Abstract:
By inputting voltages to global word lines of a memory, and by detecting currents of corresponding global word lines, a relation function between the currents and the voltages can be generated, and connection defects on the global word lines can be determined according to various types of deviation of a relation curve corresponding to the relation function between the currents and voltages.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention discloses a method of detecting connection defects in a memory and a memory capable of detecting connection defects thereof, and more particularly, a method and a memory for detecting connection defects in the memory according to relations between input voltages on global word lines and corresponding currents. 
     2. Description of the Prior Art 
     Please refer to  FIG. 1 , which illustrates connection defects occurring on word lines of a conventional memory. In  FIG. 1 , there are two neighboring sub word line drivers M 1  and M 2  included by a same memory, wherein the sub word line driver M 1  includes a P-type MOSFET P 1  and an N-type MOSFET N 1 , and the sub word line driver M 2  includes a P-type MOSFET P 2  and an N-type MOSFET N 2 . The sub word line drivers M 1  and M 2  are respectively biased by a voltage source Vpp and a ground GND. The sub word line driver M 1  is connected to a first sub word line W 1 , and the sub word line driver M 2  is connected to a second sub word line W 2 . 
     As shown in  FIG. 1 , when gates of the P-type MOSFET P 1  and the N-type MOSFET N 1  are connected to a low-voltage-level input signal provided by a decoder, and when gates of the P-type MOSFET P 2  and the N-type MOSFET N 2  are connected to a high-voltage-level input signal provided by the decoder, a high voltage level occurs on the first sub word line W 1 , and a low voltage level occurs on the second sub word line W 2 , where a symbol L indicates a low voltage level in  FIG. 1 , and a symbol H indicates a high voltage level in  FIG. 1 . 
     However, when there is a connection defect, i.e. a short circuit, between the first sub word line W 1  and the second sub word line W 2 , so that a DC leakage path is introduced, as shown in  FIG. 1 , the low voltage level previously on the second sub word line W 2  will be replaced by the high voltage level on the first sub word line W 1 , and it will introduce errors in operations of the memory. The errors worsen when more DC leakage paths are introduced between sub word lines of the memory, tending to lead to reduced accuracy of operations of the memory. 
     SUMMARY OF THE INVENTION 
     The claimed invention discloses a method of detecting connection defects in a memory. The memory comprises a plurality of first global word lines and a plurality of second global word lines. The method comprises providing a plurality of first voltages having different voltage levels to each of the plurality of first global word lines at a first moment, where each of the first voltages is simultaneously provided to the plurality of first global word lines; providing a second voltage to the plurality of second global word lines at the first moment; measuring a plurality of first currents occurred on each of the plurality of first global word lines when the plurality of first voltages are provided to the plurality of first global word lines; and determining whether there are connection defects on the plurality of first global word lines according to relations between the plurality of first currents and the plurality of first voltages. 
     The claimed invention discloses a memory capable of detecting connection defects. The memory comprises a plurality of first global word lines, a plurality of second global word lines, a controlling unit, a current detecting unit, and a processing unit. The controlling unit is coupled to an external power source, the plurality of first global word lines, and the plurality of second global word lines, for providing a plurality of first voltages having different voltage levels to each of the plurality of first global word lines at a first moment, and for providing a second voltage to the plurality of second global word lines at the first moment. Each of the first voltages is simultaneously provided to the plurality of first global word lines. The current detecting unit is coupled to the plurality of first global word lines, for measuring a plurality of first currents occurred on each of the plurality of first global word lines when the plurality of first voltages are provided to the plurality of first global word lines. The processing unit is utilized for determining whether there are connection defects on the plurality of first global word lines according to relations between the plurality of first currents and the plurality of first voltages. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates connection defects occurred on word lines of a conventional memory. 
         FIG. 2  illustrates a block diagram of a memory capable of detecting connection defects on global word lines, according to one embodiment of the present invention. 
