JP2012129252A - Semiconductor integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor integrated circuit which can separate a voltage limit circuit from an output element in an inspection before product shipment without providing a special switching element.SOLUTION: In an output element 10 that is an active element, a drain is connected to a first pad 31, a source is connected to a third pad 33 and a gate is connected to an output element drive circuit 11. A voltage limit circuit 20 has a structure in which two Zener diodes 21 and 22 are connected in series in a reverse bias direction and limits a voltage applied to the second pad 32 to a predetermined clamp voltage. The drain of the output element 10 and a cathode of the voltage limit circuit 20 which are to be electrically connected in normal operation as described above are separated by two pads 31 and 32 in a wafer state of a semiconductor integrated circuit 1.

Description

  The present invention relates to a semiconductor integrated circuit, and more particularly to a semiconductor integrated circuit in which an output element having a voltage limiting circuit for protecting the element from an overvoltage such as a surge is integrated.

  As is well known, a voltage limiting circuit is often used as a circuit for protecting an output element such as a MOSFET (metal oxide semiconductor field effect transistor) from an overvoltage such as a surge. This voltage limiting circuit is composed of a circuit 120 in which two Zener diodes are connected in series as in the conventional semiconductor integrated circuit 101 shown in FIG. 7, for example, and is reverse-biased between the gate and drain of the MOSFET that is the output element 110. Is inserted in such a direction (reverse bias direction). In the voltage limiting circuit 120 having this configuration, when an overvoltage such as a surge is applied between the gate and the drain of the output element 110, the Zener diode passes a current to limit (clamp) the overvoltage to a predetermined clamp voltage. The output element 110 is protected.

  In the semiconductor integrated circuit 101 in which the output element 110 having the voltage limiting circuit 120 is integrated, a leak test, a withstand voltage test, and the like of the output element 110 are performed in a pre-shipment inspection. In these tests, for example, a test voltage is forcibly applied from the outside between the source and drain of the MOSFET that is the output element 110, that is, between the pad 131 and the pad 133 formed on the wafer, and the output element 110 leaks. Measurements such as current and withstand voltage are performed.

  However, in the conventional semiconductor integrated circuit 101 in which the output element 110 having the voltage limiting circuit 120 is integrated, the voltage limiting circuit 120 is always electrically connected to the output element 110 (see FIG. 7). For this reason, no matter how high the test voltage is applied to the output element 110 (between the pad 131 and the pad 133), the voltage limiting circuit 120 operates and the high test voltage is limited to a predetermined clamp voltage, There is a problem that the original characteristic of the output element 110 cannot be measured accurately.

As a technique for solving this problem, there is a semiconductor integrated circuit described in Patent Document 1, for example. In the conventional semiconductor integrated circuit described in Patent Document 1, a MOSFET that is a switching element is inserted in series with respect to a voltage limiting circuit that is inserted between the gate and drain of a power MOSFET that is an output element.
With this configuration, in the conventional semiconductor integrated circuit described in Patent Document 1, when the output element is inspected before product shipment, the switching element is turned off to disconnect the voltage limiting circuit from the output element, and the output element alone The characteristics are accurately measured, and during normal use after product shipment, the switching element is always turned on, and the voltage limiting circuit is connected to the output element to protect the output element from overvoltage such as surge.

JP-A-11-261064

However, in the conventional semiconductor integrated circuit described in Patent Document 1, a switching element such as a MOSFET is used to separate the voltage limiting circuit from the output element so that the voltage limiting circuit does not function in a pre-product inspection. In addition, in order to switch between the on operation and the off operation of the MOSFET, it is necessary to apply a control voltage from the outside to the gate of the MOSFET.
That is, in the conventional semiconductor integrated circuit described in Patent Document 1, a dedicated MOSFET is purposely provided as a switching element only for inspection before product shipment, or an external circuit or terminal for supplying a control voltage to the gate of this MOSFET It is necessary to secure the semiconductor chip, and problems remain in terms of the cost and size of the semiconductor chip.

  Therefore, an object of the present invention is to provide a semiconductor integrated circuit in which an output element having a voltage limiting circuit is integrated, without providing a dedicated switching element, and to disconnect the voltage limiting circuit from the output element during pre-shipment inspection. It is to provide a possible semiconductor integrated circuit.

