Integrated circuit with detection of thinning via the back face and decoupling capacitors
A semiconductor substrate has a back face and a front face and includes a semiconductor well that is electrically isolated from the semiconductor substrate. A device is configured to detect a thinning of the semiconductor substrate from the back face. The device includes at least one trench that extends within the semiconductor well between two peripheral locations from the front face down to a location situated at a distance from a bottom of the semiconductor well. The trench is electrically isolated from the semiconductor well. A detection circuit is configured to measure a physical quantity representative of well electrical resistance between two contact areas respectively situated on either side of the at least one first trench.
1. A method for detecting a thinning of a semiconductor substrate of an integrated circuit from a back face of the semiconductor substrate, wherein the semiconductor substrate includes an assembly of at least one semiconductor well electrically isolated from the semiconductor substrate and comprising a group of at least one first trench extending within the at least one semiconductor well between two locations on a periphery of the at least one semiconductor well and from a front face of the semiconductor substrate down to a location situated at a distance from the bottom of the at least one semiconductor well, the at least one first trench being electrically isolated from the at least one semiconductor well, the method comprising: measuring a physical quantity representative of an electrical resistance of the at least one semiconductor well between two contact areas respectively situated on either side of the group of at least one first trench.
2. An integrated circuit, comprising:
a semiconductor substrate having a back face and a front face and including an assembly of at least one semiconductor well electrically isolated from the semiconductor substrate; and
a device configured to detect a thinning of the semiconductor substrate from the back face, comprising:
a group of at least one first trench extending within the at least one semiconductor well between two locations on a periphery of the at least one semiconductor well and from the front face down to a location situated at a distance from a bottom of the at least one semiconductor well, the at least one first trench being electrically isolated from the at least one semiconductor well; and
a detection circuit configured to measure a physical quantity representative of an electrical resistance of the at least one semiconductor well between two contact areas respectively situated on either side of the group of at least one first trench.
3. The integrated circuit according to claim 2 , wherein the detection circuit comprises a biasing circuit configured to apply a potential difference between the two contact areas and a measurement circuit configured to measure a current flowing between the two contact areas.
4. The integrated circuit according to claim 2 , wherein the at least one first trench is totally insulating.
5. The integrated circuit according to claim 2 , wherein the group comprises several first trenches.
6. The integrated circuit according to claim 2 , wherein the at least one semiconductor well comprises several semiconductor wells.
7. The integrated circuit according to claim 6 , further comprising a coupling circuit configured for electrically coupling in series two semiconductor wells of said several semiconductor wells so as to form a chain of semiconductor wells electrically coupled in series, the coupling circuit being disposed between two groups of at least one first trench respectively extending into the two semiconductor wells, and wherein the two contact areas are respectively situated on either side of the two groups of at least one first trench respectively extending into the two semiconductor wells respectively situated at two ends of the chain, the detection circuit configured to measures a physical quantity representative of the electrical resistance of the chain of semiconductor wells between the two contact areas.
8. The integrated circuit according to claim 2 , wherein the integrated circuit is a part of an object.
9. The integrated circuit according to claim 8 , wherein the object is a smartcard.
10. The integrated circuit according to claim 2 , wherein the semiconductor substrate and the at least one semiconductor well are of a P type of conductivity, and wherein the at least one semiconductor well is electrically isolated from the semiconductor substrate by an isolation region comprising:
a peripheral isolation trench extending into the semiconductor substrate from the front face and surrounding the at least one semiconductor well,
a semiconductor layer of the N type of conductivity buried in the semiconductor substrate under the at least one semiconductor well, and
an intermediate peripheral insulating region surrounding the at least one semiconductor well and configured to ensure a continuity of electrical isolation between the buried semiconductor layer and the peripheral isolation trench, and
wherein the at least one first trench extends at least between two locations of the peripheral isolation trench.
11. The integrated circuit according to claim 10 , wherein the isolation region comprises an additional peripheral trench having at least one insulating envelope, extending from the front face through the peripheral isolation trench and having a lower part extending under this peripheral isolation trench to makes contact with the buried semiconductor layer.
12. The integrated circuit according to claim 11 , wherein the at least one first trench extends between two locations of the additional peripheral trench.
