SE463235B - MOS FIELD POWER TRANSISTOR CONTROL TYRISTOR - Google Patents

Description

463 255 is therefore sufficient to make it impossible to control all of them in the thyristor input field effect transistors. If these are of the depletion type, ie leading in the absence of control voltage, they can never be controlled to a non-conductive state, thus making ignition of the thyristor impossible. If the transistors are off enrichment type, ie normally non-conductive, they cannot be controlled to conductive stand, thereby making it impossible to extinguish the thyristor. A single short-circuit of the type described thus means that the entire component becomes defective and must be discarded, which makes it difficult or impossible to obtain a satisfactory satisfactory replacement during manufacture.

DISCLOSURE OF THE INVENTION The invention intends to provide a design of a thyristor of initial specified type, which enables a sharp increase in the yield at manufacturing.

What characterizes a thyristor according to the invention is apparent from the accompanying patent claims.

A thyristor according to the invention is formed with a plurality, preferably a large number of separate thyristor modules, each with a base area, one or more emitter ranges, and one or more field effect transistors for switching off the thyristor module. The field effect transistors are of depleted The field power transistors of each module are via a current limiting device connected to the common extinguishing control connection ningen.

Because the transistors are of the depletion type, they are conductive in the absence of control signal. A short circuit of the field effect transistor controllers in a module therefore means that the thyristor module can never be switched on. The module remains thereby inactive and does not affect the function of other modules.

The current limiting device which connects the transmissions of the defective module with the common fire control connection comes at the appropriate shaping to limit it from the control terminal to the transistor of the module. control the current so much that the other thyristor modules function is not disturbed. 3 4625 255 Thus, in a thyristor according to the invention, a certain number of short-circuiting between board and substrate are tolerated without further deterioration of thyristor function than a certain loss of total thyristor area.

The current limiting device can, for example, consist of a med integrated resistor, or of a diode integrated with the thyristor connected field effect transistor.

According to an embodiment of the invention, ignition current from the common the ignition control connection is supplied to each module via one with the module integrated field effect transistor. This is then controlled depending on the voltage of the extinguishing the control of the transistors in such a way that the supply of ignition current to a defective thyristor module is blocked, thereby eliminating the total need for ignition current reduced.

According to another embodiment of the invention, field effect transitions are provided. insulating layers applied to the substrates on top of the substrate. Hereby and undesired influence between the thyristors and the field effect transistor and a higher degree of packing is made possible.

DESCRIPTION OF FIGURES The invention will be described in more detail in the following in connection with attached figures 1. 2, 3, üa-Ne, 5a, 5b and 6.

Fig. 1 shows in the form of an electrical circuit diagram the construction of a thyristor. torque module at a thyristor according to an embodiment of the invention. Fig. 2 shows schematically in the form of a section through a semiconductor substrate structure of a thyristor module according to Fig. 1. Fig. 3 shows in the form of a circuit diagram in more detail the structure of a thyristor module. Fig. 4a shows how they in a thyristor module the units included may be arranged on the substrate surface. Fig. Üb shows in more detail a part of the surface of the thyristor module. Fig. 4c shows the section A-A in Fig. Äb, and Fig. 4d shows the section B-B. Fig. 4e shows section C-C in Fig. 4a. Figures 5a and 5b show two embodiments where the the power transistors are different from the substrate of an electrically isolated layer. Fig. 6 shows how the current limiting device can be constituted of a diode-connected field effect transistor. 463 255 nu DESCRIPTION OF EMBODIMENTS Fig. 1 shows a thyristor module in an exemplary embodiment of a thyristor according to the invention. The thyristor has four common to all thyristor modules. the same connections, namely a cathode connection K, an extinguishing control connection SS, an ignition control connection TS and an anode connection A. The module shown thyristor TY is connected between the cathode and anode connection. The module has a depletion type MOS field effect transistor FN, connected between one emitter layer (n-emitter) of the thyristor and its adjacent to the emitter base layer (p-base). The transistor's control electrode is via a current limiting device in the form of a resistor R connected to the common extinguishing control connection SS. The transistor is of the n-type. It is thus normally leading and can be made non-conductive by a negative control signal on the handlebars. Ignition current the ignition layer (p-base) of the thyristor is supplied from the common ignition the connection TS via a MOS transistor FP. This transistor is of the p-type and of enrichment type. The transistor is thus normally non-conductive and can be made leading by means of a negative control signal. Its government is associated with controlled by the transistor UN.

The thyristor according to the invention consists of a large number of modules, which are performed in integrated circuit technology on one and the same semiconductor body and which each has the design shown in Fig. 1. All thyristor modules are connected in parallel to the anode and cathode connections common to the modules The connection lines SS are also for the extinguishing signal and TS for the ignition signal common to all in the thyristor in progress modules.

