DD147898A5 - HIGH VOLTAGE FESTKOERPERFLAECHENSCHALTER - Google Patents

Abstract

A high-voltage solid-state switch suitable for DC and AC operation and capable of blocking in two directions consists of a first p-type semiconductor body on an n-type semiconductor chip substrate. A p + -type anode region and an n + -type cathode region are in sections d. Halbleiterkoerpers. A second P-type region with a larger Stoerstellenkonzentration than the semiconductor body circles the cathode region. The anode region and the second p-type region are separated by a portion of the semiconductor body. The semiconductor chip substrate, which acts like a gate electrode, is designed to make a low-resistance contact thereto. Separate low-resistance contacts are made to the anode region and the cathode region.

Description

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High-voltage solid-state flat switch

Field of application of the invention:

This invention relates to solid state devices, and more particularly to high voltage solid state devices suitable for telephone switching systems and many other applications.

Characteristic of the known technical solutions:

In an article entitled "A Field Terminated Diode" by Douglas E, Houston et al., Published in IEEE Transactions on Electron Devices Vol. ED-23, No. * 8, August 1976, a discrete high voltage A solid-state switch is described that has a vertical geometry and includes an area that can be pinched off or rendered highly conductive by means of the dual charge carrier injection to provide an OFF state to provide an ON state. The "double charge carrier injection" refers to both the injection of holes and electrons that form a conductive plasma in the semiconductor. A problem associated with this switch is that it can not readily be manufactured with other similar switching devices on a common substrate. Another problem is that the spacing between the gratings and the cathode must be kept small in order to limit the size of the control grid voltage. However, this limits the usable voltage range because the grid-to-cathode breakdown voltage is lowered. By this limitation, the application of the two anti-parallel components is drastically limited to relatively low voltages, where anti-parallel connection means that in each case the cathode is connected to the anode of the other component.

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is coupled. Such a circuit would be very suitable as a high-voltage solid-state bidirectional switch. Another problem is that the base region must ideally be heavily doped in order to prevent the anode from passing through to the grid; however, this leads to a low breakdown voltage between the anode and the cathode. A widening of the base region causes a limitation of the punch-through effect, but it also increases the resistance of the components in the ON state,

Aim of the invention;

What is desired is a solid state switch that is easily integrated so that two or more switches can be fabricated simultaneously on a common substrate, with each switch being capable of blocking relatively high voltages in two directions.

Explanation of the essence of the invention:

The present invention relates to a solid-state device having a semiconductor body whose volume is of the one conductivity type and has a major surface within which the semiconductor body is formed on a semiconductor substrate (substrate) of the opposite conductivity type. Separate localized first and second regions are present in the semiconductor body * The first region is of one conductivity type and the second region is of the opposite conductivity type. Oeder area has a section that extends to the main area. Both regions have a relatively low resistivity compared to the volume of the semiconductor body. The first and second regions serve as the anode and cathode of the solid state device. Separate low-resistance electrical contacts exist for the anode and cathode regions. The

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Component is designed so that a double charge carrier injection takes place during operation. The semiconductor body is in contact with the substrate, and the substrate is adapted to provide an electrode coupled thereto with the ability to serve as the gate electrode of the device.

The device, when properly designed, may be operated as a switch characterized by a low resistance current path between the anode and cathode when in the ON state (conductive state) and by a high resistance current path between the anode and cathode when it is is in the OFF state (locked state). The potential applied to the gate electrode determines the state of the switch. During the ON state, a double charge carrier injection occurs which reduces the resistance between the anode and cathode.

In another embodiment of the invention, a semiconductor body of the type described above, comprising the first and second regions; with the exception of the main surface portion of the same with a semiconductor region of the opposite conductivity type surrounded. A plurality of semiconductor bodies, which are all surrounded by a separate semiconductor region, are formed in a common semiconductor chip of the one conductivity type, wherein sections of the semiconductor wafer separate all the semiconductor bodies from each other.

These solid state devices, referred to as diode gate switches (GDS), when properly designed, may lock relatively large potential differences between the anode and cathode regardless of the polarity in the OFF state, and they may have relatively large currents in the ON state

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conduct relatively low voltage drop between anode and cathode.

The two-sided blocking feature makes these GDS devices particularly suitable for many applications. "Two of the GDS devices described above can be coupled together with only one common gate electrode for both devices and the cathodes coupled to the anodes of the other device, respectively , This combination is a bidirectional high voltage switch. Assemblies of GDS devices may be fabricated on a common die to form crosspoints, or two GDS devices may be fabricated with a common gate electrode to form a bi-directional switch.

