Current source component with process tracking characteristics for compact programmed Vt distribution of flash EPROM

• US 6,614,687 B2
• Filed: 05/03/2001
• Issued: 09/02/2003
• Est. Priority Date: 05/03/2001
• Status: Active Grant

• Current Assignee: Macronix International Co., Ltd.
• Original Assignee: Macronix International Co., Ltd.
• Inventors: Lu, Wenpin, Wang, Mam-Tsung, Lin, Baw-Chyuan, Chen, Ming-Shang
• Primary Examiner(s): TRAN, MICHAEL THANH
• Application Number:
  US09/848,786
• Publication Number:
  US 20020163835A1
• Time in Patent Office: 852 Days
• Field of Search: 365/185.18, 365/185.26
• US Class Current: 365/185.18
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 16/12 Programming voltage switching circuits
• CPC Class Codes: G11C 2211/565 Multilevel memory comprising elements in triple well structure

Abstract

A new structure and method with a process tracking current source component to program a flash EPROM memory is proposed. By applying a current source which varies not only with the process variation but also with the source bias of the cell being programmed, a self-convergent and high-efficiency programming can be achieved. This process tracking current source component provides less current for cells with higher erased Vt and larger current for cells with lower erased Vt.

A circuit for programming a floating gate transistor includes a current source component. The current source component couples in series between the floating gate transistor and an electrical sink during a programming interval. The current source component includes an electrical characteristic substantially matching the electrical characteristic of the floating gate transistor.

An integrated circuit memory module on a semiconductor substrate is disclosed. The integrated circuit memory module includes: an array of floating gate memory cells, decoders, and a plurality of current source components. The array of floating gate memory cells is arranged in M rows and N columns. The decoders couple to the M rows and N columns of memory cells to provide for reading and programming floating gate memory cells within a selected one of the M rows of the memory array. The plurality of current source components each couple in series between an electrical sink and a corresponding one of the floating gate memory cells within the selected one of the M rows during a programming interval. Each of the plurality of current source components includes an electrical characteristic substantially matching the electrical characteristic of the corresponding one of the floating gate memory cells to be programmed.

Claims

1. Circuitry for programming a floating gate transistor, and the floating gate transistor including gate, drain and source nodes, and the circuitry for programming comprising:

a current source component coupled in series between the floating gate transistor and an electrical sink during a programming interval, and the current source component including an electrical characteristic substantially matching the electrical characteristic of the floating gate transistor.

2. The circuitry for programming a floating gate transistor of claim 1, wherein the electrical characteristic of the current source component includes at least one of:

resistance, capacitance, conductance, and inductance.

3. The circuitry for programming a floating gate transistor of claim 1, wherein the current source component further comprises a process dependent electrical characteristic substantially matching the process dependent electrical characteristic of the floating gate transistor.

4. The circuitry for programming a floating gate transistor of claim 3, wherein the process dependent electrical characteristic of the current source component includes at least one of:

channel width, channel length, oxide thickness, dopant type and dopant density.

5. The circuitry for programming a floating gate transistor of claim 1, wherein the current source component further comprises;

a dummy cell including gate, drain and source nodes, and the drain node coupled to the source node of the floating gate transistor, the source node coupled to the electrical sink, the gate coupled to a voltage source, and the dummy cell fabricated utilizing processes substantially matching the fabrication processes utilized for the floating gate transistor.

6. The circuitry for programming a floating gate transistor of claim 5, wherein the current source component further comprises;

a resistor coupled in parallel with the dummy cell.

7. The circuitry for programming a floating gate transistor of claim 5, wherein the current source component further comprises;

a diode coupled in parallel with the dummy cell.

8. The circuitry for programming a floating gate transistor of claim 7, wherein the diode further comprises;

a MOSFET with the gate shorted to the drain side to act as a diode.

9. The circuitry for programming a floating gate transistor of claim 1, wherein the current source component further comprises;

a dummy cell including gate, drain and source nodes, and the drain node coupled to the source node of the floating gate transistor, the source node coupled to the electrical sink, and the gate coupled to a voltage source, and the dummy cell fabricated with dimensions substantially matching the dimensions of the floating gate transistor.

10. The circuitry for programming a floating gate transistor of claim 9, wherein the current source component further comprises;

a resistor coupled in parallel with the dummy cell.

