including processor  30 , controller  40 , memory unit  50 , X-Y stage  100 , base  110 , insulating module  200 , substrate support module  333 , bottom insulator  410 , electron optics  500 , high voltage supply unit  600 , first feedthrough module  620 , second feedthrough module  622 , cables  630 , test circuit  640 , interferometer  650 , interferometer window  652 , vacuum chamber  700 , top conductive unit  900  and top insulator  960 . 
         [0032]    Processor  30  may be configured to process detection signals from the electron optics  500 . Processor  30  may generate and/or analyze images. 
         [0033]    Controller  40  may control the operation of the high voltage inspection system  10 . 
         [0034]    Memory unit  50  may store commands, recipes, images of the substrate, reference images and the like. 
         [0035]    The electron optics  500  may be a column but other types of electron optics may be provided. 
         [0036]    The substrate support module  333  includes bottom conductive shield  310 , housing  320 , chuck  330  and upper shield  340 . The housing  320  is positioned between the bottom conductive shield  310  and the upper shield  340 . 
         [0037]    The housing  320  may include sidewalls that are coated with light reflecting and electrically conducting materials to form mirrors that are used by interferometer  650  to detect the location of the housing  320 . Light beams from interferometer  650  pass through interferometer opening  652 , impinge on the sidewalls of the housing and are reflected to the interferometer  650 . The high voltage inspection system  10  may include an additional interferometer (not shown) that illuminates another sidewall of the housing. 
         [0038]    The location information obtained by the interferometer  650  may be used by controller  40  to control the movement of the X-Y stage  100 . The X-Y stage  100  may be replaced by a X-Y-Z stage and/or by a rotating stage in some embodiments. 
         [0039]    In order to guarantee the accuracy of the location determination, the mirrors should not be deformed due to heat changes. The lack of deformation may be achieved by using a housing that includes a core that is made of an extremely low expansion material such as a glass ceramic like ZERODUR™ of Schott. Other extremely low expansion materials may be used. 
         [0040]    Because a core that is made of ZERODUR™ is fragile—the housing may be mechanically shielded and/or protected by an upper shield  340  positioned on top of the housing  320  and a bottom shield  310  positioned below the housing  320 . 
         [0041]    One or more shields of upper shield  340  and bottom shield  310  may be integrated with the housing  320 . Both upper shield  340  and bottom shield  310  are made of electrically conductive materials. 
         [0042]    The housing  320  may be coated with electrically conductive material and/or may include an electrically conductive envelope. Parts of the exterior of the housing that are not used as a mirror may or may not reflect light. 
         [0043]    The high voltage inspection system  10  may inspect the substrate  20  when operating at a first operational mode. 
         [0044]    During other operational modes, the high voltage inspection system  10  may perform maintenance operations (such as plasma cleaning), may perform vacuum pumping, may inspect the substrate  20  using an optical microscope (denoted  510  in  FIG. 2 ), may insert the substrate  20  into the vacuum chamber  700 , may position the substrate  20  on the chuck  330 , may remove the substrate  20  from the chuck  330 , and may evacuate the substrate  20  from the vacuum chamber  700 . The substrate  20  may be manipulated by a robot or any other unit known in the art. 
         [0045]    The chuck  330  may be any known chuck. The chuck may use electrostatic force, vacuum and/or any other known method to hold the substrate  20 . 
         [0046]    The chuck  330  can also be made of an electrically conductive material or may include an electrically conductive exterior or an electrically conductive upper part. 
         [0047]    When the high voltage inspection system  10  operates at the first operational mode the substrate  20  is surrounded by the chuck  330  and the housing  320 . The sidewall of the substrate  20  is surrounded by the housing  320 . 
         [0048]    Both the chuck  330  and the housing  320  may be substantially maintained at a given high voltage level regardless of the motion of the X-Y stage  100 . 
         [0049]    A top conductive unit  900  is positioned above the substrate  20 . When the high voltage inspection system  10  operates at the first operational mode, the substrate  20  is proximate to the top conductive unit  900 . The distance between substrate  20  and the top conductive unit  900  may be millimetric or below a predefined distance threshold. 
         [0050]    When the high voltage inspection system  10  operates at the first operational, the X-Y stage  100  may move the substrate support module  333  (and accordingly move the substrate  20 ) in order to expose different areas of the substrate to the electron beam  502 . 
