Memory card with enhanced testability and methods of making and using the same

#The present invention relates to the field of semiconductor memory cards that can be used to extend the memory available to a wide variety of electronic devices that capture or use electronic data. More specifically, the present invention relates to a memory card with enhanced testability so that upon failure, particularly a failure in the field, the card can be examined and tested so that the source of, or reason for, the failure can be identified to improve the reliability and quality of subsequently manufactured cards.

#Memory cards are flat memory units that incorporate semiconductor memory in a casing called a skin. A memory card may be about the size of a postage stamp, a matchbook or a credit card. Memory cards also include electrical contacts or connectors so that the memory in the card can be connected to a device that captures or uses digital data, for example, a digital camera. In this way, memory cards provide primary or additional memory capacity for the host device in much the same way that floppy disks provide additional memory capacity for computers.

#Memory cards are typically non-volatile, meaning that they do not require power to maintain the data stored on them. Memory cards are also solid-state, semiconductor devices. Consequently, there are no moving parts to skip or break down while the stored data is being retrieved. Memory cards offer relatively high storage capacity, recently 32 to 64 MB. Capacities of up to 128 MB and 256 MB are expected in the near future. Memory cards also provide fast data transfer rates, security features and easy storage of data given the small size of the cards.

#The accompanying drawings illustrate preferred embodiments of the present invention and are a part of the specification. Together with the following description, the drawings demonstrate and explain the principles of the present invention.

#FIGS. 1a and 1b illustrate a conventional memory card at various stages of the manufacturing process.

#FIG. 2 illustrates an improved memory card according to the present invention without the card's skin.

#Throughout the drawings, identical elements are designated by identical reference numbers.

#The present invention is an improved memory card which provides better means for testing the card following a failure, particularly a field failure, to improve subsequently manufactured memory cards. As described above, memory cards are solid-state, semiconductor devices that provide primary or additional memory for electronic devices that use digital data. Memory cards are typically non-volatile, meaning that they do not require power to maintain the data stored on them. However, within the scope of the present invention, memory cards may be volatile memory that could be used, for example, to increase the memory on a laptop or personal digital assistant.

#The present invention can make use of several earlier inventions which, like the present invention, have been assigned to Matrix Semiconductor, Inc. of Santa Clara, Calif. These previous inventions are the subject of U.S. Pat. Nos. 6,034,882 and 6,185,122, both entitled “Vertically Stacked Field Programmable Nonvolatile Memory and Method of Fabrication” to Johnson, et al. and U.S. patent application Ser. No. 09/560,626 filed Apr. 28, 2000 by Johan Knall and entitled “Three Dimensional Memory Array and Method of Fabrication.” These three documents are incorporated herein by reference in their entireties. As described and claimed in these patents, it is possible to fabricate multiple layers of memory that are stacked vertically in, for example, a memory card. Consequently, the memory capacity of the card can be increased while at the same time decreasing the X-Y real estate required for the memory unit on the card's substrate.