MOSFET technology for programmable address decode and correction

• US 6,521,958 B1
• Filed: 08/26/1999
• Issued: 02/18/2003
• Est. Priority Date: 08/26/1999
• Status: Expired due to Term

• Current Assignee: Nanya Technology Corporation
• Original Assignee: Micron Technology, Inc.
• Inventors: Forbes, Leonard, Noble, Wendell P., Cloud, Eugene H.
• Primary Examiner(s): Fourson, George
• Assistant Examiner(s): Estrada, Michelle
• Application Number:
  US09/383,804
• Time in Patent Office: 1,272 Days
• Field of Search: 257/405, 257/391, 257/392, 438/286, 438/288
• US Class Current: 257/391
• CPC Class Codes: G11C 11/4087 Address decoders, e.g. bit - or word line decoders; Multiple line decoders
• CPC Class Codes: G11C 16/0466 comprising cells with charge storage in an insulating layer, e.g. metal-nitride-oxide-silicon [MNOS], silicon-oxide-nitride-oxide-silicon [SONOS] G11C16/0483, G11C16/0491 take precedence
• CPC Class Codes: G11C 29/789 using non-volatile cells or latches
• CPC Class Codes: G11C 8/08 Word line control circuits, e.g. drivers, boosters, pull-up circuits, pull-down circuits, precharging circuits, for word lines
• CPC Class Codes: G11C 8/10 Decoders
• CPC Class Codes: H01L 27/11803 using field effect technology
• CPC Class Codes: H03K 3/356008 ensuring a predetermined initial state when the supply voltage has been applied; storing the actual state when the supply voltage fails digital storage cells each combining volatile and non-volatile storage properties G11C14/00
• CPC Class Codes: H10B 12/50 Peripheral circuit region structures

Abstract

Structures and methods for PLA capability on a DRAM chip according to a DRAM optimized process flow are provided by the present invention. These structures and methods include using MOSFET devices as re-programmable elements in memory address decode circuits in a DRAM integrated circuit. The structures and methods use the existing process sequence for MOSFET'"'"'s in DRAM technology. An illustrative embodiment of the present invention includes a non-volatile, reprogrammable circuit switch. The circuit switch includes a metal oxide semiconductor field effect transistor (MOSFET) in a substrate. The MOSFET has a source region, a drain region, a channel region between the source and drain regions, and a gate separated from the channel region by a gate oxide. The MOSFET is a programmed MOSFET having a charge trapped in the gate oxide adjacent to the source region such that the channel region has a first voltage threshold region (Vt1) and a second voltage threshold region (Vt2), such that the programmed MOSFET operates at reduced drain source current.

Claims

1. A circuit switch, comprising:

a metal oxide semiconductor field effect transistor (MOSFET) in a substrate, the MOSFET having a source region, a drain region, a channel region between the source and drain regions, and a gate separated from the channel region by a gate oxide;

a wordline coupled to the gate;

a first transmission line coupled to the source region;

a second transmission line coupled to the drain region; and

wherein the MOSFET is a programmed MOSFET having a charge trapped in the gate oxide adjacent to the source region and substantially no charge trapped in the gate oxide adjacent to the drain region such that the channel region has a first voltage threshold region (Vt1) and a second voltage threshold region (Vt2).

2. The circuit switch of claim 1, wherein the first transmission line includes a source line and wherein the second transmission line includes a bitline.

3. The circuit switch of claim 2 wherein the source line is operatively coupled to the source region of the MOSFET and the bitline is operatively coupled to the drain region.

4. The circuit switch of claim 1, wherein the charge trapped in the gate oxide adjacent the source region includes a trapped electron charge.

6. The circuit switch of claim 1, wherein the second voltage threshold region (Vt2) in the channel is adjacent the source region, the first voltage threshold region (Vt1) in the channel is adjacent the drain region wherein the Vt2 has a higher voltage threshold than the Vt1.

7. The circuit switch of claim 1, wherein the programmed MOSFET includes a non-volatile, reprogrammable MOSFET.

5. A circuit switch, comprising:

a n-channel metal oxide semiconductor field effect transistor (NMOS) in a substrate, the NMOS having a source region, a drain region, a channel region between the source and region regions, and a gate separated from the channel region by a gate oxide;

a wordline coupled to the gate;

a source line operatively coupled to source region;

a bitline operatively coupled to the drain region; and

wherein the NMOS is a programmed NMOS having an electron charge trapped in the gate oxide adjacent to the source region and substantially no charge trapped in the gate oxide adjacent to the drain region such that the channel region has a first voltage threshold region (Vt1) and a second voltage threshold region (Vt2), Vt2 having a higher voltage threshold than Vt1.

