JP3687266B2 - Semiconductor device and semiconductor relay using the device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a field effect semiconductor device that operates by an electric field generated by applying a voltage to an insulated gate electrode, and a semiconductor relay using the device.
[0002]
[Prior art]
Conventionally, there are semiconductor devices of this type having the configurations shown in FIGS. This includes an n-type drain layer A1 having one surface A11, a p-type base layer A2 that forms a pn junction with the drain layer A1, and an n-type that surrounds the center of the base layer A2. A gate that inverts the conductivity type of the channel region A21 by facing the channel region A21, which is the base layer A2 on one surface A11 side sandwiched between the source layer A3, the drain layer A1 and the source layer A3, via the insulating film A4 A plurality of semiconductor elements A each including an electrode A5, a source electrode A6 in contact with both the base layer A2 and the source layer A3, and a drain electrode A7 formed on the other surface A12 of the drain layer A1 are connected to each source electrode A6. The drain electrodes A7 are connected in parallel.
[0003]
More specifically, the widths of the drain layer regions A13, which are the drain layers A1 sandwiched between the channel regions A21 and A21 adjacent to each other, are formed substantially evenly. Further, compared with a general bipolar transistor, it does not have an offset voltage in the on state, and operates by an electric field generated in the gate electrode A5, so that the input resistance is extremely large, and the conductivity type of the channel region A21 is rapidly reversed. It has many advantages such as short switching time.
[0004]
Therefore, in order to turn on and off bidirectional signals having opposite polarities, which are used as switching elements of a semiconductor relay, two of them electrically connect each source electrode A6 and output both drain electrodes A7 and A7. Used as a terminal, connected in series.
[0005]
[Problems to be solved by the invention]
In the conventional semiconductor device described above, when a voltage is applied to the gate electrode A5, the conductivity type of the channel region A21 is inverted by the generated electric field, and the source electrode A6 and the drain electrode A7 can be turned on and switched.
[0006]
However, when connection is made such that the drain potential is lower than the source potential when the conductivity type of the channel region A21 is inverted and turned on, the current-voltage characteristic does not include a discontinuity as shown in FIG. A continuous region B occurs.
[0007]
This phenomenon will be described with reference to a cross-sectional view of the semiconductor element shown in FIG. When the channel region A21 is on and the flowing current is small, the current flows from the source electrode A6 to the drain electrode A7 side through the channel region A21. However, the current increases, and the voltage generated by the sum of the channel resistance Rch and the resistance Rj of the drain layer region A13 sandwiched between both channel regions A21 and A21 is generated at the pn junction between the drain layer A1 and the base layer A2. When the forward voltage of the built-in diode Di formed is exceeded, current flows through the built-in diode Di.
[0008]
As a result, the drain layer A1 undergoes conductivity modulation in which the drain resistance Rd decreases. Therefore, when a current flows from the source electrode A6 to the drain electrode A7, the impedance between the source electrode A6 and the drain electrode A7 changes suddenly at a constant current value, and a discontinuous region B is generated. That is, a plurality of current values exist in the discontinuous region B with respect to one voltage value.
[0009]
Here, in order to eliminate the discontinuous region B of the current-voltage characteristics, the sum of the channel resistance Rch and the resistance Rj of the drain layer region A13 may be increased to cause conductivity modulation while the flowing current is small. However, in this case, the on-resistance of the semiconductor element A is increased.
[0010]
When such a discontinuous region B occurs when used as a switching element of a semiconductor relay, the output current output from one of the drain electrodes A7 and A7 is compared to the input current input to the other. The problem arises that the signal becomes distorted due to the discontinuity.
[0011]
The present invention has been made in view of the above problems, and the object of the present invention is that even when the polarity is reversed, the current passed between the source electrode and the drain electrode continues to the voltage. It is an object of the present invention to provide a changing semiconductor device and a semiconductor relay using the device.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problem, a semiconductor device according to claim 1 includes a first conductivity type drain layer having one surface, and a second conductivity type base layer forming a pn junction between the drain layer and the drain layer. A source layer of the first conductivity type surrounding the central portion of the base layer, a gate electrode for inverting the conductivity type of the channel region sandwiched between the drain layer and the source layer, and contact with both the base layer and the source layer In an insulated gate semiconductor device in which a plurality of semiconductor elements each including a source electrode and a drain electrode formed on the other surface of the drain layer are arranged in parallel with each source electrode and each drain electrode being connected, at least one of a region of both the channel region drain layer region interposed between the adjacent one another, the high resistance portion is provided with a narrower width in the direction along the one side, the one area, the de Are the structure formed by only one of the in-layer region.
