Abstract:
Methods of fabricating integrated circuit devices utilize fuse elements to support sequential testing of vertically-integrated test elements during fabrication. These methods include forming a first test element, a first fuse and a first test pad electrically connected by the first fuse to the first test element, on a substrate. The first test element is tested by passing a first current between the first test element and first test pad and through the first fuse. The first fuse is then “cut” by increasing an impedance of the first fuse, which may include breaking the first fuse to create an electrical “open” (infinite impedance) or greatly increasing a resistance of the first fuse (e.g., by narrowing the fuse through electromigration). A second test element and a second test pad, which is electrically connected to the second test element and the first test pad, are then formed on the substrate.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a test method for a semiconductor device and, more particularly to a test method for a semiconductor device using a fuse. 
     BACKGROUND 
     In general, a semiconductor device formed on a semiconductor substrate made of, for example, silicon, is formed through a series of unit processes, including a film stacking process, impurity doping process, a photolithography process for patterning films, and an etching process. In order to determine whether each unit process has accurately been performed to be adapted to the design, failures of manufactured semiconductor devices, including transistors, capacitors, resistors, inductors, and so on, are detected or parameter characteristics thereof are evaluated whenever the unit process is completed. 
     As described above, in order to evaluate electrical properties of semiconductor devices, test elements are formed together with the semiconductor devices. The test elements are generally formed on scribe line regions existing between adjacent integrated circuit chips on a semiconductor substrate. 
     A test element is electrically connected to a pad. In order to test a test element, a probe terminal is brought into contact with the pad to apply a predetermined signal to the test element. Then, the signal output through the pad is analyzed to evaluate the electrical properties of semiconductor devices. 
     However, the respective pads, excluding those pads for grounding, are electrically connected to one test element, to then be used to test one test element. Therefore, as the number of test elements to be tested increases, the number of pads increases. However, since a space of a semiconductor device in which pads are to be formed is restricted, there exists a need for a method of more efficiently testing a test element using a restricted number of pads. 
     SUMMARY 
     Methods of fabricating integrated circuit devices utilize fuse elements to support sequential testing of vertically-integrated test elements during fabrication. According to some embodiments of the invention, a method of fabricating an integrated circuit device can include forming a first test element, a first fuse and a first test pad electrically connected by the first fuse to the first test element, on a substrate. The first test element is then tested by passing a first current between the first test element and first test pad and through the first fuse. After testing of the first test element is completed, the first fuse is “cut” by increasing an impedance of the first fuse, which may include breaking the first fuse to create an electrical “open” (infinite impedance) or greatly increasing a resistance of the first fuse (e.g., by narrowing the fuse through electromigration). A second test element and a second test pad, which is electrically connected to the second test element and the first test pad, are then formed on the substrate. An operation is then performed to test the second test element by passing a second current between the second test element and the second test pad, and by using the cut first fuse to at least inhibit (or completely block) flow of current between the first test pad and the first test element. 
     According to additional embodiments of the invention, the first test pad extends underneath the second test pad and between the second test pad and the substrate. Similarly, the first test element may extend underneath the second test element and between the second test element and the substrate. In addition, the first fuse may have first and second ends/terminals and the cutting of the first fuse may include breaking an electrical connection between the first and second ends/terminals. In some embodiments of the invention, the first fuse is a silicide electromigration fuse. 
     According to still further embodiments of the invention, a method of fabricating an integrated circuit device includes forming a first test element on a substrate and then forming a first electrically insulating layer having first and second electrical interconnects therein, on the first test element. First and second test pads are formed on the first electrically insulating layer. The first and second test pads are electrically connected to the first test element by the first and second electrical interconnects, respectively. Operation of the first test element is then verified by contacting a pair of test probes to the first and second test pads and performing a test operation. A second test element is also formed on the first electrically insulating layer. This second test element is vertically aligned relative to the first test element. A second electrically insulating layer having third and fourth electrical interconnects therein is formed on the second test element. Third and fourth test pads are formed on the second electrically insulating layer. The third and fourth test pads are electrically connected to the second test element by the first and second electrical interconnects, respectively. Operation of the second test element is verified by contacting a pair of test probes to the third and fourth test pads. The first electrical interconnect may include a first fuse therein and the operation of testing the second test element may be preceded by blowing the first fuse. 
