Abstract:
A pizeoresistive type Z-axis accelerometer is provided, including a substrate; a plurality of anchors formed over the substrate; a plurality of cantilever beams, wherein the cantilever beams include a piezoresistive material; and a proof mass, wherein the proof mass is suspended over the substrate by respectively connecting the proof mass with the anchors, and the accelerometer senses a movement of the proof mass by the piezoresistive material.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority of Taiwan Patent Application No. 100136886, filed on Oct. 12, 2011, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to motion sensors, and in particularly to a Z-axis accelerometer. 
     2. Description of the Related Art 
     Accelerometers have wide applications such as for inertial navigation systems, automotive safety, and missile control. Z-axis accelerometers can be used to control side air bags, vehicles and multi-axis sensing systems. Normally, z-axis accelerometers are fabricated using bulk micro-machined technology. 
     According to various operating mechanisms, several types of Z-axis accelerometers such as piezoresistive type accelerometers, piezoelectric type accelerometers, capacitive type accelerometers, thermal type accelerometers and tunneling current type accelerometers have been developed. 
     BRIEF SUMMARY OF THE INVENTION 
     An exemplary piezoresistive type Z-axis accelerometer comprises a substrate; a plurality of anchors formed over the substrate; a plurality of cantilever beams, wherein the cantilever beams comprise a piezoresistive material; and a proof mass, wherein the proof mass is suspended over the substrate by respectively connecting the proof mass with the anchors, and the accelerometer senses a movement of the proof mass by the piezoresistive material. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a schematic top view of a piezoresistive type Z-axis accelerometer according to an embodiment of the invention; 
         FIG. 2  is a schematic diagram showing a cross section taken along a line  2 - 2  in  FIG. 1 ; 
         FIG. 2A  is another schematic diagram showing a cross section taken along a line  3 - 3  in  FIG. 1 ; 
         FIG. 3  is a schematic diagram showing a cross section taken along a line  3 - 3  in  FIG. 1 ; 
         FIG. 4  is a schematic perspective view illustrating that the piezoresistive type Z-axis accelerometer in  FIG. 3  has sensed exterior accelerations; 
         FIG. 5  is a schematic top view of a piezoresistive type Z-axis accelerometer according to another embodiment of the invention; 
         FIG. 6  is a schematic cross section taken along a line  6 - 6  in  FIG. 5 ; 
         FIG. 7  is a schematic perspective view illustrating that the piezoresistive type Z-axis accelerometer in  FIG. 6  has sensed exterior accelerations; 
         FIG. 8  is a schematic top view of a piezoresistive type Z-axis accelerometer according to yet another embodiment of the invention; 
         FIG. 9  is a schematic cross section taken along a line  9 - 9  in  FIG. 8 ; 
         FIG. 10  is a schematic perspective view illustrating that the piezoresistive type Z-axis accelerometer in  FIG. 9  has sensed exterior accelerations; 
         FIG. 11  is a schematic top view of a piezoresistive type Z-axis accelerometer according to another embodiment of the invention; 
         FIG. 12  is a schematic cross section taken along a line  12 - 12  in  FIG. 11 ; 
         FIG. 13  is a schematic top view of a piezoresistive type Z-axis accelerometer according to yet another embodiment of the invention; and 
         FIG. 14  is a schematic cross section taken along a line  14 - 14  in  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
       FIG. 1  is a schematic top view of an exemplary piezoresistive type Z-axis accelerometer. Herein, the exemplary piezoresistive type Z-axis accelerometer is a piezoresistive type Z-axis accelerometer known by the inventors and is used as a comparative example to comment on the reliability problems found by the inventors, but is not used to restrict the scope of the invention. 
     As shown in  FIG. 1 , a schematic top view parallel with an X-Y plane of a substrate  100  is illustrated. The piezoresistive type Z-axis accelerometer comprises the substrate  100  and a support frame  102  formed over a portion of the substrate  100 , and the support frame  102  defines a cavity  112  within the support frame  102  over the substrate  100 . The substrate  100  can be, for example, a bulk silicon substrate, and the support frame  102  is illustrated as a rectangular configuration here, but is not limited thereto. The support frame may be formed as other polygonal configurations. 