8. A non-volatile, reprogrammable switch, comprising:

a metal oxide semiconductor field effect transistor (MOSFET) in a substrate, the MOSFET having a source region, a drain region, a channel region between the source region and the drain region, and a gate separated from the channel region by a gate oxide;

a wordline coupled to the gate;

a first transmission line coupled to the source region;

a second transmission line coupled to the drain region; and

wherein the MOSFET is a programmed MOSFET having an electron charge trapped in the gate oxide adjacent to the source region and substantially no charge trapped in the gate oxide adjacent to the drain region such that the channel region has a first voltage threshold region (Vt1) adjacent to the drain region and a second voltage threshold region (Vt2) adjacent to the source region, the Vt2 having a greater voltage threshold than Vt1.

9. A latch on a substrate, comprising:

a pair of cross coupled inverters, wherein each inverter includes a first conduction type MOSFET and a second conduction type MOSFET, each MOSFET has a source region, a drain region, a channel region between the source and the drain regions, and a gate separated from the channel region by a gate oxide;

a first transmission line coupled to the gates of a first inverter in the cross coupled pair and to the drain regions of a second inverter in the cross coupled pair;

a second transmission line coupled to the gates of a second inverter in the cross coupled pair and to the drain regions of a first inverter in the cross coupled pair; and

wherein at least one of the MOSFETs is a programmed MOSFET having a charge trapped in the gate oxide adjacent to the source region and substantially no charge trapped in the gate oxide adjacent to the drain region such that the channel region has a first voltage threshold region (Vt1) and a second voltage threshold region (Vt2).

10. The latch of claim 9, wherein the first conduction type MOSFETs in each inverter include n-channel type MOSFETs (NMOS) and the second conduction type MOSFETs include p-channel type MOSFETs (PMOS).

11. The latch of claim 9, wherein the source regions in the first conduction type MOSFETs are coupled to a first voltage potential, and wherein the drain regions in the second conduction type MOSFETs are coupled to a second voltage potential.

12. The latch of claim 9, wherein the source of the at least one MOSFET is coupled to the source region of a MOSFET that is not a programmed MOSFET.

13. The latch of claim 9, wherein the latch further includes an input line operatively coupled to the first transmission line and the second transmission line.

14. The latch of claim 9, wherein the charge trapped in the gate oxide adjacent the source region includes a trapped electron charge.

15. The latch of claim 9, wherein the second voltage threshold region (Vt2) in the channel in the programmed MOSFET is adjacent to the source region of the programmed MOSFET, the first voltage threshold region (Vt1) in the channel in the programmed MOSFET is adjacent the drain region of the programmed MOSFET, and wherein the Vt2 has a higher voltage threshold than the Vt1.

16. A programmable decoder, comprising:

an array of latches on a substrate, wherein each latch comprises;

a pair of cross coupled inverters, wherein each inverter includes a first conduction type MOSFET and a second conduction type MOSFET, each MOSFET has a source region, a drain region, a channel region between the source and drain regions, and a gate separated from the channel region by a gate oxide;

a number of first transmission lines coupled to the gates of the a first inverter in the cross coupled pair of inverters in the array of latches, and to the drain regions of a second inverter in the cross coupled pair of inverters in the array of latches;

a number of second transmission lines coupled to the gates of the a second inverter in the cross coupled pair of inverters in the array of latches, and to the drain regions of a first inverter in the cross coupled pair of inverters in the array of latches; and

wherein at least one latch includes a MOSFET which is a programmed MOSFET having a charge trapped in the gate oxide adjacent to the source region and substantially no charge trapped in the gate oxide adjacent to the drain region such that the channel region has a first voltage threshold region (Vt1) and a second voltage threshold region (Vt2).

17. The programmable decoder of claim 16, wherein the number of first transmission lines include a number of address input lines and wherein the number of second transmission lines includes a number of output lines.

18. The programmable decoder of claim 16, wherein the charge trapped in the gate oxide adjacent to the source region of the programmed MOSFET includes a trapped electron charge.

19. The programmable decoder of claim 16, wherein the second voltage threshold region (Vt2) in the channel of the programmed MOSFET is adjacent to the source region, the first voltage threshold region (Vt1) in the channel of the programmed MOSFET is adjacent to the drain region, and wherein the Vt2 has a higher voltage threshold than the Vt1.

