Semiconductor device and method for fabricating the same

Abstract

A semiconductor device in which selectivity in epitaxial growth is improved. There is provided a semiconductor device comprising a gate electrode formed over an Si substrate, which is a semiconductor substrate, with a gate insulating film therebetween and an insulating layer formed over sides of the gate electrode and containing a halogen element. With this semiconductor device, a silicon nitride film which contains the halogen element is formed over the sides of the gate electrode when an SiGe layer is formed over the Si substrate. Therefore, the SiGe layer epitaxial-grows over the Si substrate with high selectivity. As a result, an OFF-state leakage current which flows between, for example, the gate electrode and source/drain regions is suppressed and a manufacturing process suitable for actual mass production is established.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing an important part of a semiconductor device for which selective epitaxial growth is used (part 1).

FIG. 2 is a sectional view showing an important part of a semiconductor device for which the selective epitaxial growth is used (part 2).

FIG. 3 is an example of a flow chart of fabricating a semiconductor device by using the selective epitaxial growth.

FIG. 4 is a sectional view showing an important part of the step of forming the gate electrode.

FIG. 5 is a sectional view showing an important part of the step of forming the insulating layer (part 1).

FIG. 6 is a sectional view showing an important part of the step of forming the side walls (part 1).

FIG. 7 is a sectional view showing an important part of the step of recessing the semiconductor substrate (part 1).

FIG. 8 is a sectional view showing an important part of the step of forming the source/drain electrodes (part 1).

FIG. 9 is a sectional view showing an important part of the step of forming the insulating layer (part 2).

FIG. 10 is a sectional view showing an important part of the step of forming the side walls (part 2).

FIG. 11 is a view for describing the differences in the growth of SiGe on silicon nitride films.

FIG. 12 is a view for describing the relationship between the ratio of Si atoms to N atoms and chlorine content.

FIG. 13 shows SEM images for describing the difference in the growth of SiGe on silicon nitride films which contain Cl.

FIG. 14 is a view for describing the differences in the growth of SiGe on silicon nitride films which contain Cl.

FIG. 15 is an example of a flow chart of pretreatment for fabricating a semiconductor device by using selective epitaxial growth.

FIG. 16 is a sectional view showing an important part of the step of recessing the semiconductor substrate (part 2).

FIG. 17 is a sectional view showing an important part of the step of supplying HCl—H₂ mixed gas.

FIG. 18 is a sectional view showing an important part of the step of forming the source/drain electrodes (part 2).

FIG. 19 is a SEM image of the surface of a CVD-silicon nitride film of sample G.

FIG. 20 is a SEM image of the surface of a CVD-silicon nitride film of sample H.

FIG. 21 is a sectional view showing an important part of a recessed source/drain MOSFET in which a deterioration in selectivity has occurred.

Claims

1. A semiconductor device comprising: a gate electrode formed over a semiconductor substrate with a gate insulating film therebetween;an insulating film formed over side wall portions of the gate electrode and having a laminated structure; anda semiconductor epitaxial growth layer formed on the semiconductor substrate,wherein a content of a halogen element in a top layer of the insulating film having the laminated structure is higher than contents of the halogen element in other layers of the laminated structure.

2. The semiconductor device according to claim 1, wherein the halogen element is one of chlorine and bromine.

3. The semiconductor device according to claim 1, wherein the insulating film is a silicon nitride film.

4. The semiconductor device according to claim 1, wherein a material for the semiconductor substrate is one of silicon, silicon which contains germanium, and germanium.

5. A semiconductor device comprising: a gate electrode formed over a semiconductor substrate with a gate insulating film therebetween;an insulating film formed over side wall portions of the gate electrode and containing a halogen element; anda semiconductor epitaxial growth layer formed on the semiconductor substrate,wherein a content of the halogen element in the insulating film has a slope.

6. The semiconductor device according to claim 5, wherein the halogen element is one of chlorine and bromine.

7. The semiconductor device according to claim 5, wherein the insulating film is a silicon nitride film.

8. The semiconductor device according to claim 5, wherein a material for the semiconductor substrate is one of silicon, silicon which contains germanium, and germanium.

