JP2009110584A - Anti-fuse circuit and semiconductor device having the same, and method for writing address to anti-fuse circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anti-fuse circuit capable of disabling a fuse set concerned even if writing to a defective address fails. <P>SOLUTION: The anti-fuse circuit has a plurality of fuse sets 100 including an anti-fuse element 330 for holding data in a nonvolatile manner. The fuse sets include: a plurality of bit storage circuits 210 for storing a defective address; and a disable circuit 230 for disabling the defective address stored in the plurality of bit storage circuits. Since each fuse set 100 has the disable circuit 230, the fuse set to which a defective address has been written once can be disabled after that. Therefore, even if writing a defective address fails, it is not necessary to abolish an entire chip. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an antifuse circuit and a semiconductor device including the same, and more particularly to an antifuse circuit capable of performing writing processing to an antifuse element at high speed and a semiconductor device having the same. The present invention also relates to an address writing method for such an antifuse circuit.

  In a semiconductor device such as a DRAM (Dynamic Random Access Memory), defective addresses are relieved by replacing defective cells that do not operate normally with redundant cells. Usually, a fuse element is used to store a defective address (see Patent Documents 1 and 2). The fuse element in the initial state is in an electrically conductive state, and a defective address can be stored in a nonvolatile manner by cutting the fuse element by irradiation with a laser beam. Therefore, if a plurality of such fuse elements are provided and a desired fuse element is cut, a desired address can be stored. Thus, a normal fuse element is an element that stores information in a nonvolatile manner by changing from a conductive state to an insulating state.

  On the other hand, in recent years, an element called an antifuse element has attracted attention (see Patent Document 3). The antifuse element is an element that stores information by changing from an insulated state to a conductive state, contrary to a normal fuse element. Information is written to the antifuse element by dielectric breakdown due to application of a high voltage. Therefore, unlike ordinary fuse elements, laser beam irradiation is not required for writing. This makes it possible to write a defective address at high speed and eliminates the need for a device such as a laser trimmer. In addition, since the passivation film is not broken by the laser beam irradiation, the reliability of the product can be improved.

However, the resistance value of the dielectric breakdown antifuse element varies greatly depending on the degree of dielectric breakdown and the location where the breakdown occurs. For this reason, in some cases, the resistance value after dielectric breakdown may be on the order of MΩ. In such a case, it is difficult to determine whether the antifuse element is broken or not. However, in the fuse set in which the defective address has been written once, the enable fuse indicating whether or not it is used is also destroyed, so that it cannot be returned to the unused state. For this reason, there is a problem that when writing of a defective address fails, the entire chip must be discarded.
JP-A-10-75170 JP 2006-147651 A JP 2004-227361 A

  Therefore, an object of the present invention is to provide an antifuse circuit capable of invalidating the fuse set even when writing of a defective address fails, and a semiconductor device having the antifuse circuit.

  Another object of the present invention is to provide a method of writing an address to such an antifuse circuit.

  An antifuse circuit according to the present invention includes a plurality of fuse sets including an antifuse element that holds data in a nonvolatile manner, and the fuse sets are stored in a plurality of bit storage circuits for storing defective addresses and a plurality of bit storage circuits. And a disable circuit for invalidating the defective address. The semiconductor device according to the present invention includes such an antifuse circuit. Further, the address writing method according to the present invention includes a first step of activating an enable circuit in a fuse set to which a defective address is to be written, and a disable circuit in the fuse set when the writing of the defective address fails. And a second step of activation.

  According to the present invention, since each fuse set is provided with the disable circuit, the fuse set in which the defective address has been once written can be subsequently invalidated. For this reason, even when writing of a defective address fails, it is not necessary to discard the entire chip.

  It is preferable that the fuse set further includes an enable circuit that validates the defective address stored in the plurality of bit storage circuits. In this case, it is preferable that both the enable circuit and the disable circuit have substantially the same circuit configuration as the bit storage circuit.

  As described above, according to the present invention, the fuse set can be invalidated even when writing of a defective address fails.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a configuration of a semiconductor device 10 according to a preferred embodiment of the present invention.

  The semiconductor device 10 according to the present embodiment is a semiconductor memory such as a DRAM, and includes a memory cell array 11 including a plurality of memory cells, an access circuit 12 for controlling access to the memory cell array 11, and data input / output control for the memory cell array 11. An input / output circuit 13 for performing the command and a command decoder 14 for receiving the command signal CMD are provided. As shown in FIG. 1, the memory cells included in the memory cell array 11 are classified into normal cells 11a and redundant cells 11b. The redundant cell 11b is used to repair a defective address by replacing the defective normal cell 11a.

