Integrated circuit with current detection

Abstract: An integrated circuit is provided with a current conductor which is to supply current to a semiconductor structure at least temporarily and to supply current to other parts of the circuit. The connection conductor is locally split into a first and a second parallel partial current conductor, the semiconductor structure being connected to the first partial current conductor. The partial current conductors are connected to connection contacts across which a voltage drop can be derived as a measure for the value of the current flowing through the semiconductor structure.

Description: The invention relates to an integrated circuit provided with: a semiconductor structure comprising a current path designed to pass a current at least temporarily during operation, a current conductor of sufficient width and thickness both for supplying the said current to the semiconductor structure during operation and for supplying current to other parts of the circuit, a resistance element between the semiconductor structure and the current conductor designed to generate a voltage drop which is proportional to the strength of the current through the semiconductor structure during operation, two connection contacts across which the said voltage drop can be derived. Integrated circuits in which the current through a semiconductor structure, which forms part of the circuit, is monitored by means of the voltage drop generated by this current across a resistor present for this purpose in a current path of the semiconductor structure are known per se . Such a current monitoring problem occurs, for example, in voltage stabilizers, power end stages, and the like. Generally, the said resistance is created by dimensioning a portion of the metallization pattern in such a way that this portion can function as a (small) resistance. An example of such a specially designed metallization pattern is described in Patent Abstracts of Japan 56-71963 (Japanese application 54-148902). According to this publication, the small resistance consists of a portion of a metal track between two vertical connecting tracks which lead through an insulating layer to further metal tracks at a lower level. Another possibility for manufacturing a resistor of the type referred to above is described in, for example, Patent Abstracts of Japan 56-116658 (Japanese Patent application 55-18982). This known resistor consists of a layer of resistor material of pre-determined length, width and thickness with a connection region at either end. The disadvantage of such a resistor is that it occupies a comparatively large surface area. US-A-4 713 607 discloses a current sensing circuit for measuring the potential difference across a trace having a predetermined resistance formed within a metallization layer. The current drawn by each of a plurality of devices may be measured by providing a parallel-connected trace for each device. The invention has for its purpose to disclose a way in which a resistor of the type referred to above can be realized in an integrated circuit so that the resistance element occupies little space and the integrated circuit is thus given a compact structure. This object is achieved in an integrated circuit of the type referred to in the opening paragraph in that the current conductor is locally divided into a first and a second parallel partial current conductor, an end of the current path of the semiconductor structure is connected to the first partial current conductor, and each of the partial current conductors is connected to one of the said connection contacts. Since the current through the semiconductor structure runs exclusively through the first partial current conductor whereas the current to the further parts of the circuit is branched out over both partial current conductors, a potential difference arises across the connection contacts connected to the two partial current conductors, which potential difference is proportional to the current through the transistors. This means that no separate resistance element needs to be created in the metallization phase. Preferably, the partial current conductors are realized by the formation of a longitudinal split in the current conductor with a length sufficient to achieve that the current path of the semiconductor structure makes contact exclusively with the first partial current conductor. The invention will be explained in more detail below with reference to the accompanying Figures. Figure 1 shows diagrammatically the type of circuit in which the device according to the invention may be used. Figure 2 shows a metallization pattern according to the present art. Figure 3 shows an embodiment of a device according to the invention. Figure 4 shows a detailed view of the split current conductor for the derivation of an equivalent resistance. Figure 5 shows an alternative embodiment of the split current conductor. Figure 6 shows a further embodiment of the split current conductor. Figure 1 shows diagrammatically a type of circuit in which the device according to the invention may be used. Figure 1 illustrates two transistor circuits consisting of a resistor R1, R2, and a transistor T1, T2, respectively, each connected in series with a pair of output terminals k7, k8 and k9, k10, respectively, between two current-conducting lines 10 and 12. The current-conducting lines 10 and 12 are provided with connection terminals k1, k2, respectively, at which an input voltage U in can be offered, while an output voltage U out1' U out2' can be derived from the respective output terminals k7, k8 and k9, k10. Such transistor circuits, which are generally known, are used in, for example, stabilized supplies, amplifier end stages and the like. In many cases it is desirable to have available in the further circuits, of which these stages form part, information about the current supplied by the transistors T1, T2, to the relevant output terminals k7, k9, respectively. This current may be determined from the voltage drop arising across the resistors R1 and R2, respectively. In Figure 1 these voltage drops are designated Vs1 and Vs2 and can be measured across the connection terminals k3, k4, and k5, k6, respectively. Figure 2 shows a practical embodiment of a metallization pattern for realizing the resistances R1 and R2, and further shows diagrammatically the transistors T1 and T2, connected to