JP6051831B2 - Evaluation device - Google Patents

Description

  The present invention relates to an evaluation apparatus used for evaluating electrical characteristics of a semiconductor device such as a semiconductor wafer or a semiconductor chip.

  A contact probe may be brought into contact with the semiconductor device to evaluate the electrical characteristics of the semiconductor device. At that time, for example, a discharge may occur between the contact probe and the semiconductor device. It is necessary to securely capture the semiconductor device in which discharge has occurred and prevent it from flowing into the market. Patent Documents 1 and 2 disclose techniques for detecting the occurrence of discharge.

  Patent Document 1 discloses a technique for detecting a discharge by determining noise and discharge generated inside a semiconductor module by measuring sound accompanying partial discharge using an acoustic emission sensor attached to the surface of the semiconductor element module. It is disclosed. Patent Document 2 discloses a technique for detecting a discharge current by current detection means.

JP 2003-130925 A JP 2002-22793 A

  If discharge occurs during the evaluation of the electrical characteristics of the semiconductor device, the semiconductor device may be deteriorated. Therefore, it is necessary to reliably detect the discharge being evaluated. In addition, it is preferable to detect the discharge by an easy method.

  The technique disclosed in Patent Document 1 requires measurement of sound accompanying discharge. However, it is difficult to measure sound accompanying discharge in evaluation of a semiconductor device in a wafer or chip state. In addition, the technique disclosed in Patent Document 2 has a problem that requires a complicated circuit and a problem that detection accuracy is reduced due to external noise.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an evaluation apparatus that can easily detect a discharge.

Evaluation device Ru engaged to the invention, the voltage and current applied to the semiconductor device, and detection and evaluation unit for evaluating the electric characteristics of the semiconductor device, the applied voltage or current to the semiconductor device, the voltage Or a discharge detector that emits a discharge notification signal when the occurrence of discharge is detected from a change in current, and a controller that stops evaluation by the evaluation unit when the discharge notification signal is received from the discharge detector; A storage unit that stores information for identifying the semiconductor device, and the discharge detection unit is predetermined in a process of increasing the voltage or current, and a detection unit that detects the voltage or current When the voltage or current does not reach the predetermined first set value even after the first set time is exceeded, or when the voltage or current exceeds the second set time set in the process of decreasing the voltage or current, Or a second setting with a predetermined current When not reached, characterized by comprising a second comparison unit for emitting said discharge notification signal to the control unit.

  According to the present invention, discharge can be easily detected.

It is a figure of the evaluation apparatus which concerns on Embodiment 1 of this invention. It is a front view of a contact probe. It is a flowchart which shows discharge detection operation | movement etc. by the evaluation apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the waveform of the voltage applied to the semiconductor device for evaluation in a high voltage. It is a figure which shows the waveform of the applied voltage when discharge generate | occur | produces during a voltage rise. It is a figure which shows the example of transition of a differential value. It is a figure which shows the discharge in the fall process of the voltage applied to a semiconductor device. It is a figure of the evaluation apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows a waveform when a voltage does not reach a 1st setting value even if it exceeds 1st setting time in the process of raising a voltage. It is a figure of the evaluation apparatus which uses together the discharge detection part of Embodiment 1 and the discharge detection part of Embodiment 2 of this invention.

  An evaluation apparatus according to an embodiment of the present invention will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repeated description may be omitted.

Embodiment 1 FIG.
FIG. 1 is a diagram of an evaluation apparatus according to Embodiment 1 of the present invention. The evaluation apparatus according to Embodiment 1 of the present invention includes a chuck stage 10. The chuck stage 10 vacuum-sucks the semiconductor device 11. An emitter electrode 11 a is formed on the upper surface of the semiconductor device 11, and a collector electrode 11 b in contact with the chuck stage 10 is formed on the lower surface. The semiconductor device 11 is formed of an IGBT having a vertical structure that allows current to flow between the emitter electrode 11a and the collector electrode 11b.

  An insulating substrate 12 is disposed above the chuck stage 10. A contact probe 14 is fixed to the insulating base 12. A plurality of contact probes 14 are formed so that a large current can be applied to the semiconductor device 11. The contact probe 14 is electrically connected to a connection portion 16 fixed to the insulating base 12 by, for example, a metal plate on the insulating base 12.

