Semiconductor device

This application is a National Stage of International Application No. PCT/JP2015/067055, filed Jun. 12, 2015, claiming priority based on Japanese Patent Application No. 2014-127418, filed Jun. 20, 2014, the contents of all of which are incorporated herein by reference in their entirety.

The present invention relates to a semiconductor device with improved resistance to ESD noise.

In a semiconductor device which operates in an environment in which “electrostatic discharge” (ESD) occurs, it is preferable for an influence of ESD noise to be reduced. This is because element destruction or a malfunction occurs when ESD noise or the like is input to an analog circuit or the like. Therefore, several schemes have been conventionally proposed (see, for example, Patent Literature 1).

Patent Literature

Patent Literature 1: Japanese Patent No. 4978998

Technical Problem

However, in a case where a first circuit and a second circuit having different functions are connected in series, inventive ideas for reducing an influence of ESD noise or the like are not known.

The present invention has been made in view of such problems, and an object thereof is to provide a semiconductor device capable of reducing an influence of ESD noise or the like.

Solution to Problem

In order to solve the above-described problems, a first semiconductor device is a semiconductor device including a plurality of leads, the semiconductor device including: a first circuit and a second circuit that are connected in series; a first terminal that applies a first potential to a first power supply line of the first circuit; a second terminal that applies a second potential to a second power supply line of the second circuit; a third terminal that is connected to a signal transfer line of the first circuit; and a first protection circuit that is connected to the third terminal, and discharges a current from the third terminal to a fourth terminal when a potential of the third terminal becomes higher than a first threshold value, wherein the first power supply line and the second power supply line are separated, and the fourth terminal is not directly connected to the first power supply line and is electrically connected to a lead.

Since the first power supply line of the first circuit and the second power supply line of the second circuit are separated from each other, an influence of a fluctuation in a potential of one of the power supply lines on the other is originally small, and a stable circuit operation is performed. On the other hand, when ESD noise or the like is generated and a potential of the third terminal greatly rises, a current flows from the first protection circuit to the fourth terminal. Thus, the first circuit is protected. However, when the fourth terminal is directly connected to the first power supply line, a power supply potential of the first power supply line fluctuates, the first circuit malfunctions, and a malfunction occurs in transmission and reception between the first circuit and the second circuit. Therefore, in this semiconductor device, the fourth terminal is not directly connected to the first power supply line and is connected to the lead. Accordingly; ESD noise output from the fourth terminal at the time of the operation of the first protection circuit does not directly flow into the first circuit via the first power supply line. Thus, a malfunction of the first circuit or a malfunction of transmission and reception between the first circuit and the second circuit are suppressed.

Further, a second semiconductor device includes a first lead connected to the first terminal via a first wiring; a fourth wiring connected to the fourth terminal; and a first shield wiring located between the first wiring and the fourth wiring.

Since the first wiring is connected to the first power supply line, the potential of the first power supply line fluctuates if ESD noise is superimposed on the first wiring, and if the fourth wiring is adjacent to the first wiring, noise is easily superimposed on the first wiring. This is because a large noise current flows from the first protection circuit to the fourth wiring when ESD noise is input. In such a case, since the first shield wiring is disposed between the first wiring and the fourth. wiring, it is possible to block electromagnetic waves traveling through a space from the fourth wiring to the first wiring. Therefore, it is possible to suppress a fluctuation in the potential of the first power supply line.

The above-described circuit configuration can be applied not only to the power supply line but also to a fixed line to which a fixed potential is applied, such as a ground line. If the circuit configuration is applied to both, it is possible to perform the above-described suppression of the malfunction more effectively.

That is, a third semiconductor device includes a fifth terminal that applies a first fixed potential to a first fixed line of the first circuit; a sixth terminal that applies a second fixed potential to a second fixed line of the second circuit; and a second protection circuit that is coupled to the third terminal and flows a current from the seventh terminal to the third terminal when a potential of the third terminal becomes lower than a second threshold value, wherein the first fixed line and the second fixed line are separated, and the seventh terminal is electrically connected to a lead without going through the first fixed line.

