Patent Publication Number: US-2012026790-A1

Title: Non-volatile memory device including block state confirmation cell and method of operating the same

Description:
PRIORITY DOCUMENT 
     This application claims the benefit under 35 U.S.C. §120 of U.S. application Ser. No. 12/071,349, filed on Feb. 20, 2008, and Korean Patent Application No. 10-2007-0061874, filed on Jun. 22, 2007, in the Korean Intellectual Property Office (KIPO), the entire contents of each of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     Non-volatile memory devices that may be electrically erased and programmed may retain data even if a supplied power is discontinued. A representative example of non-volatile memory devices is flash memory. 
     Memory cells that constitute flash memory may include a cell transistor having a control gate, a floating gate, a source and a drain. A cell transistor of a flash memory may be programmed or erased according to the Fowler-Nordheim (F-N) tunneling mechanism. 
     Data in a cell transistor may be erased by applying a ground voltage to a control gate of the cell transistor and applying a voltage higher than a power supply voltage to a semiconductor substrate (or bulk). Under such erasing bias conditions, a strong electric field may be formed between a floating gate and the semiconductor bulk due to a large voltage difference therebetween. Thus, electrons present in the floating gate may be discharged to the semiconductor bulk according to the F-N tunneling mechanism. In this case, the threshold voltage of the erased cell transistor may decrease. 
     The cell transistor may be programmed by applying a voltage higher than the power supply voltage to the control gate and applying a ground voltage to a drain and the semiconductor bulk. Under such bias conditions, electrons may be injected into the floating gate of the cell transistor according to the F-N tunneling mechanism. In this case, the threshold voltage of the programmed cell transistor may increase. A state in which electrons are injected into the floating gate may be referred to as a “programming state,” and a state in which electrons do not exist in the floating gate may be referred to as an “erased state.” A threshold voltage in the programming state may be greater than zero and a threshold voltage in the erased state may be less than zero. 
     Recently, research has been conducted into development of a multi-level flash memory capable of storing two or more data bits in one memory cell in order to improve the degree of intensity of flash memory. A memory cell that may store multiple data bits may be referred to as a multi-level cell (MLC), and a memory cell that may store a single data bit may be referred to as a single-level cell (SLC). 
     The MLC may have four or more threshold voltage distributions, and four or more data storing states corresponding to the distributions in order to store two or more data bits. However, as more data bits are stored in the MLC, more threshold voltage distributions may be needed by the MLC, thereby increasing a time required to read the data from the MLC. 
     SUMMARY 
     Example embodiments may provide a semiconductor device having a block state confirmation cell storing information indicating the number of data bits written to a plurality of memory cells. 
     Example embodiments may also provide a method of storing information indicating the number of data bits written to a plurality of memory cells and/or reading the data from the memory cells based on the information. 
     Example embodiments may also provide a memory data programming method of storing information indicating the number of data bits written to a plurality of memory cells. 
     According to example embodiments, there may be provided a semiconductor device including one or more memory blocks each including a block state confirmation cell and one or more memory cells, the block state confirmation cell to store information indicating a number of data bits written to the one or more memory cells, and/or a controller reading only stored data bits from the respective one or more memory blocks, based on the information stored in the block state confirmation cells. 
     A number of bits that is to be stored in each of the block state confirmation cells may be one bit less than the number of data bits that is to be stored in the memory cells of each respective memory block to which each block state confirmation cell corresponds. 
     According to example embodiments, there may be provided a memory data reading method of reading data from one or more memory cells including detecting a number of data bits written to the one or more memory cells and/or reading only the detected data bits from the one or more memory cells. 
     According to example embodiments, there may be provided a memory programming method including writing the data to a plurality of memory cells, storing information indicating a number of data bits written to the plurality of memory cells, and/or verifying only the written data bits, which are indicated in the stored information. 
