Patent Publication Number: US-2005116729-A1

Title: Method and device for testing or calibrating a pressure sensor on a wafer

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application is a continuation of copending International Application No. PCT/EP02/06350, filed on Jun. 10, 2002, which designated the United States and was not published in English. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a method and a device for testing or calibrating a pressure sensor on a wafer.  
      2. Description of the Related Art  
      Microelectronic circuits formed in or on a wafer are usually tested before dicing the wafer and housing the individual circuits. These tests are performed by automatic wafer probers or wafer testers. A wafer prober includes a handling system or handling means taking one individual wafer from a storage unit (rack) and passing it to the actual prober. The wafer is placed on a moveable carrier plate, the so-called chuck, and is fixed there by suction or electrostatically or with the help of an adhesive layer. The prober performs an exact positioning of the wafer to be tested in all three space directions. After the positioning of the wafer to be tested has been performed, exactly one respective integrated circuit of the wafer is put below an immovably arranged probe card. The probe card has a plurality of wolfram pins or needles, the arrangement of which exactly corresponds to the geometry of the microscopic pads on the integrated circuit. For contacting the integrated circuit, the chuck is moved in height or the z direction perpendicularly to the wafer plane until the probes of the probe card touch the pads and thus form electrically conductive connections to them. Electrical signals are supplied to the integrated circuit or electrical signals produced by the integrated circuit are tapped via macroscopic taps associated to the probes of the probe card and connected to them in an electrically conductive way.  
      A probe card can contact a respective or several integrated circuits at one time. For sequentially contacting and testing all the integrated circuits, the wafer with the chuck is repeatedly moved by predetermined distances parallel to the wafer plane and driven to the probes of the probe card. Since the exact positions of all the integrated circuits on a wafer are known, a single positioning of the wafer is thus sufficient. The wafer prober is connected to a computer or a workstation of a testing system, respectively, via a serial interface so that a test program executed by the testing system or the computer can communicate to the wafer prober.  
      If the integrated circuit includes a pressure sensor, only a test of electrical functions and functionalities of the integrated circuit is possible with the wafer prober described above. After the test, the wafer is diced and electrically functioning integrated circuits are housed, i.e. inserted or potted in a case. Subsequently, a test and a calibration, if suitable, of the diced and housed pressure sensors are performed.  
      This procedure has the disadvantage that defect pressure sensors are housed, too, since their defect will only be recognized after dicing and housing. In addition, testing the diced and housed pressure sensors is complicated and expensive since every single pressure sensor must be handled, positioned and contacted. Thus, cost reasons prevent an application of pressure sensors in a number of products. In some products, the calibration described cannot be performed after dicing and housing for technological reasons. A further disadvantage is that, for storing or programming calibration coefficients or calibration parameters into the pressure sensor or the integrated circuit of it or an integrated memory element (such as, for example, an EEPROM), the case may have to have one or several additional contacts which are only used once, that is when calibrating the pressure sensor, which, however, increases the production cost and increases the danger of damage or destruction of it during the entire life time of the pressure sensor.  
     SUMMARY OF THE INVENTION  
      It is the object of the present invention to provide an improved test or calibration method for a pressure sensor, a method for manufacturing a pressure sensor and a device simplifying testing and calibrating a pressure sensor.  
      In accordance with a first aspect, the present invention provides a method for testing or calibrating a pressure sensor of a plurality of pressure sensors formed in a wafer, wherein the pressure sensor has a pressure-sensitive portion and a signal output, wherein the signal output includes pads, and wherein the pads and the pressure-sensitive portion are arranged on a surface of the wafer, including the following steps: providing a probe card having probes with probe tips, wherein the probe card has an upper side and a lower side, wherein the lower side of the probe card is directed towards the surface of the wafer, wherein the probes are arranged on the lower side of the probe card, and wherein a sealing lip surrounding the probe tips is further attached on the lower side of the probe card; connecting the pressure-sensitive portion of the pressure sensor to the fluid line in a pressure-tight way by contacting the sealing lip with the surface of the wafer, wherein the probe tips are further electrically connected to the pads; applying a predetermined pressure to the pressure-sensitive portion of the pressure sensor via the fluid line; and receiving a signal from the signal output of the pressure sensor via the probes of the probe card.  
