BACKSIDE ILLUMINATED IMAGING DEVICE, SEMICONDUCTOR SUBSTRATE, IMAGING APPARATUS AND METHOD FOR MANUFACTURING BACKSIDE ILLUMINATED IMAGING DEVICE

• US 20080283726A1
• Filed: 09/17/2007
• Published: 11/20/2008
• Est. Priority Date: 09/20/2006
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Nagase, Masanori, UYA, Shinji, Nakahashi, Yosuke, Hachiya, Toru
• Granted Patent: US 7,781,715 B2
• Time in Patent Office: Days
• US Class Current: 250/208.1
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/1464 Back illuminated imager structures
• CPC Class Codes: H01L 27/14812 Special geometry or disposition of pixel-elements, address lines or gate-electrodes

Abstract

A backside illuminated imaging device performs imaging by illuminating light from a back side of a p substrate to generate electric charges in the substrate based on the light and reading out the electric charges from a front side of the substrate. The device includes n layers located in the substrate and on an identical plane near a front side surface of the substrate and accumulating the electric charges; n+ layers between the respective n layers and the front side of the substrate, the n+ layers having an exposed surface exposed on the front side surface of the substrate and functioning as overflow drains for discharging unnecessary electric charges accumulated in the n layers; p+ layers between the respective n+ layers and the n layers and functioning as overflow barriers of the overflow drains; and an electrode connected to the exposed surface of each of the n+ layers.

Claims

1. A backside illuminated imaging device that performs imaging by illuminating light from a back side of a semiconductor substrate to generate electric charges in the semiconductor substrate based on the light and reading out the electric charges from a front side of the semiconductor substrate, which comprises:

a plurality of first impurity diffusion layers located in the semiconductor substrate and on an identical plane near a front side surface of the semiconductor substrate, the first impurity diffusion layers having a first conductivity and accumulating the electric charges;

a plurality of second impurity diffusion layers between the respective first impurity diffusion layers and the front side of the semiconductor substrate, the second impurity diffusion layers having an exposed surface exposed on the front side surface of the semiconductor substrate, having the first conductivity, and functioning as overflow drains for discharging unnecessary electric charges accumulated in the plurality of first impurity diffusion layers;

a plurality of third impurity diffusion layers between the respective second impurity diffusion layers and the respective first impurity diffusion layers, the third impurity diffusion layers having a second conductivity opposite to the first conductivity, and functioning as overflow barriers of the overflow drains; and

an electrode connected to the exposed surface of each of the second impurity diffusion layers.

2. The backside illuminated imaging device according to claim 1, wherein the electrode connected to the exposed surface of each of the plurality of second impurity diffusion layers is commonly connected to specific second impurity diffusion layers and is adapted to independently apply a voltage to each of the specific second impurity diffusion layers.

3. The backside illuminated imaging device according to claim 2, further comprising a color filter layer below the back side of the semiconductor substrate, wherein

the color filter layer includes a plurality of color filters corresponding to the respective second impurity diffusion layers,

the plurality of color filters are classified into a plurality of groups of color filters, the groups transmitting light of different wavelength bands, and

the specific second impurity diffusion layers corresponds to the same group of color filters.

4. The backside illuminated imaging device according to claim 2, wherein the plurality of second impurity diffusion layers are classified into a first group corresponding to the first impurity diffusion layers in which the electric charges are read out in a specific imaging mode and a second group corresponding to the first impurity diffusion layers in which the electric charges are not read out in the specific imaging mode, and all of the specific second impurity diffusion layers belongs to one of the first and second groups.

5. The backside illuminated imaging device according to claim 1, further comprising:

a diffusion prevention layer that prevents diffusion of a conductivity material constituting the electrode, the diffusion prevention layer being between the electrode and each of the second impurity diffusion layers.

6. The backside illuminated imaging device according to claim 1, wherein the electrode is made of W, Ti, Mo, or silicide thereof.

7. The backside illuminated imaging device according to claim 1, further comprising:

an insulating layer below a back side surface of the semiconductor substrate;

a fourth impurity diffusion layer inside from the back side surface of the semiconductor substrate, having the second conductivity, and having a higher concentration than the semiconductor substrate; and

a terminal that applies a voltage to the fourth impurity diffusion layer.

8. The backside illuminated imaging device according to claim 1, further comprising:

an insulating layer below a back side surface of the semiconductor substrate;

a transparent electrode below the insulating layer, the transparent electrode being transparent to the light; and

a terminal that applies a voltage to the transparent electrode.

9. The backside illuminated imaging device according to claim 1, wherein a distance from a back side surface to the front side surface of the semiconductor substrate is equal to or more than 5 μ

m.

