Method for fabricating semiconductor device

• US 20030131788A1
• Filed: 11/13/2002
• Published: 07/17/2003
• Est. Priority Date: 11/13/2001
• Status: Active Grant

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Ueda, Tetsuzo
• Granted Patent: US 6,881,261 B2
• Time in Patent Office: Days
• US Class Current: 117/108
• CPC Class Codes: H01L 21/0237 Materials
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/02472 Oxides
• CPC Class Codes: H01L 21/02507 Alternating layers, e.g. superlattice
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02576 N-type
• CPC Class Codes: H01L 21/02579 P-type
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 21/02664 Aftertreatments planarisation in general H01L21/304
• CPC Class Codes: H01L 21/268 using electromagnetic radiation, e.g. laser radiation
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/025 Physical imperfections, e.g. particular concentration or distribution of impurities
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01S 5/3054 p-doping
• CPC Class Codes: H01S 5/32341 blue laser based on GaN or GaP

Abstract

A p-type InGaAlN layer, an InGaAlN active layer, and an n-type InGaAlN layer each having a composition represented by (Al_xGa_1-x)_yIn_1-yN (0≦x≦1, 0≦y≦1) are formed on a sapphire substrate. In the as-grown state, Mg is bonded to hydrogen atoms in the p-type InGaAlN layer. Then, the back surface of the sapphire substrate is irradiated with a laser beam in a nitrogen atmosphere. The resistance of the p-type InGaAlN layer is reduced by removing hydrogen therefrom with irradiation with a weak laser beam. During the irradiation with the laser beam, the diffusion of a dopant in a multilayer portion is suppressed such that a dopant profile retains sharpness. It is also possible to separate the sapphire substrate from the multilayer portion by subsequently using an intense laser beam for irradiation.

Claims

1. A method for fabricating a semiconductor device having a semiconductor layer formed by epitaxial growth from a single-crystal substrate, the method comprising the steps of:

(a) forming a multilayer film having at least a first semiconductor layer composed of a group Ill-V compound doped with a p-type impurity and containing nitrogen and an n-type second semiconductor layer composed of a group Ill-V compound doped with an n-type impurity and containing nitrogen such that the single-crystal substrate is covered with the multilayer film; and

(b) irradiating the first semiconductor layer with a light beam to activate the p-type impurity in the first semiconductor layer.

2. The method of claim 1, wherein the light beam has an energy larger than an optical band gap of a lowermost portion of the first semiconductor layer.

3. The method of claim 1, wherein

the step (a) includes forming the first semiconductor layer below the second semiconductor layer and

the step (b) includes irradiating the first semiconductor layer with the light beam through a back surface of the single-crystal substrate.

4. The method of claim 3, wherein the step (b) includes varying a power density or energy of the light beam used for the irradiation into two types to activate the p-type impurity in the first semiconductor layer and separate the first semiconductor layer and the single-crystal substrate from each other.

5. The method of claim 3, further comprising the step of:

fixing a recipient substrate to the multilayer structure.

6. The method of claim 3, wherein the step (b) includes performing a first-stage treatment for activating the p-type impurity in the first semiconductor layer and performing a second-stage treatment for varying a power density or energy of the light beam to separate the first semiconductor layer and the single-crystal substrate from each other.

7. The method of claim 6, further comprising, after the first-stage treatment in the step (b) and prior to the second-stage treatment, the step of:

fixing a recipient substrate onto the multilayer structure.

8. The method of claim 3, wherein

the step (b) includes decomposing or denaturing the first semiconductor layer to form a conductor layer, the method further comprising, after the step (b), the step of:

forming an ohmic electrode composed of a conductor material on the conductor layer.

9. The method of claim 8, further comprising, after the step (b) and prior to the formation of the ohmic electrode, the step of:

etching a surface portion of the conductor layer.

