Abstract:
An improved microsystems testing and characterization system which allows the system user to identify specific structures, and thereby to initiate an automated testing sequence to be applied to that structure or a series of structures. The integrated control system that governs the present invention automates the power supply to the device under test, the precision motion control of all components, the sensor operation, data processing and data presentation. Therefore operation is autonomous once the microstructure is in place and the testing sequence is specified. The integrated testing system can be used to perform tests on an entire wafer or on a single die.

Description:
FIELD OF THE INVENTION 
     This invention relates to the field of microsystems characterization systems, and particularly to microelectromechanical microsystems characterization systems. 
     BACKGROUND OF THE INVENTION 
     The present invention comprises a testing and characterization system to provide automated multi-domain measurements of a wide range of microsystem devices in either single chip or wafer format. Unlike electronic devices and integrated circuits in which only lumped electrical parameters are needed for device level modeling, microsystem devices require the precise and simultaneous measurement of multi-domain parameters, often widely dissimilar. In the microelectrical domain, probe stations, waveform generators and current-voltage measurement equipment are all instruments used for modeling and or testing based on lumped electrical circuits. However, they are not capable of providing characterization of the mechanical or fluidic properties common in microsystem devices. 
     Typical microsystem devices that would benefit from the testing and characterization capabilities of the present invention include present and future devices with vibratory or bistable motion in either the horizontal or vertical direction, fluidic properties, or optical properties. Such devices include but are not limited to accelerometers, diffraction gratings, pumps, gyroscopes, micromirrors, micromicrophones, drive motors. actuators and diaphragms. 
     Current technology and prior art carried over from electronic device testing tend to provide means for testing a few characteristics of the micros,stem devices, primarily electrical. However, these technologies often lack the ability to characterize the results of the electrical stimulus, i.e. mechanical motion. Similarly, prior art exists that is capable of non-contact examination of the topology of wafers or devices in search of structural defects, but these systems too are incapable of characterizing the mechanical motion or fluidic operation of these wafers or devices. Overall, they lack an overall multi-domain characterization ability that is needed to establish the microsystem devices as viable components suitable for full scale manufacturing. 
     For example, U.S. Pat. No. 5,773,951 by Markowski and Cosby provides a means of wafer only level electrical probing. As discussed above, this technology is capable of testing and verifying the electrical contacts of the microsystems device, but is unable to characterize the operation resulting from the electrical stimulus. 
     Similarly, several U.S. patents appear to disclose non-contact surface profiling in the determination of structural defects. These include U.S. Pat. No. 5,127,726 by Moran which provides a high resolution surface inspection system: U.S. Pat. No. 5,105,147 by Karasikov and Ilssar which provides a optical inspection system for wafers; U.S. Pat. No. 4,607,525 by Turner and Roch which provides an air probe for wafer contouring. U.S. Pat. No. 5,526,116 and U.S. Pat. No. 5,671,050 by de Groot which provide an optical means of surface profiling for wafer inspection; and U.S. Pat. No. 5,479,252 by Worster .et al., which provides a confocal laser scanning system for defect detection in wafers. However, these systems often lack the ability to provide electrical stimulus to characterize the resultant surface structure or more importantly, to perform microsystem operation. 
     OBJECTS OF THE INVENTION 
     Therefore, it is the object of the invention disclosed herein to provide an integrated testing and characterization system for wafer level microsystem technologies. 
     It is also an object of the invention to provide an integrated testing and characterization system for die level microsystem technologies. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved microsystems testing system. By identifying specific structures, the user can initiate an automated testing sequence  106  to be implemented on that structure or a series of structures. The integrated control system that governs the present invention automates power supply to the device under test  101 , precision motion control of all components, sensor  134  operation, data processing and data presentation. Therefore operation is autonomous once the microstructure is in place and the testing sequence is specified. The integrated testing system can be used to perform tests on an entire wafer or on a single die. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the invention believed to be novel are set forth in the associated claims. The invention, however, together with further objects and advantages thereof may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a block diagram schematically illustrating the entire integrated system of a preferred embodiment of the invention. 
     FIG. 2 is a block diagram of the integrated control system architecture of the embodiment of FIG.  1 . 
     FIG. 3 is a flowchart of the operation of the integrated system of the embodiment of FIG.  1 . 
     FIG. 4 is a block diagram of an alternative embodiment of the invention in which a vacuum and vacuum control means are added to facilitate vacuum testing. 
    
    
     DETAILED DESCRIPTION 
     The present invention provides an improved testing system for microsystems technology. The overall goal of the system is to provide a basic means of performing automated tests designed to analyze the performance and characterize the operation of microsystems technology. The testing system can be implemented on wafer or die level microsystems, also know as microelectromechanical systems (MEMS). The testing system is predominantly automated, relying on the device design file  101  used to lay out and ultimately manufacture the wafer based structures to “navigate” the wafer or die. Although the primary application of the testing system is single wafer or die testing, for example in a research and development setting, this system could be incorporated into an assembly line for fully automated manufacturing testing within the scope of the invention and its associated claims. 
