Abstract:
Mechanical resonating structures, as well as related devices and methods of manufacture. The mechanical resonating structures can be microphones, each including a diaphragm and a piezoelectric stack. The diaphragm can have one or more openings formed therethrough to enable the determination of an acoustic pressure being applied to the diaphragm through signals emitted by the piezoelectric stack.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 14/034,986 filed Sep. 24, 2013 entitled MEMS MICROPHONE, which claims benefit of the priority of U.S. Provisional Patent Application No. 61/705,299 filed Sep. 25, 2012 entitled MEMS MICROPHONE. 
     
    
     TECHNICAL FIELD 
       [0002]    The present application relates generally to microphones, and more particularly to micro-electro-mechanical-systems (MEMS) microphones and methods of manufacturing MEMS microphones. 
       BACKGROUND 
       [0003]    A microphone is an acoustic-to-electric converter (e.g., a transducer or sensor) that converts sound (i.e., acoustic pressure) into an electrical signal. Microphones can operate using a number of techniques including electromagnetic induction (e.g., as used in dynamic microphones) and capacitance change (e.g., as used in condenser microphones). 
         [0004]    Many microphones being utilized today are condenser microphones, which typically feature a fixed electrode (also referred to herein as the “backplate”) in close proximity to a moveable electrode (also referred to herein as the “diaphragm”). The backplate is typically rigid and is necessary because condenser microphones use electrostatic (i.e., capacitive) transduction between the diaphragm and the backplate to convert acoustic pressure into an electrical signal. 
         [0005]    Condenser microphones typically use a small gap between the respective electrodes formed by the diaphragm and the backplate to achieve high signal-to-noise ratios (SNRs), frequently resulting in reliability challenges such as stiction. Such a small gap between the backplate and the diaphragm can also degrade the thermal-mechanical noise performance by damping the overall mechanical structure. Moreover, a DC bias between the backplate and the diaphragm is typically required to enable capacitive detection of motion. However, such a DC bias between the backplate and the diaphragm can be a significant source of power consumption. 
         [0006]    A further consideration is whether condenser microphones (e.g., micro-electro-mechanical-systems (MEMS) condenser microphones) can be configured with a top port package configuration (also referred to herein as the “top port configuration”) or a bottom port package configuration (also referred to herein as the “bottom port configuration”). In a top port configuration, a MEMS condenser microphone is typically soldered to a printed circuit board (PCB), and acoustic access to the MEMS condenser microphone is provided through a hole at the top of the package. In a bottom port configuration, acoustic access is provided through a hole in the bottom of the package. A bottom port configuration also generally requires a hole in the PCB to enable sound to reach the MEMS condenser microphone. Although such MEMS condenser microphones can be made in either a top or bottom port configuration, holes must typically be machined into the backplates, increasing fabrication complexity. 
       SUMMARY 
       [0007]    Mechanical resonating structures, as well as related devices and methods of manufacture, are described herein. The mechanical resonating structures described herein are discussed with respect to microphones. However, the exemplary embodiments described herein, or one or more features thereof, can be used with any other suitable devices, including speakers. 
         [0008]    One or more of the embodiments described herein can include a piezoelectric microphone having a membrane or diaphragm, and a piezoelectric stack. The membrane or diaphragm can have a configuration (e.g., through removal of material therefrom) that facilitates movement or vibration, including holes and/or trenches of various shapes and/or sizes. The membrane or diaphragm can be made from various material or combinations of material, such as silicon (Si), silicon dioxide (SiO 2 ), silicon nitride (SiN), and silicon carbide (SiC). As an example, the membrane or diaphragm can be an array of holes and/or an array of non-prismatic cantilevers. In one embodiment, the piezoelectric stack can be patterned so that the membrane is thinner in selected regions and the static capacitance is reduced. In another embodiment, a hole pattern can be selected to relieve or otherwise reduce stress of the membrane. In still another embodiment, the microphone can be formed without a backplate. 
