Abstract:
A NAND flash memory device performing an error detecting and data reloading operation during a copy back program operation is provided. The device includes a cell array having a plurality of planes and a parity cell array having a plurality of parity planes. Each of the parity planes stores a parity of each of the planes. Additionally, the device includes a parity generating and parity column selecting circuit generating a new parity about reloaded data from an outside during a copy back program operation, and storing the new parity on a parity plane corresponding to a plane on which the reloaded data is stored.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Embodiments of the invention relate to a semiconductor memory device. More particularly, embodiments of the invention relate to a NAND flash memory device performing an error detecting and data reloading operation during a copy back program operation. 
   This application claims the benefit of Korean Patent Application No. 2005-83216 filed Sep. 7, 2005, the subject matter of which is hereby incorporated by reference. 
   2. Description of the Related Art 
   A broad class of semiconductor memory devices has been developed to store and subsequently provide data within various electronic and computer applications. Semiconductor memory devices may be generally classified into random access memory (RAM) devices and read only memory (ROM) devices. The data stored in a RAM device is volatile in nature, that is, it is lost when power is no longer applied to the RAM. In contrast, data stored in ROM is nonvolatile in nature. It remains stored in ROM even when power is no longer applied to the ROM. 
   RAM devices may be further classified as dynamic RAM (DRAM), static RAM (SRAM), etc. ROM devices may be further classified as programmable ROM (PROM), erasable PROM (EPROM), electrically EPROM (EEPROM), flash memory, etc. Flash memory devices include NAND flash memory devices and NOR flash memory devices. 
   The NAND flash memory device supports a so-called “copy back program” operation in addition to the customary program, read, and erase operations. The copy back program operation is essentially adapted to “copy back” data stored on a source page into a target page. That is, the data stored on the source page is temporarily stored on a page buffer, and then immediately programmed into the target page. Through use of the copy back program operation, the programming speed of a NAND flash memory device may be markedly improved, because the otherwise duplicate process of reading data from the source page, as well as the process of externally reloading data may be omitted. 
   However, a conventional NAND flash memory device may generate a 1-bit error during the process of reading data from the source page through a page buffer during a copy back program operation. Additionally, another 1-bit error may be generated during the process of reading data from the target page. That is, the conventional NAND flash memory device may generate two (2) 1-bit errors (or a cumulative 2-bit error) during a conventional copy back program operation. 
   Generally, a NAND flash memory device may readily correct a 1-bit error in a single page of data as it passes through an associated memory controller. This is, however, not the case for a 2-bit error. 
   SUMMARY OF THE INVENTION 
   Embodiments of the invention provide a NAND flash memory device adapted to prevent the generation of a 2-bit error during a copy back program operation. 
   Thus, in one embodiment, the invention provides a NAND flash memory device comprising; a cell array comprising a plurality of planes, a parity cell array comprising a plurality of parity planes, each parity plane storing parity data associated with a corresponding one of the plurality of planes, and a parity generation and parity column selection circuit adapted to generate new parity data associated with reloaded data during a copy back program operation, and further adapted to program the new parity data in a parity plane corresponding to a plane storing the reloaded data. 
   In another embodiment, the invention provides a NAND flash memory device comprising; a cell array comprising a plurality of planes, a parity cell array comprising a plurality of parity planes, each parity plane storing parity data associated with a corresponding one of the plurality of planes, a parity generation circuit adapted to generate parity data to be stored on each one of the plurality of parity planes upon receiving data to be stored on the corresponding plurality of planes, and a parity column selection circuit supplying the parity data to the parity cell array in response to a column address signal after receiving the parity data from the parity generation circuit, wherein the parity generation circuit if further adapted to generate new parity data associated with reloaded data during a copy back program operation, and the parity column selection circuit is further adapted to supply the new parity data to a parity plane selected by the column address signal. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram illustrating an error detecting operation for a NAND flash memory device according to an embodiment of the invention; 
       FIG. 2  is a block diagram illustrating a data reloading operation for a NAND flash memory device according to an embodiment of the invention; 
       FIG. 3  is a block diagram illustrating an internal configuration of a parity generating and parity column selecting circuit illustrated in  FIG. 2 ; and 
       FIG. 4  is block diagram illustrating an internal configuration of a parity plane detector illustrated in  FIG. 3 . 
   

   DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   Several embodiments of the invention will now be described with reference to the accompanying drawings. However, the present invention is not limited to only the illustrated embodiments. Rather, the embodiments are presented as teaching examples. 
   A NAND flash memory device according to one embodiment of the invention is adapted to generate an error detection code (EDC) during a copy back program operation, and is further adapted to perform an error detecting operation. Additionally, the NAND flash memory device performs a data reloading operation during a copy back program operation. The error detecting operation and the data reloading operation will be described with reference to the exemplary block diagrams shown in  FIGS. 1 and 2 . 
