Electrically decoupled integrated transformer having at least one grounded electric shield

• US 20060202789A1
• Filed: 05/10/2006
• Published: 09/14/2006
• Est. Priority Date: 12/15/2003
• Status: Active Grant

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Hyvonen, Lassi Pentti Olavi
• Granted Patent: US 7,733,205 B2
• Time in Patent Office: Days
• US Class Current: 336/200
• CPC Class Codes: H01F 17/0013 with stacked layers
• CPC Class Codes: H01F 2027/348 Preventing eddy currents
• CPC Class Codes: H01F 27/36 Electric or magnetic shields or screens movable for varying inductance H01F21/10
• CPC Class Codes: H01F 27/363 made of electrically conductive material
• CPC Class Codes: H01L 23/5225 Shielding layers formed together with wiring layers
• CPC Class Codes: H01L 23/5227 Inductive arrangements or effects of, or between, wiring layers other inductive arrangements H01L23/645
• 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 2924/3011 Impedance

Abstract

An integrated circuit, such as a radio frequency integrated circuit (RFIC), has a first layer bearing first metallization patterned for defining a first inductive coil, a second layer bearing second metallization patterned for defining a second inductive coil that overlies the first inductive coil and that is magnetically coupled to the first inductive coil through a third layer interposed between the first layer and the second layer. The third layer bears third metallization for defining an electric shield or electrostatic shield. The third metallization is patterned into a plurality of structures having shapes intended to minimize eddy currents. The electric shield is connected to further metallization that carries a ground potential. The third layer may further bear other metallization for coupling together at least two components of the integrated circuit. The integrated circuit may be fabricated by a CMOS process, and the first and second coils may be a primary coil and a secondary coil, respectively, of a radio frequency transformer. An additional electric shield may also be included, and in this case one electric shield can be coupled to a ground potential associated with the primary coil, and the second electric shield can be coupled to a ground potential associated with the secondary coil.

Claims

1-22. -22. (canceled)

23. A method to construct a planar transformer in an integrated circuit, comprising:

fabricating a first layer bearing first metallization patterned for defining a first inductive coil;

fabricating a second layer over the first layer, the second layer bearing second metallization for defining an electric shield, the second metallization being patterned into a plurality of structures having shapes intended to minimize eddy currents, where fabricating the second layer comprises fabricating an electrical connection for coupling the electric shield to a ground potential; and

fabricating a third layer over the second layer, the third layer bearing third metallization patterned for defining a second inductive coil that overlies the first inductive coil and that is magnetically coupled to the first inductive coil through the electric shield.

24. A method as in claim 23, where fabricating the second layer further comprises providing additional metallization associated with other circuitry.

25. A method as in claim 23, where fabricating the second layer comprises fabricating a fourth layer over the second layer, and where fabricating the third layer fabricates the third layer over the fourth layer, the fourth layer bearing fourth metallization for defining a second electric shield, the fourth metallization also being patterned into a plurality of structures having shapes intended to minimize eddy current, where fabricating the fourth layer comprises fabricating a second electrical connection for coupling the second electric shield to ground potential.

26. A method as in claim 25, where the electrical connection couples the electric shield to a ground potential associated with one of the first inductive coil or the second inductive coil, and where the second electrical connection couples the second electric shield to a ground potential associated with the other one of the first inductive coil or the second inductive coil.

27. A method as in claim 23 where the fabricating steps are carried out in accordance with a CMOS process, and where the integrated circuit contains radio frequency (RF) circuitry.

28. A method as in claim 27, where the electrostatic shield is patterned to form a plurality of ribbon structures, each ribbon having a width that is a function of a skin depth in the second metallization of a radio frequency of an electrical signal that is applied to said primary coil.

29. A method as in claim 28, where each ribbon is spaced apart from an adjacent ribbon by a distance that is a function of a distance between said first metallization and third second metallization.

30. A method as in claim 23, where the second metal is a non-ferrous metal.

64. A planar transformer in an integrated circuit produced by the method of claim 23.

31-36. -36. (canceled)

37. An apparatus comprising:

a first dielectric layer in an integrated circuit comprising a first inductance;

a second dielectric layer in the integrated circuit comprising a second inductance that is spaced from the first inductance and that overlies the first inductance;

an electrically conductive shield in the integrated circuit, disposed between the first and second inductances and spaced from each of the first and second inductances, for coupling a capacitance between the first and second inductance to ground.

38. The apparatus of claim 37, wherein the electrically conductive shield is a first shield, the apparatus further comprising a second electrically conductive shield disposed between the first shield and the second inductance, spaced from each of the first shield and the second inductance, and coupled to ground.

39. The apparatus of claim 38, wherein the first shield and the first inductance are coupled to a common first grounding metallization of the integrated circuit, and the second shield and the second inductance are coupled to a common second grounding metallization of the integrated circuit.

40. The apparatus of claim 37, wherein the shield couples the capacitance to ground at a location outboard of the shield.

41. The apparatus of claim 37, wherein the shield couples the capacitance to ground at a location substantially aligned with a geometric center of one of the first or second inductances.

42. The apparatus of claim 37, wherein the shield comprises a plurality of radially extending conductive shapes that are spaced from one another and electrically coupled to one another.

43. The apparatus of claim 42, wherein the shapes are electrically coupled to one another such that none of the said shapes forms a loop with any other said shape.

