Patent Publication Number: US-2022238343-A1

Title: Singulation of silicon carbide semiconductor wafers

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 15/974,984, filed May 9, 2018, which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     This description relates to singulation of die from silicon carbide (SiC) semiconductor wafers. 
     BACKGROUND 
     Singulation is a process of reducing a semiconductor wafer that includes multiple die of integrated circuits to form individual semiconductor chips. For example, singulation semiconductor die from a silicon wafer may be performed using a water-cooled saw with diamond-tipped teeth. Alternatively, the singulation may be performed using a laser ablation tool. 
     SUMMARY 
     In one general aspect, a method of singulating a silicon carbide (SiC) semiconductor wafer can include defining a cut within the silicon carbide (SiC) semiconductor wafer by performing a partial dicing operation where the SiC semiconductor wafer is aligned along a plane and the cut has a depth less than a first thickness of the SiC semiconductor wafer. The cut is aligned along a vertical direction orthogonal to the plane such that a portion of the SiC semiconductor wafer has a second thickness that extends between a bottom of the cut and an outer surface of the SiC semiconductor wafer. The method can further include defining a cleave, by performing a cleaving operation, through the portion of the SiC semiconductor wafer having the second thickness. The cleave can be aligned with the cut and extending to the outer surface of the SiC semiconductor wafer. 
     In another general aspect, a system can include a wafer chuck, the wafer chuck being configured to receive a SiC semiconductor wafer thinned to a first thickness, the thinned SiC semiconductor wafer having a surface aligned along a plane. The system can also include a dicing apparatus configured to perform a partial dicing operation on the SiC semiconductor wafer to define a cut within the SiC semiconductor wafer, the cut having a depth less than the first thickness of the SiC semiconductor wafer, the cut being aligned along a vertical direction orthogonal to the plane such that a portion of the SiC semiconductor wafer has a second thickness that extends between a bottom of the cut and an outer surface of the SiC semiconductor wafer. The system can further include a cleaving apparatus, the cleaving apparatus being configured to perform a cleaving operation, through the portion of the SiC semiconductor wafer having the second thickness, along the vertical direction to define a cleave, the cleave being aligned with the cut and extending to the outer surface of the SiC semiconductor wafer. 
     In another general aspect, a method can include thinning a silicon carbide (SiC) a semiconductor wafer to a thickness, the thinned SiC semiconductor wafer having a surface aligned along a plane. The method can also include performing a partial dicing operation on the SiC semiconductor wafer to define a cut in the SiC semiconductor wafer through a first portion of the thickness of the SiC semiconductor wafer, the cut aligned along a vertical direction orthogonal to the plane such that a portion of the SiC semiconductor wafer has a second thickness that extends between a bottom of the cut and an outer surface of the SiC semiconductor wafer, the cut also having a first width in a direction parallel to the plane. The method can further include performing a cleaving operation to define a cleave having a second width less than the first width, the cleave aligned with the vertical cut and through a second portion of the thickness of the SiC semiconductor wafer. 
     The details of one or more implementations are set forth in the accompa-nying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a diagram that illustrates an example method for singulating a silicon carbide (SiC) semiconductor wafer into die. 
         FIGS. 1B and 1C  are diagrams that illustrate a portion of a SiC semiconductor wafer that correspondence with the method shown in  FIG. 1A . 
         FIG. 2A  is a diagram that illustrates a cross-sectional view of an example SiC semiconductor wafer after being thinned to a target thickness for singulation. 
         FIG. 2B  is a diagram that illustrates a cross-sectional view of the SiC semiconductor wafer after backmetal deposition. 
         FIG. 2C  is a diagram that illustrates a cross-sectional view of the SiC semiconductor wafer after a partial dicing operation. 
         FIG. 2D  is a diagram that illustrates a cross-sectional view of the SiC semiconductor wafer after a cleaving operation. 
         FIG. 2E  is a diagram that illustrates a cross-sectional view of a portion of an example die of the SiC semiconductor wafer after the cleaving operation. 
