JPH07312427A - Diode - Google Patents

Abstract

PURPOSE:To increase a forward current and obtain excellent reverse recovery characteristics. CONSTITUTION:A diode main body is formed of a junction of a low concentration first conductivity type region 2 and a second conductivity type region 3 formed on the region 2. A first conductivity type anode region 4 is formed on the surface part of the second conductivity type region 3, and a high concentration second conductivity type anode region 5 is formed on the surface part of the first conductivity type anode region 4. The second conductivity type region 3, the first conductivity type anode region 4, and the high concentration second conductivity type anode region 5 are connected with an anode electrode A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diode capable of obtaining a large forward current and a good reverse recovery characteristic.

[0002]

2. Description of the Related Art As a conventional diode, for example, FIG.
0 (Proceeding of 1992 Inte
rnational Symposium on Power Semiconductor Devices
& ICs, Tokyo, pp.60-65). This diode is Emitter
It has a structure called r Short Type Diode (ESD), in which a low-concentration N-type region 12 is formed on a high-concentration N-type substrate 11, and a P-type region 13 is formed on the low-concentration N-type region 12. ing. P-type contact regions 14 and high-concentration N-type regions 15 are alternately formed on the surface of the P-type region 13, and both the P-type contact regions 14 and the high-concentration N-type regions 15 are ohmic-connected to the anode electrode A. ing. High concentration N
The mold substrate 11 is ohmic-connected to the cathode electrode K. P-type contact region 14-P-type region 13-Low concentration N
A PIN diode is formed on the type region 12-high-concentration N-type substrate 11, and a high-concentration N-type region 15-P-type region 13-low-concentration N-type region 12-high-concentration N-type substrate 11 forms an NPN bipolar transistor. There is. The P-type region 13 that serves as the base of the NPN bipolar transistor is connected to the high-concentration N-type region 15 that serves as the emitter via the P-type contact region 14. FIG. 11 shows the current through the diode as a function of time when the diode is switched from forward bias to reverse bias. First, when the forward current I _f flows through the diode while being forward biased and is switched to the reverse bias, the reverse recovery time _{trr of the} diode.
Only during this time reverse current flows through the diode. The time integration (= charge Q _rr ) of the reverse current flowing during the reverse recovery time t _rr is holes of minority carriers accumulated in the low concentration N-type region during the forward bias period, and I _f is If it is large, Q _{rr is} also large, and the reverse recovery characteristic of the diode is deteriorated. In the ESD shown in FIG. 10, the PIN is input during the forward bias period.
Besides the current I _f1 flowing through the diode, a current I _f2 (= I _f −
I _f1 ) flows through the NPN bipolar transistor. That is, when holes are injected from the P-type region 13 into the low-concentration N-type region 12, electrons correspondingly flow from the low-concentration N-type region 12 into the P-type region 12.
It is injected into the mold region 13. The injected electrons are P-type region 1
3 and reaches the high concentration N-type region 15, it flows out to the anode electrode A and becomes a part of the anode current. Therefore, the conventional example shown in FIG. 10 has the same charge Q _rr as the simple PIN diode in which the high concentration N-type region 15 is not formed.
A large amount of forward current I _f can flow. If the forward current of a simple PIN diode is made the same as that of the conventional example shown in FIG. 10, the amount of charge Q _rr becomes large as shown by X in FIG. 11, and the reverse recovery characteristic deteriorates.

[0003]

However, in the conventional diode, the collector-emitter of the NPN bipolar transistor is used in the opposite direction, and the current amplification factor is low. That is, the potential of the low-concentration N-type region 12 corresponding to the collector of the NPN bipolar transistor is lower than the potential of the high-concentration N-type region 15 corresponding to the emitter, and electrons are injected from the collector to the P-type region 13 corresponding to the base. Has become. Since the low-concentration N-type region 12 corresponding to the collector has a low impurity concentration, the low-concentration N-type region 12 to the P-type region 13
The electron injection efficiency is poor. Therefore, even if a large number of holes are injected from the P-type region 13 into the low-concentration N-type region 12, only a small number of electrons are injected from the low-concentration N-type region 12 into the P-type region 13, and the current of the NPN bipolar transistor is increased. The amplification factor is low. As a result, there is a problem that the current I _f2 flowing through the NPN bipolar transistor cannot be increased sufficiently.