  Here, the contact probe 14 will be described in detail. FIG. 2 is a front view of the contact probe 14. The contact probe 14 includes a main body 14 a that is fixed to the insulating base 12. A telescopic portion 14b is connected to the lower portion of the main body portion 14a. The expansion / contraction part 14b has a spring or the like incorporated therein so that it can expand and contract in the longitudinal direction. A contact portion 14c is connected to the lower side of the extendable portion 14b. The tip of the contact portion 14c has a rounded shape, and this tip hits the emitter electrode 11a of the semiconductor device.

  A connection portion 14d for electrical connection of the contact probe 14 is connected above the main body portion 14a. The contact probe 14 is formed of a conductive material such as copper, tungsten, or rhenium tungsten. In order to increase the conductivity and durability of the contact portion 14c, it is preferable to coat the contact portion 14c with gold, palladium, tantalum, platinum, or the like. The contact probe 14 is gradually brought closer to the emitter electrode 11a from the initial state of FIG. 2A, and the contact portion 14c contacts the emitter electrode 11a (see FIG. 2B). Further, when the contact probe 14 is pressed in the direction of the emitter electrode 11a, the expansion / contraction part 14b contracts and the contact part 14c and the emitter electrode 11a come into contact with each other with a sufficient force.

  Returning to the description of FIG. The insulating base 12, the contact probe 14, and the connection portion 16 are collectively referred to as a probe card 18. The probe card 18 can be moved in an arbitrary direction by an arm 20 formed so as to be able to grip the insulating base 12.

  One end of a signal line 30 is connected to the connection unit 16. The other end of the signal line 30 is connected to the controller 32. The controller 32 applies voltage and current to the semiconductor device 11 in order to evaluate the electrical characteristics of the semiconductor device 11. A connection portion 34 is provided on the side surface of the chuck stage 10. The connecting portion 34 is electrically connected to the collector electrode 11 b of the semiconductor device 11 through the chuck stage 10. One end of a signal line 36 is connected to the connection portion 34. The other end of the signal line 36 is connected to the controller 32.

  The controller 32 is electrically connected to the contact probe 14 via the signal line 30 and the connection portion 16, and is electrically connected to the chuck stage 10 via the signal line 36 and the connection portion 34. When evaluating the electrical characteristics of the semiconductor device 11, the contact probe 14 is applied to the emitter electrode 11 a and the collector electrode 11 b is brought into contact with the chuck stage 10. The chuck stage 10, the insulating base 12, the contact probe 14, the connection parts 16 and 34, and the signal lines 30 and 36 that electrically connect the controller 32 and the semiconductor device 11 are collectively referred to as a measuring instrument.

  The controller 32 includes an evaluation unit 32a and a control unit 32b. The evaluation unit 32a is a part that applies a voltage and a current to the semiconductor device 11 via the measuring instrument and evaluates the electrical characteristics of the semiconductor device 11. The control part 32b is a part which stops the evaluation by the evaluation part 32a.

  A discharge detector 42 is connected to the controller 32. The discharge detection unit 42 is a part that detects a voltage or current applied to the semiconductor device 11 and detects occurrence of discharge from a change in the voltage or current. When the discharge detector 42 detects a discharge, the discharge detector 42 issues a discharge notification signal to the controller 32b of the controller 32.

  The discharge detector 42 will be specifically described. The discharge detection unit 42 includes a differential value calculation unit 42a and a first comparison unit 42b. The differential value calculation unit 42a is a part that detects the value of the voltage or current applied to the semiconductor device 11 and calculates a differential value obtained by time-differentiating it. The first comparison unit 42b compares the differential value calculated by the differential value calculation unit 42a with a predetermined threshold value, and issues a discharge notification signal to the control unit 32b when the differential value exceeds the threshold value. The function of the discharge detector 42 can be realized by using, for example, a waveform detection function of an oscilloscope. Further, instead of an oscilloscope, a combination of a digitizer and a peak hold circuit may be used.

