One-time programmable bitcell with diode under anti-fuse

• US 10,529,436 B1
• Filed: 01/16/2018
• Issued: 01/07/2020
• Est. Priority Date: 01/17/2017
• Status: Active Grant

• Current Assignee: Synopsys Incorporated
• Original Assignee: Synopsys Incorporated
• Inventors: Sargsyan, Hrant, Horch, Andrew E.
• Primary Examiner(s): Lozada, Alfredo Bermudez
• Application Number:
  US15/872,673
• Time in Patent Office: 721 Days
• CPC Class Codes: G11C 17/16 using electrically-fusible links
• CPC Class Codes: G11C 17/165 Memory cells which are electrically programmed to cause a change in resistance, e.g. to permit multiple resistance steps to be programmed rather than conduct to or from non-conduct change of fuses and antifuses digital stores using resistance random access memory elements G11C13/0002
• CPC Class Codes: G11C 17/18 Auxiliary circuits, e.g. for writing into memory
• CPC Class Codes: H01L 23/5252 comprising anti-fuses, i.e. connections having their state changed from non-conductive to conductive
• CPC Class Codes: H01L 29/0649 Dielectric regions, e.g. SiO2 regions, air gaps
• CPC Class Codes: H01L 29/0684 characterised by the shape, relative sizes or dispositions of the semiconductor regions or junctions between the regions
• CPC Class Codes: H01L 29/45 Ohmic electrodes
• CPC Class Codes: H01L 29/861 Diodes
• CPC Class Codes: H10B 20/25 One-time programmable ROM [OTPROM] devices, e.g. using electrically-fusible links

Abstract

A one-time programmable memory device includes a first doped region in a semiconductor substrate, a second doped region implanted within the first doped region, and a gate positioned over the second doped region. The first doped region and second doped regions form a diode. A first contact is coupled to the first doped region for applying a voltage to the first doped region. The gate includes a dielectric portion that is capacitively coupled to the second doped region. The gate also includes a conductive portion that is coupled to a second contact for applying a voltage to the conductive portion. The voltage applied to the conductive portion is independent from the voltage applied to the first doped region. The memory device is programmed by forming a rupture in the dielectric portion of the gate.

Claims

1. A one-time programmable memory device comprising a plurality of bitcells arranged in an array comprising rows and columns, a first bitcell of the plurality of bitcells comprising:

a first doped region implanted in a semiconductor substrate, wherein the first doped region connects the first bitcell to a first subset of the plurality of bitcells in one of the rows of the array;

a first contact coupled to the first doped region for applying a voltage to the first doped region;

a second doped region implanted within the first doped region, the first doped region and the second doped region forming a diode; and

a gate positioned over the second doped region, the gate comprising a dielectric portion capacitively coupled to the second doped region and a conductive portion, the conductive portion coupled to a second contact for applying a voltage to the conductive portion, the voltage applied to the conductive portion independent from the voltage applied to the first doped region, the first bitcell programmed by forming a rupture in the dielectric portion of the gate, wherein the gate connects the first bitcell to a second subset of the plurality of bitcells in one of the columns of the array,

wherein, in response to reverse biasing the diode formed by the first doped region and the second doped region, the voltage of the second doped region is based on a reverse bias diode leakage and a tunneling current through the dielectric portion of the gate.

2. The one-time programmable memory device of claim 1, wherein the second doped region is floating.

3. The one-time programmable memory device of claim 1, wherein the second doped region extends across a width of the gate, the second doped region separating the gate from the first doped region.

4. The one-time programmable memory device of claim 1, wherein the first bitcell is read by forward biasing the diode formed by the first doped region and the second doped region.

5. The one-time programmable memory device of claim 1, wherein the first bitcell is programmed by applying a rupture voltage to the second contact, which causes the diode formed by the first doped region and the second doped region to be forward biased.

6. The one-time programmable memory device of claim 1, wherein the one of the columns is isolated from at least one adjacent column by shallow trench isolation, and the one of the rows is isolated from at least one adjacent row by one of a third doped region and a deep trench.

