Title of Invention

INTEGRATED CIRCUIT WITH AN OPERATION MODE SELECTOR SELECTOR LINE

Abstract

The invention relates to an integrated circuit with an operation mode selector line with which the integrated circuit can be transferred into a testing and/or initialization operation mode. The integrated circuit has a special characteristic, in that it is provided with an electrically connected protective layer above the operation mode selector line and at least partly covering it. In this way, unauthorized access to the operating mode selector line transferring the integrated circuit into the testing and/or initialization operation mode can be reliably prevented.

Full Text

2 This invention pertains to an integrated circuit, more particularly to an integrated circuit with an operation mode selector line, by using which the integrated circuit can be transferred into a testing and/or initialization operation mode The principal structure and function of integrated circuits is generally known and need not be explained here. The provision of a testing and/or initialization operation mode in integrated circuits primarily serves the purpose that, immediately after their manufacture, preferably still before their final completion, the integrated circuits can test very quickly and in a simply manner and/or initialize non-volatile storage contained in them. The testing and/or initialization operation mode should however only be activatable in one way, which reliably prevents its activation during 'normal' operation by a later user. Otherwise, later users of me integrated circuit will be able to read confidential data, change the content of the non-volatile storages or resort to some other kind of misuse. It is known how to activate the testing and/or initialization operation mode by means of an operation mode selector line of the integrated circuit, which is men rendered unusable before delivering to later users A possible practical realization of such a kind of operation mode selector line for activating the testing and/or initialization operation mode would be by providing a socalled saw bow. Such a saw bow is described below in more details with reference to the figures 4 and 5, out of which figure 4 shows a section-wise diagram of a top view on a wafer containing integrated circuits, and figure 5 shows an enlarged detailed view of the same. 3 As one can especially see from figure 4, several integrated circuits 1 are provided on the wafer, which in the example under consideration can be individually separated by sawing the wafer and accommodating them in housings on circuit boards or something similar, the respective sawing channels alongs which the wafer has to be sawed for separating the integrated circuits 1, are denoted in the figures with the reference sign 2 The integrated circuits 1 separated by sawing along the said sawing channel 2 consist of a circuit region 11 and an edge region 12 surrounding it In the example under consideration, the circuit region 11 is bordered by a (can also be left out) frame 13 which could be designed here in a socalled metal layer of the integrated circuit 1 In this metal layer generally run metallic conductor paths through which supply voltages and/or the input and/or output signals of the components in the integrated circuits can be guided and which are connected to corresponding contact points of the component by means of through-contacting Each of the integrated circuits has on its right side, as shown in figures 4 and 5, a saw bow 3 as already mentioned above The saw bows are loop-shaped structures which in the present example go through below the frame 13 and come out of the circuit region 11, cross through the edge region 12 and clearly stretch upto the other side of the respective allocated sawing channel 2 (in this example, the saw bow 3 is designed in the form of a socalled poly-layer of the integrated circuit This poly-layer has local structures made of (electrically conductive) poly-silicon which are otherwise particulary used for designing the gate sections of the transistors in the integrated circuits) If one takes the respective integrated circuits 1 into operation for testing and/or initialization process in the condition as shown in figure 4, l e in not separated condition, then the integrated circuits 1 can automatically independently be transferred to the testing and/or initialization operation mode via the respective saw bows 3 This can be effected by the fact that a voltage suitable for activation of the testing and/or initialization operation mode is given out of the integrated circuit via one of the shanks of the respective saw bow, which goes as input via the other shank into a corresponding (operation mode selector-) input of the integrated circuit Alternatively, one can also make the provision that the saw bow does not independently automatically transfer the integrated circuit into the testing and/or initialization 4 operation mode, but that its availability is "only" a necessary prerequisite in order to be able to transfer the integrated circuit into the testing and/or initialization operation mode As the design of the operation mode selector line in the form of a saw bow 3 enables the integrated circuit to get transferred itself into the testing and/or initialization operation mode, the saw bow 3 is partly referred to later also generally as self-activating line If one saws the wafer in order to lead the integrated circuits 1 provided on it to their desired application, then, as one can clearly see in figures 4 and 5, simultaneously also the saw bows 3 or more precisely their shanks get separated, which again has the noticeable consequence that the integrated circuit can no longer be transferred automatically into the testing and/or initialization operation mode If a user however finds a possibility of connecting shank sections of the previous saw bow 3, which run through the edge region 12 of the intigrated circuit, then through this possibility he will be in a position to transfer the integrated circuit into its testing and/or initialization operation mode for purposes of misuse In order to prevent that, one could provide further lines or structures in the immediate vicinity of the saw bow 3 which cannot be destroyed, because they represent important components of the integrated circuits Such a procedure however has the disadvantage that lines and/or structures have to be foreseen very very close to the respective sawing channels, which should not be destroyed by the sawing Instead of the saw bows which have already been mentioned above, which connect an output terminal of the integrated circuit into an input terminal of the same, one can also make provision for operation mode selector lines in the form of lines referred to below as external activation lines, which as their name already suggests, represent "only" an input connection of the integrated circuit and have to be charged externally (for example, by the testing and/or initialisation device) with a pre-determined activation voltage or a pre-determmed activation voltage gradient, in order to effect or enable the switchover of the integiated circuit into its testing and/or initialization operation mode These external activation lines, whose structure 5 somewhat resembles the already described structure of the saw bow, apart from the mentioned difference, can if required, i.e. after testing and/or initialization of the integrated circuit, similarly be interrupted like the already mentioned saw bows, whereby the interruption here is however not only effected by means of sawing, but sawing, but alternatively or additionally also by means of burning with high current or something similar. Just as in the case of separation of the saw bow, here also one has the consequence that the integrated circuits can no longer be