         [0009]    The microphone can be formed in various configurations including, but not limited to, a top port package configuration (also referred to herein as the “top port configuration”) to obtain a top port wafer-level chip-scale package (WLCSP) microphone (featuring through-silicon vias (TSVs)), or a bottom port package configuration (also referred to herein as the “bottom port configuration”) to obtain a bottom port WLCSP microphone (featuring TSVs). In one embodiment, a technique can be utilized to maintain the structural integrity of the membrane throughout the fabrication process by providing temporary structural pillars to keep the membrane stiff. In another embodiment, arrays of the microphones can be placed on a single chip. 
         [0010]    Piezoelectricity offers high electromechanical coupling compared with electrostatic transduction, enabling superior or improved signal-to-noise ratios (SNRs) to be achieved with proper design. 
         [0011]    In one embodiment of the present application, a method can include obtaining a starting wafer, forming vias and a cavity in the starting wafer, and bonding a silicon-on-insulator (SOI) wafer to the starting wafer. The method can also include removing material from at least one of the SOI wafer and the starting wafer to create a released diaphragm, depositing a piezoelectric stack in proximity to the released diaphragm, etching diaphragm holes in the released diaphragm to create a MEMS wafer, bonding the MEMS wafer to an integrated circuit wafer, and exposing the MEMS wafer to the ambient environment. 
         [0012]    In another embodiment of the present application, a device can have a substrate, and a diaphragm over an opening in the substrate, wherein the diaphragm includes one or more openings therein. The diaphragm can also have a piezoelectric stack in proximity to the one or more openings, wherein the piezoelectric stack is connectable with a conductor for determining acoustic pressure applied to the diaphragm. 
         [0013]    In a further embodiment of the present application, a microphone device can have a substrate having an opening, and a piezoelectric stack over the opening in the substrate. The piezoelectric stack has one or more openings therein, wherein the piezoelectric stack is connectable with a conductor for determining acoustic pressure applied thereto. The microphone device does not include a backplate. The piezoelectric stack can comprise a first metal layer, a second metal layer, and a piezoelectric layer disposed therebetween. 
         [0014]    Other embodiments and features of the present application will become apparent from the following detailed description when considered in conjunction with the accompanying drawing figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The accompanying drawing figures, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments described herein and, together with the Detailed Description, explain these embodiments. In the drawing figures: 
           [0016]      FIGS. 1A-1C  show micro-electro-mechanical-systems (MEMS) microphones according to embodiments of the present application; 
           [0017]      FIG. 1D  shows a transducer stack that includes a compensating structure, for use in the MEMS microphones of  FIGS. 1A-1C ; 
           [0018]      FIGS. 2A-2M  show a process for manufacturing a MEMS microphone according to embodiments of the present application; 
           [0019]      FIGS. 3A-3J  show another process for manufacturing another MEMS microphone according to embodiments of the present application; 
           [0020]      FIGS. 4A-4G  show still another process for manufacturing still another MEMS microphone according to embodiments of the present application; 
           [0021]      FIG. 5  shows yet another MEMS microphone according to embodiments of the present application; and 
           [0022]      FIG. 6  shows a further MEMS microphone according to embodiments of the present application. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The disclosures of U.S. patent application Ser. No. 14/034,986 filed Sep. 24, 2013 entitled MEMS MICROPHONE, and U.S. Provisional Patent Application No. 61/705,299 filed Sep. 25, 2012 entitled MEMS MICROPHONE, are hereby incorporated herein by reference in their entirety. 
         [0024]    In the drawing figures, the same reference numbers identify identical or substantially similar elements or acts. The drawing figures illustrate particular embodiments for the purpose of describing the present application, and are not intended to be exclusive or limiting in any way. The drawing figures are schematic and are not intended to be drawn to scale. In the drawing figures, each identical or substantially similar component illustrated in various figures is represented by a single numeral or notation. For purposes of clarity, not every component is labeled in every drawing figure, nor is every component of each embodiment of the present application shown where illustration is not necessary to allow those of ordinary skill in the art to understand the present application. It should be understood that various combinations of the structures, components, materials, and/or elements, other than those specifically shown, are contemplated and are within the scope of the present application. 
