STRUCTURE FOR HIGH VOLTAGE DEVICE AND CORRESPONDING INTEGRATION PROCESS

• US 20110049638A1
• Filed: 08/25/2010
• Published: 03/03/2011
• Est. Priority Date: 09/01/2009
• Status: Abandoned Application

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: SAGGIO, Mario Giuseppe, MURABITO, Domenico, MAGRI', Angelo
• Application Number:
  US12/868,023
• Publication Number:
  US 20110049638A1
• Time in Patent Office: Days
• US Class Current: 257/368
• CPC Class Codes: H01L 27/088 the components being field-effect transistors with insulated gate
• CPC Class Codes: H01L 29/0634 Multiple reduced surface field (multi-RESURF) structures, e.g. double RESURF, charge compensation, cool, superjunction (SJ), 3D-RESURF, composite buffer (CB) structures
• CPC Class Codes: H01L 29/0649 Dielectric regions, e.g. SiO2 regions, air gaps
• CPC Class Codes: H01L 29/086 Impurity concentration or distribution
• CPC Class Codes: H01L 29/1095 Body region, i.e. base region, of DMOS transistors or IGBTs cell layout H01L29/0696
• CPC Class Codes: H01L 29/41766 with at least part of the source or drain electrode having contact below the semiconductor surface, e.g. the source or drain electrode formed at least partially in a groove or with inclusions of conductor inside the semiconductor H01L29/41733 - H01L29/41758 take precedence
• CPC Class Codes: H01L 29/66712 Vertical DMOS transistors, i.e. VDMOS transistors
• CPC Class Codes: H01L 29/7395 Vertical transistors, e.g. vertical IGBT
• CPC Class Codes: H01L 29/7802 Vertical DMOS transistors, i.e. VDMOS transistors
• CPC Class Codes: H01L 29/7811 with an edge termination structure guard regions per se H01L29/0619; field plates per se H01L29/402

Abstract

An embodiment of a structure for a high voltage device of the type which comprises at least a semiconductor substrate being covered by an epitaxial layer of a first type of conductivity, wherein a plurality of column structures are realized, which column structures comprises high aspect ratio deep trenches, said epitaxial layer being in turn covered by an active surface area wherein said high voltage device is realized, each of the column structures comprising at least an external portion being in turn realized by a silicon epitaxial layer of a second type of conductivity, opposed than said first type of conductivity and having a dopant charge which counterbalances the dopant charge being in said epitaxial layer outside said column structures, as well as a dielectric filling portion which is realized inside said external portion in order to completely fill said deep trench.

Claims

1. Structure for a high voltage device of the type which comprises at least a semiconductor substrate being covered by an epitaxial layer of a first type of conductivity, wherein a plurality of column structures are realized, which column structures comprise high aspect ratio deep trenches, said epitaxial layer being in turn covered by an active surface area wherein said high voltage device is realized, wherein each of the column structures comprises at least an external portion being in turn realized by a silicon epitaxial layer of a second type of conductivity, opposed than said first type of conductivity and having a dopant charge which counterbalances the dopant charge being in said epitaxial layer outside said column structures, as well as a dielectric filling portion which is realized inside said external portion in order to completely fill said deep trench.

2. Structure for a high voltage device according to claim 1, wherein said epitaxial layer of said external portion is U-shaped and extends both on the wall and on the bottom of a corresponding column structure.

3. Structure for a high voltage device according to claim 2, wherein said external portion has a dopant concentration with a constant concentration dopant profile and with a transition zone towards said epitaxial layer outside said column structures having a smaller size than a thickness of a silicon epitaxial layer of said external portion.

4. Structure for a high voltage device according to claim 2, wherein said external portion has a dopant concentration with a growing dopant profile towards an interface with said epitaxial layer outside said column structures.

5. Structure for a high voltage device according to claim 4, wherein said external portion has a dopant concentration with a substantially constant concentration dopant profile.

6. Structure for a high voltage device according to claim 4, wherein said external portion has a dopant concentration with a variable concentration profile having a maximum near said interface with said epitaxial layer.

7. Structure for a high voltage device according to claim 2, wherein the thickness of said external portion is constant along its whole U-shaped profile.

8. Structure for a high voltage device according to claim 1, wherein said column structures have a ratio between width and height less than 3/20.