transferred into testing and/or initialization operation mode automatically. Even here one can additionally provide as safety measure additional lines or structures in the immediate vicinity of the external activation line, which cannot be destroyed The disadvantage, which has already been mentioned above, is that the lines and /or structures have to be foreseen very close to the sawing channel, which cannot be destroyed by separation of the line or in any other way, cannot be avoided here or at best with a lot of trouble. Therefore, it is the task of this invention to develop a device according to the invention in such a way that an unauthorized access transferring the integrated circuits into the testing and/or initialization operation mode on to the operation mode selector line can be reliably prevented in an easy manner. Tins task is fulfilled by means of its characteristics features of the inventioa According to that, provision is made for an electrically conductive protecting layer above the operation mode selector line, which also covers it at least partly. Now if one tries to contact the operation mode selector line from above, in order to connect portions of it with one another or to charge it with a definite voltage or a definite voltage gradient, men unavoidably an electrical connection comes about between the contacting operation mode selector line and the electrically conductive protector layer running above it, whereby the operation mode selector line can be charged with a voltage which will rule out the activation of the testing and/or initialization operation mode The provisional of the electrically conductive protective layer above the operation mode selector line allows us an unbelievably simple manner to reliably prevent an unauthorized access to the operation mode selector line which will transfer the integrated circuit into the testing and /or initialization operation mode. 6 The invention is described in details below with the help of design examples and the accompanied reference drawings. The following are shown : Fig.1 a diagramatic representation of a top view of a section containing an operation mode selector line of an integrated circuit designed according to the invention, Fig. 2 a sectional view along the line A-B in fig. 1; Fig 3 a sectional view along the line A-B in fig.1, whereby however, here the shanks of a contact bow are contacted from above and connected to one another. Fig. 4 a diagramatic representation of a top view of a traditional wafer containing integrated circuits; and Fig. 5 a diagramatic representation of a top view of a section containing an operation mode selector line of a traditional integrated circuit. In contrast to the traditional integrated circuit, the device as per the invention described below with reference to the figures 1 to 3 reveals an electrically conductive protective layer running over the operation mode selector line However, like before, the operation mode selector line can be designed as saw bow (setf-activating line) or as external activation line or also in any other manner. The manufacture of the device in an integrated circuit as per the invention takes place-apart from the additional measures required for production the said protective layer- in the same way as in the case for traditional integrated circuits. Wherever the same reference signs are used in figures 1 to 3 as well as in figures 4 and 5, they denote-unless specifically mentioned otherwise-the same elements or at least elements corresponding to one another. Now on the basis of figure 1 to 3 the design as per invention of an integrated circuit is described, having a saw bow as the operation mode selector line. However, already at this point it need to be pointed out that the other designs in this context also for the integrated circuits with other operation mode selector line, like for example differently designed self-activation lines or external activation lines of any kind, also have same validity. Figure 1 . 7. shows a diagramatic representation of the section containing the saw bow of an intigrated circuit designed as per the invention, the representation shown in fig 1 conforms to the representation shown in fig 5 as far as the shown cut-out and the depiction method are concerned, corresponding to the already described intigrated circuit and therefore allowing a comparison The integrated circuit as per the invention has a circuit region 11 bordered by a (not compulsory) frame 13, an edge region 12 surrounding the circuit region 11 and a saw bow 3 which is designed so as to stretch from within the circuit region 11 over the edge region 12 upto the other side of a sawing channel 2 and which is also in the shape of a conducting loop Regarding the structure, function and working method of these elements, there is no complete identicality, but relative agreement to a large extent with the corresponding element of the traditional integrated circuit described at the beginning, so that regarding further details one can initially refer to those designs The sections running within the edge region 12 and partly also the sections running through the sawing channel 2 of the saw bow 3 are, as shown in figures 1 to 3, covered by an electrically conductive protective layer 4 Contrary to the representation in the figures, the protective layer 4 should neither be a single continuous protective layer nor a protective layer covering the saw bow 3 without any gap As one can understand better from the later description of the function of the protective layer 4, for the designing of the protective layer 4 it is mainly of importance that the saw bow sections remaining on the integrated circuit after their separation are not contactable without simultaneous contacting of (charged with predetermined voltage) the protective layer Figure 2 shows a diagramatic representation of a layer structure of the integrated circuit in the region of the protective layer 4, more precisely, a cross-section along the line A-B in fig 1 As one can see from fig 2, at the very bottom a carrier element carrying the integrated circuit is provided in the form of sublayer 15 made of semi-conductor material In and/or on the sublayer 15 the components contained in the integrated circuit are designed The cut-out of integrated circuit shown in fig 2 is however free of components, as this is the edge region 12 lying outside the circuit region 11 8 The sublayer 15 is covered with an insulating layer of silicon oxide, into which the saw bow 3 and the protective layer 4 are inserted as shown in fig 2 The saw bow 3 in this example is again realized as poly-silicon structure in a poly 1-layer, more precisely, in a poly-layer lying close to the sublayer However, there is no restriction to this The saw bow 3 can basically be designed in any other kind of electrically conductive layer, e g in a metal layer, it is however advantageous if the saw bow 3 is arranged as deep as possible and as close to the sublayer as possible, because only then its contacting from outside becomes particularly difficult The protective layer 4 running above the saw bow 3 in this example is also similarly made as a poly-silicon structure in a poly-layer, and more precisely in a poly 2-layer lying way above and far from the sublayer Even for this there is no restriction The protective layer 4 can basically also be arranged in any electrically conductive layer above the saw bow, e g in a metal layer, however, it will be advantageous if the protective layer 4 runs relatively close above the saw bow 3 Between the structures forming the saw bow 3 and the protective layer 4, a layer made of the already mentioned insulating material 16 is provided If and as long as the integrated circuit arranged beside each other and above each other on a wafer are not yet separated, or more precisely