the current conducting line 10 via the resistors R1 and R2, respectively. The realization shown in Figure 2 is assumed to be known to those skilled in the art. Figure 2 shows a track pattern manufactured from a conducting material, for example aluminium, consisting of a relatively wide track 10, which serves as the main current conductor and from which two current conductors R1 and R2 of smaller dimensions branch off to connection regions E1 and E2, respectively. These connection regions provide the contact with the emitters of the respective tranistors T1 and T2. The structure of these transistors T1 and T2 is not shown in the Figure and is assumed to be known to those skilled in the art. The collector regions of the two transistors are in contact with the respective connection regions C1 and C2, from which conductor tracks run to the contacts k7, k9 (non shown) and possibly to further parts of the circuits. As is diagrammatically shown in Figure 2, the connection between the connection region E1 and the emitter of the transistor T1 may be formed by a number of divided vertical connecting conductors designated with e1, e2. In a similar manner, the connection region C1 is connected to the collecor region proper of the transistor T1 via a number of divided vertical connecting conductors c1, c2, c3. This connecting method is assumed to be known per se to those skilled in the art. The vertical connecting conductors are not shown for the transistor T2, neither are they shown in detail in the subsequent Figures. It will be clear that there is no essential difference between the use of pnp and npn transistors. This means that in the above the terms "emitter" and "collector" can be simply interchanged without detracting from the invention yet to be described. In addition, a different semiconductor structure may be used instead of the tranistor T1, T2, such as a diode, a thyristor, and the like. In the pattern of Figure 2, the conductor tracks R1 and R2, provided they are correctly dimensioned, serve as resistance elements having a small but sufficient resistance for causing a voltage drop across them which can be detected by means of a measuring circuit which can be connected to the terminals k3, k4 and k5, k6 via the measuring lines m3, m4 and m5, m6, respectively. As was stated above, this circuit has the disadvantage that it requires a relatively large surface area for realizing the resistance tracks R1 and R2. An integrated circuit according to the invention is shown in Figure 3. In Figure 3, the main current conductor, through which current is supplied to the transistor T1, is designated with the reference numeral 10 again. This main current conductor is divided into two partial current conductors 10a and 10b by means of a split 11 at the area of the transistor T1. The partial current conductor 10a has no contact of any sort with any part of the transistor T1, whereas the partial current conductor 10b makes contact with the emitter (or collector) of transistor T1. The connection region C1 is in contact with the collector (or emitter) of the transistor T1 and is constructed in the same way as illustrated in Figure 2. The partial current conductor 10a is provided with a contact k3 and the partial current conductor 10b with a contact k4. Measuring lines m3 and m4 extend from the two contacts to further parts of the circuit, where the potential difference across k3 and k4 is further evaluated. It is assumed that the current flows from right to left in Figure 3. A portion of the incoming current I1 + I2 flows through the one partial current conductor 10b to the transistor T1. This portion is designated with I1 in Figure 3. The other portion proceeds to further parts of the circuit and is designated with I2. A result of the current I1 is that a potential difference will arise between the measuring terminals k3 and k4. The through-going current I2, which branches out over the two partial current conductors 10a and 10b first and is then united again, does not contribute to this potential difference. In other words, the potential difference between the terminals k3 and k4 is a measure for the current I1 which runs through the transistor T1. This potential difference may be measured in the same way as in the present art, for example, by means of a suitable measuring circuit in the device of which the circuit according to the invention forms part. A comparison of the Figures 2 and 3 shows, however, that the configuration according to the invention leads to a considerable saving in space. A derivation will now be given of the equivalent resistance network with reference to the Figures 4a and 4b. In Figure 4a, the split portion of the current conductor 10 is shown again. The length of the split 11 is denoted with L, the measuring contacts k3 and k4 are placed in the centre of the split length, so at a distance 0,5 L from the beginning of the split, while it is assumed that the current I1 running through the transistor T1 is taken off at an average distance x from the beginning of the split 11. It is further assumed that the partial current conductor 10a has a width W2 and that the partial current conductor 10b has a width W1. In Figure 4b, the accompanying equivalent resistance network is illustrated. The partial current conductor 10a is divided into two equal resistances Ra by the connection contact k3, while in a similar manner the partial current conductor 10b is divided into two equal resistances Rb by the contact k4. Since the current I1 is branched off at a distance x, one of these resistances Rb is divided into two partial resistances, i.e. a resistance αRb and resistance (1-α)Rb, a variation in the distance x obviously resulting in a similar variation of the factor α. The following relation can be derived for this equivalent resistance network: in which Rm = surface resistance. It is assumed in the above that the contacts k3 and k4 are positioned in the centre of the split length. Although this is not necessary, this positioning is definitely preferable because a maximum potential difference across the contacts k3 and k4 is generated in this way. It should furthermore be noted that the above equations can also be applied in the case in which the current I1 is taken off in portions, for example in a configuration in which a number of connection conductors is present between the current conductor 10b and the subjacent collector region (or