    
    
     
       BRIEF DESCRIPTION 
       The above and other features and advantages of will become more apparent by describing in detail example embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a block diagram of a semiconductor device with a plurality of memory blocks, according to example embodiments; 
         FIG. 2  is a block diagram illustrating in more detail one of the memory blocks illustrated in  FIG. 1 , which has a block state confirmation cell, according to example embodiments; 
         FIG. 3  is a diagram illustrating a method of determining the number of data bits written to a memory cell, based on information stored in the block state confirmation cell illustrated in  FIG. 2 , according to example embodiments; and 
         FIG. 4  is a block diagram of a semiconductor device with the block state confirmation cell illustrated in  FIG. 2 , according to example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments will be described in detail with reference to the accompanying drawings. Accordingly, while example embodiments are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments to the particular forms disclosed, but on the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of example embodiments. Like numbers refer to like elements throughout the description of the figures. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between”, “adjacent” versus “directly adjacent”, etc.). 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising,”, “includes” and/or “including”, when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the FIGS. For example, two FIGS. shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. 
       FIG. 1  is a block diagram of a semiconductor device with a plurality of memory blocks MB 11  through MB 4   n , according to example embodiments. The semiconductor device of  FIG. 1  may be divided into a plurality of planes PLANE™ through PLANE 4 , each having n memory blocks, e.g., memory blocks MB 11  through MB 1   n . Although  FIG. 1  may illustrate that the semiconductor device includes the four planes PLANE 1  through PLANE 4 , it would be apparent to those of ordinary skill in the art that the number of planes is not limited to four and therefore may vary. 
     Row decoders RD 1  and RD 2  may be located between the planes PLANE 1  through PLANE 4 . However, it would be apparent to those of ordinary skill in the art that the row decoders RD 1  and RD 2  can be located in various other locations other than between the planes PLANE 1  through PLANE 4 . For example, the row decoder RD 1  may not be located between the planes PLANE 1  and PLANE 2 , but instead, may be located to the left side of the plane PLANE 1 . 
     The semiconductor device of  FIG. 1  may further include a plurality of page buffers PB 1  and PB 2 . The page buffers PB 1  and PB 2  may either receive write data from outside and then transmit it to the memory blocks MB 11  through MB 4   n , or receive read data from the memory blocks MB 11  through MB 4   n  and transmit it to the outside. The semiconductor device of  FIG. 1  may include a controller CTRL. The controller CTRL may control a write operation and a read operation to be performed on the memory blocks MB 11  through MB 4   n.    
       FIG. 2  is a block diagram illustrating in detail the memory block MB 11  from among the memory blocks illustrated in  FIG. 1 , which has a block state confirmation cell BSCC. Referring to  FIG. 2 , the memory block MB 11  may include a plurality of memory cells MC 1  through MCn and a block state confirmation cell BSCC. Each of the memory cells MC 1  through MCn may store data. The block state confirmation cell BSCC may store information indicating the number of data bits written to each of the memory cells MC 1  through MCn. The information may indicate the number of bits, in which the data has been written among the bits of the memory cell.  FIG. 2  illustrates the memory block MB 11  from among the memory blocks MC 1  through MCn illustrated in  FIG. 1  but all or some of the other memory blocks MC 2  through MCn may have the same construction as the memory block MB 11  illustrated in  FIG. 2 . 
     The controller CTRL illustrated in  FIG. 1  may read the data from the memory block MB 11  through MB 4   n  based on the number of the bits indicated in the information stored in the block state confirmation cell BSCC. More specifically, the controller CTRL may read the information from the block state confirmation cell BSCC in order to determine the number of data bits written to the memory cells MC 1  through MCn. Thus, according to example embodiments, a semiconductor device may not need to perform a read operation on all the data bits written to the memory cells MC 1  through MCn but may instead perform the read operation on only the data bits written to the memory cells MC 1  through MCn. Accordingly, it may be possible to increase the speed of performing the read operation of the semiconductor device. 
     The block state confirmation cell BSCC, according to example embodiments, may be available for a read operation performed in order to verify data written to memory cells. More specifically, for data verification, a semiconductor device, according to example embodiments, may use the number of bits indicated in information stored in the block state confirmation cell BSCC. That is, the data written to the memory cells MC 1  through MCn may be verified based on the number of the bits indicated in the information stored in the block state confirmation cell BSCC. For example, a first data bit may be written to the memory cells MC 1  through MCn, and then information indicating that the first data bit has been written may be stored in the block state confirmation cell BSCC. Then, the first data bit written to the memory cells MC 1  through MCn may be verified, based on the information that is stored in the block state confirmation cell BSCC and may indicate that the first data bit has been written. Next, a second data bit may be written to the memory cells MC 1  through MCn, and then information indicating that the second data bit has been written may be stored in the block state confirmation cell BSCC. Then, the second data bit written to the memory cells MC 1  through MCn may be verified. That is, only the first data bit may be verified without verifying the second data bit during the verification of the already written first data bit, and only the second data bit may be verified without verifying the other data bits following the second data bit thereof during the verification of the already written second data bit. 