     According to still further embodiments of the invention, an integrated circuit device includes a first test element on a substrate and a first electrically insulating layer on the first test element. A second test element is provided on the first electrically insulating layer and is vertically aligned relative to the first test element. A second electrically insulating layer is provided on the second test element and first and second test pads are provided on the second electrically insulating layer. The first test pad is electrically connected to the first and second test elements by first and second electrical interconnects and the second test pad is electrically connected to the first and second test elements by third and fourth electrical interconnects. In addition, to facilitate efficient testing of the multiple test elements, at least one of the first through fourth electrical interconnects includes a fuse element, which can be blown to support sequential testing of the test elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a flow chart of a test method for a semiconductor device according to an embodiment of the present invention; 
         FIGS. 2 to 11  are a plan view and cross-sectional views of a semiconductor device for explaining the test method for a semiconductor device according to an embodiment of the present invention; 
         FIG. 12  is a cross-sectional view of a semiconductor device according to another embodiment of the present invention; 
         FIGS. 13 to 14  are cross-sectional views of a test method for a semiconductor device according to still another embodiment of the present invention; 
         FIG. 15  is a flow chart of a test method for a semiconductor device according to still another embodiment of the present invention; 
         FIGS. 16 to 19  are a plan view and cross-sectional views of a semiconductor device for explaining the test method for a semiconductor device according to still another embodiment of the present invention; 
         FIG. 20  is a plan view of a semiconductor device for explaining the test method for a semiconductor device according to still another embodiment of the present invention; and 
         FIG. 21  is a plan view schematically illustrating a test module formed on a scribe line area. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Advantages and features of the present invention and methods of accomplishing the same may be understood more readily by reference to the following detailed description of preferred embodiments and the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art, and the present invention will only be defined by the appended claims. In the drawings, the thickness of layers and regions are exaggerated for clarity. 
     It will be understood that when an element or layer is referred to as being “connected to,” or “coupled to” another element or layer, it can be directly connected to or coupled to another element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, for example, a first element, a first component or a first section discussed below could be termed a second element, a second component or a second section without departing from the teachings of the present invention. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     A test method for a semiconductor device according to an embodiment of the present invention will be described with reference to  FIGS. 1 to 11 .  FIG. 1  is a flow chart of a test method for a semiconductor device according to an embodiment of the present invention, and  FIGS. 2 to 11  are a plan view and cross-sectional views of a semiconductor device for explaining the test method for a semiconductor device according to an embodiment of the present invention. 
     Referring first to  FIGS. 1 to 3 , a semiconductor device  1  is provided, the semiconductor device  1  including a first test element  10 , a first pad  20  electrically connected to the first test element  10 , and a first fuse  30  electrically connected to the first test element  10  and the first pad  20  (S 10 ). The first test element  10  may be formed on a semiconductor substrate  100  and may be positioned on a first layer level  110 . The first test element  10  may be a test element group (TEG). The first test element  10  may include, for example, a P channel transistor for a logic gate, an N channel transistor for a logic gate, a field N channel transistor, a field P channel transistor, a capacitor for a logic gate, a contact chain or resistor, but is not limited thereto. Throughout this specification, the term “layer level” is used to indicate relative positions of layer levels, but a layer level is not limited to a single layer. For example, a layer level may include a plurality of layers. 
     The first pad  20  is electrically connected to the first test element  10  via the first fuse  30 . The first pad  20  and the first test element  10  may be connected to each other by, for example, a contact structure  40 . A layer level at which the first pad  20  is positioned may be higher than a layer level at which the first test element  10  is positioned. For example, the first test element  10  may be positioned on a first layer level  110  and the first pad  20  may be positioned on a third layer level  130  higher than the first layer level  110 . 
     The first fuse  30  may be electrically connected to the first test element  10  and the first pad  20 . That is to say, the first test element  10  and the first pad  20  are electrically connected by the first fuse  30 . Therefore, the first test element  10  and the first pad  20  may be electrically disconnected by cutting the first fuse  30 . The first fuse  30  may be an electric fuse (e-fuse), for example, a silicide electromigration fuse, or a metal electromigration fuse. 
     In a case where the first fuse  30  is a silicide electromigration fuse, the first fuse  30  may include a silicide layer. If an excessive current flows in the first fuse  30 , atoms in the silicide layer undergo electromigration, so that resistance of the first fuse  30  may increase. If the resistance of the first fuse  30  becomes high, it is difficult for a current to flow through the first fuse  30 . Thus, the first test element  10  and the first pad  20  may become electrically disconnected from each other. 