emitter region) of the transistor T1, such as has been drawn for a known configuration in Figure 2 (transistor T1). In each particular case, the equations may be adapted for each of the relevant connection conductors (with an adapted value for x each time, after which the results can be combined in a simple manner). As the above equations show, the widths W1 and W2 of the two partialcurrent conductors may be chosen at random to a certain degree (taking into account further requirements imposed on the circuit). In principle, therefore, it is possible to choose the width of one of the two partial current conductors relatively small and the width of the other partial current conductor relatively great. An embodiment in which such a choice was made is illustrated in Figure 5. In Figure 5, the partial current conductor 10a is designed as a separate conductor element which is positioned in parallel with the partial current conductor 10b, which in its turn forms a direct continuation of the main current conductor 10. The partial current conductor 10a is connected to the current conductor 10, at the respective beginning and end of the partial current conductor 10b, at a sufficient distance outside the boundary of the transistor T1. The partial current conductor 10a is provided with contact k3, to which is connected the measuring line m3, and the partial current conductor 10b is provided with the contact k4, to which is connected the measuring line m4. The working principle of this configuration is fully identical to the working principle of the device shown in Figure 3. Another possible embodiment of a device according to the invention is illustrated in Figure 6. In Figure 6, the partial current conductor 10b is again a direct continuation of the main current conductor 10. There is not any objection to choosing the dimension of the current conductor 10 to be equal to that of the partial current conductor 10b. An insulating layer is applied on the current conductor 10 at least locally, which layer is not separately illustrated in Figure 6. The second partial current conductor 10a is subsequently applied on this layer and consists of a metal strip of the desired dimensions, which metal strip is in contact with the current conductor 10 at the areas designated with D1 and D2. The partial current conductor 10a is provided with the contact k3 from which the measuring line m3 extends, and the partial current conductor 10b is provided with the contact k4 from which the measuring line m4 extends. Compared with the configuration of Figure 5, the configuration of Figure 6 has the advantage that even less surface area is required for realizing the device. On the other hand, it entails the disadvantage that a separate separation layer must be applied between the partial-current conductors 10a and 10b because of the vertical structure. In many cases, however, such a separation layer must be applied anyway in the total integration process, in which case the configuration according to Figure 6 may be advantageously used.

Claims: An integrated circuit provided with: a semiconductor structure (T1) forming part of the integrated circuit and being electrically connected at a connection region (C1) to a current conductor (10) of a given width and thickness both for supplying current (I1) to the semiconductor structure (T1) during operation and for supplying current (I2) to other parts of the integrated circuit, a resistance element between the semiconductor structure (T1) and the current conductor (10) designed to generate a voltage drop which is proportional to the strength of the current through the semiconductor structure during operation, two connection contacts (K3,K4) across which the said voltage drop can be derived, characterized in that said resistance element is formed by a portion of the current conductor that is locally divided into a first (10b) and a second (10a) electrically parallel partial current conductor at said connection region (C1); said connection region (C1) of the semiconductor structure (T1) is connected to the first partial current conductor (10b), and each of the partial current conductors (10a,10b) is connected to a respective one of the said connection contacts (K3, K4). An integrated circuit as claimed in Claim 1, characterized in that the connection contact (K4) connected to the first partial current conductor (10b) is situated near the edge of the first partial current conductor (10b) which is remote from the second partial current conductor (10a). An integrated circuit as claimed in Claim 1 or 2, characterized in that the length of the two partial current conductors (10a,10b) is at least approximately the same. An integrated circuit as claimed in Claim 1, 2 of 3, characterized in that the partial current conductors (10a,10b) are realized by the formation of a longitudinal split (11) in the current conductor (10) with a length sufficient to achieve that the current (I1) of the semiconductor structure (T1) flows exclusively within the first partial current conductor (10b). An integrated circuit as claimed in any one of the preceding Claims, characterized in that the partialcurrent conductors (10a,10b) are realized in that a second partial current conductor (10a) is formed, whose ends are connected to the first partial current conductor (10b) at areas which lie outside of the portion of the first part current conductor (10b) which is connected to the semiconductor structure (T1). An integrated circuit as claimed in Claim 5, characterized in that the second partial current conductor (10a) is at least substantially parallel to the first partial current conductor (10b). An integrated circuit as claimed in Claim 5 or 6, characterized in that the second partialcurrent conductor (10a) is manufactured during the same metallization stage as the first partial current conductor (10b). An integrated circuit as claimed in Claim 5 or 6, characterized in that the second partial current conductor (10a) is formed during another metallization step than the first partial current conductor (10b). An integrated circuit as claimed in Claim 8, characterized in that the first and second current conductors (10b,10a) are at least partly positioned one above the other.

Inventors: BOEZEN HENDRIK, BOEZEN, HENDRIK
Applicants: PHILIPS NV, N.V. PHILIPS' GLOEILAMPENFABRIEKEN
Application year: 1990
Main classification: H01L27
IPC codes: H01L27, H01L23, H01L21