         [0025]    Micro-electro-mechanical systems (MEMS) transducers are micrometer-scale transducers involving one or more mechanical elements. MEMS transducers can be used in various devices including devices for inertial sensing, pressure sensing, and filtering, devices that employ projection display technology, timing devices, or any other suitable devices. The exemplary embodiments also take into consideration whether a top port package configuration (also referred to herein as the “top port configuration”) or a bottom port package configuration (also referred to herein as the “bottom port configuration”) can be employed. In a top port configuration, a MEMS microphone is soldered to a printed circuit board (PCB), and acoustic access to the microphone is provided through a hole at the top of the package. In a bottom port configuration, access is provided through a hole in the bottom of the package. A bottom port configuration also generally requires a hole in the PCB to enable sound to reach the microphone. The exemplary embodiments are adaptable to either configuration so as to satisfy either requirement. 
         [0026]    The direct piezoelectric effect refers to the ability of a piezoelectric material to generate an electric dipole moment in response to (and proportional to) an applied stress. Thus, a piezoelectric microphone design generates stress in the piezoelectric film under the application of acoustic pressure. Two exemplary embodiments  102 ,  104  are illustrated in  FIGS. 1A and 1B , respectively, for a piezoelectric MEMS microphone. The embodiments  102 ,  104  share substantially the same sliced cross section  106 , which is illustrated in  FIG. 1C .  FIGS. 1A-1C  do not depict the package of the piezoelectric MEMS microphone, which is addressed later, but many different packages can be used with these designs. 
         [0027]    In  FIG. 1A , the mechanical element can be a silicon membrane or diaphragm  108  anchored around its perimeter  110  to a silicon substrate  112 . In one embodiment, the membrane  108  is single crystal silicon, but it may alternatively be polysilicon, silicon dioxide (SiO 2 ), silicon nitride (SiN), silicon carbide (SiC), or some combination of these materials in a multilayer stack. On top of the membrane  108 , a metal-piezoelectric-metal transducer stack  118  (see  FIG. 1C ) is deposited and patterned. The piezoelectric film of the transducer stack  118  may be made of various materials, including aluminum nitride (AlN), zinc oxide (ZnO), cadmium sulfide (CdS), quartz, lead titanate (PbTiO 3 ), lead zirconate titanate (PZT), lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), or any other suitable material. The metal of the transducer stack  118  may be aluminum (Al), molybdenum (Mo), titanium (Ti), chromium (Cr), ruthenium (Ru), gold (Au), platinum (Pt), AlSiCu, or any other suitable material. The patterning of the transducer stack  118  concentrates the stack at the perimeter  110  where most of the stress is generated. This provides at least two advantages: 1) the overall membrane  108  thickness decreases over most of the area, resulting in more deflection per unit acoustic pressure, and 2) the static capacitance of the transducer stack  118  is reduced or minimized, which results in a higher signal-to-noise ratio (SNR). However, other embodiments can be utilized which do not use this stack patterning. 
         [0028]    In one embodiment, the transducer stack  118  can have an active layer  120 , and a compensating structure including at least one of a first layer  122  and a second layer  124  coupled to the active layer  120 , as shown in  FIG. 1D . The first layer  122  can have a stiffness that increases with increasing temperature over at least a first temperature range. Likewise, the second layer  124  can have a stiffness that increases with increasing temperature over at least the first temperature range. As further shown in  FIG. 1D , the active layer  120  is disposed between the first layer  122  and the second layer  124 . The compensating structure may be configured to provide a desired stiffness variation of the mechanical resonating structure and/or frequency of operation variation of the mechanical resonating structure over a desired temperature range (e.g., an anticipated operational temperature range of the mechanical resonating structure) for one or more modes of vibration of interest. In some embodiments, the composition of the active layer  120  of the transducer stack  118  may be considered in configuring the compensating structure, as the composition of the active layer  120  may impact the stiffness variation of the active layer  120  with temperature, which is to be compensated by the compensating structure in some embodiments. 
         [0029]    According to one embodiment, the compensating structure may be configured to provide the mechanical resonating structure with a temperature coefficient of frequency (TCF) having an absolute value of less than approximately 1 ppm/K over a temperature range of at least 40° C. centered around room temperature (25° C.) for one or more modes of Lamb waves when the active layer  120  is formed of aluminum nitride (AlN). However, this is merely a non-limiting example provided for purposes of illustration. 