     In a case where the first fuse  30  is a metal electromigration fuse, the first fuse  30  may include a metal layer. If an excessive current flows in the first fuse  30 , atoms in the metal layer undergo electromigration, so that resistance of the first fuse  30  may increase. If the resistance of the first fuse  30  becomes high, it is difficult for a current to flow through the first fuse  30 . Thus, the first test element  10  and the first pad  20  may become electrically disconnected from each other. 
     As described above, in a case where the first fuse  30  is an e-fuse, a current exceeding a predetermined level is allowed to pass through the first fuse  30 , thereby cutting the first fuse  30 . However, the present invention does not limit the type of the first fuse  30  as long as the first test element  10  and the first pad  20  can be electrically disconnected from each other by cutting the first fuse  30 . For example, the first fuse  30  may be a laser fuse, and the first fuse  30  may be cut by irradiating laser into the first fuse  30 . 
     The first fuse  30  may be formed on a via layer. The via layer level refers to a level at which the contact structure  40  is formed. Referring to  FIG. 3 , the via layer level may be a second layer level  120  at which the contact structure  40  is formed. For example, when the first fuse  30  is a metal electromigration fuse, the first fuse  30  may be formed on a via layer level. 
     Alternatively, unlike in  FIG. 3 , the first fuse  30  may be formed on a different layer level, as shown in  FIGS. 13 and 14 .  FIGS. 13 to 14  are cross-sectional views of a test method for a semiconductor device according to still another embodiment of the present invention. The first fuse  30  may be formed on an active layer or a gate layer level. Here, the active layer level refers to a level at which an active region of the semiconductor device  1  is formed, and the gate layer level refers to a level at which a gate is formed. As shown in  FIG. 13 , the layer level and the gate layer level may be the first layer level  110 . For example, in a case where the first fuse  30  is a silicide electromigration fuse, the first fuse  30  may be formed on an active layer level or a gate layer level. In addition, the first fuse  30  may be formed on a wire layer level. The wire layer level refers to a level at which a metal for a wire  50  is provided. Referring to  FIG. 14 , the wire layer level may be a third layer level  130  where the wire  50  is formed. For example, in a case where the first fuse  30  is a metal electromigration fuse, the first fuse  30  may be formed on the wire layer level. For convenience of explanation, the invention will be made with regard to the first fuse  30  formed on a via layer. However, it should be appreciated that features of the present invention that follow will be applied to the first fuse  30  formed at various positions. 
     The first fuse  30  may be a single type, and may be constituted by a single fuse. However, the type of the first fuse  30  is not limited to the single type, but may be of an array type. The array type of fuse refers to a type in which a plurality of fuses are arrayed. In a case where the first fuse  30  is constituted by a plurality of fuses in array to then be connected to the semiconductor device  1 , the first test element  10  and the first pad  20  can be electrically disconnected simply by cutting some of the plurality of fuses. Therefore, the use of the array type fuse allows the first fuse  30  to be effectively cut. 
     Next, the first test element  10  is primarily tested using the first pad  20  with reference to  FIGS. 1 ,  4  and  5  (S 20 ). A predetermined signal may be input to the first test element  10  or an output signal output from the first test element  10  may be detected by allowing a probe terminal  60  to contact the first pad  20 , first test element  10 . For example, a failure of the first test element  10  may be detected or parameter characteristics may be tested by analyzing the output signal output from the first test element  10 , via the first pad  20 . The primarily testing may be performed on, for example, the third layer level  130 , using the first pad  20 . 
     Next, referring to  FIGS. 1 ,  6  and  7 , the first pad  20  and the first test element  10  are electrically disconnected by cutting the first fuse  30  (S 30 ). The first fuse  30  is cut in different methods according to the type of the first fuse  30 . For example, if the first fuse  30  is an electric fuse, the first fuse  30  may be cut by allowing current of a predetermined level or higher to flow in the first fuse  30 . If the first fuse  30  is cut, the first pad  20  and the first test element  10  become electrically disconnected. 
     In the embodiment illustrated in  FIG. 6 , a circuit is opened by cutting the first fuse  30 . However,  FIG. 6  shows by way of example that cutting of the first fuse  30  exerts the same effect as opening the circuit. That is to say, the first fuse  30  is physically not disconnected. For example, in a case where the first fuse  30  is an e-fuse, even if the first fuse  30  is cut, it is not physically broken but becomes in a state of high resistance. 
