Patent Document

RELATED APPLICATION 
       [0001]    None 
       TECHNICAL FIELD 
       [0002]    The present invention relates generally to microelectromechanical systems (MEMS) device and more particularly, to one or more threshold sensors to sense external influence imparted to a MEMS device. 
       DESCRIPTION OF RELATED ART 
       [0003]    MEMS devices are formed using various semiconductor manufacturing processes. MEMS devices may have fixed and movable portions. MEMS devices may include one or more MEMS sensors. MEMS sensors may sometimes be subjected to unwanted external influence. Sometimes, unwanted external influence may void the warranty, weaken the device, degrade the lifetime, damage the device or break the device. When diagnosing the MEMS device it is beneficial to know if the MEMS device was subjected to unwanted external influence. 
         [0004]    With these needs in mind, the current disclosure arises. This brief summary has been provided so that the nature of the disclosure may be understood quickly. A more complete understanding of the disclosure can be obtained by reference to the following detailed description of the various embodiments thereof in connection with the attached drawings. 
       SUMMARY OF THE INVENTION 
       [0005]    In one embodiment a device with a first MEMS device and a second MEMS device is disclosed. The first MEMS device is configured to sense at least one external influence. The second MEMS device is responsive to the at least one external influence. The first MEMS device is configured to change a state when the at least one external influence exceeds a threshold value. The first MEMS device is configured to retain the state below the threshold value. The change in state of the first MEMS device is done passively and the change in state of the first MEMS device is indicative of a status of the second MEMS device. 
         [0006]    In another embodiment, a device with a first MEMS device and an object is disclosed. The first MEMS device is configured to sense at least one external influence. The object is responsive to the at least one external influence. The first MEMS device is configured to change a state when the at least one external influence exceeds a threshold value. The first MEMS device is configured to retain the state below the threshold value. The change in state of the first MEMS device is done passively and the change in state of the first MEMS device is indicative of a status of the object. 
         [0007]    This brief summary is provided so that the nature of the disclosure may be understood quickly. A more complete understanding of the disclosure can be obtained by reference to the following detailed description of the preferred embodiments thereof in connection with the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The foregoing and other features of several embodiments are described with reference to the drawings. In the drawings, the same components have the same reference numerals. The illustrated embodiments are intended to illustrate but not limit the invention. The drawings include the following Figures: 
           [0009]      FIG. 1  shows a device with a first MEMS device and a second MEMS device, according to one aspect of the present disclosure; 
           [0010]      FIG. 2  shows an example first MEMS device, according another aspect of the present disclosure; 
           [0011]      FIG. 3  shows another example first MEMS device, according to yet another aspect of the present disclosure; 
           [0012]      FIG. 4  shows yet another example first MEMS device, according to an aspect of the present disclosure; 
           [0013]      FIG. 5  shows yet another example first MEMS device, according to another aspect of the present disclosure; 
           [0014]      FIGS. 6A-6D  show an example friction spring implementation of contacts for the first MEMS device, according to an aspect of the present disclosure; 
           [0015]      FIGS. 7A-7D  show another example friction spring implementation of contacts for the first MEMS device, according to an aspect of the present disclosure; 
           [0016]      FIGS. 8A and 8B  show an example strain gauge implementation of contacts for the first MEMS device, according to an aspect of the present disclosure; 
           [0017]      FIG. 9  shows an example second MEMS device, according to an aspect of the present disclosure; and 
           [0018]      FIG. 10  shows an example first MEMS device configured as an event counter, according to one aspect of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    To facilitate an understanding of the adaptive aspects of the present disclosure, exemplary apparatus and method for sensing external influence upon a device is described. The specific construction and operation of the adaptive aspects of the apparatus and method for sensing external influence upon the device of the present disclosure are described with reference to an exemplary device with a first MEMS device and a second MEMS device. 
