Semiconductor memory devices have become more popular for use in various electronic devices. For example, non-volatile semiconductor memory is used in cellular telephones, digital cameras, personal digital assistants, mobile computing devices, non-mobile computing devices and other devices. Flash memory is among the most popular non-volatile semiconductor memories.
Consumers of semiconductor memory have seen significant advantages as a result of a history of steadily scaling down the physical dimensions of the components of the memory systems. For example, smaller memory cells can be packed more densely on a given die area, allowing the user to access more memory capacity for the same price. However, scaling the sizes of memory cells entails certain risks. In order to achieve the advantage of higher memory capacity for a fixed die size, these smaller memory cells must be packed more closely together. Doing so, however, may result in a greater number of manufacturing defects, such as shorting between adjacent word lines, shorting between word lines and interconnects, shorting between word lines and the substrate, broken word lines, etc. Such defects often result in corruption of data stored on the word lines being programmed and nearby word lines. In some cases, these defects are not realized during tests conducted by manufacturers prior to packaging and shipping. Rather, these defects only manifest themselves after the memory systems has been used from some time and, therefore, only begin to corrupt data after programming and erasing is performed by the user.
Some prior systems have sought to combat latent manufacturing defects by reading programmed data after programming. However, by the time programming has completed, the programming process may have already damaged data being stored in other nearby memory cells.