10. The backside illuminated imaging device according to claim 9, wherein the distance is equal to or more than 10 μ

m.

11. The backside illuminated imaging device according to claim 1, which read out a signal, in a frame interline method, based on the electric charges accumulated in the first impurity diffusion

12. The backside illuminated imaging device according to claim 1, further comprising a metal oxide semiconductor circuit that read out a signal based on the electric charges accumulated in the first impurity diffusion layer.

13. The backside illuminated imaging device according to claim 1, further comprising a voltage application unit that applies to the electrode a voltage for adjusting a saturation charge amount of the first impurity diffusion layers.

14. The backside illuminated imaging device according to claim 1, further comprising a voltage application unit that applies to the electrode a voltage required to eliminate an overflow barrier in the third impurity diffusion layers.

15. The backside illuminated imaging device according to claim 1, further comprising:

a first voltage application unit that applies to the electrode a voltage for adjusting a saturation charge amount of the first impurity diffusion layers; and

a second voltage application unit that applies to the electrode a voltage required to eliminate an overflow barrier in the third impurity diffusion layers.

16. A method for manufacturing a backside illuminated imaging device according to claim 1, comprising:

forming a first impurity diffusion layer and a fifth impurity diffusion layer in the semiconductor substrate such that the fifth impurity diffusion layer is formed in a direction from the front side surface to an inner side of the semiconductor substrate and the first impurity diffusion layer is formed below the fifth impurity diffusion layer, the fifth impurity diffusion layer having the second conductivity and preventing a dark current;

forming an insulating layer on the semiconductor substrate in which the first impurity diffusion layer and the fifth impurity diffusion layer are formed;

forming an opening in a portion of the insulating layer to expose a portion of a surface of the fourth impurity diffusion layer;

forming a second impurity diffusion layer in the fifth impurity diffusion layer by self-alignment in which the insulating layer serves as a mask; and

embedding a conductivity material in the opening to form an electrode,

wherein a portion except the second impurity diffusion layer of the fifth impurity diffusion layer has a function of a third impurity diffusion layer.

17. The method according to claim 16, wherein the second impurity diffusion layer is formed by vertical ion implantation to a surface of the fifth impurity diffusion layer exposed from the opening.

18. The method according to claim 16, wherein the second impurity diffusion layer is formed by oblique ion implantation in at least four directions to a surface of the fourth impurity diffusion layer exposed from the opening.

19. The method according to claim 16, further comprising:

forming a sixth impurity diffusion layer having the second conductivity below the second impurity diffusion layer by self-alignment in which the insulating layer serves as the mask, between the forming of the second impurity diffusion layer and the forming of the electrode,

wherein a portion except the second impurity diffusion layer of the fifth impurity diffusion layer and the sixth impurity diffusion layer has a function of the third impurity diffusion layer.

20. The method according to claim 19, wherein the sixth impurity diffusion layer includes impurities having a diffusion coefficient having larger than that of impurities in the second impurity diffusion layer.

21. The method according to claim 19, wherein the sixth impurity diffusion layer is formed by vertical ion implantation to a surface of the fifth impurity diffusion layer exposed from the opening.

22. The method according to claim 19, wherein the sixth impurity diffusion layer is formed by oblique ion implantation in at least four directions to a surface of the fourth impurity diffusion layer exposed from the opening.

23. The method according to claim 16, wherein the conductivity material is tungsten.

24. A backside illuminated imaging device that performs imaging by illuminating light from a back side of a semiconductor substrate to generate electric charges in the semiconductor substrate based on the light and reading out the electric charges from a front side of the semiconductor substrate, which comprises:

a plurality of first impurity diffusion layers located in the semiconductor substrate and on an identical plane near a front side surface of the semiconductor substrate, the first impurity diffusion layers having a first conductivity and accumulating the electric charges;

a plurality of second impurity diffusion layers between the respective first impurity diffusion layers and the front side of the semiconductor substrate, the second impurity diffusion layers having the first conductivity, and functioning as overflow drains for discharging unnecessary electric charges accumulated in the plurality of first impurity diffusion layers; and

a plurality of third impurity diffusion layers between the respective second impurity diffusion layers and the respective first impurity diffusion layers, the third impurity diffusion layers having a second conductivity opposite to the first conductivity, and functioning as overflow barriers of the overflow drains,

wherein each of the second impurity diffusion layers is located in a position overlapping with a maximum potential point of the corresponding first impurity diffusion layer in plan view.

25. The backside illuminated imaging device according to claim 24, wherein the maximum potential point is in a center of the corresponding first impurity diffusion layer in the plan view.

