Semiconductor device and method for fabrication thereof

• US 20050250234A1
• Filed: 05/10/2005
• Published: 11/10/2005
• Est. Priority Date: 05/10/2004
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Araki, Masahiro, Yamada, Eiji, Kamikawa, Takeshi
• Granted Patent: US 7,157,297 B2
• Time in Patent Office: Days
• US Class Current: 438/47
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/24 of the light emitting region, e.g. non-planar junction
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01S 2304/12 Pendeo epitaxial lateral overgrowth [ELOG], e.g. for growing GaN based blue laser diodes
• CPC Class Codes: H01S 5/0202 Cleaving
• CPC Class Codes: H01S 5/0207 Substrates having a special shape
• CPC Class Codes: H01S 5/2201 in a specific crystallographic orientation
• CPC Class Codes: H01S 5/2231 with inner confining structure only between the active layer and the upper electrode
• CPC Class Codes: H01S 5/32341 blue laser based on GaN or GaP

Abstract

On a processed substrate having an engraved region as a depressed portion formed thereon, a nitride semiconductor thin film is laid. The sectional area occupied by the nitride semiconductor thin film filling the depressed portion is 0.8 times the sectional area of the depressed portion or less.

Claims

1. A method for fabricating a nitride semiconductor device, the method including:

a first step of forming a processed substrate by forming, on a nitride semiconductor substrate of which at least part of a surface is a nitride semiconductor or on a substrate formed by laying a nitride semiconductor thin film on top of such a nitride semiconductor substrate, an engraved region formed as at least one depressed portion and a ridge portion formed as an non-engraved region; and

a second step of laying a nitride semiconductor layer portion consisting of a plurality of nitride semiconductor thin films both on the engraved region and on a surface of the ridge portion formed on the processed substrate,

wherein, in the first and second steps,

let a sectional area of a region surrounded by a sectional portion of the depressed portion cut along a plane perpendicular to a direction in which the depressed portion extends and lines extending from the surface of the ridge portion parallel to the surface of the ridge portion be A, and

let a sectional area occupied by the nitride semiconductor thin films laid in the depressed portion be B,

then B/A, indicating a degree in which the depressed portion is filled by the nitride semiconductor thin films, is 0.8 or less.

2. The method of claim 1,

wherein, in the first step, in the engraved region, the depressed portion is formed to have an opening width more than 100 μ

m, and

wherein, in the second step, a total thickness from the surface of the ridge portion to a surface of the nitride semiconductor layer portion is 0.8 times a depth of the depressed portion or less.

3. The method of claim 1,

wherein, in the first step, in the engraved region, the depressed portion is formed to have an opening width more than 30 μ

m but less than or equal to 100 μ

m, and

wherein, in the second step, a total thickness from the surface of the ridge portion to a surface of the nitride semiconductor layer portion is twice a depth of the depressed portion or less.

4. The method of claim 1,

wherein, in the first step, in the engraved region, the depressed portion is formed to have an opening width of 2 μ

m or more but 30 μ

m or less, and

wherein, in the second step, a total thickness from the surface of the ridge portion to a surface of the nitride semiconductor layer portion is three times a depth of the depressed portion or less.

5. The method of claim 1, the method further comprising:

a third step of forming a plurality of nitride semiconductor devices on top of the substrate by forming, on top of the nitride semiconductor layer portion laid on a surface of the processed substrate in the second step, electrode pads on which to perform wire bonding for connection with outside,

wherein, in the third step, the electrode pads are not formed above the engraved region.

6. The method of claim 5,

wherein, in the third step, the electrode pads are formed 5 μ

m or more apart from an edge of the engraved region.

7. The method of claim 1,

wherein, in the first step, the ridge portion has a width of 92 μ

m or more but 4 mm or less.

8. The method of claim 1,

wherein one nitride semiconductor device is formed in the ridge portion sandwiched between two adjacent engraved regions.

9. The method of claim 1,

wherein a plurality of nitride semiconductor devices are formed in the ridge portion sandwiched between two adjacent engraved regions.

10. The method of claim 1,

wherein chip separation is performed by performing scribing on a bottom surface of a part of the nitride semiconductor substrate located right below the engraved region of the processed substrate or a top surface of the nitride semiconductor substrate.