         [0020]      FIG. 1  shows a device  100 , with a first MEMS device  102  and a second MEMS device  104 . In one example, the first MEMS device  102  may be configured to change state of a state indicator  115  when the external influence exceeds one or more threshold limits. Various adaptive aspects of the first MEMS device  102  will be later described in detail. The Second MEMS device  104  may be configured to have one or more sensor  106 . The sensor  106  may be configured as a gyroscope, accelerometer, magnetometer, barometer, microphone and the likes. The first MEMS device  102  is configured to selectively measure any external influence the sensor  106  of the second MEMS device  104  may be subjected to. In some examples, the external influence may be imparted during the life cycle of the device. In some examples, the external influence may be imparted during an assembly process of the device  100 . In yet other examples, the external influence may be imparted during the transportation or storage of the device  100 . In yet another example, the external influence may be imparted during the operation of the device  100 , for example, in an appliance into which the device  100  is incorporated into. In some examples, the external influence may be a shock. In some examples, the external influence may be a strain. In some examples, the external influence may be a temperature. 
         [0021]    The first MEMS device  102 , is further configured to be a passive device where only the energy from the external influence is used to change and store a state in a state indicator  115  of the First MEMS device  102 . The passive device requires no external power supply like a battery or the likes. The state of the first MEMS device may be determined by visually looking at the device through a microscope like Infra-red, optical or other. The first MEMS device could also be coupled to a signal processor  117 . The signal processor  117  may be configured to read the state indicator  115  of the first MEMS device  102  and output the status  119  that indicates the reliability of the second MEMS device  104 . In another embodiment the first MEMS device  102 , second MEMS device  104  and signal processor  117  may be anchored to a common surface or substrate  121 . 
         [0022]    Now, referring to  FIG. 2 , an example first MEMS device  102  is described. The first MEMS device  102  includes a handle layer  108 , a device layer  110  and a IC substrate  112 . One or more threshold sensors are formed on the device layer  110 . A fusion bond layer  114  bonds the handle layer  108  to device layer  110 , to form an upper cavity  116 , defined by the lower side  118  of the handle layer  108  and upper side  120  of the device layer  110 . 
         [0023]      FIG. 2  also shows trench pattern  122 - 1 , a mass  124 . The mass  124  is movable and is attached to a spring  126 . The spring  126  is created by forming a plurality of trench patterns (not shown) on the device layer  110 , for example, using a DRIE process. The mass  124  is configured to substantially move along a first direction. The mass  124  includes a plunger  128 . In some examples, the plunger  128  may extend beyond the lower side  130  of the device layer  110 . 
         [0024]    The device layer  110  includes a standoff  132 . The standoff  132  surrounds one or more threshold sensors formed on the device layer  110 . A seal ring  134  is disposed between the standoff  132  and a top surface  136  of the IC substrate  112  so as to seal the threshold sensor of the first MEMS device  102 . 
         [0025]    The IC substrate  112  in some examples may be a CMOS substrate. The IC substrate  112  includes a substrate cavity  138 . A first conductor  140  is disposed over the substrate cavity  138 . The first conductor  140  is disposed relative to the plunger  128  such that upon sensing an external influence at or above a threshold value, for example, a force along the first direction at or above a threshold value, the plunger  128  will impact the first conductor  140  and break the first conductor  140 . The first conductor  140  includes a first end  142  and a second end  144 . The first end  142  is coupled to a first terminal  146  and the second end  144  is coupled to a second terminal  148 . The MEMS device  102  described in  FIG. 2  is an example of a normally closed switch. 
         [0026]    A low resistance between the first terminal  146  and the second terminal  148  is indicative that the first conductor  140  is not broken. In other words, the device  100  has not experienced an external influence, in this example, a force substantially along the first direction above a threshold value. In some examples, this may be indicative of a first status of the second MEMS device  104 . A high resistance between the first terminal  146  and the second terminal  148  is indicative that the first conductor  140  is broken. In other words, it is indicative that the device  100  has experienced an external influence, in this example, a force substantially along the first direction above a threshold value. In some examples, this may be indicative of a second status of the second MEMS device  104 . In some examples, the second status may indicate that the second MEMS device  104  may have suffered damage which may render the second MEMS device  104  to not perform at its optimum performance level. In yet other examples, the second status may indicate that the second MEMS device  104  is inoperative due to the external influence above the threshold value. 
