Methods of fabricating semiconductor devices including implanted regions for providing low-resistance contact to buried layers and related devices

• US 9,984,881 B2
• Filed: 07/16/2014
• Issued: 05/29/2018
• Est. Priority Date: 11/06/2006
• Status: Active Grant

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Sheppard, Scott T., Suvorov, Alexander V.
• Primary Examiner(s): HUBER, ROBERT T
• Application Number:
  US14/332,575
• Publication Number:
  US 20140329367A1
• Time in Patent Office: 1,413 Days
• Field of Search: 257192, 257E21403, 438172, 438181, 438604
• CPC Class Codes: H01L 21/2654 in AIIIBV compounds
• CPC Class Codes: H01L 21/26553 Through-implantation
• CPC Class Codes: H01L 29/66212 Schottky diodes
• CPC Class Codes: H01L 29/66446 with an active layer made of a group 13/15 material, e.g. group 13/15 velocity modulation transistor [VMT], group 13/15 negative resistance FET [NERFET]
• CPC Class Codes: H01L 29/66462 with a heterojunction interface channel or gate, e.g. HFET, HIGFET, SISFET, HJFET, HEMT
• CPC Class Codes: H01L 29/778 with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface H01L29/803 takes precedence
• CPC Class Codes: H01L 29/802 with heterojunction gate, e.g. transistors with semiconductor layer acting as gate insulating layer, MIS-like transistors H01L29/806 takes precedence; with one dimensional electron gas H01L29/775; with dimensional electron gas H01L29/778
• CPC Class Codes: H01L 29/812 with a Schottky gate H01L29/7725, H01L29/775, H01L29/778, H01L29/806 take precedence; with Schottky contact on top of heterojunction gate H01L29/802

Abstract

Methods of fabricating a semiconductor device include forming a first semiconductor layer of a first conductivity type and having a first dopant concentration, and forming a second semiconductor layer on the first semiconductor layer. The second semiconductor layer has a second dopant concentration that is less than the first dopant concentration. Ions are implanted into the second semiconductor layer to form an implanted region of the first conductivity type extending through the second semiconductor layer to contact the first semiconductor layer. A first electrode is formed on the implanted region of the second semiconductor layer, and a second electrode is formed on a non-implanted region of the second semiconductor layer. Related devices are also discussed.

Claims

1. A method of fabricating a semiconductor device, the method comprising:

forming a first semiconductor layer of a first conductivity type;

forming a second semiconductor layer on the first semiconductor layer;

implanting ions into the second semiconductor layer to form an implanted region comprising a distribution of implanted dopants having an implanted dopant concentration comprising a substantially uniform concentration of at least about 5×

10²⁰ ions/cm³ that extends at least about 1000 Angstroms from a first depth within the implanted region to a second depth within the implanted region, wherein the substantially uniform concentration is a result of first, second, and third implantations; and

forming a first electrode on the implanted region of the second semiconductor layer,

wherein forming the first semiconductor layer comprises forming the first semiconductor layer to have a first dopant concentration,

wherein forming the second semiconductor layer comprises forming the second semiconductor layer to have a second dopant concentration that is less than the first dopant concentration, and

wherein the method further comprises forming a second electrode on a non-implanted region of the second semiconductor layer that is spaced apart from the implanted region.

2. The method of claim 1, wherein the first semiconductor layer and the second semiconductor layer comprise a Group III-nitride material.

3. The method of claim 1, further comprising:

forming a protective layer on the second semiconductor layer prior to implanting the ions; and

after implanting the ions, annealing the first and second semiconductor layers and the protective layer using a temperature of about 1000°

C. to about 1300°

C. for about 30 seconds to about 30 minutes, to activate the implanted ions,

wherein the protective layer is thinner than the second semiconductor layer,

wherein implanting the ions comprises implanting the ions into the second semiconductor layer through the protective layer, and

wherein forming the first electrode comprises;

forming an opening in the protective layer after annealing to expose the implanted region of the second semiconductor layer; and

forming an ohmic contact in the opening on the exposed implanted region.