The present invention is directed to a semiconductor integrated circuit in which semiconductor elements are integrated. In order to achieve the above object, the semiconductor integrated circuit according to the present invention includes an output element that is an active element and a voltage limit that limits the overvoltage to a predetermined voltage when an overvoltage exceeding a predetermined voltage is applied to the output element. Integrated with the circuit. Further, in the semiconductor integrated circuit of the present invention, the first pad for supplying a voltage to the output element and the first pad are provided independently, and the first pad is electrically connected to the first pad by wire bonding. And a second pad for supplying a voltage to the voltage limiting circuit, which can be connected to each other.
With this configuration, the voltage limiting circuit can be electrically disconnected from the output element at the time of inspection before product shipment without providing a dedicated switching element.

  Typically, the output element is an N-channel type MOSFET. The voltage limiting circuit is at least one Zener diode provided in the reverse bias direction between the second pad and the gate of the MOSFET.

Note that it is desirable to further integrate a detection circuit that can detect whether or not the voltage limiting circuit is operating in a state where the first pad and the second pad are electrically connected. The specific detection circuit determines whether or not a current flows through at least one Zener diode until a predetermined period elapses after the output element shifts from an on operation to an off operation. It detects whether the circuit is operating.
With this detection circuit, it is possible to determine more than the voltage limiting circuit due to the disconnection of the bonding wire or the like even after the product is shipped.

Generally, the above-described semiconductor integrated circuit is mounted on a semiconductor package having a plurality of input / output terminals and commercialized. In mounting on this semiconductor package, in the present invention, a wire bonded to the first pad of the semiconductor integrated circuit and a wire bonded to the second pad are any one of a plurality of input / output terminals. Connect to.
By this packaging, the output element and the voltage limiting circuit are electrically connected, and the output element can be protected by the voltage limiting circuit.

  According to the present invention, the output element can be inspected before product shipment without being affected by the voltage restriction by the voltage restriction circuit in a state where the voltage restriction circuit is electrically disconnected from the output element. Accordingly, the ability to detect a defect in the output element in the manufacturing process is enhanced, and the quality of the shipped product is improved.

1 is a diagram illustrating a configuration of a semiconductor integrated circuit 1 according to a first embodiment of the present invention. The figure explaining the state which mounted the semiconductor integrated circuit 1 shown in FIG. The figure explaining an example of the inspection before product shipment performed with respect to the semiconductor integrated circuit 1 shown in FIG. The figure explaining the state which mounted the semiconductor integrated circuit 2 which concerns on the 2nd Embodiment of this invention in the semiconductor package 60. The figure which shows the relationship between the voltage which appears in the input-output terminal 71, and the electric current I which flows into the shunt resistance 41 The figure explaining the structure of the other semiconductor integrated circuit 3 of this invention. 2A and 2B illustrate a configuration of a conventional semiconductor integrated circuit 101. FIG.

Hereinafter, each embodiment of the present invention will be described with reference to the drawings.
<First Embodiment>
FIG. 1 is a diagram illustrating the configuration of a semiconductor integrated circuit 1 according to the first embodiment of the present invention. FIG. 2 is a diagram for explaining a state in which the semiconductor integrated circuit 1 shown in FIG. A semiconductor integrated circuit 1 shown in FIG. 1 shows a state of a wafer on which semiconductor elements, wirings, and the like are formed. In the present invention, the semiconductor integrated circuit 1 is subjected to a pre-shipment inspection such as a leak test and a withstand voltage test, and then the semiconductor integrated circuit 1 that has passed the inspection is mounted on the semiconductor package 60 and shipped. .

First, the semiconductor integrated circuit 1 according to the first embodiment of the present invention will be described.
In FIG. 1, the semiconductor integrated circuit 1 includes an output element 10, a voltage limiting circuit 20, first to third pads 31 to 33, an output element driving circuit 11, a Zener diode 12, and a resistor 13. .

  The output element 10 is an active element that outputs a predetermined signal with respect to an input signal. In the present invention, an N-channel MOSFET is used. As this MOSFET, for example, a double diffusion MOSFET (DMOSFET) or a lateral double diffusion MOSFET (LDMOSFET) is used. In addition to the MOSFET, the output element 10 may be, for example, a lateral insulated gate bipolar transistor (LIGBT) or a general bipolar transistor (BT). When this bipolar transistor is applied, the gate, drain, and source described in the following embodiment may be interpreted as the base, collector, and emitter, respectively.

