METHOD AND DEVICE FOR PROTECTING AN INTEGRATED CIRCUIT AGAINST BACKSIDE ATTACKS

• US 20130314121A1
• Filed: 05/23/2013
• Published: 11/28/2013
• Est. Priority Date: 05/24/2012
• Status: Active Grant

• Current Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Inventors: Tubert, Cedric, Mougin, Stephane
• Granted Patent: US 9,117,833 B2
• Time in Patent Office: Days
• US Class Current: 326/8
• CPC Class Codes: G06F 21/86 Secure or tamper-resistant housings
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 23/576 using active circuits
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/15311 being a ball array, e.g. BGA

Abstract

A method for detecting an attack, such as by laser, on an electronic microcircuit from a backside of a substrate includes forming the microcircuit on the semiconductor substrate, the microcircuit comprising a circuit to be protected against attacks, forming photodiodes between components of the circuit to be protected, forming a circuit for comparing a signal supplied by each photodiode with a threshold value, and forming a circuit for activating a detection signal when a signal at output of one of the photodiodes crosses the threshold value.

Claims

1. A method, comprising:

forming a microcircuit on a front side of a semiconductor substrate, forming the microcircuit including forming an active layer on the front side of the substrate, forming conductive layers with conductive tracks formed on the active layer, forming insulating layers between the conductive layers, and forming in the active and conductive layers a circuit to be protected against laser beam attacks;

forming photodiodes in the active layer of the semiconductor substrate between components of the circuit to be protected, each of the photodiodes being configured to supply a respective photodiode signal representative of a light intensity received by the photodiode from a back side of the substrate opposite to the front side;

forming on the semiconductor substrate a comparison circuit configured to compare each photodiode signal with a first threshold value; and

forming on the semiconductor substrate a processing circuit configured to activate a detection signal when one of the photodiode signals crosses the first threshold value.

2. The method according to claim 1, wherein the photodiodes are configured to receive light from the back side of the substrate subsequent to a partial removal of the substrate from the back side.

3. The method according to claim 1, comprising establishing the first threshold value at a level that will be exceeded by a photodiode signal that is subjected to substantially any light intensity greater than zero.

4. The method according to claim 3, wherein forming the comparison circuit includes forming the comparison circuit configured to compare each photodiode signal with the first threshold value and a second threshold value, the method comprising establishing the second threshold value at a level that will be exceeded by a photodiode signal that is subjected to a light intensity that is consistent with a laser emission.

5. The method according to claim 1, comprising establishing the first threshold value at a level that is slightly greater than a signal produced when a photodiode is in complete darkness.

6. The method according to claim 1, comprising:

packaging the microcircuit and photodiodes in a way that prevents light from being detected by the photodiodes during normal operation of the microcircuit.

7. The method according to claim 1, comprising:

packaging the microcircuit and photodiodes in a way that prevents the photodiodes from producing a signal that exceeds the first threshold during normal operation of the microcircuit.

8. The method according to claim 1, wherein forming the photodiodes on the semiconductor substrate comprises forming the photodiodes over the circuit to be protected according to a random distribution.

9. The method according to claim 1, wherein forming the photodiodes on the semiconductor substrate comprises forming the photodiodes over the circuit to be protected according to a matrix configuration in rows and in columns.

10. The method according to claim 1, wherein forming the photodiodes on the semiconductor substrate comprises forming individual ones of the photodiodes over the circuit to be protected in close proximity with respective individual components of the circuit to be protected.

11. A microcircuit, comprising:

a semiconductor substrate;

an active layer formed on a front side of the substrate;

conductive layers formed on the active layer of the substrate, each including conductive tracks;

insulating layers formed between the conductive layers;

a circuit to be protected, formed in the active and conductive layers;

a plurality of photodiodes formed in the active layer among components of the circuit to be protected, each of the photodiodes being configured to supply respective a light intensity signal representative of a light intensity received by the photodiode from a back side of the substrate opposite to the front side; and

a detector circuit linked to the photodiodes, configured to compare the light intensity signals with a first threshold value, and to activate a detection signal when one of the light intensity signals crosses the threshold value.

12. The microcircuit according to claim 11, wherein the photodiodes are configured to receive light from the back side of the substrate subsequent to a partial removal of the substrate from the back side.

13. The microcircuit according to claim 11, wherein the detector circuit comprises a first comparator linked to the photodiodes and configured to compare each light intensity signal with the first threshold value chosen to distinguish whether the photodiode is not subjected to any light intensity or receives a light intensity.

14. The microcircuit according to claim 13, wherein the detector circuit comprises a second comparator linked to the photodiodes to compare each light intensity signal with a second threshold value chosen to distinguish whether one or more of the photodiodes receives a light intensity corresponding to an ambient light or a laser beam used to attack the microcircuit.

15. The microcircuit according to claim 11, wherein the photodiodes are distributed over the circuit to be protected of the microcircuit according to a random configuration or as close as possible to sensitive components of the circuit to be protected.

16. The microcircuit according to claim 11, wherein the photodiodes are distributed over the circuit to be protected of the microcircuit according to a matrix configuration in rows and in columns transversal to the rows.

17. A device, comprising:

a semiconductor substrate;

an active layer formed on a front side of the substrate;

conductive layers formed on the active layer of the substrate, each including conductive tracks;

insulating layers formed between the conductive layers;

a first integrated circuit formed in the active and conductive layers;

a plurality of photodiodes formed in the active layer and distributed within an area defined by the first integrated circuit, each of the photodiodes being configured to detect light applied to the photodiode from a back side of the substrate opposite to the front side;

a second integrated circuit formed in the active and conductive layers and having a plurality of inputs, each coupled to a respective one of the plurality of photodiodes, the second integrated circuit being configured to detect a level of light exceeding a first threshold that reaches any of the plurality of photodiodes from the back side of the substrate, and to produce a corresponding detection signal; and

a packaging of the first integrated circuit and plurality of diodes configured to prevent light exceeding the first threshold from reaching any of the plurality of photodiodes.

18. The device of claim 17, wherein the photodiodes are configured to receive light from the back side of the substrate subsequent to a partial removal of the substrate from the back side.

19. The device of claim 17, wherein the second integrated circuit comprises a comparator configured to compare a signal produced by one of the plurality of diodes with a first reference value that corresponds to the first threshold.

20. The device of claim 19, wherein the second integrated circuit comprises a multiplexer configured to couple each of the plurality of diodes in turn to the comparator.

21. The device of claim 19, wherein the comparator is one of a plurality of comparators comprised by the second integrated circuit each coupled to a respective one of the plurality of diodes.

22. The device of claim 17, wherein the second integrated circuit is configured to detect a level of light exceeding a second threshold, greater than the first threshold, that reaches any of the plurality of photodiodes, and to produce a detection signal corresponding to the second threshold.

23. A method, comprising:

detecting light impinging on a portion of an integrated circuit formed on a semiconductor substrate, where the detected light impinges from a backside of the substrate; and

producing a detection signal if the detected light exceeds a threshold value representing a maximum value of light that can penetrate packaging of the integrated circuit, as originally manufactured, during normal operation of the circuit.

24. The method of claim 23 wherein the producing a detection signal if the detected light exceeds a threshold value comprises producing the detection signal if any light is detected.

25. The method of claim 23 wherein the producing a detection signal if the detected light exceeds a threshold value comprises producing the detection signal indicating a degree by which the detected light exceeds the threshold.

26. The method of claim 23, comprising making irrevocable alterations to the integrated circuit if the detection signal is produced.