The transistors FN in the thyristor modules are normally conductive, with the thyristor tower TY emitter is shorted. Transistor FP is normally non-conductive.

When the thyristor is to be switched on, the common fire control connection is supplied SS a negative control signal, which makes the transistor UN conductive and cancels the short circuit of the thyristor, and which further makes the transistor FP conductive, whereby an ignition signal supplied to the thyristor via the common ignition the TS connection can be applied to the TY p-base of the thyristor module. When the thyristor to be extinguished, the negative control signal is taken on the extinguishing control connection SS away, with the transistors FN switching into a conducting state and shorting the thyristor modules whose thyristors TY thereby go out.

In the event of a manufacturing defect which, for example, causes the UN of the transistor to control in a module is shorted to the substrate, this transistor will 5,463,235 constantly remain in their non-conductive state. The thyristor module is coming therefore never to be lit. The resistor R will then limit it from the extinguishing control connection SS to the control of the transistor FN floating current, and at the appropriate dimensioning of the resistor and the control signal source will the control voltage applied to the other non-defective thyristor modules to is affected to such an extent that the function of these modules is not disturbed. One defect of the kind now mentioned in a thyristor module thus does not entail - as in previously known thyristors - that the entire thyristor must be discarded, without it causes only failure of the defective module. Since the number of thyristors modules in a thyristor are normally large, the function of the thyristor is only affected to a negligible degree of the failure of a thyristor module, or of a few thyristor modules.

The resistance of the resistor R should in a typical thyristor according to the invention be at least about 10 kohm, for example 50 kohm. The board of tran- However, the system FN has a certain capacitance (C in Fig. 1) to the semiconductor device. the substrate. This capacitance, together with the resistor, has a time con- stant, which gives a delay of the voltage on the handlebar in relation to the signal applied to the common extinguishing control connection SS. The now mentioned capacitance can be kept down by making the modules sufficient still small. For example, each module can be given the size 0.25 x 0.25 mm, which gives a capacitance of the order of 2 pF and - with a resistance of 50 kohm - a time constant of 0.1 ps, which is normally sufficient so as not to adversely affect the function of the thyristor.

As can be seen from the above description, if the transistor's FN control pattern is short-circuited to the substrate - never any negative voltage to the transistor FP, which then cannot become conductive. This prevents ignition current is supplied to the module and unnecessary ignition current consumption is avoided.

The ignition current consumption can, if desired, be kept down by ignition current only certain selected thyristor modules are supplied, the ignition from these may spread to other modules. This can be achieved for example, in the modules that are not to be supplied with ignition current the connection between the transistor FP and the ignition control terminal TS is omitted, or by the connection between the gates of the two transistors FN and FP are omitted.

Fig. 2 schematically shows a section through a thyristor module at a thyristor according to the invention. Transistor FP has been omitted for simplicity. 465 255 The thyristor is formed in a silicon wafer with an anode contact A, a p-emitter layer 1 and an n-base layer 2, which are common to all thyristor modules. The TY p-base of the thyristor consists of the layer 3 and its n-emitter of layer E. Its cathode contact 5a is connected to the common cathode connection K. The transistor UN is trained in a p-pocket 6. Its source- area 8 is connected to the p-base 3 of the thyristor via the contacts 11a and 5b.

Its drain area 7 is connected via a metal contact 11b to the common the same cathode connection K. The drain area 7 is via the metal contact 11b and the heavily p-doped area 6a short-circuited to the p-pocket 6, which prevents the formation of harmful parasite thyristors. Transistor channel range 9 is n-conducting. Its guide 10, for example formed of polycrystalline high doped silicon, is connected via the resistor R to the extinguishing control connection SS.

The resistor may conveniently be formed as an elongate thin layer of poly- crystalline silicon with suitable doping, which is arranged on the substrate and separate from this by an insulating layer.

The P-pocket 6 is preferably made with such a high doping and thus so pass lateral resistance that a hollow current originating from the anode side does not causes the source region 8 of the transistor to function as a parasitic thyristor. For to nevertheless obtain good function of the transistor, this suitability is with a weaker p-doped region Gb below the channel region itself.

The total area of the MOS transistor part 6-11 is suitably made large so that the transistor gets low resistance in its conducting state. The from The hollow current injected into the p-emitter layer 1 goes partly to the MOS transistor part p-pocket 6 of the part, partly to the p-base layer of the thyristor part 3. The larger the area the p-pocket 6 occupies, the less it becomes liquid to the thyristor part itself residual hole current, which needs to be diverted on extinguishing, which also facilitates extinguishing.