      In accordance with a second aspect, the present invention provides a method for manufacturing a pressure sensor element, including the following steps: providing a wafer having a plurality of pressure sensors, wherein each pressure sensor has a pressure-sensitive portion and a signal output; applying a method to one of the plurality of pressure sensors, the method being for testing or calibrating a pressure sensor of a plurality of pressure sensors formed in a wafer, wherein the pressure sensor has a pressure-sensitive portion and a signal output, wherein the signal output includes pads, and wherein the pads and the pressure-sensitive portion are arranged on a surface of the wafer, the method including the following steps: providing a probe card having probes with probe tips, wherein the probe card has an upper side and a lower side, wherein the lower side of the probe card is directed towards the surface of the wafer, wherein the probes are arranged on the lower side of the probe card, and wherein a sealing lip surrounding the probe tips is further attached on the lower side of the probe card, connecting the pressure-sensitive portion of the pressure sensor to the fluid line in a pressure-tight way by contacting the sealing lip with the surface of the wafer, wherein the probe tips are further electrically connected to the pads, applying a predetermined pressure to the pressure-sensitive portion of the pressure sensor via the fluid line, and receiving a signal from the signal output of the pressure sensor via the probes of the probe card; dicing the wafer after applying the method to obtain the diced pressure sensor; and housing the diced pressure sensor to obtain the pressure sensor element.  
      In accordance with a third aspect, the present invention provides a device for applying a certain pressure to a pressure sensor of a plurality of pressure sensors formed in a wafer and for receiving a signal from a signal output, having pads, of the pressure sensor, wherein the pressure sensor has a pressure-sensitive portion, and wherein the pads and the pressure-sensitive portion are arranged on a surface of the wafer, including means for providing a probe card having probes with probe tips, wherein the probe card has an upper side and a lower side, wherein the lower side of the probe card is directed towards the surface of the wafer, wherein the probes are arranged on the lower side of the probe card, and wherein a sealing lip surrounding the probe tips is further arranged on the lower side of the probe card; means for connecting the pressure-sensitive portion to the fluid line provided for supplying the predetermined pressure in a pressure-tight way by contacting the sealing lip with the surface of the wafer, wherein the probe tips are further electrically connected to the pads; and means for receiving the signal from the signal output of the pressure sensor via the probes of the probe card.  
      In accordance with a fourth aspect, the present invention provides a probe card for testing or calibrating a pressure sensor of a plurality of pressure sensors formed in a wafer, wherein the pressure sensor has a pressure-sensitive portion and a signal output, wherein the signal output includes pads, and wherein the pads and the pressure-sensitive portion are arranged on a surface of the wafer, including: a probe card body having an upper side and a lower side, wherein the lower side of the probe card is to be directed towards the upper side of the wafer when the pressure sensor is tested of calibrated; probes with probe tips arranged on the lower side of the probe card; and a sealing lip attached to the lower side of the probe card such that it surrounds the probe tips.  
      The present invention is based on the finding of testing or calibrating pressure sensors, in particular surface-micromechanical absolute pressure sensors, and in particular pressure sensors provided for a negative pressure range, still in a wafer, i.e. before dicing it. For this, a pressure-sensitive portion of the pressure sensor is connected to a fluid line for example by means of a sealing lip via which one or subsequently several predetermined pressures can be applied to the pressure-sensitive portion of the pressure sensor. Preferably, simultaneously to or after applying a pressure, a signal produced by the pressure sensor responsive to the pressure on a signal output is received. For this, the test or calibration is preferably performed by means of an automatic wafer tester with a probe card, wherein the sealing lip is arranged between the probe card and a surface of the wafer where the pressure-sensitive portion of the pressure sensor is arranged. This sealing lip surrounds the pressure-sensitive portion, the probes of the probe card and the pads of the pressure sensor laterally for example in the form of a circle or of a rectangle and seals the gap between the surface of the wafer on the one hand and the probe card in which the pressure-sensitive portion of the pressure sensor is arranged on the other hand in a pressure-tight way relative to the environment. Preferably, a standard wafer tester is modified and particularly provided with the sealing lip below the probe card.  