20. The programmable decoder of claim 16, wherein the programmed MOSFET includes a non-volatile, reprogrammable MOSFET.

21. An integrated circuit, comprising:

an array of latches on a substrate, wherein each latch comprises;

a pair of cross coupled inverters, wherein each inverter includes a first conduction type MOSFET and a second conduction type MOSFET, each MOSFET has a source region, a source region, a channel region between the first and the second source/drain regions, and a gate separated from the channel region by a gate oxide;

a number of first transmission lines coupled to the gates of the a first inverter in the cross coupled pair of inverters in the array of latches, and to the drain regions of a second inverter in the cross coupled pair of inverters in the array of latches;

a number of second transmission lines coupled to the gates of the a second inverter in the cross coupled pair of inverters in the array of latches, and to the drain regions of a first inverter in the cross coupled pair of inverters in the array of latches;

an address driver coupled to the number of first transmission lines;

a number of row drivers and at least one redundant row driver coupled to the number of second transmission lines; and

wherein at least one latch includes a programmed MOSFET having a charge trapped in the gate oxide adjacent to the source region and substantially no charge trapped in the gate oxide adjacent to the drain region such that the channel region has a first voltage threshold region (Vt1) and a second voltage threshold region (Vt2).

22. The integrated circuit of claim 21, wherein the first conduction type MOSFETs in each inverter include n-channel type MOSFETs (NMOS) and the second conduction type MOSFETs include p-channel type MOSFETs (PMOS).

23. The integrated circuit of claim 21, wherein the source regions in the first conduction type MOSFETs are coupled to a first voltage potential, and wherein the source regions in the second conduction type MOSFETs are coupled to a second voltage potential.

24. The integrated circuit of claim 21, wherein the source of the at least one MOSFET is coupled to the source region of a MOSFET that is not a programmed MOSFET.

25. The integrated circuit of claim 21, wherein each latch in the array of latches further includes an input line operatively coupled to the first transmission line and the second transmission line.

26. The integrated circuit of claim 21, wherein the second voltage threshold region (Vt2) in the channel in the at least one programmed MOSFET is adjacent to the source region of the programmed MOSFET, the first voltage threshold region (Vt1) in the channel in the at least one programmed MOSFET is adjacent to the drain of the programmed MOSFET, and wherein the Vt2 has a higher voltage threshold than the Vt1 and the first source/drain region of the programmed MOSFET is a source region.

27. The integrated circuit of claim 21, wherein the number of first transmission lines include a number of address input lines, and wherein the number of second transmission lines include a number of output lines.

28. An electronic system, comprising:

a memory; and

a processor coupled to the memory, wherein the memory includes a programmable decoder, the programmable decoder comprising;

an array of latches on a substrate, wherein each latch includes a pair of cross coupled inverters, wherein each inverter includes an n-channel MOSFET (NMOS) and a p-channel MOSFET (PMOS), each MOSFET has a source region, a drain region, a channel region between the source and the drain regions, and a gate separated from the channel region by a gate oxide, and wherein the NMOS and PMOS of each inverter are coupled at the drain region;

a number of address input lines coupled to the gates of a first inverter in the cross coupled pair of inverters in the array of latches, and to the drain region of a second inverter in the cross coupled pair of inverters in the array of latches;

a number of output lines coupled to the gates of the a second inverter in the cross coupled pair of inverters in the array of latches, and to the drain region of a first inverter in the cross coupled pair of inverters in the array of latches; and

wherein at least one of the MOSFETs in the array of latches is a programmed MOSFET having a charge trapped in the gate oxide adjacent to the source region and substantially no charge trapped in the gate oxide adjacent to the drain region such that the channel region of the programmed MOSFET has a first voltage threshold region (Vt1) and a second voltage threshold region (Vt2).

29. The electronic system of claim 28, wherein the source regions in the PMOS transistors in each latch are coupled to a first voltage potential, and wherein the source regions in the NMOS transistors in each latch are coupled to a second voltage potential.

30. The electronic system of claim 28, wherein memory coupled to the processor includes a memory coupled to the processor on a single semiconductor chip.

31. The electronic system of claim 28, wherein each latch in the array of latches further includes an input line operatively coupled to the number of address lines and to the number of output lines.

32. The electronic system of claim 28, wherein the second voltage threshold region (Vt2) in the channel in the at least one programmed MOSFET is adjacent to the source region of the programmed MOSFET, the first voltage threshold region (Vt1) in the channel in the at least one programmed MOSFET is adjacent to the drain region of the programmed MOSFET, and wherein the Vt2 has a higher voltage threshold than the Vt1.

33. The electronic system of claim 28, wherein the number of address input lines include a number of address input lines coupled to each latch in the array of latches from an address driver, and wherein the number of output lines include a number of output lines coupled to at least one row driver and at least one redundant row driver.