         FIG. 3A  is a diagram that illustrates an example cutting apparatus for cutting the SiC semiconductor wafer through a first portion of a thickness of the SiC semiconductor wafer. 
         FIG. 3B  is a diagram that illustrates an example cleaving apparatus for cleaving the SiC semiconductor wafer through a second portion of the thickness of the SiC semiconductor wafer. 
         FIG. 4A  is a diagram that illustrates an example cut and cleaved SiC semiconductor wafer. 
         FIG. 4B  is a diagram that illustrates a line drawing of a scanning electron microscope (SEM) picture of the example cut and cleaved SiC semiconductor wafer. 
         FIG. 5  is a flow chart that illustrates an example method of singulating a SiC semiconductor wafer into die according to the improved techniques described herein. 
     
    
    
     DETAILED DESCRIPTION 
     The implementations described herein are directed to methods and apparatus for singulation, in a desirable fashion, of semiconductor die from a silicon carbide (SiC) semiconductor wafer. For example, the singulation apparatus and methods described herein can singulate semiconductor die from a SiC semiconductor wafer with vertical sidewall cut profiles through the thickness of the SiC semiconductor wafer. The SiC semiconductor wafer can be referred to as a SiC wafer. 
     The singulation techniques described herein can include defining a cut within the SiC wafer using a cutting apparatus followed by cleaving of the SiC wafer with a cleaving apparatus. The cut can be defined through only a portion of a thickness of the SiC semiconductor wafer (to a specified depth that is less than an entire thickness of the SiC semiconductor wafer), and the cleaving can be performed through a remaining thickness of the SiC semiconductor wafer. 
     SiC devices have some advantages over traditional Si devices. For example, SiC has a bandgap that is about three times the bandgap of Si and can withstand far higher voltages and temperatures than Si-based devices. As another example, SiC-based devices having the same dimensions as a Si-based device can withstand approximately 10 times the electric field strength of a SiC-based device. Despite these advantages, the manufacturing techniques applied to SiC wafers cannot be applied in the same way to SiC wafers because SiC wafers have different properties (e.g., have different crystalline structure, is a harder material) than Si wafers. The improved methods and apparatus described herein are directed to processing of the SiC wafers in view of the unique properties of the SiC wafers. 
       FIG. 1A  is a diagram that illustrates an example method of singulating a SiC semiconductor wafer into die.  FIGS. 1B and 1C  are diagrams that illustrate a portion of a SiC wafer  130  that correspond with the method shown in  FIG. 1A . 
     As shown in  FIG. 1A  at block  110 , a cut is defined within a SiC semiconductor wafer through a portion of the SiC semiconductor wafer. For example, as shown in  FIG. 1B , a SiC semiconductor wafer  130  has a cut C 1  defined through a portion of a thickness A 1  by a cutting apparatus. The depth of the portion of the thickness A 1  is denoted in  FIG. 1B  as A 2 . As shown in  FIG. 1B , the depth A 2  is a fraction of the thickness A 1 . Cutting the SiC wafer through the full thickness A 1  may cause undesirable wear on a cutting apparatus. 
     As also shown in  FIG. 1A  at block  120 , the SiC wafer is cleaved along the cut through a remaining portion of the thickness of the SiC wafer. For example, as shown in  FIG. 1C , the SiC semiconductor wafer  130  is cleaved along cleave C 2  in addition to being cut along cut C 1 . The cleave C 2  has been added to the SiC semiconductor wafer  130  using a cleaving apparatus. The depth of the remaining portion of the thickness A 1  is denoted in  FIG. 1C  as depth A 3 . The singulation of the SiC semiconductor wafer  130  in this context is then the combination of a cutting operation that produced the cut C 1  and a cleaving operation that produced the cleave C 2 . 
