Method for repairing a semiconductor memory
View Patent ↗A block repair device is used in a Dynamic Random Access Memory (DRAM) having a primary array with a defective cell and a redundant array with a redundant row. The block repair device stores a block repair configuration that determines the dimensions (e.g., the number of rows and columns spanned) of a repair block. Routing circuitry is configured by the stored block repair configuration to output some row and column address bits from received row and column addresses in a selected ratio. Comparison circuitry compares the row and column address bits output by the routing circuitry with the address of the defective cell that defines the repair block. When a match occurs, the comparison circuitry implements a block repair by activating the redundant row and by causing data to be written to or read from the activated redundant row instead of the primary array.
1. A memory block repair device, comprising:
a stored location of at least one defective memory cell;
a stored dimension of a repair block of redundant memory cells logically spanning the stored location;
a comparison circuit configured to evaluate a received memory address and to select redundant memory cells as identified by the stored dimension when the received memory address corresponds with the stored location of the at least one defective memory cell;
non-volatile elements selected from a group comprising fuses, anti-fuses, and flash EEPROM cells; and
routing circuitry coupled to the non-volatile elements to be configured by the block repair configuration to output a selected ratio of received row address bits to receive column address bits.
2. A memory block repair device, comprising:
a stored location of at least one defective memory cell;
a stored dimension of a repair block of redundant memory cells logically spanning the stored location;
a comparison circuit configured to evaluate a received memory address and to select redundant memory cells as identified by the stored dimension when the received memory address corresponds with the stored location of the at least one defective memory cell;
non-volatile elements selected from a group comprising fuses, anti-fuses, and flash EEPROM cells; and
routing circuitry coupled to the non-volatile elements to be configured by the block repair configuration to output a selected ratio of received row address bits to receive column address bits, wherein the comparison circuit includes circuitry for masking column address bits output by the routing circuitry and column address bits in at least a portion of the stored location of the at least one defective memory cell prior to comparing the address bits output by the routing circuitry with the stored dimension of at least a portion of the received memory address.
3. A memory block repair device, comprising:
a comparison circuit to select a block of redundant memory cells as identified by a stored dimension spanning a stored location of at least one defective memory cell when a received memory address corresponds with the stored location; and
routing circuitry to output to redundant memory cells a selected ratio of received row address bits to receive column address bits in response to the stored dimension.
4. The memory block repair device of claim 3 , further comprising non-volatile elements for storing the stored dimension.
5. The memory block repair device of claim 4 , wherein the non-volatile elements are selected from a group comprising fuses, anti-fuses, and flash EEPROM cells.
6. The memory block repair device of claim 3 , wherein the comparison circuit is configured to compare a portion of the stored location of the at least one defective cell with a portion of the received address, the portions determined by the stored dimension of the block of redundant memory cells.
7. The memory block repair device of claim 3 , wherein the comparison circuit is configured to compare a row address of the stored location of the at least one defective cell with a row address of the received address.