7. The one-time programmable memory device of claim 1, wherein the memory device is fabricated by a bipolar process, a complementary metal-oxide-semiconductor (CMOS) process, or a double-diffused metal-oxide-semiconductor (DMOS) process, and the first doped region is a high voltage well.

8. A one-time programmable memory device comprising a plurality of bitcells, a first bitcell of the plurality of bitcells comprising:

a first doped region implanted in a semiconductor substrate;

a first contact coupled to the first doped region for applying a voltage to the first doped region;

a second doped region implanted within the first doped region, the first doped region and the second doped region forming a diode; and

a gate positioned over the second doped region, the gate comprising a dielectric portion capacitively coupled to the second doped region and a conductive portion, the conductive portion coupled to a second contact for applying a voltage to the conductive portion, the voltage applied to the conductive portion independent from the voltage applied to the first doped region, the first bitcell programmed by forming a rupture in the dielectric portion of the gate,

wherein the second doped region is a lightly-doped drain, and a salicide is blocked from forming on the second doped region.

9. The one-time programmable memory device of claim 8, wherein the second doped region is floating.

10. The one-time programmable memory device of claim 8, wherein the second doped region extends across a width of the gate, the second doped region separating the gate from the first doped region.

11. The one-time programmable memory device of claim 8, wherein the first bitcell is read by forward biasing the diode formed by the first doped region and the second doped region.

12. The one-time programmable memory device of claim 8, wherein the first bitcell is programmed by applying a rupture voltage to the second contact, which causes the diode formed by the first doped region and the second doped region to be forward biased.

13. A non-transitory computer-readable storage medium storing a digital representation of a one-time programmable memory device, the one-time programmable memory device comprising a plurality of bitcells arranged in an array comprising rows and columns, a first bitcell of the plurality of bitcells comprising:

a first doped region implanted in a semiconductor substrate, wherein the first doped region connects the first bitcell to a first subset of the plurality of bitcells in one of the rows of the array;

a first contact coupled to the first doped region for applying a voltage to the first doped region;

a second doped region implanted within the first doped region, the first doped region and the second doped region forming a diode; and

a gate positioned over the second doped region, the gate comprising a dielectric portion capacitively coupled to the second doped region and a conductive portion, the conductive portion coupled to a second contact for applying a voltage to the conductive portion, the voltage applied to the conductive portion independent from the voltage applied to the first doped region, the first bitcell programmed by forming a rupture in the dielectric portion of the gate, wherein the gate connects the first bitcell to a second subset of the plurality of bitcells in one of the columns of the array,

wherein, in response to reverse biasing the diode formed by the first doped region and the second doped region, the voltage of the second doped region is based on a reverse bias diode leakage and a tunneling current through the dielectric portion of the gate.

14. The non-transitory computer-readable storage medium of claim 13, wherein the second doped region is floating.

15. The non-transitory computer-readable storage medium of claim 13, wherein the second doped region extends across a width of the gate, the second doped region separating the gate from the first doped region.

16. The non-transitory computer-readable storage medium of claim 13, wherein the first bitcell is read by forward biasing the diode formed by the first doped region and the second doped region.

17. The non-transitory computer-readable storage medium of claim 13, wherein the first bitcell is programmed by applying a rupture voltage to the second contact, which causes the diode formed by the first doped region and the second doped region to be forward biased.

18. The non-transitory computer-readable storage medium of claim 13, wherein second doped region is a lightly-doped drain, and a salicide is blocked from forming on the second doped region.

19. The non-transitory computer-readable storage medium of claim 13, wherein the one of the columns is isolated from at least one adjacent column by shallow trench isolation, and the one of the rows is isolated from at least one adjacent row by one of a third doped region and a deep trench.

20. The non-transitory computer-readable storage medium of claim 13, wherein the memory device is fabricated by a bipolar process, a complementary metal-oxide-semiconductor (CMOS) process, or a double-diffused metal-oxide-semiconductor (DMOS) process, and the first doped region is a high voltage well.