摘要:
A method and apparatus are disclosed for detecting if a semiconductor circuit has been exposed to ultra-violet light. An ultra-violet light detection circuit detects exposure to ultra-violet light and will automatically activate a security violation signal. The security violation signal may optionally initiate a routine to clear sensitive data from memory or prevent the semiconductor circuit from further operation. The ultra-violet light detection circuit detects whether a semiconductor circuit has been exposed to ultra-violet light, for example, by employing a dedicated mini-array of non-volatile memory cells. At least two active bit lines, blprg and bler, are employed corresponding to program and erase, respectively. One of the bit lines is only programmable and the other bit line is only eraseable. Generally, all of the bits in the dedicated non-volatile memory array are initially in approximately the same state, which could be erased, programmed or somewhere in between. An offset current is added to one bit line and a change in the resulting current difference is used to detect an exposure to ultra-violet light.
摘要:
A method is provided to determine erase threshold voltages of memory transistors and thereby identify unusable memory transistors. A voltage is applied to the common source of a selected memory transistor and gradually incremented until a logical HIGH bit is read as a logical LOW bit. By iteratively incrementing Vbias, the erase threshold voltage for each memory transistor can be determined. In one process, the erase threshold voltage for each memory transistor in a memory device is determined and then the memory device is put under stress tests to simulate normal operative conditions. After the stress tests, the erase threshold voltage of each memory transistor can be once again determined to ascertain the change in the erase threshold voltage, i.e., the data retention characteristic, of each memory transistor.
摘要:
A bit line selector for a virtual ground non-volatile read only memory (“NROM”) cell array is disclosed. The selector transistors are oriented such that the channel length is perpendicular to the bit line and the channel width is parallel to the bit line. Subsequent reduction in the bit line pitch does not affect the channel width of the select transistors or their drive current.
摘要:
A programmable reference current source used with a memory array during test and user modes to program or erase verify. The reference current source is programmable so that optimal reference currents can be determined during test mode. A value representing the optimal reference current is stored so that the reference current source provides the determined reference current during user mode.
摘要:
Programming lines are attached to reference cells of a memory device. A state machine controls voltages and/or currents applied to the reference cells via the programming lines to program and verify a program state of the reference cells. The state machine utilizes existing array cell programming operations conducted by the programming lines to the reference cells. The utilization of internal circuitry of the memory device in the programming of reference cells reduces the sort and test time of the memory device. The memory device may be a flash memory device or any device having reference cells, and the reference cells may be of any configuration or structure, including nitride layer cells.
摘要:
A memory system has the capability to adjust a program or erase voltage if the time to program or erase is excessive. The memory system comprises at least a memory cell, a voltage value storage device, a voltage source, and a voltage adjustment circuit. The voltage value storage device stores a voltage value. The voltage source receives and converts the voltage value into a voltage. The voltage source applies the voltage to at least one memory cell. The voltage adjustment circuit is also coupled to receive the stored voltage value. The voltage adjustment circuit determines the time required to program or erase at least one memory cell using the voltage value. If the time to program or erase at least one memory cell is excessive, the voltage adjustment circuit increments the voltage value stored in the voltage value storage device.
摘要:
A method is provided for biasing a NAND array EEPROM during programming to allow the array to be scaled down further before reach punchthrough. The sources of the ground-select transistors of the NAND array are biased at V.sub.cc instead of ground to reduce the voltage drop across the source and drain of the ground-select transistors. As a result, the channel length of the ground-select transistors can be further shortened before punchthrough is obtained, resulting in a higher density EEPROM.
摘要:
A method for programing a cell in an array of flash memory cells connected to a bit line using hot-electron injection. In the method, a negative word line voltage is applied to unselected cells connected to the bit line to create a negative gate to source voltage in the unselected cells. The negative gate to source voltage in the unselected cells is provided to prevent overerased cells, or cells which have a negative threshold, from turning on to reduce bit line leakage current.
摘要:
A technique to determine whether multiple memory cells are programmed or erased. After a program or erase operation, respective program or erase verify operations are performed. A logical gate is coupled to measure the state of each memory cell. When all memory cells selected to be programmed or erased are programmed or erased then the output of the logical gate indicates successful program or erase verify. Thus, by using a single logical gate coupled to measure the states of multiple memory cells, only the output of the logical gate need be measured to determine successful program or erase verification of multiple memory cells.
摘要:
A capacitor structure which exhibits a constant capacitance at non-negative voltages is provided by erasing a P-well floating gate NMOS transistor prior to its use as a capacitor. By erasing the transistor, a negative threshold voltage is obtained, thereby turning on the transistor and placing the transistor in an inversion state where the MOS capacitance is voltage-independent. Such transistors can be utilized as capacitors, whereby one plate of the capacitor corresponds to the control gate of the transistor and the other plate corresponds to the commonly connected source, drain, P-well, and deep N-well regions of the transistor, in voltage regulator circuits or other circuits in which node stabilization is desired. As a result, the capacitance is constant even at initialization when zero volts is applied.