     As shown in  FIG. 1C , the cleave C 2  is aligned with the cut C 1  along a vertical axis. Defining the cut C 1  and the cleave C 2  so that such alignment is achieved is non-obvious in a SiC semiconductor wafer. Performing a cleaving operation in conjunction with a cutting operation results in a vertical separation that is unexpected within a SiC semiconductor wafer. The methods and apparatus under which such alignment of the cut C 1  and the cleave C 2  is achieved in a SiC semiconductor wafer is further shown and described below. 
     Advantageously, the improved techniques (cutting and cleaving) reduce wear and tear on equipment use during the singulation process. Because SiC is a hard material (harder than silicon), a cut through a portion of a thickness rather than the entire thickness of a thinned (e.g., post-grinded) wafer may have an advantage of extending the life of cutting equipment used in the singulation process. Extending the life of the cutting apparatus can lower the overall cost of manufacturing the die from a SiC wafer. 
       FIGS. 2A through 2D  are diagrams that illustrate a process by which a SiC semiconductor wafer is singulated into semiconductor die.  FIGS. 2A through 2D  illustrate more details related to the method shown and described in connection with  FIGS. 1A through 1C . 
       FIG. 2A  illustrates thinning (e.g., grinding) of the SiC semiconductor wafer to a thickness,  FIG. 2B  illustrates backmetal deposition,  FIG. 2C  illustrates cutting the SiC wafer is cut to a portion of the thickness with a singulation tool, and  FIG. 2D  illustrates cleaving of the SiC wafer a cleaving tool. The process shown in  FIGS. 2A-2D  is shown in the order in which they are performed. In some implementations, the process shown in  FIGS. 2A-2D  is performed in a different order. For example, in some implementations, the backmetal deposition operation shown in  FIG. 2B  may be performed after the cutting operation shown in  FIG. 2C  but before the cleaving operation shown in  FIG. 2D . 
       FIG. 2A  is a diagram that illustrates an example SiC semiconductor wafer  200  after the SiC semiconductor wafer  200  has been ground to a specified thickness.  FIG. 2A  shows the SiC semiconductor wafer  200  as positioned in a coordinate system in which x denotes a horizontal direction (i.e., parallel to the surface  202  of the SiC semiconductor wafer  200 ) and y denotes a vertical direction (i.e., perpendicular to the surface  202  and in the direction of the thickness A 1  of the wafer  200 ). In the implementation shown in  FIG. 2A , the SiC semiconductor wafer  200  is disposed on a chuck  206  as the SiC wafer  200  is being thinned. During the thinning (e.g., grinding) process, at least some portion of the SiC wafer  200  is removed to reduce the thickness of the SiC wafer  200 . 
     In some implementations, the thickness A 1  of the SiC semiconductor wafer  200  is several hundred microns (m) (e.g., 250 μm, 300 μm, 500 μm). The thinning process illustrated in  FIG. 2A  is also configured to provide an essentially flat surface  202 . In some implementations, for example, the flatness of the surface  202  is within 1 μm and the surface roughness is less than 0.5 nm. 
     Also shown in  FIG. 2A  are die sections of the SiC semiconductor wafer  200 , including die sections  204 ( 1 ) and  204 ( 2 ). As shown in  FIG. 2A , the die sections have boundaries represented by dashed lines. Each die section represents a die after the singulation process has been completed. The boundaries between the die sections have a finite width to take into account the finite widths of the cut C 1  and the cleave C 2  used to produce separated dies. Each die section also has a boundary region known as a kerf. In some implementations, the kerf includes, for example, test and/or alignment patterns. In some implementations, each of the die sections is rectangular. In some implementations, each of the die sections has dimensions of about 10 mm×10 mm. In some implementations, each of the die sections has a smaller size (e.g., 5 mm×5 mm) or a larger size (e.g., 26 mm×32 mm). 