         [0051]    The top conductive unit  900  may be static but is shaped and sized to “cover” the entire movement of the substrate, so that regardless of the position of the substrate  20 , the substrate is positioned below the top conductive unit  900 . 
         [0052]    The phrase “substantially maintained at the given high voltage level” may include maintained at the exact given high voltage level but may also allow small deviations from the given high voltage level. A small deviation may be, for example, a deviation that does not exceed 1-5 percent of the given high voltage level. 
         [0053]    When the high voltage inspection system  10  operates at the first operational mode—even if the substrate  20  is moved from one location to another—the substrate  20  is surrounded by the same high voltage environment. The top conductive unit  900 , the housing  320  and the chuck  330  may be substantially maintained at the given high voltage level. 
         [0054]    According to an embodiment, the chuck  330  is an electrostatic chuck that includes a positive electrode  331  and a negative electrode  332 . The positive and negative electrodes may be of any shape and size. The positive electrode  331  receives a positive electrode bias signal and the negative electrode  332  receives a negative electrode bias signal. The positive electrode bias signal and/or the negative electrode bias signal may deviate from the given high voltage level in order to allow the chuck  330  to apply an electromagnetic chucking force on the substrate  20 . 
         [0055]    Surrounding the substrate  20  by the same high voltage environment may dramatically reduce the probability of high voltage breakdowns. 
         [0056]    The vacuum chamber  700  may be grounded (or at least maintained in a low voltage). 
         [0057]    The top conductive unit  900  is mechanically connected to a vacuum chamber cover  710  and is electrically insulated from the vacuum chamber cover  710  by a top insulating interface that includes top insulators  960 . 
         [0058]    Each top insulator  960  may include a set of coaxial insulating rings of descending size. Higher rings of the set have a smaller size. Each top insulator reduces creepage. 
         [0059]    The top conductive unit  900  receives high voltage bias signals through a second feedthrough module  622  positioned at the cover of the vacuum chamber. 
         [0060]    The insulating module  200  is positioned on top of a base  110 . Base  110  is positioned above X-Y stage  100 . 
         [0061]    The bottom of the bottom conductive shield  310  may be smooth and face the upper surface of base  110 . The upper surface of base  110  may also be smooth. 
         [0062]    A bottom insulating interface may include a bottom insulator that mechanically couples the base  110  to the bottom conductive shield  310  and also electrically insulates the base  110  from the bottom conductive shield  310 . 
         [0063]    The base  110  may be maintained at a low voltage while the bottom conductive shield  310  is substantially maintained at the given high voltage level. 
         [0064]    An upper surface of base  110  faces the bottom surface of the bottom conductive shield  310 . In order to reduce the chances of a formation of an arc between the base  110  and the bottom conductive shield  310 , the upper surface of the base  110  and the bottom surface of bottom conductive shield  310  may be smooth. 
         [0065]    Each bottom insulator  410  may include a set of coaxial insulating rings of ascending size. Lower rings of the set have a smaller size. Each bottom insulator reduces creepage. 
         [0066]    According to an embodiment, the insulating module  200  receives four cables. A first cable conveys a test signal that is sent to the chuck  330  in order to determine if there is a Ohmic contact between the chuck  330  and the substrate  20 . The test signal may be provided from test circuit  640  that is positioned outside the vacuum chamber. 
         [0067]    A second cable may convey a bias signal of the given high voltage level. This bias signal may be provided to one or more of the housing  320 , the bottom conductive shield  320  and the upper shield  340 . The housing  320 , the bottom conductive shield  320  and the upper shield  340  are electrically coupled to each other by means of conductors, mechanical coupling and the like. 
         [0068]    Third and fourth cables convey the positive electrode bias signal and the negative electrode bias signal, respectively. 
         [0069]    It is noted that the number of cables may differ from four, and that more than a single high bias voltage signal may be provided to the housing  320 , the bottom conductive shield  320  and/or the upper shield  340 . 
         [0070]      FIG. 2  is a cross sectional view of a substrate  20  and a high voltage inspection system  10  according to an embodiment. 
         [0071]    Some of the components of  FIG. 1  have been removed for brevity of explanation. 
