N- AND P-TYPE 2D CHANNELS VIA SURFACE CHARGE TRANSFER FROM A DOPED OXIDE

Abstract

A doped binary oxide high-k gate dielectric has the following formula M.sub.1-xN.sub.xO.sub.2, wherein MHf, Zr, or Si, NTa, Nb, Re, Os, or Ru, and 0<x<0.2, or the following formula M.sub.1-xP.sub.xO.sub.2, wherein MHf, Zr, or Si, PCo, Bi, Fe, Y, Al, or B, and 0<x<0.2. A method for doping a transition metal dichalcogenide layer includes doping a binary oxide high-k gate dielectric layer to provide the aforementioned doped binary oxide high-k gate dielectric and thereby dope the transition metal dichalcogenide layer by surface charge transfer doping.

Claims

1. A doped binary oxide high-k gate dielectric of the following formula (1): ##STR00003## wherein MHf, Zr, or Si, NTa, Nb, Re, Os, or Ru, and 0<x<0.2, or the following formula (2): ##STR00004## wherein MHf, Zr, or Si, PCo, Bi, Fe, Y, Al, or B, and 0<x<0.2.

2. The doped binary oxide high-k gate dielectric of claim 1, wherein the doped binary oxide high-k gate dielectric is a doped binary oxide high-k gate dielectric of formula (1).

3. The doped binary oxide high-k gate dielectric of claim 2, wherein NTa.

4. The doped binary oxide high-k gate dielectric of claim 2, wherein NNb.

5. The doped binary oxide high-k gate dielectric of claim 2, wherein NRe.

6. The doped binary oxide high-k gate dielectric of claim 2, wherein NOs.

7. The doped binary oxide high-k gate dielectric of claim 2, wherein NRu.

8. The doped binary oxide high-k gate dielectric of claim 1, wherein the doped binary oxide high-k gate dielectric is a doped binary oxide high-k gate dielectric of formula (2).

9. The doped binary oxide high-k gate dielectric of claim 8, wherein PCo, Bi, or Fe.

10. The doped binary oxide high-k gate dielectric of claim 8, wherein PCo.

11. The doped binary oxide high-k gate dielectric of claim 8, wherein PBi.

12. The doped binary oxide high-k gate dielectric of claim 8, wherein PFe.

13. The doped binary oxide high-k gate dielectric of claim 2, wherein MHf.

14. The doped binary oxide high-k gate dielectric of claim 8, wherein MHf.

15. The doped binary oxide high-k gate dielectric of claim 9, wherein MHf.

16. A method for doping a transition metal dichalcogenide layer, comprising doping a binary oxide high-k gate dielectric layer to provide a doped binary oxide high-k gate dielectric of claim 1 and thereby dope the transition metal dichalcogenide layer by surface charge transfer doping.

17. The method of claim 16, wherein the method is a method for n-doping a transition metal dichalcogenide layer, comprising doping a binary oxide high-k gate dielectric layer to provide a doped binary oxide high-k gate dielectric of formula (1) and thereby n-dope the transition metal dichalcogenide layer by surface charge transfer doping.

18. The method of claim 16, wherein the method is a method for p-doping a transition metal dichalcogenide layer, comprising doping a binary oxide high-k gate dielectric layer to provide a doped binary oxide high-k gate dielectric of formula (2) and thereby p-dope the transition metal dichalcogenide layer by surface charge transfer doping.

19. The method of claim 18, wherein PCo, Bi, or Fe.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0041] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0042] Example embodiments of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which:

[0043] FIG. 1 is a graph showing the metronomic progress in CMOS transistor density and switching energy over time.

[0044] FIG. 2 shows a representative transistor structure.

[0045] FIG. 3 is a graph showing the mobility () of electrons as a function of channel thickness (t.sub.CH), and illustrates that for Si on insulators (SOI), the mobility degrades when t.sub.CH is below 4 nm, while transition metal dichalcogenides (MoS.sub.2, WSe.sub.2, etc.) show robust mobility for thinner channels.

[0046] FIG. 4 is a schematic energy level diagram of surface charge transfer doping (SCTD) between organic molecules and MoS.sub.2, and illustrates depletion and a n-doping process via SCTD of organic molecules with higher electron affinity (EA) than the ionization energy (IE) of TMDs.

[0047] FIG. 5 shows graphs considering TMD interfaced with Hf.sub.(1-x)M.sub.xO.sub.2 where the interface HfO.sub.2 layer is replaced by MO.sub.2 layer (results in this figure are for the interface and show n-doping of WSe.sub.2, in blue).