10. The method of claim 3, further comprising, prior to the step (a), the step of:

forming, on the single-crystal substrate, a spacer layer having an optical band gap smaller than an optical band gap of the single-crystal substrate, wherein

the step (a) includes forming the multilayer film on the spacer layer and

the step (b) includes activating the p-type impurity in the first semiconductor layer and separating the spacer layer and the single-crystal substrate from each other.

11. The method of claim 1, wherein

the step (a) includes forming the first semiconductor layer above the second semiconductor layer and

the step (b) includes irradiating the first semiconductor layer with the light beam from above the first semiconductor layer.

12. The method of claim 11, further comprising, after the step (a), the step of:

forming a cap layer on the multilayer portion, wherein

the step (b) includes irradiating the first semiconductor layer with the light beam from above the cap layer.

13. The method of claim 12, further comprising the steps of:

after the step (b), removing the cap layer;

fixing a recipient substrate onto the multilayer portion; and

after or prior to the fixation of the recipient substrate, irradiating a back surface of the single-crystal substrate with a light beam to separate the single-crystal substrate from the multilayer portion.

14. The method of claim 13, wherein the light beam used to irradiate the back surface of the substrate is higher in energy than the light beam used for the irradiation from above the multilayer portion in the step (b).

15. The method of claim 11, further comprising:

after the step (b), forming an ohmic electrode composed of a conductor material on the first semiconductor layer.

16. The method of claim 11, wherein

the step (b) includes decomposing or denaturing the first semiconductor layer to form a conductor layer, the method further comprising the step of:

after the step (b), forming an ohmic electrode composed of a conductor material on the conductor layer.

17. The method of claim 16, further comprising:

after the step (b) and prior to the formation of the ohmic electrode, etching a surface portion of the conductor layer.

18. The method of claim 1, wherein

the step (a) includes forming the multilayer portion such that it further has an n-type third semiconductor layer opposing the second semiconductor layer with the first semiconductor layer interposed therebetween and having an optical band gap different from an optical band gap of the first semiconductor layer.

19. The method of claim 18, wherein the optical band gap of the third semiconductor layer is larger than the optical band gap of the first semiconductor layer and larger than an energy of the light beam.

20. The method of claim 18, wherein a collector region of a bipolar transistor is formed from the first semiconductor layer, a base region of the bipolar transistor is formed from the second semiconductor layer, and an emitter region of the bipolar transistor is formed from the third semiconductor layer.

21. The method of claim 20, wherein an optical band gap of the emitter region is adjusted to be larger than an optical band gap of the base region.

22. The method of claim 1, wherein the step (c) is performed in an inert gas atmosphere or in an atmosphere under a reduced pressure.

23. The method of claim 1, wherein the light beam used in activating the p-type impurity in the first semiconductor layer has an energy smaller than an optical band gap of the second semiconductor layer.

24. The method of claim 1, wherein a light source of the light beam is a laser which oscillates pulsatively.

25. The method of claim 1, wherein the light beam used in activating the p-type impurity in the first semiconductor layer is a bright line spectrum from a mercury vapor lamp.

26. The method of claim 1, wherein the single-crystal substrate is heated during the irradiation with the light beam.

27. The method of claim 26, wherein a heating temperature in heating the single-crystal substrate is in the range of 400°

C. to 750°

C.

28. The method of claim 1, wherein the irradiation with the light beam is performed such that a luminous flux scans an entire surface of the single-crystal substrate.

29. The method of claim 1, wherein the step (a) includes using Mg or Be as a dopant in forming the first semiconductor layer.

30. The method of claim 1, wherein the step (a) includes forming the first semiconductor layer in an atmosphere containing hydrogen.

31. The method of claim 1, wherein a substrate selected from a sapphire substrate, an SiC substrate, an MgO substrate, an LiGaO₂ substrate, an LiGa_xAl_1-xO₂ (0≦

x≦

1) mixed crystal substrate, and an LiAlO₂ substrate is used as the single-crystal substrate.

32. The method of claim 5, wherein a substrate selected from an Si substrate, a GaAs substrate, a GaP substrate, and an InP substrate is used as the recipient substrate.