The present invention has been made in view of such conventional problems, and an object thereof is to provide a diode capable of increasing a forward current and obtaining a good reverse recovery characteristic. To do.

[0005]

In order to solve the above problems, the present invention firstly provides a low-concentration first conductivity type region and a second-conductivity type region formed on the low-concentration first conductivity type region. To form a diode body, form a first conductivity type anode region on the surface of the second conductivity type region, and form a high concentration second conductivity type anode region on the surface of the first conductivity type anode region. It is characterized in that the second conductivity type region, the first conductivity type anode region and the high concentration second conductivity type anode region are connected to an anode electrode.

Secondly, a high concentration second conductivity type region is formed in at least a part of the surface portion of the second conductivity type region other than the formation region of the first conductivity type anode region, and the high concentration second conductivity type region is formed. The gist is that the second conductivity type region is connected to the anode electrode.

Thirdly, a plurality of the first conductivity type anode regions are formed, and the high concentration second conductivity type anode regions are formed only in a part of the plurality of the first conductivity type anode regions. Is the gist.

[0008]

In the above structure, first, in the diode, in addition to the diode body formed by the junction of the second conductivity type region and the low concentration first conductivity type region, the high concentration second conductivity type anode region is formed. Is formed as an emitter, the first conductivity type anode region as a base, and the second conductivity type region as a collector. Since the bipolar transistor has a high emitter impurity concentration, it has a high carrier injection efficiency into the base and a high current amplification factor. Therefore, at the time of forward bias, the current amplified by the bipolar transistor is added to the forward current flowing through the diode body, and the forward current increases. Further, since the amount of charge accumulated in the low-concentration first conductivity type region during forward bias depends on the forward bias voltage, when the forward current value is the same, the diode of the present invention accumulates more than the conventional example. The amount of charge decreases and the reverse recovery time becomes short.

Secondly, a high concentration second conductivity type region is formed in at least a part of the surface portion of the second conductivity type region other than the formation region of the first conductivity type anode region, and the high concentration second conductivity type region is formed. Since the type region is connected to the anode electrode, in addition to the effect of increasing the forward direction current due to the high current amplification factor of the bipolar transistor during forward bias, the second conductivity type region and the high concentration second conductivity type region are changed to the low concentration first type region. A large number of carriers are injected into the one-conductivity type region, and the current also increases on the diode body side, and the forward current further increases. Further, by forming the high-concentration second conductivity type region, the resistance component of the second conductivity type region with respect to the carrier is reduced, and when the diode is switched from the forward bias to the reverse bias, the carrier is removed from the second conductivity type region. The thyristor formed by the high concentration second conductivity type anode region, the first conductivity type anode region, the second conductivity type region, and the low concentration first conductivity type region rapidly flows out to the anode electrode, and as a result, The reverse recovery time of the diode becomes shorter.

Thirdly, the high-concentration second conductivity type anode region is formed only on a part of the surface portion of the plurality of first conductivity type anode regions, so that the high current amplification factor of the bipolar transistor is similar to the above. The action increases the forward current. Further, the high concentration second conductivity type anode region and the first conductivity type in the thyristor formed of the high concentration second conductivity type anode region, the first conductivity type anode region, the second conductivity type region and the low concentration first conductivity type region. Since the first conductivity type anode region is connected in parallel to the anode region, the resistance component for carriers in the first conductivity type anode region is reduced. As a result, when the diode is switched from the forward bias to the reverse bias, the thyristor turns off faster, and the reverse recovery time of the diode becomes shorter as in the second invention.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 are views showing a first embodiment of the present invention. First, the configuration of the diode will be described with reference to FIG. A low concentration N type region 2 is formed on a high concentration N type substrate 1, and a P type region 3 is formed on the low concentration N type region 2. A plurality of N-type anode regions 4 are formed on the surface of the P-type region 3.
Are formed at appropriate intervals, and high-concentration P-type anode regions 5 are formed on the surface of each N-type anode region 4. P-type region 3, N-type anode region 4 and high concentration P
The type anode region 5 is commonly ohmic-connected to the anode electrode A. FIG. 2 shows an equivalent circuit of the diode. P-type region 3-low concentration N-type region 2-high concentration N
A PIN diode (diode body) 7 is formed on the mold substrate 1. In addition, the N-type anode region 4-P-type region 3
An NPN bipolar transistor 8 is formed on the low-concentration N-type region 2-high-concentration N-type substrate 1, and a PNP bipolar transistor 9 is formed on the high-concentration P-type anode region 5-N-type anode region 4-P-type region 3. There is. The PNP bipolar transistor 9 and the NPN bipolar transistor 8 form a PNPN thyristor. R _p is P-type region 3
, R _n is a resistance component to holes in the N-type anode region 4, and R _n is a resistance component to electrons in the N-type anode region 4.