Since the first fixed line of the first circuit and the second fixed line of the second circuit are separated from each other, an influence of a fluctuation in a potential in one of the fixed lines on the other is originally small, and a stable circuit operation is performed. On the other hand, when ESD noise or the like is generated and the potential of the third terminal greatly drops, a current flows from the second protection circuit to the seventh terminal. Thus, the first circuit is protected. However, when the seventh terminal is directly connected to the first fixed line, the potential of the first fixed line fluctuates, the first circuit malfunctions, and a malfunction occurs in transmission and reception between the first circuit and the second circuit. Therefore, in this semiconductor device, the seventh terminal is not directly connected to the first fixed line and is connected to the lead. Accordingly, ESD noise output from the seventh terminal at the time of the operation of the second protection circuit does not directly flow into the first circuit via the first fixed line. Thus, a malfunction of the first circuit or a malfunction of transmission and reception between the first circuit and the second circuit are suppressed.

A fourth semiconductor device includes a fifth lead connected to the fifth terminal via a fifth wiring; a seventh wiring connected to the seventh terminal; and a second shield wiring located between the fifth wiring and the seventh wiring.

Since the fifth wiring is connected to the first fixed line, if ESD noise is superimposed on the fifth wiring, a potential of the first fixed line fluctuates, and if the seventh wiring is adjacent to the fifth wiring, noise is easily superimposed on the seventh wiring. This is because a large noise current flows from the second protection circuit to the seventh wiring when the ESD noise is input. In such a case, if the second shield wiring is arranged between the fifth wiring and the seventh wiring, it is possible to block electromagnetic waves traveling through a space from the seventh wiring to the fifth wiring and to suppress a fluctuation in the potential of the first fixed line.

Further, a fifth semiconductor device further includes a third protection circuit including a pair of diodes connected in parallel with reversed polarities, wherein the third protection circuit is interposed between the first power supply line and the fourth terminal.

Further, a sixth semiconductor device further includes a fourth protection circuit including a pair of diodes connected in parallel with reversed polarities, wherein the fourth protection circuit is interposed between the first fixed line and the seventh terminal.

The third protection circuit and/or the fourth protection circuit can consume an output current of the protection circuit when ESD noise is input to the third terminal at the time of manufacture of the semiconductor device. Therefore, ESD noise does not flow in the first circuit, and the first circuit is protected.

According to the semiconductor device of the present invention, it is possible to reduce the influence of ESD noise or the like.

FIG. 1 is a plan view of a semiconductor device.

FIG. 2 is a bottom view of the semiconductor device.

FIG. 3 is a diagram illustrating a cross-sectional configuration of a semiconductor device.

FIG. 4 is a circuit diagram illustrating an example of a first circuit.

FIG. 5 is a circuit diagram illustrating an example of a second circuit.

FIG. 6 is a plan view of a semiconductor device.

FIG. 7 is a plan view of a semiconductor device according to a comparative example.

FIG. 8 is a diagram illustrating an input-side configuration of the semiconductor device in a case where a differential input is input.

FIG. 9 is a circuit diagram of a second (or third) protection circuit.

Hereinafter, a semiconductor device according to an embodiment will be described. The same reference numerals are used for the same elements and repeated description will be omitted.

FIG. 1 is a plan view of a semiconductor device.

This semiconductor device includes a semiconductor chip 10 , a die pad 11 to which the semiconductor chip 10 is fixed, a plurality of leads (ten in FIG. 1 ) arranged to be spaced around the die pad 11 , and a package 12 in which the die pad 11 and the leads are molded. In FIG. 1 , a resin mold located on the lead is excluded so that an internal connection relationship is seen.