11. The method of claim 1, the method further comprising:

a fourth step of cleaving the processed substrate in a direction perpendicular to a first direction in which the engraved region of the nitride semiconductor device extends in order to form bars each having a plurality of nitride semiconductor devices mounted thereon; and

a fifth step of performing chip separation by splitting the bars in a direction parallel to the first direction in order to separate the individual nitride semiconductor devices on the bars into discrete chips,

wherein, in the fifth step, the chip separation is performed after scribing is performed on an top surface of the nitride semiconductor layer portion laid on the engraved region or on a bottom surface of a part of the nitride semiconductor substrate located right below the engraved region so as to form scribe lines parallel to the first direction.

12. The method of claim 11, the method including the fourth and fifth step,

wherein, in the fifth step, the chip separation is performed by performing scribing on a top surface of the nitride semiconductor layer portion laid on the engraved region or on a bottom surface of a part of the nitride semiconductor substrate located right below the engraved region and on a top surface of the nitride semiconductor layer portion laid on the ridge portion or on a bottom surface of a part of the nitride semiconductor substrate located right below the ridge portion.

13. The method of claim 11, the method including the fourth and fifth step,

wherein, in the fifth step, the scribe lines are formed in a shape of solid lines from end to end on each bar.

14. The method of claim 11, the method including the fourth and fifth step,

wherein, in the fifth step, the scribe lines are formed in a shape of solid lines in part of each bar.

15. The method of claim 11, the method including the fourth and fifth step,

wherein, in the fifth step, the scribe lines are formed in a shape of broken lines from end to end on each bar.

16. The method of claim 11, the method including the fourth and fifth step,

wherein, in the fifth step, the scribe lines are formed in an edge portion along an edge formed in a direction perpendicular to the first direction.

17. A nitride semiconductor device fabricated by the method of claim 1.

18. A method for fabricating a semiconductor device, the method including:

a first step of forming a processed substrate by forming, on a substrate having a nitride semiconductor layer in at least part of a surface thereof, an engraved region formed as at least one depressed portion and a ridge portion formed as an non-engraved region,

the method comprising;

a second step of forming inflow prevention walls as elevated portions along both edges of the ridge portion formed on the processed substrate; and

a third step of forming a nitride semiconductor layer portion consisting of at least one type of nitride semiconductor thin film both on the engraved region and on a surface of the ridge portion formed on the processed substrate having the inflow prevention walls formed in the second step so that the nitride semiconductor layer portion is formed on the inflow prevention walls formed along both edges of the ridge portion, and thereby forming inflow prevention portions elevated so as to have a level difference from a surface of a flat portion of the nitride semiconductor layer portion laid on the surface of the ridge portion.

19. The method of claim 18,

wherein, when the nitride semiconductor layer portion is formed in the third step, the depressed portion formed as the engraved region is not completely filled.

20. The method of claim 18,

wherein, in the second step, the inflow prevention walls are formed of one of SiO₂, Al₂O₃, TiO₂, ZrO, and W.

21. The method of claim 18,

wherein, when the inflow prevention walls are formed in the second step, the inflow prevention walls are given a thickness of 50 nm or more but 3 μ

m or less in a direction normal thereto and thus perpendicular to the surface of the ridge portion.

22. The method of claim 18,

wherein, when the inflow prevention walls are formed in the second step, the inflow prevention walls are given a width of 1 μ

m or more but 25 μ

m or less in a direction perpendicular to a length direction of the inflow prevention walls.

23. The method of claim 18, the method further comprising:

a fourth step of forming a plurality of semiconductor devices on top of the substrate by forming, on top of the nitride semiconductor layer portion laid on a surface of the processed substrate having the inflow prevention walls formed in the third step, electrode pads on which to perform wire bonding for connection with outside,

wherein, in the fourth step, the electrode pads are not formed above the engraved region.

24. The method of claim 23,

wherein, in the fourth step, the electrode pads are formed 30 μ

m or more apart from an edge of the engraved region.

25. The method of claim 18,

wherein one semiconductor device is formed in the ridge portion sandwiched between two adjacent engraved regions.

26. The method of claim 18,

wherein a plurality of semiconductor devices are formed in the ridge portion sandwiched between two adjacent engraved regions.

27. The method of claim 18,

wherein chip separation is performed by performing scribing on an top surface of the nitride semiconductor layer portion laid on the engraved region or on a bottom surface of a part of the processed substrate located right below the engraved region.

28. The method of claim 18,

wherein, when the engraved region is formed as the depressed portion in the first step, the depressed portion is given a depth of 1 μ

m or more but 20 μ

m or less.

