Advanced Micro Devices Corporation

Spansion Llc.

Mimi Lee

Darlene G Hamilton

Edward Hsia

Ken Cheong Cheah

Kulachet Tanpairoj

Alykhan Madhani

Yi He

Mark W Randolph

Zhizheng Liu

Xin Sheng Guo

Kendra Nguyen

A system and method is discussed for providing programmable test conditions for a built-in self test circuit of a flash memory device. The present invention employs a flash memory having BIST circuit for testing the memory and a BIST interface circuit adapted to adjust the test conditions of the memory tests. The BIST interface circuit is operable to receive one or more global variables associated with the test conditions of a plurality of tests used on the flash memory and to output results of the memory tests based on the value of the variables. The global variables are used to adjust the test conditions and to trim one or more references used in various flash memory tests and operations. The system may further include a serial communications medium for communicating the global variables to the BIST interface and test results from the interface.

Input of test conditions and output generation for built-in self test

Methods of performing a sector erase of flash memory devices incorporating built-in self test circuitry are provided. The present invention employs an interactive verification and sector erase algorithm to verify and repeatedly erase the sector until a portion of the groups of each page of the sector are erased or a first maximum number of erase pulses is achieved. The algorithm further includes a word verification and erase operation that sequentially verifies and erases each word of the sector until each word is erased or a second maximum number of erase pulses is achieved. The second maximum number of erase pulses may be based on a function of the first maximum number of erase pulses. The second maximum number of erase pulses may be input to the sector erase algorithm as a multi-bit code. The second maximum number of erase pulses and conversion of the multi-bit code may be based on a binary multiple of the first maximum number of erase pulses.

[object Object]

A method is discussed for providing programmable test conditions for a built-in self test circuit of a flash memory device. The method comprises providing a BIST interface adapted to adjust a test condition used in a BIST circuit, providing the memory cells of the Flash memory device, and providing the BIST circuit adapted to test the flash memory. The method further comprises communicating with the BIST interface one or more global variables associated with the test condition, adjusting the test condition used by the BIST circuit based on the values represented by the global variables, performing one or more test operations on the flash memory in accordance with the adjusted test condition, and reporting the results of the memory test operations. The method of the present invention may further include a serial communications medium and the use of a serial test protocol for communicating the global variables to the BIST interface and test results from the interface. The global variables may also be provided by a memory device user.

Automated tests for built-in self test

A method of erasing a flash electrically erasable read only memory (EEPROM) device composed of a plurality of memory cells includes pre-programming the plurality of memory cells, applying an erase pulse to the plurality of memory cells followed by an erase verification. The erase verification is followed by soft programming any memory cells having a threshold voltage below a predetermined minimum level and applying a positive gate stress to the plurality of memory cells. The erase method prevents overerasing and provides a tightened threshold voltage distribution.

Memory device and method using positive gate stress to recover overerased cell

A method of programming a dual cell memory device having a first charge storing cell and a second charge storing cell. According to one aspect of the method, the method can include over-erasing the first and second charge storing cells to shift an erase state threshold voltage of the memory device to be lower than a natural state threshold voltage. According to another aspect of the method, the method can include programming the first and second charge storing cells to the same data state and verifying that the second programmed charge storing cell stores charge corresponding to the data state. If the verification fails, both charge storing cells can be re-pulsed.

Method of dual cell memory device operation for improved end-of-life read margin

A method of programming and reading a dual cell memory device. The method includes storing a selected program level in each cell and reading one of the cells to determine a single data value stored by the memory device.

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Santa Clara, CA, United States of America

Mimi Lee