  When the control unit 32b receives the discharge notification signal from the first comparison unit 42b, the control unit 32b stops the evaluation by the evaluation unit 32a. A storage unit 44 is connected to the controller 32 and the discharge detection unit 42. The storage unit 44 stores a threshold for each evaluation item of the semiconductor device 11. In the first comparison unit 42b described above, the threshold value stored in the storage unit 44 is used. The storage unit 44 stores information for specifying the semiconductor device 11 that has been discharged.

  The operation of the evaluation apparatus according to Embodiment 1 of the present invention will be described. FIG. 3 is a flowchart showing a discharge detection operation and the like by the evaluation apparatus according to Embodiment 1 of the present invention. First, the semiconductor device 11 is placed on the chuck stage 10 (step 100). Next, the contact portions 14c of the plurality of contact probes 14 whose positions are adjusted to be parallel are brought into contact with the emitter electrode 11a of the semiconductor device 11 (step 102). In step 102, as shown in FIG. 2, the expandable portion 14b is contracted to bring the contact portion 14c into contact with the emitter electrode 11a.

  In step 102, the emitter electrode 11 a of the semiconductor device 11 is connected to the controller 32 via the contact probe 14, the connection unit 16, and the signal line 30. Further, the collector electrode 11 b of the semiconductor device 11 is connected to the controller 32 via the chuck stage 10, the connection portion 34, and the signal line 36.

Next, voltage and current are applied from the evaluation unit 32a of the controller 32 to the semiconductor device 11 to evaluate the electrical characteristics of the semiconductor device 11 (step 104). Usually, multiple evaluation items are evaluated. In step 104, for example, the collector-emitter saturation voltage (V _CE (sat)) is evaluated.

V _CE (sat) is evaluated by applying a high voltage of several kV to the semiconductor device. In order to perform evaluation at a high voltage, the voltage applied to the semiconductor device 11 is gradually increased so as to reach a predetermined voltage (high voltage). FIG. 4 is a diagram illustrating a waveform of a voltage applied to the semiconductor device 11 for evaluation at a high voltage. As shown in FIG. 4, it is ideal that the voltage rises linearly with respect to the time axis.

  However, discharge may occur between the contact probe 14 and the semiconductor device 11 during the voltage rise, for example. FIG. 5 is a diagram showing a waveform of an applied voltage when a discharge is generated while the voltage is rising. When a temporary discharge occurs, the voltage drops like the A region, but then returns to the voltage rising process again. However, when continuous discharge occurs, the voltage drops as in the B region, and the voltage cannot be increased to the set value.

In the process of increasing the applied voltage of the semiconductor device 11 in step 104, the differential value calculation unit 42a always calculates the differential value. The differential value is a value obtained by time-differentiating the value of the voltage or current applied to the semiconductor device 11 by the evaluation unit 32a. Since V _CE (sat) is evaluated here, the differential value is calculated from the value of the voltage applied to the semiconductor device 11. Whether to calculate the differential value from the value of the voltage applied to the semiconductor device 11 or to calculate the differential value from the value of the current applied to the semiconductor device 11 is appropriately determined for each evaluation item.

When the differential value is calculated, the first comparison unit 42b immediately compares the differential value with a predetermined threshold value (step 106). The first comparison unit 42b grasps (reads) from the evaluation unit 32a that the evaluation item under evaluation is V _CE (sat), and then evaluates V _CE (sat) among the threshold values stored in the storage unit 44. Use the threshold for. This threshold is a threshold used in the process of increasing the voltage of the semiconductor device in the V _CE (sat) evaluation.

  If the first comparison unit 42b determines that the differential value exceeds the threshold value, the first comparison unit 42b issues a discharge notification signal to the control unit 32b. The control unit 32b that has received the discharge notification signal stops the evaluation by the evaluation unit 32a (step 108). At this time, the storage unit 44 stores information that identifies the semiconductor device 11 that has been discharged. This information is, for example, the ID of the semiconductor device 11. Later, based on this information, the semiconductor device in which discharge has occurred is discarded.

  FIG. 6 is a diagram illustrating an example of the transition of the differential value. Area A and area B in FIG. 6 correspond to area A and area B in FIG. The threshold value is set so that the differential value exceeds the threshold value for both temporary discharge and continuous discharge.