         [0072]    The high voltage inspection system  10  of  FIG. 2  includes an optical microscope  510  that is configured to direct a light beam  512  towards the substrate  20 . The light beam  512  propagates through a window formed in the cover of the vacuum chamber and through an aperture formed in the top conductive module  900 . The optical microscope  510  and the electron optics  500  are spaced apart from each other. According to an embodiment, the fields of view of the optical microscope  510  and the electron optics  500  are spaced apart from each other. 
         [0073]      FIG. 3  is a top view of a top conductive module  900 , an optical microscope  510 , electron optics  500  and different positions of the housing according to various embodiments. 
         [0074]    Assuming that each point of the substrate  20  should be imaged by the electron optics  500 , the housing  320  should move between different positions. The rear-leftmost position of the housing  320  is denoted Position A  321 . The rear-rightmost position of the housing  320  is denoted Position B  322 . The front-leftmost position of the housing  320  is denoted Position C  323 . The front-rightmost position of the housing  320  is denoted Position D  324 . 
         [0075]    The position of the substrate  20  when imaged by the optical microscope is denoted Position E  325 . 
         [0076]      FIG. 3  illustrates that in all of the positions of the housing  320 , the top conductive module  900  may be directly above the housing (and the substrate  20 ). The phrase “directly above” means that the a projection of the top conductive module  900  on the plane of the substrate  20  when the projection lines are vertical “falls” on the substrate  20 . 
         [0077]    Therefore, during the first operational mode of the high voltage inspection system, the substrate  20  will see the same high voltage environment. 
         [0078]      FIG. 4  illustrates the high voltage inspection system  10  according to an embodiment. 
         [0079]    The high voltage inspection system  10  includes interferometer window  652 , vacuum chamber  700 , a vacuum chamber cover  710 , vacuum chamber sidewalls  780  and  782 , Z-axis stages  720 , inspection system base  730 , support structures  740 , vacuum pump  750 , dumping unit  760  and vacuum chamber opening  770 . 
         [0080]    The vacuum chamber is supported by support structures  740 . In  FIG. 4  the support structures  740  have a cylindrical shape although other shapes may be used. The support structures  740  are positioned on the inspection system base  730 . Any other frames of supporting structures may be provided. The support structures  740  may include or may be mechanically coupled to shock absorbers or damping units. 
         [0081]    Vacuum pump  750  may introduce a desired vacuum level within the vacuum chamber. The vacuum may be introduced via one or more gas conduits (not shown) that enter the vacuum chamber. Vibrations generated by the vacuum pump  750  may be dumped by dumping unit  760 . 
         [0082]    The Z-axis stages  720  are positioned outside the vacuum chamber, are mechanically coupled to the vacuum chamber cover  710 , and are configured to elevate the vacuum chamber cover  710  (thereby opening the vacuum chamber) or to lower the vacuum chamber cover  710  (thereby sealing the vacuum chamber). There may be a sealing mechanism between the vacuum chamber cover  710  and the sidewalls  780  and  782  of the vacuum chamber. 
         [0083]    The vacuum chamber opening  770  may be a part of a load lock mechanism for inserting the substrate in the vacuum chamber and for extracting the substrate  20  from the vacuum chamber. 
         [0084]      FIG. 5  illustrates the vacuum chamber  700  and the top surface  102  of the X-Y stage. The top surface  102  is not smooth and is not exposed to the bottom conductive shield  310  in some embodiments. 
         [0085]      FIG. 6  illustrates the base  110  and bottom insulators  410  according to an embodiment. 
         [0086]    The base  110  may include a smooth upper surface  116 , a base insulating unit recess  114  and a base cable recess  112 . 
         [0087]    A cable guide (denoted  90  in  FIG. 8 ) is placed on base cable recess  112 . Insulating module  200  is placed on base insulating unit recess  114 . 
         [0088]    Bottom insulators  410  are connected between the smooth upper surface  116  and the bottom surface of the bottom conductive shield  310 . 
         [0089]      FIG. 7  illustrates top surface  102 , base  110  and bottom insulators  410  according to an embodiment. 
         [0090]    The base  110  may be positioned above the top surface  102  (of the X-Y stage) and conceal the top surface  102  from the bottom conductive shield  310 . 
         [0091]      FIG. 8  illustrates a lower part  270  of a housing of the insulating module  200  and some components of the insulating module  200  according to an embodiment. 
         [0092]    The lower part  270  of the housing of the insulating module  200  is supported by the base insulating unit recess  114 . 
