Incrementally programmable non-volatile memory

• US 9,570,175 B2
• Filed: 08/05/2014
• Issued: 02/14/2017
• Est. Priority Date: 08/05/2013
• Status: Active Grant

• Current Assignee: Jonker LLC
• Original Assignee: Jonker LLC
• Inventors: Liu, David K. Y.
• Primary Examiner(s): Hur, J. H.
• Application Number:
  US14/452,269
• Publication Number:
  US 20150036427A1
• Time in Patent Office: 924 Days
• US Class Current: 1/1
• CPC Class Codes: G11C 11/5628 Programming or writing circuits; Data input circuits
• CPC Class Codes: G11C 11/5635 Erasing circuits
• CPC Class Codes: G11C 11/5642 Sensing or reading circuits; Data output circuits
• CPC Class Codes: G11C 16/0416 comprising cells containing a single floating gate transistor and no select transistor, e.g. UV EPROM
• CPC Class Codes: G11C 16/10 Programming or data input circuits
• CPC Class Codes: G11C 16/14 Circuits for erasing electrically, e.g. erase voltage switching circuits
• CPC Class Codes: G11C 16/22 Safety or protection circuits preventing unauthorised or accidental access to memory cells
• CPC Class Codes: G11C 17/12 using field-effect devices
• CPC Class Codes: G11C 17/18 Auxiliary circuits, e.g. for writing into memory
• CPC Class Codes: H10B 20/20 Programmable ROM [PROM] devices comprising field-effect components H10B20/10 takes precedence

Abstract

An array of programmable non-volatile devices, such as a nominal OTP cell, is adapted such that a V_t representing a particular binary logic state can be changed over time. This allows for re-programming and emulating a few times or multi-time programmable device.

Claims

1. A programmable non-volatile device having at least a first programmed state and a second unprogrammed state which can be varied in time and comprising:

a programming control circuit configured to generate a programming voltage;

a control gate configured to apply said programming voltage from said programming control circuit to the device;

wherein said programming voltage includes at least a first voltage value and a second higher voltage value;

a floating gate coupled to the control gate and adapted to store a first charge amount corresponding to said first programmed state in response to said programming voltage including said first voltage value being applied at a first programming time;

said floating gate being further adapted to store a second charge amount that also corresponds to said first programmed state in response to said programming voltage including said second voltage value being applied at a second programming time;

wherein said programming control circuit is further configured to perform a reset operation which sets said floating gate to a reference state in which at least said first charge amount is stored on said floating gate prior to setting such gate to store said second charge amount at said second programming time;

further wherein the device does not include an electrical based erase circuit which removes electric charge from said floating gate for erase operations and is adapted to store a first unique binary programmed state (1 or

     0) at different times using both a first threshold value and a second separate threshold value set for the device.

2. The device of claim 1 wherein said reset operation effectuates a pseudo erase of a prior state of the floating gate without removing charge.

3. The device of claim 1 wherein the device can store at least three different logic states by storing three different charge amounts on said floating gate.

4. The device of claim 1 wherein the programming control circuit is configured to perform an operation of time multiplexing a total capacity (Ct) of the non-volatile memory device across P distinct periods such that an available capacity (Ca)=Ct/P at any moment in time.

5. The device of claim 1 wherein the non-volatile memory device operates as a multi-time programmable array without requiring redundancy for each programming cycle.

6. The device of claim 1 wherein the non-volatile memory device is a multi-level cell that can be operated by said programming control circuit as a single bit cell with a different program threshold voltage during each programming cycle.

7. The device of claim 1 wherein said programming control circuit performs said reset operation and second programming automatically at predetermined programmable time intervals.

8. The device of claim 1 wherein said programming control circuit is configure to perform an operation of operating a first array in the non-volatile memory device with a first threshold voltage corresponding to a first logical state;

and operating a second array in the non-volatile memory device with a second different threshold voltage corresponding to said same first logical state.