      An opening often present in conventional probe cards above the probe tips may be closed in a pressure-tight way by means of a cap preferably comprising a transparent material, such as, for example, PMMA (poly methyl methacrylate). A fluid line thus connects the completely pressure-tight surrounded cavity between the surface of the wafer, the probe card and the cap to a pressure system producing the one or several predetermined pressures.  
      It is an advantage of the present invention that the pressure sensors can be tested or calibrated on the wafer not yet diced. This can take place simultaneously to a test of the electrical features of the integrated circuit or its functionality. Repeated handling, positioning and contacting the diced and housed pressure sensors are thus not required. Defect pressure sensors will not be housed since they have already been identified. Corresponding to the resulting simplification and shortening of the manufacturing process in the area of testing and calibrating, considerable cost advantages result which, as far as economics is concerned, enable the usage of integrated pressure sensors in many products. In addition, the present invention makes possible the usage of integrated pressure sensors in products in which testing or calibrating cannot be performed after dicing for technological reasons. The housed pressure sensor and its housing, respectively, need not comprise contacts for transferring calibration coefficients into an integrated memory element (such as, for example, an EEPROM). Thus, size and production cost of the casing can be produced and the risk of a future damage of these contacts can be avoided. A further advantage of the present invention is that it can be implemented by modifying a conventional wafer tester. The present invention thus only produces small investment cost.  
      A preferred field of application of the present invention is manufacturing absolute pressure sensors, in particular in a negative pressure range between 0 and 1 bar and, in particular, surface-micromechanical absolute pressure sensors in high numbers and, in particular, for fields of application in which the customer, after inserting the absolute pressure sensor into an entire system, does not have the possibility for calibrating the sensor.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Preferred embodiments of the present invention will be detailed subsequently referring to the appended drawings, in which:  
       FIG. 1  is a schematic illustration of a pressure sensor testing system according to the present invention;  
       FIG. 2  is a schematic sectional illustration of an inventive device;  
       FIGS. 3A and 3B  show a schematic top view of a wafer and a schematic sectional illustration of a sealing lip according to the present invention; and  
       FIGS. 4A and 4   b  show a schematic top view and a schematic sectional illustration of a cap according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      In  FIG. 1 , a schematic illustration of a testing system according to a preferred embodiment of the present invention is shown. A wafer  10  is held by a wafer carrier or chuck  12  of a prober  14  by means of a negative pressure, electrostatically or by means of an adhesive layer and is positioned in all three space directions. On a surface  20  of the wafer  10 , a plurality of non-illustrated pressure sensors preferably having the same setup among one another and arranged in a regular raster are arranged. Each pressure sensor includes a pressure-sensitive portion, a mechanical-electrical transducer and a signal output.  
      In the case of a piezoelectric pressure sensor, the mechanical-electrical transducer is a solid body containing a piezo-effect, such as, for example, a piezoelectric crystal having a surface representing the pressure-sensitive portion of the pressure sensor.  
      In the case of a capacitive pressure sensor, the mechanical-electrical transducer is a capacitor, the capacitor plate of which is a diaphragm deformable by a pressure, the surface of which represents the pressure-sensitive portion of the pressure sensor. The signal output of the pressure sensor has a plurality of pads via which an electrical power, an electrical voltage or another electrical signal can be fed to the pressure sensor, if required, and via which a signal produced or influenced by the pressure sensor can be tapped.  