  The semiconductor device 10 according to the present embodiment includes a plurality of command terminals 21, a plurality of address terminals 22, and a plurality of data terminals 23 as external terminals. The command terminal 21 is a terminal to which a command signal CMD is supplied, and the address terminal 22 is a terminal to which an address signal ADD is supplied. The data terminal 23 is a terminal for outputting the read data DQ and inputting the write data DQ. In addition, a clock terminal 24 to which the clock signal CK is input and a power supply terminal (not shown) are also provided.

  The operation of the semiconductor device 10 during normal operation is specified by a combination of command signals CMD. For example, when the command signal CMD indicates a read operation, the command decoder 14 internally generates a read signal. When the command signal CMD indicates a write operation, the command decoder 14 internally generates a write signal. Is done. These internal commands are supplied to the access circuit 12 and the input / output circuit 13.

  When the read signal is internally generated, the data stored at the address specified by the address signal ADD among the data stored in the memory cell array 11 is accessed, and the read data DQ read is output to the data terminal 23. Access to the memory cell is controlled by the access circuit 12, and the output of the read data DQ is controlled by the input / output circuit 13. On the other hand, when the write signal is internally generated, the write data DQ input to the data terminal 23 is taken into the input / output circuit 13 and written to the address specified by the address signal ADD under the control of the access circuit 12.

  As shown in FIG. 1, the semiconductor device 10 according to the present embodiment further includes an antifuse circuit 31 and an address comparison circuit 32. The antifuse circuit 31 is a circuit that stores an address (defective address RADD) of the defective normal cell 11a, and includes a plurality of antifuse sets, as will be described later.

  The address comparison circuit 32 compares the defective address RADD stored in the antifuse circuit 31 with the address signal ADD supplied via the address terminal 22. The result of the comparison is supplied to the access circuit 12. The access circuit 12 accesses the normal cell 11a when no match is detected by the address comparison circuit 32, and accesses the redundant cell 11b when a match is detected. Thereby, the defective address is relieved.

  Next, the configuration of the antifuse circuit 31 will be described in detail.

  FIG. 2 is a block diagram showing a circuit configuration of the antifuse circuit 31.

  As shown in FIG. 2, the anti-fuse circuit 31 includes a plurality of fuse sets 100 that store defective addresses, a control circuit 110 that controls the operation of the fuse sets 100, and a mode determination circuit 120 that determines an operation mode to be entered. And.

  Each fuse set 100 is a circuit capable of storing one address in a nonvolatile manner. Therefore, the antifuse circuit 31 can store the same number of defective addresses as the fuse set 100. The specific number of fuse sets 100 varies depending on the product, but for example, about 1000 sets are often provided. A specific circuit configuration of the fuse set 100 will be described later.

  The mode determination circuit 120 determines an operation mode to be entered based on the voltages supplied to the external terminals VPPS and VBBS. In the present embodiment, at least “set mode”, “write mode”, and “sense mode” are provided as operation modes.

  The “set mode” is a mode for temporarily latching the defective address in the fuse set 100. In this mode, the antifuse element is not destroyed. The “write mode” is a mode for actually destroying the antifuse element, and is entered after the defective address is latched in the set mode. The “sense mode” is a mode in which a defective address written in the fuse set 100 is read, and this mode is always entered in the actual use state.

  Although not particularly limited, in this embodiment, it is possible to enter the “set mode” by applying 3 V and 0 V to the external terminals VPPS and VBBS, respectively, and by applying 4 V and −2 V, respectively. You can enter “Write Mode”. Further, by entering both the external terminals VPPS and VBBS in an open state, it is possible to enter the “sense mode”. External terminals VPPS and VBBS are terminals that are not used in the actual use state, and are used only during an operation test performed in the wafer state. Therefore, in the actual use state, the external terminals VPPS and VBBS are always open.

  When entering the set mode, the mode determination circuit 120 sets both the mode signals M1 and M2 to the high level, and the control circuit 110 performs the operation in the set mode accordingly. Further, the mode determination circuit 120 sets the levels of the operating voltages VPPSV and VBBSV to supply voltages to the external terminals VPPS and VBBS, that is, 3 V and 0 V, respectively, and supplies them to each fuse set 100.