FIG. 2 is a bottom view of the semiconductor device. Since a back surface of the rectangular die pad 11 and a back surface of each lead are exposed in a back surface of the package 12 , radiation of heat can be performed through the die pad 11 and the leads.

FIG. 3 is a diagram illustrating a cross-sectional configuration of the semiconductor device. A semiconductor device body including the semiconductor chip 10 , the die pad 11 , the package 12 , and the leads is fixed on a wiring circuit hoard 13 . The wiring circuit board 13 may be a multilayer wiring board. The semiconductor chip 10 and the various leads (an input lead INPUT and an output lead OUTPUT are illustrated in FIG. 3 ) are connected via a bonding wire (wiring). The semiconductor chip 10 is embedded inside the resin package 12 .

Referring back to FIG. 1 , a circuit configuration will be described.

This semiconductor device includes a plurality of leads, and various terminals are formed using electrode pads formed on a surface of the semiconductor chip 10 . A first circuit 1 and a second circuit 2 connected in series are formed in the semiconductor chip 10 , and a buffer circuit 3 is formed between the first circuit 1 and the second circuit 2 . A first protection circuit including a diode D 1 and a second protection circuit including a diode D 2 are provided on the input side of the first circuit 1 in the semiconductor chip 10 . The buffer circuit 3 is intended to reduce erroneous determination of signal transfer between the first circuit 1 and the second circuit 2 even when noise is large, and a Schmitt buffer may be used.

A first terminal T 1 , a second terminal T 2 , a third terminal T 3 , a fourth terminal T 4 , a fifth terminal T 5 , a sixth terminal T 6 , a seventh terminal T 7 , a first shield terminal TS 1 , a second shield terminal TS 2 , and a second circuit-side terminal T 10 are provided on the semiconductor chip 10 .

For convenience of description, the same reference numeral as those for the leads are used for voltages or signals applied to the leads. That is, potentials VCC 1 , VCC 2 , GND 1 , and GND 2 are assumed to be applied to the respective leads VCC 1 , VCC 2 , GND 1 , and GND 2 . Further, it is assumed that an input signal INPUT is applied to an input lead INPUT (third lead) and an output signal OUTPUT is taken out from an output lead OUTPUT.

The first terminal T 1 is connected to a first power supply line DL 1 of the first circuit 1 and applies the first potential (VCC 1 ) to the first power supply line DL 1 , and is connected to the first lead VCC 1 via the wiring W 1 . The second terminal T 2 is connected to the second power supply line DL 2 of the second circuit 2 and applies the second potential (VCC 2 ) to the second power supply line DL 2 , and is connected to the second lead VCC 2 via the wiring W 2 . The third terminal T 3 is connected to a signal transfer line of the first circuit 1 and is connected to the input lead INPUT via the wiring W 3 . The fourth terminal T 4 is connected to a cathode of the diode D 1 and is connected to the lead VCC 1 via the wiring W 4 . A resistance value of each wiring is greater than a resistance value of each lead.

The fifth terminal T 5 is connected to a first fixed line GL 1 of the first circuit 1 and supplies a first fixed potential (GND 1 : ground potential) to the first fixed line GL 1 , and is connected to the fifth lead GND 1 via a wiring W 5 . The sixth terminal T 6 is connected to a second fixed line GL 2 of the second circuit 2 and applies a second fixed potential (GND 2 : ground potential) to the second fixed line GL 2 , and is connected to the sixth lead GND 2 via a wiring W 6 . The seventh terminal T 7 is connected to an anode of the diode D 2 and is connected to the lead GND 1 via a wiring W 7 .

The first shield terminal TS 1 is connected to the die pad 11 fixed to the ground potential via a first shield wiring WS 1 . The second shield terminal TS 2 is connected to the die pad 11 fixed to the ground potential via a second shield wiring WS 2 .

The terminal T 10 on the side of the second circuit 2 is connected to the output lead OUTPUT via a wiring W 10 .