EXEMPLARY EMBODIMENTS:

Fig. 1 shows a solid-state device in accordance with an embodiment of the invention;

FIG. 2 shows a proposed electrical symbol for the component according to FIG. 1; FIG.

Fig. 3 shows the plan view of a component according to another embodiment of the invention;

Fig. 4 shows the device in accordance with another embodiment of the invention;

Fig. 5 shows a device in accordance with yet another embodiment of the invention;

Fig. 6 shows a device in accordance with yet another embodiment of the present invention; and

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FIG. 7 shows a component in accordance with yet another embodiment of the invention.

In Fig. 1, a semiconductor device IO having two substantially identical diode gate switches GDS1 and GDS2, shown within the dashed line triangles and both formed in a die or substrate 12, is shown. The semiconductor device 10 has a main surface 11, the substrate 12 is of the one conductivity type and acts as a common gate electrode and carrier for GDS1 and GDS2.

An epitaxial layer of opposite conductivity of the substrate 12 is separated from the semiconductor bodies 16 and 16a by semiconductor regions 20. In addition to the two illustrated semiconductor bodies, many further semiconductor bodies 16 and 16a can be formed in the substrate 12. The regions 20 are of the same conductivity as the substrate 12; However, they have a larger impurity concentration and extend from the main surface 11 down to the substrate 12. To the semiconductor body 16 also includes a semiconductor anode region 18 of the same conductivity type as the semiconductor body 16; however, it has a larger impurity concentration. A semiconductor region 22 is of the same conductivity type as the semiconductor body 16; however, it has a lower resistivity than the semiconductor body 16. A semiconductor cathode region 24 is included in a portion of the region 22 and has a portion extending to the main surface 11. The region 24 is of the same conductivity type and has substantially the same impurity concentration as the regions 20. The electrodes 28, 32 and 30 establish a low-resistance contact with the regions 18, 24 and 20, respectively. The region 20 establishes a low-resistance contact with the substrate 12. In this way, the electrode 30 provides a low-resistance contact to

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Substrate 12 and serves as a common gate electrode for GDS1 and GDS2. An electrode 38, which is optional, may be made of a metal or semiconductor material and disposed between anode electrode 28 and cathode electrode 32. The electrode 38 is electrically coupled to the substrate by an electrical connection to the electrode 30 »

The semiconductor body 16a includes semiconductor regions 18a, 22a and 24a. The electrodes 28a, 32a and 30 are coupled to the regions 18a, 22a and * 24a, respectively. These regions are substantially the same as the corresponding regions of the semiconductor body 16. An insulating layer 26 provides for electrical isolation of all electrodes described above from the portions of the structure 10 except those portions which are to be electrically connected.

In one illustrated embodiment, the substrate 12 is of the conductivity type £, the regions 20 and 24 (24a) are of the conductivity type n +, the semiconductor body 16 (16a) is of the conductivity type p-, the region 18 (18a) is of the conductivity type p +, the region 22 (22a) is of the conductivity type ε and has a lower specific resistance than the semiconductor body 16 (16a), and the electrodes 28 (28a), 32 (32a) and 30 are made of aluminum. In this embodiment, the anode electrode 28 is electrically coupled to the cathode electrode 32a, and the cathode electrode 32 is coupled to the anode electrode 28a.

The electrical symbols proposed for GDS1 and GDS2 are shown in FIG. The anode, cathode and gate electrode terminals of the GDS1 are represented by 28, 32 and 30, respectively. The relevant ports of the GDS2 are 28a, 32a and 30, this combination of GDSl and GDS2 acts

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like a bidirectional switch capable of blocking potentials regardless of whether the positive potential is applied to the anode or the cathode of the two diode gate switches.

GDS1 and GDS2 are both essentially identical and operate in much the same way. Accordingly, the following description of GDSl also applies to GDS2. GDS1 is characterized by a relatively low resistance current path between the anode region 18 and the cathode region 24 when in the ON state (conducting state) and by a considerably larger resistance when in the OFF state (blocking state). In the ON state, the potential of the gate electrode 30 is usually equal to or smaller than the potential of the anode 28. Holes are injected into the semiconductor body 16 from the anode region 18, and electrons are injected into the semiconductor body 16 from the cathode region 24. These holes and electrons can be present in sufficient numbers and form a plasma whose conductivity modulates the semiconductor body 16. As a result, the resistance of the semiconductor body 16 is effectively reduced, so that the resistance between the anode region 18 and the cathode region 24 is relatively low when GDS1 operates in the ON state. This type of operating state, in which both holes and electrons act as current carriers, is referred to as double charge carrier injection. The device described herein is referred to as a diode gate switch (GDS).