Next, the operation of the diode constructed as described above will be described. Consider a case where a positive voltage is applied to the anode electrode A with respect to the cathode electrode K and the diode is forward biased. First, holes are injected from the P-type region 3 into the low-concentration N-type region 2, and a forward current flows. Electrons are injected from the low concentration N-type region 2 to the P-type region 3 by the injection of holes. The injected electrons diffuse in the P-type region 3 and reach the N-type anode region 4. N in the region where the forward current is small
When the electrons that have reached the type anode region 4 flow through the N type anode region 4 and reach the anode electrode A, they flow as an anode current. At this time, the electrons receive the resistance component R _n . When the forward current increases, the number of injected electrons increases and the voltage drop due to the resistance component R _n increases. As a result, PNP
The bipolar transistor 9 is turned on, and electrons are injected into the high concentration P-type anode region 5. Due to this electron injection, holes are injected from the high-concentration P-type anode region 5 to the N-type anode region 4. That is, the current is amplified by the PNP bipolar transistor 9. Since the PNP bipolar transistor 9 has a high impurity concentration in the high-concentration P-type anode region 5 corresponding to the emitter, the efficiency of injecting holes into the N-type anode region 4 corresponding to the base is high, and thus the current amplification factor is high. . As a result, a large forward current I
_f flows.

FIG. 3 shows a diode of the present embodiment (in the figure, a
Characteristic line), the ESD (b characteristic line) shown in FIG. 10, and the forward current-voltage characteristic of a simple PIN diode (c characteristic line). When the forward bias voltage V _f is constant, the ESD causes a current larger than the PIN diode by the current I _f2 flowing through the NPN bipolar transistor. In the diode of this embodiment, the forward current I _f becomes larger than the ESD by the current I _f3 flowing through the PNPN thyristor.
Since the amount of electric charge Q _rr accumulated in the low concentration N-type region 2 is determined by the forward bias voltage V _f , the accumulated electric charge in the diode of this embodiment is larger than that in the ESD for the same value of the forward current I _f. The amount of Q _rr is small and the reverse recovery characteristic is improved. At this time, since the current amplification factor of the PNP bipolar transistor 9 is large, I _f3 is large.

FIG. 4 shows an example of the manufacturing process of the diode of this embodiment. First, the low-concentration N-type region 2 is formed on the high-concentration N-type substrate 1 by the epitaxial growth method, and the P-type region 3 is formed on the surface side of the low-concentration N-type region 2 by the thermal diffusion method or the like. (A). By thermal oxidation or the like to form a SiO ₂ film 10, SiO ₂ film 1 by lithography
A window 10a is opened at a predetermined portion of 0 (b). Phosphorus or arsenic is introduced into the surface of the P-type region 3 through the window 10a by the ion implantation method or the like, and the N-type anode region 4 is formed by the thermal diffusion method (c). Boron is again introduced through the window 10a by an ion implantation method or the like to form the high concentration P-type anode region 5 and the SiO ₂ film 10 is removed (d). Finally, an anode electrode and a cathode electrode are formed.

FIGS. 5 and 6 show two types of plane patterns of this embodiment shown in FIG. 5B is a cross-sectional view taken along the line AA of FIG. 5A, and FIG. 6B is B of FIG.
It is a -B line sectional view. FIG. 5 is an example of a stripe pattern. The stripe pattern is easy to design, but it is difficult to increase the density. FIG. 6 shows an example of a circular cell and hexagonal arrangement pattern. The round cell pattern has an advantage that the cell density can be increased.

