Multi-fin FINFET device including epitaxial growth barrier on outside surfaces of outermost fins and related methods

Abstract

A multi-fin FINFET device may include a substrate and a plurality of semiconductor fins extending upwardly from the substrate and being spaced apart along the substrate. Each semiconductor fin may have opposing first and second ends and a medial portion therebetween, and outermost fins of the plurality of semiconductor fins may comprise an epitaxial growth barrier on outside surfaces thereof. The FINFET may further include at least one gate overlying the medial portions of the semiconductor fins, a plurality of raised epitaxial semiconductor source regions between the semiconductor fins adjacent the first ends thereof, and a plurality of raised epitaxial semiconductor drain regions between the semiconductor fins adjacent the second ends thereof.

Claims

1. A device, comprising: a substrate having a surface; a plurality of first fins formed on and extending from the surface of the substrate, each fin of the plurality of first fins having a length that extends along a first axis; a first gate structure formed on the plurality of first fins; a plurality of first raised source regions formed on the surface of the substrate and between ones of the plurality of first fins; a plurality of first raised drain regions formed on the surface of the substrate and between ones of the plurality of first fins, the plurality of first raised drain regions being separated from the plurality of first raised source regions by the first gate structure; a first contact extending over first ends of the plurality of first fins, the plurality of first raised source regions being between the first contact and the first gate structure; and a gate contact formed on the substrate and abutting the first gate structure, the gate contact spaced from the plurality of first fins along a second axis that is transverse to the first axis.

2. The device of claim 1, further comprising a second contact extending over second ends of the plurality of first fins, the plurality of first raised drain regions being between the second contact and the first gate structure.

3. The device of claim 1, further comprising a plurality of second fins formed on and extending from the surface of the substrate, the plurality of second fins being adjacent to the plurality of first fins.

4. The device of claim 3, further comprising: a second gate structure formed on the plurality of second fins; a plurality of second raised source regions formed on the surface of the substrate and between ones of the plurality of second fins; and a plurality of second raised drain regions formed on the surface of the substrate and between ones of the plurality of second fins, the plurality of second raised drain regions being separated from the plurality of second raised source regions by the second gate structure.

5. The device of claim 4 wherein the first gate structure and the second gate structure are aligned and extend along a same direction.

6. The device of claim 4, further comprising: a first contact formed at a first end of the plurality of first fins, the plurality of first raised source regions being between the first contact and the first gate structure; a second contact formed at a second end of the plurality of first fins, the plurality of first raised drain regions being between the second contact and the first gate structure; a third contact formed at a first end of the plurality of second fins, the plurality of second raised source regions being between the third contact and the second gate structure; and a fourth contact formed at a second end of the plurality of second fins, the plurality of second raised drain regions being between the fourth contact and the second gate structure.

7. A device, comprising: a substrate; a plurality of fins on and extending from the substrate, each fin having a first end, a second end opposite the first end, and a central area between the first end and the second end; a gate on the central area of the plurality of fins; a plurality of source and drain regions positioned between the plurality of fins; a first contact covering the first ends of the plurality of fins; and a second contact on the second ends of the plurality of fins.

8. The device of claim 7 wherein the plurality of source regions are positioned between the gate and the first end.

9. The device of claim 8 wherein the plurality of drain regions are positioned between the gate and the second end.

10. The device of claim 7 wherein each of the plurality of fins includes silicon.

11. A method, comprising: forming a plurality of first fins on and extending from a surface of a substrate, each first fin having a first end and a second end opposite the first end, each fin of the plurality of first fins having a length between the first and second ends that extends along a first axis; forming a first gate structure on the plurality of first fins; forming a plurality of first raised source regions on the surface of the substrate and between ones of the plurality of first fins; forming a plurality of first raised drain regions on the surface of the substrate and between ones of the plurality of first fins, the plurality of first raised drain regions being separated from the plurality of first raised source regions by the first gate structure; forming a first contact surrounding the first ends of the plurality of first fins, the first contact extending along a second axis that is transverse to the first axis; and forming a second contact extending along the second ends of the plurality of first fins, the second contact extending along the second axis.

12. The method of claim 11, wherein the plurality of first raised source regions is between the first contact and the first gate structure.