      In addition, each pressure sensor can have an integrated circuit connected between the mechanical-electrical transducer and the pads for generating, processing or transducing electrical signals. If the above-mentioned capacitive pressure sensor is provided for being supplied with a direct voltage, the integrated circuit will preferably comprise an oscillator based on a comparator. The capacitor including the diaphragm is charged by a predetermined current, wherein the comparator compares the voltage at the capacitor to a reference voltage. As soon as the voltage at the capacitor reaches the reference voltage, switching from the charging process to a discharging process takes place. This discharging process is, controlled by a second comparator, either disrupted when dropping below a second reference voltage or a complete discharge is performed via a short-circuit. Charging and discharging processes are repeated cyclically, wherein a sequence of zeros and ones is produced. The period Δt of the charging/discharging cycle and the sequence of zeros and ones, respectively, due to the pressure-dependence of the capacity of the capacitor, are a function of the pressure. Alternatively or in addition to a digital output signal, the integrated circuit can also produce an analog output signal.  
      Alternatively, the integrated circuit of the capacitive pressure sensor comprises a resonator in which the capacitor including the diaphragm is integrated as a device determining the characteristic frequency. In this case, the pressure sensor may additionally comprise a transducer transducing the resonance frequency of the oscillator influenced by the pressure into an analog or digital signal.  
      In the above-mentioned case of the pressure sensor with a piezoelectric mechanical-electrical transducer, the integrated circuit is preferably provided for amplifying, impedance-transducing or digitalizing the output signal of the piezoelectric sensor. Preferably, the integrated circuit further has an analog or digital memory for storing one or several calibration coefficients with the help of which it produces a calibrated output signal of the pressure sensor.  
      A probe card  30  having a plurality of probes is arranged opposite the surface  20  of the wafer  10 . The lateral arrangement of the probes and the probe tips, respectively, corresponds to the lateral arrangement of the pads of a pressure sensor. In a corresponding relative space arrangement of the wafer  10  and the probe card  30 , the probes of the probe card  30  contact the pads of one of the pressure sensors of the wafer  10  so that via the probes an electrical power or an electrical signal can be fed to the pressure sensor an electrical signal produced or influenced by the pressure sensor can be tapped.  
      The probe card  30  has an opening  32  below which the tips of the non-illustrated probes are arranged. Above the opening  32  there is a cap  34  connected to the probe card  30  in a pressure-tight way. Between the probe card  30  and the surface  20  of the wafer  10 , there is a sealing lip  36  surrounding the opening  32  and the probes and their tips, respectively, in a lateral direction for example in the form of a circle or a rectangle. In a relative space arrangement of the probe card  30  and the wafer  10  in which the probes of the probe card  30  contact the pads of a pressure sensor on the surface  20  of the wafer  10 , the sealing lip  36  forms a pressure-tight connection of the probe card  30  to the surface  20  of the wafer  10  so that a cavity  38  sealed relative to the environment in a pressure-tight way is formed between the cap  34 , the probe card  30 , the sealing lip  36  and the surface  20  of the wafer  10 . In particular the pressure-sensitive portion of the pressure sensor is arranged in this cavity  38 .  
      Before other structures and functional elements illustrated in  FIG. 1  are discussed, the cavity  38 , the sealing lip  36  and the cap  34  will first be explained in greater detail referring to  FIG. 2, 3A ,  3 B,  4 A and  4 B.  FIG. 2  shows an enlargement of a section of  FIG. 1  in which the cavity  38  is illustrated in a cross section resulting when, by a corresponding relative space arrangement of the probe card  30  and the wafer  10  and its surface  20 , respectively, probes  40  of the probe card  30  touch the non-illustrated pads of the pressure sensor on the surface  20  of the wafer  10  and contact them. The sealing lip  36 , such as, for example, a soft silicone lip, is arranged on the lower side  44  of the probe card  30 , wherein the exterior border  48  of the sealing lip is, for example, connected to the lower side  44  of the probe card  30  in a pressure-tight way by gluing.  