4. The method of claim 1, further comprising:

forming a protective layer on the second semiconductor layer prior to implanting the ions; and

after implanting the ions, annealing the first and second semiconductor layers and the protective layer to activate the implanted ions,

wherein implanting the ions comprises implanting the ions into the second semiconductor layer through the protective layer, and

wherein the protective layer comprises a high purity nitride (HPN).

5. The method of claim 1, further comprising:

forming a protective layer on the second semiconductor layer prior to implanting the ions; and

after implanting the ions, annealing the first and second semiconductor layers and the protective layer to activate the implanted ions,

wherein implanting the ions comprises implanting the ions into the second semiconductor layer through the protective layer, and

wherein the first and second semiconductor layers comprise gallium nitride (GaN), and wherein forming the protective layer comprises;

forming a first protective layer comprising a Group III-nitride including aluminum on the second semiconductor layer; and

forming a second protective layer comprising a high purity nitride (HPN) on the first protective layer.

6. The method of claim 1, further comprising:

forming a protective layer on the second semiconductor layer prior to implanting the ions; and

after implanting the ions, annealing the first and second semiconductor layers and the protective layer to activate the implanted ions,

wherein implanting the ions comprises implanting the ions into the second semiconductor layer through the protective layer, and

wherein the protective layer comprises silicon nitride (SiN), silicon dioxide (SiO₂), and/or silicon oxynitride (SiON).

7. The method of claim 1, further comprising:

forming a protective layer on the second semiconductor layer prior to implanting the ions; and

after implanting the ions, annealing the first and second semiconductor layers and the protective layer to activate the implanted ions,

wherein implanting the ions comprises implanting the ions into the second semiconductor layer through the protective layer, and

wherein implanting the ions into the second semiconductor layer comprises;

implanting the ions into the second semiconductor layer to form the implanted region extending through the second semiconductor layer and extending at least partially into the protective layer.

8. The method of claim 1,

wherein implanting the ions into the second semiconductor layer comprises:

implanting the ions into the second semiconductor layer to form the implanted region extending through the second semiconductor layer and extending at least partially into the first semiconductor layer, and

wherein the implanted region has a peak dopant concentration in the second semiconductor layer.

9. The method of claim 1,

wherein the first and second semiconductor layers comprise channel and surface layers, respectively,

wherein implanting the ions comprises:

implanting the ions into the surface layer to provide the distribution of implanted dopants with a substantially uniform concentration throughout the implanted region of the surface layer, and to extend the distribution of implanted dopants through the surface layer and partially into but not completely through the channel layer,

wherein the distribution of implanted dopants does not have a substantially uniform concentration throughout the implanted region in the channel layer, and

wherein implanting the ions into the surface layer to provide the distribution of implanted dopants with the substantially uniform concentration comprises;

implanting ions of the first conductivity type at a first dose and at a first implantation energy; and

then

implanting ions of the first conductivity type at a second dose and at a second implantation energy.

10. The method of claim 9, wherein the first dose comprises about 0.5×

10¹⁵ to about 2.5×

10¹⁵ ions/cm² and the first implantation energy comprises about 160keV, and wherein the second dose comprises about 0.8×

10¹⁵ to about 5×

10¹⁵ ions/cm² and the second implantation energy comprises about 260keV.

11. The method of claim 9, wherein implanting the ions into the second semiconductor layer to provide the distribution of implanted dopants with the substantially uniform concentration further comprises:

implanting ions of the first conductivity type at a third dose and at a third implantation energy.

12. The method of claim 1, wherein the implanted ions comprise silicon (Si), sulfur (S) and/or oxygen (O).

13. The method of claim 1, wherein the first semiconductor layer and the second semiconductor layer comprise a same material.

14. The method of claim 1, wherein the first semiconductor layer and/or the second semiconductor layers comprises an epitaxial layer.

15. The method of claim 1, wherein the first electrode comprises an ohmic contact.

16. The method of claim 1,

wherein the first electrode comprises a cathode contact on the implanted region of the second semiconductor layer,

wherein the second electrode comprises an anode contact on the non-implanted region of the second semiconductor layer, and

wherein the first semiconductor layer and/or the second semiconductor layer has a thickness of about 100 nanometers (nm) to about 500 nm.