  When entering the write mode, the mode determination circuit 120 sets the mode signal M1 to the high level and the mode signal M2 to the low level, and the control circuit 110 performs the operation in the write mode accordingly. Further, the mode determination circuit 120 sets the levels of the operating voltages VPPSV and VBBSV to supply voltages to the external terminals VPPS and VBBS, that is, 4V and −2V, respectively, and supplies them to each fuse set 100.

  When entering the sense mode, the mode determination circuit 120 sets the mode signal M1 to the low level and the mode signal M2 to the high level, and the control circuit 110 operates in the sense mode accordingly. Furthermore, the mode determination circuit 120 sets the operating voltages VPPSV and VBBSV to the VSS level.

  FIG. 3 is a block diagram showing a circuit configuration of the fuse set 100.

  As shown in FIG. 3, one fuse set 100 includes m bit storage circuits 210, an enable circuit 220, and a disable circuit 230. Each bit storage circuit 210 corresponds to one bit of a defective address to be stored. Therefore, the number (= m) of bit storage circuits 210 included in one fuse set 100 is equal to (or more than) the number of bits of the address to be stored.

  The enable circuit 220 is a circuit that is activated when the fuse set 100 is validated, and the disable circuit 230 is a circuit that is activated when the fuse set 100 is invalidated. The disable circuit 230 has a higher priority than the enable circuit 220. Therefore, when both the enable circuit 220 and the disable circuit 230 are activated, the fuse set 100 is invalidated. Note that the fuse set 100 is also invalidated when both the enable circuit 220 and the disable circuit 230 are inactive.

  The bit storage circuit 210, the enable circuit 220, and the disable circuit 230 have the same circuit configuration. Specifically, as shown in FIG. 3, all are configured by a selection circuit 310, a latch circuit 320, an antifuse element 330, and a sense circuit 340. The selection circuit 310 is activated when the fuse set 100 is selected, and the corresponding bit signals DATA1 to DATAm, the enable signal E, and the disable signal D are input thereto. The latch circuit 320 is a circuit that temporarily holds data to be written to the antifuse element 330.

  The bit signals B1 to Bm, which are the outputs of the sense circuit 340, indicate one defective address. If the enable signal Ea is active, the defective address is valid, and if the disable signal Da is active, the defective address. Is invalid. Thus, the output 100a from one fuse set 100 is composed of the bit signals B1 to Bm, the enable signal Ea, and the disable signal Da. As shown in FIG. 2, a set of these outputs 100a is a defective address RADD.

  FIG. 4 is a specific circuit diagram of the bit storage circuit 210.

  As shown in FIG. 4, the selection circuit 310 included in the bit storage circuit 210 has a transfer gate configuration in which an N-channel MOS transistor 311 and a P-channel MOS transistor 312 are connected in parallel. A corresponding selection signal SEL and its inverted signal are supplied to the gates of the transistors 311 and 312. The selection signal SEL is a signal for selecting a desired fuse set 100. Therefore, a different selection signal SEL is assigned to each fuse set 100. With this configuration, when the selection signal SEL is activated to a high level, the corresponding bit signal DATAi (i = 1 to m) is supplied to the latch circuit 320.

  The latch circuit 320 has a so-called flip-flop configuration in which two inverters 321 and 322 are circularly connected. Therefore, when the selection signal SEL is activated, the bit signal DATAi is temporarily stored in the latch circuit 320. Needless to say, writing to the latch circuit 320 can be performed at a very high speed, unlike writing to the antifuse element. As shown in FIG. 4, the operating voltage VPPSV generated by the mode determination circuit 120 is supplied to the latch circuit 320.

  The output of the latch circuit 320 is supplied to the antifuse element 330 through the write transistor 301. The antifuse element 330 has a configuration in which the source and drain of a MOS transistor are short-circuited, the output of the latch circuit 320 is supplied to the gate 331, and the mode determination circuit 120 generates the source / drain 332. Operating voltage VBBSV is supplied.

  In the anti-fuse element 330 in the initial state, the gate 331 and the source / drain 332 are insulated via a gate insulating film. For this reason, no current flows between the two. However, when a high voltage is applied between the gate 331 and the source / drain 332, dielectric breakdown occurs in the gate insulating film, and a current path is formed between the two. After the dielectric breakdown of the gate insulating film, it cannot be restored, so that irreversible nonvolatile writing becomes possible. The gate 331 of the antifuse element 330 is connected to the sense circuit 340 via the read transistor 302.

