Taiwan Semiconductor Manufacturing Comp. Ltd.

Juang-Ker Yeh

Jian-Hsing Lee

Kuo-Reay Peng

Ming-Chou Ho

The present invention provides method to fabricate a snap-back flash EEPROMS device. The method begins by forming a gate structure 22 24 28 26 on a substrate. The gate structure comprises: a tunnel oxide layer 22, a floating gate 24, integrate dielectric layer 28, and a control gate 26. A drain 14 is formed adjacent to the gate structure by an masking 51 and ion implant process. Next, a source side doped region 18 is formed adjacent to and under a portion of the gate structure 22 24 28 26 by an masking and ion implant process. Spacers 32 are now formed on the sidewalls of the gate structure. A source 20 is formed overlapping portion of the side source doped region 18 and adjacent to the spacers 32. The side source doped region has a lower dopant concentration than the source 20. This method forms a snap-back memory cell wherein the side source doped region 18 is used to apply a high voltage to operate the EEPROM cell in a snap-back erase mode.

Process for a snap-back flash EEPROM cell

A method to erase data from a flash EEPROM cell while electrical charges trapped in the tunnel oxide of a flash EEPROM cell are eliminated to maintain proper separation of the programmed threshold voltage and the erased threshold voltage after extended programming and erasing cycles. The method to erase a flash EEPROM cell begins by first applying a first relatively high positive voltage pulse to the source of the flash EEPROM cell. Simultaneously a ground reference voltage is applied to the control gate and to the semiconductor substrate. At this same time the drain is floating. The flash EEPROM cell is then detrapped by floating the source and drain and applying a second relatively high positive voltage pulse to the semiconductor substrate. At the same time a relatively large negative voltage pulse is applied to the control gate.

Method to improve flash EEPROM cell write/erase threshold voltage closure

A method to erase data from a flash EEPROM while electrical charges trapped in the tunneling oxide of a flash EEPROM are eliminated to maintain proper separation of the programmed threshold voltage and the erased threshold voltage after extended programming and erasing cycles. The method to erase a flash EEPROM cell begins by channel erasing to detrap the tunneling oxide of the flash EEPROM cell. The channel erasing consists floating the drain and the second diffusion well and concurrently applying the ground reference potential to the semiconductor substrate and the first diffusion well. Concurrently a first relatively large negative voltage pulse is applied to the control gate, as a first moderately large positive voltage pulse is applied to said source. The method to erase then proceeds with the source erasing to remove charges from the floating gate of the flash EEPROM cell. The source erasing consists of applying a second relatively large negative voltage pulse to the control gate of said EEPROM cell and concurrently applying a second moderately large positive voltage pulse to a first diffusion well. At the same time the ground reference potential continues to be applied to the semiconductor substrate, while the drain and a second diffusion well is allowed to float.

Mixed mode erase method to improve flash eeprom write/erase threshold

A method to erase data from a flash EEPROM while electrical charges trapped in the tunneling oxide of a flash EEPROM are eliminated to maintain proper separation of the programmed threshold voltage and the erased threshold voltage after extended programming and erasing cycles. The method to erase a flash EEPROM cell begins by channel erasing to remove charge from the floating gate of the flash EEPROM cell. The channel erasing consists of applying a first relatively large negative voltage pulse to the control gate of said EEPROM cell and concurrently applying a first moderately large positive voltage pulse to a first diffusion well. At the same time a ground reference potential is applied to the semiconductor substrate, while the drain and a second diffusion well is allowed to float. The method to erase then proceeds with the source erasing to detrap the tunneling oxide of the flash EEPROM cell. The source erasing consists continued floating the drain and the second diffusion well and concurrently applying the ground reference potential to the semiconductor substrate and the first diffusion well. Concurrently a second relatively large negative voltage pulse is applied to the control gate, as a second moderately large positive voltage pulse is applied to said source.

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Hsin-Chu, Taiwan

Juang-Ker Yeh