9. A method for fabricating a semiconductor device, the method comprising the steps of: forming a first insulating film over a first semiconductor layer;forming over the first insulating film a second insulating film in which a content of a halogen element is higher than a content of the halogen element in the first insulating film;exposing a surface of the first semiconductor layer by removing part of the first insulating film and part of the second insulating film; andmaking a second semiconductor layer selectively epitaxial-grow on the exposed surface of the first semiconductor layer by supplying a material for forming the second semiconductor layer onto the surface of the first semiconductor layer and a surface of the second insulating film.

10. The method according to claim 9, wherein the halogen element is one of chlorine and bromine.

11. The method according to claim 9, wherein the first insulating film and the second insulating film are silicon nitride films.

12. A method for fabricating a semiconductor device, the method comprising the steps of: forming an insulating film which contains a halogen element over a first semiconductor layer;exposing a surface of the first semiconductor layer by removing part of the insulating film; andmaking a second semiconductor layer selectively epitaxial-grow on an exposed surface of the first semiconductor layer by supplying a material for forming the second semiconductor layer onto the exposed surface of the first semiconductor layer and a surface of the insulating film,wherein in the step of forming the insulting film which contains the halogen element, a content of the halogen element in a surface portion of the insulating film is made higher than a content of the halogen element in an inside of the insulating film.

13. The method according to claim 12, wherein the halogen element is one of chlorine and bromine.

14. The method according to claim 12, wherein the insulating film is a silicon nitride film.

15. A method for fabricating a semiconductor device, the method comprising the steps of: supplying a material for suppressing growth of a second semiconductor layer over an insulating film onto a surface of a first semiconductor layer and a surface of the insulating film; andmaking the second semiconductor layer selectively epitaxial-grow over the first semiconductor layer by supplying a material for forming the second semiconductor layer onto the surface of the first semiconductor layer and the surface of the insulating film.

16. The method according to claim 15, wherein the material for suppressing the growth of the second semiconductor layer is gas which contains a halogen element.

17. The method according to claim 15, wherein in the step of supplying the material for suppressing the growth of the second semiconductor layer: gas which contains a halogen element is used as the material for suppressing the growth of the second semiconductor layer;the gas which contains the halogen element is supplied together with carrier gas; andwhen the gas which contains the halogen element is supplied, pressure in an atmosphere is between 10 and 10,000 Pa.

18. The method according to claim 15, wherein when the material for suppressing the growth of the second semiconductor layer is supplied, temperature of the first semiconductor layer is between 450 and 600° C.

19. The method according to claim 15, wherein when the second semiconductor layer is made to epitaxial-grow over the first semiconductor layer, substrate temperature is between 450 and 600° C.

20. The method according to claim 15, wherein in the step of supplying the material for suppressing the growth of the second semiconductor layer: gas which contains a halogen element is used as the material for suppressing the growth of the second semiconductor layer;the gas which contains the halogen element is supplied together with carrier gas;when the gas which contains the halogen element is supplied, pressure in an atmosphere is between 10 and 10,000 Pa; andpartial pressure of the gas which contains the halogen element is between 1 and 700 Pa.

21. The method according to claim 15, wherein in the step of supplying the material for suppressing the growth of the second semiconductor layer: gas which contains a halogen element is used as the material for suppressing the growth of the second semiconductor layer;the gas which contains the halogen element is supplied together with carrier gas;when the gas which contains the halogen element is supplied, pressure in an atmosphere is between 10 and 10,000 Pa; andpartial pressure of the carrier gas is higher than or equal to 1 Pa and is lower than 10,000 Pa.

22. A method for fabricating a semiconductor device, the method comprising the steps of: forming a gate electrode over a first semiconductor layer with a gate insulating film therebetween;forming an insulating film over side wall portions of the gate electrode;supplying a material for suppressing growth of a second semiconductor layer over the insulating film onto a surface of the first semiconductor layer and a surface of the insulating film; andmaking the second semiconductor layer selectively epitaxial-grow over the first semiconductor layer by supplying a material for forming the second semiconductor layer onto the surface of the first semiconductor layer and the surface of the insulating film.

23. The method according to claim 22, wherein the material for suppressing the growth of the second semiconductor layer is gas which contains a halogen element.