         [0027]    One or more electronic circuits (not shown) may be disposed over the IC substrate  112  and the first terminal  146  and the second terminal  148  may be configured to electrically couple to the electronic circuit. In some examples, the resistance of the first conductor  140  is selectively measured on demand so that minimal energy (or power) is expended to measure the status of the first conductor  140  as to whether the first conductor  140  is broken or not. In other words, no energy (or power) is expended to operate the first MEMS device  102  and minimal energy (or power) is selectively expended to measure the status of the first conductor  140 . 
         [0028]    In the above example as described with reference to  FIG. 2 , the mass  124  and the plunger  128  is configured to move normal to the device layer  110  and the first conductor  140  is formed on the substrate  112 . In some examples, the mass  124  and the plunger  128  may be configured move in-plane relative to the device layer  110  and the first conductor  140  may be formed on the device layer  110 , instead on the substrate  112 . In such an example, the plunger  128  is configured to move due to an excitation in a direction that is in-plane with the device layer. The first conductor  140  is disposed relative to the plunger  128  such that upon sensing an external influence at or above a threshold value, for example, a force along a direction in-plane relative to the device layer  110 , at or above a threshold value, the plunger  128  will impact the first conductor  140  and break the first conductor  140 . A pair of conductors may be disposed on the device layer coupled to a distal end of the first conductor  140  to permit measurement of a resistance of the first conductor  140 . As previously discussed, a change in a resistance of the first conductor  140  may indicate a change in a status of the second MEMS device  104 . 
         [0029]    Now referring to  FIG. 3 , another example first MEMS device  102 - 1  is described. In this example, the first MEMS device  102 - 1  is similar to the first MEMS device  102  in that the IC substrate  112  includes a substrate cavity  138  and the first conductor. However, in this example, a second conductor  150  is disposed in the substrate cavity  138 . The second conductor  150  is disposed relative to the first conductor  140  so as to define a gap G. The plunger  128 , the first conductor  140  and the second conductor  150  are disposed relative to each other such that upon sensing an external influence, for example, a force along the first direction, the gap G reduces. And, at or above a threshold value, the plunger impacts the first conductor  140  and the first conductor  140  couples to the second conductor  150 . In one example, a third terminal  152  is coupled to the first conductor  140  and a fourth terminal  154  is coupled to the second conductor  150 . The MEMS device  102 - 1  describe in  FIG. 3  is an example of a normally open switch. 
         [0030]    In one example, the first conductor  140  and the second conductor  150  form electrodes of a capacitor and a change in the gap G changes a capacitance value of the capacitor so formed. As the gap G reduces, the capacitance value of the capacitor reduces. This change in capacitance due to change in the gap G, in one example, may indicate a corresponding value of the external influence imparted to the first conductor  140 . At or above a threshold value, the first conductor  140  couples to the second conductor  150 , thereby reducing the gap G to zero, which will indicate a substantially zero capacitance value. 
         [0031]    In another example, a high resistance between the third terminal  152  and the fourth terminal  154  is indicative that the first conductor  140  has not been moved by the plunger  128  to couple to the second conductor  150 . In other words, the device  100  has not experienced an external influence, in this example, a force substantially along the first direction above a threshold value. In some examples, this may be indicative of a first status of the second MEMS device  104 . A low resistance between the third terminal  152  and the fourth terminal  154  is indicative that the first conductor  140  has been moved by the plunger  128  to couple to the second conductor  150 . In other words, it is indicative that the device  100  has experienced an external influence, in this example, a force substantially along the first direction above a threshold value. In some examples, this may be indicative of a second status of the second MEMS device  104 . In some examples, the second status may indicate that the second MEMS device  104  may have suffered damage which may render the second MEMS device  104  to not perform at its optimum performance level. In yet other examples, the second status may indicate that the second MEMS device  104  is inoperative due to the external influence above the threshold value. 