  The output element 10 has a drain connected to the first pad 31, a source connected to the third pad 33, and a gate connected to the output element drive circuit 11. The voltage limiting circuit 20 is a circuit that limits (clamps) the voltage applied to the second pad 32 to a predetermined clamp voltage. Typically, at least one Zener diode that can easily obtain a constant voltage is used in the voltage limiting circuit 20. For example, a configuration in which two Zener diodes 21 and 22 are connected in series, an anode is connected to the gate of the output element 10 and a cathode is connected to the second pad 32 (a configuration in which the reverse bias direction is connected) is connected to the voltage limiting circuit 20. To do. In this way, the drain of the output element 10 to be electrically connected during normal operation and the cathode of the voltage limiting circuit 20 are separated by the two pads 31 and 32 in the wafer state of the semiconductor integrated circuit 1. The output element drive circuit 11 supplies a drive signal to the gate of the output element 10 to control the on operation and the off operation of the output element 10.

  The Zener diode 12 has a cathode connected to the gate of the output element 10 (in the reverse bias direction), and is inserted between the third pad 33 and the gate of the output element 10. The Zener diode 12 is a protective element that prevents an excessive voltage from being applied to the gate of the output element 10. The resistor 13 is also inserted between the third pad 33 and the gate of the output element 10. The resistor 13 generates a potential necessary for an on operation or an off operation at the gate of the output element 10 in accordance with a drive signal output from the output element drive circuit 11. Note that the zener diode 12 and the resistor 13 are not particularly indispensable when realizing the voltage limiting circuit 20 provided by the present invention to be disconnected from the output element 10.

Next, pre-product inspection performed on the semiconductor integrated circuit 1 having the above-described configuration will be described. FIG. 3 is a diagram for explaining an example of a pre-shipment inspection performed on the semiconductor integrated circuit 1 shown in FIG.
As shown in FIG. 3, when performing a leak test on the output element 10, a test voltage source 81 is connected between the first pad 31 and the third pad 33, and between the drain and source of the output element 10. Only the test voltage is applied. Whether or not a leak current flows through the output element 10 is determined using an ammeter 82 inserted in series with the test voltage source 81.

  In this leak test, since the test voltage is not applied to the second pad 32, the voltage limiting circuit 20 can be electrically disconnected from the output element 10. Therefore, a test voltage exceeding the clamp voltage limited by the voltage limiting circuit 20 can be applied to the output element 10. As a result, the ability to detect defects (screening ability) of the semiconductor integrated circuit 1, that is, the output element 10, can be enhanced as compared with the conventional case, so that the product quality can be further improved.

Even when other pre-shipment inspections such as a withstand voltage test are performed on the output element 10, necessary test voltage sources are respectively provided between the first pad 31 and the third pad 33 as shown in FIG. 3. Just connect.
Further, by applying a test voltage or a test signal between the second pad 32 and the third pad 33, the operation test of the voltage limiting circuit 20 can be performed independently.

The semiconductor integrated circuit 1 that has passed the pre-shipment inspection is mounted on a semiconductor package 60 having a plurality of input / output terminals as shown in FIG.
In FIG. 2, the semiconductor integrated circuit 1 is fixed to a semiconductor package 60, and each pad and an input / output terminal of the semiconductor package 60 are bonded with a metal wire. At this time, the first pad 31 and the second pad 32 are bonded to the same input / output terminal 71 by the first wire 61 and the second wire 62, respectively. Thereby, in the packaged product to be shipped, the drain of the output element 10 and the cathode of the voltage limiting circuit 20 are connected. FIG. 2 shows an example in which the input / output terminal 71 is applied to the power supply voltage Vcc via the inductor 70. On the other hand, the third pad 33 is bonded to the input / output terminal 73 by the third wire 63.

As described above, according to the semiconductor integrated circuit 1 according to the first embodiment of the present invention, the drain of the output element 10 and the cathode of the voltage limiting circuit 20 are connected to different pads 31 and 32, respectively. Disconnect. In the semiconductor package 60 that is a shipped product, different pads 31 and 32 of the semiconductor integrated circuit 1 are wire-bonded to one input / output terminal 71.
Thereby, in the wafer state, the output element 10 can be inspected before shipping without being affected by the clamp voltage by the voltage limiting circuit 20. Accordingly, the ability to detect a defect in the output element 10 in the manufacturing process is enhanced, and the quality of the shipped product is improved. In particular, the output element 10 tends to have a larger element size as the required withstand voltage is higher, increase the possibility of contamination by foreign matters in the manufacturing process, and increase the element defect rate. Therefore, the configuration of the semiconductor integrated circuit 1 according to the present invention is extremely effective when applied to a circuit including the high breakdown voltage output element 10.