[0048] FIGS. 6A-6F show larger versions of the subfigures of FIG. 5.

[0049] FIG. 7A is a graph showing the charge transferred to the TMD layer for various n-dopants to dope Hf in an HfO.sub.2 interface layer, and FIG. 7B is a graph showing the charge transferred to the TMD layer for various p-dopants to dope Hf in an HfO.sub.2 interface layer.

[0050] FIG. 8 shows the estimated ionization energy (vacuum level set as zero-reference) of typical oxides used as dielectrics.

[0051] FIGS. 9A-9E are supplemental graphs showing the density of states vs. energies for various dopants.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0052] As mentioned above, the present disclosure provides a list of chemistries to n-dope and p-dope transition metal dichalcogenides (TMDs: MoS.sub.2, WSe.sub.2, MoSe.sub.2, WS.sub.2) using a binary oxide high-k gate dielectric like HfO.sub.2, ZrO.sub.2, or SiO.sub.2 and chemical combinations of them by n-doping the oxide layer with {Ta, Nb, Re, Os, Ru} within the fractional (x) limit 0<x<0.2 or by p-doping the oxide layer with {Co, Bi, Fe, Y, Al, B} within the fractional (x) limit 0<x<0.2.

[0053] HfO.sub.2 is a well studied high-k dielectric binary oxide. The band alignment of HfO.sub.2 is not directly favorable for substrate n-doping TMDsthe CBM of pristine HfO.sub.2 is above the VBM of TMDs.

[0054] FIG. 5 shows graphs considering TMD interfaced with Hf (1-x) M.sub.xO.sub.2 where the interface HfO.sub.2 layer is replaced by MO.sub.2 layer (results in this figure are for WSe.sub.2). The subfigures in FIG. 5 are shown individually in FIGS. 6A-6F. The band alignment of Hf (1-x) M.sub.xO.sub.2 interfaced with WSe.sub.2 shows that the CBM of TMD layer is occupied, thereby doping the TMD layer. The charge is transferred from the interface TMD layer.

[0055] FIGS. 7A and 7B show the charge transferred to the TMD layer for various dopant candidates to dope Hf in HfO.sub.2 interface layer. In particular, FIG. 7A is a graph showing the charge transferred to the TMD layer for various n-dopants (Ta, Nb, Re, Os, Ru) to dope Hf in an HfO.sub.2 interface layer, and FIG. 7B is a graph showing the charge transferred to the TMD layer for various p-dopants (Co, Bi, Fe, Y, Al, B) to dope Hf in an HfO.sub.2 interface layer.

[0056] Thus, the present disclosure shows cation doping of HfO.sub.2 with transition metals whose oxides lead to a charge transfer from the oxide layer to the TMD layer.

[0057] FIG. 8 shows the ionization energy of typical oxides used as dielectrics estimated by computing the vacuum levels and the valance bands of a monolayer slab of oxide. Assuming that the relative position of the dopant bands relative to the shared oxygen atoms are the same, the relative band shift between the different surfaces can be estimated by computing the ionization energies of the surfaces. Given that the dopant levels are lower (SiO.sub.2) or similar (ZrO.sub.2) in energy to HfO.sub.2, they are expected to transfer electrons to TMD.

[0058] Thus, the results provided by the present disclosure reveal that the relative band alignment in conventional high-k oxides can be modified by the doping strategy of the present disclosure. This should result in n-doping or p-doping the neighboring TMD layer. For doping in the range 0<x<0.2, the dielectric constant of the high-k layer is expected to retained with 80% accuracy.

[0059] As supplemental information, FIGS. 9A-9E are graphs showing the density of states vs. energies for various dopants, namely, the n-dopants Nb, Ta, Re, Ru, and Os, respectively.

[0060] The atomic doping of the high-k layer in the present disclosure can be achieved using typical growth methods like thermal oxidation, atomic layer deposition, pulsed laser deposition, chemical vapor deposition, plasma oxidation, wet anodization or other chemical treatments.

[0061] By carrying out a method like one of the above methods, a structure of the present disclosure can be obtained.

[0062] The present disclosure can be used to improve the performance of existing transistors by integrating atomically thin 2D materials as channel layers.

[0063] The foregoing is illustrative of exemplary embodiments and is not to be construed as limiting the disclosure. Although a few exemplary embodiments have been described, those skilled in the art will readily appreciate that many modifications are possible in the above embodiments without materially departing from the disclosure.