     FIG. 1  is a block diagram illustrating an exemplary execution of an error detecting operation adapted for use in a NAND flash memory device according to an embodiment of the invention. Referring to  FIG. 1 , the exemplary NAND flash memory device includes a cell array  110 , a page buffer  120 , a column selection and a parity generation circuit  130 , a parity cell array  210 , a parity page buffer  220 , a parity generation and parity column selection circuit  230 , and a comparator  300 . 
   Cell array  110  and parity cell array  210  facilitate program and read operations in a conventional page mode. Cell array  110  stores data and the parity cell array  210  stores the EDC. The EDC functions as parity data. Parity data is stored on a page by page basis in relation to a corresponding page of data stored in cell array  110 . 
   Page buffer  120  temporarily stores data to be programmed into cell array  110  or data to be read from cell array  110 . Parity page buffer  220  temporarily stores parity data to be programmed into parity cell array  210  or data to be read from parity cell array  210 . 
   Column selection and parity generation circuit  130  receives data from an external data input buffer (not shown), and supplies data to page buffer  120  in response to a column address (CA) signal. Column selection and parity generation circuit  130  generates first parity data (Py) from data received from page buffer  120 , and supplies first parity data (Py) to comparator  300 . 
   Parity generation and parity column selection circuit  230  generates second parity data (Px) from data received from a data input buffer (not shown) in response to the column address (CA) signal. Alternatively, parity generation and parity column selection circuit  230  receives second parity data (Px) from parity page buffer  220  and supplies this data to comparator  300 . 
   Comparator  300  detects an error by comparing first and second parities data (Px and Py). Comparator  300  outputs a pass signal when first and second parity data (Px and Py) are identical, and a fail signal if different. During the copy back program operation, comparator  300  generates a fail signal when an error occurs in an operation reading data stored in source page  11  of cell array  110 , for example. 
   Hereinafter, an exemplary error detection operation in a NAND flash memory device, which also performs a copy back program operation, will be described in some additional detail with reference to  FIG. 1 . 
   First, data input from an external data input buffer (not shown) is programmed to a source page via data flow {circle around ( 1 )}. Column selection and parity generation circuit  130  receives the input data, and transmits it to page buffer  120  in response to the column address (CA) signal. Here, a data loading operation is used to transmit the input data to page buffer  120 . That is, the input data is transmitted to page buffer  120  through the data loading operation. On the other hand, parity generation and parity column selection circuit  230  generates second parity data (Px) from the input data, and transmits the second parity data (Px) to the parity page buffer  220  in response to the column address (CA) signal. 
   The input data loaded into page buffer  120  and the corresponding first parity data (Py) loaded into parity page buffer  220  are programmed at the same time by the program operation. 
   Referring to data flow {circle around ( 2 )}, the data and corresponding parity data stored in relation to a source page in cell array  110  and parity cell array  210  are read into page buffer  120  and parity page buffer  220 , respectively. A 1-bit error may be generated during the process of reading data from source page  11 . Within the context of embodiments of the invention, an error detection operation is used to detect this 1-bit error. 
   Referring to data flow {circle around ( 3 )}, the 1-bit error generated during the read operation is detected by comparing corresponding first parity data (Py), which is generated by column selection and parity generation circuit  130 , with second parity data (Px), which is generated by parity generation and parity column selection circuit  230 . Column selection and parity generation circuit  130  generates first parity data (Py) from read data stored in page buffer  120 , and then supplies first parity data (Py) to comparator  300 . Parity generation and parity column selection circuit  230  supplies second parity data (Px) stored in parity page buffer  220  to comparator  300 . Comparator  300  generates a pass signal when the first and second parity data (Py and Px) are identical, and generates a fail signal when they are different. Here, where second parity data (Px) is equal to first parity data (Py) no 1-bit error has been generated during the read operation associated with source page 11. However, where second parity data (Px) is different from first parity data (Py), a 1-bit error has occurred. 
   Referring to data flow {circle around ( 4 )} shown in  FIG. 2 , a data reloading operation is performed. The data reloading operation will be described in some additional detail with reference to  FIG. 2 . 
   Referring to data flow {circle around ( 5 )}, the read data stored in page buffer  120  and the corresponding parity data stored in parity page buffer  220  are programmed into a target page  12  when the first and second parity data (Px and Py) are identical as determined above. In contrast, when a 1-bit error occurs during the copy back program operation, the copy back program may be terminated or an error correction operation may be performed before completion of the copy back operation. 
     FIGS. 2 through 4  are diagrams illustrating an exemplary data reloading operation adapted for use with a NAND flash memory device according to an embodiment of the invention. Here, the data reloading operation is used to replace a portion of source page  11  with new data during a copy back program operation. That is, the data loading operation is used to reload new data into page buffer  120  after reading data stored in source page  11  into page buffer  120  via data flow {circle around ( 2 )}. At this point, new parity data for the reloaded data must be stored into parity page buffer  220 . 