         [0032]    One or more electronic circuits (not shown) may be disposed over the IC substrate  112  and the third terminal  152  and the fourth terminal  154  may be configured to electrically couple to the electronic circuit. In some examples, the resistance between the third terminal  152  and the fourth terminal  154  is selectively measured on demand so that minimal energy (or power) is expended to measure the status of the first conductor  140  as to whether it has moved sufficiently to couple to the second conductor  150 . In other words, no energy (or power) is expended to operate the first MEMS device  102  and minimal energy (or power) is selectively expended to measure the status of the first conductor  140 . 
         [0033]    In the above example as described with reference to  FIG. 3 , the mass  124  and the plunger  128  is configured to move normal to the device layer  110  and the first conductor  140  and second conductor  150  are formed on the substrate  112 . In some examples, the mass  124  and the plunger  128  may be configured move in-plane relative to the device layer  110  and the first conductor  140  and second conductor  150  may be formed on the device layer  110 , instead on the substrate  112 . In such an example, the plunger  128  is configured to move due to an excitation in a direction that is in-plane with the device layer  110 . The first conductor  140  is disposed relative to the plunger  128  such that upon sensing an external influence at or above a threshold value, for example, a force along a direction in-plane relative to the device layer  110 , at or above a threshold value, the plunger  128  will impact the first conductor  140  and move the first conductor  140 . A pair of conductors may be disposed on the device layer coupled to a distal end of the first conductor  140  and second conductor  150  so as to measure status of the second MEMS device  104 , as previously described with reference to  FIG. 3 . 
         [0034]    Now, referring to  FIG. 4 , yet another example first MEMS device  102 - 2  is shown. In this example, a first mass  402  is movably coupled to a first anchor  404  and a second anchor  406 . A first spring  408  couples the first mass  402  to the first anchor  404 . A second spring  410  couples the first mass  402  to the second anchor  406 . A first contact  412  is coupled to the first mass  402  and disposed about a first end  414  of the first mass  402 . A second contact  416  is coupled to the first mass  402  and disposed about a second end  418  of the first mass  402 . The first mass  402  is configured to move along a first direction and a second direction. A third contact  420  is disposed on a third anchor  422 . For example, the third contact  420  may be disposed on a first arm  424  coupled to and extending from the third anchor  422 . The third contact  420  is disposed relative to the first contact  412  such that when the first mass  402  moves sufficiently along the first direction, the first contact  412  slides over a first surface  426  of the third contact  420 , slips over the third contact  420  and rests on a second surface  428  of the third contact  420 . For example, the first contact  412  may be configured to slip over the third contact  420 , when an external influence along the first direction is at or above a first threshold value. In some examples, the third contact  420  acts as a latch and holds the first contact  412  in place. In other words, the third contact  420  prevents the mass  402  from returning to its previous position once the external influence has exceeds a first threshold value. 
         [0035]    A fourth contact  430  is disposed on a fourth anchor  432 . For example, the fourth contact  430  may be disposed on a second arm  434  coupled to and extending from the fourth anchor  432 . The fourth contact  430  is disposed relative to the second contact  416  such that when the first mass  402  moves sufficiently along the second direction, the second contact  416  slides over a third surface  436  of the fourth contact  430 , slips over the fourth contact  430  and rests on a fourth surface  438  of the fourth contact  430 . For example, the second contact  416  may be configured to slip over the fourth contact  430 , when an external influence along the second direction is at or above a second threshold value. In some examples, the fourth contact  430  acts as a latch and holds the second contact  416  in place. In other words, the fourth contact  430  prevents the mass  402  from returning to its previous position once the external influence has exceeds a second threshold value. After the second contact has slipped over the fourth contact  430 , fifth contact  440  comes into play. 