     A preferred embodiment of the invention can best be described with reference to FIG.  1 . Controller  100  receives device design file  101  along input train  104 . Device design file  101  comprises the layout file created to manufacture the wafer, and is used for navigation purposes by the testing system. 
     Controller  100  also receives testing locations input  102  along input train  104 . In embodiment of FIG. 1, testing locations input  102  comprises software level identification by the user of features and/or structures to be tested. The software level identification takes place in relation to device design file  101 , which as noted above, comprises the layout file/program used to create the structure or a file/program compatible thereto. The testing locations input  102  can be identified by the user, for example, through coordinate input or a cursor/cross-hair based point and click scheme, again, based on the information contained within device design file  101 . The location of the features and/or structures to be tested is stored by controller  100  for implementation in the testing sequence. 
     Testing parameters input  106  is also transferred to controller  100  along input path  104 . Testing parameters input  106  comprises information regarding the specifications of the testing sequence to be implemented. In the embodiment of FIG. 1, testing parameters input  106  comprises power supply parameters  108 , motion parameters  110 , and data acquisition parameters  112  to be applied to the device under test  114 . Power supply parameters  108  are applied to power supply module  116  of controller  100 . Motion parameters  110  are applied to motion module  118  of controller  100 . Data acquisition parameters  112  are applied to data acquisition module  120  of controller  100 . The testing sequence comprises a series of one or more testing steps to be performed, in series, and/or in parallel, as appropriate, at the one or more testing locations identified in testing locations input  102 . 
     Therefore, the input to controller  100  essentially comprises device design file  101 , testing locations input  102 , and testing parameters input  106 . As mentioned above, device design file  101  comprises the layout file used to manufacture the wafers. This design file  101  is used for navigation purposes by the controller  100 . It provides pre-test location information and serve as a basis for user identification of preferred testing locations  102 . With this feature, users can identify testing locations  102  in a familiar format, in any desired magnification level, without necessitating scanning and evaluation of the actual wafer/device. Testing parameters input  106  provides a means for the user to provide all necessary testing specification variables for the testing sequence. And again, testing locations input  102  and testing parameters input  106  are interrelated to one another insofar as various tests specified by, testing parameters input  106  will be performed at various locations specified by testing locations input  102 . 
     Controller  100  is the primary interface between the user and the rest of the system. As described above, input parameters ( 108 ,  110 ,  112 ) are supplied by the user to controller  100  in order to specify details of the testing sequence to be implemented. Controller  100  is comprised of several modules which govern the operation of particular components of the overall so stem. 
     Power supply module  116  of controller  100 , translates power supply parameters  108  supplied by the user into an applied voltage train  122  that is provided to probe assembly  124 . The applied voltage train  122  may comprise a voltage and corresponding time period over which it should be applied to a specific structure on the device under test  114 , or a series of voltages and corresponding time periods to be applied to a specific structure on the device under test  114  in a specific sequence. 
     Motion module  118  of controller  100  translates motion parameters  110  supplied by the user into motion control information that is used throughout the entire testing sequence by many components of the system. Motion module  118  provides a probe assembly motion control sequence  126  to probe assembly  124 . In the embodiment of FIG. 1, probe assembly  124  moves in the z-direction only. This motion allows probe assembly  124  to be moved into electrical contact with the device under test  114  in order to supply the desired voltages. Typically, probe assembly  124  is lowered from a set point above the device under test  114  to a point at which electrical contact is established between probe assembly  124  and device under test  114 . 
     Motion module  118  also provides a device motion control sequence  128  to device holder  130 . In the preferred embodiment, device holder  130  is capable of five axes of motion that include x, y, rotation ω, and two directions of tilt, θ and φ. More specifically, x-axis motion  146 , y-axis motion  148 , ω rotation  150 , θ tilt  152 , and φ tilt  154  of the device holder  130  is provided by device motion control sequence  128  from the motion module  118  of controller  100 . 
     Motion module  118  also provides sensor motion control sequence  132  to sensor  134 . In the embodiment of FIG. 1, sensor  134  is capable of motion along the x, y, and z axes, though this is not limiting and other motions obvious to someone of ordinary skill can be implemented in alternative embodiments. More specifically, x-axis motion  156 , y-axis motion  158 , and z-axis motion  160  for sensor  134  is provided by sensor motion control sequence  132  from motion module  118  of controller  100 . 
     Alternative embodiments the invention include alternative axial and rotational/tilt motion capabilities for probe assembly  124 , device holder  130  and sensor  134 . These alternative embodiments are described in more detail later. 