     As shown in  FIG. 1 , a movable proof mass  104  is disposed within the cavity  112  and is suspended over the substrate  100 . The proof mass  104  is connected to a side of a cantilever beam  106  and is supported by thereof, and the other side not connecting to the proof mass of the cantilever beam  106  is embedded within the support frame  102  and disposed over an anchor  108  formed in the support frame  102 . 
     In addition, the piezoresistive type Z-axis accelerometer comprises a piezoresistive material layer  110  (illustrated with dotted line here) to function as a piezoresistor, and the piezoresistive material layer  110  is embedded in the cantilever beam  106  and further extends into a portion of the support frame  102 . 
     Moreover, three additional piezoresistors (not shown) are further provided and disposed in other portions of the substrate  100 , and these tree additional piezoresistors are electrically connected to the piezoresistive material layer  110  in the piezoresistive type Z-axis accelerometer shown in  FIG. 1  to form t a wheatstone bridge (not shown). 
     In  FIG. 2 , a schematic cross section taken along a line  2 - 2  in  FIG. 1  is illustrated. For the purpose of simplicity, only components such as the cantilever beam  106 , the piezoesistive material layers  110  and the support frame  102  are illustrated in  FIG. 2 . In one embodiment, the support frame  102  comprises an insulating layer  120 , a plurality of conductive layers  122 , a plurality of dielectric layers  124  and a topmost passivation layer  114  sequentially stacked over the substrate  100 . The conductive layer  122  and the dielectric layers  124  are interleaved with each other and are disposed between the insulating layer  120  and the passivation layer  114 . 
     The conductive layers  122  can be, for example, conductive layers comprising metals such as copper or aluminum, and the dielectric layers  124  can be, for example, intermetal dielectric (IMD) layers comprising dielectric materials such as silicon dioxide and silicon nitride. In another embodiment, the cantilever beam  106  may comprise a plurality of dielectric layers  124  and a piezoresistive material layer  110  composed of, for example, polysilicon materials in one of the dielectric layers  124  embedded within the cantilever beam  106 . The dielectric layers  124  in the cantilever beam  106  are simultaneously formed with the dielectric layers  124  in the support frame  102 , but a number of the dielectric layers  124  in the cantilever beam  106  is less than a number of the dielectric layer  124  in the support frame  102 . In yet another embodiment, a recess R may optionally be formed in the substrate  100  below the cavity  112 , and the recess R may partially extend below the support frame  102  to improve a sensitivity of the piezoresistive type Z-axis accelerometer, as shown in  FIG. 2A . 
     In  FIG. 3 , a schematic perspective diagram taken along a line  3 - 3  in  FIG. 1  is illustrated. For the purpose of simplicity, only components such as the passivation layer  114 , the cantilever beam  106 , the anchor  108 , the proof mass  104  and the substrate  100  are illustrated. The proof mass  104  is formed by stacking and interleaving one or a plurality of conductive layers  122  and the dielectric layers  124  together, and a region covered by the passivation layer  114  is substantially where the support frame  102  is. 
     Herein, the proof mass  104  is under a static status not sensing exterior stresses, such that the proof mass  104 , the cantilever beam  106 , and the piezoresistive material layer  110  in the cantilever beam  106  are substantially parallel with the X-Y plane of the substrate  100 . Numbers of the conductive layers  122  and the dielectric layers  124  in the proof mass  104  can be adjusted according to a need of a practical process and every two conductive layers  122  are isolated by one of the dielectric layers  124 . 
     As shown in  FIG. 4 , a schematic perspective view shows that the piezoresistive type Z-axis accelerometer of  FIG. 3  has sensed exterior accelerations. When the exterior accelerations are being sensed, the proof mass  104  performs inertia movements along a Z-axis direction in perpendicular to the X-Y plane, thereby causing deformation of the cantilever beam  106  and changing stress distribution over the cantilever beam  106 , such that a resistance of the piezoresistive material layer  110  in the cantilever beam  106  is changed. Therefore, a voltage at two ends of the wheatstone bridge (not shown) that electrically connects with the piezoresistive material layer  110  is changed and an acceleration along the Z-axis direction can be obtained by analyzing an output voltage from the wheatstone bridge by an instrument amplifier (not shown). 
