Methods and circuits for programming of a semiconductor memory cell and memory array using a breakdown phenomenon in an ultra-thin dielectric
View Patent ↗A method of programming a memory cell is disclosed. The memory cell comprises a select transistor and a data storage element. The method comprises allowing current to flow through the data storage element until a predetermined current or voltage is detected. If the current or voltage exceeds a threshold, then the programming is deemed complete.
1. An apparatus for programming a memory cell, the memory cell comprising a select transistor and a data storage element, said select transistor having a gate connected to a select wordline, a source connected to a first terminal of said data storage element, and a drain connected to a column bitline, said apparatus comprising:
a first column transistor connected to said column bitline;
a wordline decoder connected to said gate of said select transistor through said select wordline, said wordline decoder providing an output signal to said select transistor to selectively activate said select transistor;
a sense amplifier that compares an input voltage to a reference voltage, said sense amplifier indicating that said memory cell as being adequately programmed if said input voltage is higher than said reference voltage, and if so, said sense amplifier providing a stop signal.
2. The apparatus of claim 1 wherein the data storage element is a MOS capacitor.
3. The apparatus of claim 1 wherein said data storage element comprises a conductive structure forming said second terminal, an ultra-thin dielectric underlying said conductive for physical storage of data, and a doped semiconductor region forming said first terminal underlying both the ultra-thin dielectric and the conductive structure.
4. The apparatus of claim 1 further including a first column transistor on said bitline controlled by a column decoder and a second column transistor on said bitline in series with said first column transistor, said second column transistor controlled by a current control circuit, wherein said input voltage is taken from between said first and second column transistor.
5. The apparatus of claim 4 wherein said current control circuit receives said stop signal from said sense amplifier, said control circuit operative to terminate current flow on said bitline when said stop signal is received.
6. An apparatus for programming a memory cell, the memory cell comprising a select transistor and a data storage element, said select transistor having a gate connected to a select wordline, a source connected to a first terminal of said data storage element, and a drain connected to a column bitline, said apparatus comprising:
a first column transistor connected to said column bitline;
a wordline decoder connected to said gate of said select transistor through said select wordline, said wordline decoder capable of turning on said select transistor;
means for measuring a current flowing through said data storage element during programming and providing a stop signal if said current flow is greater than a reference.
7. The apparatus of claim 6 wherein the data storage element is a MOS capacitor.
8. The apparatus of claim 6 wherein said data storage element comprises a conductive structure forming said second terminal, an ultra-thin dielectric underlying said conductive for physical storage of data, and a doped semiconductor region forming said first terminal underlying both the ultra-thin dielectric and the conductive structure.
9. The apparatus of claim 6 further including a second column transistor on said bitline in series with said first column transistor, said second column transistor controlled by a current control circuit, wherein said input voltage is taken from between said first and second column transistor.
10. The apparatus of claim 9 wherein said current control circuit receives said stop signal from said sense amplifier, said control circuit operative to terminate current flow on said bitline when said stop signal is received.