     Data acquisition module  120  of controller  100 , translates data acquisition parameters  112  supplied by the user to sensor  134  along data acquisition pathway  136 . Subsequently, the raw test data acquired by sensor  134  is fed along the same pathway from sensor  134  to data acquisition module  120  of controller  100 . From there, the acquired raw data is sent along the data pathway  138  to data processing module  140  of the controller  100 . The raw test data is then processed, and this processed test data is then sent along the output pathway  142  to be presented as output  144  to the user. 
     In the preferred embodiment, sensor  134  is a single point laser based reflectometer sensor capable of making surface profile measurements as well as single point measurements. Alternative embodiments of the present invention provide alternative sensing techniques/sensors  134  that provide operational information about the microsystem device under test  114  once power is applied. Such alternative sensing techniques/sensors  134  include but are not limited to thermal imaging, thermal microscopic imaging, interferometric sensing, profilometric sensing, triangulation sensing, and CCD imaging. These alternative sensing techniques would easily assimilate into and be encompassed by the overall structure of the present invention and operational details would be the same. Of course, the nature of sensor  134  is related to the nature of the data which data acquisition module  120  can direct sensor  134  to acquire. 
     The operation of the controller  100  can best be described with reference to the diagram in FIG. 2, which illustrates the input and output signals of controller  100 . Controller  100  receives input  246  which comprises device design file  101 , testing locations input  102  and testing parameters input  106  as described above. Controller  100  then provides input and receives feedback from its submodules, namely power supply module  116 , motion module  118 , and data acquisition module  120 . 
     More specifically as earlier described, power supply module  116  provides power input to probe assembly  124 . Motion control module  118  provides motion input to probe assembly  124  for motion in the z-direction ( 248 ). Motion control module  118  also provides input to device holder  130  for 5 axis motion specifically x, y, rotation and two directions of tilt θ and φ ( 250 ). Motion control module  118  also provides motion input to the sensor  134  for motion in the x, y, and z direction ( 252 ). Data acquisition module  120  provides input and receives feedback from sensor  134 . Processed test data output  144  from data processing module  140  of controller  100  is available to the user for storage and presentation  144 . 
     FIG. 3 is a flowchart depicting the operation of this embodiment of the invention. At input box  354  testing locations input  102  is introduced to controller  100 . As mentioned above, testing locations input  102  comprises location identification supplied by the user of structures or points to be tested in the testing sequence. The location identification takes place in a suitable representation of the device under test  114  in design layout software. That is to say, controller  100 , in the preferred embodiment, uses the very device design file  101  that a device is designed in, and which is used to manufacture the device, to navigate the device under test  114  for testing purposes. This allows the user detailed and exact layout parameters from which to specify exact locations for test implementation. As noted earlier, testing locations input  102  may comprise, for example, point and click cross-hair identification with a mouse or, alternatively, coordinate input, all in relation to device design file  101 . 
     At input box  356  testing parameters input  106  is introduced to controller  100 . As mentioned above, testing parameters input  106  comprises testing specifications such as, but not limited to, sensor type, testing sequence, power or voltage ranges or sequences, and timing sequences, in relation to testing locations identified by  102 . 
     At process box  358 , controller  100  implements an alignment procedure to ensure that device under test  114  is accurately aligned along the axes of motion. The alignment procedure is necessary to establish a precise relative positional relationship between the locations specified by the user (testing locations input  102 ) via device design file  101  and the actual device under test  114  relative to sensor  134 . That is, sensor  134  and device under test  114  are aligned with one another so as to calibrate properly against the locations specified in device design file  101 , prior to initiating testing. This alignment utilizes motion of device holder  130  to ensure proper axial and planar alignment of the device under test  114 . Feedback front the sensor  134  verifies alignment results and adjustments can be made to all five axes until alignment meets standards set by controller  100 . 
     Operation continues with process box  360  in which controller  100 , via motion module  118  of the controller  100 , initiates the motion of all components necessary to position the sensor  134  at the first point on the device under test  114  to be tested as specified by testing locations input  102 . This automated motion may comprise motion of the device under test  114  via device holder  130 , motion of probe assembly  124  and/or motion of sensor  134 . The purpose of the motion is to align sensor  134  with the specific point of device under test  114  to be tested. Once sensor  134  is properly aligned to the desired location of device under test  114 , probe assembly  124  is lowered to contact device under test  114  to provide the required power to activate device under test  114 . 
     In the preferred embodiment of the invention, gross motion is achieved by device holder  130  for such purposes as initial alignment and motion between test points. Subsequent precise motion is achieved by sensor  134 , for such purposes as motion within a testing sequence. According to this embodiment, device holder  130  is capable of a large range of axial motion with less accuracy, and sensor  134  is capable of a much shorter range of axial motion but with great accuracy. Alternative embodiments for this motion will be obvious to someone of ordinary skill, and are considered within the scope of this disclosure and its associated claims. 