     Nevertheless, the piezoresistive type Z-axis accelerometer shown in  FIGS. 1-4  has the following disadvantages. First, the proof mass  104  is connected to the anchor  108  or the support frame  102  by only a single cantilever beam  106  such that a sensitivity of the piezoresistive material layer  110  in the cantilever beam  106  may be too sensitive, thereby affecting a reliability of the piezoresistive type Z-axis accelerometer. Second, due to connections between the proof mass  104  with the anchor  108  or the support frame  102  are achieved by only one cantilever beam  106 , mechanical damages such as cracking may happen at the connection between the cantilever beam  106  and the anchor  108  or the support frame  102  as the number of times the proof mass  104  in the piezoresistive type Z-axis accelerometer is moved is increased, such that reliability thereof is affected. 
     Accordingly, the structure the piezoresistive type Z-axis accelerometer shown in  FIGS. 1-4  is modified to improve a sensitivity of the piezoresistor (i.e. the piezoresistive material layer  110 ) therein and a connection between the cantilever beam  106  and the anchor  108  or the support frame  102  to improve a reliability of the piezoresistive type Z-axis accelerometer. 
     In  FIG. 5 , a schematic top view of another exemplary piezoresistive type Z-axis accelerometer is illustrated. As shown in  FIG. 5 , the exemplary piezoresistive type Z-axis accelerometer is similar with that illustrated in  FIG. 1 , and a difference therebetween is that two sides of the proof mass  104  in this embodiment are respectively connected with a side of two individual cantilever beams  106   a  and  106   b , and the other side of the individual cantilever beams  106   a  and  106   b  not connecting with the proof mass  104  is respectively connected with one of the anchors  108   a  and  108   b  formed in the support frame  102 . Moreover, the piezoresistive type Z-axis accelerometer in this embodiment comprises two piezoresistive material layers  110   a  and  110   b  (illustrated with dotted line here) to function as two piezoresistors, and two piezoresistive material layers  110   a  and  110   b  are respectively embedded in one of the cantilever beams  106   a  and  106   b.    
     As shown in  FIG. 5 , the piezoresistive material layers  110   a  and  110   b  of the piezoresistive type Z-axis accelerometer can be connected in series to form a sensing resistor in a wheatstone bridge (not shown). In this embodiment, configurations of the anchors  108   a  and  108   b , the cantilever beams  106   a  and  106   b , and the piezoresistive material layers  110   a  and  110   b  are similar with the configurations of the anchor  108 , the cantilever beam  106  and the piezoresistive layer  110  shown in  FIGS. 1-4  and are not described and illustrated in detail here. 
     In  FIG. 6 , a schematic perspective diagram taken along a line  6 - 6  in  FIG. 5  is illustrated. For the purpose of simplicity, only components such as the passivation layer  114 , the cantilever beams  106   a  and  106   b , the anchors  108   a  and  108   b , the proof mass  104  and the substrate  100  are illustrated. The proof mass  104  is formed by stacking and interleaving one or a plurality of conductive layers  122  and the dielectric layers  124  together, and a region covered by the passivation layer  114  is substantially where the support frame  102  is. Herein, the proof mass  104  is under a static status not sensing exterior stresses, such that the proof mass  104 , the cantilever beams  106   a  and  106   b , and the piezoresistive material layers  110   a  and  110   b  are substantially parallel with the X-Y plane of the substrate  100 . 
     As shown in  FIG. 7 , a schematic perspective view shows that the piezoresistive type Z-axis accelerometer of  FIG. 6  has sensed exterior accelerations. When the exterior accelerations are being sensed, the proof mass  104  performs inertia movements along a Z-axis direction in perpendicular to the X-Y plane, thereby causing deformation of the cantilever beams  106   a  and  106   b , and changing stress distribution over the cantilever beams  106   a  and  106   b , such that a resistance of the piezoresistive material layers  110   a  and  110   b  respectively in the cantilever beams  106   a  and  106   b  is changed. Therefore, a voltage at two ends of the wheatstone bridge (not shown) that electrically connects with the piezoresistive material layers  110   a  and  110   b  is changed and an acceleration along the Z-axis direction can be obtained by analyzing an output voltage from the wheatstone bridge by an instrument amplifier (not shown). 