  Here, the transistors included in the selection circuit 310 and the latch circuit 320 and the transistors 301 and 302 illustrated in FIGS. 4A and 4B each have a breakdown voltage structure with a thicker gate insulating film than the other transistors. On the other hand, the transistor constituting the antifuse element 330 is a normal transistor constituting the sense circuit 340 and other internal circuits, and the thickness of the gate insulating film is set thin. This is to prevent the selection circuit 310 and the latch circuit 320 from breaking down when the antifuse element 330 is broken down. When the gate insulating film is thickened, the capability as a transistor is reduced, but even if the operation speed of the selection circuit 310, the latch circuit 320, etc. is slightly reduced, there is almost no practical problem.

  Like the latch circuit 320, the sense circuit 340 has a so-called flip-flop configuration in which an inverter made up of transistors 341 and 342 and an inverter made up of transistors 343 and 344 are connected in a circulating manner. A sense signal CSN is supplied to the sources of the transistors 342 and 344. The sense signal CSN is set to the VDD level during the period for reading the state of the antifuse element 330, and is set to the VSS level when performing the sensing operation. The node a connected to the gates of the transistors 341 and 342 is connected to the gate 331 of the antifuse element 330 via the read transistor 302 and is used as an output terminal of the bit storage circuit 210. Instead of the node a, the node b connected to the gates of the transistors 343 and 344 may be used as the output terminal.

The nodes a and b are supplied with the power supply voltage VDD and the reference voltage Vref through transistors 345 and 346, respectively. The transistors 345 and 346 are turned on when the precharge signal PRE is activated to a low level, and precharge the nodes a and b to the power supply voltage VDD and the reference voltage Vref, respectively. The relationship between the power supply voltage VDD and the reference voltage Vref is
VDD> Vref
Therefore, the bit output Bi (i = 1 to m) immediately after the precharge is at the high level (1).

  When the read transistor 302 is turned on after completing the precharge, the node a is connected to the antifuse element 330. At this time, the sense signal CSN is set to the VDD level. When the node a is connected to the antifuse element 330, the level of the node a changes according to the state of the antifuse element 330. That is, when the anti-fuse element 330 is broken down, a current flows from the node a to the anti-fuse element 330. Therefore, the potential of the node a is lowered, and the bit signal is output by changing the sense signal CSN to the VSS level. Bi is inverted to a low level (0). On the other hand, when the anti-fuse element 330 is not broken down, the potential of the node a is kept at VDD, so that the bit output Bi remains at the high level (1) even if the sense signal CSN is changed to the VSS level. Hold. In this way, the sense circuit 340 can read the information written in the antifuse element 330.

  The enable circuit 220 and the disable circuit 230 are also supplied with the enable signal E and the disable signal D instead of the bit signal DATAi, and output the enable signal Ea and the disable signal Da, respectively. The memory circuit 210 has the same circuit configuration.

  The above is the configuration of the semiconductor device according to the present embodiment. Next, the operation of the semiconductor device according to the present embodiment will be described focusing on the antifuse circuit 31.

  The operation of the antifuse circuit 31 is largely divided into a set operation for temporarily latching the defective address, a write operation for writing the latched defective address into the antifuse element, and a sense operation for reading out the defective address written in the antifuse element. Separated. These operations are performed by entering the “set mode”, “write mode”, and “sense mode” described above, respectively.

  The set operation and the write operation are included in a series of test processes performed in the wafer state.

  FIG. 5 is a flowchart showing a rough flow of the test process.

  The test process is performed using a tester (not shown). As shown in FIG. 5, first, defective data is detected, that is, an operation test is performed by actually writing and reading data (step S11). The defective address thus detected is temporarily stored in the tester.

  Next, the tester transfers the stored defective address to the semiconductor device 10 and causes the latch circuit 320 in the fuse set 100 to latch (step S12). At this time, the anti-fuse circuit 31 is entered in the “set mode” and performs a set operation. Next, the tester actually causes the defective address latched by the latch circuit 320 to be written in the antifuse element 330 (step S13). At this time, the antifuse circuit 31 is entered in the “write mode” and performs a write operation. Thereby, each of the plurality of defective addresses is stored in the fuse set 100 in a nonvolatile manner. Finally, a roll call test is performed on the antifuse circuit 31 (step S14). Details of the operations in steps S12 to S14 will be described later.

  Such a test process is performed in a wafer state at the time of manufacture. That is, it is executed in parallel for a plurality of semiconductor devices (chips). Specifically, as shown in FIG. 6, an operation test is performed in parallel on j × k semiconductor devices among the semiconductor devices included in the semiconductor wafer 400. The j × k semiconductor devices to be tested in parallel are called so-called DUT (Device Under Test). The number of DUTs depends on the configuration of the probe card 401 provided in the tester. For example, about 200 semiconductor devices are tested in parallel.

  The probe card 401 has a large number of probes for making contact with each terminal provided in the semiconductor device to be tested. As shown in FIG. 6, a probe 401a for supplying a clock signal CK The probe 401b for supplying the command signal CMD and the probe 401c for supplying the address signal ADD are commonly connected between the chips. This is because in an operation test for detecting a defective address, it is not necessary to supply individual clock signals CK, address signals ADD and command signals CMD to each chip, and these signals can be given to all chips in common. It is because it is good.

  On the other hand, since the input / output data DQ needs to be individual for each chip, the probe 401d for exchanging data DQ is not commonly connected but is individually connected for each chip.

  FIG. 7 is a flowchart for explaining the set operation (step S12).

  The set operation is an operation in which the detected defective address is transferred from the tester to the semiconductor device 10 and is latched by the latch circuit 320 in the fuse set 100. As described above, the test process is executed in parallel for a plurality of chips, and the address signal ADD is commonly applied to the plurality of chips. That is, the individual address signal ADD cannot be supplied to each chip. On the other hand, of course, the defective address is different for each chip.

  In order to solve such a problem, in this embodiment, the presence / absence of a defect is notified for each chip using the data terminal 23 while incrementing (or decrementing) the address signal ADD via the address terminal 22. This will be specifically described below.

  First, by applying 3V and 0V to the external terminals VPPS and VBBS, respectively, the antifuse circuits 31 of all the chips belonging to the same DUT are entered into the “set mode” (step S21). When entering the set mode, the mode determination circuit 120 sets the mode signals M1 and M2 to the high level, and in response to this, the control circuit 110 performs the operation in the set mode.

  After the control circuit 110 is entered into the set mode, the address signal ADD is set to the minimum value (= 0) on the tester side (step S22), and a “relief set address” is assigned to the chip whose address is a defective address. Supply (steps S23 and S24). The relief set address refers to the address of the fuse set 100 where the defective address is to be stored. Since the relief set address needs to be individual for each chip, the data DQ via the data terminal 23 is used to supply these signals.

  Upon receiving the relief set address, the control circuit 110 activates the corresponding selection signal SEL, thereby selecting a predetermined fuse set 100 (step S25). Thereby, the selection circuit 310 in the selected fuse set 100 becomes conductive. In this state, the bits DATA1 to DATAm of the defective address and the enable signal E are supplied to the fuse set 100 (step S26). At this time, the write transistor 301 is held in an off state. As a result, the bits DATA1 to DATAm of the defective address and the enable signal E are latched in the latch circuit 320 in the selected fuse set 100.

  Such an operation is performed for all addresses by incrementing the address signal ADD (step S28). When the address signal ADD reaches the maximum value (ADD = Max) and incrementing of all addresses is completed (step S27: YES), a series of set operations is completed. With the above operation, all defective addresses are latched in the fuse set 100. The enable signal E is latched in the enable circuit 220 of the fuse set 100 in which the defective address is latched.

  The time required for processing one address in the set operation, that is, the time required for the operation from step S23 to step S28 shown in FIG. 7 is on the order of nanoseconds. As an example, if the time required for processing one address is 14 ns and the total number of addresses is 34000 addresses, the time required to complete the set operation is about 0.48 s. That is, the set operation can be completed in 0.48 seconds for all chips belonging to the same DUT.

  FIG. 8 is a timing chart showing an example of changes in each signal during the set operation.

  In the example shown in FIG. 8, the address is incremented in two clock cycles. Specifically, the first half part (ADDa) of the address signal ADD is input in response to the first rising edge of the clock signal CK, and the second half part (ADDb) of the address signal ADD in response to the second rising edge. You are typing.

  On the other hand, for the relief set address, four terminals among the plurality of data terminals 23 are used, and bit DQ0 is used as an enable signal. The bit DQ0 is high active, and if the bit DQ0 is all at a high level during the two clock cycles of interest, the selection of the chip is valid, and the antifuse circuit 31 generates the enable signal E. On the other hand, the remaining 3 bits DQ1 to DQ3 are captured four times in total at both edges of the clock signal CK. A relief set address is designated by these four captures (AF1 to AF4). As described above, the repair set address specified by the bits DQ1 to DQ3 is used for selecting the fuse set 100.

  FIG. 9 is a table showing an example of changes in each signal during the set operation.

  In the example shown in FIG. 9, both the first half part ADDa and the second half part ADDb of the address signal ADD are 10 bits. A row address (or column address) is specified by 13 bits consisting of 10 bits (A0 to A9) of the first half part ADDa inputted first time and 3 bits (A0 to A2) of the second half part ADDb inputted second time. The bank address is designated by 2 bits consisting of bits A4 and A5 of the latter half portion ADDb. Bit A3 of the latter half portion ADDb is an enable bit, and is always set to high level (1) during the set operation. The remaining bits A6 to A9 are not used. These address signals ADD are given in common to all chips belonging to the same DUT.

  As described above, the repair set address corresponding to each address is different for each chip, and if the enable bit DQ0 is at a high level (1), the other bits DQ1 to DQ3 are valid. In the example shown in FIG. 9, chip # 0 is enabled at addresses # 2 and # 5, and chip # 1 is enabled at address # 4.

  As described above, according to the setting operation according to the present embodiment, an arbitrary defective address can be set in parallel to each chip.

  FIG. 10 is a flowchart for explaining the write operation (step S13). The write operation is an operation for writing the defective address temporarily latched in the latch circuit 320 into the antifuse element 330.

  First, by applying 4 V and −2 V to the external terminals VPPS and VBBS, respectively, the antifuse circuits 31 of all the chips belonging to the same DUT are entered into the “write mode” (step S31). When entering the write mode, the mode determination circuit 120 sets the mode signal M1 to the high level and the mode signal M2 to the low level, and in response to this, the control circuit 110 performs the operation in the write mode.

  The tester causes the control circuit 110 to enter the write mode, and then periodically changes the clock signal CK as shown in FIG. If the write mode is entered, the control circuit 110 increments the internal counter 111 in synchronization with the clock signal CK. The count values C of the internal counter 111 indicate the corresponding fuse sets 100, and therefore, a different fuse set 100 is selected every time the count value C changes. The count value C is set to 0 as an initial value (step S32).

  The control circuit 110 supplies the write signal SELBRK to the fuse set 100 selected by the count value C while the clock signal CK is at a high level (step S33). Accordingly, the write transistor 301 is turned on while the clock signal CK is at a high level. At this time, the read transistor 302 is held in an off state.

  During the write operation, the voltage VBBSV (−2 V) is supplied to the source / drain 332 of the antifuse element 330. For this reason, when the write transistor 301 is turned on, among the anti-fuse elements 330 included in the fuse set 100, those having a high level (1) latched in the corresponding latch circuit 320 have a voltage of 6V ( = 4V + 2V) is applied. As a result, the antifuse element 330 is dielectrically broken and irreversibly transitions from the non-conductive state to the conductive state. On the other hand, among the antifuse elements 330 included in the fuse set 100, only the voltage of 2V (= 0V + 2V) is applied to the gate insulating film of the corresponding latch circuit 320 whose low level (0) is latched. Therefore, the gate insulating film is not broken. That is, the antifuse element 330 is kept in a non-conductive state.

  As a result, the defective address temporarily stored using the latch circuit 320 is recorded in the antifuse element 330 in a nonvolatile manner. Writing to the antifuse element 330 requires a longer time (for example, 5 ms) than writing to the latch circuit 320.

  Such an operation is performed on all the fuse sets 100 by incrementing the internal counter 111 in synchronization with the clock signal CK (step S35). When the count value C of the internal counter 111 becomes the maximum value and the writing process for all the fuse sets 100 is completed (step S34: YES), a series of writing operations is completed. Therefore, if the number of fuse sets 100 included in the anti-fuse circuit 31 is 1000, for example, the write operation for all the chips belonging to the same DUT is completed in about 5 seconds (= 5 ms × 1000).

  Here, the write operation is performed for each fuse set 100 because the amount of current that can be supplied by the tester is limited. Therefore, if the amount of current that can be supplied by the tester is large to some extent, the write operation may be performed simultaneously on a plurality of fuse sets 100 included in one chip. According to this, it becomes possible to complete a series of write operations at higher speed.

  FIG. 12 is a flowchart for explaining the roll call test (step S14). The roll call test is a test for determining whether or not a defective address is correctly written in each fuse set 100.

  First, by setting the external terminals VPPS and VBBS to an open state, the antifuse circuits 31 of all the chips belonging to the same DUT are entered in the “sense mode” (step S41). When entering the sense mode, the mode determination circuit 120 sets the mode signal M1 to the low level and the mode signal M2 to the high level, and in response to this, the control circuit 110 performs the operation in the sense mode.