26. The backside illuminated imaging device according to claim 24, wherein the maximum potential point is in a depth of within 0.3 μ

m from a boundary surface of the corresponding first impurity diffusion layer and the corresponding third impurity diffusion layer.

27. The backside illuminated imaging device according to claim 24, further comprising a depletion-layer extension layer for extending a depletion layer formed by each of the second impurity diffusion layers in a direction parallel to the front side surface of the semiconductor substrate the depletion-layer extension layer being located in the vicinity of each of the second impurity diffusion layers and being an impurity diffusion layer having a first conductivity and a lower concentration than that of the second impurity diffusion layers.

28. The backside illuminated imaging device according to claim 24, wherein each of the second impurity diffusion layer is a depletion layer covering ⅔

or more of the corresponding first impurity diffusion layer.

29. The backside illuminated imaging device according to claim 24, wherein each of the second impurity diffusion layers has an exposed surface exposed on the front side surface of the semiconductor substrate, the exposed surface being connected to an electrode.

30. An imaging device, comprising:

a backside illuminated imaging device according to claim 29;

a first voltage application unit that applies to the electrode a first voltage determining a saturation charge amount of the first impurity diffusion layers; and

a second voltage application unit that applies to the electrode a second voltage higher than the first voltage to eliminate the overflow barriers formed by the third impurity diffusion layers when the first voltage is applied.

31. The imaging device according to claim 30, wherein the second voltage application unit variably controls an application time of the second voltage to adjust an exposure time of the backside illuminated imaging device.

32. The imaging device according to claim 30, wherein the first voltage application unit variable controls the first voltage to adjust the saturation charge amount of the first impurity diffusion layers.

33. The imaging device according to claim 30, wherein the second voltage is determined by a value based on the first voltage.

34. The imaging device according to claim 30, wherein

the backside illuminated imaging device includes:

a vertical charge transfer device that transfers electric charges accumulated in each of the first impurity diffusion layers in a vertical direction; and

a horizontal charge transfer device that transfers the electric charges transferred from the vertical charge transfer device in a horizontal direction orthogonal to the vertical direction,

the first voltage is less than or equal to a driving voltage of the horizontal charge transfer device, and

the second voltage is less than or equal to a readout voltage for reading out the electric charges to the vertical charge transfer device.

35. The imaging device according to claim 34, wherein

the first impurity diffusion layers is classified into n groups, wherein n is a natural number of 2 or more,

an addition transfer mode in which electric charges accumulated in the respective groups are added and transferred in the vertical transfer device and a non-addition mode in which electric charges accumulated in the respective groups are transferred in the vertical transfer device without addition are set, and

the first voltage application unit variably controls the first voltage such that the saturation charge amount of the first impurity diffusion layers when the addition transfer mode is set is 1/n of the saturation charge amount of the first impurity diffusion layer determined by the first voltage to be applied to the electrode when the non-addition transfer mode is set.

36. The imaging device according to claim 34, wherein

the backside illuminated imaging device includes a source follower circuit that converts electric charges transferred from the horizontal charge transfer device into a voltage signal to output the voltage signal,

the vertical charge transfer device operates at three voltages of VH representing a highest voltage, VL representing a lowest voltage, and VM representing a voltage between VH and VL, and

the second voltage is a value computed by adding the first voltage and one of an application voltage for a drain of a transistor of a last stage of the source follower circuit, a difference between the VL and the VM, and a difference between the VH and the VM.

37. The imaging device according to claim 34, wherein the backside illuminated imaging device includes:

a charge accumulation layer that reads out and accumulates electric charges accumulated in each of the first impurity diffusion layers; and

a CMOS circuit that outputs a signal based on the electric charges accumulated in the charge accumulation layer.

38. A backside illuminated imaging device that performs imaging by illuminating light from a back side of a semiconductor substrate to generate electric charges in the semiconductor substrate based on the light and reading out the electric charges from a front side of the semiconductor substrate, which comprises:

a first semiconductor layer in the semiconductor substrate, the first semiconductor layer having a first conductivity and accumulating the electric charges;

a second semiconductor layer inside from a back side surface of the semiconductor substrate and having a second conductivity opposite to the first conductivity type; and

a third semiconductor layer between the first semiconductor layer and the second semiconductor layer, the third semiconductor layer having an impurity concentration of 1.0×

10¹⁴/cm³ or less.

39. The backside illuminated imaging device according to claim 38, wherein the third semiconductor layer is n-type or p-type and has an impurity concentration of more than 2.0×

10¹³/cm³ and less than 1.0×

10¹⁴/cm³.