       FIG. 2B  is a diagram that illustrates an example SiC semiconductor wafer  210  after a backmetal deposition operation has been performed to produce a backmetal  214  that is coupled to (e.g., adheres) to the backside of the wafer  210 . In some implementations, the backmetal  214  deposited on the backside of the wafer  210  includes a film stack that includes silver, nickel, and/or tin. In some implementations, the thickness of each layer of the film stack is between 1.5 μm and 2.0 μm. In some implementations, the layers of the stack may include tantalum, copper, and/or aluminum. 
       FIG. 2C  is a diagram that illustrates an example SiC semiconductor wafer  220  after a cutting operation performed by a cutting tool to produce a cut C 1  in between die sections  204 ( 1 ) and  204 ( 2 ). As shown in  FIG. 2C , the cut C 1  is vertical (e.g., substantially vertical, aligned along direction y) and has a depth A 2  that is a portion of the thickness A 1  of the SiC semiconductor wafer  220 . 
     In some implementations, the cut C 1  has a width that can be determined by a specified width of kerfs of the die section separated by the cut C 1 . In some implementations, the width of the cut C 1  can be a few microns (e.g., 2 μm, 5 μm). In some implementations, the width of the cut C 1  can be more than a few microns (e.g., between 20 μm to 50 μm). Also shown in  FIG. 2C  is the backmetal  214  deposited on the backside of the wafer  220 . 
     In some implementations, the cut C 1  has a uniform cross-section through the portion A 2  even though the cut C 1  is still aligned with the vertical direction. In some implementations, the cut C 1  has a nonuniform cross-section (e.g., a tapered cross-section, a bulging cross-section, and the like). For example, when a cutting apparatus (see apparatus  310  in  FIG. 3A ) includes a laser ablation tool, the distribution of laser light irradiance (i.e., energy density) through the portion A 2  may vary with the vertical direction because the distribution of light for a tightly focused beam varies through the direction of propagation of the light. 
       FIG. 2D  is a diagram illustrating an example wafer  230  after both the cutting operation and cleaving operation have been performed. Shown in  FIG. 2D  are the cut C 1  resulting from a cutting operation and a cleave C 2  resulting from a cleaving operation that are both aligned with respect to the vertical (y) axis. As shown in  FIG. 2D , the cut C 1  is aligned with the cleave C 2 . As shown in  FIG. 2D , the cleave C 2  extends from the cut C 1 . 
     As shown in  FIG. 2D , the cleave C 2  has a smaller width than the cut C 1 . In some implementations, the cut C 1  can have a width that is more than 5 times a width of the cleave C 2 . For example, in some implementations, the cut C 1  can have a width between 20 μm to 50 μm, and the cleave C 2  has a width of between 3 μm to 5 μm. This difference between the widths of the cut C 1  and the cleave C 2  is discussed in further detail with respect to at least  FIG. 2E . 
     In some implementations, the cut C 1  has a uniform cross-section (e.g., profile) along the depth A 2  of the cut C 1 . For example, sidewalls of the cut C 1  can be vertical and parallel between die sections  204 ( 1 ) and  204 ( 2 ). In some implementations, the cut C 1  has a nonuniform cross-section along the depth A 2  of the cut C 2  (e.g., a tapered cross-section and the like resulting from the cleaving operation). 
     In some implementations, the cleave C 2  has a uniform cross-section (e.g., profile) along the depth A 3  of the cleave C 2 . For example, sidewalls of the cleave C 2  between can be vertical and parallel between die sections  204 ( 1 ) and  204 ( 2 ). In some implementations, the cleave C 2  has a nonuniform cross-section along the depth A 3  of the cleave C 2  (e.g., a tapered cross-section and the like resulting from the cleaving operation). 
       FIG. 2E  is a diagram illustrating enlarged example view of die  254 ( 1 ) and  254 ( 2 ) (corresponding to die sections  204 ( 1 ) and  204 ( 2 )) resulting from the process illustrated in  FIGS. 2A-2D . As mentioned above, the cut has a larger width W 1  than the width of the cleave W 2 . Accordingly, a gap W 3  (e.g., a step) having width about equal to (W 1 −W 2 )/2. The gap W 3  results in a step in the die  254 ( 1 ) of width (W 1 −W 2 )/2. As shown in  FIG. 2E , the sidewall associated with the cut is vertical (e.g., substantially vertical) and the sidewall associated with the cleave is vertical (e.g., substantially vertical). 