13. The integrated circuit according to claim 11 , in which the additional peripheral trench is totally insulating.
14. The integrated circuit according to claim 10 , wherein the isolation region comprises an additional peripheral trench having at least one insulating envelope, extending from the front face through the peripheral isolation trench and having a lower part extending under this peripheral isolation trench at a distance from the buried semiconductor layer, and an implanted region of the N type of conductivity situated between a lower part and the buried semiconductor layer.
15. The integrated circuit according to claim 14 , wherein the at least one first trench extends between two locations of the additional peripheral trench.
16. The integrated circuit according to claim 14 , wherein the additional peripheral trench is totally insulating.
17. An integrated circuit, comprising:
a semiconductor substrate having a back face and a front face and including an assembly of several semiconductor wells electrically isolated from the semiconductor substrate;
a group of at least one first trench extending within each semiconductor well between two locations on a periphery of the semiconductor well and from the front face down to a location situated at a distance from a bottom of the semiconductor well, the at least one first trench being electrically isolated from the semiconductor well;
a coupling circuit configured to electrically couple two semiconductor wells of the assembly of several semiconductor wells in series so as to form a chain of semiconductor wells electrically coupled in series, the coupling circuit being disposed between two groups of at least one first trench respectively extending within the two semiconductor wells; and
two contact areas respectively situated on either side of the two groups of at least one first trench respectively extending into the two semiconductor wells respectively situated at two ends of the chain, so as to form a resistive circuit extending between the two contact areas.
18. The integrated circuit according to claim 17 , wherein the semiconductor substrate and the at least one semiconductor well are of a P type of conductivity, and wherein the at least one semiconductor well is electrically isolated from the semiconductor substrate by an isolation region comprising:
a peripheral isolation trench extending into the semiconductor substrate from the front face and surrounding the at least one semiconductor well,
a semiconductor layer of the N type of conductivity buried in the semiconductor substrate under the at least one semiconductor well, and
an intermediate peripheral insulating region surrounding the at least one semiconductor well and configured to ensure a continuity of electrical isolation between the buried semiconductor layer and the peripheral isolation trench, and
wherein the at least one first trench extends at least between two locations of the peripheral isolation trench.
19. The integrated circuit according to claim 18 , wherein the isolation region comprises an additional peripheral trench having at least one insulating envelope, extending from the front face through the peripheral isolation trench and having a lower part extending under this peripheral isolation trench to makes contact with the buried semiconductor layer.
20. The integrated circuit according to claim 19 , wherein the at least one first trench extends between two locations of the additional peripheral trench.
21. The integrated circuit according to claim 19 , in which the additional peripheral trench is totally insulating.
22. The integrated circuit according to claim 18 , wherein the isolation region comprises an additional peripheral trench having at least one insulating envelope, extending from the front face through the peripheral isolation trench and having a lower part extending under this peripheral isolation trench at a distance from the buried semiconductor layer, and an implanted region of the N type of conductivity situated between a lower part and the buried semiconductor layer.
23. The integrated circuit according to claim 22 , wherein the at least one first trench extends between two locations of the additional peripheral trench.
24. The integrated circuit according to claim 22 , wherein the additional peripheral trench is totally insulating.
25. The integrated circuit according to claim 22 , wherein the additional peripheral trench and the at least one first trench each comprise an electrically conducting central region surrounded by an insulating envelope.
26. The integrated circuit according to claim 25 , wherein the group comprises several parallel first trenches connecting two opposing edges of the additional peripheral trench.
27. The integrated circuit according to claim 25 , wherein the detection circuit comprise a first biasing circuit configured to apply a first potential difference between the two contact areas and a measurement circuit configured to measure a current flowing between the two contact areas, and a second biasing circuit configured to applying a second potential difference between the central region of the additional peripheral trench and the at least one semiconductor well.
28. The integrated circuit according to claim 17 , further including a memory device comprising a memory plane having non-volatile memory cells and selection transistors with buried gates, the at least one first trench having a depth substantially equal to a depth of the buried gates.
29. The integrated circuit according to claim 17 , wherein the integrated circuit is a part of an object.
30. The integrated circuit according to claim 29 , wherein the object is a smartcard.
31. The integrated circuit according to claim 17 , wherein the at least one first trench is totally insulating.
32. The integrated circuit according to claim 17 , wherein the group comprises several first trenches.