17. The method of claim 1,

wherein a lateral distance between the second electrode and the implanted region is less than a lateral distance between the second electrode and the first electrode, and

wherein the lateral distance between the second electrode and the implanted region is less than about 1 micrometer (μ

m).

18. The method of claim 1,

wherein the first electrode comprises a source/drain contact on the implanted region of the second semiconductor layer,

wherein the second electrode comprises a gate contact on the non-implanted region of the second semiconductor layer, and

wherein a bandgap of the second semiconductor layer is greater than a bandgap of the first semiconductor layer.

19. The method of claim 1, wherein implanting the ions comprises:

implanting the ions into the second semiconductor layer to form the implanted region comprising the implanted dopant concentration of at least about 5×

10²⁰ ions/cm³ at a depth within the implanted region of at least about 2000 Angstroms.

20. The method of claim 1,

wherein the first dopant concentration comprises 1×

10¹⁹ ions/cm³ or higher, and

wherein forming the first semiconductor layer comprises forming the first semiconductor layer to have the first dopant concentration that comprises 1×

10¹⁹ ions/cm³ or higher, before implanting the ions into the second semiconductor layer.

21. A method of fabricating a semiconductor device, the method comprising:

forming a first semiconductor layer of a first conductivity type and having a first dopant concentration;

forming a second semiconductor layer on the first semiconductor layer, the second semiconductor layer having a second dopant concentration that is less than the first dopant concentration;

implanting ions into the second semiconductor layer to form an implanted region of the first conductivity type extending through the second semiconductor layer to contact the first semiconductor layer, and to provide a distribution of implanted dopants having a substantially uniform concentration that extends at least about 1000 Angstroms from a first depth within the implanted region to a second depth within the implanted region;

forming a first electrode on the implanted region of the second semiconductor layer; and

forming a second electrode on a non-implanted region of the second semiconductor layer that is spaced apart from the implanted region,

wherein the substantially uniform concentration results from;

implanting ions of the first conductivity type at a first dose and at a first implantation energy;

then

implanting ions of the first conductivity type at a second dose and at a second implantation energy; and

implanting ions of the first conductivity type at a third dose and at a third implantation energy, and

wherein the third dose comprises about 0.5×

10¹⁵to about 3.7×

10¹⁵ ions/cm².

22. A method of fabricating a semiconductor device, the method comprising:

forming a first semiconductor layer of a first conductivity type;

forming a second semiconductor layer on the first semiconductor layer;

implanting ions into the second semiconductor layer to form an implanted region of the first conductivity type extending through the second semiconductor layer to contact the first semiconductor layer, wherein implanting the ions comprises;

implanting ions of the first conductivity type at a first dose and at a first implantation energy;

then

implanting ions of the first conductivity type at a second dose and at a second implantation energy; and

then

implanting ions of the first conductivity type at a third dose and at a third implantation energy, wherein the first, second, and third implantation energies result in a substantially uniform implanted dopant concentration that extends at least about 1000Angstroms from a first depth within the implanted region to a second depth within the implanted region;

forming a first electrode on the implanted region of the second semiconductor layer; and

forming a second electrode on a non-implanted region of the second semiconductor layer that is spaced apart from the implanted region,

wherein forming the first semiconductor layer comprises forming the first semiconductor layer to have a first dopant concentration, and

wherein forming the second semiconductor layer comprises forming the second semiconductor layer to have a second dopant concentration that is less than the first dopant concentration.

23. The method of claim 22, wherein the first dose comprises about 0.5×

10¹⁵ to about 2.5×

10¹⁵ ions/cm² and the first implantation energy comprises about 160keV, and wherein the second dose comprises about 0.8×

10¹⁵ to about 5×

10¹⁵ ions/cm² and the second implantation energy comprises about 260keV.

24. The method of claim 22, wherein implanting the ions comprises:

implanting the ions into the second semiconductor layer to form the implanted region with a distribution of implanted dopants at a depth within the implanted region of at least about 2000 Angstroms, and wherein the first implantation energy comprises about 160keV, the second implantation energy comprises about 260keV, or the third implantation energy comprises about 360keV.