         FIG. 3  schematically illustrates two neighboring memory modules UN respectively belonging to two neighboring rows in the memory shown in  FIG. 2 . 
         FIG. 4  illustrates relation curves between the provided plurality of first voltages on the odd global word lines GWLO and the currents occurred correspondingly. 
         FIG. 5  illustrates how to determine whether there is a connection defect on a global word line according to whether a slope of a relation curve of the global word line varies significantly from that of relation curves of other global word lines, according to one embodiment of the present invention. 
         FIG. 6  illustrates how to determine connection defects on global word lines according to deviations of relation curves shown in  FIG. 4 . 
         FIG. 7  illustrates how to determine whether there are connection defects on global word lines according to deviations of starting points of relation curves shown in  FIG. 4 . 
         FIG. 8  illustrates a flowchart of detecting connection defects according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     For effectively detecting connection defects introducing DC leakage paths between word lines of a memory so as to maintain accuracy of operations of the memory, the present invention discloses a method and a memory for detecting connection defects of global word lines of the memory. In the memory, a single global word line is utilized for simultaneously managing a plurality of sub word lines; therefore, detecting connection defects in global word lines is more effective than detecting connection defects in sub word lines. 
     Please refer to  FIG. 2 , which illustrates a block diagram of a memory  200  capable of detecting connection defects on global word lines according to one embodiment of the present invention. As shown in  FIG. 2 , the memory  200  includes at least a plurality of odd global word lines GWLO, a plurality of even global word lines GWLE, a plurality of memory modules UN, a controlling unit  210 , a current detecting unit  220 , a processing unit  230 , and an external power source  240 . Each of the global word lines GWLO or GWLE is coupled to one row of memory modules UN. 
     Please refer to  FIG. 3 , which schematically illustrates two neighboring memory modules UN respectively belonging to two neighboring rows in the memory  200 , where one of the memory modules UN is coupled to an odd global word line GWLO, and the other one of the memory modules UN is coupled to an even global word line GWLE. The odd global word line GWLO is configured to manage a plurality of sub word lines WLO, and the even global word line GWLE is configured to manage a plurality of sub word lines WLE. Each of the sub word lines WLO and WLE is configured to manage a sub word line driver M, which may share similar elements and a similar structure to the sub word line drivers M 1  and M 2  shown in  FIG. 1 . 
     The controlling unit  210  is coupled to the external power source  240 , the plurality of odd global word lines GWLO, and the plurality of even global word lines GWLE, and is configured to provide voltages to the plurality of odd global word lines GWLO and the plurality of even global word lines GWLE. The current detecting unit  220  is coupled to the plurality of odd global word lines GWLO and the plurality of even global word lines GWLE, and is configured to detect currents occurring in response to the voltages provided to the plurality of odd global word lines GWLO and the plurality of even global word lines GWLE. The processing unit  230  is utilized for determining whether there are connection defects on the plurality of odd global word lines GWLO and the plurality of even global word lines GWLE according to relations between the provided voltages and the occurring currents on the plurality of odd global word lines GWLO and the plurality of even global word lines GWLE. The external power source is utilized for providing a voltage required by the controlling unit  210 . 
     How the memory  200  detects connection defects on the plurality of odd global word lines GWLO and the plurality of even global word lines GWLE is described as follows. 
     First, the controlling unit  210  simultaneously provides a plurality of first voltages having different voltage levels to the plurality of odd global word lines GWLO at a first moment, so that the provided first voltages on each of the global word lines GWLO may swing; the controlling unit  210  further provides a second voltage to a plurality of even global word lines GWLE simultaneously at the first moment, where each of the first voltages is higher than the second voltage. Then, the current detecting unit  220  detects currents occurring on the plurality of odd global word lines GWLO in correspondence with the plurality of first voltages. The processing unit  230  retrieves information about the plurality of first voltages from the controlling unit  210 , and retrieves information about the currents occurring in correspondence with the plurality of first voltages from the current detecting unit  220 . Therefore, the processing unit  230  is capable of determining relation functions between a current and a first voltage on each of the global word lines according to the retrieved information. 