     Herein, the piezoresistive type Z-axis accelerometer shown in  FIGS. 5-7  has the following advantages when compared with the piezoresistive type Z-axis accelerometer shown in  FIGS. 1-4 . First, the proof mass  104  is connected to the different anchors  108   a  and  108   b  in the support frame  102  by a pair of cantilever beams  106   a  and  106   b , such that a sensitivity of the piezoresistor in the cantilever beam  106   a  (i.e. the piezoresistive material layer  110   a ) and a sensitivity of the piezoresistor in the cantilever beam  106   b  (i.e. the piezoresistive material layer  110   b ) can be controlled by the pair of the cantilever beams  106   a  and  106   b  and may not be too sensitive, thereby improving a reliability of the piezoresistive type Z-axis accelerometer. Second, due to connections between the proof mass  104  with the anchors  108   a  and  108   b  in the support frame  102  being achieved by the pair of cantilever beams  106   a  and  106   b , mechanical damages such as cracking may be reduced or not happened at the multiple connections between the cantilever beams  106   a  and  106   b  and the anchors  108   a  and  108   b  as the number of times the proof mass  104  in the piezoresistive type Z-axis accelerometer is moved is increased, such that a reliability thereof is improved. 
     In  FIG. 8 , a schematic top view of yet another exemplary piezoresistive type Z-axis accelerometer is illustrated. As shown in  FIG. 8 , the exemplary piezoresistive type Z-axis accelerometer is similar with that illustrated in  FIG. 1 , and a difference therebetween is that four sides of the proof mass  104  in this embodiment are respectively connected with a side of four individual cantilever beams  106   a ,  106   b ,  106   c  and  106   d , and the other side of the individual cantilever beams  106   a ,  106   b ,  106   c  and  106   d  not connecting with the proof mass  104  is respectively connected with one of the four anchors  108   a ,  108   b ,  108   c  and  108   d  formed in the support frame  102 . Moreover, the piezoresistive type Z-axis accelerometer in this embodiment comprises four piezoresistive material layers  110   a ,  110   b ,  110   c  and  110   d  (illustrated with dotted line here) to function as four piezoresistors, and this four piezoresistive material layers  110   a ,  110   b ,  110   c  and  110   d  are respectively embedded in one of the four cantilever beams  106   a ,  106   b ,  106   c  and  106   d . As shown in  FIG. 8 , the piezoresistive material layers  110   a ,  110   b ,  110   c  and  110   d  of the piezoresistive type Z-axis accelerometer can be connected in series to form a sensing resistor in a wheatstone bridge (not shown). In this embodiment, configurations of the anchors  108   a ,  108   b ,  108   c  and  108   d , the cantilever beams  106   a ,  106   b ,  106   c  and  106   d , and the piezoresistive material layers  110   a ,  110   b ,  110   c  and  110   d  are similar with the configurations of the anchor  108 , the cantilever beam  106  and the piezoresistive layer  110  shown in  FIGS. 1-4  and are not described and illustrated in detail here. 
     In  FIG. 9 , a schematic perspective diagram taken along a line  9 - 9  in  FIG. 8  is illustrated. For the purpose of simplicity, only components such as the passivation layer  114 , the cantilever beams  106   a ,  106   b  and  106   c , the anchors  108   a ,  108   b  and  108   c , the proof mass  104  and the substrate  100  are illustrated. The proof mass  104  is formed by stacking and interleaving one or a plurality of conductive layers  122  and the dielectric layers  124  together, and a region covered by the passivation layer  114  is substantially where the support frame  102  is. Herein, the proof mass  104  is under a static status not sensing exterior stresses, such that the proof mass  104 , the cantilever beams  106   a  and  106   b , and the piezoresistive material layers  110   a  and  110   b  are substantially parallel with the X-Y plane of the substrate  100 . 
