摘要:
Techniques are provided for improving the accuracy of read operations of memory cells, where the threshold voltage (Vth) of a memory cell can shift depending on when the read operation occurs. In one aspect, a dummy voltage is applied to the word lines to cause a coupling up of the word lines and weak programming. This can occur when a specified amount of time has elapsed since a last program or read operation, or when a power on event is detected for the memory device. A number of read errors can also be considered. The dummy voltage is similar to a pass voltage of a program or read operation but no sensing is performed. The word line voltages are therefore provided at a consistently up-coupled level so that read operations are consistent. The coupling up occurs due to capacitive coupling between the word line and the channel.
摘要:
Techniques are provided for improving the accuracy of read operations of memory cells, where the threshold voltage (Vth) of a memory cell can shift depending on when the read operation occurs. In one aspect, a dummy voltage is applied to the word lines to cause a coupling up of the word lines and weak programming. This can occur when a specified amount of time has elapsed since a last program or read operation, or when a power on event is detected for the memory device. A number of read errors can also be considered. The dummy voltage is similar to a pass voltage of a program or read operation but no sensing is performed. The word line voltages are therefore provided at a consistently up-coupled level so that read operations are consistent. The coupling up occurs due to capacitive coupling between the word line and the channel.
摘要:
A memory stack structure for a three-dimensional device includes an alternating stack of insulator layers and spacer material layers. A memory opening is formed through the alternating stack. A memory material layer, a tunneling dielectric layer, and a silicon oxide liner are formed in the memory opening. A sacrificial liner is subsequently formed over the tunneling dielectric layer. The layer stack is anisotropically etched to physically expose a semiconductor surface of the substrate underneath the memory opening. The sacrificial liner may be removed prior to, or after, the anisotropic etch. The silicon oxide liner is removed after the anisotropic etch. A semiconductor channel layer can be deposited directly on the tunneling dielectric layer as a single material layer without any interface therein.
摘要:
Techniques for forming 3D memory arrays are disclosed. Memory openings are filled with a sacrificial material, such as silicon or nitride. Afterwards, a replacement technique is used to remove nitride from an ONON stack and replace it with a conductive material such as tungsten. Afterwards, memory cell films are formed in the memory openings. The conductive material serves as control gates of the memory cells. The control gate will not suffer from corner rounding. ONON shrinkage is avoided, which will prevent control gate shrinkage. Block oxide between the charge storage region and control gate may be deposited after control gate replacement, so the uniformity is good. Block oxide may be deposited after control gate replacement, so TiN adjacent to control gates can be thicker to prevent fluorine attacking the insulator between adjacent control gates. Therefore, control gate to control gate shorting is prevented.
摘要:
Fabrication techniques for a three-dimensional stack memory device remove the charge-trapping material from the select gate transistors and the dummy memory cells to avoid unintentional programming which increases the threshold voltage. In one approach, a stack is formed with a sacrificial material for the a) control gate layers of the select gate transistors and the dummy memory cells and the b) control gate layers of the data memory cells. A slit is formed to allow etchants to be introduced to selectively remove the sacrificial material and then the charge-trapping material for the select gate transistors and dummy memory cells. A protective layer is provided partway in the slit, or the slit is etched in two steps.
摘要:
Techniques are provided for reducing program disturb in a memory device. The techniques include compensating for a temperature in the memory device to reduce the upshift in the threshold voltage (Vth) of erased-state memory cells. A minimum allowable program pulse duration increases with temperature to account for an increase in the attenuation of a program pulse along a word line. A program pulse duration which accounts for reduced channel boosting at relatively high temperatures is reduced as the temperature increases. An optimum program pulse duration is based on the larger of these durations. The optimum program pulse duration can also be based on factors such as a measure of program disturb or a memory hole width. Program disturb can also be reduced by easing the requirements of a verify test for the highest data state.
摘要:
Techniques are provided for reducing the effects of short-term charge loss while programming charge-trapping memory cells. Short-term charge loss can result in a downshift and widening of a threshold voltage distribution. A programming operation includes a rough programming pass in which memory cells are programmed close to a final threshold voltage distribution, for each target data state. Subsequently, a negative voltage is applied to control gates of the memory cells. Subsequently, a final programming pass is performed in which the memory cells are programmed to the final threshold voltage distribution. Since the negative voltage accelerates charge loss, there is reduced charge loss after the final programming pass. The rough programming pass can use incremental step pulse programming for the lowest target data state to obtain information regarding programming speed. An initial program voltage in the final programming pass can be set based on the programming speed.
摘要:
Fabrication techniques for a three-dimensional stack memory device remove the charge-trapping material from the select gate transistors and the dummy memory cells to avoid unintentional programming which increases the threshold voltage. In one approach, a stack is formed with a different sacrificial material for the a) control gate layers of the select gate transistors and the dummy memory cells and the b) control gate layers of the data memory cells. A slit is formed to allow etchants to be introduced to selectively remove the sacrificial material and then the charge-trapping material for the select gate transistors and dummy memory cells. Subsequently, an etchant is introduced to remove the sacrificial material but not the charge-trapping material for the data memory cells. In other approaches, a protective layer is provided partway in the slit, or the slit is etched in two steps, and a common sacrificial material can be used.
摘要:
Techniques are provided to accelerate the redistribution of the holes in connection with an erase operation, so that there will be a reduced amount of redistribution of the holes after programming. As a result, short-term charge loss after programming is reduced. In one aspect, a positive control gate voltage is applied to a set of memory cells after erase and before programming. The positive control gate voltage has a relatively low amplitude and a long duration, compared to a programming voltage. The positive control gate voltage can be adjusted based on the erase depth of the memory cells and factors such as a count of program-erase cycles, a count of erase-verify iterations, sensing of a position of the lower tail, and a cross-sectional width of a vertical pillar of a memory hole.
摘要:
Techniques are provided for periodically monitoring and adjusting the threshold voltage levels of memory cells in a charge-trapping memory device. When a criterion is met, such as based on the passage of a specified time period, the memory cells are read to classify them into different subsets according to an amount of downshift in threshold voltage (Vth). Two or more subsets can be used per data state. A subset can also comprise cells which are corrected using Error Correction Code (ECC) decoding. The subsets of memory cells are refresh programmed, without being erased, in which a Vth upshift is provided in proportion to the Vth downshift. The refresh programming can use a fixed or adaptive number of program pulses per subset. Some cells will have no detectable Vth downshift or a minor amount of Vth downshift which can be ignored. These cells need not be refresh programmed.