[0014]
The semiconductor relay of claim 2, in which using two semiconductor devices according to claim 1, as well as connecting the source electrode to each other, the load signal current between both the drain electrode as a switching element for switching It is the structure used.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described below with reference to FIGS. Such a semiconductor device is composed of a plurality of semiconductor elements 1. Each semiconductor element 1 includes a drain layer 11, a base layer 12, a source layer 13, a gate electrode 14, a source electrode 15, and a drain electrode 16. I have.
[0016]
The drain layer 11 has one surface 11a and the other surface 11b, the conductivity type is n-type, the first conductivity type, and is formed of a semiconductor substrate. The base layer 12 has a central portion 12 a, a p-type conductivity type that diffuses impurities such as boron, and a second conductivity type, and forms a pn junction with the drain layer 11.
[0017]
The source layer 13 is an n-type first conductivity type in which impurities such as phosphorus are diffused. The source layer 13 surrounds the central portion 12a of the base layer 12 and is formed in a substantially square shape. A channel region 12 b, which is the layer 12, is formed between the drain layer 11. The gate electrode 14 is made of metal such as aluminum or polysilicon, facing the channel region 12b sandwiched between the drain layer 11 and the source layer 13 through an insulating film 14a made of silicon oxide, and the channel region 12b The conductivity type is reversed when a voltage is applied.
[0018]
The source electrode 15 is in contact with both the base layer 12 and the source layer 13 by a metal such as aluminum to short-circuit each of them. The drain electrode 16 is formed on the other surface 11b of the drain layer 11 with a metal such as aluminum.
[0019]
A plurality of semiconductor elements 1 are arranged in parallel with each source electrode 15 and each drain electrode 16 being electrically connected. Therefore, a drain layer region composed of one region 11c and another region 11d is formed in the drain layer 11 between the semiconductor elements 1 and 1, sandwiched between the channel regions 12b and 12b adjacent to each other. Here, as shown in FIG. 2, adjacent source layers 13 are connected, a part of the corner portion of the connected source layers 13 is formed at 180 degrees or more, and one region 11 c has a plurality of drain layers. One of the regions is formed. Further, a high resistance portion 11e having a narrow width in the direction along the one surface 11a of the drain layer 11 is provided in the region 11c, and the resistance is extremely increased.
[0020]
The operation of this will be described. When a voltage is applied to the gate electrode 14, the conductivity type of the channel region 12b is inverted from p-type to n-type, and the drain layer 11 (n-type), the base layer 12 (p-type), and the source layer 13 (n The npn junction is inverted from the npn junction formed by the type). Accordingly, the source electrode 15 and the drain electrode 16 are turned on.
[0021]
Here, when the drain potential is lowered with respect to the source potential, one region 11c in the drain layer region is provided with the high resistance portion 11e and has an extremely large resistance, and therefore flows from the source layer 13 through the channel region 12b. Even when the current is small, the current flows through a built-in diode formed by a pn junction between the drain layer 11 and the base layer 12. Accordingly, conductivity modulation occurs in the drain layer 11 with a small current, and no discontinuity occurs in the current-voltage characteristics. Moreover, since the one region 11c is only one of the plurality of drain layer regions, the on-resistance of the semiconductor element 1 does not increase.
[0022]
FIG. 3 shows current-voltage characteristics when the drain potential is electrically connected so as to be lower than the source potential. It can be seen from FIG. 3 that discontinuous points in the current-voltage characteristics do not occur, and therefore there is no plurality of current values for one voltage value.
[0023]
The two are incorporated in a semiconductor relay (not shown) provided with an output unit having two input units and an output terminal, and are used as switching elements of the output unit. The source electrodes 15 are connected to each other and connected in series, and the drain electrodes 16 and 16 are connected to the output terminal, and a signal current is loaded between the output terminals. Then, the signal current that is input to one of the output terminals and changes in polarity is switched and output to the other output terminal. Here, since the source electrodes 15 are connected to each other, when in the on state, the drain potential of one semiconductor device is higher than the source potential and the drain potential of the other semiconductor device is lower than the source potential.