The region 22 helps to restrict the penetration of a depletion layer formed between the region 20 and the substrate 12 and the cathode region 24 during operation. Region 22 also contributes to the formation of a surface inversion layer

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between areas 24 and 20. In addition, it allows to keep the distance between the anode region 18 and the cathode region 24 relatively small. This results in a relatively low resistance between the anode region 18 and the cathode region 24 during the ON state.

The current conduction between the anode region 18 and the cathode region 24 is prevented or interrupted when the potential of the gate electrode 30 is considerably more positive than that of the anode electrode 28 and the cathode electrode 32. The amount by which the potential must be more positive to prevent the current conduction or interrupting is a function of the geometry and impurity concentrations of the structure 10. This positive gate potential causes depletion of the portion of the semiconductor body 16 between the gate electrode region 12 and a portion of the oxide layer 26 such that the potential of that portion of the semiconductor body 16 is more positive than that the areas of anode 18 and cathode 24 is. This positive potential barrier prevents the conduction of holes from the anode region 18 to the cathode region 24, and also serves to accumulate electrons emitted from the cathode region 24 before they can reach the anode region 18. As a result, the semiconductor body 16 is substantially constricted in its volume to the dielectric layer 26, wherein the volume portion between the anode and the cathode region (18 and 24) and extends from the region 12 to the dielectric layer 26.

With the aid of electrode 38, the size of the potential required to prevent or interrupt the conduction process can be reduced. In the OFF state, GDS1 is capable of blocking relatively large potentials between the anode and cathode regions in two directions.

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irrespective of which area the more positive potential is present.

During the ON state of GDS1, the p-n junction diode comprising the semiconductor body 16 and the region 20 is forward biased. For the restriction of the power line through the forward biased diode, a current limiting device (not shown) find application.

The anodes and cathodes of GDS1 and GDS2 do not need to be interconnected, GDS1 and GDS2 can be used individually; however, they have the gate electrodes in common.

3, a top view of a preferred embodiment of a fabricated dual GDS semiconductor device 100 is shown. Device 100 is identical to device 10 except that the anode and cathode regions are curved. With the aid of this geometry, the local stress field concentration causing a voltage breakdown can be limited and provides an additional circumference, which is common to the anode and the cathode region, so that the low-resistance in the ON state is easier to implement and the high-current operation is relieved. Device 100 was fabricated on a jv-type substrate having a thickness of 457 μm, 559 μm, and a conductivity of 10 μm, 1O impurities / cm. The semiconductor bodies 160 and 160a are p-type and have a thickness of 30 microns, 40 microns, a width of 720 microns, a length of 910 microns, and an impurity concentration in the range of 5, 9, 9, 10 impurities / cm.sup.-1 curved anode regions 180 and 180a are p + -type and have a thickness of

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19 2 ,,, 4 microns and an impurity concentration of 10 impurities / cm. The curved cathode regions 240 and 240a are n + -type and have a thickness of 2. 4 microns

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and an impurity concentration of 10 impurities / cm "The total length and width of the fabricated circuit is 1910 microns by 1300 microns. The distance between the anode and cathode is usually 120 microns.

Some of the devices produced included lead areas 380 and 380a that were 60 microns wide, and some contained none. The devices fabricated without the regions 380 and 380a required a gate electrode potential which was 22 volts higher than that at the anode to prevent or interrupt the anode-to-cathode power line. The devices fabricated with the conductor regions 380 and 380a required a gate electrode potential which was only 7.5 volts higher than the anode potential to achieve the turn-off effect. The fabricated device was capable of blocking 300 volts and 500 volts To conduct milliamps, wherein the voltage drop between the anode and cathode was 2.2 volts. This device withstood 10 amps of current over a period of one millisecond.

In Fig. 4, a device 1000 is shown, which is very similar to the device 10, wherein all components thereof, which are substantially similar to those of the component 10 or identical to those are identified by the same reference number with adjusting two zeros. The main difference between the devices 1000 and 10 is that in the structure 1000, the semiconductor regions 22 and 22a of the device 10 according to FIG. 1 are omitted. The respective distances between the regions 2400 and 2400a from the region 2000 provide adequate protection against penetration the depletion layer to the regions

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chen 2400 and 2400a and allow the operation of the device 1000 as a high voltage switch.