Fig. 3 shows in the form of a circuit diagram in more detail the construction of a thyristor module at a thyristor according to the invention. Thyristor part n-emitter layer 4 is divided into several separate layers 4a, Äb etc to enable more efficient extinguishing. These form separate emitter transmissions. times with the p-base layer 3 common to the module further symbolically the n-base layer 2 common to all modules and p-emitter layer 1. The transistor FN in Fig. 1 is shown consisting of a several parts FN1, FN2, FN3 etc, to which the styrene, eg FNS1, are connected partly with the extinguishing control connection SS via the resistor R and partly with the control FPS 7 465 255 at the transistor FP. The transistors FN1 etc can be separate or also joined together into a coherent pattern. This latter shaping will be described in the following.

Fig. Ha shows an example of how the different parts of a thyristor module can be arranged on the surface of the substrate. Along the center line of the module is the transistor FP as well thyristor emitter layer Ha-He arranged. The latter are associated with each other using the metal connector 5. On either side of the center line is two identical field effect transistor parts designed. These are trained in a coherent grid pattern. The gate electrodes of the thyristors form it 15c denoted the grid pattern, and the same pattern is formed by the underlying ones the channel areas. The gate pattern 15c is by means of a contact 15b connected to the gate of the transistor FP and via a contact 15a with one the end of the resistor R. The other end of the resistor is connected to it for the modules common fire control connection SS. The resistor is designed as an elongate layer of polycrystalline silicon, arranged on top of the substrate and separate therefrom by an insulating layer of, for example, silica. Of those of the guide pattern enclosed squares is every other square via contacts 12b, 12c etc. connected to each other and, via a common contact 12a, with thyristor the p-base layer of the part 3. The other boxes are connected to each other via bars 13a, 13b etc and with the contact 5 via connections 1Ha, 1Hb etc. It in the figure to the left of the center line the field effect transistor part is constructed in an identical manner to that now described.

Fig. Hb shows in more detail a part of the surface of the thyristor module. Fig. Hc shows the section A-A marked in Fig. Hb and Fig. Hd show the section B-B. Fig. He shows the section C-C marked in Fig. Ha.

A silica layer H0 is arranged on the surface of the substrate. The contact 5 out- is made of a metal layer which is arranged on top of the oxide layer and via holes 20, 21 in this makes contact with the underlying emitter layer, eg Ha. Cone- the bar 12a is constituted by another metal layer, arranged on the oxide layer and applied in contact with the p-base 3 through holes 2H, 25, 26, etc. in the oxide layer.

A heavily p-doped area 30 provides effective contacting. Field effect the control pattern of the transistors consists of a coherent grid pattern of polycrystalline silicon 35, separated from the substrate by a thin oxide layer.

Panels 36, 38 constitute the n + conductive source regions of the field effect transistors.

They are contacted by fingers 12b, 12c of the contact 12a through holes 37, 39 in oxide layer H0. The source areas are arranged in a p-pocket 6, which at its 465 235 strip is provided with a stronger p-doped area 31. Under the control electrode pattern 35, the n-conducting channel regions 34 of the field effect transistors 34 are arranged. and under these weakly p-leading areas 33. On top of those now mentioned the metal layers, an additional silica layer 41 is provided. and on top this a coherent additional metal layer 27, which forms the tyris- towers for all modules common cathode connection.

Fig. 4d shows on the left how the contact 5 via a hole 23 in the oxide layer 41 contacted by the cathode contact 27. The figure shows the n + conductive layers 48, 49, etc., which constitute the drain regions of the field effect transistors. For short-circuit of these areas to the p-pocket 6, p +-doped areas 43, 50 are provided. nade. Closest to the surface of the substrate are low-resistance areas 44, 51 of e.g. platinum silicide, which provide an effective low-resistance compound.

The metal contact 13a is arranged on the oxide layer 40 and makes via holes 45, 52 in this contact with the layers 44 and 51 and thus with the drain areas. Contact Fig. 13a is in turn contacted through holes 46, 47 of the cathode layer 27. Fig. 4e shows the section C-C in Fig. 4a. It shows the contact 5, which via the holes 20, 21 etc makes contact with the emitter parts 4a. 4b etc, and which in turn via the hole 23 is contacted by the common cathode contact 27. The transistor FP is formed by the p-pocket 3, which encloses a p + -conducting region 62. The latter is via a metal contact 61, which at the edge of the module is connected to a p-conductive layer 60, connected to the common ignition control connection TS.

The gate of the transistor consists of a polycrystalline silicon layer 63, which via a metal contact 64 is connected to the guide pattern 15b, 15c (Fig. 4a).