         [0093]      FIG. 8  also illustrates various components of the insulating module such as resistors, creepage reduction elements, input ports and a output ports. For brevity of explanation, the various components are numbered in  FIGS. 14 and 15 . 
         [0094]      FIG. 9  illustrates a cover of the housing of the insulating module  200 , cables  281 ,  282 ,  283  and  284 , lower plate  272 , upper plate  273  and terminals  291 ,  292 ,  293  and  294  according to an embodiment. 
         [0095]    Holes may be formed in cover  270 . Cables  281 ,  282 ,  283  and  284  from the output ports illustrated in  FIG. 8  may pass through the holes and be connected to the inputs of terminals  291 ,  292 ,  293  and  294 . Terminals  291 ,  292 ,  293  and  294  are secured to upper plate  273  that is positioned above (and connected to) lower plate  272 . Lower plate  272  is secured to cover  270 . 
         [0096]    Cables  281 ,  282 ,  283  and  284  convey (a) the test signal that is sent to the chuck  330  in order to determine if there is a Ohamic contact between chuck  330  and substrate  20 , (b) the bias signal of the given high voltage level, (c) the positive electrode bias signal, and (d) the negative electrode bias signal, respectively. 
         [0097]      FIG. 10  illustrates the X-Y stage  100 , the base  110 , the bottom insulators  410 , the bottom conductive shield  310  and the housing  320  according to an embodiment. 
         [0098]      FIG. 10  illustrates that the bottom conductive shield  310  is positioned below the housing  320  and above the bottom insulators  410  and the base  110 . 
         [0099]    The bottom conductive shield  310  includes an aperture that extends through the upper plate  273 . 
         [0100]    The housing  320  includes an aperture  326 . Electrical cables that extend from one or more terminals  291 ,  292 ,  293  and  294  may pass through the aperture  326  and/or the aperture formed in the bottom conductive shield  310 . 
         [0101]    The housing  320  includes external sidewall  324  that may be coated by light reflecting material to form mirrors. 
         [0102]    The housing  320  is illustrated as including a recess  321  on which the chuck  330  may be mounted. The recess  321  is surrounded by internal sidewall  322  that face the chuck  330  when the chuck is positioned on housing  320 . 
         [0103]    External sidewalls  342  may be slightly higher than the internal sidewalls. The external sidewalls  324  may end with an upper surface  325 . The internal sidewalls  322  may end with upper surface  323 . 
         [0104]      FIG. 11  illustrates the chuck  330 , the housing  320 , the bottom conductive shield  310  and the bottom insulators  410  according to an embodiment. 
         [0105]    The chuck  330  is positioned within the recess  321  of  FIG. 10 . The chuck  330  may not contact the internal sidewalls  322  of  FIG. 10 . Two chuck recesses  334  and  335  are shaped and sized to fit end effectors that supply the substrate  20  to the chuck  330 . The upper surface of the chuck  330  is only exposed to the high voltage environment and thus can be unsmooth. 
         [0106]      FIG. 12  illustrates the upper shield  340 , the chuck  330 , the housing  320 , the bottom conductive shield  310  and the bottom insulators  410  according to an embodiment. 
         [0107]    The upper shield  340  covers the upper parts of the housing  320 . The upper shield  340  is electrically conductive and protects the housing  320  from mechanical damages. 
         [0108]      FIG. 13  illustrates the top conductive module  900  according to an embodiment. 
         [0109]    The top conductive module  900  is illustrated as including an electron lens  910  that has an aperture  912  through which the electron beam ( 502  of  FIG. 1 ) passes. 
         [0110]    The top conductive module  900  also illustrates four additional conductive unit segments  920 ,  930 ,  940  and  950 . 
         [0111]    The segmenting of the top conductive module  900  may ease the installation and the carrying of the top conductive module  900 . 
         [0112]    The electron lens  910  may be fed by electron lens supply module  990  that is configured to introduce a difference between an electric potential of the electron lens and the high voltage level. 
         [0113]    The top conductive module can be made of a ceramic material. 
         [0114]      FIG. 14  includes a perspective view and a cross-sectional view of a resistor  220  having a first port  221 , a second port  222  and a creepage reduction element  223  according to an embodiment.  FIGS. 15 and 16  further illustrate the insulating module  200  according to an embodiment. 