13. The method of claim 12, wherein the plurality of first raised drain regions is between the second contact and the first gate structure.

14. The method of claim 11, further comprising forming a plurality of second fins formed on and extending from the surface of the substrate, the plurality of second fins being adjacent to the plurality of first fins.

15. The method of claim 14, further comprising: forming a second gate structure on the plurality of second fins; forming a plurality of second raised source regions on the surface of the substrate and between ones of the plurality of second fins; and forming a plurality of second raised drain regions on the surface of the substrate and between ones of the plurality of second fins, the plurality of second raised drain regions being separated from the plurality of second raised source regions by the second gate structure.

16. The method of claim 15 wherein forming the first gate structure and the second gate structure includes aligning the first and second gate structure along a same direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a CMOS multi-fin FINFET device in accordance with the invention.

(2) FIGS. 2A and 2B are side and top views, respectively, showing formation of the fins of the FINFET of FIG. 1.

(3) FIGS. 3A and 3B are side and top views, respectively, showing formation of tri-gates on the fins of the FINFET of FIG. 1.

(4) FIG. 4 is a side view showing an ion implantation step to form epitaxial growth barriers on outside surfaces of the outermost fins of the FINFET of FIG. 1.

(5) FIGS. 5A and 5B are side and top views, respectively, showing formation of epitaxial source and drain regions of the FINFET of FIG. 1.

(6) FIG. 6 is a flow diagram corresponding to the steps illustrated in FIGS. 2A, 2B, 3A, 3B, 4, 5A, and 5B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

(8) Referring initially to FIGS. 1-5, a multi-fin FINFET device 30 and associated method aspects are first described. In the illustrated example, the FINFET 30 is a complementary metal oxide semiconductor (CMOS) device including an NFET and a PFET. The FINFET 30 may be configured to provide various devices such as memories, logic gates, etc., using the contact regions described further below. However, it should be noted that non-CMOS configurations may be used in different embodiments as well (i.e., individual NFETs or PFETs).

(9) The FINFET 30 illustratively includes a substrate 31, which may be a semiconductor substrate (e.g., silicon, germanium, Si/Ge, etc.), a semiconductor on insulator (SOI) substrate, etc. Furthermore, a plurality of semiconductor fins 32n, 32p for respective NFET and PFET devices extend upwardly from the substrate 31, and are laterally spaced apart along the substrate (left to right in FIGS. 2A, 2B). In FIGS. 2A, to 5B, the NFET is on the left and the PFET is on the right. Each semiconductor fin 32n, 32p respectively has opposing first and second ends 33a, 33b and 34a, 34b, and a respective medial portion 35a, 35b therebetween (indicated with dashed lines in FIG. 2B). Outermost fins of the plurality of semiconductor fins (i.e., the fins 32n, 32p on the far left and right of their respective sets of fins) comprise an epitaxial growth barrier 35n, 35p on outside surfaces thereof, as will be described further below.

(10) The FINFET 30 further illustratively includes respective gates 37n, 37p for the NFET and PFET, which overlie the respective medial portions 35a, 35b of the fins 32n, 32p. More particularly, the gates 37n, 37p are tri-gate structures, each of which may include an insulator layer and an electrode layer overlying the insulator layer. In addition, a plurality of raised epitaxial semiconductor source regions 38n, 38p extend between the semiconductor fins 32n, 32p adjacent the first ends 33a, 34a thereof, respectively. Moreover, a plurality of raised epitaxial semiconductor drain regions 39n, 39p extend between the semiconductor fins 32n, 32p adjacent the second ends 33b, 34b thereof. The FINFET 30 further illustratively includes gate contact regions 40n, 40p respectively coupled to the gates 37n, 37p and extending upwardly from the substrate 31 and spaced apart from the semiconductor fins 40n, 40p (FIG. 1). Similarly, respective source contact regions 41n, 41p are coupled to the first ends 33a, 34a of the semiconductor fins 32n, 32p, and respective drain contact regions 42n, 42p are coupled to the second ends 33b, 34b of the semiconductor fins 32n, 32p.