      The sealing lip  36  approximately has the form of a cover area of a flat truncated cone or of a flat truncated pyramid. Near its inner edge  50 , the sealing lip  36  comprises a circulating border  52  directed to the surface  20  of the wafer  10 , touching the surface  20  and forming a pressure-tight connection with it.  
      The cap  34  is arranged on an upper side  56  of the probe card  30  and, for example by means of gluing, connected to the probe card  30  so that it closes the opening  32  of the probe card  30  in a pressure-tight way. A bore or venting channel  60  connects the miniature pressure chamber or vacuum chamber or cavity  38  between the cap  34 , the probe card  30 , the sealing lip  36  and the surface  20  of the wafer  10  to a pressure system illustrated below referring to  FIG. 1  for setting a predetermined pressure in the cavity  38 .  
      As can be seen from  FIG. 2 , construction and setup of the sealing lip  36  are simplified for geometrical reasons when the probes  40  have a large as possible angle to the lower side  44  of the probe card  30 . A preferred value of the angle between the probes  40  and the lower side  44  of the probe card  30 , with which the present invention has been tested successfully, is 10 degrees.  
       FIG. 3A  is a schematic top view of a plurality of pressure sensors on a surface  20  of a wafer  10 , for the manufacturing of which the present invention can be employed. In  FIG. 3A , like in the following  FIGS. 3B, 4A  and  4 B, some typical dimensions, which are, however, only indicated exemplarily, are indicated. The individual pressure sensors  54  have a length of 2.12 mm and a width of 2.11 mm and are arranged in an approximately square raster having a mutual pitch of 0.2 mm on the surface  20  of the wafer  10 . Each pressure sensor  54  has a pressure-sensitive portion, pads for electric contacting and, preferably, an integrated circuit.  
       FIG. 3B  is a schematic illustration of the sealing lip  36  in a section perpendicularly to the surface  20  of the wafer  10 . In this embodiment, the sealing lip  36  is provided to surround  64  of the pressure sensors  54  illustrated in FIG.  3 A. When the probe card  30  has probes  40  for simultaneously contacting all the pads of all the 64 pressure sensors  54  laterally surrounded by the sealing lip  36 , these 64 pressure sensors can be tested or calibrated simultaneously.  
      The exterior border  48  of the sealing lip  36  laterally preferably has the form of a circle having a diameter of 30 mm, the interior border  50  of the sealing lip  36  laterally preferably has the form of a circle having a diameter of 15 mm. Somewhat outside the interior border  50 , the sealing lip  36  has an edge  52  laterally approximately having the form of a square having a side length of 18.48 mm and 18.56 mm and thus, as has been described above, exactly surrounding  64  pressure sensors. The edge  52  compared to the inner border projects vertically  50  by 0.5 mm. The angle by which the sealing lip  36  deviates from a plane is 10°.  
       FIGS. 4A and 4B , in a schematic top view and a schematic sectional illustration, respectively, show the cap  34 .  FIG. 4B  thus shows a section perpendicularly to the surface  20  of the wafer  10 . The cap  34  is basically axially symmetric. Its exterior diameter is 60 mm. In the middle of the surface  64  facing the probe card  30 , the cap  34  has a nose or projection  66  projecting into the opening  32  of the probe card  30 . This projection  66  decreases the volume of the cavity  38 , whereby setting a predetermined pressure in the cavity  38  is accelerated. Apart from the projection  66 , the cap  34  has the form of a circular disc having two plane parallel surfaces, a thickness of 10 mm and a circular 5 mm deep recess  68  compared to the projection  66 .  
      The cap  34  further comprises the bore or venting channel  60  via which pressure compensation takes place between the cavity  38  and the other pressure system described below referring to  FIG. 1 . The venting channel  60  ends in the area of the projection  66 .  