     Please refer to  FIG. 4 , which illustrates relation curves between the provided plurality of first voltages on the odd global word lines GWLO and the currents occurring correspondingly. A set of relation curves EF are determined by the processing unit  230 , as shown in  FIG. 4 , and there are no connection defects on the set of relation curves EF. Each of the relation curves EF is corresponding to a single odd global word line GWLO. A voltage swing region SW shown in  FIG. 4  indicates an example of measuring occurring currents on a single global word line GWLO. Since there are differences in voltage levels of the provided plurality of first voltages, a starting point of each of the relation curves EF, i.e. the lowest voltage at each of the relation curves EF, may vary slightly. However, under the assumption that there are no connection defects on each of the odd global word lines GWLO, slopes of the plurality of relation curves EF may be close to or equal to each other, as shown in  FIG. 4 . In other embodiments of the present invention, the controlling unit  210  may detect all global word lines in the memory chip for connection defects, or detect part of the global word lines in the memory chip for connection defects. When the controlling unit  210  merely detects part of the global word lines, the plurality of first voltages are merely provided to the part of the global word lines. Therefore, under different conditions for detecting connection defects, each of the relation curves EF shown in  FIG. 4  may correspond to a plurality of odd global word lines GWLO of a memory section, a memory bank, or a memory chip. 
     However, when there are connection defects in certain odd global word lines GWLO, slopes of the certain odd global word lines GWLO may vary significantly from those of other odd global word lines GWLO having no connection defects. Please refer to  FIG. 5 , which illustrates how to determine whether there is a connection defect on a global word line according to whether a slope of a relation curve of the global word line varies significantly from that of relation curves of other global word lines. As shown in  FIG. 5 , there is a relation curve EF having a significantly different slope from others among the set of relation curves EF. The processing unit  230  may determine a predetermined deviation; when the relation curve having a significantly different slope indicates a deviation larger than the predetermined deviation, the processing unit  230  may determine that there is at least one connection defect on a global word line GWLO corresponding to the relation curve having the significantly different slope. 
     Besides slope deviation, deviation of relation curves may also be utilized as a reference for determining whether there are connection defects on global word lines. Please refer to  FIG. 6 , which illustrates how to determine connection defects on global word lines according to deviations of relation curves shown in  FIG. 4 . Among the relation curves EF shown in  FIG. 6 , there is one relation curve having a similar slope as the others but having a significantly larger deviation from the others. The processing unit  230  may determine a predetermined deviation TM. When the deviation of the relation curve is larger than the predetermined deviation TM, as shown in  FIG. 6 , the processing unit  230  may determine that there is at least one connection defect on a global word line GWLO corresponding to the relation curve having the larger deviation. 
     In another embodiment of the present invention, deviation of a starting point of a relation curve may be utilized for determining whether there are connection defects on a global word line corresponding to the relation curve. Please refer to  FIG. 7 , which illustrates how to determine whether there are connection defects on global word lines according to deviations of starting points of relation curves shown in  FIG. 4 . As shown in  FIG. 7 , besides a first group of relation curves EF having starting points close to each other, there are a second group of deviation points DE having voltages close to starting points of the first group of relation curves EF but having much larger currents than starting points of the first group of relation curves EF. The much larger currents are introduced by DC paths caused by connection defects, and each of the deviation points DE corresponds to at least one global word line having at least one connection defect. In one embodiment of the present invention, a predetermined value, e.g. a predetermined current deviation DF shown in  FIG. 7 , may be determined in advance; therefore, when a voltage is inputted to a global word line, and when an initial current occurring on a relation curve of the global word line deviates significantly from those of relation curves of most other global word lines, a fact that at least one connection defect exists on the global word line can be determined without further swinging the voltages on the global word line. 