Here, if ESD noise is superimposed on the input lead INPUT, a potential at the third terminal T 3 greatly changes. The first protection circuit including the diode D 1 is connected to the third terminal T 3 , and when a potential of the third terminal T 3 becomes greater than a first threshold (a threshold voltage of the diode D 1 +a potential of the fourth terminal T 4 ), current is discharged from the third terminal T 3 to the fourth terminal T 4 . On the other hand, in the second protection circuit including the diode D 2 , when the potential of the third terminal T 3 becomes smaller than a second threshold value (a threshold of the diode D 2 +potential of the seventh terminal T 7 ), a current flows into the third terminal T 3 from the seventh terminal T 7 .

Therefore, the input side of the first circuit 1 is protected due to an operation of the first and second protection circuits.

The first power supply line DL 1 and the second power supply line DL 2 are separated from each other, and the fourth terminal T 4 is not directly connected to the first power supply line DL 1 , but is electrically connected to the lead VCC 1 . Further, the first fixed line GL 1 and the second fixed line GL 2 are separated, and the seventh terminal T 7 is electrically connected to the lead GND 1 without going through the first fixed line GL 1 .

Since the first power supply line DL 1 of the first circuit 1 and the second power supply line DL 2 of the second circuit 2 are separated from each other, an influence of a fluctuation in a potential of one of the power supply lines on the other is originally small, and a stable circuit operation is performed. On the other hand, when ESD noise or the like is generated and a potential of the third terminal T 3 greatly rises, a current flows from the protection circuit including the diode D 1 to the fourth terminal T 4 . Thus, the first circuit 1 is protected. However, when the fourth terminal T 4 is directly connected to the first power supply line DL 1 , a power supply potential of the first power supply line DL 1 fluctuates, the first circuit 1 malfunctions, and a malfunction occurs in transmission and reception between the first circuit 1 and the second circuit 2 .

That is, in the case of a circuit of a comparative example illustrated in FIG. 7 , when ESD noise is superimposed on the third terminal T 3 , ESD noise output from the diode D 1 causes the potential of the first power supply line DL 1 to fluctuate, and malfunctions are caused in the first circuit 1 .

In the semiconductor device of the embodiment in FIG. 1 , the fourth terminal T 4 is not directly connected to the first power supply line DL 1 and is connected to the lead VCC 1 without going through the first power supply line DL 1 . Therefore, ESD noise output from the fourth terminal T 4 at the time of the operation of the protection circuit does not directly flow into the first circuit 1 via the first power supply line DL 1 . Thus, a malfunction of the first circuit 1 and a malfunction of transmission and reception between the first circuit 1 and the second circuit 2 are suppressed.

The first shield wiring WS 1 is located between the first wiring W 1 and the fourth wiring W 4 . Since the first wiring W 1 is connected to the first power supply line DL 1 , the potential of the first power supply line DL 1 fluctuates if the ESD noise is superimposed on the first wiring W 1 , and if the fourth wiring W 4 is adjacent to the first wiring W 1 , noise is easily superimposed on the first wiring W 1 . This is because a large noise current flows from the first protection circuit to the fourth wiring W 4 when ESD noise is input. In this example, since the first shield wiring WS 1 is disposed between the first wiring W 1 and the fourth wiring W 4 , it is possible to block electromagnetic waves traveling through a space from the fourth wiring W 4 to the first wiring W 1 . Therefore, it is possible to suppress a fluctuation in the potential of the first power supply line DL 1 .

The above-described circuit configuration can be applied not only to the power supply line but also to a fixed line to which a fixed potential is applied, such as a ground line. If the circuit configuration is applied to both, it is possible to perform the above-described suppression of the malfunction more effectively.