         [0115]    The first port  221  is connected to an input port  224  of the insulating module  250 . The input port  224  is electrically coupled to a first cable  251 . 
         [0116]    The second port  222  is connected to an output port  225  of the insulating module  250 . The output port  225  is electrically coupled to cable  281  of  FIG. 9 . 
         [0117]    Resistor  220  may be completely surrounded by creepage reduction element  223 . 
         [0118]    In  FIG. 14 , the creepage reduction element  223  includes multiple insulating rings of alternating radiuses. Other arrangements of rings of different sizes may be used. 
         [0119]    The resistors may limit the current that flows through cables  250  if an arc occurs within the vacuum chamber. 
         [0120]    One or more plasma openings may be positioned in any location within the vacuum chamber and allow plasma from an external plasma source to enter the vacuum chamber and to clean at least selected elements of the system. 
         [0121]    In the foregoing specification, embodiments have been described with reference to specific examples. It will, however, be evident that various modifications and changes may be made therein without departing from the broader spirit and scope of the invention as set forth in the appended claims. 
         [0122]    Moreover, the terms “front,” “back,” “top,” “bottom,” “over,” “under” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments described herein are, for example, capable of step in other orientations than those illustrated or otherwise described herein. 
         [0123]    The connections as discussed herein may be any type of connection suitable to transfer signals from or to the respective nodes, units or devices, for example via intermediate devices. Accordingly, unless implied or stated otherwise, the connections may be, for example, direct connections or indirect connections. The connections may be illustrated or described in reference to being a single connection, a plurality of connections, unidirectional connections, or bidirectional connections. However, different embodiments may vary the implementation of the connections. For example, separate unidirectional connections may be used rather than bidirectional connections and vice versa. Also, a plurality of connections may be replaced with a single connection that transfers multiple signals serially or in a time multiplexed manner. Likewise, single connections carrying multiple signals may be separated out into various different connections carrying subsets of these signals. Therefore, many options exist for transferring signals. 
         [0124]    Although specific conductivity types or polarity of potentials have been described in the examples, it will be appreciated that conductivity types and polarities of potentials may be reversed. 
         [0125]    Each signal described herein may be designed as positive or negative logic. In the case of a negative logic, the signal is active low where the logically true state corresponds to a logic level zero. In the case of a positive logic, the signal is active high where the logically true state corresponds to a logic level one. Note that any of the signals described herein may be designed as either negative or positive logic signals. Therefore, in alternate embodiments, those signals described as positive logic signals may be implemented as negative logic signals, and those signals described as negative logic signals may be implemented as positive logic signals. 
         [0126]    Furthermore, the terms “assert” or “set” and “negate” (or “deassert” or “clear”) are used herein when referring to the rendering of a signal, status bit, or similar apparatus into its logically true or logically false state, respectively. If the logically true state is a logic level one, the logically false state is a logic level zero. And if the logically true state is a logic level zero, the logically false state is a logic level one. 
         [0127]    Those skilled in the art will recognize that the boundaries between logic blocks are merely illustrative and that alternative embodiments may merge logic blocks or circuit elements or impose an alternate decomposition of functionality upon various logic blocks or circuit elements. Thus, it is to be understood that the architectures depicted herein are merely exemplary, and that in fact many other architectures may be implemented which achieve the same functionality. 
         [0128]    Any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality may be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected,” or “operably coupled,” to each other to achieve the desired functionality. 
         [0129]    Furthermore, those skilled in the art will recognize that boundaries between the above described steps are merely illustrative. The multiple steps may be combined into a single step, a single step may be distributed in additional steps and steps may be executed at least partially overlapping in time. Moreover, alternative embodiments may include multiple instances of a particular step and the order of steps may be altered in various other embodiments. 
         [0130]    Also for example, in one embodiment, the illustrated examples may be implemented as circuitry located on a single integrated circuit or within a same device. Alternatively, the examples may be implemented as any number of separate integrated circuits or separate devices interconnected with each other in a suitable manner. 
         [0131]    However, other modifications, variations and alternatives are also possible. The specifications and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense. 
         [0132]    In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word ‘comprising’ does not exclude the presence of other elements or steps then those listed in a claim. Furthermore, the terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an.” The same holds true for the use of definite articles. Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage. 
         [0133]    While certain features have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.