     In one embodiment of the present invention, as long as at least one of the conditions, including a highly-deviated slope, a highly-deviated curve, and a highly-deviated initial value, is met, a fact that at least one connection defect exists on a corresponding global word line can be determined. 
     In embodiments shown in  FIGS. 4-7 , the abovementioned detecting method can also be utilized for detecting connection defects on even global word lines GWLE, as long as a plurality of fourth voltages having different voltage levels are provided to the plurality of even global word lines GWLE, and as long as a third voltage is provided to the plurality of odd global word lines GWLO at the same time, where each of the plurality of fourth voltages is higher than the third voltage. 
     Note that the step of detecting connection defects on the plurality of odd global word lines GWLO is completed at once, instead of respectively detecting the plurality of odd global word lines GWLO at different and exclusive time intervals. Similarly, the step of detecting connection defects on the plurality of even global word lines GWLE is also completed at once. While implementing the procedure of detecting connection defects on global word lines by following the above descriptions and using the memory  200 , the plurality of odd global word lines GWLO are detected at once, and the plurality of even global word lines GWLE are then detected at once according to one embodiment of the present invention; else, the plurality of even global word lines GWLE are detected at once, and the plurality of odd global word lines GWLO are then detected at once according to another embodiment of the present invention. No matter which set of global word lines is detected first, all connection defects on global word lines of the memory  200  can be detected in merely two attempts of detection, and the memory  200  can be adjusted immediately in response to all detected connection defects. Accuracy of operations of and access to the memory  200  can be raised as a result of the adjustment on the memory  200 , so that the problem of bad accuracy of the conventional memory is neutralized. 
     In one embodiment of the present invention, while implementing the detecting method, sub word lines managed by each of the global word lines can be offline or open-circuited, so that noise from the sub word lines can be prevented while the current detecting unit  220  detects currents occurring on global word lines, and so that resolution of measuring the occurring currents on the global word lines is raised. 
     Please refer to  FIG. 8 , which illustrates a flowchart of detecting connection defects according to one embodiment of the present invention. As shown in  FIG. 8 , the detecting method includes steps as follows: 
     Step  302 : Provide a plurality of first voltages having different voltage levels to each of a plurality of first global word lines at a first moment, where each of the first voltages is simultaneously provided to the plurality of first global word lines. 
     Step  304 : Provide a second voltage to a plurality of second global word lines at the first moment. 
     Step  306 : Measure a plurality of first currents occurring on each of the plurality of first global word lines when the plurality of first voltages are provided to the plurality of first global word lines. 
     Step  308 : Determine whether there are connection defects on the plurality of first global word lines according to relations between the plurality of first currents and the plurality of first voltages. 
     Step  310 : Provide a third voltage to the plurality of first global word lines at a second moment. 
     Step  312 : Provide a plurality of fourth voltages having different voltage levels to each of the plurality of second global word lines at the second moment, where each of the fourth voltages is simultaneously provided to the plurality of second global word lines. 
     Step  314 : Measure a plurality of second currents occurring on each of the plurality of second global word lines, when the plurality of fourth voltages are provided to the plurality of second global word lines. 
     Step  316 : Determine whether there are connection defects on the plurality of second word lines according to relations between the plurality of second currents and the plurality of fourth voltages. 
     The procedure of detecting connection defects on odd global word lines GWLO is indicated by Steps  302 - 308 , and the procedure of detecting connection defects on even global word lines GWLE is indicated by Steps  310 - 316 . However, in other embodiments of the present invention, Steps  302 - 308  may also be applied for detecting connection defects on the even global word lines GWLE, and Steps  310 - 316  may also be applied for detecting connection defects on the odd global word lines GWLO. Embodiments formed by reasonable combination and permutation of the steps shown in  FIG. 8 , or by adding limitations mentioned above, should also be regarded as embodiments of the present invention. 
     The present invention discloses a detecting method and a memory for detecting connection defects, so that the memory is capable of monitoring all its connection defects and of adjusting itself for preserving the accuracy of its operations. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.