are not yet sawed, the integrated circuit can be transferred into the testing and/or initialization operation mode By sawing along the sawing channels 2, the saw bow 3 can be separated, as one can see clearly from fig 1 This has the consequence that the integrated circuit can no longer be transferred into the testing and/or initialization operation mode In this condition, activation of the testing and/or initialization operation mode can, if at all, only take place if the saw bow sections (shank) remaining on the integrated circuit after its separation, are contacted from above and connected to one another This condition is made clear in fig 3 Here a cross-section view of the integrated circuit conforming to that of fig 2 is shown, whereby however in this case the shanks of the saw bow (by unauthorized persons) have been contacted from above and connected to one another Contacting of the shanks of the saw bow 3 from above must take place similar to the production of the socalled through-contacts Accordingly, for this it is necessary to locally remove the layers covering the shanks and fill up the thus form funnel-shaped openings with metallic materials, e g tungsten Such contact elements formed as described or in any other way, which are denoted in fig 3 with the reference sign 21, can be connected for example by means of a connecting element 22 running along the surface of the integrated circuit, whereby in the result also the shanks of the previous saw bow 3 contacted by the contact element 21 are electrically connected to one another If the protective layer 4 is not provided, whose function and working method is described more precisely below, then the integrated circuit manipulated in this way or any similar way could be transferred into the testing and/or initialization operation mode in an unauthorized manner This can however be prevented reliably by the protective layer 4 as explained below The arrangement of the protective layer 4 above the shanks of the previous saw bow 3 leads to the fact that the contact element 21 while contacting the said shanks not only comes in contact with these, but also automatically with the protective layer 4 This means that the shanks are connected by an overbndge as shown in fig 3 not only with one another but at the same time also with the protective layer 4 As already mentioned above, the protective layer 4 is made of electrically conductive material Therefore, if one charges the protective layer with a voltage not suitable for activation of the testing and/or initialization operation mode, then also the shanks of the previous saw bow 3 are charged with this or drawn to this potential This again has the consequence that one of the shanks of the previous saw bow 3 cannot get suitable voltage supply through the other shank for activation of the testing and/or initialization operation mode The voltage with which the protective layer 4 is charged for fulfilling its desired objective, depends on the voltage with which the saw bow 3 has to be charged for activation of the testing and/or initialization operation mode The voltage with which the protective layer 4 has to be charged, is preferably a voltage working against the activation of the testing and/or initialisation operation mode, 1. e for example 0V for the case that the testing and/or initialization operation mode is activatable by +5V, or it should be +5V for the case that the testing and/or initialization operation mode is activatable by 0V 10 For charging the protective layer 4 with a voltage unsuitable for activating the testing and/or initialization operation mode, this has an extension 5 as shown in fig 1, which stretches into the circuit region 11 of the integrated circuit and there runs on to a connecting point, through which it is connected to a voltage source which can provide the said voltage The inner resistance of the voltage source and the resistance of the protective layer are so low in terms of ohms, that the shanks of the previous saw bow get drawn to the potential of the protective layer independent of the voltage on these The protective layer 4 stretches, as one can see in fig 1, only to a very small extent into the sawing channel 2 Thereby it is possible in a relatively simple manner to separate the saw bow 2 before sawing along the sawing channel by means of a laser beam or something similar Such a pre-separation of the sawpow can be of interest specially if the integrated circuits are unsawed, I e delivered on the wafer to the order-giver for further processing there Of course it is also possible that the protective layer crosses through the sawing channel in its entire width It is however decisive that the saw bow sections remaining on the integrated circuit after their separation or - generally expressed - operation mode selector line sections are covered around by the protective layer 4 in such a way that a contacting of the operation mode selector line sections without simultaneouly contacting the protective layer is ruled out WE CLAIM 1. Integrated circuit (1) with an operation mode selector line (3), with which the integrated circuit can be transferred into a testing and/or initialization operation mode, characterized in that there is an electrically conductive protective layer (4) above said operation mode selector line, which also partly covers it, and in that said operation mode selector line (3) and said protective layer (4) are separated from one another by at least one insulating layer (16). 2. Integrated circuit as claimed in claim 1, wherein said operation mode selector line (3) is designed as a poly-silicon structure lying close to a sublayer (15). 3. Integrated circuit as claimed in claim 1 or 2, wherein said protective layer (4) is designed as a poly-silicon structure running above said operation mode selector line (3). 4. Integrated circuit as claimed in one of the previous claims, wherein said protective layer (4) in not yet separated condition of said integrated circuit (1) provided on a wafer along with several additional integrated circuits, stretches at least partly over a sawing channel (2), along which a wafer is sawed with the purpose of the separating the integrated circuits. 5. Integrated circuit as claimed in one of the previous claims, wherein said protective layer (4) is arranged and/or structured above said operation mode selector fine (3) in such a way that the operation mode selector line cannot be contacted from outside in the separated condition of the integrated circuit (1) without establishing an electrical connection between the operation mode selector line and the protective layer. 6. Integrated circuit as claimed in one of the previous claims, wherein said protective layer (4) is connected to a voltage source, through which the protective layer is charged with a voltage that is unsuitable for activation of the testing and/or initialization operation mode. 6. 7. Integrated circuit as claimed in claim 6, wherein satd voltage source and at! protective layer (4) are designed in such a way that in case of an electrical connection with the protective layer the operation mode selector line (3) is drawn at least approximately to the electrical protential of the protective layer. Dated this 18th day of AUGUST 1997. The invention relates to an integrated circuit with an operation mode selector line with which the integrated circuit can be transferred into a testing and/or initialization operation mode. The integrated circuit has a special characteristic, in that it is provided with an electrically connected protective layer above the operation mode selector line and at least partly covering it. In this way, unauthorized access to the operating mode selector line transferring the integrated circuit into the testing and/or initialization operation mode can be reliably prevented.