29. The method of claim 18,

wherein, when the engraved region is formed as the depressed portion in the first step, the depressed portion is given an opening width of 1 μ

m or more.

30. The method of claim 18,

wherein, when the engraved region is formed as the depressed portion in the first step, the ridge portion sandwiched between two adjacent engraved regions is given a width of 140 μ

m or more but 4 mm or less.

31. A semiconductor device fabricated by the method of claim 18.

32. A method for fabricating a semiconductor device, the method including:

a first step of forming a processed substrate by forming, on a substrate having a nitride semiconductor layer in at least part of a surface thereof, an engraved region formed as at least one depressed portion and a ridge portion formed as an non-engraved region; and

a second step of forming a nitride semiconductor layer portion consisting of at least one type of nitride semiconductor thin film both on the engraved region and on a surface of the ridge portion formed on the processed substrate,

wherein, in the second step, a thickness of the nitride semiconductor layer portion laid in both edge portions of the ridge portion close to the engraved region as measured from the surface of the ridge portion to a surface of the nitride semiconductor layer portion is made greater than a thickness of the nitride semiconductor layer portion laid elsewhere than in both edge portions of the ridge portion as measured from the surface of the ridge portion to the surface of the nitride semiconductor layer portion so as to form inflow prevention portions elevated from a surface of a flat portion of the nitride semiconductor layer portion laid on a surface of a region elsewhere than in both edge portions of the ridge portion.

33. The method of claim 32,

wherein, when the nitride semiconductor layer portion is formed in the second step, the depressed portion formed as the engraved region is not completely filled.

34. The method of claim 32,

wherein, in the second step, the level difference between the surface of the flat portion of the nitride semiconductor layer portion laid on the surface of the ridge portion and the inflow prevention portions elevated therefrom is 150 nm or more.

35. The method of claim 32,

wherein, in the second step, the nitride semiconductor thin film in direct contact with a surface of the processed substrate is 0.5 μ

m or less thick GaN.

36. The method of claim 32,

wherein, in the second step, the nitride semiconductor thin film in direct contact with a surface of the processed substrate is AlGaN.

37. The method of claim 32,

wherein, in the second step,

the nitride semiconductor thin film in direct contact with a surface of the processed substrate is GaN, and,

when the GaN is laid on the surface of the processed substrate, the surface of the processed substrate is at a temperature of 1,025°

.

38. The method of claim 32,

wherein, in the second step,

the nitride semiconductor thin film in direct contact with a surface of the processed substrate is GaN, and,

when the GaN is laid, a ratio of a flow rate in mol at which a source material containing nitrogen atoms as a group V element is supplied per unit time to a flow rate in mol at which a source material containing gallium atoms as a group III element is supplied per unit time is 2,000 or more.

39. The method of claim 32,

wherein, in the second step, the nitride semiconductor thin films forming the nitride semiconductor layer portion include an AlGaN layer with an Al content of 0.02.

40. The method of claim 32, the method further comprising:

a fourth step of forming a plurality of semiconductor devices on top of the substrate by forming, on top of the nitride semiconductor layer portion laid on a surface of the processed substrate in the second step, electrode pads on which to perform wire bonding for connection with outside,

wherein, in the fourth step, the electrode pads are not formed above the engraved region.

41. The method of claim 40,

wherein, in the fourth step, the electrode pads are formed 30 μ

m or more apart from an edge of the engraved region.

42. The method of claim 32,

wherein one semiconductor device is formed in the ridge portion sandwiched between two adjacent engraved regions.

43. The method of claim 32,

wherein a plurality of semiconductor devices are formed in the ridge portion sandwiched between two adjacent engraved regions.

44. The method of claim 32,

wherein chip separation is performed by performing scribing on an top surface of the nitride semiconductor layer portion laid on the engraved region or on a bottom surface of a part of the processed substrate located right below the engraved region.

45. The method of claim 32,

wherein, when the engraved region is formed as the depressed portion in the first step, the depressed portion is given a depth of 1 μ

m or more but 20 μ

m or less.

46. The method of claim 32,

wherein, when the engraved region is formed as the depressed portion in the first step, the depressed portion is given an opening width of 1 μ

m or more.

47. The method of claim 32,

wherein, when the engraved region is formed as the depressed portion in the first step, the ridge portion sandwiched between two adjacent engraved regions is given a width of 140 μ

m or more but 4 mm or less.

48. A semiconductor device fabricated by the method of claim 32.