Since the first fixed line GL 1 of the first circuit 1 and the second fixed line GL 2 of the second circuit 2 are separated from each other, an influence of a fluctuation in a potential in one of the fixed lines on the other is originally small, and a stable circuit operation is performed. On the other hand, when ESD noise or the like is generated and the potential of the third terminal T 3 greatly drops, a current flows from the second protection circuit including the diode D 2 to the seventh terminal T 7 . Thus, the first circuit 1 is protected. However, when the seventh terminal T 7 is directly connected to the first fixed line GL 1 , the potential of the first fixed line GL 1 fluctuates, the first circuit 1 malfunctions, and a malfunction occurs in transmission and reception between the first circuit 1 and the second circuit 2 .

In the semiconductor device of this example, the seventh terminal T 7 is not directly connected to the first fixed line GL 1 and is connected to the lead GND 1 without going through the first fixed line GL 1 . Therefore, since the ESD noise output from the seventh terminal T 7 at the time of the operation of the second protection circuit including the diode D 2 does not directly flow into the first circuit 1 via the first fixed line GL 1 , a malfunction of the first circuit 1 and a malfunction of transmission and reception between the first circuit 1 and the second circuit 2 are suppressed.

The second shield wiring WS 2 is located between the fifth wiring W 5 and the seventh wiring W 7 . Since the fifth wiring W 5 is connected to the first fixed line GL 1 , if the ESD noise is superimposed on the fifth wiring W 5 , a potential of the first fixed line GL 1 fluctuates, and if the seventh wiring W 7 is adjacent to the fifth wiring W 5 , noise is easily superimposed on the seventh wiring W 7 . This is because a large noise current flows from the second protection circuit including the diode D 2 to the seventh wiring W 7 when the ESD noise is input. In such a case, if the second shield wiring WS 2 is arranged between the fifth wiring W 5 and the seventh wiring W 7 , it is possible to block electromagnetic waves traveling through a space from the seventh wiring W 7 to the fifth wiring W 5 and to suppress a fluctuation in the potential of the first fixed line GL 1 .

The circuit configurations of the first circuit 1 and the second circuit 2 described above are not particularly limited, and the first circuit 1 may be an analog circuit and the second circuit 2 may be a digital circuit. An example of the first circuit 1 may include an amplifier or a PLL circuit. An example of the second circuit 2 may include a digital signal processing (DSP) circuit, an encoder (in the case of a transmission circuit), a decoder (in the case of a reception circuit), a scrambler, a descrambler, a packer, an unpacker, or an error detection circuit.

FIG. 4 is a circuit diagram illustrating an example of the first circuit.

Transistors Q 1 , Q 2 , Q 3 , and Q 4 are connected between the first power supply line DL 1 and the first fixed line GL 1 , as illustrated, to function as an amplifier that transfers a signal on an input side to an output side.

FIG. 5 is a circuit diagram illustrating an example of the second circuit.

A current mirror circuit is connected between the second power supply line DL 2 and the second fixed line GL 2 . That is, between the second power supply line DL 2 and the second fixed line GL 2 , a transistor Q 10 and a transistor Q 20 are connected in series and, in parallel therewith, a transistor Q 30 and a transistor Q 40 are connected in series. Gates of a pair of transistors Q 10 and Q 30 on the upstream side are connected in common, and are connected to an upstream position of the transistor Q 20 on the downstream side. An input signal is input to a gate of the transistor Q 20 , and a reference voltage Vref is input to a gate of the transistor Q 40 . A node on the downstream side of the transistor Q 20 and the transistor Q 40 is connected to the second fixed line GL 2 via a current source IS. According to a potential input to the gate of the transistor Q 20 , a potential of a node (a connection point between the transistor Q 30 and the transistor Q 40 ) on the output side fluctuates. This potential is output as an output signal to the outside.

FIG. 6 is a plan view of a semiconductor device.

The semiconductor device has a structure in which positions of the input lead INPUT and the output lead OUTPUT illustrated in FIG. 1 are mutually exchanged. In this case, a signal is input from the input lead INPUT, and a signal processed by the second circuit 2 is input to the first circuit 1 . For example, the second circuit 2 is a digital circuit, and the first circuit 1 is an analog circuit. When ESD noise is input to the third terminal T 3 via the output lead OUTPUT, the semiconductor device functions similarly to the above-described circuit.