     Next, referring to  FIGS. 1 ,  8  and  9 , a second pad  25  electrically connected to the first pad  20  and a second test element  15  electrically connected to the second pad  25  are formed (S 40 ). The first pad  20  and the second pad  25  may be positioned on different layer levels. The layer level on which the second pad  25  is positioned may be higher than the layer level on which the first pad  20  is positioned. For example, the first pad  20  may be positioned on the third layer level  130 , and the second pad  25  may be positioned on a sixth layer level  160  higher than the third layer level  130 . 
     The second pad  25  may be electrically connected to the first pad  20  through, for example, the contact structure  40 . The first pad  20  and the second pad  25 , which are electrically connected, constitute a single pad set. The second pad  25  may be formed to overlap with the first pad  20 . The first pad  20  and the second pad  25  are positioned on different layer levels and overlap with each other. Therefore, only the second pad  25  positioned on a relatively high layer level is illustrated in  FIG. 9 . The second test element  15  is electrically connected to the second pad  25 . The second pad  25  and the second test element  15  may be connected to each other through the contact structure  40  and the wire  50 . 
     The layer level on which the second test element  15  is positioned may be higher than the layer level on which the first test element  10  is positioned. For example, the first test element  10  may be positioned on the first layer level  110  and the second test element  15  may be positioned on the fourth layer level  140  higher than the first layer level  110 . The layer level on which the second test element  15  is positioned may be higher than the layer level on which the first pad  20  is positioned. The second test element  15  is formed after the first test element  10  is tested using the first pad  20 . Therefore, since the second test element  15  may be formed after the first pad  20  is formed, the second test element  15  may be positioned on a higher layer level than the first pad  20 . 
     Next, referring to  FIGS. 1 ,  10  and  11 , the second test element  15  is secondarily tested using the second pad  25  (S 50 ). The secondarily testing of the second test element  15  is performed in a similar manner to the primarily testing of the first test element  10 . However, the secondarily testing may be performed on a different layer level from a layer level on which the primarily testing is performed using the second pad  25 . The secondarily testing may be performed on, for example, a sixth layer level  160 . 
     A current leakage measuring device  70  for compensating for the secondarily testing will now be described with reference to  FIG. 12 .  FIG. 12  is a cross-sectional view of a semiconductor device according to another embodiment of the present invention. In a case where the first fuse  30  is an e-fuse, as described above, even if the first fuse  30  is cut by allowing a current of a predetermined level or higher to flow through the first fuse  30 , the first fuse  30  may not be completely electrically cut. Therefore, since some small current may flow through the first fuse  30  cut during the secondarily testing of the second test element  15 , there is a risk of generating an error in the secondarily testing. Therefore, the semiconductor device  1  according to the embodiment of the present invention may further include the current leakage measuring device  70 . Before performing the secondarily testing, the level of current leaking through the cut first fuse  30  may be measured using the current leakage measuring device  70 . For example, the level of leakage current may be measured using a third pad  27  connected to the current leakage measuring device  70 . Data on the level of leakage current measured by the current leakage measuring device  70  is used in the measured secondarily testing, thereby reducing an error in the secondarily testing. 
     After the testing of the semiconductor device  1  according to the embodiment using the above-described test method is completed, the semiconductor device  1  has the following configuration. The semiconductor device  1  includes the first test element  10 , the second test element  15 , the first pad  20  connected to the first test element  10 , the first fuse  30  cut and electrically connected to the first test element  10  and the first pad  20 , and the second pad  25  electrically connected to the second test element  15  and the first pad  20 . Since the first fuse  30  is cut after testing the first test element  10 , the semiconductor device  1  includes the cut first fuse  30 . 
     In the test method for the semiconductor device according to the embodiment of the present invention, a plurality of test elements are tested at different layer levels using a pad set composed of a plurality of pads electrically connected to each other, and fuses connected between the pad set and the test elements. That is to say, a first test element is tested at a given layer level using the pad set and the fuse therebetween is cut, thereby electrically disconnecting the first test element from the pad set. Next, a second test element may be tested at another layer level using the pad set. That is to say, since a plurality of test elements are tested using one pad set, a limited space of a semiconductor device can be efficiently utilized. 
     A test method for a semiconductor device according to another embodiment of the present invention will be described with reference to  FIGS. 15 to 19 . However, the following description will focus on differences between the test methods for semiconductor devices according to the current embodiment and previous embodiment.  FIG. 15  is a flow chart of a test method for a semiconductor device according to still another embodiment of the present invention and  FIGS. 16 to 19  are a plan view and cross-sectional views of a semiconductor device for explaining the test method for a semiconductor device according to still another embodiment of the present invention. Referring first to  FIGS. 15 to 17 , a semiconductor device  1  is provided, the semiconductor device  1  including a first test element  10 , a second test element  15 , a first pad  20  electrically connected to the first test element  10  and the second test element  15 , and a first fuse  30  electrically connected to the first test element  10  and the first pad  20  (S 110 ). 