In Fig. 5, a device 10 000 is shown, which is very similar to the solid state device 10, wherein all components thereof, which are substantially identical to those of the device 10, are identified with the same reference number by adding three zeros «The main difference between the components 10 000 and 10 consists in the application of semiconductor protective ring regions 40 and 40a, which surround the regions 24 000 and 24 000 a and are separated from them by the sections of the semiconductor bodies 16 000 and 16 000 a. The guard ring portions 40 and 40a provide the same type of protection against the surface layer inversion as the portions 22 and 22a of the device 10. The protection is considered to be adequate in some cases to provide a high voltage solid state switch. The guard rings 40 and 40a are of the same conductivity type as the semiconductor bodies 16,000 and 16,000a, but have a lower resistivity. Guard rings 40 and 40a may be expanded (as shown by dashed lines) so as to contact cathode regions 24,000 and 24,000a.

In Fig. 6, a device 100 000 is shown, which is similar to the device 10. All portions of the device 100,000 that are similar or substantially identical to the respective portions of the device are identified by the same reference numeral with four zeros. A difference between the device 100,000 and the device 10 is the use of semiconductor guard regions 400 and 400a, which encircle the cathode regions 240,000 and 240,000a. The guard rings 400 and 400a are similar to the semiconductor guard regions 40 and 40a of the device 10000. The dashed line portion of the guard rings 400 and 400a illustrates that

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they can be extended so that they touch the cathodes 240 and 240 000a. The combination of the regions 220 and 220 000a and the guard rings 400 and 400a provide protection against the inversion of the semiconductor bodies 160 000 and 160 00Oa ₁ , especially between the gate electrode region 200 000 and the cathode region 240 000 and 240 000a provides protection against passing the depletion layer to the cathode region 240,000 and 240,000a. This type of double protection around the cathode region 240,000 and 240,000a is the preferred protection. The regions 220,000 and 220,000a and 400 and 400a are all of the same conductivity type as the semiconductor bodies 160,000 and 160,000a, but have a lower specificity Resistance. The regions 400 and 400a have lower resistivity than the regions 220,000 and 220,000a. Another difference between the device 100,000 and the device 10 are the semiconductor regions 70 and 7Oa ₁ which are of the same conductivity type as the cathode regions 240,000 and 240,000a. The regions 70 and 70a are in electrical contact with the electrodes 380 and 380, 000a and act like upper gate electrodes. The application of the gate electrode regions 70 and 70a results in a reduction of the potential amount required for the interruption and prevention of the current conduction between the anode regions 180,000 and 180,000a and the cathode regions 240,000 and 240,000a.

In Fig. 7, a semiconductor device 42 is shown comprising a plurality of identical diode gate switches (GDS) of which only two, GDS3 and GDS4 (shown within the dashed line triangle) are shown. The semiconductor device 42 includes a semiconductor substrate portion (substrate) 44 that is of a first conductivity type and has a major surface 46. Within a portion of the substrate 44 are separate regions 48 and 48a of opposite conductivity type

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Substrate 44 and are separated by portions of the substrate 44 and by regions 50 which are of the same conductivity type as the substrate 44, but have a greater impurity concentration. The regions 50 are optionally used. The substantially identical semiconductor bodies 52 and 52a are contained within the regions 48 and 48a, respectively.

The semiconductor bodies 52 and 52a are of the same conductivity type as the substrate 44. Within the semiconductor body 52 there is an anode region 54 which is of the same conductivity type as the semiconductor body 52, but which has a larger impurity concentration. Within the semiconductor body 52 there is likewise a region 56 which has the same conductivity as the semiconductor body 52 but has a greater impurity concentration and which is separated from the region 54 by the sections of the semiconductor body 52. A cathode region 58 is located within a portion of the region 56 and is separated from the semiconductor body 52 by the portions of the region 55 g. The cathode region 58 is of the same conductivity type as the region 48.

Electrodes 60, 62, 64 and 66 provide low resistance contact to regions 48, 54, 58 and 50, respectively. If the regions 50 are omitted, the electrode 66 makes contact with the region 44, either directly or via a low-resistance semiconductor region (not shown), such as the region 54, which, however, is contained in a portion of the substrate 44. An insulating layer 68, which is usually made of silicon dioxide, serves to electrically isolate all the electrodes of the structure 42 from the main surface 46 except for those regions to which low resistance contact is desired.

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The semiconductor body 52a, the regions 54a, 56a and 58a and the electrodes 60a, 62a and 64a of the GDS4 are substantially identical to the corresponding regions of the GDS3.

The substrate 44 is usually maintained at the most negative available potential. This serves to reverse the bias of the p-n junctions formed by the regions 48 and 48a and the substrate 44 so that all the GDS devices contained within the substrate 44 are separated from each other with respect to the barrier layers.

