Test control circuit, semiconductor memory device and method for testing the same
Disclosed herein are test control circuit, semiconductor memory device, and testing method embodiments for suppressing variations in test time while reducing the influence of a failed cell. An embodiment operates by performing a first verify of a cell selected in a predetermined order; storing an address of the cell when the first verify is a fail until the number of addresses is a predetermined number; applying a predetermined voltage to a plurality of cells of an erase unit when a next fail is determined in the first verify after the predetermined number of addresses have been stored; and performing a second verify to one or more cells indicated by the predetermined number of addresses, wherein the first verify is performed from a cell at the next fail according to the predetermined order after the second verify has finished.
1. A test control circuit comprising:
an address sequencer that generates a first address for selecting a cell in a predetermined order;
a register that stores a second address of a cell that is determined to be a fail by a verify determination;
a selector that selects the first address generated by the address sequencer or the second address stored in the register based on whether or not one or more predetermined number of addresses have been stored in the register; and
a verify determination circuit that performs a verify determination of a cell which is indicated by the address selected by the selector;
wherein the verify determination circuit performs a first verify determination of a cell which is indicated by the first address generated by the address sequencer and performs a second verify determination of one or more cells which are indicated by the one or more predetermined number of addresses after a predetermined voltage has been applied to a plurality of cells of an erase unit where there is a cell determined to be a fail in the first verify determination in a state in which the one or more predetermined number of addresses have been stored in a register, and
wherein the selector selects the first address generated by the address sequencer after the second verify determination has been finished.
2. The test control circuit according to claim 1 , further comprising:
a second register that stores information that indicates whether or not an address is stored in the register,
wherein the selector selects the first address generated by the address sequencer until it is determined that the one or more predetermined number of addresses have been stored in the register based on the information stored in the second register.
3. The test control circuit according to claim 1 , wherein the address sequencer generates a next address in the predetermined order when the first verify determination has resulted in a pass or when the address has been stored in the register.
4. A semiconductor memory device comprising:
a test control circuit comprising:
an address sequencer that generates a first address for selecting a cell in a predetermined order;
a register that stores a second address of a cell that is determined to be a fail by a verify determination;
a selector that selects the first address generated by the address sequencer or the second address stored in the register based on whether or not one or more predetermined number of addresses have been stored in the register; and
a verify determination circuit that performs a verify determination of a cell which is indicated by the address selected by the selector;
wherein the verify determination circuit performs a first verify determination of a cell which is indicated by the first address generated by the address sequencer and performs a second verify determination of one or more cells which are indicated by the one or more predetermined number of addresses after a predetermined voltage has been applied to a plurality of cells of an erase unit where there is a cell determined to be a fail in the first verify determination in a state in which the one or more predetermined number of addresses have been stored in a register, and
wherein the selector selects the first address generated by the address sequencer after the second verify determination has been finished; and
a memory cell array including the cell.
5. A method for testing a semiconductor memory device, comprising:
performing a first verify of a cell selected in a predetermined order;
storing an address of the cell when the first verify is a fail until the number of addresses is a predetermined number;
applying a predetermined voltage to a plurality of cells of an erase unit when a next fail is determined in the first verify after the predetermined number of addresses have been stored; and
performing a second verify to one or more cells indicated by the predetermined number of addresses,
wherein the first verify is performed from a cell at the next fail according to the predetermined order after the second verify has finished.