In addition, according to the semiconductor integrated circuit 1 according to the first embodiment, a dedicated switching element for separating the voltage limiting circuit 20 from the output element 10 as in the conventional semiconductor integrated circuit described in Patent Document 1 above. It is not necessary to use a signal and to supply a signal for controlling the switching element.
This eliminates the need to provide a dedicated circuit for supplying a control signal to the switching element or an input / output terminal of the semiconductor package, thereby reducing the scale of the semiconductor integrated circuit 1 and reducing the cost of the semiconductor integrated circuit 1. Can do.

Furthermore, according to the semiconductor integrated circuit 1 according to the first embodiment, the pre-product inspection of the output element 10 and the pre-product inspection of the voltage limiting circuit 20 can be independently performed.
Thereby, when a defect occurs in the semiconductor integrated circuit 1, it is possible to clearly determine whether the output element 10 is defective or the voltage limiting circuit 20 is defective from the result of the inspection before each product shipment. .

<Second Embodiment>
In the semiconductor integrated circuit 1 according to the first embodiment, since the pads 31 and 32 are respectively provided in the output element 10 and the voltage limiting circuit 20 in the wafer state, the two bonding wires 61 and 62 are in the package state. It is necessary to electrically connect the voltage limiting circuit 20 to the output element 10 via
However, since the electrical connection between the voltage limiting circuit 20 and the output element 10 is performed via the two bonding wires 61 and 62, the semiconductor integrated circuit 1 according to the first embodiment has the following new features. Problems arise.

  For example, when the first wire 61 bonded to the first pad 31 is disconnected after the product is shipped, the voltage of the input / output terminal 71 sticks to a high level regardless of the operating state of the output element 10. Since there is no change, the abnormality of the first wire 61 can be detected. However, when only the second wire 62 bonded to the second pad 32 is disconnected, during normal operation where no overvoltage is applied, a normal voltage that is normal according to the operating state of the output element 10 is obtained. Only appears at the input / output terminal 71, and no special voltage change occurs. That is, in the packaged state, even if the voltage appearing at the input / output terminal 71 is observed, the abnormality of the second wire 62 cannot be detected.

  Therefore, in the second embodiment, a semiconductor integrated circuit will be described that further includes a disconnection detection circuit that can accurately detect abnormality of the second wire 62 due to disconnection or the like even in a package state.

  FIG. 4 is a diagram for explaining a state in which the semiconductor integrated circuit 2 according to the second embodiment of the present invention is mounted on the semiconductor package 60. The semiconductor integrated circuit 2 according to the second embodiment has a configuration in which a disconnection detection circuit 40 is further added to the semiconductor integrated circuit 1 according to the first embodiment described above. The other configuration of the semiconductor integrated circuit 2 is the same as that of the semiconductor integrated circuit 1, and therefore, the same reference numerals are given and a part of the description is omitted.

  The disconnection detection circuit 40 includes a shunt resistor 41, a comparator 42, and a disconnection determination unit 43. The shunt resistor 41 is inserted between the anode of the voltage limiting circuit 20 and the gate of the output element 10. The comparator 42 inputs and compares voltages appearing at both terminals of the shunt resistor 41, and detects the presence or absence of a voltage difference between the terminals caused by a voltage drop when a current flows through the shunt resistor 41. The disconnection determination unit 43 receives, from the comparator 42, the presence / absence of a voltage difference between the terminals of the shunt resistor 41 and the driving signal for controlling the on / off operation of the output element 10 from the output element driving circuit 11, respectively. The disconnection of the second wire 62 bonded to 32 is determined as follows.

First, when the second wire 62 is connected, a low voltage appears at the input / output terminal 71 when the output element 10 is turned on by a high-level drive signal. Thereafter, when the output element 10 shifts to an off operation by a low level drive signal, the current of the inductor 70 is held and the input / output terminal 71 is lifted, whereby the voltage limiting circuit 20 operates to become a clamp voltage, and the shunt resistance A current I flows through 41. The clamp voltage is gradually lowered after being held for the period X.
FIG. 5A shows the relationship between the voltage appearing at the input / output terminal 71 and the current I flowing through the shunt resistor 41 when the second wire 62 is connected.