     Operation continues with process box  362 , in which controller  100  initiates the calibration of sensor  134 . The specifics of the calibration routine will vary dependent upon the specific type of sensor  134  being used. However, calibration  362  comprises a combination of input from motion module  118  and data acquisition module  120  of controller  100 . Typically, the calibration routine will test the operation of the sensor  134  to ensure that it is in a proper operating range and produces accurate and expected results. 
     Operation continues with process box  364 , in which controller  100  initiates the acquisition of the data specified by the user in testing parameters input  106 . This operation may employ one or more of data acquisition module  120 , power supply module  116  and motion module  118  of controller  100 . The specified test is implemented by sensor  134  and results sent to data acquisition module  120  of controller  100 . At the end of the acquisition of the desired raw test data, probe assembly  124  is typically raised to cease power to device under test  114 . This allows for ease of motion to the next desired testing point or replacement of the device under test  114 . This cessation of power prior to movement is particularly required for wafer level testing, since each structure has an independent set of pads from which it draws power. 
     Operation continues with decision box  366  in which controller  100  is queried internally based on testing location input  102  whether there is another point to be tested. If there is another point to be tested, operation loops back to just above process box  360  and continues again from there. This loop continues until all points specified by testing locations input  102  have been tested. Once the internal query is negative, the operation continues with process box  368  in which all raw test data is transferred from the data acquisition module  120  to data processing module  140  of controller  100 . 
     Once the raw test data is processed in data processing module  140 , operation completes with output box  370  in which the processed test data is presented  144  by controller  100  to the user  144  for additional manipulation or storage. 
     A first alternative embodiment of the invention is presented in FIG. 4 in which the testing components such as the device under test  114 , probe assembly  124 , device holder  130 , and sensor  134  are enclosed within a vacuum chamber  466  to allow for specialized testing sequences requiring vacuum conditions. Aside from this creation of the vacuum conditions, the system operates exactly as described above. The vacuum conditions are specified by the user among testing parameters input  106 , transferred as vacuum control parameters  470  to vacuum control module  468  and implemented by the controller  100  along pathway  472 . Alternatively, the vacuum specifications can be manually implemented by the user. Vacuum system control parameters that must be monitored for testing under vacuum conditions include but are not limited to a vacuum pressure sensor within a vacuum vessel, a vacuum pump, venting valves for vacuum elimination, and bleed valves for vacuum pressure control and regulation. The primary purposes for testing microsystems components in a vacuum environment is to mimic actual operating conditions or to provide a testing environment in which the Microsystems devices are not subjected to effects of atmospheric pressure during operation. 
     Another significant alternative embodiment to the present invention is a simplified system in which there is no need for a device design file  101  or testing location information  102  along input train  104 . The only input to the system comprises testing parameters  106  along input path  104 . The testing parameters  106  comprise power supply parameters  108 , motion parameters  110 , and data acquisition parameters  112 . In this embodiment, the sensor  134  is essentially used to scan a designated area of the entire device under test  114 . This embodiment is useful if no device design file  101  is available to the user. With the sensor  134  being the single point reflectometer as in the preferred embodiment, the output  144  essentially comprises device identification and location information as preliminary results to be used to specify more exact testing sequences. 
     Further alternative embodiments include modifications to the operation of the invention as presented in the flowchart in FIG.  3 . For example, the calibration of sensor  134  in process box  362  is only required to precede the acquisition of raw test data in process box  364 , but is not required to follow any operation except the testing locations and testing parameters input ( 102  and  106 ) represented by input boxes  354  and  356 . Therefore, the calibration of the sensor  134  (process box  362 ) can occur either before, after or in between process boxes  358  and  360 . Similarly, if multiple points or structures are to be measured, the acquired raw test data can be moved to data processing module  140  before the controller  100  moves on to the next structure. That is to say, in FIG. 3, process box  368  can be moved above decision box  366  without disrupting the operational flow. Other, similar modifications may occur to someone of ordinary skill and are considered to be within the scope of this invention and its associated claims. 
     A further alternative embodiment involves motion module  110  and its axial control of device holder  130 , sensor  134  and probe assembly  124 . Although specific axes of motion for the preferred embodiment were detailed above, alternative axes of motion for each of the three components  130 ,  134  and  124  controlled by the motion module  110  are possible. That is to say that the motion is not limited to that described in the preferred embodiment, but can be established in a number of ways that will be apparent to someone of ordinary skill. 
     While only certain preferred features of the invention have been illustrated and described, many modifications, changes and substitutions will occur to those skilled in the art. It is, therefore, to be understood that this disclosure and its associated claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.