       FIG. 2E  illustrates an example cross-sectional shape (e.g., profile) of a cut and a cleave, however, the cut and the cleave can have different cross-sectional shapes). For example, in some implementations, the sidewall of a cut can be aligned within a same plane as a sidewall of a cleave (instead of being offset as shown in  FIG. 2E ). 
       FIGS. 3A and 3B  are diagrams that illustrate an example system for performing singulation of die from a SiC semiconductor wafer  130 . The system includes a cutting apparatus  310  for performing a cutting operation on a portion of a SiC semiconductor wafer  210 . The system also includes a cleaving apparatus  320  for performing a cleaving operation on the SiC semiconductor wafer  220  after the cutting operation has been performed. The result of the cutting operation and the subsequent cleaving operation, when performed according to the improved techniques described herein, is a set of SiC semiconductor dies having vertical sidewalls (e.g., substantially vertical sidewalls). 
     As shown in  FIG. 3A , the cutting apparatus  310  is configured to perform a cutting operation between the die sections of the SiC semiconductor wafer  210  to produce a set of cuts (e.g., cut C 1  in  FIGS. 2A-2D ) through a portion of the thickness of the SiC semiconductor wafer  130 . As shown in  FIG. 3A , the cutting apparatus  310  includes a controller  312  configured to control a cutting tool  340  for performing the cutting operation. 
     The cutting tool  340  is configured to cut the SiC semiconductor wafer  210  between die sections. In some implementations, the cutting tool  340  includes a mechanical saw blade. In some implementations, the saw blade is a nickel bond dicing blade. In some implementations, the saw blade is a hubbed or hubless resinoid blade. In some implementations, the saw blade is a metal sintered dicing blade. In some implementations, the saw blade is configured to produce cut widths of between about 15 μm and 75 μm. 
     In some implementations, the cutting tool  340  includes a laser ablation tool. Such a laser ablation tool performs a scribing operation to produce a cut through a portion of the thickness of the SiC semiconductor wafer  210  between the die sections. In some implementations, the cutting tool  340  includes a short-pulse laser and a focusing lens. The laser can be of any wavelength although it is advantageous that the laser has a short wavelength (e.g., a UV wavelength less than 400 nm). In some implementations, the laser ablation tool can produce cut widths between 10 μm and 50 μm. 
     The controller  312  is configured to control the cutting tool  340  such that a cut produced by the cutting tool  340  has a specified depth through a portion of the thickness of the SiC semiconductor wafer  210  and a specified width in the gap between the die sections. In some implementations, the controller  312  includes an electronic control component configured to move the cutting tool  340  over the SiC semiconductor wafer  210  according to a dwell schedule. In some implementations, when the cutting tool includes a mechanical saw blade, the electronic component is configured to position the saw blade along an axis normal to the surface of the SiC semiconductor wafer  210  such that the saw blade performs the cutting operation at a portion of the thickness of the SiC semiconductor wafer  210 . In some implementations, the controller  312  has a mechanical component configured to position the saw blade along the axis normal to the surface of the SiC semiconductor wafer  210 . In some implementations, when the cutting tool  340  includes a laser ablation tool, the controller  312  includes an electronic control component configured to adjust a power of the laser and/or a number of passes across the SiC semiconductor wafer  210  to produce a cut having a specified depth through the thickness of the SiC semiconductor wafer  210  and/or width. In some implementations, the electronic control component is configured to adjust a position of the focusing lens to produce the cut having a specified depth through the thickness of the SiC semiconductor wafer  210 . 