FIG. 8 is a diagram illustrating a configuration of the input side of the semiconductor device when a differential input is received.

An input to the first circuit 1 described above may be a differential input. That is, two input units denoted by reference numeral 100 in FIG. 1 are included. Structures of the input unit 100 and the input unit 100 A in FIG. 8 are the same. Complementary signals are input to input terminals of the input units 100 and 100 A, and output signals from the input units 100 and 100 A are input to the first circuit 1 via the third terminal T 3 in FIG. 1 . In this case, the first circuit 1 has a modified structure as follows. That is, the first circuit 1 includes a pair of transistors QA and QB, and complementary input signals from the respective input units 100 and 100 A are input to gates of the respective transistors QA and QB. One-side terminals of the respective transistors QA and QB are connected to the first power supply line DL 1 via resistors RA and RB, and the other-side terminals thereof are connected to the first fixed line GL 1 via a switching transistor QC. An appropriate bias potential Bias can be applied to a gate of the transistor QC, and a current flows through the transistors QA and QB according to the voltage applied to the gates and the bias potential Bias. A node between the transistor QB and the resistor R 2 is connected to the second circuit 2 in the subsequent stage. In this structure, since a structure of the input unit for the transistors QA and QB is the same as that of the above-described circuit, the same effect as in the above embodiment is achieved and the input unit is protected.

FIG. 9 is a circuit diagram of the second (or third) protection circuit.

A protection circuit illustrated in FIG. 9 may be further provided between a node Pa of the first power supply line DL 1 or the first fixed line GL 1 illustrated in FIG. 1 and a node Pb on the first or second protection circuit side.

That is, in the third protection circuit, a pair of diodes D 10 and D 20 are connected in parallel with reversed polarities, and the third protection circuit is interposed between the first power supply line DL 1 and the fourth terminal T 4 .

In a fourth protection circuit, a pair of diodes D 10 and D 20 are connected in parallel with reversed polarities, and the fourth protection circuit is interposed between the first fixed line GL 1 and the seventh terminal T 7 . Any one of the third protection circuit and the fourth protection circuit may be provided or both may be provided. Further, as the diodes D 10 and D 20 , a bidirectional diode may be formed using a Zener diode. In the third protection circuit or the fourth protection circuit, a plurality of diodes may be connected in series in multiple stages to form a first diode group, diodes with opposite polarity may be connected in series in multiple stages to form a second diode group, and the diode groups may be connected in parallel.

According to the above-described configuration, the third protection circuit and/or the fourth protection circuit can consume an output current of the protection circuit when ESD noise is input to the third terminal at the time of manufacture of the semiconductor device. Therefore, ESD noise does not flow in the first circuit, and the first circuit is protected.

Specifically, in assembly of the device, in a step before the protection circuit (diodes D 1 and D 2 ) is bonded and connected to the leads VCC 1 and GND 1 via the wirings W 4 and W 7 , which is a step before the first circuit 1 is bonded and connected to the leads VCC 1 and GND 1 via the wirings W 1 and W 5 , there is no current path that connects the protection circuit (diodes D 1 and D 2 ) and the first circuit 1 via the first power supply line DL 1 or the first fixed line GL 1 . In this case, if ESD is input to the third terminal T 3 , which is an input terminal, the potential of the input terminal rises and the input unit of the protection circuit (diodes D 1 and D 2 ) may be destroyed since no current flows through the seventh terminal T 7 on the ground side or the fourth terminal on the power supply side. To suppress such destruction, the bidirectional diodes D 10 and D 20 as described above are provided between the node Pa and the node Pb on the power supply side and the ground side.

1 : First circuit

2 : Second circuit

DL 1 : First power supply line

DL 2 : Second power supply line

GL 1 : First fixed line

GL 2 : Second fixed line