(11) As noted above, multi-fin FINFETs are advantageous in that the effective gate width is 2nh, where n is the number of fins and h is the fin height. Accordingly, wider transistors with higher on-currents may be obtained by using multiple fins. However, when source/drain epitaxial growth is used to merge the fins 32n, 32p to lower the external resistance, epitaxial growth will otherwise occur between the two sets of fins. That is, not only is there intra-fin growth of the epitaxial semiconductor material between the fins 32n, and 32p, in a typical FINFET integration process there will be inter-fin growth between the two sets of fins, for example. This may otherwise be problematic in that it can cause shorting between the NFET and PFET fins 32n, 32p. The above-noted epitaxial growth barriers 36n, 36p advantageously help constrain epitaxial growth to intra-fin growth to interior or inner fin surfaces between the fins 32n, 32p, and thus reduce a likelihood of shorting between the NFET and PFET devices.

(12) An example approach for fabricating the FINFET 30 with the epitaxial growth barriers 36n, 36p will now be described further with reference to the flow diagram 60 of FIG. 6. Beginning at Block 61, the semiconductor (e.g., silicon, germanium, Si/Ge, etc.) fins 32n, 32p are formed extending upwardly from the substrate 31 and are spaced apart along the substrate, as noted above, at Block 62 (FIGS. 2A and 2B). The gates 37n, 37p are then formed overlying the medial portions 35a, 35b of the semiconductor fins 32n, 32p, respectively, at Block 63. Again, with a tri-gate structure, the gates 37n, 37p (which respectively include an insulator layer and a gate electrode layer) will wrap around the top and side surfaces of the fins 32n, 32p, as seen in FIGS. 3A, 3B.

(13) The method further includes forming the epitaxial growth barriers 36n, 36p on outside surfaces of the outermost fins from the sets of fins 32n, 32p, as noted above, at Block 64. More particularly, this may be done by performing an ion implantation at an angle offset from normal to the substrate 31, as represented by the dashed arrows in FIG. 4. More particularly, a dual-angled implant/reactive ion etch (RIE) may be performed using Carbon-Fluorine (e.g., CF4) or other suitable gases. As a result, the epitaxial growth barriers 36n, 36p will comprise a compound including the semiconductor fin material (e.g., silicon, etc.), carbon and/or fluorine components. The epitaxial growth barriers 36n, 36p will appear as a film or coating, and they will inhibit grow of epitaxial semiconductor material during formation of the raised source regions 38n, 38p and drain regions 39n, 39p, at Blocks 65-66 (FIGS. 5A, 5B), which illustratively concludes the method shown in FIG. 6 (Block 67).

(14) The angle of implantation may be chosen so as not to be too steep, and thereby allow ion penetration too deep between the fins 32n or 32p, yet not too shallow so that the outside surfaces of the sets of fins facing one another do not get coated on the bottom (which would allow excessive inter-fin epitaxial growth that could result in shorting between the NFET and PFET devices, as described above). Generally speaking, the angle of implantation may be in a range of 30 to 60 degrees, depending upon the height and lateral spacing of the fins 32n, 32p which are used in a given embodiment. Because the inner surfaces of the fins 32n, 32p are blocked from ion bombardment by the adjacent fins, these inner surfaces will have relatively little impact or damage from the implantation, and will thereby still allow for the subsequent epitaxial source and drain growth. With proper angle selection only a small portion of these inner surfaces near the tops of the fins 32n, 32p will be impacted by the implantation and thereby have epitaxial growth barriers 36n, 36p formed thereon, as shown in FIGS. 4 and 5A.

(15) It will therefore be appreciated that that the above-described approach may be relatively easy to implement, in that an additional step (i.e., the ion implantation) may be added to a multi-fin FINFET fabrication process to provide the epitaxial growth barriers 36n, 36p and reduce the likelihood of shorting in the finished device. That is, the above-described approach advantageously allows for relatively high density multi-fin configurations to be fabricated without the epitaxial merging between the NFETs and PFETs. The epitaxial growth barriers 36n, 36p may provide desired retardation of epitaxial growth, so that this growth is confined to the inner surfaces of the fins 32n, 32p where desired.

(16) Many modifications and other embodiments of the invention will come to the mind of one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is understood that the invention is not to be limited to the specific embodiments disclosed, and that modifications and embodiments are intended to be included within the scope of the appended claims.