46. The backside illuminated imaging device according to claim 38, wherein a thickness from a front side surface to a back side surface of the semiconductor substrate is 5 μ

m or more.

47. The backside illuminated imaging device according to claim 46, wherein the thickness is 8 μ

m or more.

40. A backside illuminated imaging device that performs imaging by illuminating light from a back side of a semiconductor substrate to generate electric charges in the semiconductor substrate based on the light and reading out the electric charges from a front side of the semiconductor substrate, which comprises:

a first semiconductor layer in the semiconductor substrate, the first semiconductor layer having a first conductivity and accumulating the electric charges;

a second semiconductor layer inside from a back side surface of the semiconductor substrate and having a second conductivity opposite to the first conductivity type;

a third semiconductor layer having the first conductivity and having an impurity concentration is 2.0×

10¹⁴/cm³ or less; and

a fourth semiconductor layer having the second conductivity and having an impurity concentration of 2.0×

10¹⁴/cm³ or less,

the third and fourth semiconductor layers being between the first semiconductor layer and the second semiconductor layer.

41. The backside illuminated imaging device according to claim 40, further comprising a fifth semiconductor layer between the third and fourth semiconductor layers, the fifth semiconductor layer having an impurity concentration of 1.0×

10¹⁴/cm³ or less.

42. A semiconductor substrate for use in a semiconductor device, comprising:

a first semiconductor layer inside from one surface of the semiconductor substrate, the first semiconductor layer having a first conductivity; and

a second semiconductor layer on the first semiconductor layer, the second semiconductor layer having an impurity concentration of 1.0×

10¹⁴/cm³ or less.

43. The semiconductor substrate according to claim 42, wherein the second semiconductor layer is n-type or p-type and has an impurity concentration of more than 2.0×

10¹³/cm³ and less than 1.0×

10¹⁴/cm³.

44. A semiconductor substrate for use in a semiconductor device, comprising:

a first semiconductor layer inside from one surface of the semiconductor substrate, the first semiconductor layer having a first conductivity;

a second semiconductor layer on the first semiconductor layer, the second semiconductor layer having the first conductivity or a second conductivity opposite to the first conductivity and having an impurity concentration of 2.0×

10¹⁴/cm³ or less; and

a third semiconductor layer on the second semiconductor layer, the third semiconductor layer having a conductivity opposite to that of the second semiconductor layer and having an impurity concentration of 2.0×

10¹⁴/cm³ or less.

45. The semiconductor substrate according to claim 44, further comprising a fourth semiconductor layer between the second and third semiconductor layers, the fourth semiconductor layer having an impurity concentration of 1.0×

10¹⁴/cm³ or less.

48. The semiconductor substrate according to claim 45, wherein a thickness from a front side surface to a back side surface of the semiconductor substrate is 5 μ

m or more.

49. The semiconductor substrate according to claim 48, wherein the thickness is 8 μ

m or more.

50. A method for manufacturing a backside illuminated imaging device that performs imaging by illuminating light from a back side of a semiconductor substrate, which is opposite to a front side of the semiconductor substrate having an electrode, to generate electric charges in the semiconductor substrate based on the light and reading out the electric charges from the front side, which comprises:

forming a photoelectric conversion region and a charge transfer portion in a conductive semiconductor layer of an SOI substrate including a first semiconductor support substrate, an insulating layer, and a conductive semiconductor layer in this order, the photoelectric conversion region including a light receiving portion, the charge transfer portion transferring signal charges generated in the photoelectric conversion region to a signal output portion;

fixing a surface of the SOI substrate opposite to the first semiconductor support substrate to a second semiconductor support substrate;

removing the first semiconductor support substrate from the SOI substrate; and

performing ion implantation for gettering into the conductive semiconductor layer of the SOI substrate.

51. The method according to claim 50, further comprising removing the insulating layer formed on the conductive semiconductor layer before the performing of the ion implantation.

52. The method according to claim 51, further comprising forming a protection film on the conductive semiconductor layer from which the insulating layer is removed, wherein the performing of the ion implantation is a process of implanting ions into the conductive semiconductor layer through the protection film.

53. The method according to claim 50, wherein the ion implantation is performed with an ion of one selected of the group consisting of carbon, oxygen, fluorine, silicon, hydrogen, and nitride.

54. The method according to claim 50, further comprising performing a low-temperature anneal treatment in an environment of 500°

C. or less after the performing of the ion implantation.

55. A backside illuminated imaging device that performs imaging by illuminating light from a back side of a semiconductor substrate, which is opposite to a front side of the semiconductor substrate having an electrode, to generate electric charges in the semiconductor substrate based on the light and reading out the electric charges from the front side, which comprises.

a photoelectric conversion region an a charge transfer portion on the front side of the semiconductor substrate, the photoelectric conversion region including a light receiving portion, the charge transfer portion transferring signal charges generated in the photoelectric conversion region to a signal output portion;

and

an impurity layer for gettering on the back side of the semiconductor substrate, the impurity layer being formed by ion implantation.