      It can also be seen that the cap  34 , close to its exterior circumference  70 , has fixing bores  72  having one or several cut-in threads for mechanically fixing the cap  34  on a special device for mechanical stabilization. This device for mechanical stabilization is required since otherwise even a small negative or positive pressure in the cavity  38  causes deformation or bending of the probe card usually consisting of an FR4 board. A negative pressure results in a decrease in the distance between probe card and wafer. This decrease in the distance has the effect that the tips of the probes on the surface  20  of the wafer  10  are shifted that much that they leave the pads and damage the surrounding areas of the chip surface. In order to prevent this, probe card  30  and cap  34  are mechanically stabilized by the mentioned device not illustrated in the Figures.  
      The cap  34  is preferably formed of a transparent material, such as, for example, acrylic plastic or acrylic glass or PMMA (poly methyl methacrylate), respectively. For adjusting purposes, it is possible to look at the IC or pressure sensor to be detected through the cap  34  by means of a microscope or a camera part.  
      In the following, the pressure system with which the cavity  38  is connected via the venting channel  60  and by means of which predetermined pressures p 1 , p 2 , p 3  in the cavity  38  are set will be discussed in greater derail referring to  FIG. 1 . A pressure providing system  100  provides two different predetermined pressures p 1 , p 2  via pressure tanks  102 ,  104 , wherein the pressures, controlled by means described below, can be applied to the cavity  38  in an alternating way. A control PC on which control software or a control program is executed, is connected to a pressure calibrator  120  via a data bus  112 , such as, for example, a GPIP bus. The pressure calibrator  120  is connected to a reference vacuum pump  126  and a vacuum pump  128  via vacuum lines  122 ,  124 . Controlled by the control PC  110 , the pressure calibrator  120  alternatingly produces the two pressures p 1 , p 2  to be applied to the cavity  38  and thus the pressure-sensitive portion of the pressure sensor to be tested or to be calibrated.  
      The control PC  110  is further, via a data bus  132  again preferably being a GPIP bus, connected to a voltage source  134  for generating two voltages. These two voltages are applied to magnetic control valves Va  152  and Vb  154  via control lines  142 ,  144  to open and close them. The magnetic control valves Va  152  and Vb  154  are, on the pressure input side, connected to the pressure calibrator  120  via a branched vacuum line  156 . On the pressure output side, the magnetic control valve Va  152  is connected to the first pressure tank  102  via a vacuum line  162  and the magnetic control valve Vb  154  is connected to the second pressure tank  104  via a vacuum line  164 .  
      The pressure providing system  100 , as a self-contained system, independently of further components of the pressure system described below, provides two predetermined pressures p 1 , p 2  in the pressure tanks  102 ,  104 . For this, the control PC or the control program executed on it controls the pressure calibrator  120  and the magnetic control valves Va  152  and Vb  154  via the data busses  112 ,  132  and the voltage source  134 . The pressure calibrator  120  alternatingly produces the first predetermined pressure p 1  to be provided in the first pressure tank  102 , wherein, at the same time, only the first pressure tank  102  is connected to the pressure calibrator  120  by an open magnetic control valve Vb  152  and a closed magnetic control valve Vb  154  and the second predetermined pressure p 2  to be provided in the second pressure tank  104 , wherein only the second pressure tank  104  is connected to the pressure calibrator  120  via a closed magnetic control valve Va  152  and an open magnetic control valve Vb  154 .  
      The pressure tanks  102 ,  104  are connected to one magnetic control valve V 1   182  or V 2   184  each via vacuum lines  172 ,  174 . The magnetic control valves V 1   182  and V 2   184  are also, in parallel to a magnetic control valve V 3   190 , connected to a pressure load or pressure measurement cell  194  via a multiple branched vacuum line  188  and connected to the cavity  38  via the venting channel  60 . The magnetic control valve V 3   190  is also connected to the surrounding atmosphere.  