     FIG. 2  is a block diagram illustrating an exemplary data reloading operation adapted for use with a NAND flash memory device according to an embodiment of the invention. Referring to  FIG. 2 , a plurality of planes  111  through  114  and a plurality of parity planes  211  through  214  are defined in a cell array and a parity cell array, respectively. That is, cell array  110  may comprises a plurality of planes  111  through  114 , and parity cell array  210  may comprises a plurality of parity planes  211  through  214 . Referring to data flow {circle around ( 1 )} in  FIG. 1 , parities planes  211  through  214  are used to store parity data associated with the data stored in planes  111  through  114 , respectively. In the illustrated example, parity cell array  210  is assumed to store 4-bit parity data. 
   The data and associated parity data for source page  11  are read into page buffer  120  and parity page buffer  220  via data flow {circle around ( 2 )}, the error detection operation is performed via data flow {circle around ( 3 )}, and then the data reloading operation is performed via data flow {circle around ( 4 )}. For example, it is assumed for illustrative purposes that new data is reloaded into first page buffer  121 . At this point, new parity data associated with the reloaded data must be stored into first parity page buffer  221 . 
   Referring to  FIG. 2 , column selection and parity generation circuit  130  receives the reloaded data during the data reloading operation and transmits the reloaded data to first page buffer  121  in response to the column address (CA) signal. On the other hand, parity generation and parity column selection circuit  230  generates new parity associated with the reloaded data, and transmits the new parity data to first parity page buffer  221  in response to the column address (CA) signal. 
     FIG. 3  is a block diagram further illustrating an internal configuration of an exemplary parity generation and parity column selection circuit like the one illustrated in  FIG. 2 . Referring to  FIG. 3 , the parity generation and parity column selection circuit  230  comprises a demultiplexer  410 , a plurality of parity generators  421  to  424 , a parity plane detector  430 , and a plurality of load drivers  441  to  444 . 
   Demultiplexer  410  receives the reloaded data during the data reloading operation, and selects a parity generator that generates new parity in response to the column address (CA) signal. For example, demultiplexer  410  receives the reloaded data and transmits the data inputted in response to column address (CA) signal to first parity generator  421 . 
   Each of a plurality of parity generators  421  to  424  has an identical configuration and an operational principle. Referring to data flow {circle around ( 1 )} shown in  FIG. 1 , parity generators  421  to  424  generate parity data P 1  to P 4 , respectively. During a data reloading operation, first parity generator  421  receives the reloaded data and generates first new parity P 1 ′. At this point, the second through fourth parity generators  422  to  424  maintain the previous parities P 2  to P 4 . 
   Parity plane detector  430  detects a parity plane in response to the column address (CA) signal during the data reloading operation and generates a flag signal as a detection result. As described above, parity plane detector  430  detects the first parity plane  211 , and generates the first flag signal. A configuration and an operation of parity plane detector  430  will be described in some additional detail with reference to  FIG. 4 . 
   A plurality of load drivers  441  to  444  have an identical configuration and an operational principle. The plurality of load drivers  441  to  444  transmit parities, which are generated from a plurality of parity generators  421  to  424  in response to a flag signal generated from the parity plane detector  430 , to a plurality of parity page buffers  221  to  224 . As described above, first load driver  441  transmits the first new parity P 1 ′ to first parity page buffer  221  in response to first flag signal F 1  during the data loading operation 
     FIG. 4  is block diagram further illustrating an exemplary internal configuration of a parity plane detector as illustrated in  FIG. 3 . Referring to  FIG. 4 , parity plane detector  430  includes a plurality of latches  431  to  434 , and a decoder  435 . 
   The plurality of latches  431  to  434  store flag signals F 1  to F 4 , and transmits the flag signals F 1  to F 4  to a plurality of load drivers  441  to  444  of  FIG. 3  in synchronization with a clock signal CLK during the data loading operation. The decoder  435  decodes the column address (CA) signal and enables one among the plurality of latches  431  to  434  during the data loading operation. As described above, decoder  435  decodes the column address (CAO signal and then enables the first latch  431 . First latch  431  supplies first flag signal F 1  to first load driver  441  in synchronization with the clock signal (CLK). 
   As described above, a NAND memory flash memory device is disclosed that performs error detection and data reloading operations during a copy back program operation. In one aspect, the NAND flash memory device generates new parity associated with reloaded data when the data reloading operation is performed during the copy back program operation. The new parity is programmed on a parity plane selected by a column address signal. 
   As described above, a NAND flash memory device according to an embodiment of the invention can detect a 1-bit error generated during a data read operation associated with a source page during the copy back program operation. The NAND flash memory device generates new parity associated with the reloaded data and programs the new parity into a parity plane selected by the column address signal when the data reloading operation is performed during the copy back program operation. 
   It will be apparent to those skilled in the art that various modifications and variations can be made to the foregoing embodiments which are presented in the context of exemplary circuits. Thus, it is intended that the present invention cover the modifications and variations to the embodiments as defined by the appended claims and their equivalent.