# US 12,216,806 B2 · Semiconductor device with self-lock security and associated methods and systems

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- Number: US 12,216,806 B2
- Document ID: US12216806B2
- Status: Granted
- Kind: B2
- Application number: 17/982,403
- Filed: 2022-11-07
- Published: 2023-03-09
- Granted: 2025-02-04
- Earliest claimed: 2019-11-07
- Assignees: Micron Technology, Inc.
- Applicants: Micron Technology, Inc.
- Inventors: Nathaniel J. Meier; Brenton P. Van Leeuwen
- Web page: https://patentgrep.com/patent/US12216806B2

## CPC

- G06F 21/79: in semiconductor storage media, e.g. directly-addressable memories
- G06F 21/44: Program or device authentication
- G06F 21/554: {involving event detection and direct action}
- G06F 21/74: operating in dual or compartmented mode, i.e. at least one secure mode
- G11C 7/24: Memory cell safety or protection circuits, e.g. arrangements for preventing inadvertent reading or writing; Status cells; Test cells
- G11C 16/22: Safety or protection circuits preventing unauthorised or accidental access to memory cells
- G06F 12/1433: {for a module or a part of a module}
- G06F 2212/1052: Security improvement
- G11C 17/18: Auxiliary circuits, e.g. for writing into memory
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- G11C: STATIC STORES (semiconductor memory devices H10B)

## Abstract

Memory devices, systems including memory devices, and methods of operating memory devices are described, in which self-lock security may be implemented to control access to a fuse array (or other secure features) of the memory devices based on a predefined event associated with the memory device operation. The predefined event may include an operating parameter of the memory device, one or more commands directed to the memory device, or both. The memory device may monitor the predefined event and determine that the predefined event satisfies a threshold. The threshold may be related to a time elapsed since the predefined event has occurred or a certain pattern in the one or more commands. Subsequently, the memory device may disable a circuit configured to access the fuse array based on the determination such that an access to the fuse array is no longer allowed.

## Claims

### Claim 1

A method of operating a memory device, comprising:
monitoring a predefined event associated with the memory device;
counting a quantity of clock cycles in response to an instance of the predefined event;
pausing counting the quantity of clock cycles when a circuit is activated to access the fuse array of the memory device;
determining that the predefined event satisfies a threshold; and
temporarily disabling the circuit configured based on the determination.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
storing a quantity of one or more instances of the predefined event in the memory device based on monitoring the predefined event.

### Claim 3 (depends on 2)

The method of claim 2, further comprising:
comparing the stored quantity of one or more instances with the threshold; and
determining the quantity of one or more instances is greater than or equal to the threshold.

### Claim 4 (depends on 1)

The method of claim 1, further comprising:
storing the quantity of clock cycles in the memory device.

### Claim 5 (depends on 4)

The method of claim 4, further comprising:
comparing the stored quantity of clock cycles with the threshold; and
determining the quantity of clock cycles is greater than or equal to the threshold.

### Claim 6 (depends on 1)

The method of claim 1, further comprising:
resuming counting the quantity of clock cycles when the circuit is deactivated after accessing the fuse array of the memory device.

### Claim 7 (depends on 1)

The method of claim 1, wherein:
the predefined event corresponds to a specific sequence of commands directed to the memory device; and
the threshold comprises one or more instances of the specific sequence of commands.

### Claim 8 (depends on 1)

The method of claim 1, wherein:
the predefined event corresponds to a voltage supplied to the memory device exceeding a portion of an operating voltage of the memory device; and
the threshold comprises a fixed duration for the voltage exceeding the portion of the operating voltage.

### Claim 9 (depends on 1)

The method of claim 1, wherein:
the predefined event comprises a command directed to the memory device; and
the threshold comprises a fixed duration after the command is executed by the memory device.

### Claim 10

A memory device, comprising:
a circuit configured to access a fuse array of the memory device;
an access control module coupled to the circuit and configured to:
monitor for a predefined event;
count a quantity of clock cycles in response to an instance of the predefined event;
pause counting the quantity of clock cycles when the circuit is activated to access the fuse array of the memory device;
determine the predefined event satisfies a threshold; and
temporarily disable the circuit when the predefined event associated with the memory device satisfies the threshold.

### Claim 11 (depends on 10)

The memory device of claim 10, further comprising:
one or more registers to store a quantity of one or more instances of the predefined event or the counted quantity of clock cycles in response to one or more instances of the predefined event.

### Claim 12 (depends on 11)

The memory device of claim 11, wherein the access control module is configured to compare the stored quantity of one or more instances of the predefined event or the stored quantity of clock cycles with the threshold.

### Claim 13 (depends on 10)

The memory device of claim 10, wherein the predefined event comprises one or more operating parameters of the memory device, one or more commands directed to the memory device, or both.

### Claim 14

A method of operating a memory device, comprising:
monitoring a predefined event associated with the memory device;
counting a quantity of clock cycles in response to an occurrence of the predefined event;
determining a voltage supplied to the circuit is greater than an operating voltage of the memory device;
pausing counting the quantity of clock cycles based on the determination,
determining that a fixed duration has lapsed after the occurrence of the predefined event based on counting the quantity of clock cycles; and
temporarily disabling a circuit of the memory device configured to access a fuse array of the memory device based on the determination.

### Claim 15 (depends on 14)

The method of claim 14, wherein the predefined event corresponds to a voltage supplied to the memory device exceeding a portion of an operating voltage of the memory device.

### Claim 16 (depends on 14)

The method of claim 14, wherein the predefined event corresponds to a specific sequence of commands directed to the memory device.

### Claim 17 (depends on 14)

The method of claim 14, wherein the predefined event corresponds to a command that programs a mode register of the memory device.

### Claim 18 (depends on 14)

The method of claim 14, wherein the predefined event corresponds to a combination of a subset of the one or more commands and a predetermined time span after completing the subset of the one or more commands.

### Claim 19 (depends on 14)

The method of claim 14, wherein disabling the circuit of the memory device allows reading the fuse array of the memory device.