Abstract:
A micromechanical sensor having an analyzer circuit and at least two detecting elements, each of the two detecting elements being connected to the analyzer circuit by at least one signal line. At least one signal line is connected to both detecting elements.

Description:
BACKGROUND INFORMATION 
   Micromechanical sensors according to the prior art have a certain number of signal lines per sensor unit, these lines connecting the actual pickup to an electronic analyzer. With advances in integration, multiple pickups are integrated into one micromechanical sensor to form a multichannel sensor, for example, or to perform a plausibility check on the results. The number of signal lines is many times greater here. Due to the further miniaturization of micromechanical function elements, the areas for connections such as signal lines and bond pads are taking up a growing amount of the total substrate surface area of a micromechanical sensor. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a micromechanical sensor having an analyzer circuit and at least two detecting elements, each of the two detecting elements being connected to the analyzer circuit by at least one signal line. The core of the present invention is that at least one signal line is connected to the two detecting elements. 
   It is advantageous here that, through the joint use of signal lines, there is a savings in terms of the substrate surface area of the micromechanical sensor for these lines and for unneeded bond pads. 
   In a preferred embodiment of the present invention, each of the two detecting elements is constructed so that the measured value is represented in the form of a differential capacitance. The capacitive measuring method, in particular the measurement of differential capacitances, is a standard measurement method in micromechanical sensors. Four signal lines to the electronic analyzer are needed for one detecting element. In integrating additional detecting elements into the micromechanical sensor, the result is a considerable potential savings in terms of signal lines. 
   According to another embodiment of the present invention, the analyzer circuit is provided on a first substrate and at least two detecting elements are provided on a second substrate, and the first and second substrates are connected by a signal line. 
   Such a signal line is known as a substrate line. It connects the substrates of the detecting element and the analyzer circuit to one another. It is advantageous here that the detecting elements are situated on a common substrate because a joint substrate line may then be provided from the detecting elements to the analyzer circuit. 
   According to a particularly advantageous embodiment of the present invention, when there are N detecting elements the sensor has N+3 signal lines. In the case of a pickup having four signal lines, as in the example of the pickup according to the principle of differential capacitance and when all the detecting elements are situated on a common substrate and the analyzer device is situated on another substrate, N+3 is the smallest possible number of signal lines for connecting N detecting elements to the analyzer device. 
   According to another embodiment of the present invention, the analyzer circuit is provided on a first substrate, the first detecting element is provided on a second substrate and at least the second detecting element is provided on a third substrate. The first and second substrates are then interconnected by a first signal line, and the first and third substrate are interconnected by a second signal line. It is advantageous here that individual pickups situated on their own substrates are provided in any desired location in the micromechanical sensor and may be connected to the analyzer device. 
   According to another advantageous embodiment of the present invention, when there are N detecting elements the sensor has 2N+2 signal lines. In the case of a pickup having four signal lines as in the example of the pickup according to the principle of differential capacitance and when each detecting element is provided on its own substrate and the analyzer device is situated on another substrate, then 2N+2 is the smallest possible number of signal lines for connecting N detecting elements to the analyzer device. However, the N detecting elements may also be situated on a joint substrate and each may nevertheless have its own substrate line for connecting to the analyzer device in order to avoid the effects of residual capacitance on the substrate, for example. Again in this case, 2N+2 is the smallest possible number of signal lines for connecting N detecting elements to the analyzer device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows schematically the capacitive detecting element of a micromechanical sensor according to the prior art. 
       FIG. 2  shows schematically a micromechanical sensor according to the prior art having two capacitive detecting elements. 
       FIG. 3  shows a micromechanical sensor according to the present invention having two capacitive detecting elements and five signal lines. 
       FIG. 4  shows another embodiment of the micromechanical sensor according to the present invention having two capacitive detecting elements and six signal lines. 
   

   DETAILED DESCRIPTION 
   The present invention will be described in greater detail on the basis of the exemplary embodiments described below. 
     FIG. 1  shows schematically a capacitive detecting element of a micromechanical sensor according to the prior art. The detecting element operates according to the principle of differential capacitance. A first electrode  11  is stationary and opposite a second electrode  12  that is movable. Opposing electrodes  11 ,  12  together form a capacitor having a variable plate spacing. Movable electrode  12  together with another stationary electrode  13  forms a second capacitor having a variable plate spacing. Movable electrode  12  is attached to a seismic mass  9 . Deflections in the seismic mass along direction  14  result in measurable changes in capacitance between electrodes  11 ,  12  and  12 ,  13 . The detecting element described here is connected to an analyzer circuit by four signal lines. Signal line  1  is connected to stationary electrode  11 , signal line  2  is connected to movable electrode  12  and signal line  3  is connected to stationary electrode  13 . Signal line  4  is known as a substrate line, connecting the substrate of the detecting element to the analyzer circuit. 
     FIG. 2  shows a micromechanical sensor having two capacitive detecting elements according to the prior art. The micromechanical sensor in this example has a micromechanical measuring unit  20  and an electronic analyzer device  21 . Measuring unit  20  includes two capacitive detecting elements (not shown here). The first detecting element has signal lines  1  through  4  and the second detecting element has signal lines  5  through  8 . These signal lines are connected to electronic analyzer device  21  via contacting surfaces (bond pads)  22  and  23 . In contrast with a single-channel sensor, a two-channel sensor has twice as many signal lines. Signal lines  1  through  8  and sixteen bond pads  22 ,  23  take up a considerable amount of the chip surface area of detecting element  20  and analyzer device  21 . 
     FIG. 3  shows a first embodiment of a micromechanical sensor according to the present invention having two capacitive detecting elements. Former signal lines  1  and  5  now together form a single signal line  31 . Former signal lines  3  and  7  now together form joint signal line  33 . In addition, former substrate lines  4  and  8  now form joint substrate line  34 . On the whole, only five signal lines  2 ,  6 ,  31 ,  33 ,  34  and ten bond pads  22 ,  23  are provided through the circuitry of the two capacitive detecting elements according to the present invention to connect micromechanical measuring unit  20  to electronic analyzer device  21 . 
     FIG. 4  shows another embodiment of a micromechanical sensor according to the present invention having two capacitive detecting elements. However, in contrast with the exemplary embodiment described in conjunction with  FIG. 3 , substrate lines  4  and  8  of the two capacitive detecting elements are still carried separately in this embodiment, as in the related art. This embodiment may be expedient when the detecting elements are on different substrates (e.g., as shown schematically by elements  44  and  88 ) or when influences on the measurement due to residual capacitances are to be prevented. In this example, micromechanical measuring unit  20  and electronic analyzer device  21  are interconnected by six signal lines  2 ,  4 ,  6 ,  8 ,  31 ,  33  and twelve bond pads  22 ,  23 .