GDS3 and GDS4 are operated in substantially the same manner as described for GDS1 and GDS2 of FIG. The region 48 serves as a gate electrode, with the regions 54 and 58 serving as anode or cathode. It should be noted that the gate electrode regions 48 and 48a are physically and electrically isolated, and consequently, GDS3 and GDS4 can be operated substantially completely independently of each other since the respective gate electrodes, anodes and cathodes are electrically isolated. Thus, the device 42 facilitates the fabrication of an assembly of GDS devices, wherein each GDS device may be operated independently of all other GDS devices of the assembly.

The embodiments described herein are intended to illustrate the general principles of the invention. For example, the impurity concentrations, the distances between the regions, and the dimensions of the regions may be altered to allow considerably higher operating voltages and currents than those disclosed. A dielectric layer may be interposed between regions 48 and 48a, and region 44 or dielectric layer may be replaced by regions 44 and 50, respectively. In addition, other types of dielec-

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tric materials such as silicon nitride instead of silicon dioxide can be used. The semiconductor regions such as the region 38 in accordance to be included in the structures shown in Figs, 3, 4, 5, 6 and 7 Figure _# l can. The areas 56 and 56a may be omitted. This reduces the voltage handling capability of the resulting GDS devices, although the distance between the anode and the cathode and between adjacent GDS devices can be increased to extend the usable voltage ranges. In addition, areas 56 and 56a may be replaced by guard rings such as shown around cathode 24,000 in FIG. 5. Furthermore, a region such as the region 220 000 and a guard ring such as the guard ring 4C0 of FIG. 6 may be substituted for the regions 56 and 56a of FIG. The electrodes may be made of doped polysilicon, gold, titanium or other types of conductive materials. The conductivity of all semiconductor substrates and regions is reversible, provided that the voltage polarities are changed accordingly in the manner well known in the art. In such a case, the areas 18, 18a, 180, 180a, 1800, 1800a, 18000, 18000a, 54, 54a, 180000 and 180000a become cathodes and the areas 24, 24a, 240, 240a, 2400, 2400a , 24,000, 24,000a, 58, 58a, 240,000 and 240,000a to anodes. It should be noted that the devices of the present invention permit DC and AC operation.

Claims (8)

217695 claim for invention: 1) A solid-state switching device comprising a semiconductor body whose volume portion is of the first conductivity type, the first region of which is of the first conductivity type, the second region of which is of the second conductivity type opposite to the first conductivity type, and the gate electrode region is of the second conductivity type the first, the second and the Torelektrodenbereich have a lower resistivity than the volume portion and these are separated by sections of the semiconductor body volume portion and wherein the parameters of the switching device are chosen so that when applying a first voltage to the Torelektrodenbereich a depletion region in the semiconductor body is formed, which substantially prevents the flow of current between the first and the second region, and that upon application of a second voltage to the Torelektrodenbereich and when applying appropriate voltages to the first and the second region is formed by double charge carrier injection, a relatively low resistance current path between the first and the second region, characterized in that the first and the second region each comprise a surface on a first major surface of the semiconductor body and the Torelektrodenbereich comprises a semiconductor part with the semiconductor body is in contact along a second surface opposite the first surface. 2) switching device according to item 1, characterized in that the semiconductor body comprises a localized third region of the first conductivity type whose resistivity is between that of the volume of the semiconductor body and the first region, wherein the third region is arranged so that it the second Enclosing area. 217695 3) switching device according to item 1, characterized in that the Torelektrodenbereich shown in FIG. 7 between the semiconductor body volume portion and a semiconductor die substrate portion of the first conductivity type is arranged. 4) switching device according to item 2, characterized in that the conductivities of the semiconductor body, the first region, the second region and the third region of the type p-, p +, n + or ρ are. 5) Switching device according to item 1, characterized in that the Torelektrodenbereich is at least two switching devices in common, wherein the first region of the one component is connected to the second region of the other component and the second region of the first component connected to the first region of the second component is. 6) A switching device according to item 3, characterized in that a plurality of switching devices are accommodated on a semiconductor chip substrate and the semiconductor chip substrate comprises a plurality of regions of the first conductivity type, the resistivity of which, however, is lower than that of the semiconductor chip substrate. 7) The switching device according to item 1, characterized in that the semiconductor body comprises a localized fourth region which encloses the second region, but does not touch it, wherein the fourth region is of the first conductivity type and has a lower resistivity than the volume portion. 217 69 5 8) The switching device according to item 2, characterized in that the semiconductor body comprises a fourth region within a third region, wherein the fourth region encloses, but does not touch the second region and wherein the fourth region is of the first conductivity type and a lower resistivity as the third area has. For this purpose__iL_Seiien drawings