FIG. 7 shows an example of a circuit using the diode of this embodiment. This circuit is part of an H-bridge or a three-phase inverter and uses an inductive load L using transistors T1 and T2.
It controls the electric current flowing through. Each transistor T
Diodes D1 and D2 of this embodiment are connected in parallel between the emitters and collectors of T1 and T2, respectively. Now, for example, when the transistor T1 is turned on, a current flows in the direction shown in the figure. Next, when the transistor T1 is turned off, the back electromotive force of the inductive load L causes the potential at the point in the figure to turn negative. This negative potential causes the transistor T
Diode D2 is used so that 2 is not destroyed. That is, when the potential of turns negative, the diode D2 is forward-biased and the current flows in the direction of. As a result, the transistor T2 is protected potential at the point is clamped to -V _f. Next, when the transistor T1 is turned on again, current flows in the direction of during the reverse recovery period of the diode D2, and the power source is short-circuited by the transistor T1 and the diode D2. If the reverse recovery characteristic of the diode D2 is poor because the current flowing during this period is large, the transistor T1
Is destroyed. However, since the diode D2 of this embodiment has a good reverse recovery characteristic as described above, the period of power supply short circuit can be shortened and the breakdown of the transistor T1 can be prevented.

FIG. 8 shows a second embodiment of the present invention. In this embodiment, a high concentration P type region 6 is formed on the surface portion of the P type region 3 other than the formation portion of the N type anode region 4, and the high concentration P type region 6 is also ohmic-connected to the anode electrode A. When the forward bias voltage V _f increases, this high concentration P
Since a large number of holes are injected into the low-concentration N-type region 2 from the type region 6 and the P-type region 3, the forward current becomes even larger than that in the first embodiment. Further, by changing the impurity concentration of the high concentration P-type region 6, it becomes possible to set the value of the resistance component R _p for holes shown in FIG. When the resistance component R _p is set to be low, holes are transferred to P when the reverse bias is applied to the diode and the thyristor is about to turn off.
The thyristor can be quickly turned off by quickly flowing out from the mold region 3 to the anode electrode A. As a result, the turn-off time _{trr of the} diode can be shortened. If the high-concentration P-type region 6 is not provided, the thyristor turns on from the edge portion indicated by Y in FIG. 1 and current is likely to be concentrated, so that the dI / dt withstand capability may decrease. However, by providing the high-concentration P-type region 6, it becomes difficult for the edge portion Y to turn on, and the dI / dt withstand capability increases. Further, when the reverse bias voltage changes, the displacement current flows through the resistance component R _p, and as a result, the thyristor may turn on incorrectly. That is, the dV / dt withstand capability of the diode may be reduced by integrating the thyristor structure. However, the dV / dt withstand capability can be increased by reducing the value of the resistance component R _p .

FIG. 9 shows a third embodiment of the present invention. In this embodiment, the high-concentration P-type anode region 5 is formed only on a part of the surface of the plurality of N-type anode regions 4, and the high-concentration P-type anode region 5 is formed on the surface of the other remaining N-type anode regions 4. The P-type anode region 5 is not formed. With this structure, the present embodiment has the diode of FIG.
The structure is such that the ESD shown in FIG. 10 is integrated.
By doing so, it becomes possible to arbitrarily set the ratio of the current flowing through the thyristor in the diode of this embodiment. That is, by integrating the thyristor and the ESD, the resistance component R _n for electrons shown in FIG. 2 is reduced. As a result, the turn-off time of the thyristor becomes shorter and the erroneous turn-on becomes less likely. That is, the turn-off time _{trr of the} diode can be shortened and the dV / dt withstand capability can be increased.

[0019]

As described above, according to the invention described in each claim, the following effects are obtained.

According to the invention of claim 1, the low concentration first
A conductivity type region and a second region formed on the low concentration first conductivity type region
A diode body is formed by a junction with a conductivity type region, a first conductivity type anode region is formed on a surface portion of the second conductivity type region, and a high concentration second conductivity type is formed on a surface portion of the first conductivity type anode region. Forming an anode region, the second conductivity type region, the first
Since the conductive type anode region and the high concentration second conductive type anode region are connected to the anode electrode, the high concentration second conductive type anode region is an emitter and the first conductive type anode region is a base in the diode in addition to the diode body. , A bipolar transistor having the collector of the second conductivity type region is formed. Since the impurity concentration of the emitter of this bipolar transistor is high, the efficiency of carrier injection into the base is high, the current amplification factor is high, and the diode is forward biased. The forward current can be increased by adding the current amplified by the bipolar transistor to the forward current on the main body side. Further, since the amount of charge accumulated in the low-concentration first conductivity type region during forward bias depends on the forward bias voltage, when the forward current value is the same, the diode of the present invention has a larger amount of accumulated charge than the conventional example. As a result, the reverse recovery time can be shortened.