     Once the cutting operation has been performed by the cutting apparatus  310 , the SiC semiconductor wafer  210  becomes the cut semiconductor wafer  220  and the cut SiC semiconductor wafer  220  is transferred to the cleaving apparatus  320 . In some implementations, the transfer of the wafer  220  from the cutting apparatus  310  to the cleaving apparatus  320  is performed by a robotic wafer transfer device having an end effector that is magnetically attached to the wafer  210  during the transfer. 
     As shown in  FIG. 3B , the cleaving apparatus  320  is configured to perform a cleaving operation on the cut SiC semiconductor wafer  220  after the cutting operation has been performed on the SiC semiconductor wafer  210  to produce a cleave that results in separated die. As shown in  FIG. 3B , the cleaving apparatus  320  includes, for example, an impulse bar  360  configured to cleave the wafer  220  at a specified location below the cut C 1 . 
     The cleaving operation is made possible when the cut C 1  creates a stress concentration factor in the gap separating the die sections  204 ( 1 ) and  204 ( 2 ) of the wafer  220 . The cleaving operation causes the impulse bar  360  to cleave through the portion of the thickness of the cut SiC semiconductor wafer  220  below the cut upon an application of force by the impulse bar  360 . In some implementations, the pressure applied to the cut SiC semiconductor wafer  220  by the impulse bar can be between 300 kPa and 350 kPA. In some implementation, the pressure applied can be greater than 350 kPA or less than 300 kPa. In some implementations, such pressure is applied to the SiC semiconductor wafer  220  when the distance that the impulse bar  360  travels can be between 80 μm and 100 μm. In some implementation, the distance that the impulse bar  360  travels can be greater than 100 μm or less than 80 μm. In some implementations, the cleaving operation is performed by static bending, an anvil method, or a non-contact method that uses a vacuum chuck. 
     In some implementations, the cleave produced by the cleaving operation is aligned with the cut produced by the cutting operation performed by the cutting apparatus  310 . As is discussed in greater detail with respect to  FIG. 4A , this alignment depends on the portion A 2  of the thickness A 1  through which the cut is made. 
       FIG. 4A  is a diagram illustrating the SiC semiconductor wafer  230  that has been diced into the die  254 ( 1 ) and  254 ( 2 ) according to the improved techniques described above. As shown in  FIG. 3A , the SiC semiconductor wafer  230  has a cut C 1  and a cleave C 2  that results in a set of die, for example die  254 ( 1 ) and  254 ( 2 ). The cut C 1  has a depth A 2  that is a portion of the thickness A 1  of the SiC semiconductor wafer  230 , the cleave C 2  is aligned with the cut C 2  and both the cut C 1  and cleave C 2  are aligned along a vertical direction (e.g., substantially vertical direction). 
     The depth A 2  of cut C 1  into the thickness A 1  of the wafer  230  extends is formed (e.g., made) so that a subsequent cleave produces a cleave C 2  that is aligned with (e.g., aligned along the same direction, parallel to) the cut C 1 . Such an alignment of the cleave C 2  with the cut C 1  occurs when the portion A 2  is at least 65% of the thickness A 1  of the SiC wafer  230 . In some implementations, the portion A 2  is preferably between about 65% and 75% of the thickness A 1  of the SiC wafer  230 . In some implementations, the ratio of the portion A 2  to the portion A 3  is between about 2 and 3. 
     As described above, the situation illustrated in  FIG. 4A  with the cut C 1  and cleave C 2  both aligned with respect to the vertical (y) axis occurs when the portion A 2  of the thickness A 1  of the cut C 1  is about 65-75% of the thickness A 1 . If the portion A 1  is less than 65% of A 1 , then the resulting cleave S may not be aligned with the y axis and the cut C 1  but may rather be situated at a skewed angle with respect to the y axis. Such a skewed angle is not desirable because the die that result may not provide a properly operating device when in a module. When the portion is greater than 75%, the wear on the singulation tool used to perform the cutting operation may be too great to be economically viable in some applications. 