         [0036]    The fifth contact  440  is disposed on a fifth anchor  442 . For example, the fifth contact  440  may be disposed on a third arm  444  coupled to and extending from the fifth anchor  442 . The fifth contact  440  is disposed relative to the second contact  416  such that after the second contact has slid over the fourth contact  430 , an external influence at or above the third threshold value will cause the first mass  402  to move along the second direction. The movement of the first mass  402  causes the second contact  416  to slide over the fifth surface  446  of the fifth contact  440  and slides over the fifth contact  440  and rests on the sixth surface  448  of the fifth contact  440 . For example, the second contact  416  may be configured to slip over the fifth contact  440 , when an external influence along the second direction is at or above a third threshold value. In some examples, the fifth contact  440  acts as a latch and holds the second contact  416  in place. In other words, the fifth contact  440  prevents the mass  402  from returning to its previous position once the external influence has exceeds a third threshold value. 
         [0037]    As one skilled in the art appreciates, the first MEMS device  102 - 2  in this example is configured to sense one threshold value, for example, first threshold value in the first direction and two threshold values, for example, second threshold value and third threshold value in the first directions. As one skilled in the art appreciates, the first MEMS device  102 - 2  may be configured to measure a plurality of threshold values in each direction, by appropriately configuring and positioning additional contacts that operatively work with the first contact and the second contact at different threshold values of the external influence. 
         [0038]    In some examples, one or more terminals may be coupled to the first contact, second contact, third contact, fourth contact and the fifth contact to measure a resistance between the first contact and the third contact, second contact and the fourth contact and the second contact and the fifth contact. As an example, if the resistance between the first contact and the third contact is low, it indicates that the first MEMS device was subjected to an external influence at or above a first threshold value in the first direction. Similarly, if the resistance between the second contact and the fourth contact is low, it indicates that the first MEMS device was subjected to an external influence at or above a second threshold value in the second direction. Similarly, if the resistance between the second contact and the fifth contact is low, it indicates that the first MEMS device was subjected to an external influence at or above a third threshold value in the second direction. 
         [0039]    As one skilled in the art appreciates, the first mass  402  may be appropriately doped to be conductive and may form a conductive path to measure the resistance between contacts discussed above. Similarly, first anchor  404 , second anchor  406 , third anchor  422 , fourth anchor  432  and fifth anchor  442  may be appropriately doped to be conductive and may form a conductive path to measure the resistance between contacts discussed above. 
         [0040]    Now, referring to  FIG. 5 , yet another example first MEMS device  102 - 3  is shown. The first MEMS device  102 - 3  of  FIG. 5  is similar to the first MEMS device  102 - 2  of  FIG. 4 , except that a first thermal actuator  502  couples the first mass  402  to the first anchor  404 . In some examples, the first thermal actuator  502  is a passive bimorph thermal actuator. And, a second thermal actuator  504  couples the first mass  402  to the second anchor  406 . In some examples, the second thermal actuator  504  is a passive bimorph thermal actuator. The first thermal actuator  502  and the second thermal actuator  504  are configured such that when the first MEMS device  102 - 3  is subjected to a temperature lower than an ambient temperature, the first mass  402  moves in a direction substantially along the first direction. Further, the first thermal actuator  502  and the second thermal actuator  504  are configured such that when the first MEMS device  102 - 3  is subjected to a temperature higher than an ambient temperature, the first mass  402  moves in a direction substantially along the second direction. The first MEMS device is configured such that the first contact  412  slides over the third contact  420 , when a temperature the first MEMS device is subjected to is above a first threshold value, in other words, when the temperature is at or below a certain value. Similarly, first MEMS device is configured such that the second contact  416  slides over the fourth contact  430 , when a temperature the first MEMS device is subjected to is above a second threshold value. Further, the first MEMS device is configured such that the second contact  416  slides over the fifth contact  440 , when a temperature the first MEMS device is subjected to is above a third threshold value. 