9. Structure for a high voltage device according to claim 1, wherein said column structures realize a first active area of said high voltage device and in that said high voltage device comprises at least a second active area which is realized in said active surface area and has at least one fastening zone with said first active area.

10. Structure for a high voltage device according to claim 9, wherein said first active area is fastened in correspondence with said fastening zone to a conduction portion of said first active area.

11. Structure for a high voltage device according to claim 9, wherein said conduction portion of said first active area is an external portion of said column structures.

12. Structure for a high voltage device according to claim 8, wherein said high voltage device is a MOS transistor of the Multi Drain type and in that said first active area is a drain area comprising said epitaxial layer and said column structures and in that said second active area is a body area.

13. Structure for a high voltage device according to claim 12, wherein said high voltage device comprises, in said active surface area, a plurality of body wells of said second type of conductivity, inside which corresponding plurality of source wells of said first type of conductivity are realized, as well as a plurality of gate structures, being realized between consecutive pairs of column structures, above a channel region being define in said epitaxial layer between said body wells and in contact with said source wells.

14. Structure for a high voltage device according to claim 13, it further comprising a capping layer, being realized on said high voltage device and in particular covering said gate structures.

15. Structure for a high voltage device according to claim 13, wherein said gate structures are chosen between planar type and trench gate type structures.

16. Structure for a high voltage device according to claim 13, it further comprising contact surface structures being chosen between microtrench type or conventional structures.

17. Structure for a high voltage device according to claim 8, wherein said column structures have a same periodicity with respect to said second active areas.

18. Structure for a high voltage device according to claim 1, wherein each of said column structures has a width between about 1.5 and 4 um, for example about 2 um and a height between about 10 and 70 um, for example about 30 um.

19. Structure for a high voltage device according to claim 1, wherein said external portion has a dopant concentration between about 1e¹⁵ and 1e¹⁷, for example about 1e¹⁶ at/cm3 and said epitaxial layer has a dopant concentration between about 5e¹⁴ and 5e¹⁶, for example about 5e¹⁵.

20. Structure for a high voltage device according to claim 1, wherein said column structures have a distance between about 2 um and 8 um, for example about 4 um.

21. Structure for a high voltage device according to claim 1, wherein said column structures extend down to said semiconductor substrate.

22. Structure for a high voltage device according to claim 1, wherein said column structures extend down to a prefixed distance from said semiconductor substrate.

23. Structure for a high voltage device according to claim 1, wherein said high voltage device is chosen between a MOS transistor, a diode and an IGBT device.

24. Integration process of a structure for a high voltage device of the type which comprises the steps of:

realizing a semiconductor substrate having a first conductivity type;

epitaxially growing on said semiconductor substrate an epitaxial layer having said first conductivity type; and

realizing in said epitaxial layer at least one deep trench having a high aspect ratio in order to realize at least one column structure in said epitaxial layer;

an epitaxial growing step within said trench of a silicon layer being doped and having a second conductivity type, opposed than said first conductivity type and having a dopant charge which counterbalances a dopant charge being in said epitaxial layer outside said column structures and

a filling step of said trench by means of a filling dielectric layer in order to realize a filling portion of said at least one column structure.

25. Integration process according to claim 24, wherein said epitaxial growing step within said trench grows said silicon layer at least on the walls and on the bottom of said trench thus realizing an U-shaped external portion of said at least one column structure.

26. Integration process according to claim 24, wherein said epitaxial growing steps of said epitaxial layer on said semiconductor substrate and of said epitaxial layer within said trench are realized with a limited thermal budget and with a process maximum temperature less than 1100°

C.

27. Integration process according to claim 26, wherein said epitaxial growing steps realize said epitaxial layer within said trench with a dopant concentration comprised between about 1e¹⁵ and 1e¹⁷, for example about 1e¹⁶ at/cm3, and said epitaxial layer on said semiconductor substrate with a dopant concentration comprised between about 5e ¹⁴ and 5e¹⁶, for example about 5e¹⁵.

28. Integration process according to claim 24, wherein said column structures realize a first active area of said high voltage device and in that if further comprises a step of realizing, in an active surface area of said structure, at least one second active area which has at least one fastening zone with said first active area.

29. Integration process according to claim 28, further comprising integrating a MOS transistor of the multi-drain type, by realizing, as the first active area, a drain area which comprises said epitaxial layer and said column structures and, as the second active area, a body area.