      The magnetic control valves V 1   182 , V 2   184  and V 3   190 , in  FIG. 1 , are illustrated as 3-way valves which are, however, only used as 2-way valves and the respective third input/output of which is closed continually. The reason for the usage of 3-way valves as 2-way valves is the small selection of pneumatic valves suitable for the usage in a negative pressure range.  
      A main frame  200  controlling testing and/or calibrating the pressure sensors is connected to a test head  204  via an interface  202 , preferably a TH-MF interface. The test head  204  receives a pressure load signal from the pressure load cell  194  via the control line  210  and transmits control signals for the magnetic control valves V 1   182 , V 2   184  and V 3   190  via control lines  212 ,  214 ,  216 . A test program executing on the main frame  200  can thus control the pressure applying in the cavity  38  and thus the pressure-sensitive section of the pressure sensor to be tested or to be calibrated via the test head  204  and by means of the magnetic control valves V 1   182 , V 2   184  and V 3   190 .  
      In an output position, the valves V 1   182  and V 2   184  are closed and the valve V 3   190  is open. In this case, the system, in particular the cavity  38 , is vented and ambient pressure p 3  is present. If the magnetic control valves V 3   190  and V 2   184  are closed and the magnetic control valve V 1   182  is open, there is a fluid communication between the first pressure tank  102  and the cavity  38 . The first predetermined pressure p 1  provided in the first pressure tank forms in the cavity  38 . If the magnetic control valves V 3   190  and V 1   182  are closed and the magnetic control valve V 2   184  is open, there is a fluid communication between the second pressure tank  104  and the cavity  38 . Consequently the second predetermined pressure p 2  provided in the second pressure tank  104  forms in the cavity  38 . As soon as the main frame  200  receives a pressure load signal from the pressure load cell  194  via the test head  204 , the signal indicating that a pressure corresponding to the position of the valves V 1   182 , V 2   184  and V 3   190 , that is one of the predetermined pressures p 1 , p 2  or ambient pressure p 2 , has formed in the cavity  38 , a test program routine is started. With the help of the test program routine, the pressure sensor and the integrated circuit are tested and the pressure analog sensor data or the digital or analog output signals of the pressure sensor representing the pressure detected by the pressure sensor are read out.  
      The calibration of the pressure sensor preferably takes place as is provided by the pressure system described above, at at least two different temperatures T 1 , T 2  and at at least three different pressures p 1 , p 2 , p 3  per temperature T 1 , T 2  set. From the measurement data obtained in this way, individual calibration coefficients for the pressure sensor to be calibrated are calculated subsequently and, if this is provided for the pressure sensor, stored in an integrated memory of the pressure sensor. If the pressure sensor is only tested, it will be checked whether the deviations of the measurement values determined by the pressure sensor from the respective actually applying pressures p 1 , p 2 , p 3  are within allowable limits or whether established calibration coefficients are within a predetermined range. Pressure sensors not satisfying these conditions will not be housed after subsequent dicing, but thrown away.  
      Since heating or cooling down the chuck or wafer carrier  12  and the wafer  10  takes place relatively slowly and takes a relatively long time, all the pressure sensors on a wafer are preferably measured at first at a fixedly set first predetermined temperature T 1 . Measurement data representing the functionality of the integrated circuit of the pressure sensor and the pressure measurement values of the pressure sensor for all the three predetermined pressures p 1 , p 2 , p 3  are stored in a file. Subsequently, the wafer carrier  12  and the wafer  10  or all the wafers of the rack, respectively, are heated to a second temperature T 2  and for all the pressure sensors not having been detected as defect in the first pass at the first predetermined temperature T 1 , the pressure measurement signals are detected again at the three pressures p 1 , p 2 , p 3 . In this second pass, a calibration routine is started by the test program directly after detecting the pressure measurement signals of a pressure sensor. The calibration routine determines individual calibration coefficients for the respective pressure sensor from the measurement data for the first predetermined temperature T 1  stored in the file and the measurement data for the second predetermined temperature T 2  and, if suitable, stores them in a memory of the integrated circuit of the pressure sensor provided for the calibration coefficients.  