         [0041]    As previously described with reference to  FIG. 4 , in some examples, the third contact  420  acts as a latch and holds the first contact  412  in place. In other words, the third contact  420  prevents the mass  402  from returning to its previous position, once the external influence has exceeded a preset threshold value. Similarly, fourth contact  430  and fifth contact  440  may act as a latch and hold the second contact  416  in place. In other words, the fourth contact  430  and fifth contact  440  prevent the mass  402  from returning to its previous position once the external influence has exceeded a preset threshold value. 
         [0042]    Now, referring to  FIGS. 6A-6D , an example friction spring configuration implementation for the contacts is described. The friction spring configuration for the contacts may be used in one or more example first MEMS device  102  previously described. Now, referring to  FIG. 6A , the second mass  602  is movably coupled to a sixth anchor  604  by a third spring  606 . The second mass  602  is configured to move along a third direction. The sixth contact  608  is movably coupled to the second mass  602  by a fourth spring  610 . A seventh contact  612  is coupled to a seventh anchor  614 . The sixth surface  616  of the sixth contact  608  is configured to touch and slide over a seventh surface  618  of the seventh contact  612 , when the second mass  602  moves in the third direction. 
         [0043]    Now, referring to  FIG. 6B , when an external influence, for example, a force is applied in the third direction, the third spring  606  expands and the second mass  602  moves in the direction of the third direction. As the second mass  602  continues to move due to the external influence, the sixth surface  616  of the sixth contact  608  comes in contact with the seventh surface  618  of the seventh contact  612 . 
         [0044]    Now, referring to  FIG. 6C , based on the extent of the external force, as the second mass  602  continues to move in the third direction, the sixth contact  608  continues to slide over the seventh contact  612  and the fourth spring  610  continues to contract. As sixth surface  616  slides over seventh surface  618  a friction force from the compression of spring  610  and the coefficient of friction of sixth surface  616  and seventh surface  618  opposes the motion. Now, referring to  FIG. 6D , at a threshold value of the external influence, for example, a fourth threshold value, the sixth contact  608  completely slides over the seventh surface  618  of the seventh contact  612  and rests on the first side  620  of the seventh contact  612 . The fourth spring  610  expands from its contracted position and holds the sixth contact  608  on the first side  620  of the seventh contact  612 . A low resistance between the sixth contact  608  and the seventh contact  612  indicates that an external influence at or above the fourth threshold value was experienced. A high resistance between the sixth contact  608  and the seventh contact  612  indicates that an external influence at or above the fourth threshold value was not experienced. The strength of the spring  610 , the geometry of sixth surface  616  and seventh surface  618  and the coefficient of friction of the sixth surface  616  and seventh surface  618  set the threshold limit of the switch. Once the device has reached position as shown in  FIG. 6D  a certain amount of work energy is required to reach this state. It is this work energy that sets the threshold limit. For example, a stiffness, shape and size of the friction surface and the spring determine a threshold value. 
         [0045]    Now, referring to  FIGS. 7A-7D  another example friction spring configuration implementation describing the threshold contact operation is shown. The friction spring configuration for the contact may be used in one or more example first MEMS device  102  previously described. Now, referring to  FIG. 7A , the third mass  702  is movably coupled to an eighth anchor  704  by a fifth spring  706 . The third mass  702  is configured to move along a fourth direction. The eighth contact  708  is coupled to the third mass  702 . In this example, the eighth contact  708  is configured to be compliant, for example, like a leaf spring. A ninth contact  712  is coupled to a ninth anchor  714 . In this example, the ninth contact  712  is configured to be compliant, for example, like a leaf spring. The eighth surface  716  of the eighth contact  708  is configured to touch and slide over a ninth surface  718  of the ninth contact  712 , when the third mass  702  moves in the fourth direction. 
         [0046]    Now, referring to  FIG. 7B , when an external influence, for example, a force is applied in the fourth direction, the fifth spring  706  expands and the third mass  702  moves in the direction of the fourth direction. As the third mass  702  continues to move due to the external influence, the eighth surface  716  of the eighth contact  708  comes in contact with the ninth surface  718  of the ninth contact  712 . 
         [0047]    Now, referring to  FIG. 7C , based on the extent of the external force, as the third mass  702  continues to move in the fourth direction, the eighth contact  708  continues to slide over the ninth contact  712 , as both eighth contact  708  and the ninth contact  712  comply and bend to slide over each other. Now, referring to  FIG. 7D , at a threshold value of the external influence, for example, a fifth threshold value, the eighth contact  708  completely slides over the ninth surface  718  of the ninth contact  712 , as shown and rests on the first side  720  of the ninth contact  712 . At this point, both the eighth contact  708  and ninth contact  712  have returned back to their original shape. The eighth contact  708  continued to rest on the first side  720  of the ninth contact  712 . A low resistance between the eighth contact  708  and the ninth contact  712  indicates that an external influence at or above the fifth threshold value was experienced. A high resistance between the eighth contact  708  and the ninth contact  712  indicates that an external influence at or above the fifth threshold value was not experienced. The strength of the spring formed by the eighth contact  708  and ninth contact  712  and the geometry of the eighth surface  716  and ninth surface  718  set the threshold limit of the switch. Once the device has reached position as shown in  FIG. 7D  a certain amount of Work energy is required to reach this state. It is the Work energy that sets the threshold limit. 
         [0048]    Now, referring to  FIGS. 8A and 8B , an example strain gauge configuration implementation for the contacts is described. The strain gauge configuration for the contacts may be used in one or more example first MEMS device  102  previously described. Now, referring to  FIG. 8A , a tenth anchor  802  and an eleventh anchor  804  is provided. A first connector  806  couples the tenth anchor  802  to an arm  808  at a first location  810 . A second connector  812  couples the eleventh anchor  804  to the arm  808  at a second location  814 . A tenth contact  816  is disposed at a distal end  818  of the arm  808 , away from the first location  810 . An eleventh contact  820  is disposed in an operative relationship to the tenth contact  816  and coupled to a twelfth anchor  822 . 
         [0049]    The second location  814  is separated from the first location  810  by a distance so that when an external influence, for example, a strain is applied in the fifth direction, the tenth anchor  802  moves in the direction of the fifth direction and the eleventh anchor  804  moves (or pushed) in a direction opposite to the fifth direction, thereby rotating the arm  808  in a direction shown by the arrow  824 . Now, referring to  FIG. 8B , when an external influence greater than fifth threshold value is applied in the fifth direction, the arm  808  is sufficiently rotated along the direction shown by the arrow  824 , wherein the tenth contact  816  goes past the eleventh contact  820  and rests on the upper side  826  of the eleventh contact  820 . As one skilled in the art appreciates, the tenth contact  816  may be constructed such that the tenth contact  816  continues to rest on the upper side  826  of the eleventh contact  820  even when the external influence in the fifth direction is no longer present. A low resistance between the tenth contact  816  and the eleventh contact  820  indicates that an external influence at or above the fifth threshold value was experienced. A high resistance between the tenth contact  816  and the eleventh contact  820  indicates that an external influence at or above the fifth threshold value was not experienced. 
         [0050]    Now, referring to  FIG. 9  an exemplary second MEMS device  104  is described. Second MEMS device  104  includes a MEMS substrate  901  and integrated circuit substrate  926 . MEMS substrate  901  includes a handle layer  902  and a device layer  904 . A fusion bond layer  906  bonds the handle layer  902  to device layer  904 , to form an upper cavity  908 , defined by the lower side  910  of the handle layer  902  and upper side  912  of the device layer  904 . 
         [0051]    Now referring to device layer  904 , a plurality of standoff  914  structures are formed on the device layer  904 , for example, by deep reactive ion etching (DRIE) process.  FIG. 9  further shows trench patterns  920 - 1  and  920 - 2 , an actuator  922 , device pads  924 , integrated circuit substrate  926 , IC pads  928  and seal ring  930 . Seal ring  930  in some examples may be a conductive metal seal. A movable actuator  922  is created by forming a plurality of trench patterns  920 - 1  and  920 - 2  on the device layer  904 , for example, using a DRIE process. Actuator  922  may be configured as a sensor, for example, to measure acceleration, angular rotation and the likes. Next, device pads  924 , for example, made of germanium alloys are deposited and patterned on the device layer  904 . 
         [0052]    Integrated circuit substrate  926  includes one or more electronic circuits that communicate with various sensors formed on the device layer  904 . IC pads  928 , for example, made of aluminum alloys are deposited and patterned on the integrated circuit substrate  926 . IC pads  928  are coupled to device pads  924  to provide a communication path to various sensors formed on the device layer  904 . For example, device pads  924  may be conductively bonded with IC pads  928 . 
         [0053]    Standoff  914 - 1  surrounds various devices formed on the device layer  904 . A seal ring  930  is formed on the standoff  914 - 1  to bond the device layer  904  with integrated circuit substrate  926 , for example, to hermitically seal various devices formed on the device layer  904 . Height of the standoff  914 - 1 , along with seal ring  930  define height of the lower cavity  932 . 
         [0054]    As one skilled in the art appreciates, first MEMS device  102  may also be constructed as part of the second MEMS device  104 . In one examples, a common handle layer may be used for first MEMS device  102  and second MEMS device  104 . In some examples, elements of both first MEMS device  102  and second MEMS device  104  may be constructed on a common device layer. In yet other examples, the first MEMS device  102  and second MEMS device  104  may be constructed separately but packaged together in a device, for example, device  100 . 
         [0055]      FIG. 10  shows another example first MEMS device  102 - 4 . The first MEMS device  102 - 4  may be substantially similar to the first MEMS device  102 - 2 , but reconfigured to be an event counter. MEMS device  102 - 4  has a movable mass  1002  connected to an anchor  1004  through a spring  1006 . The movable mass  1002  further includes a contact  1008 . A plurality of flexible latches  1010 - 1  to  1010 - 4  are disposed at substantially equal distance from the moveable mass  1002 . Under an external excitation the contact  1008  of the moveable mass  1002  contacts the flexible latch and if the external influence exceeds a threshold the moveable mass moves past the flexible latch and the moveable mass  1002  is prevented from moving backwards. In this embodiment the stiffness of the flexible latch  1010 - 1  to  1010 - 4  is much greater than the stiffness of spring  1006  and therefore although the plurality of flexible latches  1001 - 1  to  1010 - 4  are disposed at different locations the threshold value is substantially the same. In this configuration the state of MEMS devices  102 - 4  represents the number of times the MEMS device  102 - 4  exceeds a single threshold value. 
         [0056]    As one skilled in the art appreciates, although first MEMS device  102 - 4  has a pair of contacts  1008  and corresponding pairs of flexible latches  1010 - 1  to  1010 - 4 , first MEMS device  102 - 4  may be modified to have a single contact and a plurality of single flexible latches. 
         [0000]    As one skilled in the art appreciates, various examples of the first MEMS device described in this disclosure may be implemented in a single device that may be configured to measure threshold of different external influences. Further, various examples of the first MEMS device described in this disclosure may be implemented in a single device to measure different thresholds of the same external influence. Additionally, various examples of the first MEMS device described in this disclosure may be implemented in a single device to measure different thresholds of the same external influence in different directions. 
         [0057]    While embodiments of the present invention are described above with respect to what is currently considered its preferred embodiments, it is to be understood that the invention is not limited to that described above. To the contrary, the invention is intended to cover various modifications and equivalent arrangements within the spirit and scope of the appended claims.

Technology Category: h