         [0030]    The embodiment  104  of  FIG. 1B  depicts a membrane or diaphragm  114  similar to  FIG. 1A , but with long slits etched through its thickness instead of holes. In effect, this embodiment  104  is an array of non-prismatic cantilevers  116  with the piezoelectric stack  118  covering the bases, again where stress is the highest. This embodiment can also reduce sensitivity to package stresses. 
         [0031]    In general, there is similar acoustic pressure across each of the cantilevers  116 . In one embodiment, stress across different cantilevers  116  or other regions of the diaphragm  114  can be compared, such as to confirm the accuracy of the stress detected. In another embodiment, the stress at different cantilevers  116  or regions of the diaphragm  114  can be compared to determine an angle or direction of the sound that is applying the acoustic pressure to the diaphragm  114 . In one embodiment, each region of the diaphragm  114  (e.g., the cantilevers  116 ) can be separately connected with wiring or a conductor (e.g., a conductor  214 ,  FIG. 2H , or a conductor  314 ,  FIG. 3G ) for detecting separate vibrations. In another embodiment, a single wire can be used for connecting with the various regions of the diaphragm  114 . 
         [0032]      FIGS. 2A-2M  show cross sections of an exemplary process flow to manufacture a microphone in a bottom port configuration of either type of embodiment  102 ,  104  (see  FIGS. 1A ,  1 B) described above (or other configurations) in a wafer-level chip-scale package (WLCSP), which has through-silicon vias (TSVs). In  FIG. 2A , a starting wafer  202  can be silicon. TSVs  204  (see  FIG. 2B ) can be formed in the starting wafer  202 , and a cavity  206  (see  FIG. 2C ) can be etched where the microphone is to be located. A silicon-on-insulator (SOI) wafer  208  (see  FIG. 2D ) can be bonded to the starting wafer  202  and ground, polished, and/or etched back to create a released diaphragm  210  (see  FIG. 2E ) made of silicon, or whatever material or material stack is transferred from the top of the SOI wafer  208 . A piezoelectric stack  212  (see  FIG. 2F ) can then be deposited, patterned, and etched (see  FIG. 2G ). Electrical connections  214 ,  217  and passivation  216  (see  FIG. 2H ) can be created using any suitable technique known to those skilled in micro-fabrication technology. Diaphragm holes  218  (see  FIG. 2I ) can be etched. Further, the resulting MEMS wafer  220  (see  FIG. 2J ) can be bonded to an integrated circuit (IC) wafer  222  (see  FIG. 2J ) using any suitable known metal bonding techniques. The MEMS wafer  220  can be ground from the backside to expose the TSVs  204  (see  FIG. 2K ), which can then be passivated and patterned with metal  224  (see  FIG. 2L ). The microphone including the released diaphragm  210  and the piezoelectric stack  212  (see  FIG. 2M ) can be exposed to the ambient environment through grinding, polishing, reactive ion etching (RIE), or some combination of the above. The microphone package can be soldered to a PCB or assembled in a multi-chip module (MCM) with the MEMS wafer facing down. 
         [0033]    A similar approach can be used to manufacture a microphone in a top port configuration, as depicted in  FIGS. 3A-3J . The fabrication process is substantially the same as depicted in  FIGS. 2A-2M  except that the TSVs are created in the IC wafer, not in the MEMS wafer. 