     As shown in  FIG. 10 , a schematic perspective view shows that the piezoresistive type Z-axis accelerometer of  FIG. 9  has sensed exterior accelerations. When the exterior accelerations are being sensed, the proof mass  104  performs inertia movements along a Z-axis direction in perpendicular to the X-Y plane, thereby causing deformation of the cantilever beams  106   a ,  106   b  and  106   c , and changing stress distribution over the cantilever beams  106   a ,  106   b  and  106   c , such that a resistance of the piezoresistive material layers  110   a ,  110   b  and  110   c  respectively in the cantilever beams  106   a ,  106   b  and  106   c  is changed. Therefore, a voltage at two ends of the wheatstone bridge (not shown) that electrically connects with the piezoresistive material layers  110   a ,  110   b  and  110   b  is changed and an acceleration along the Z-axis direction can be obtained by analyzing an output voltage from the wheatstone bridge by an instrument amplifier (not shown). 
     Herein, the piezoresistive type Z-axis accelerometer shown in  FIGS. 8-10  has the following advantages when compared with the piezoresistive type Z-axis accelerometer shown in  FIGS. 1-4 . First, the proof mass  104  is connected to the different anchors  108   a ,  108   b ,  108   c  and  108   d  in the support frame  102  by four cantilever beams  106   a ,  106   b ,  106   c  and  106   d , such that a sensitivity of the piezoresistor in the cantilever beam  106   a  (i.e. the piezoresistive material layer  110   a ), a sensitivity of the piezoresistor in the cantilever beam  106   b  (i.e. the piezoresistive material layer  110   b ), a sensitivity of the piezoresistor in the cantilever beam  106   c  (i.e. the piezoresistive material layer  110   c ), and a sensitivity of the piezoresistor in the cantilever beam  106   d  (i.e. the piezoresistive material layer  110   d ) can be controlled by the pair of the cantilever beams  106   a ,  106   b ,  106   c  and  106   d  and may not be too sensitive, thereby improving a reliability of the piezoresistive type Z-axis accelerometer. Second, due to connections between the proof mass  104  with the anchors  108   a ,  108   b ,  108   c  and  108   d  in the support frame  102  being achieved by the four cantilever beams  106   a ,  106   b ,  106   c  and  106   b , mechanical damages such as cracking may be reduced or not happened at the multiple connections between the cantilever beams  106   a ,  106   b ,  106   c , and  106   b  and the anchors  108   a ,  108   b ,  108   c  and  108   b  as the number of times the proof mass  104  in the piezoresistive type Z-axis accelerometer is moved is increased, such that a reliability thereof is improved. 
     In the configurations of the piezoresistive type Z-axis accelerometer shown in  FIGS. 5-10 , a pair or two pairs of anchors  108   a ,  108   b ,  108   c  and  108   d  of a symmetrical structure and a pair or two pairs of the cantilever beams  106   a ,  106   b ,  106   c , and  106   d  of a symmetrical structure are formed therein. However, the piezoresistive type Z-axis accelerometer is not limited by the configurations and anchors and cantilever beams of asymmetrical structures can be also formed in a piezoresistive type Z-axis accelerometer. 
     In  FIG. 11 , a schematic top view of another exemplary piezoresistive type Z-axis accelerometer is illustrated. As shown in  FIG. 11 , the exemplary piezoresistive type Z-axis accelerometer is similar with that illustrated in  FIG. 5 , and a difference therebetween is that two adjacent sides of the proof mass  104  in this embodiment are respectively connected with a side of two individual cantilever beams  106   a  and  106   b , and the other side of the individual cantilever beams  106   a  and  106   b  not connecting with the proof mass  104  is respectively connected with one of the anchors  108   a  and  108   b  formed in the support frame  102 . Moreover, the piezoresistive type Z-axis accelerometer in this embodiment comprises two piezoresistive material layers  110   a  and  110   b  (illustrated with dotted line here) to function as two piezoresistors, and two piezoresistive material layers  110   a  and  110   b  are respectively embedded in one of the cantilever beams  106   a  and  106   b . As shown in  FIG. 11 , the piezoresistive material layers  110   a  and  110   b  of the piezoresistive type Z-axis accelerometer can be connected in series to form a sensing resistor in a wheatstone bridge (not shown). In this embodiment, configurations of the anchors  108   a  and  108   b , the cantilever beams  106   a  and  106   b , and the piezoresistive material layers  110   a  and  110   b  are similar with the configurations of the anchor  108 , the cantilever beam  106  and the piezoresistive layer  110  shown in  FIGS. 1-4  and are not described and illustrated in detail here. 