On the other hand, when the second wire 62 is disconnected, a low voltage appears at the input / output terminal 71 as usual when the output element 10 is turned on by a high-level drive signal. However, after that, even if the output element 10 shifts to the off operation by the low level drive signal, the voltage limiting circuit 20 does not operate and the input / output terminal 71 cannot be raised to the clamp voltage. Therefore, the current I does not flow through the shunt resistor 41.
FIG. 5B shows the relationship between the voltage appearing at the input / output terminal 71 and the current I flowing through the shunt resistor 41 when the second wire 62 is disconnected.

  Using these different states, the disconnection determination unit 43 causes the output element 10 to switch from the on operation (drive signal is high level) to the off operation (drive signal is low level) until the period X elapses. If there is a voltage difference between the terminals of the shunt resistor 41, it is determined that the second wire 62 is not disconnected. On the other hand, if there is no voltage difference between the terminals of the shunt resistor 41, it is determined that the second wire 62 is disconnected. To do.

As described above, according to the semiconductor integrated circuit 2 according to the second embodiment of the present invention, the disconnection detection circuit 40 is further included in the configuration of the semiconductor integrated circuit 1 according to the first embodiment described above. Even after shipment, the disconnection of the second wire 62 can be determined.
Thereby, in addition to the effect of the first embodiment, it is possible to appropriately check whether or not the second wire 62 is disconnected each time the output element 10 shifts from the on operation to the off operation. The disconnection determination unit 43 notifies the abnormal state by outputting the obtained result (for example, diagnosis) to a system or the like incorporating the semiconductor integrated circuit 2. By this notification, it is possible to avoid a situation in which the voltage limiting circuit 20 does not function when an overvoltage actually occurs by continuing to use the semiconductor integrated circuit 2 even though there is an abnormality in the wire breakage.

  In the first and second embodiments, the configuration in which the voltage limiting circuit 20 is electrically disconnected from the output element 10 in the wafer state has been described. However, the configuration in which the voltage limiting circuit 20 is electrically disconnected from the output element 10 is only the voltage limiting circuit 20. Not limited to. For example, as in the semiconductor integrated circuit 3 shown in FIG. 6, the voltage source of another circuit (voltage monitor circuit 50 or the like) inserted in parallel with the output element 10 is connected to the second pad 32 that is the same as the voltage limiting circuit 20. By connecting, another circuit can be electrically disconnected from the output element 10. Thereby, the original characteristic of the output element 110 can be measured more reliably.

  The configuration of the semiconductor integrated circuit of the present invention can be used for an output element having a voltage limiting circuit. In particular, the voltage limiting circuit is electrically connected to the output element at the time of inspection before product shipment without providing a dedicated switching element. Suitable when you want to separate.

1-3, 101 Semiconductor integrated circuit 10, 110 Output element 11 Output element drive circuit 12, 21, 22 Zener diode 13, 41 Resistor 20, 120 Voltage limiting circuit 31-33, 131, 133 Pad 40 Disconnection detection circuit 42 Comparator 43 Disconnection determination unit 50 Voltage monitor circuit 60 Semiconductor package 61-63 Wire 70 Inductor 71, 73 Input / output terminal 81 Test voltage source 82 Ammeter

Claims (5)

A semiconductor integrated circuit in which semiconductor elements are integrated,
An output element that is an active element;
When an overvoltage exceeding a predetermined voltage is applied to the output element, a voltage limiting circuit that limits the overvoltage to the predetermined voltage is integrated,
A first pad for supplying a voltage to the output element;
A second pad for supplying a voltage to the voltage limiting circuit, which is provided independently of the first pad and can be electrically connected to the first pad by wire bonding, is formed. A semiconductor integrated circuit. The output element is an N-channel MOSFET,
The semiconductor integrated circuit according to claim 1, wherein the voltage limiting circuit is at least one Zener diode provided in a reverse bias direction between the second pad and the gate of the MOSFET.   The detection circuit according to claim 2, further comprising a detection circuit that detects whether or not the voltage limiting circuit is operating in a state in which the first pad and the second pad are electrically connected. Semiconductor integrated circuit.   4. The detection circuit according to claim 3, wherein the detection circuit determines whether or not a current flows through the at least one Zener diode until a predetermined period elapses after the output element shifts from the on operation to the off operation. The semiconductor integrated circuit as described. A semiconductor package having a plurality of input / output terminals,
The semiconductor integrated circuit according to claim 1 is mounted,
A wire bonded to the first pad of the mounted semiconductor integrated circuit and a wire bonded to the second pad of the semiconductor integrated circuit are set to any one of the plurality of input / output terminals. Connected semiconductor package.

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