30. Integration process according to claim 28, further comprising integrating a diode by realizing, as the first active area, a cathode area and, as the second active area, an anode area.

31. A structure, comprising:

a semiconductor layer having a first conductivity;

a first semiconductor region extending into the semiconductor layer and having a second conductivity; and

a first insulator region extending into the semiconductor region.

32. The structure of claim 31 wherein the semiconductor layer comprises an epitaxial layer.

33. The structure of claim 31 wherein the first conductivity comprises an N-type conductivity.

34. The structure of claim 31 wherein the semiconductor region comprises an epitaxial region.

35. The structure of claim 31 wherein the second conductivity comprises a P-type conductivity.

36. The structure of claim 31 wherein the insulator region comprises an oxide.

37. The structure of claim 31 wherein:

the semiconductor layer has a layer surface;

the semiconductor region extends into the semiconductor layer from an opening in the layer surface, and has a region surface; and

the insulator region extends into the semiconductor region from an opening in the region surface.

38. The structure of claim 31, further comprising:

wherein the semiconductor layer has a surface and forms a drain;

a body region of the second conductivity disposed in the semiconductor layer adjacent to the semiconductor region and the surface;

a source region of the first conductivity disposed in the body region adjacent to the surface;

a gate insulator disposed over the body region; and

a gate disposed over the gate insulator.

39. The structure of claim 31, further comprising:

wherein the semiconductor layer has a surface and forms a drain;

a body region of the second conductivity disposed in the semiconductor layer and adjacent to the semiconductor region and the surface;

a body extension region of the second conductivity disposed in the semiconductor region adjacent to the body region;

a source region of the first conductivity disposed in the body region adjacent to the surface;

a gate insulator disposed over the body region; and

a gate disposed over the gate insulator.

40. The structure of claim 31, further comprising:

wherein the semiconductor layer has a surface and forms a drain;

a body region of the second conductivity disposed in the semiconductor layer and adjacent to the semiconductor region and the surface;

a body-extension region of the second conductivity disposed in the semiconductor region adjacent to the body region;

a source region of the first conductivity disposed in the body region adjacent to the surface;

a gate insulator disposed over the body region;

a gate disposed over the gate insulator; and

a source contact region disposed over the surface and adjacent to the body-extension and source regions.

41. The structure of claim 31 wherein:

the semiconductor layer has a doping concentration of approximately between 5×

10¹⁴ and 5×

10¹⁶ atoms/cm³; and

the semiconductor region has a doping concentration of approximately between 1×

10¹⁵ and 1×

10¹⁷ atoms/cm³.

42. The structure of claim 31 wherein:

the semiconductor layer has a doping concentration of approximately 5×

10¹⁵ atoms/cm³; and

the semiconductor region has a doping concentration of approximately 1×

10¹⁶ atoms/cm³.

43. The structure of claim 31 wherein:

the semiconductor layer comprises a surface; and

the semiconductor region has a height from the surface of between approximately 10 and 70 μ

m.

44. The structure of claim 31 wherein:

the semiconductor layer comprises a surface; and

the semiconductor region has a height from the surface of approximately 30 μ

m.

45. The structure of claim 31 wherein the semiconductor region has a width of between approximately 1.5 and 4 μ

m.

46. The structure of claim 31 wherein the semiconductor region has a width of approximately 2 μ

m.

47. The structure of claim 31, further comprising:

a second semiconductor region extending into the semiconductor layer and having a second conductivity; and

a second insulator region extending into the second semiconductor region.

48. The structure of claim 47, further comprising:

wherein the semiconductor layer has a surface and forms a drain;

a first body region of the second conductivity disposed in the semiconductor layer adjacent to the first semiconductor region and the surface;

a first source region of the first conductivity disposed in the first body region adjacent to the surface;

a first gate insulator disposed over the first body region;

a first gate disposed over the gate insulator;

a second body region of the second conductivity disposed in the semiconductor layer adjacent to the second semiconductor region and the surface;

a second source region of the first conductivity disposed in the second body region adjacent to the surface;

a second gate insulator disposed over the second body region; and

a second gate disposed over the second gate insulator.

49. The structure of claim 47 wherein the first and second semiconductor regions are spaced apart by approximately 2 to 8 μ

m.

50. The structure of claim 47 wherein the first and second semiconductor regions are spaced apart by approximately 4 μ

m.