       FIG. 4B  is a line drawing that shows this aligned cut and cleave in scanning electron microscope (SEM) pictures  442  and  444 . SEM picture  442  shows a first die (e.g., die  254 ( 1 )) and the SEM picture  444  shows another die (e.g., die  254 ( 2 )). As shown in the SEM pictures  442  and  444 , the die resulting from the cut and cleave, as described above, have vertical sidewalls. 
       FIG. 5  is a flow chart illustrating a method  500  of performing a singulation of a SiC semiconductor wafer according to the improved techniques described above. 
     At  502 , a SiC semiconductor wafer (e.g., the wafer  200  of  FIG. 2A ) is thinned (e.g., grinded) to a first thickness (e.g., thickness A 1 ). A surface of the thinned SiC semiconductor wafer is aligned along a plane (e.g., surface  202  is aligned in the x-direction). 
     At  504 , a cut is defined within the SiC semiconductor wafer by performing a partial dicing operation (e.g., cut C 1  of  FIG. 2C ). The cut has a depth less than the first thickness to which the SiC semiconductor wafer is ground (e.g., portion A 2 ). The cut is aligned along a vertical direction orthogonal to the plane (e.g., the cut C 1  is aligned in the y-direction of  FIG. 2D ), the cut aligned such that a portion of the SiC semiconductor wafer has a second thickness that extends between a bottom of the cut and an outer surface of the SiC semiconductor wafer. 
     At  506 , a cleave is defined by performing a cleaving operation, through the portion of the SiC semiconductor wafer having the second thickness, along the vertical direction (e.g., cleave C 2  of  FIG. 2D ). The cleave is aligned with the cut and extending to the outer surface of the SiC semiconductor wafer. 
     A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the specification. 
     It will also be understood that when an element is referred to as being on, connected to, electrically connected to, coupled to, or electrically coupled to another element, it may be directly on, connected or coupled to the other element, or one or more intervening elements may be present. In contrast, when an element is referred to as being directly on, directly connected to or directly coupled to another element, there are no intervening elements present. Although the terms directly on, directly connected to, or directly coupled to may not be used throughout the detailed description, elements that are shown as being directly on, directly connected or directly coupled can be referred to as such. The claims of the application may be amended to recite exemplary relationships described in the specification or shown in the figures. 
     The various apparatus and techniques described herein may be implemented using various semiconductor processing and/or packaging techniques. Some embodiments may be implemented using various types of semiconductor processing techniques associated with semiconductor substrates including, but not limited to, for example, Silicon (Si), Gallium Arsenide (GaAs), Silicon Carbide (SiC), and/or so forth. 
     It will also be understood that when an element, such as a layer, a region, or a substrate, is referred to as being on, connected to, electrically connected to, coupled to, or electrically coupled to another element, it may be directly on, connected or coupled to the other element, or one or more intervening elements may be present. In contrast, when an element is referred to as being directly on, directly connected to or directly coupled to another element or layer, there are no intervening elements or layers present. 
     Although the terms directly on, directly connected to, or directly coupled to may not be used throughout the detailed description, elements that are shown as being directly on, directly connected or directly coupled can be referred to as such. The claims of the application may be amended to recite exemplary relationships described in the specification or shown in the figures. 
     As used in this specification, a singular form may, unless definitely indicating a particular case in terms of the context, include a plural form. Spatially relative terms (e.g., over, above, upper, under, beneath, below, lower, and so forth) are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. In some implementations, the relative terms above and below can, respectively, include vertically above and vertically below. In some implementations, the term adjacent can include laterally adjacent to or horizontally adjacent to. 
     While certain features of the described implementations have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled 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 scope of the implementations. It should be understood that they have been presented by way of example only, not limitation, and various changes in form and details may be made. Any portion of the apparatus and/or methods described herein may be combined in any combination, except mutually exclusive combinations. The implementations described herein can include various combinations and/or sub-combinations of the functions, components and/or features of the different implementations described. 
     In addition, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. In addition, other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. Accordingly, other embodiments are within the scope of the following claims.