Fabrication of self-aligned gallium arsenide MOSFETS using damascene gate methods

• US 7,955,917 B2
• Filed: 09/18/2008
• Issued: 06/07/2011
• Est. Priority Date: 03/29/2007
• Status: Active Grant

• Current Assignee: Novartis Ag
• Original Assignee: Micron Technology, Inc.
• Inventors: Hanafi, Hussein I.
• Primary Examiner(s): Le; Dung A.
• Application Number:
  US12/233,208
• Publication Number:
  US 20090011563A1
• Time in Patent Office: 992 Days
• Field of Search: 438/83, 438303-306, 257/E21.441, 257/E29.258
• US Class Current: 438/183
• CPC Class Codes: H01L 29/105 with vertical doping variation H01L29/7827 takes precedence
• CPC Class Codes: H01L 29/66522 with an active layer made of a group 13/15 material H01L29/66446 takes precedence
• CPC Class Codes: H01L 29/6653 using the removal of at least part of spacer, e.g. disposable spacer
• CPC Class Codes: H01L 29/66545 using a dummy, i.e. replacement gate in a process wherein at least a part of the final gate is self aligned to the dummy gate
• CPC Class Codes: H01L 29/66606 with final source and drain contacts formation strictly before final or dummy gate formation, e.g. contact first technology H01L29/66621 takes precedence

Abstract

A method for fabricating a gallium arsenide MOSFET device is presented. A dummy gate is formed over a gallium arsenide substrate. Source-drain extensions are implanted into the substrate adjacent the dummy gate. Dummy spacers are formed along dummy gate sidewalls and over a portion of the source-drain extensions. Source-drain regions are implanted. Insulating spacers are formed on dummy oxide spacer sidewalls. A conductive layer is formed over the source-drain regions. The conductive layer is annealed to form contacts to the source-drain regions. The dummy gate and the dummy oxide spacers are removed to form a gate opening. A passivation layer is in-situ deposited in the gate opening. The surface of the passivation layer is oxidized to create an oxide layer. A dielectric layer is ex-situ deposited over the oxide layer. A gate metal is deposited over the dielectric layer to form a gate stack in the gate opening.

Claims

1. A method for fabricating a MOSFET device, the method comprising:

forming a dummy gate over a substrate;

implanting source-drain extensions into the substrate adjacent the dummy gate;

forming dummy spacers along the sidewalls of the dummy gate and over a portion of the source-drain extensions;

defining the source-drain regions adjacent the source drain extensions;

forming contacts to the source-drain regions;

removing the dummy gate and the dummy spacers to form a gate opening;

depositing in-situ a passivation layer in the gate opening;

forming an oxide layer on the passivation layer;

depositing ex-situ a dielectric layer over the oxide layer; and

depositing a gate metal over the dielectric layer to form a gate stack in the gate opening.

2. The method of claim 1, wherein the substrate is comprised of gallium arsenide.

3. The method of claim 1, wherein the substrate is comprised of undoped <

100>

oriented gallium arsenide.

4. The method of claim 1, further comprising:

implanting and annealing source-drain regions adjacent the source-drain extensions after forming the dummy spacers; and

forming insulating spacers on the sides of the dummy spacers.

5. The method of claim 1, wherein the source-drains regions are defined with a photoresist layer.

6. The method of claim 5, further comprising:

forming a conductive layer over the photoresist layer; and

lifting off the photoresist layer and annealing the conductive layer to form the contacts to the source-drain regions.

7. The method of claim 1, wherein the contacts are formed by evaporating a layer of gold germanium over the source-drain regions, evaporating a layer of nickel over the layer of gold geranium germanium and evaporating a layer of gold over the layer of nickel.

8. The method of claim 1, further comprising:

depositing a layer of nitride after forming the contacts to the source-drain regions;

depositing a layer of oxide over the layer of nitride and planaraizing the oxide layer to the uppermost surface of the layer of nitride; and

etching the layer of oxide and layer of nitride to the uppermost surface of the dummy gate.

9. The method of claim 1, wherein the oxide layer is formed on the passivation layer by oxidizing the surface of the passivation layer.

10. The method of claim 1, wherein the dummy gates are comprised of oxide.

11. The method of claim 1, wherein the passivation layer comprises amorphous silicon.

12. The method of claim 1, wherein the oxide layer comprises silicon dioxide.

13. The method of claim 1, wherein the dielectric layer comprises hafnium oxide.

14. The method of claim 1, wherein the gate metal comprises polysilicon, tungsten, tantalum, titanium nickel, or combinations thereof.

15. A method for fabricating a gallium arsenide MOSFET device, the method comprising:

forming a dummy gate over a substrate of gallium arsenide;

implanting source-drain extensions adjacent the dummy gate;

forming dummy oxide spacers along the sidewalls of the dummy gate and over a portion of the source-drain extensions;

defining the source-drain regions adjacent the source-drain extensions;

forming alloy contacts to the source-drain regions;

removing the dummy gate and removing the dummy oxide spacers to form a gate opening;

depositing in-situ a layer of amorphous silicon;

forming a silicon dioxide layer on the amorphous silicon layer;

depositing ex-situ a layer of hafnium oxide over the silicon dioxide layer; and

depositing gate metal over the hafnium oxide layer to form a gate stack.

16. The method of claim 15, wherein the alloy contacts comprise a layer of gold germanium over the source-drain regions, a layer of nickel over the layer of gold germanium and a layer of gold over the layer of nickel.

17. The method of claim 15, wherein the dummy gate is comprised of polysilicon.

18. The method of claim 15, wherein the amorphous silicon layer has a thickness of about 1.5 nm.

19. The method of claim 15, wherein the silicon dioxide layer has a thickness of less than 1 nm.

20. The method of claim 15, wherein the hafnium oxide layer has a thickness of about 10 nm.