11. The circuitry for programming a floating gate transistor of claim 9, wherein the current source component further comprises;

a diode coupled in parallel with the dummy cell.

12. The circuitry for programming a floating gate transistor of claim 11, wherein the diode further comprises;

a MOSFET with the gate shorted to the drain side to act as a diode.

13. The circuitry for programming a floating gate transistor of claim 1, wherein said current source component couples in series between the floating gate transistor and the electrical sink only during a programming interval.

14. The circuitry for programming a floating gate transistor of claim 1, further comprising;

a switch switchably coupling the current source component to the floating gate transistor only during the programming interval.

15. An integrated circuit memory module on a semiconductor substrate comprising;

an array of floating gate memory cells arranged in M rows and N columns and each cell including a floating gate transistor and the floating gate transistor including gate, drain and source nodes;

decoders coupled to the M rows and N columns of memory cells to provide for reading and programming floating gate memory cells within a selected one of the M rows of the memory array; and

a plurality of current source components each coupled in series between an electrical sink and a corresponding one of the floating gate memory cells within the selected one of the M rows during a programming interval, and each of the plurality of current source components including an electrical characteristic substantially matching the electrical characteristic of the corresponding one of the floating gate memory cells to be programmed.

16. The integrated circuit memory module of claim 15, wherein the array of M rows and N columns of floating gate memory cells are arranged in blocks with the source node of each floating gate transistor within the memory cells of each block coupled to a common source line;

and

wherein further the plurality of current source components each couple to the common source line of a corresponding one of the blocks.

17. The integrated circuit memory module of claim 15, wherein the electrical characteristic of each of the plurality of current source components includes at least one of:

resistance, capacitance, conductance, and inductance.

18. The integrated circuit memory module of claim 15, wherein the plurality of current source components each further comprise a process dependent electrical characteristic substantially matching the process dependent electrical characteristic of the corresponding one of the floating gate memory cells.

19. The integrated circuit memory module of claim 18, wherein the process dependent electrical characteristic of each of the plurality of current source components includes at least one of:

channel width, channel length, oxide thickness, dopant type and dopant density.

20. The integrated circuit memory module of claim 15, wherein each of the plurality of current source components further comprises;

a dummy cell including gate, drain, and source nodes, and the drain node coupled to the source node of the floating gate transistor within the corresponding one of the floating gate memory cells, the source node coupled to the electrical sink, the gate coupled to a voltage source, and the dummy cell fabricated utilizing processes substantially matching the fabrication processes utilized for the corresponding one of the floating gate memory cells.

21. The integrated circuit memory module of claim 20, wherein each of the plurality of current source components further comprises;

a resistor coupled in parallel with the dummy cell.

22. The integrated circuit memory module of claim 20, wherein each of the plurality of current source components further comprises;

a diode coupled in parallel with the dummy cell.

23. The integrated circuit memory module of claim 22, wherein the diode further comprises:

a MOSFET with the gate shorted to the drain side to act as a diode.

24. The integrated circuit memory module of claim 15, wherein each of the plurality of current source components further comprises;

a dummy cell including gate, drain and source nodes, and the drain node coupled to the source node of the floating gate transistor, the source node coupled to the electrical sink, the gate coupled to a voltage source, and the dummy cell fabricated with dimensions substantially matching the dimensions of the floating gate transistor.

25. The integrated circuit memory module of claim 24, wherein each of the plurality of current source components further comprises;

a resistor coupled in parallel with the dummy cell.

26. The integrated circuit memory module of claim 24, wherein each of the plurality of current source components further comprises;

a diode coupled in parallel with the dummy cell.

27. The integrated circuit memory module of claim 26, wherein the diode further comprises:

a MOSFET with the gate shorted to the drain side to act as a diode.

28. The integrated circuit memory module of claim 15, wherein each of the plurality of current source components couples in series between the floating gate transistor and the electrical sink only during a programming interval.

29. The integrated circuit memory module of claim 15, further comprising:

a plurality of switches each associated with a corresponding one of the plurality of current source components and each of the plurality of switches switchably coupling the corresponding one of the plurality of current source components to the corresponding one of the floating gate memory cells only during the programming interval.