9. The device of claim 1 wherein said programming control circuit is configured to perform an operation of dividing a total capacity (Ct) of the non-volatile memory array containing M cells and N distinct program levels into P distinct periods, including:

performing a first program operation in a 1st period of the P distinct periods to store logical data in the M cells of the array using at least two (2) or more separate program levels {PVt1, PVt2} of the N distinct program levels;

performing a second program operation in a subsequent 2nd period of the P distinct periods to store logical data in the M cells of the array using at least (2) separate program levels {PVt3, PVt4} of the N distinct program levels, wherein at least one of {PVt3, PVt4} is different from and greater than {PVt1, PVt2}.

10. In a programmable non-volatile memory device including a programming circuit, an array of cells each having a floating gate, a control gate, a source region, a drain region, and a channel coupling said source region and said drain region, the improvement comprising:

the memory device being adapted such that said array of cells is initialized at a first state, and

a) can be set by the programming circuit to a second single binary logic state (1 or

     0) at a first threshold voltage (Vt1) in response to a first program operation; and

b) can be set by the programming circuit to said same second single binary logic state (1 or

     0) at a second different threshold voltage (Vt2) which is higher than Vt1 in response to a second program operation; and

said programming control circuit is further configured to perform a reset operation which sets each cell in said array to a reference state threshold voltage (Vr) equal at least to a prior programming state threshold voltage prior to setting such cell to a new state at said second programming time;

wherein the memory device does not require an electrical based erase controller to remove electric charge from each floating gate of such array of cells between program operations.

11. The memory device of claim 10 wherein a first portion of said programmable non-volatile memory device is implemented as a one-time programmable (OTP) device.

12. The memory device of claim 11 wherein the first portion of such array of cells is programmed to said second single binary state at said first threshold voltage Vt1 while a second portion of such array of cells is

programmed to said second single binary state at said second threshold voltage Vt2.

13. The memory device of claim 12 wherein the OTP device is on a single die.

14. The device of claim 10 wherein said reset operation effectuates a pseudo erase of a prior state of the cell without removing charge from the cell.

15. The device of claim 10 wherein said reference state threshold voltage Vr is equal to said first threshold voltage (Vt1) used for programming said cells in said array in said first program operation.

16. The device of claim 10 wherein said device can store at least three different logic states using three different threshold voltages.

17. The device of claim 10 wherein the cells include a multi-level cell that can be operated by said programming control circuit as a single bit cell with a different program threshold voltage during each programming cycle.

18. The device of claim 10 wherein said programming control circuit performs said reset operation and second program operation automatically at programmable predetermined time intervals.

19. In a programmable non-volatile device including a programming control circuit, an array of cells each having a floating gate, a control gate, a source region, a drain region, and a channel coupling said source region and said drain region, the improvement comprising:

the device being adapted such that;

a first portion of the array of cells can be set to a first initial state Vt, and can be programmed to a second single binary logic state (1 or

     0) at a first threshold voltage (Vt1) higher than Vt;

a second portion of the array of cells can be set to a second initial state which is also higher than Vt, and can be programmed to said same second single binary logic state (1 or 0 ) as programmed in said first portion at a second threshold voltage (Vt2) which is higher than Vt1; and

the programming control circuit is configured to perform a reset operation which can set each cell in a respective portion of the array to a reference state equal to a prior programming state threshold voltage (Vt1 or Vt2) before programming such cell to a new threshold voltage.

20. The memory device of claim 19 further including a third portion of the array of cells that can be set to a third initial threshold voltage (VtB1) and can be programmed to a single trinary logic state (−

1, 0 or

     1) at a fourth threshold voltage (VtB2) and at a fifth threshold voltage (VtB3), where VtB3>

VtB2>

VtB1.

21. The device of claim 19 wherein said reset operation effectuates a pseudo erase of a prior state of cells without removing charge from such cells.

22. The device of claim 19 wherein said device can store at least three different logic states using three different threshold voltages.

23. The device of claim 19 wherein the cells include a multi-level cell that can be operated by said programming control circuit as a single bit cell with a different program threshold voltage during each programming cycle.

24. The device of claim 19 wherein said programming control circuit performs said reset operation automatically at programmable predetermined time intervals as part of a security feature of such device.