  On the other hand, when there is no discharge and the differential value does not exceed the threshold value, the discharge detection unit 42 determines whether or not the boosting of the semiconductor device is finished (step 110). When the boosting is not finished, the discharge detection is continued, and when the boosting is finished, the discharge detection is finished. As described above, according to the evaluation apparatus according to Embodiment 1 of the present invention, when the differential value exceeds the threshold value, it is considered that the discharge has occurred, and the evaluation by the evaluation unit 32a is stopped.

  Although the discharge in the process of increasing the voltage applied to the semiconductor device has been described here, the discharge can occur in the process of applying a constant voltage (steady process) and in the process of decreasing the voltage. It is desirable to perform detection. FIG. 7 is a diagram illustrating discharge in the process of decreasing the voltage applied to the semiconductor device. A temporary discharge is shown in the C region and a continuous discharge is shown in the D region. In the case where discharge is detected in the process of applying a constant voltage and the process of decreasing the voltage, threshold values corresponding to those processes are stored in the storage unit 44. In this case, a plurality of threshold values are stored for each evaluation item.

  According to the evaluation apparatus according to Embodiment 1 of the present invention, the differential value of the value of the voltage applied to the semiconductor device 11 is calculated by the differential value calculation unit 42a, and the differential value and the threshold value are compared by the first comparison unit 42b. Thus, the discharge can be easily detected. Therefore, it is possible to reliably capture the semiconductor device in which discharge has occurred. Further, the evaluation by the evaluation unit 32a is stopped by the control unit 32b immediately after the occurrence of the discharge, so that the contact probe 14 and the emitter electrode 11a can be prevented from being damaged and the damage range can be prevented from being expanded.

  Since the information specifying the semiconductor device that has been discharged is stored in the storage unit 44, it is possible to prevent the semiconductor device that has been discharged from being shipped. The first comparison unit 42b grasps the evaluation item under evaluation from the evaluation unit 32a, and then compares the threshold value corresponding to the evaluation item under evaluation among the threshold values stored in the storage unit 44 with the differential value. Therefore, it is possible to detect the presence or absence of discharge using an appropriate threshold value for each evaluation item.

  As is clear from FIG. 1, the connection portions 16 and 34 and the plurality of contact probes 14 are arranged so that the plurality of contact probes 14 are sandwiched between the connection portion 16 and the connection portion 34. Therefore, for each contact probe, the length of the path from the connection portion 16 via the contact probe to the connection portion 34 can be made substantially the same, so that the current densities of the contact probes can be made almost the same.

  The semiconductor device 11 to be evaluated is not limited to an IGBT having a vertical structure. For example, a lateral structure semiconductor device that inputs and outputs current on the upper surface may be an evaluation target. Further, the semiconductor device 11 may be a wafer on which a plurality of semiconductor chips are formed or a single semiconductor chip. In the case where a plurality of semiconductor chips are formed in the semiconductor device 11, “information specifying the semiconductor device 11 that has been discharged” stored in the storage unit 44 is, for example, coordinates of the position of the semiconductor device 11.

  The measuring instrument is not limited to the measuring instrument shown in FIG. 1 as long as it measures the electrical characteristics of the semiconductor device 11. For example, a cantilever contact probe may be employed. Further, the stretchability of the contact probe may be ensured by a laminated probe or a wire probe.

  The chuck stage 10 is not particularly limited as long as the semiconductor device 11 is fixed by vacuum chucking or electrostatic chucking of the semiconductor device 11. Further, instead of moving the probe card 18 by the arm 20, the chuck stage 10 may be moved. The modification shown in the first embodiment of the present invention can also be applied to an evaluation apparatus according to the following embodiment.

Embodiment 2. FIG.
Since the evaluation apparatus according to Embodiment 2 of the present invention has a lot in common with Embodiment 1, differences from Embodiment 1 will be mainly described. FIG. 8 is a diagram of an evaluation apparatus according to Embodiment 2 of the present invention. The discharge detection unit 200 includes a detection unit 200a and a second comparison unit 200b.