Documents:

01515-cal-1997-abstract.pdf

01515-cal-1997-claims.pdf

01515-cal-1997-correspondence.pdf

01515-cal-1997-description(complete).pdf

01515-cal-1997-drawings.pdf

01515-cal-1997-form-1.pdf

01515-cal-1997-form-2.pdf

01515-cal-1997-form-3.pdf

01515-cal-1997-form-5.pdf

01515-cal-1997-gpa.pdf

01515-cal-1997-priority document.pdf

1515-cal-1997-granted-abstract.pdf

1515-cal-1997-granted-acceptance publication.pdf

1515-cal-1997-granted-claims.pdf

1515-cal-1997-granted-correspondence.pdf

1515-cal-1997-granted-description (complete).pdf

1515-cal-1997-granted-drawings.pdf

1515-cal-1997-granted-form 1.pdf

1515-cal-1997-granted-form 2.pdf

1515-cal-1997-granted-form 3.pdf

1515-cal-1997-granted-form 5.pdf

1515-cal-1997-granted-gpa.pdf

1515-cal-1997-granted-letter patent.pdf

1515-cal-1997-granted-priority document.pdf

1515-cal-1997-granted-reply to examination report.pdf

1515-cal-1997-granted-specification.pdf

1515-cal-1997-granted-translated copy of priority document.pdf