[0024]
In the semiconductor device according to one embodiment, as described above, since the high resistance portion 11e having a narrow width is provided in one region 11c of the drain layer region sandwiched between the channel regions 12b, the drain potential is reduced. Even if it becomes lower than the source potential, the current flows from the source layer 13 to the drain layer 11 through a built-in diode formed between the drain layer 11 and the base layer 12 when the current flowing from the source layer 13 to the drain layer 11 is small. The occurrence of discontinuous points in the current-voltage characteristics can be prevented without having a plurality of current values for one voltage value.
[0025]
Further, since the narrow region 11c is only one of the plurality of drain layer regions 11c and 11e, the width of the other region 11d of the semiconductor element 1 is wide, so that the resistance is reduced and the on-resistance can be lowered. it can.
[0026]
In such a semiconductor relay using two semiconductor devices of one embodiment, since each semiconductor device is used as a switching element that connects the source electrodes 15 to each other, even if the drain potential is lower than the source potential in the ON state, Since each semiconductor device prevents the occurrence of discontinuous points in the current-voltage characteristics, the output current output from one of the drain electrodes 16 and 16 forms a discontinuous point with respect to the input current input to the other. The signal current loaded on the drain electrodes 16 and 16 can be stably switched without being distorted, that is, without being distorted.
[0027]
In the present embodiment, the first conductivity type and the second conductivity type are n-type and p-type, respectively, but they may be p-type and n-type, respectively, and are not limited.
[0028]
Moreover, although the one area | region 11c was formed by one piece among the drain layer area | regions, the one area | region 11c may be formed in multiple numbers, and it is not limited.
[0029]
【The invention's effect】
The semiconductor device according to claim 1, wherein at least one of the drain layer regions sandwiched between the channel regions is formed, and the high resistance portion having a narrow width is provided in the one region. Even if the potential is lower than the potential, when the current flowing from the source layer to the drain layer is small, the current flows through the built-in diode formed between the drain layer and the base layer. Therefore, the occurrence of discontinuous points in the current-voltage characteristics can be prevented without having a plurality of current values, and only one of the plurality of drain layer regions has a narrow width. the resistance becomes smaller width of the region is therefore widely, Ru can be lowered on-resistance.
[0031]
The semiconductor relay of claim 2, in which using two semiconductor devices according to claim 1, since the semiconductor device is used as a switching element connected to one another source electrode, the source potential is the drain potential in the on-state Since each semiconductor device prevents the occurrence of discontinuous points in the current-voltage characteristics, the output current does not form a discontinuous point with respect to the input current, that is, without distortion. The signal current loaded on the drain electrode can be switched stably.
[Brief description of the drawings]
FIG. 1 is a sectional view taken along line XX in FIG. 2 showing an embodiment of the present invention.
FIG. 2 is a plan view of the above.
FIG. 3 is a diagram showing current-voltage characteristics of the above.
4 is a YY cross-sectional view in FIG. 5 showing a conventional example.
FIG. 5 is a plan view of the same.
FIG. 6 is a diagram showing current-voltage characteristics of the above.
FIG. 7 is a cross-sectional view of the above semiconductor element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Semiconductor element 11 Drain layer 11a One surface 11b Other surface 11c One area | region (drain layer area | region)
11d Other region (drain layer region)
11e high resistance portion 12 base layer 12a central portion 12b channel region 13 source layer 14 gate electrode 14a insulating film 15 source electrode 16 drain electrode

Claims (2)

A first conductivity type drain layer having one surface, a second conductivity type base layer forming a pn junction with the drain layer, and a first conductivity type source layer surrounding a central portion of the base layer; A gate electrode that reverses the conductivity type of the channel region sandwiched between the drain layer and the source layer, a source electrode that contacts both the base layer and the source layer, and a drain electrode formed on the other surface of the drain layer. In an insulated gate semiconductor device in which a plurality of provided semiconductor elements are arranged in parallel with each source electrode and each drain electrode being connected,
At least one region of the drain layer regions sandwiched between the channel regions adjacent to each other is provided with a high resistance portion having a narrow width in the direction along the one surface, and the one region includes the drain layer. A semiconductor device formed with only one of the regions . 2. The semiconductor relay according to claim 1, wherein the two semiconductor devices are used as a switching element of an output section for connecting the source electrodes to each other and switching a signal current loaded between the drain electrodes. .

Images