      Depending on the physical measuring principle of the pressure sensor and the requirements posed by the application for which the pressure sensor is provided, calibration, due to measurements, can take place at only one or more than two temperatures as well as one, two or four or more pressures. Thus, the probe card  30  can contact only one respective individual pressure sensor or a plurality of pressure sensors at the same time. If the sealing lip  36  also surrounds this plurality of simultaneously contacted pressure sensors so that the predetermined pressure p 1 , p 2  or ambient pressure p 3  is applied simultaneously to all the contacted pressure sensors or their pressure-sensitive portions, respectively, all the contacted pressure sensors can be calibrated simultaneously.  
      If the probe card  30  and the sealing lip  36  do not contact or surround all the pressure sensors of the wafer  10  simultaneously, the wafer  10 , after measuring, testing or calibrating a group of pressure sensors, will be moved away a little from the probe card  30 , so that the probes  40  do not touch the pads of the pressure sensors anymore and the edge  52  of the sealing lip  36  does no longer touch the surface  20  of the wafer  10 . The wafer  10  is then moved in a lateral direction by a distance corresponding to the raster measure with which the pressure sensors are arranged on the surface  20  of the wafer or to a multiple of it. Subsequently, the wafer  10  with the wafer carrier  12  is moved again in the direction of the probe card  30  so that the probes  40  contact the pads of the pressure sensors on the surface  20  of the wafer  10  and the edge  52  of the sealing lip  36  completely contacts the surface  20  of the wafer  10 . Subsequently, one or several pressure sensors not having been measured, tested or calibrated so far are measured, tested or calibrated, respectively.  
      The pressure providing system  100  described above is provided for producing negative pressures or pressures smaller than ambient pressure. The present invention is, however, also usable for pressure sensors and their calibration in a positive pressure range, wherein a corresponding pressure could be provided to only the pressure calibrator by a compressor or a positive pressure pump, a pressure gas bottle or the like. In addition, an expansion of the pressure providing system  100  to more than two pressures which differ from ambient pressure is possible easily.  
      For testing or calibrating pressure sensors for other gases than air or for liquids, corresponding pumps  126 ,  128 , valves  152 ,  154 ,  182 ,  184 ,  190 , pressure tanks  102 ,  104 , fluid lines  112 ,  132 ,  156 ,  162 ,  164 ,  172 ,  174 ,  188 ,  192 , a corresponding pressure load cell  194  and a corresponding pressure calibrator  120  are used.  
      The pressure load cell  194  is either, as it is illustrated in  FIG. 1 , connected to the magnetic control valve V 3   190  and the cavity  38  via a branched vacuum line  192  or connected directly to the cavity  38  via a separate vacuum  10  line or arranged in it, as has already been discussed referring to  FIG. 4 .  
      In the situation illustrated in  FIGS. 1 and 2 , the pressure sensor includes a pressure-sensitive portion on the surface  20  of the wafer  10  arranged between the pads contacted by the contact probes  40 . Although this corresponds to a common arrangement of pads on an integrated circuit or chip, respectively, the pressure-sensitive portion of each pressure sensor can also be arranged next to the pads. In this case, the contact probes  40  of the probe card  30  can be arranged outside the sealing lip  36 . Differing from the embodiment illustrated in  FIGS. 1 and 2 , the pressure sensor may have an optical signal output and/or an optical power input. In this case, an optical interface, apart from a (smaller) number of probes  40  or instead of the probes  40 , respectively, is required to test the pressure sensors on the surface  20  of the wafer  10 .  
      While this invention has been described in terms of several preferred embodiments, there are alterations, permutations, and equivalents which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention.