Semiconductor memory device having flexible column redundancy scheme

This U.S. nonprovisional patent application claims priority under 35 U.S.C. § 119 of Korean Patent Application 2003-34119 filed on May 28, 2003, the entire contents of which are hereby incorporated by reference.

A NAND flash memory device, which is one example of a non-volatile semiconductor memory device, includes a page buffer circuit for performing various functions. For example, in reading data from memory cells of a selected page, the page buffer circuit senses data of the selected page and latches the sensed page data. In addition, when data are programmed in memory cells of the selected page, the page buffer circuit temporarily stores program data supplied from outside. The page buffer circuit is capable of preventing a program-inhibited cell or a program-completed cell from being programmed. Examples of the page buffer performing functions mentioned above are disclosed in U.S. Pat. No. 5,790,458 entitled “SENSE AMPLIFIER FOR NONVOLATILE SEMICONDUCTOR MEMORY DEVICE,” U.S. Pat. No. 5,761,132 entitled “INTEGRATED CIRCUIT MEMORY DEVICE WITH LATCH-FREE PAGE BUFFERS THEREIN FOR PREVENTING READ FAILURE” and U.S. Pat. No. 5,712,818 entitled “DATA LOADING CIRCUIT FOR PARTIAL PROGRAM OF NONVOLATILE SEMICONDUCTOR MEMORY”.

In performing a verification operation for confirming if programmed/erased cells have reached a target threshold voltage (if programmed/erased cells are sufficiently programmed/erased), the page buffer circuit, in the same way as a sensing operation, senses/latches data bits from memory cells of the selected page. To decide whether the latched data bits are pass data bits, the page buffer circuit provides the latched data bits to a program-status detecting circuit (also referred to as “a pass/fail check circuit”) without otherwise outputting the data from the page buffer. A NAND flash memory device having the program-status detecting circuit is disclosed in U.S. Pat. No. 5,299,162 entitled “SEMICONDUCTOR MEMORY DEVICE AND AN OPTIMIZING PROGRAMMING METHOD THEREOF.”

The program-status detecting circuit PS, which is disclosed in U.S. Pat. No. 5,299,162, includes pull-down transistors PD1–PD1024 connected to latches LT of page buffers PB, respectively. The pull-down transistors PD1–PD1024 are controlled by inversion outputs /Q of corresponding latches LT. Program/erase verification is carried out repeatedly until all pull-down transistors PD1–PD1024 are turned off.

After repeatedly performing the program/erase operation, a determination is made by the program status detection circuit whether all memory cells have been normally programmed/erased. Even after program/erase verification is carried out upon all effected memory cells, results of the pass/fail check circuit can indicate a program/erase failure. Such a program/erase failure may be generated, for example, by a defective memory cell. If the program/erase failure is caused by the defective memory cell, then the defective memory cell(s) is (are) substituted for redundant cell(s) in a known manner. After such substitution, a program/erase failure should not be indicated unless there was some additional cause of the failure.

At least one embodiment of the present invention provides a semiconductor memory device having a flexible column redundancy scheme that, e.g., can repair a defective page buffer without having to declare the corresponding column defective and/or can prevent a verification failure due to the defective page buffer.

At least one other embodiment of the present invention provides a flash memory device comprising: a plurality of main bit lines; a plurality of redundant bit lines; a plurality of first page buffers respectively organized as a plurality of first page buffer groups which are connected to main bit lines; a plurality of second page buffers respectively organized as a plurality of second page buffer groups which are connected to the redundant bit lines; each of the first and second page buffers including an output P/F terminal to provide pass/fail data; a plurality of fuses corresponding to the pluralities of the first and second page buffer groups, respectively, each of the fuses having one end commonly connected to the P/F terminals in a corresponding page buffer group and the other end connected to a signal line; and a pass/fail check circuit to determine an overall pass/fail signal based upon a signal on the signal line.

Additional features and advantages of the invention will be more fully apparent from the following detailed description of example embodiments, the accompanying drawings and the associated claims.

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:

FIG. 1 is a block diagram showing a flash memory device according to at least one embodiment of the present invention;

FIG. 2 is a circuit diagram for any one of page buffer circuits 110 M and 110 R in FIG. 1 , according to at least one embodiment of the present invention;

FIG. 3 shows a fuse circuit and the page buffer circuits in FIG. 1 , according to at least one embodiment of the present invention;

FIG. 4 is a circuit diagram for a pass/fail check circuit in FIG. 1 in accordance with at least one embodiment of the present invention;

FIG. 5 is a timing diagram illustrating operation of the pass/fail check circuit in FIG. 4 ;

FIG. 6 is a circuit diagram for a column gate circuit 120 R in FIG. 1 , in accordance with at least one embodiment of the present invention;

FIG. 7 is a block diagram showing an address storage circuit and a redundant column decoder circuit, in accordance with at least one embodiment of the present invention;

FIG. 8 is a circuit diagram for an address storage block 160 A and the redundant decoder circuit 170 B, according to at least one embodiment of the present invention;

FIG. 9 is a circuit diagram showing any one of the fuse boxes in FIG. 8 , in accordance with at least one embodiment of the present invention;

FIG. 10 is a circuit diagram for showing the address storage block 160 B and the redundant decoder 170 B in FIG. 7 , in accordance with at least one embodiment of the present invention;

FIG. 11 is a block diagram showing a multiplexer circuit 159 in FIG. 1 , in accordance with at least one embodiment of the present invention;

FIG. 12 is a block diagram showing an input/output control circuit in FIG. 1 , in accordance with at least one embodiment of the present invention;

FIG. 13 is a circuit diagram for any one of the fuse boxes in FIG. 12 , in accordance with at least one embodiment of the present invention;

FIG. 14 is a circuit diagram showing any one of decoders in FIG. 12 , in accordance with at least one embodiment of the present invention;

FIG. 15 is a flowchart illustrating repair operation of the flash memory device, in accordance with at least one embodiment of the present invention.

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. However, the present invention is not limited to the embodiments illustrated herein after, and the embodiments herein are rather introduced to provide easy and complete understanding of the scope and spirit of the present invention.

In developing embodiments of the present invention, the following problem with the Background Art was recognized, the physics thereof determined, and the problem overcome. The program-status detecting circuit of U.S. Pat. No. 5,299,162 can exhibit a program/erase failure also because of a defective page buffer. If the page buffer is defective, at least one of pull-down transistors PD1–PD1024 of the program-status detecting circuit is turned on continuously. As a result, the output of the program-status detecting circuit will continuously exhibit the program/erase failure. This makes it difficult, e.g., in a situation where a defective memory cell has also caused the program/erase failure, to use absence of a program/erase failure as a confirmation that the defective memory cell has been replaced. At least one embodiment of the present invention solves such a problem by providing a semiconductor memory device which has a flexible column redundancy scheme that, e.g., can isolate a defective page buffer without having to declare the corresponding column defective.

FIG. 1 is a block diagram showing a flash memory device 100 , according to at least one embodiment of the present invention.

Referring to FIG. 1 , the flash memory device 100 includes an array comprising a main cell array 100 M and a redundant cell array 100 R. The main cell array 100 M includes main columns (main bit lines), e.g., corresponding to a plurality of NAND strings (as is known), respectively. Each NAND string can include a string selection transistor, a ground selection transistor and main cells connected in series between the string selection transistor and the ground transistor. The redundant cell array 100 R provides redundant columns that can be substituted for defective columns of the main cell array 100 M and can include NAND strings respectively corresponding to redundant columns (redundant bit lines). It is to be understood that the columns of the redundant cell array 100 R can be constituted of the same (or substantially the same) circuitry as those of the main cell array 100 M. In effect, the redundant cell array 100 R can make it seem as though a defective column has been repaired.

A page buffer circuit 110 M senses data from the main cell array 100 M through the main bit lines in a read operation. In addition, the page buffer circuit 110 M drives the main bit lines to a level of a power supply voltage or a ground voltage depending on a program/erase operation. The page buffer circuit 110 M includes a plurality of page buffers (not shown in FIG. 1 but see other figures) connected to the main bit lines respectively, and the page buffers are divided into a plurality of groups. A column gate circuit (referred to as “Y-Gate”) 120 M responds to selection signals from a main column decoder circuit 140 to sequentially select page buffers of the page buffer circuit 110 M at a bite/word level of resolution within the circuit 110 M. In a read operation, bite/word data of the selected page buffers are transferred through a multiplexer circuit 150 to data lines DLk. In a program operation, bite/word data that will be programmed on data lines DLk are loaded through the multiplexer circuit 150 and the column gate circuit 120 M into the selected page buffers.

An address XA applied from the outside is loaded in a counter circuit 130 . To select page buffers at the bite/word unit level, the counter circuit 130 sequentially increases loaded address to generate an internal address ADD — int. The main column decoder circuit 140 responds to the internal address ADD — int from the counter circuit 130 to generate selection signals. In a normal operation mode, the counter circuit 130 generates the internal address ADD — int to sequentially select main columns (page buffers of the page buffer circuit 110 M) of the main cell array 100 M. In test (also known as scan) operation mode, the data of all page buffers of page buffer circuits 110 M and 110 R are output for inspection, e.g., by a pass/fail check circuit 210 . As is known, a scan flag signal can be used to indicate the test mode. When a scan flag signal FY — SCAN is activated, the counter circuit 130 generates the internal address ADD — int to sequentially select main columns (page buffers of the page buffer circuit 110 M) of the main cell array 100 M as well as redundant columns (page buffers of the page buffer circuit 110 R) of the redundant cell array 100 R.

Similarly, referring to FIG. 1 , the page buffer circuit 110 R senses data from the redundant cell array 100 R through redundant bit line(s) in a read operation. In addition, the page buffer circuit 110 R drives redundant bit line(s) to a level of the power supply voltage or the ground voltage depending on a program/erase operation. The page buffer circuit 110 R includes a plurality of page buffers (not shown in FIG. 1 but see other figures) respectively connected to redundant bit lines. The column gate circuit (referred to as “Y-Gate”) 120 R responds to selection signals from a switch circuit 180 to select a page buffer of the page buffer circuit 110 R. In a reading operation, instead of data of the defective column in the page buffer circuit 110 M, data of the corresponding selected page buffer in page buffer circuit 110 R is transferred through the multiplexer circuit 150 to the data line DLk. In a program operation, data to be programmed corresponding to the defective column in the page buffer circuit 110 M is loaded through the multiplexer circuit 150 and the column gate circuit 120 R into the corresponding selected page buffer in the page buffer circuit 110 R.

The multiplexer circuit 150 operates responsive to an output from an input/output control circuit 220 . For example, when an applied address (an output address of the counter circuit) is an address of a defective column in the page buffer circuit 110 M, the multiplexer circuit 150 selects a corresponding replacement column in the page buffer circuit 110 R via the column gate circuit 120 R rather than the defective column of the page buffer circuit 110 R via the column gate circuit 120 M. To the contrary, when the applied address is not an address of a defective column, the multiplexer circuit 150 selects desired ones among the outputs of the column gate circuit 120 M and connects them to the corresponding data lines.

An address storage circuit 160 stores address(s) of (or, in other words pointers to) main column(s) in the page buffer circuit 110 M. Furthermore, the address storage circuit 160 stores address(s) for pointing to the page buffer group that includes a defective page buffer. This will be more fully described later. A redundant column decoder circuit 170 responds to the output of the address storage circuit 160 and the internal address ADD — int to generate selection signals. The selection signals from the redundant column decoder 170 are transferred through the switch circuit 180 to the column gate circuit 120 R. A test decoder circuit 190 operates responsive to the scan flag signal FY — SCAN, and generates selection signals by decoding the internal address ADD — int.

The selection signals from the test decoder circuit 190 are transferred through the switch circuit 180 to the column gate circuit 120 R. The switch circuit 180 operates responsively to the scan flag signal FY — SCAN. For example, when the scan flag signal FY — SCAN is activated, the switch circuit 180 transfers an output of the redundant column decoder circuit 170 to the column gate circuit 120 R. When the scan flag signal FY — SCAN is activated, the switch circuit 180 transfers an output of the test decoder circuit 190 to the column gate circuit 120 R.

As shown in FIG. 1 , the flash memory device 100 further includes a fuse box 200 and a pass/fail check circuit 210 . The fuse box 200 transfers pass/fail data outputted from page buffer groups of the page buffer circuit 110 M and 110 R to the pass/fail check circuit 210 . The pass/fail check circuit 210 decides whether or not a current program/erase operation has been normally carried out according to inputted data. If at least one of the page buffers in a page buffer group is defective, the fuse box 200 can electrically isolate the page buffer group that includes the defective page buffer from the pass/fail check circuit 210 . This will be more fully described later.

FIG. 2 is a circuit diagram showing any one of the page buffers of the page buffer circuits 110 M and 110 R shown in FIG. 1 , according to at least one embodiment of the present invention.

In FIG. 2 , a page buffer PB is illustrated which is connected to only one main/redundant bit line, respectively, but the other page buffers connected to the respective other main/redundant bit lines may be constituted of the same (or substantially the same) circuitry as that shown in FIG. 2 . Referring to FIG. 2 , the page buffer PB includes three PMOS transistors M 1 , M 2 and M 7 , four NMOS transistors M 3 , M 4 , M 5 and M 6 , and a latch LAT 1 comprising invertors INV 1 and INV 2 , which can be connected as shown in FIG. 2 . A bit line BLi (or, in other words, an i th column) of the main call array 100 R or redundant call array 100 R is connected to the transistors M 1 and M 5 . The operation of page buffers is generally known. Hence, further description of the page buffer BP is kept brief.

Referring to FIG. 2 , during operation of the page buffer BP, the PMOS transistor M 7 selectively charges a signal line segment nWDk with a power supply voltage according to a logic level of a node ND 1 of the latch LAT 1 . The signal line segment nWDk is precharged through the pass/fail check circuit 210 in FIG. 1 to a ground voltage level. A logic low level on the signal line segment nWDk indicates that a memory cell connected to the page buffer PB has been normally programmed/erased. To the contrary, a logic high level on the signal line segment nWDk exhibits that the memory cell connected to the page buffer PB has not been sufficiently programmed/erased.

FIG. 3 is a more detailed block diagram of the fuse circuit 200 and the page buffer circuits 100 M and 100 R of FIG. 1 , according to at least one embodiment of the present invention.

Referring to FIG. 3 , the page buffer circuit 110 M includes a plurality of page buffer groups PBG 0 -PBGi. Each page buffer group PBG 0 –PBGi, for example, can have eight page buffers PB. As shown in FIG. 3 , one page buffer can be arranged (or laid out) within the width of eight bit lines. For this reason, eight page buffers PB should be arranged perpendicularly to a bit line direction. PMOS transistors M 7 of the page buffers PB in each page buffer group PBGk are commonly connected to a corresponding signal line segment nWDk, and the signal line segment nWDk is electrically connected through a corresponding fuse Fk to the signal line PB — nWD. For example, PMOS transistors M 7 of the page buffers PB of a page buffer group PBG 0 are commonly connected to the signal line segment nWD 0 , which is connected through a fuse F 0 to the signal line PB — nWD.

Similarly, referring to FIG. 3 , the page buffer circuit 110 R includes a plurality of page buffer groups RPBG 0 –RPBGj. Each page buffer group RPBGi, for example, can have eight page buffers PB. One page buffer can be arranged within the width of eight bit lines, and so eight page buffers PB should be arranged perpendicularly to a bit line direction. PMOS transistors M 7 of the page buffers PB in each page buffer group RPBGk are commonly connected to a corresponding signal line segment nWDk, which is electrically connected through a corresponding fuse Fk to the signal line PB — nWD. For example, PMOS transistors M 7 in page buffers PB of a page buffer group RPBG 0 are commonly connected to the signal line segment nWDi+1, which is connected through a fuse Fi+1 to the signal line PB — nWD.

In FIG. 3 , fuses −F 0 –Fi+j are included as parts of the fuse circuit 200 . For example, each fuse Fk may be a laser fuse.

If any main column of the main cell array 100 M is determined to be defective, then a redundant column of the redundant cell array 100 R may be substituted for it, which will be more fully described later. If a page buffer PB in any page buffer group PBGK is determined to be defective, the page buffer group PBGK that includes the defective page buffer PB may be electrically separated from the signal line PB — nWD by cutting (or, in other words, destroying) a corresponding fuse. For example, if a defective page buffer exists in the page buffer group PBG 0 , a fuse F 0 corresponding to the page buffer group PBG 0 can be cut. Once the fuse Fk is cut, the respective page buffer group PBGK is rendered completely irrelevant to a program/erase verify operation. In other words, the defective page buffer group PBGK will have no influence upon the results of the pass/fail check circuit 210 once the fuse Fk has been cut. The defective page buffer group PBGK may be substituted with a page buffer group of the redundant cell array 100 R, which will be described more fully later.

FIG. 4 is a circuit diagram showing in more detail the pass/fail check circuit 210 of FIG. 1 , according to at least one embodiment of the present invention. FIG. 5 is a timing diagram illustrating an operation of the pass/fail check circuit 210 of FIG. 4 .

As shown in FIG. 4 , the pass/fail check circuit 210 includes a tri-state inverter INV 3 , NMOS transistors M 9 and M 10 and inverters INV 4 –INV 7 , which can be connected as shown in FIG. 4 . Inverters INV 4 –INV 5 are included as parts of a latch LAT 2 . In FIG. 5 , when a control signal INT — PPWRRUP is activated in a pulse shape, a signal (not show in FIG. 5 ) on an output node ND 2 of the latch LAT 2 is initialized to a logic high level. When the control signal is activated, the signal line PB — nWD (from the fuse box 200 ) is set to a logic low level, e.g., at ground voltage, through the NMOS transistors M 9 . While a control signal WD 1 ch is activated high, a logic state of the signal line PB — nWD is latched to the latch LAT 2 . The latched signal may be outputted through the inverters INV 6 and INV 7 , where the output of the inverter INV 7 represents the scan flag signal FY — SCAN. When at the low level the scan flag signal FY — SCAN indicates that the present program/erase operation has been normally carried out (no failure). When at the high level the scan flag signal FY — SCAN indicates that the present program/erase operation has not been carried out normally (one or more causes of failure exist).

FIG. 6 is a circuit diagram of the column gate circuit 120 R of FIG. 1 , according to at least one embodiment of the present invention.

Referring to FIG. 6 , the column gate circuit 120 R is operated by responding to selection signals YCR — Lmn and YCR — Mx (in this embodiment, it is assumed for simplicity of illustration/discussion that m=0–3, n=0–1 and x=0–7; other values of m, n and x can be implemented) received via the switch circuit 180 of FIG. 1 , and includes a plurality of pass transistors M 15 –M 30 . The pass transistors M 15 –M 22 are included as parts of a column gate unit YG 0 , and pass transistors M 23 –M 30 are included as parts of a column gate unit YG 1 .

In FIG. 6 , again for simplicity of illustration/discussion, it is assumed that page buffer circuit 100 R has only two page buffer groups (though other numbers of such groups can be implemented), to which the column gate units YG 0 and YG 1 respectively correspond. Like the page buffer circuit 110 M, each page buffer group of the page buffer circuit 110 R, as previously mentioned, has eight page buffers PB respectively connected to eight bit lines. Drain terminals of the pass transistors M 15 –M 22 are connected to the corresponding page buffers PB, respectively. In addition, source terminals of the pass transistors M 15 –M 22 are commonly connected to a node ND 3 . The node ND 3 (and the signal thereon, referred to as redundant data RD) is connected in common to one input terminal of each multiplexer of a multiplexer circuit 150 , which will be more fully described hereinafter.

According to at least one embodiment of the present invention, when a main column is defective, redundant columns are substituted for the defective main column and a main column adjacent thereto. In other words, when one main column is defective, two main columns are replaced with redundant columns. Furthermore, a page buffer group that includes a defective page buffer (hereinafter inclusively referred to as a defective page buffer group), as previously mentioned, can be rendered completely irrelevant to the signal line PB — nWD. The defective page buffer group of the page buffer circuit 110 M is replaced with a corresponding page buffer group of the page buffer circuit 110 R. In other words, a flash memory device according to at least one embodiment of the present invention is capable of seeming to repair defective columns as well as the defective page buffer groups. In the Y-Gate circuit 120 R of FIG. 6 , the column gate unit YG 0 is available to substitute redundant columns for defective main columns, and the column gate unit YG 1 is available to substitute a redundant page buffer group for a defective page buffer group, as will be more fully described hereinafter.

If the circumstances of there being a defective main column arises, an address of the defective main column is stored in an address storage circuit 160 of FIG. 1 . At this time, redundant columns are substituted for the defective main column and a main column adjacent thereto. Any one of the substituted redundant columns is selected at a normal read/program operation. For example, if redundant columns having respective pass transistors M 15 and M 16 are used to substitute for defective main columns, only one of selection signals YCR — L 00 and YCR — L 01 is activated and the other is inactivated. Residual pairs of pass transistors M 17 and M 18 , M 19 and M 20 , and M 21 and M 22 may be controlled in the same way as the previously mentioned method. Therefore, if the defective page buffer group arises, a fuse connected to the defective page buffer group is cut. The address of the defective page buffer group is stored in the address storage circuit 160 of FIG. 1 . As a result, the defective page buffer group in the page buffer circuit 110 M is substituted for by a corresponding page buffer group in the page buffer circuit 120 R to support a read/program operation. Any one among the redundant columns of the substituted buffer group is selected through the column gate unit YG 1 . For example, in a normal read/program operation, only one of the selection signals YCR — MO–YCR — M 7 is activated, and the others are inactivated.

FIG. 7 is a block diagram showing in more detail the address storage circuit 160 and the redundant column decoder circuit 170 in FIG. 1 , according to at least one embodiment of the present invention.

Referring to FIG. 7 , the address storage circuit 160 includes two address storage blocks 160 A and 160 B, and the redundant column decoder 170 A includes two redundant column decoders 170 A and 170 B. The address storage block 160 A stores an address of a defective main column, and the address storage block 160 B stores an address of a defective page buffer group. If the address (A 1 –A 7 ) input to block 160 A is consistent with the address stored therein, then the address storage block 160 A activates any one of redundant enable signals RY — Li (in this embodiment, it is assumed for simplicity of illustration/discussion that i=0˜3; other values of i can be implemented). If the input address (A 3 –A 7 ) is consistent with the stored address, the address storage block 160 B activates the redundant enable signal RY — M. The redundant column decoder circuit 170 comprises two redundant column decoders 170 A and 170 B. The redundant column decoder 170 A receives the redundant enable signal RY — Li and the address signal A 0 . When any one of the redundant enable signals RY — Li is activated, the redundant column decoder 170 A activates any one of selection signals YCR — Lmn according to the address signal A 0 . The redundant column decoder 170 B receives the redundant column enable signal RY — M and address signals A 0 –A 2 . When the redundant enable signal RY — M is activated, the redundant column decoder 170 B activates any one of selection signals YCR — Mx according to address signals A 0 –A 2 .

FIG. 8 is a circuit diagram showing in more detail the address storage block 160 A and the redundant column decoder 170 A in FIG. 7 , according to at least one embodiment of the present invention. FIG. 9 is a circuit diagram for any one of fuse boxes 161 – 164 of FIG. 8 , according to at least one embodiment of the present invention.

Referring to FIG. 8 , the address storage block 160 A includes four fuse boxes 161 , 162 , 163 and 164 . Each fuse box 161 – 164 stores an address of a defective main column. Each fuse box 161 – 164 activates a corresponding redundant enable signal when the input address A 1 –A 7 is consistent with the address stored therein. As shown in FIG. 9 , the fuse box, e.g., 161 , comprises a plurality of transistors M 15 –M 24 , a plurality of fuses (e.g., laser fuses) F 10 –F 17 and an inverter INV 37 , which can be connected as shown in the FIG. The other fuse boxes 162 – 164 are constituted of the same (or substantially the same) circuitry as shown in FIG. 9 , and hence further description is omitted.

In this embodiment, since substitutions for two neighboring main columns are made using redundant columns simultaneously, only a 7-bit address needs to be stored in a fuse box. For this reason, fuses F 10 and F 11 related with a LSB address bit are not cut. If main columns are repaired by one column unit, an 8-bit address may be stored in a fuse box. In this case, fuses F 10 and F 11 related with an. LSB address bit A 0 also would be selectively cut.

To store an address of a defective main column, fuses F 10 and F 11 may be cut selectively to form a current path between a node ND 4 and the ground voltage. For example, if an address A 1 –A 7 of the defective main column is “1111111”, fuses F 13 , F 15 , . . . , F 17 that are related with complementary address signals nA 1 -nA 7 are cut, and fuses F 12 , F 14 , . . . , F 16 that related with address signals A 1 –A 7 are not cut. In this case, a current path between transistors M 15 and M 24 is formed only if an address of “1111111” is inputted. As a result, a flag signal RY — L 0 is activated high.

Referring to FIG. 8 again, the redundant column decoder 170 A includes a plurality of NAND gates (G 1 –G 8 ) and a plurality of inverters (INV 8 –INV 19 ), which can be connected as shown in FIG. 8 . The redundant column decoder 170 A responds to output signals RY — L 0 –RY — L 3 of the address storage block 160 A and the address signal A 0 to activate any one of selection signals YCR — L 00 –YCR — L 31 . For example, if the redundant enable signal RY — L 0 is activated and the address signal A 0 is “0”, the selection signal YCR — L 01 is activated. Resultantly, the pass transistor M 16 of the column gate unit YG 0 of FIG. 6 becomes turned on. When the redundant enable signal RY — L 0 is activated and the address signal A 0 is “1”, the selection signal YCR — L 00 is activated. Therefore, the pass transistor M 15 of the column gate unit TG 0 becomes turned on.

FIG. 10 is a circuit diagram for the address storage block 160 B and the redundant column decoder 170 B in FIG. 7 , according to at least one embodiment of the present invention.

Referring to FIG. 10 , the address storage block 160 B stores an address of the defective page buffer group. In addition, if the address A 3 –A 7 input to block 160 B is consistent with the address stored therein, then the address storage block 160 B activates the redundant enable signal RY — M. The address storage block 160 B can include the circuit arrangement shown in FIG. 9 , and stores a 5-bit address A 3 –A 7 . For this reason, fuses related with lower address signals A 0 –A 2 are not cut. If the page buffer is laid out within a width in which 16 bit lines are arranged, the address storage block 160 B stores a 4-bit address A 4 –A 7 , and fuses related with the lower address signals A 0 –A 3 are not cut irrespective of an address that will be stored.

The redundant column decoder 170 B includes AND gates G 9 –G 16 and inverters INV 22 –INV 24 , which can be connected as shown in FIG. 10 . When the redundant enable signal RY — M is activated and the address signals A 0 –A 2 are “000”, the output signal YCR — M 7 of the AND gate G 16 is activated. Therefore, the pass transistor M 30 of the column gate unit YG 1 of FIG. 6 becomes turned on. When the redundant enable signal RY — M is activated, and address signals A 0 –A 2 are “111”, the output signal YCR — MO of the AND gate G 9 is activated. Resultantly, the pass transistors M 23 of the column gate unit of FIG. 6 becomes turned on.

FIG. 11 is a block diagram showing the multiplexer circuit 150 of FIG. 1 , according to at least one embodiment of the present invention.

Referring to FIG. 11 , the multiplexer circuit 150 according to the present invention includes a plurality of multiplexers (e.g., eight multiplexers 151 , 152 , 153 , . . . , 158 ). Each multiplexer 151 – 158 has two input terminals, one selection terminal and one output terminal. Corresponding selection signals IOSLT 0 –IOSLT 7 are applied to the selection terminals of the multiplexers 151 – 158 , respectively. Corresponding main data MD 0 –MD 7 are supplied to first input terminals of the multiplexers 151 – 158 , and redundant data RD (which is the signal on node ND 3 , as noted above) is commonly supplied to second input terminals of the multiplexers 151 – 158 . When selection signals IOSLT 0 –IOSLY 7 have a low level, multiplexers 151 – 158 select the main data. When any one of selection signals IOSLT 0 –IOSLT 7 has a high level, a multiplexer that corresponds to the activated selection signal selects the redundant data rather than the main data, while the rest of multiplexers select the main data. For example, when a selection signal IOSLT 0 is activated high, a multiplexer 151 selects the redundant data RD rather than the main data MD 0 , and the rest of multiplexers 151 – 158 select corresponding main data MD 1 –MD 7 .

FIG. 12 is a block diagram showing the input/output control circuit 220 of FIG. 1 , according to at least one embodiment of the present invention. FIG. 13 is a circuit diagram for any one of the fuse boxes FBk of FIG. 12 , according to at least one embodiment of the present invention. FIG. 14 is a circuit diagram for any one of the decoders of FIG. 12 , according to at least one embodiment of the present invention.

As previously mentioned, when the address XA causes the address of the defective column to be at the output of the counter circuit), the address storage circuit 160 activates the corresponding one of the redundant enable signals RY — L 0 –RY — L 3 and RY — M. The column gate circuit 120 R selects one redundant page buffer according to activation of the redundant enable signal RY — Lk. An output of the selected page buffer is commonly supplied to multiplexers 151 – 158 of the multiplexer circuit 150 as the data RD. Only one of multiplexers 151 – 158 is controlled to select the redundant data RD depending on control of the input/output control circuit 220 . Accordingly, as shown in FIG. 12 , the input/output control circuit 220 includes signal generators 231 and 232 and a switch circuit 233 . The signal generator 231 includes fuse boxes 221 – 225 and decoders 226 – 230 . Fuse boxes 221 – 225 correspond to redundant enable signals RY — L 0 –RY — L 3 and RY — M, respectively. Decoders 226 – 230 correspond to fuse boxes 221 – 225 , respectively.

Each fuse box 221 – 225 stores information indicating whether or not any one of the main columns selected by a bite/word unit is defective when a corresponding enable signal is activated. For simplicity, FIG. 13 shows only fuse box 221 , though the same can apply to fuse boxes 222 – 225 . The fuse box 221 , includes an inverter INV 25 , a plurality of MOS transistors M 25 –M 33 and three fuses F 18 , F 19 and F 20 . When the redundant enable signal RY — L 0 is activated high, the PMOS transistors M 25 , M 28 and M 31 become turned on by the output signal nRY — L 0 of the inverter INV 25 . At this time, a logic state of output signals IRS 0 , IRS 1 and IRS 2 may be decided depending on the cutting state of the fuses F 18 , F 19 and F 20 . The cutting states of the fuses F 18 –F 20 reflect whether or not any of the selected main columns is defective column.

Referring to FIG. 12 again, each decoder 226 – 230 responds to output signals IRS 0 –IRS 2 of a corresponding fuse box to generate selection signals IOSLT 0 –IOSLT 7 . The selection signals IOSLT 0 –IOSLT 7 are transferred through the switch circuit 233 to the multiplexer circuit 150 . As shown in FIG. 14 , each decoder 226 – 230 includes a plurality of NAND gates G 17 –G 24 and a plurality of inverters INV 29 –INV 36 . Under a first example circumstance, if all input signals IRS 0 –IRS 2 have a logic high level, then the selection signal IOSLT 7 becomes logically high, and the rest of selection signals IOSLT 0 –IOSLT 6 become logically low. Accordingly, the multiplexer 158 of FIG. 11 selects the redundant data RD rather than the main data MD 7 , and the rest of multiplexers 151 – 157 select the corresponding main data. Under a second example circumstance, if all input signals IRSO–IRS 2 have a logic low level, the selection signal IOSLT 0 becomes logically high, and the rest of selection signals IOSLT 1 –IOSLT 7 become logically low. Accordingly, under the second circumstance, the multiplexer 151 of FIG. 11 selects the redundant data RD rather than the main data MD 0 , and the rest of the multiplexers 152 – 158 select the corresponding main data.

The signal generator 232 responds to activation of a scan flag signal FY — SCAN to generate selection signals IOSLT 0 –IOSLT 7 . Logic states of the selection signals IOSLT 0 –IOSLT 7 are programmed in advance. For example, the signal generator circuit 232 may be designed according to the following. The selection signal IOSLT 0 can be driven to a high logic level, and the rest of the selection signals IOSLT 1 –IOSLT 7 can be driven to a low logic level, e.g., by the signal line IOSLT 0 being connected to the power supply voltage, and the rest of the signal lines IOSLT 0 –IOSLT 7 being connected to the ground voltage. When the scan flag signal FY — SCAN is activated, the switch circuit 233 transfers the output signals IOSLT 0 –IOSLT 7 from the signal generator to the multiplexer circuit 150 . Therefore, irrespective of redundancy information, the multiplexer 151 sequentially outputs data from the redundant cell array 100 R during a test operation.

FIG. 15 is a flowchart illustrating a repair operation of the flash memory device 100 , according to at least one embodiment of the present invention. The flash memory device 100 can initially decide whether or not a defective page buffer exists in the page buffer circuits 110 M and 110 R. If so, then the defective page buffer group including the defective page buffer is repaired. Next, the flash memory device 100 can decide whether or not the main columns (or bit lines) of the main cell array 100 M include one or more defective main column(s). If a defective main column exists, then the defective main column is substituted for the redundant column.

In more detail, to decide whether or not the flash memory device 100 includes defective page buffer, at first the page buffer circuits are initialized (block S 100 ). For example, the nodes ND 1 of all the page buffers in the page buffer circuits 110 M and 110 R are initialized to a logical value, e.g., “1” (S 100 ). In addition, to initialize page buffers PB in the page buffer circuits 110 M and 100 R, control signals PLOAD and PBLCH of the page buffer PB are driven to a low level and a high level, respectively. As a result, node ND 1 of the latch LAT 1 becomes high. At this time, a data line DLk is pre-charged through a PMOS transistor M 8 of FIG. 2 . If an initialization operation of the page buffer circuits 110 M and 110 R is finished, then data of the page buffer circuits 110 M and 110 R may be read and evaluated (block output S 110 ) to decide whether or not a defective page buffer exists.

In advance, a counter circuit 130 sequentially generates an internal address ADD — int according to the loaded address (the initialized address). The main column decoder circuit 140 responds to the internal address ADD — int from the counter circuit 130 to generate selection signals. Therefore, the column gate circuit 120 M selects page buffers of the page buffer circuit 110 M at the a bite/word granularity. Data of the selected page buffers are transferred through the multiplexer circuit 150 to data lines DLk. At this time, all signals IOSLT 0 –IOSLT 7 for controlling the multiplexers have the logic low level. This indicates that a repair operation has not been carried out. In other words, since the address storage circuit 160 is not programmed, all output signals IOSLT 0 –IOSLT 7 of the signal generator 231 become low. At this time, the switch circuit 233 transfers outputs IOSLYT 0 –IOSLT 7 of the signal generator 231 to the multiplexer circuit 150 before the scan flag signal FY — SCAN is activated. As the internal address ADD — int is sequentially increased, all page buffers in the page buffer circuit 110 M sequentially will be selected.

As previously mentioned, the counter circuit 130 is operated until all page buffers of the page buffer circuit 110 M are selected in a normal operation mode. However, when the scan flag signal FY — SCAN is activated, the counter circuit 130 is continuously operated until all page buffers of the page buffer circuit 110 R have been selected. As the counter circuit 130 is continuously operated, the test decoder circuit 190 outputs selection signals YCR — Lmn and YCR — Mx by decoding the internal address ADD — int from the counter circuit 130 . In this case, the selection circuits YCR — Lmn and YCR — Mx are transferred through the switch circuit 180 to the column gate circuit 120 R. Pass transistors M 15 –M 30 are sequentially turned on, one by one, by increasing of the internal address, which correspondingly sequentially activates selection signals YCR — Lmn and YCR — Mx of the test decoder. This result is that initialized (or latched) data from all page buffers of the page buffer circuit 110 R are sequentially transferred through the column gate circuit 120 R of the multiplexer circuit 150 .

In a test operation mode in which the data of all page buffers in the page buffer circuits 120 M and 120 R are inspected, referring to FIG. 12 , the switch circuit 233 selects output signals of the signal generator 232 as output signals of the input/output control circuit 220 . As previously mentioned, output signals IOSLT 0 –IOSLT 7 of the signal generator 232 have a predetermined value (e.g., “10000000”). In other words, only IOSLT 0 signal has a high level, and the rest of signals (IOSLT 0 –IOSLT 7 ) have a low level. Under this condition, as shown in FIG. 11 , data of the page buffers are sequentially outputted in 1-bit units through the column gate circuit 120 R and then through the multiplexer 151 to the data line DL 0 . When data of the page buffer circuit 110 R are output through the rest of multiplexers to data lines DL 1 –DL 7 , such data will be regarded as invalid data.

According to explanation mentioned previously, all page buffers of page buffer circuits 110 M and 110 R are initialized, and then the initialized values of the page buffers of page buffer circuits 110 M and 110 R are selectively read and analyzed. By analyzing the output data (a data pattern of page buffers), page buffer(s) can be sorted. If a defective page buffer(s) is found to exist, then the page buffer group that includes the defective page buffer is replaced with a page buffer group in the page buffer circuit 110 R (block S 120 ).

For example, referring to FIG. 3 , if the page buffer group PBG 0 includes a defective page buffer, then the fuse F 0 corresponding to the page buffer group PBG 0 is cut, thereby completely preventing the signal on the signal line segment nWD 0 from adding to the signal content on the signal line PB — nWD. In other words, in contrast to the Background Art, the defective page buffer group PBG 0 can then no longer induce a failure result in the program/erase verification. Next, the address for pointing to the defective page buffer group (again, in the example, PBG 0 ) will be programmed in the address storage block 160 B of FIG. 7 . If an external entity subsequently attempts to access the address of the defective page buffer group in a normal operation mode, then the corresponding page buffer group in the page buffer circuit 110 R rather than the defective page buffer group PBG 0 will be selected through the column gate unit (e.g., YG 1 of FIG. 1 ) in the same way as mentioned in the discussion of FIG. 6 and FIG. 10 .

When a repair operation of page buffer circuits 110 M and 110 R is finished, it will be carried out in accordance with whether or not defective column(s) exist(s) in the main cell array 100 M. To decide whether a defective column(s) exist(s), at first data (that will be programmed) are loaded in the page buffer circuit 110 M. A programming operation is then carried out depending on the type of loaded data (block S 130 ). The programmed data (corresponding to the loaded data) will be accessed via by a read operation (block S 140 ). Program/read operation of the flash memory device 100 has been fully described above, and hence further description is omitted. Whether or not a defective column(s) exist(s) is determined by analyzing the output data. If a defective column(s) exist(s), then the circumstance is adaptively accommodated by storing the address of the defective column(s) in the address storage block 160 A (at block S 150 ). As a result, in subsequent normal operation, the redundant column is read instead of (or, in other words, is substituted for) the defective column. Stated differently, during a normal operation mode, the address of the defective column is internally mapped to the redundant column, as mentioned above in the discussion of FIGS. 8 , 11 and 12 .

As previously mentioned, column gate circuits 120 M and 120 R, and the multiplexer circuit 150 constitute a data output circuit that selectively outputs data from page buffer circuits 110 M and 110 R. A control circuit comprises the counter circuit 130 , the main column decoder circuit 140 , the address storage circuit 160 , the redundant column decoder circuit 170 , the switch circuit 180 , the test decoder circuit 190 and the input/output control circuit 220 . The control circuit controls the data output circuit to sequentially output data of page buffers of page buffer circuits 110 M and 110 R for reading by an external entity in an operation mode by which it is determined whether a page buffer group of page buffer circuits 110 M and 110 R include a defective page buffer.

Before repairing a defective column, data of the page buffers of the page buffer circuits are scanned to repair the defective page buffer group. As a result, it is possible to determine whether a program/erase failure has been caused by a defective column or a defective page buffer. In addition, by not treating (as would the Background Art) an entire column as being defective when only one of the page buffers is defective (and instead substituting a replacement page buffer for the defective buffer) redundancy effectiveness can be improved.

While the present invention has been described in connection with specific and preferred embodiments thereof, it is capable of various changes and modifications without departing the spirit and scope of the invention. It should be appreciated that the scope of the present invention is not limited to the detailed description of the invention hereinabove, which is intended merely to be illustrative.