  After entering the control circuit 110 into the sense mode, the tester supplies a reset signal RESET to each chip as shown in FIG. 13 (step S42). The reset signal RESET is a predetermined combination of the command signal CMD and is therefore supplied to the command terminal 21.

  When the reset signal RESET is supplied during entry to the sense mode, the control circuit 110 increments the internal counter 112 in synchronization with the clock signal CK. The count value C1 of the internal counter 112 is set to 0 as an initial value (step S43).

  The count value C1 of the internal counter 112 points to a plurality of fuse sets 100, and therefore, a plurality of different fuse sets 100 are selected every time the count value C1 changes. The number of fuse sets 100 selected by one count value C1 is not particularly limited, and can be about 32 sets, for example. If the number of fuse sets 100 selected by one count value C1 is set to a power of 2, it is not necessary to separately provide the internal counter 112, and it is sufficient to use the upper bits of the internal counter 111.

Next, the control circuit 110 sets the precharge signal PRE to a low level for a predetermined period, and precharges the sense circuit 340 (step S44). As described above, the relationship between the power supply voltage VDD and the reference voltage Vref is
VDD> Vref
Therefore, the bit output Bi (i = 1 to m) and the enable signal Ea in the state immediately after the precharge are at the high level (1).

  After the precharge is completed, the control circuit 110 supplies the sense signal SELBSA to the plurality of fuse sets 100 selected by the count value C1 (step S45). As a result, the read transistor 302 in the selected fuse set 100 is turned on, and the node a of the sense circuit 340 is connected to the antifuse element 330. At this time, the writing transistor 301 is held in an off state.

  As a result, when the antifuse element 330 is broken down, a current flows from the node a to the antifuse element 330. Therefore, the potential of the node a is lowered, and the bit output Bi and the enable signal Ea are at a low level (0). ). On the other hand, when the anti-fuse element 330 is not broken down, the potential of the node a is kept at VDD, so that the bit output Bi and the enable signal Ea hold high level (1).

  As described above, the defective address and the enable signal Ea written in the plurality of selected fuse sets 100 are read. Such an operation is performed on all the fuse sets 100 by incrementing the internal counter 112 in synchronization with the clock signal CK (step S47). When the count value C1 of the internal counter 112 reaches the maximum value and the sensing operation for all the fuse sets 100 is completed (step S46: YES), a series of sensing operations is completed.

  The defective address read in this way is supplied to a tester (not shown) and compared with the defective address detected in the operation test (step S11). As a result, if both are the same (step S48: YES), the roll call test is terminated. On the other hand, if at least some of the addresses do not match (step S48: NO), the antifuse element 330 is insufficiently destroyed, and rewriting is executed for the same fuse set 100 (step S49). ).

  Then, the roll call is performed again and compared with the defective address stored in the tester. As a result, if both of them coincide with each other due to the success of rewriting (step S50: YES), the roll call test is terminated. On the other hand, if even one inconsistent address remains (step S50: NO), the writing to the fuse set 100 is abandoned and the writing to the antifuse element 330 included in the disable circuit 230 is performed. (Step S51). Thereby, the fuse set 100 is invalidated.

  Next, the defective address to be written in the invalidated fuse set 100 is written in another fuse set 100 in an unused state (step S52). Then, the roll call is performed again and compared with the defective address stored in the tester. As a result, if the alternative writing is successful and both match (step S53: YES), the roll call test is terminated. On the other hand, if even one unmatched address remains (step S53: NO), the chip is handled as a defective product (step S54).

  As described above, in this embodiment, since the disable circuit 230 for disabling is provided in addition to the enable circuit 220 for enabling the fuse set 100, even if rewriting fails, the chip is immediately discarded. Instead, alternative writing to another fuse set 100 in an unused state is possible. Thereby, the yield of products can be improved.

  The above is the operation performed in a series of test steps.

  As described above, according to the present embodiment, since all defective addresses are latched in the set operation (step S12), the write operation (step S13) is actually performed on the antifuse element 330. Such a write operation can be performed on a plurality of chips in parallel. For this reason, it is possible to greatly shorten the time for writing to the antifuse element 330.

  In addition, in the set operation (step S12), the repair set address is supplied using the data DQ while incrementing the address signal ADD, so that different defective addresses can be set for individual chips. . Therefore, it is possible to use a normal probe card 401 to which a probe 401c for supplying an address signal ADD is commonly connected.

  Further, the fuse set 100 in which a write failure is found in the roll call test (step S14) can be disabled afterwards by activating the disable circuit 230. As a result, alternative writing to the unused fuse set 100 becomes possible, so that the yield of products can be improved.