     In  FIG. 12 , a schematic perspective diagram taken along a line  12 - 12  in  FIG. 11  is illustrated. For the purpose of simplicity, only components such as the passivation layer  114 , the cantilever beams  106   a  and  106   b , the anchors  108   a  and  108   b , the proof mass  104  and the substrate  100  are illustrated. The proof mass  104  is formed by stacking and interleaving one or a plurality of conductive layers  122  and the dielectric layers  124  together, and a region covered by the passivation layer  114  is substantially where the support frame  102  is. Herein, the proof mass  104  is under a static status not sensing exterior stresses, such that the proof mass  104 , the cantilever beams  106   a  and  106   b , and the piezoresistive material layers  110   a  and  110   b  are substantially parallel with the X-Y plane of the substrate  100 . A schematic perspective view of the piezoresistive type Z-axis accelerometer shown in  FIGS. 11-12  during sensing exterior accelerations and operations thereof is similar with that illustrated in  FIG. 7  and is not described and illustrated in detail here. 
     In  FIG. 13 , a schematic top view of yet another exemplary piezoresistive type Z-axis accelerometer is illustrated. As shown in  FIG. 13 , the exemplary piezoresistive type Z-axis accelerometer is similar with that illustrated in  FIG. 8 , and a difference therebetween is that three adjacent sides of the proof mass  104  in this embodiment are respectively connected with a side of three individual cantilever beams  106   a ,  106   b  and  106   c , and the other side of the individual cantilever beams  106   a ,  106   b  and  106   b  not connecting with the proof mass  104  is respectively connected with one of the anchors  108   a ,  108   b  and  108   c  formed in the support frame  102 . Moreover, the piezoresistive type Z-axis accelerometer in this embodiment comprises three piezoresistive material layers  110   a ,  110   b  and  110   c  (illustrated with dotted line here) to function as three piezoresistors, and the three piezoresistive material layers  110   a ,  110   b  and  110   c  are respectively embedded in one of the cantilever beams  106   a ,  106   b  and  106   c . As shown in  FIG. 13 , the piezoresistive material layers  110   a ,  110   b  and  110   c  of the piezoresistive type Z-axis accelerometer can be connected in series to form a sensing resistor in a wheatstone bridge (not shown). In this embodiment, configurations of the anchors  108   a ,  108   b  and  108   c , the cantilever beams  106   a ,  106   b  and  106   c , and the piezoresistive material layers  110   a ,  110   b  and  110   c  are similar with the configurations of the anchor  108 , the cantilever beam  106  and the piezoresistive layer  110  shown in  FIGS. 1-4  and are not described and illustrated in detail here. 
     In  FIG. 14 , a schematic perspective diagram taken along a line  14 - 14  in  FIG. 13  is illustrated. For the purpose of simplicity, only components such as the passivation layer  114 , the cantilever beams  106   a ,  106   b  and  106   c , the anchors  108   a ,  108   b , and  108   c , the proof mass  104  and the substrate  100  are illustrated. The proof mass  104  is formed by stacking and interleaving one or a plurality of conductive layers  122  and the dielectric layers  124  together and a region covered by the passivation layer  114  is substantially where the support frame  102  is. Herein, the proof mass  104  is under a static status not sensing exterior stresses, such that the proof mass  104 , the cantilever beams  106   a ,  106   b  and  106   c , and the piezoresistive material layers  110   a ,  110   b  and  110   c  are substantially parallel with the X-Y plane of the substrate  100 . A schematic perspective view of the piezoresistive type Z-axis accelerometer shown in  FIGS. 13-14  when sensing exterior accelerations and operations thereof is similar with that illustrated in  FIG. 10  and is not described and illustrated in detail here. 
     While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.