  The detection unit 200 a is a part that detects the value of the voltage or current applied to the semiconductor device 11. The second comparison unit 200b inspects whether the voltage or current has reached the “predetermined value” within the “predetermined time” in the process of increasing or decreasing the voltage or current applied to the semiconductor device. Part. That is, the second comparison unit 200b determines whether the voltage or current does not reach the predetermined first set value even when the predetermined first set time is exceeded in the process of increasing the voltage or current, or the voltage or current When the voltage or current does not reach the predetermined second set value even if the predetermined second set time is exceeded in the process of lowering the voltage, a discharge notification signal is issued to the control unit 32b.

  The storage unit 202 stores a first set time, a first set value, a second set time, and a second set value for each evaluation item. The second comparison unit 200b grasps the evaluation item under evaluation from the evaluation unit 32a, and stores the first set time, the first set value, the second set time, and the second set value corresponding to the evaluation item under evaluation. The above inspection (discharge detection) is performed by extracting from the unit 202.

  FIG. 9 is a diagram illustrating a waveform when the voltage does not reach the first set value even when the first set time is exceeded in the process of increasing the voltage. In FIG. 9, tp represents the first set time. Vp represents the first set value. In this case, it is assumed that the voltage is boosted to the first set value Vp within the range of the first set time tp. FIG. 9 shows that the voltage could not be boosted to the first set value Vp within the first set time tp because of the continuous discharge shown in the E region. Since the first set value Vp could not be reached within the first set time tp, the second comparison unit 200b issues a discharge notification signal to the control unit 32b. And the control part 32b stops evaluation by the evaluation part 32a.

  The process of decreasing the voltage is the same as the process of increasing the voltage, and thus the description thereof is omitted. Depending on the evaluation item, the discharge can be detected by replacing the voltage with a current. According to the evaluation apparatus according to the second embodiment of the present invention, it is possible to reliably capture the discharge when the voltage or current increases or the voltage or current decreases.

  By the way, the memory | storage part 44 and the discharge detection part 42 which concern on Embodiment 1 may be added to the evaluation apparatus which concerns on Embodiment 2 of this invention. FIG. 10 is a diagram of an evaluation apparatus that uses both the discharge detection unit according to the first embodiment of the present invention and the discharge detection unit according to the second embodiment. According to this evaluation apparatus, even if any one of the discharge detection units has a problem, the other discharge detection unit can reliably capture the discharge.

  According to the present invention, a discharge detection unit detects a voltage or current applied to a semiconductor device during evaluation of the semiconductor device, and detects occurrence of discharge from a change in voltage or current. Various modifications are possible as long as this characteristic is not lost.

  10 chuck stage, 11 semiconductor device, 11a emitter electrode, 11b collector electrode, 12 insulating base, 14 contact probe, 16 connection part, 18 probe card, 20 arm, 30 signal line, 32 controller, 32a evaluation part, 32b control part, 34 connection unit, 36 signal line, 42 discharge detection unit, 42a differential value calculation unit, 42b first comparison unit, 44,202 storage unit, 200 discharge detection unit, 200a detection unit, 200b second comparison unit

Claims (2)

  An evaluation unit that applies voltage and current to the semiconductor device and evaluates electrical characteristics of the semiconductor device;
  A discharge detector for detecting a voltage or current applied to the semiconductor device and generating a discharge notification signal when the occurrence of discharge is detected from a change in the voltage or current;
  A control unit that stops the evaluation by the evaluation unit when the discharge notification signal is received from the discharge detection unit;
  A storage unit that stores information for identifying the semiconductor device that has been discharged, and
  The discharge detector is
  A detector for detecting the voltage or current;
  When the voltage or current does not reach a predetermined first set value even if a predetermined first set time is exceeded in the process of increasing the voltage or current, or in the process of decreasing the voltage or current A second comparison unit that issues the discharge notification signal to the control unit when the voltage or current does not reach a predetermined second set value even after a predetermined second set time. An evaluation apparatus characterized by.   The storage unit stores the first set time, the first set value, the second set time, and the second set value for each evaluation item,
  The second comparison unit grasps an evaluation item under evaluation from the evaluation unit, and the first set time, the first set value, the second set time, and the first corresponding to the evaluation item under evaluation 2. The evaluation apparatus according to claim 1, wherein two set values are extracted from the storage unit and used.

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