51. The structure of claim 47 wherein the first and second insulator regions are spaced apart by approximately 2.5 to 12 μ

m.

52. The structure of claim 47 wherein the first and second insulator regions are spaced apart by approximately 6 μ

m.

53. The structure of claim 31, further comprising:

wherein the semiconductor layer has a surface and forms a drain;

a first body region of the second conductivity disposed in the semiconductor layer adjacent to the semiconductor region and the surface;

a first source region of the first conductivity disposed in the first body region adjacent to the surface;

a first gate insulator disposed over the first body region;

a first gate disposed over the first gate insulator;

a second body region of the second conductivity disposed in the semiconductor layer adjacent to the first semiconductor region and the surface;

a second source region of the first conductivity disposed in the second body region adjacent to the surface;

a second gate insulator disposed over the second body region; and

a second gate disposed over the second gate insulator.

54. The structure of claim 31, further comprising:

wherein the semiconductor layer has a surface and forms a drain;

a first body region of the second conductivity disposed in the semiconductor layer adjacent to the semiconductor region and the surface;

a first body-extension region of the second conductivity disposed in the semiconductor region adjacent to the first body region;

a first source region of the first conductivity disposed in the first body region adjacent to the surface;

a first gate insulator disposed over the first body region;

a first gate disposed over the first gate insulator;

a second body region of the second conductivity disposed in the semiconductor layer adjacent to the first semiconductor region and the surface;

a second body-extension region of the second conductivity disposed in the semiconductor region adjacent to the second body region;

a second source region of the first conductivity disposed in the second body region adjacent to the surface;

a second gate insulator disposed over the second body region; and

a second gate disposed over the second gate insulator.

55. The semiconductor structure of claim 31, further comprising a doping transition region disposed between the semiconductor layer and the first semiconductor region.

56. The semiconductor structure of claim 31 wherein the first semiconductor region has an approximately constant doping profile between the semiconductor layer and the first insulator region.

57. The semiconductor structure of claim 31 wherein the first semiconductor region has a varying doping profile between the semiconductor layer and the first insulator region.

58. An integrated circuit, comprising:

a semiconductor layer having a first conductivity; and

an electronic device, comprising;

a first semiconductor region extending into the semiconductor layer and having a second conductivity; and

a first insulator region extending into the semiconductor region.

59. A system, comprising:

a first integrated circuit, comprising;

a semiconductor layer having a first conductivity; and

an electronic device, comprising;

a first semiconductor region extending into the semiconductor layer and having a second conductivity; and

a first insulator region extending into the semiconductor region; and

a second integrated circuit coupled to the first integrated circuit.

60. The system of claim 59 wherein the first and second integrated circuits are disposed on a same die.

61. The system of claim 59 wherein the first and second integrated circuits are disposed on respective dies.

62. The system of claim 59 wherein the second integrated circuit comprises a controller.

63. A method, comprising:

forming a first trench in a first semiconductor layer having a first conductivity;

lining a wall of the first trench with a second semiconductor layer having a second conductivity; and

forming a first insulator region in the lined first trench.

64. The method of claim 63, further comprising epitaxially growing the first semiconductor layer over a substrate.

65. The method of claim 63, further comprising epitaxially growing the second semiconductor layer over the first semiconductor layer.

66. The method of claim 63, further comprising:

forming a body region of the second conductivity in the first semiconductor layer adjacent to the trench;

forming a source region of the first conductivity in the body region;

forming a gate insulator over the body region; and

forming a gate over the gate insulator.

67. The method of claim 63, further comprising:

forming a body region of the second conductivity in the first semiconductor layer adjacent to the trench; and

forming a body-region extension of the second conductivity in the second semiconductor layer adjacent to the body region.

68. The method of claim 63, further comprising forming a body region of the second conductivity in the first and second semiconductor layers adjacent to a surface of the first semiconductor layer.

69. The method of claim 63, further comprising:

forming a second trench in the first semiconductor layer;

lining a wall of the second trench with a third semiconductor layer having the second conductivity; and

forming a second insulator region in the lined second trench.

70. The method of claim 63, further comprising:

wherein lining the wall of the first trench comprises lining the wall of the first trench with a first portion of the second semiconductor layer;

forming a second trench in the first semiconductor layer;

lining a wall of the second trench with a second portion of the second semiconductor layer; and

forming a second insulator region in the lined second trench.