         [0034]    In  FIG. 3A , a starting wafer  302  can be silicon. A cavity  306  (see  FIG. 3B ) can be etched where the microphone is to be located. An SOI wafer  308  (see  FIG. 3C ) can be bonded to the starting wafer  302  and ground, polished, and/or etched back to create a released diaphragm  310  (see  FIG. 3D ) made of silicon, or whatever material or material stack is transferred from the top of the SOI wafer  308 . A piezoelectric stack  312  (see  FIG. 3E ) can then be deposited, patterned, and etched (see  FIG. 3F ). Electrical connections  314  and passivation  316  (see  FIG. 3G ) can be created using any suitable technique known to those skilled in micro-fabrication technology. Diaphragm holes  318  (see  FIG. 3H ) can be etched. Further, the resulting MEMS wafer  320  (see  FIG. 3I ) can be bonded to an integrated circuit (IC) wafer  322  (see  FIG. 3I ) using any suitable known metal bonding techniques. TSVs  304  (see  FIG. 3I ) can be created in the IC wafer  322 , and passivated and patterned with metal  324  (see  FIG. 3I ). The microphone including the released diaphragm  310  and the piezoelectric stack  312  (see  FIG. 3J ) can be exposed to the ambient environment through grinding, polishing, reactive ion etching (RIE), or some combination of the above. The microphone package can be soldered to a PCB or assembled in a multi-chip module (MCM). 
         [0035]    One potential issue in MEMS microphone manufacturing is that the membrane is often created early in the process (such as the processes of  FIGS. 2A-2M  and  3 A- 3 J), and may be susceptible to shock-induced stiction and/or breakage during the remaining portion of the process flow. To reduce the risk of stiction or other undesirable results of the manufacturing process,  FIGS. 4A-4G  illustrate a manufacturing process using one or more temporary support structures  402 , which can apply to either embodiments  102 ,  104  of  FIGS. 1A  and B without changing the principle of operation or manufacturing process. Here, the various elements depicted in  FIGS. 4A ,  4 B,  4 C,  4 D,  4 E,  4 F, and  4 G correspond to the matching elements depicted  FIGS. 2C ,  2 D,  2 E,  2 H,  2 I,  2 L, and  2 M, respectively, with the addition of the support structures  402  (see  FIGS. 4A-4G ). 
         [0036]    During the etch of the cavity  206  (see  FIG. 4A ), the support structures  402  (also referred to herein as “structural pillars”) can be defined. After bonding (see  FIG. 4B ) and grinding/polishing (see  FIG. 4C ), the membrane or diaphragm  210  can be propped up or otherwise supported by the structural pillars  402 , resulting in a dramatically stiffer membrane  210  (during the remaining portion of the manufacturing process) with superior mechanical robustness. After routing (see  FIG. 4D ) and release (see  FIG. 4E ), the structural pillars  402  can be removed by the hole  218  etch. Alternatively, they can remain intact to help the membrane  210  survive bonding and metallization (see  FIG. 4F ). During the final membrane exposure polish or etch (see  FIG. 4G ), the structural pillars  402  become released from their support and are free to move with the membrane  210 . Though the structural pillars  402  remain attached to the membrane  210  in the illustrated embodiment, they have little effect on its mechanical properties and can be tolerated during microphone operation. The structural pillars  402  can be of various shapes including pins, rings, or any other suitable shapes. 
         [0037]      FIG. 5  illustrates another embodiment  502  of the MEMS microphone. The various elements depicted in  FIG. 5  correspond to the matching elements depicted in  FIG. 4G , respectively, with the exception that the structural pillars  402  (see  FIG. 4G ) are removed and replaced with structural pillars  500  (see  FIG. 5 ), which are formed on the other side of the diaphragm  210 . In this embodiment  502 , the structural pillars  500  can help avoid reflection interference, as well as avoid stiction during the manufacturing process. 
         [0038]      FIG. 6  illustrates a further embodiment  602  of the MEMS microphone. The various elements depicted in  FIG. 6  correspond to the matching elements depicted in  FIG. 4G , respectively, with the exception that the structural pillars  402  (see  FIG. 4G ) are removed, and a backside cavity  600  is utilized to reduce or eliminate reflection interference. The use of the backside cavity  600  can depend on the operational parameters or the expected operating environment of the MEMS microphone where reflection interference may be a potential operational issue. 
         [0039]    In one or more of the embodiments depicted in  FIGS. 2M ,  3 J,  4 G,  5 , and  6 , a coating can be applied to the backside  213 ,  313 ,  413 ,  513 ,  613  of the diaphragm and/or the surface of the structure  215 ,  315 ,  415 ,  515 ,  615  opposing the backside  213 ,  313 ,  413 ,  513 ,  613 , respectively, of the diaphragm. The coating can be made of a material that reduces or eliminates stiction. 