     Also, the block state confirmation cell BSCC, according to example embodiments, may be available for a general read operation performed in order to read data written to memory cells. 
     A number of bits that may be stored in the block state confirmation cell BSCC may be one bit less than the number of data bits stored in the memory cells MC 1  through MCn of the memory block MB 11 , to which the block state confirmation cell BSCC belongs. For example, assuming that n data bits may be stored in the memory cell MC 1 , n−1 data bits may be stored in the block state confirmation cell BSCC. 
       FIG. 3  is a diagram illustrating a method of determining the number of data bits written to memory cells based on information stored in the block state confirmation cell BSCC illustrated in  FIG. 2 , according to example embodiments. 
     As illustrated in  FIG. 3 , if all bits checkbit 1  through checkbit(n−1) of the block state confirmation cell BSCC are “off,” it may be determined that only a single data bit has been written to the memory cells MC 1  through MCn illustrated in  FIG. 2 . Thus, only the 1 data bit may be read from the memory cells MC 1  through MCn. Also, as illustrated in  FIG. 3 , if only the first bit Checkbit 1  of the block state confirmation cell BSCC is “on” and the other bits checkbit 1  through checkbit(n−1) are “off,” it may be determined that 2 data bits have been written to the memory cells MC 1  through MCn. Thus, the 2 data bits may be read from the memory cells MC 1  through MCn. In example embodiments, that a bit of the block state confirmation cell BSCC is “on” may infer that the bit is programmed to “0,” and that a bit of the block state confirmation cell BSCC is “off” may infer that the bit is programmed to “1.” Also, if first and second bits Checkbit 1  and Checkbit 2  of the block state confirmation cell BSCC are “on” and the other bits are “off,” it may be determined that 3 data bits have been written to the memory cells MC 1  through MCn. Thus, the 3 data bits may be read from the memory cells MC 1  through MCn. If all bits of the block state confirmation cell BSCC are “on,” it may be determined that n data bits have been written to the memory cells MC 1  through MCn. Thus, the n data bits may be read from the memory cells MC 1  through MCn. 
     Referring to  FIG. 2 , the block state confirmation cell BSCC may belong to a first data page of the corresponding memory block MB 11 . The block state confirmation cell BSCC may be connected to a first word line WL 1  from among a plurality of word lines connected to the corresponding memory block MB 11 . Alternatively, the block state confirmation cell BSCC may belong to a data page other than the first data page, and may be connected to word lines other than the world line WL 1 , such as WL 2  through WL 32 . 
     The memory block MB 11  may further include one or more spare cells SC 2  through SCn that can replace defective cells from among the memory cells MC 1  through MCn. The total number of the spare cells SC 2  through SCn and the block state confirmation cells BSCC in a row may be equal to the total number of the memory cells MC 1  through MCn in the row. That is, one of the spare cells according to example embodiments, may be used as the block state confirmation cell BSCC. 
       FIG. 4  is a block diagram of a semiconductor device having the block state confirmation cell BSCC illustrated in  FIG. 2 , according to example embodiments. Referring to  FIG. 4 , a control logic  460  may read information stored in the block state confirmation cell BSCC of a memory cell array  410  in order to determine a current writing state of the memory cell array. That is, the control logic  460  may determine a number of data bits written to each of memory cells. Then, a command register  450  may select a reading manner based on the determination result. That is, the command register  450  may determine the number of data bits to be read from the memory cell. Then, the data may be read from the memory cell array  410  by using the control logic  460 , an input/output buffer/latch  470 , a Y gating circuit  430 , a data register/sense amplifier  420 , an output driver  490 , and/or a global buffer  480 . 
     As described above, in a semiconductor device, a method of reading data from a memory and a memory programming method according to example embodiments may be performed, wherein a read operation is performed on only data bits written to a memory cell, rather than on all the bits of the memory cell, thereby increasing the speed of performing the read operation. 
     While example embodiments have been particularly shown and described with reference to example embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of example embodiments as defined by the following claims.