  As described above, in the actual use state, the external terminals VPPS and VBBS are in an open state, so that the sense mode is always set. Therefore, when the reset signal RESET is issued when the power is turned on or reset, the processing in steps S43 to S47 shown in FIG. 12 is executed, and the defective address RADD written in each fuse set 100 is read. The read defective address RADD is supplied to the address comparison circuit 32 shown in FIG. 1, and the defective normal cell 11a is replaced with the redundant cell 11b under the control of the address comparison circuit 32 and the access circuit 12. . Thereby, the defective address is relieved.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. Needless to say, it is included in the range.

  For example, in the above embodiment, after all defective addresses are latched in the set operation (step S12), the write operation (step S13) is actually performed on the antifuse element 330. However, the present invention is not limited to this. Is not to be done. Therefore, the latch circuit 320 may be omitted, and the writing to the antifuse element 330 may actually be performed during the above-described set operation.

  In the above embodiment, the relief set address is supplied using the data DQ while incrementing the address signal ADD. However, the present invention is not limited to this. Therefore, the defective address and the relief set address may be supplied by another method.

  Furthermore, in the above-described embodiment, a gate breakdown type antifuse element having the same configuration as that of the MOS transistor is used as the antifuse element 330, but the specific configuration of the antifuse element is not particularly limited in the present invention. Therefore, for example, a capacitance destruction type antifuse element having the same configuration as a DRAM cell capacitor may be used.

1 is a block diagram showing a configuration of a semiconductor device 10 according to a preferred embodiment of the present invention. 3 is a block diagram showing a circuit configuration of an antifuse circuit 31. FIG. 2 is a block diagram showing a circuit configuration of a fuse set 100. FIG. 3 is a specific circuit diagram of a bit storage circuit 210. FIG. It is a flowchart which shows the rough flow of a test process. It is a figure which shows the semiconductor wafer 400 and the probe card 401 which tests this. It is a flowchart for demonstrating a setting operation | movement (step S12). It is a timing chart showing an example of change of each signal at the time of a set operation. It is a table | surface which shows an example of the change of each signal at the time of a setting operation | movement. It is a flowchart for demonstrating write-in operation | movement (step S13). FIG. 6 is a timing chart showing changes in count value C. It is a flowchart for demonstrating a roll call test (step S14). It is a timing chart showing change of count value C1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor device 11 Memory cell array 11a Normal cell 11b Redundant cell 12 Access circuit 13 Input / output circuit 14 Command decoder 21 Command terminal 22 Address terminal 23 Data terminal 24 Clock terminal 31 Antifuse circuit 32 Address comparison circuit 100 Fuse set 110 Control circuit 111, 112 Internal counter 120 Mode determination circuit 210 Bit storage circuit 220 Enable circuit 230 Disable circuit 310 Select circuit 320 Latch circuit 330 Antifuse element 340 Sense circuit 400 Semiconductor wafer 401 Probe cards 401a to 401d Probe

Claims (8)

  A plurality of fuse sets including an anti-fuse element that holds data in a nonvolatile manner is provided. The fuse set invalidates defective addresses stored in the plurality of bit storage circuits and a plurality of bit storage circuits that store defective addresses. An anti-fuse circuit including the disable circuit.   2. The antifuse circuit according to claim 1, wherein the fuse set further includes an enable circuit that validates a defective address stored in the plurality of bit storage circuits.   3. The antifuse circuit according to claim 2, wherein each of the enable circuit and the disable circuit has substantially the same circuit configuration as the bit storage circuit.   And a control circuit for activating the enable circuit in the fuse set to which the defective address is to be written, and activating the disable circuit in the fuse set in which the writing of the defective address has failed. Item 6. The antifuse circuit according to Item 3.   5. An antifuse circuit according to claim 1, an address terminal to which the defective address is supplied, and a data terminal to which a repair set address for selecting the fuse set is provided. A semiconductor device characterized by the above. A method for writing a defective address in the antifuse circuit according to claim 4,
A first step of activating the enable circuit in the fuse set to which the defective address is to be written;
And a second step of activating the disabling circuit in the fuse set when the writing of the defective address fails. A method of writing an address to an antifuse circuit, comprising:   7. The method of writing an address into the antifuse circuit according to claim 6, further comprising a third step of writing a defective address to be written in the fuse set in which the disable circuit is activated into another fuse set. .   8. The method according to claim 6, wherein the first step includes a step of writing the defective address, and a step of rewriting the defective address when the writing of the defective address fails. 9. Address write method to antifuse circuit.

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