44. The apparatus of claim 43, wherein the radially extending conductive shapes are electrically coupled to one another by a broken ring.

45. The apparatus of claim 44, wherein the broken ring is disposed inboard of an outer periphery of the shield.

46. The apparatus of claim 43, wherein the shapes comprise ribbons.

47. The apparatus of claim 46, wherein each ribbon defines a width no greater than the distance between the shield and the nearer of the first or second inductor.

48. The apparatus of claim 46, wherein a distance between any two adjacent ribbons is no greater than half the distance between the shield and the nearer of the first or second inductor.

49. The apparatus of claim 46, wherein the ribbons define a common width, and a spacing between any two adjacent ribbons is about half the common width.

50. The apparatus of claim 46, wherein the radially extending ribbons are formed in groups of ribbons, each ribbon of a group coupled to other ribbons of the group, and each group coupled to each other group at a common connection to ground.

51. The apparatus of claim 50, wherein said common connection to ground is disposed at about a physical center of the groups.

52. The apparatus of claim 37, wherein the shield is formed of an electrically conductive non-metal.

53. The apparatus of claim 37, wherein the shield couples a capacitance between the first and second inductances to ground through use of a conductive via that penetrates at least one of the first and second dielectric layers to contact grounding metallization of the integrated circuit.

54. An apparatus comprising:

a first inductive coil;

a second inductive coil overlying the first inductive coil;

a first electric shield disposed between the first and second inductive coils; and

a second electric shield disposed between and spaced from each of the first electric shield and the second inductive coil.

55. The apparatus of claim 54, wherein each of the first and second electric shields comprises a plurality of radially extending electrically conductive ribbons coupled to one another in a manner such that no ribbon forms a loop with any other ribbon.

56. The apparatus of claim 54, wherein the first inductive coil and the first shield are grounded to a first grounding metallization, and the second conductive coil and the second shield are grounded to a second grounding metallization.

57. An integrated circuit comprising:

first means for providing an inductance; and

second means for providing an inductance overlying the first means for providing an inductance and magnetically coupled to the first means for providing an inductance through means for shielding disposed between the first and second means for providing an inductance;

wherein the means for shielding is for coupling a capacitance between the first and second means for providing an inductance to a ground potential.

58. The integrated circuit of claim 57, wherein:

the first means for providing an inductance comprises a planar first coil of conductive material disposed in a first dielectric layer;

the second means for providing an inductance comprises a planar second coil of conductive material disposed in a second dielectric layer;

the means for shielding comprises a planar conductive material patterned into a plurality of radially extending ribbons coupled to a common point that lies in a same plane as the ribbons, said point coupled to the ground potential.

59. The integrated circuit of claim 57, wherein:

the first means for providing an inductance comprises a planar first coil of conductive material disposed in a first dielectric layer;

the second means for providing an inductance comprises a planar second coil of conductive material disposed in a second dielectric layer;

the means for shielding comprises a planar conductive material patterned into a plurality of radially extending ribbons, each of said ribbons coupled to each other of said ribbons such that no ribbon forms a loop with any other ribbon.

60. The integrated circuit of claim 59, wherein the first coil is formed of a conductive metal and the second coil is formed of a conductive metal.

61. The integrated circuit of claim 59, wherein each ribbon defines a width no greater than the distance between the shield and the nearer of the first or second coil.

62. The integrated circuit of claim 59, wherein a distance between any two adjacent ribbons is no greater than half the distance between the means for shielding and the nearer of the first or second coil.

63. The integrated circuit of claim 59, wherein all ribbons define a common width, and a spacing between any two adjacent ribbons is about half the common width.

65. A transformer in an integrated circuit IC made by a process comprising:

forming a first inductor coil in or on a first IC layer;

disposing a second IC layer to overlie the first inductor;

disposing an electric shield over the second IC layer to overlie the first inductor, said electric shield patterned into a plurality of radially extending electrically conductive ribbons, each ribbon coupled to a common point;

disposing a third IC layer over the electric shield; and

forming a second inductor in or on the third IC layer to overlie the electric shield such that at least a portion of the third IC layer separates the second inductor from the electric shield;

wherein the common point is electrically coupled to grounding metallization of the IC.

66. The transformer of claim 65, wherein each of the radially extending ribbons defines a width that is a function of a frequency of an electrical signal that is to be applied to the first or second inductors.

67. The transformer of claim 65, wherein adjacent ones of said ribbons are spaced from one another by a distance that is a function of a spacing between the first and second inductors.

68. The transformer of claim 65, wherein adjacent ones of said ribbons are spaced from one another by a distance that is on the order of twice a width of said adjacent ones of said ribbons.

69. The transformer of claim 65, wherein each of the second and third IC layers comprises a dielectric material.

70. A method of making an integrated circuit, comprising:

forming in a first dielectric layer a first coil of conductive material;

disposing an electric shield to overlie the first coil and spaced therefrom,. said electric shield defining a plurality of ribbons coupled to one another such that no ribbon forms a loop with any other ribbon;

disposing a second dielectric layer to overlie the electric shield;

forming in the second dielectric layer a second coil of conductive material to overlie the first coil such that at least a portion of the second dielectric layer lies between the electric shield and the second coil; and

coupling the electric shield to grounding metallization of the integrated circuit.