EPITAXIAL SUBSTRATE AND METHOD FOR FORMING THE SAME

• US 20180315815A1
• Filed: 03/23/2018
• Published: 11/01/2018
• Est. Priority Date: 04/28/2017
• Status: Active Grant

• Current Assignee: GlobalWafers Co., Ltd. (Sino-American Silicon Products Incorporated)
• Original Assignee: GlobalWafers Co., Ltd. (Sino-American Silicon Products Incorporated)
• Inventors: LIU, CHE-MING, Lin, Man-Hsuan, Chuang, Chih-Yuan, Hsu, Shuo-Hung, Tsou, Chuan-Wei, Hsu, Wen-Ching
• Granted Patent: US 10,446,642 B2
• Time in Patent Office: Days
• CPC Class Codes: C30B 25/183 being provided with a buffer layer, e.g. a lattice matching layer
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: H01L 21/02381 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/0245 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/02502 consisting of two layers
• CPC Class Codes: H01L 21/0251 Graded layers
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 29/0638 for preventing surface leakage due to surface inversion layer, e.g. with channel stopper channel stoppers in combination with isolation region for integrated circuits H01L21/762
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/36 characterised by the concentration or distribution of impurities in the bulk material within semiconductor regions H01L29/06

Abstract

An epitaxial substrate and a method for forming the same are disclosed. The epitaxial substrate includes a substrate, a deposition layer, a buffer layer and an epitaxial layer. The deposition layer is directly formed on the substrate, wherein the deposition layer includes a gradient doping concentration, and has a first surface and a second surface which are opposite to each other; the gradient doping concentration has a minimum value at the first surface. The buffer layer is formed on the deposition layer, and an epitaxial layer is formed on the buffer layer. The epitaxial layer is mainly formed of group III-V nitride. The substrate and the deposition layer are formed of homogeneous material. Since the deposition layer is directly formed on the substrate, and the deposition layer and the substrate are formed of a homogeneous material, the epitaxial substrate includes a good heat dissipation efficiency and low leakage current.

Claims

1. An epitaxial substrate, comprising:

a substrate;

a deposition layer formed on the substrate directly, wherein the deposition layer includes a gradient doping concentration, and has a first surface and a second surface which are opposite to each other;

the gradient doping concentration has a minimum value at the first surface;

a buffer layer formed on the deposition layer; and

an epitaxial layer formed on the buffer layer, and the epitaxial layer is mainly formed of group III-V nitride;

wherein, the substrate and the deposition layer are formed of homogeneous material;

the deposition layer includes a gradient resistivity which includes a high impedance layer region which has a resistivity at least greater than 1500 ohm-cm.

2. The epitaxial substrate of claim 1, wherein the gradient resistivity has a maximum value at the first surface of the deposition layer.

3. The epitaxial substrate of claim 1, wherein a thickness of the high impedance layer region is smaller than or equal to 6 μ

m.

4. The epitaxial substrate of claim 1, wherein a thickness of the high impedance layer region is smaller than or equal to 2 μ

m.

5. The epitaxial substrate of claim 1, wherein a resistivity of the high impedance layer region is greater than 7000 ohm-cm.

6. The epitaxial substrate of claim 1, wherein the gradient doping concentration of the deposition layer decreases from the second surface to the first surface.

7. The epitaxial substrate of claim 1, wherein the dopants of the deposition layer and the substrate are the same.

8. The epitaxial substrate of claim 1, wherein the deposition layer at least includes a first stacked layer and a second stacked layer, wherein the first stacked layer is disposed on the substrate and between the substrate and the second stacked layer;

the second stacked layer is disposed on the first stacked layer.

9. The epitaxial substrate of claim 8, wherein a doping concentration of the first stacked layer is smaller than or equal to that of the substrate.

10. The epitaxial substrate of claim 8, wherein the dopants of the first stacked layer and the substrate are different.

11. The epitaxial substrate of claim 8, wherein the dopants of the first stacked layer and the second stacked layer are different.

12. The epitaxial substrate of claim 8, wherein the gradient resistivity has a maximum at the first surface of the deposition layer.

13. The epitaxial substrate of claim 1, wherein the substrate is a heavily doped substrate and the doping concentration is equal to or greater than 1×

10¹⁸ atom/cm³.

14. The epitaxial substrate of claim 8, wherein the substrate is a heavily doped substrate and the doping concentration is equal to or greater than 1×

10¹⁸ atom/cm³.

15. A method for forming an epitaxial substrate, comprising:

A. providing a substrate;

B. forming a deposition layer on the substrate, wherein the deposition layer and the substrate are formed of homogeneous material;

the deposition layer includes a gradient doping concentration and has a first surface and a second surface which are opposite to each other;

the gradient doping concentration has a minimum value at the first surface;

the deposition layer includes a gradient resistivity which includes a high impedance layer region having a resistivity at least greater than 1500 ohm-cm;

C. forming a buffer layer on the deposition layer; and

D. forming an epitaxial layer on the buffer layer, wherein the epitaxial layer is mainly formed of group III-V nitride.

16. The method of claim 15, wherein the gradient doping concentration of the deposition layer decreases toward the first surface.

17. The method of claim 15, wherein the dopants of the deposition layer and the substrate are the same.

18. The method of claim 15, wherein the deposition layer at least includes a first stacked layer and a second stacked layer;

the first stacked layer is formed on the substrate first, and the second stacked layer is formed on the first stacked layer in step B.

19. The method of claim 18, wherein a doping concentration of the first stacked layer is smaller than or equal to that of the substrate.

20. The method of claim 18, wherein the dopants of the first stacked layer and the substrate are different.

21. The method of claim 18, wherein the dopants of the first stacked layer and the second stacked layer are different.

22. The method of claim 15, wherein the substrate is a heavily doped substrate having a doping concentration which is equal to or greater than 1×

10¹⁸ atom/cm³.

23. The method of claim 18, wherein the substrate is a heavily doped substrate having a doping concentration which is equal to or greater than 1×

10¹⁸ atom/cm³.