     The first test element  10  may be positioned on a first layer level  110  and the second test element  15  may be positioned on a third layer level  130 . However, there is no limitation in the layer levels at which the first test element  10  and the second test element  15  are positioned. The first pad  20  is electrically connected to the first test element  10  and the second test element  15 . The first pad  20  may be connected to the first test element  10  and the second test element  15  through, for example, the contact structure  40 . The first fuse  30  may be electrically connected to the first test element  10  and the first pad  20 . That is to say, the first pad  20  and the first test element  10  are electrically connected through the first fuse  30 . Next, the first test element  10  is primarily tested using the first pad  20  with reference to  FIGS. 15 to 17  (S 120 ). The test method for the first test element  10  is the same as described above. 
     Next, referring to  FIGS. 15 ,  18  and  19 , the first pad  20  and the first test element  10  are electrically disconnected by cutting the first fuse  30  (S 130 ). The cutting method of the first fuse  30  is the same as described above. Next, the second test element  15  is secondarily tested using the first pad  20  (S 140 ). The test method for the second test element  15  is the same as described above. Here, the primarily testing and the secondarily testing may be performed at the same layer level. For example, the first pad  20  may be positioned on a fifth layer level  150  and the primarily testing and the secondarily testing may be both performed on the fifth layer level  150 . 
     After the testing of the semiconductor device  1  according to the embodiment using the above-described test method is completed, the semiconductor device  1  has the following configuration. The semiconductor device  1  includes the first test element  10 , the second test element  15 , the first pad  20  connected to the first test element  10  and electrically connected to the second test element  15 , and the first fuse  30  cut and electrically connected to the first test element  10  and the first pad  20 . Since the first fuse  30  is cut after testing the first test element  10 , the semiconductor device  1  includes the cut first fuse  30 . 
     In the test method for the semiconductor device according to the embodiment of the present invention, a plurality of test elements are tested at different layer levels using a single pad, and a fuse connected between the pad and the test elements. That is to say, a first test element is tested at a given layer level using the pad and the fuse therebetween is cut, thereby electrically disconnecting the first test element from the pad. Next, a second test element may be tested at the same layer level using the same pad. That is to say, since a plurality of test elements can be tested using a single pad, a limited space of a semiconductor device can be efficiently utilized. 
     Next, a wide application of a test method for a semiconductor device will be described with reference to  FIG. 20 .  FIG. 20  is a plan view of a semiconductor device for explaining the test method for a semiconductor device according to still another embodiment of the present invention. First, an application example of the test method for a semiconductor device according to the embodiment shown in  FIG. 1  will now be described. The first test element  10  and the second test element  15  are primarily tested at the first layer level using a plurality of pad sets. Next, the first fuse  30  connected to the first test element  10  and the second test element  15  is cut. Thus, the first test element  10  and the second test element  15  are electrically disconnected from the pad sets to then test third test element  17  and the fourth test element  19 . Finally, the third test element  17  and the fourth test element  19  are secondarily tested at the second layer level higher than the first layer level using the plurality of pad sets. Next, an application example of the test method for a semiconductor device according to the embodiment shown in  FIG. 15  will now be described. The first test element  10  and the second test element  15  are primarily tested at the first layer level using a plurality of pads. Next, the first fuse  30  connected to the first test element  10  and the second test element  15  is cut. Thus, the first test element  10  and the second test element  15  are electrically disconnected from the pads to then test the third test element  17  and the fourth test element  19 . Finally, the third test element  17  and the fourth test element  19  are secondarily tested at the second layer level higher than the first layer level using the plurality of pads. 
     A position of a test module on a semiconductor substrate  100  where test elements and pads are formed will be described.  FIG. 21  is a plan view schematically illustrating a test module formed on a scribe line area. The test module may include test elements and pads. The test module may be disposed on a scribe line area SA of the semiconductor substrate  100 . However, the present invention does not limit the position of the test module on the semiconductor substrate  100 , but the test module may be disposed on a chip area CA on the semiconductor substrate  100 . 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims. It is therefore desired that the present embodiments be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than the foregoing description to indicate the scope of the invention.