Fig. 5a and Fig. 5b show alternative embodiments of the invention. at which field effect transistors for shorting the emitters of the thyristors transitions are arranged on electrically insulating layers. Fig. 5a shows it the common n-base layer 2 and the p-pocket 3, in which the separate emitters the parts 4a and 4b are arranged. These are provided with metal contacts 70, 71, which are contacted by the common cathode contact 27. Between the two the emitter parts 4a and 4b are arranged a p-area 72, the metal contact of which 73 is contacted by the cathode contact 27. Between this p-region and each and one of the emitter parts is an insulating layer 75 applied. On top of this is, for example in a recrystallized silicon layer, the n + conducting regions 76 and 77 which are the source and drain regions of the field effect transistor.

Between these a weaker n-doped channel area 78 is arranged, above the The field 79 of the field effect transistor is applied. Field effect transistor source area 77 is connected to the p-base 3 by means of a metal contact 9 465 255 80, and the drain region 76 of the transistor is contacted by the contact 73 and is thus connected to the common cathode contact 27. As with that In the previously described embodiment, the transistor is normally conducting and short-circuits the emitter transitions of the thyristors. Using a negative control signal on the gate 79, the transistor can be made non-conductive, whereby the thyristor can turn on and carry power.

Fig. Bb shows a variant of the embodiment shown in Fig. 5a. In addition to that In the embodiment according to Fig. 5b, the transistor shown in Fig. 5a is an external field field transistor 76a, 77a, 78a, 79a arranged on an insulating layer 75. This transistor has the same structure and function as the one in connection to Fig. 5a described in the field effect transistor and gives an short circuit path directly between the cathode contact 70 and the p-base contact 80.

By arranging the field effect transistors as shown in Figs. 5a and 5b separate from the substrate of electrically insulating layers is made possible larger packing density. Furthermore, greater freedom is obtained in the design of field power transistors, and an undesirable interaction between field power the transistors and thyristor parts are effectively prevented.

In the embodiments shown in Fig. 5b, for example, the area ratio is selected A1 / A2 depending on current application. The distance d is chosen so that a basic short circuit of suitable size is obtained (via the weakly p-doped layer 74).

Fig. 6 schematically shows how as an alternative to the resistor R in Fig. 1 one depleted type diode-connected field effect transistor FL can be used for limiting the current flowing to the field effect transistor UN.

The control FLS of the transistor FLS is connected to it to the control connection SS connected the electrode of the transistor. In the event of a negative control signal from the connection SS comes at increasing current the conducting channel of the transistor quickly to be throttled, and the current through the transistor is thereby limited to one approximately constant value. With the help of this embodiment, one can higher control current is obtained for non-defective thyristor modules than at present the case of the resistance described above, and thereby a faster function is obtained.

Claims (8)

10 465 235 PATENT CLAIMS A MOS field effect transistor controlled thyristor which comprises a) a plurality of thyristor modules, each with at least one base region (3) and an emitter region adjacent to the base region (4), which between them form an emitter junction, and with at least one MOS integrated with the thyristor module transistor (FN) for controllable shunting of the emitter junction for switching off the thyristor module; each module's MOS transistor control (10) is connected to the common extinguishing control connection (SS) via a current-limiting device (R) separate from the module. 2. A thyristor according to claim 1, characterized in that the current limiting device consists of a resistor (R) integrated with the thyristor. 3. A thyristor according to claim 1, characterized in that the current limiting device is constituted by a means arranged to limit the current flowing from the common extinguishing control connection to the control electrodes of the thyristor module MOS transistors so that it does not exceed a predetermined value. 4. A thyristor according to claim 1, characterized in that the current limiting device consists of a diode-connected MOS transistor of the depletion type. Thyristor according to one of the preceding claims, in which the thyristor modules have a common ignition control connection (TS), characterized in that in at least one of the thyristor modules the control of the MOS transistors (eg FNS1) is connected to the control (FPS) of an additional MOS transistor of the enrichment type and of the opposite line type (P) as the first-mentioned MOS transistors (N), and that of the source and drain regions of the additional MOS transistor one is connected to the ignition control connection (TS ) and the other to the base area (3). V) “465 255 Thyristor according to one of the preceding claims, characterized in that each thyristor module comprises a plurality of separate emitter regions (Äa, 4b, etc.). Thyristor according to one of the preceding claims, characterized in that the MOS transistors are elongate and form a grid pattern. Thyristor according to one of the preceding claims, characterized in that electrically insulating layers (75) are arranged on the semiconductor body in which the thyristor module is formed, and that the MOS transistors (e.g. 76, 77, 78) 79) are arranged on these layers.