         [0040]    The exemplary embodiments illustrate circular openings in the diaphragm and slits forming pie-shaped cantilever structures in the diaphragm. The exemplary embodiments can utilize various other shapes of openings through the diaphragm. The selection of the opening shapes can be based on a number of factors, such as the expected stress levels, amount of expected acoustic pressure, and so forth. In one embodiment, the cantilever structures can be rectangular-like structures in a parallel pattern. In another embodiment, the pattern resulting from the openings through the diaphragm can be a symmetrical pattern or an asymmetrical pattern. In another embodiment, the pattern resulting from the openings through the diaphragm can be an annular pattern, such as circular holes formed in concentric rings. 
         [0041]    The exemplary embodiment is described with respect to a three layer piezoelectric stack, but other piezoelectric stacks, including other numbers of layers can also be used with the exemplary embodiments. 
         [0042]    In one embodiment, the MEMS microphone can allow for direct vibration (and measurement) of the piezoelectric material (without the need for a separate diaphragm). For example, the piezoelectric stack can function as the diaphragm and can have one or more openings formed therethrough to facilitate vibration in response to the application of acoustic pressure. The one or more openings can be of various sizes, shapes, and configurations, including the cantilevers or circular openings. In this example, the stack can be a metal-piezoelectric-metal transducer stack. The piezoelectric film of the transducer stack may be made of various materials including aluminum nitride (AlN), zinc oxide (ZnO), cadmium sulfide (CdS), quartz, lead titanate (PbTiO 3 ), lead zirconate titanate (PZT), lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), combinations thereof, or some other material. The metal of the transducer stack may be aluminum (Al), molybdenum (Mo), titanium (Ti), chromium (Cr), ruthenium (Ru), gold (Au), platinum (Pt), AlSiCu, combinations thereof or some other material. 
         [0043]    In another embodiment, the piezoelectric stack can be formed in a shape other than a ring. For example, the piezoelectric stack can be formed over the diaphragm, and the cutting to form the desired openings and other structures can also be applied to the piezoelectric stack. 
         [0044]    In one or more of the exemplary embodiments, the piezoelectric layer for the piezoelectric stack can comprise quartz, LiNbO 3 , LiTaO 3 , aluminum nitride (AlN), or any other suitable piezoelectric material (e.g., zinc oxide (ZnO), cadmium sulfide (CdS), lead titanate (PbTiO 3 ), lead zirconate titanate (PZT), potassium niobate (KNbO 3 ), Li 2 B 4 O 7 , langasite (La 3 Ga 5 SiO 14 ), gallium arsenside (GaAs), barium sodium niobate, bismuth germanium oxide, indium arsenide, indium antimonide), either in substantially pure form or in combination with one or more other materials. In one or more exemplary embodiments, the piezoelectric layer can be formed along a first metal layer. In one or more exemplary embodiments, the piezoelectric layer can be formed along first and second metal layers, such as sandwiched between the metal layers or arranged in a different layer configuration. 
         [0045]    It should be understood that the various embodiments shown in the drawing figures are illustrative representations, and are not necessarily drawn to scale. Reference throughout the specification to “one embodiment” or “an embodiment” or “some embodiments” means that a particular feature, structure, material, or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the present application, but not necessarily in all embodiments. Consequently, appearances of the phrases “in one embodiment”, “in an embodiment”, or “in some embodiments” in various places throughout the specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments, including through combining of embodiments. 
         [0046]    Unless the context clearly requires otherwise, throughout the disclosure, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in a sense of “including, but not limited to”. Words using the singular or plural number also include the plural or singular number respectively. Additionally, the words “herein”, “hereunder”, “above”, “below”, and words of similar import refer to the present application as a whole and not to any particular portions of the present application. When the word “or” is used in reference to a list of two or more items, that word covers all of the following interpretations of the word: any of the items in the list; all of the items in the list; and, any combination of the items in the list. 
         [0047]    Having thus described several embodiments of the present application, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the disclosure. Accordingly, the foregoing description and drawing figures are by way of example only, and the invention should not be viewed as limited except as by the scope and spirit of the appended claims.