According to the second aspect of the present invention, a high concentration second conductivity type region is formed in at least a part of the surface portion of the second conductivity type region other than the first conductivity type anode region forming portion. Since the high-concentration second-conductivity type region is formed and connected to the anode electrode, in addition to the effect of increasing the forward current due to the high current amplification factor of the bipolar transistor during the forward bias, the second-conductivity-type region and the high-concentration region are formed. A large number of carriers are injected from the second conductivity type region into the low-concentration first conductivity type region, and the current also increases on the diode body side, so that the forward current can be further increased. Further, by forming the high-concentration second conductivity type region, the resistance component of the second conductivity type region with respect to the carrier is reduced, and when the diode is switched from the forward bias to the reverse bias, the carrier is removed from the second conductivity type region. Quickly flowing out to the anode electrode, the high-concentration second conductivity type anode region, the first conductivity type anode region,
The turn-off of the thyristor formed of the second conductivity type region and the low-concentration first conductivity type region is accelerated, and the reverse recovery time of the diode can be further shortened.

According to the third aspect of the present invention, a plurality of the first conductivity type anode regions are formed, and the high concentration second conductivity type anode regions are only a part of the plurality of the first conductivity type anode regions. Since it is formed as described above, the forward current can be increased by the action of the high current amplification factor of the bipolar transistor as in the above. Further, the high concentration second conductivity type anode region and the first conductivity type in the thyristor formed of the high concentration second conductivity type anode region, the first conductivity type anode region, the second conductivity type region and the low concentration first conductivity type region. Since the first conductivity type anode region is connected in parallel to the anode region, the resistance component for carriers in the first conductivity type anode region is reduced, and when the diode is switched from forward bias to reverse bias, the thyristor is turned off. 3. The reverse recovery time of the diode becomes faster.
It can be made shorter as in the described invention.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a first embodiment of a diode according to the present invention.

FIG. 2 is a circuit diagram showing an equivalent circuit of the first embodiment.

FIG. 3 is a characteristic diagram showing forward voltage-forward current characteristics of the first embodiment together with a comparative example.

FIG. 4 is a process drawing showing an example of the manufacturing method of the first embodiment.

FIG. 5 is a diagram showing an example of a plane pattern of the first embodiment.

FIG. 6 is a diagram showing another example of the plane pattern of the first embodiment.

FIG. 7 is a circuit diagram showing a usage example of the first embodiment.

FIG. 8 is a vertical sectional view showing a second embodiment of the present invention.

FIG. 9 is a longitudinal sectional view showing a third embodiment of the present invention.

FIG. 10 is a vertical sectional view showing a conventional diode.

FIG. 11 is a characteristic diagram showing a switching characteristic of the conventional example.

[Explanation of symbols]

 1 High-concentration N-type substrate 2 Low-concentration N-type region 3 P-type region 4 N-type anode region 5 High-concentration P-type anode region 6 High-concentration P-type region A Anode electrode K Cathode electrode

Claims (3)

[Claims] 1. A diode body is formed by a junction of a low-concentration first-conductivity type region and a second-conductivity-type region formed on the low-concentration first-conductivity-type region, and a diode body is formed on a surface portion of the second-conductivity-type region. First
Forming a conductive type anode region, and forming a high concentration second conductive type anode region on the surface of the first conductive type anode region,
A diode, wherein the second conductivity type region, the first conductivity type anode region and the high concentration second conductivity type anode region are connected to an anode electrode. 2. A high-concentration second-conductivity type region is formed in at least a part of a surface portion of the second-conductivity-type region other than the formation part of the first-conductivity-type anode region, and the high-concentration second region is formed. The diode according to claim 1, wherein a conductivity type region is connected to the anode electrode. 3. A plurality of the first conductivity type anode regions are formed, and the high concentration second conductivity type anode regions are formed only in a part of the plurality of the first conductivity type anode regions. The diode according to claim 1.