56. An imaging apparatus comprising:

a backside illuminated imaging device according to claim 55; and

an image signal generation unit that generates an image signal based on an output signal from the backside illuminated imaging device.

57. A method for manufacturing a backside illuminated imaging device that performs imaging by illuminating light from a back side of a semiconductor substrate, which is opposite to a front side of the semiconductor substrate having an electrode, to generate electric charges in the semiconductor substrate based on the light and reading out the electric charges from the front side, which comprises:

forming a photoelectric conversion region and a charge transfer portion in a conductive semiconductor layer of an SOT substrate including a first semiconductor support substrate, an insulating layer, and a conductive semiconductor layer in this order, the photoelectric conversion region including a light receiving portion, the charge transfer portion transferring signal charges generated in the photoelectric conversion region;

fixing a surface of the SOI substrate opposite to the first semiconductor support substrate to a second semiconductor support substrate;

removing the first semiconductor support substrate from the SOI substrate; and

exposing a gettering region on a surface of the conductive semiconductor layer and forming a low-temperature oxide film.

58. The method according to claim 57, wherein the low-temperature oxide film is formed by performing a low-temperature anneal treatment in an environment of 500°

C. or less.

59. The method according to claim 57, further comprising:

removing the low-temperature oxide film and the gettering region;

performing a follow-up oxidation treatment for the exposed surface of the SOI substrate; and

depositing a thin film by means of a CVD treatment to the exposed surface of the SOI substrate to provide an incident light side surface.

60. The method according to claim 57, further comprising depositing a thin film by means of a CVD treatment to a surface of the low-temperature oxide film on the SOI substrate to provide an incident light side surface.

61. The method according to claim 57, further comprising:

removing the low-temperature oxide film formed on the exposed surface of the SOI substrate and the gettering region; and

depositing a thin film by means of a CVD treatment on the SOI substrate to provide an incident light side surface.

62. The method according to claim 57, wherein the low-temperature oxide film is formed by oxidizing the conductive semiconductor layer with oxygen radical or high-concentration ozone.

63. A backside illuminated imaging device that performs imaging by illuminating light from a back side of a semiconductor substrate, which is opposite to a front side of the semiconductor substrate having an electrode, to generate electric charges in the semiconductor substrate based on the light and reading out the electric charges from the front side, the backside illuminated imaging device being manufactured by the method of manufacturing the backside illuminated imaging device according to claim 57, comprising:

a photoelectric conversion region an a charge transfer portion on the front side of the semiconductor substrate, the photoelectric conversion region including a light receiving portion, the charge transfer portion transferring signal charges generated in the photoelectric conversion region; and

an oxide film and a CVD film on an outer side of the oxide film, in this order on a surface of the back side of the semiconductor substrate.

64. A backside illuminated imaging device that performs imaging by illuminating light from a back side of a semiconductor substrate, which is opposite to a front side of the semiconductor substrate having an electrode, to generate electric charges in the semiconductor substrate based on the light and reading out the electric charges from the front side, the backside illuminated imaging device being manufactured by the method of manufacturing the backside illuminated imaging device according to claim 57, comprising:

a photoelectric conversion region an a charge transfer portion on the front side of the semiconductor substrate, the photoelectric conversion region including a light receiving portion, the charge transfer portion transferring signal charges generated in the photoelectric conversion region; and

an oxide film containing heavy metal and a CVD film on an outer side of the oxide film, in this order on a surface of the back side of the semiconductor substrate.

65. A backside illuminated imaging device that performs imaging by illuminating light from a back side of a semiconductor substrate, which is opposite to a front side of the semiconductor substrate having an electrode, to generate electric charges in the semiconductor substrate based on the light and reading out the electric charges from the front side, the backside illuminated imaging device being manufactured by the method of manufacturing the backside illuminated imaging device according to claim 57, comprising:

a photoelectric conversion region an a charge transfer portion on the front side of the semiconductor substrate, the photoelectric conversion region including a light receiving portion, the charge transfer portion transferring signal charges generated in the photoelectric conversion region; and

a CVD film on a surface of the back side of the semiconductor substrate.

66. An imaging apparatus, comprising:

a backside illuminated imaging device according to claim 63; and

an image signal generation unit that generates an image signal based on an output signal from the backside illuminated imaging device.