Multilayer high k dielectric films and method of making the same
A new multilayer dielectric film for improving dielectric constant and thermal stability of gate dielectrics is provided. The multilayer dielectric film comprises a first layer formed of a metal oxide material having a high dielectric constant, and a second layer formed on the first layer. The second layer is formed of a metal silicate material having a dielectric constant lower than the dielectric constant of the first layer. A semiconductor transistor incorporating the multilayer dielectric film is also provided.
This application is divisional of U.S. application Ser. No. 10/056,625, filed Jan. 25, 2002, which claims the benefit of U.S. Provisional Application No. 60/264,428 filed Jan. 26, 2001, entitled “Multilayer High Dielectric Constant Oxide Films and Method of Making”, the entire disclosures of which are incorporated herein by reference.
FIELD OF THE INVENTION The present invention relates generally to the field of semiconductors. More specifically, the present invention relates to multilayer high dielectric constant (
Design and manufacturing of integrated circuits (ICs) are becoming increasingly complex as the device density of such circuits increases. High density circuits require closely spaced devices and interconnect lines, as well as multiple layers of materials and structures.
To address this problem, alternative gate dielectric materials have recently been investigated. One approach is to replace the SiO2 gate dielectric with a material that has a higher dielectric constant (
In the prior art, a number of different high
More recently, zirconium silicate (ZrSixOy) and hafnium silicate (HfSixOy) have been investigated as new gate dielectric materials. For example, zirconium silicate gate dielectrics have been reported in “Stable zirconium silicate gate dielectrics deposited directly on silicon” by G. D. Wilk and R. M. Wallace, Applied Physics Letters, Volume 76, Number 1, Jan. 3, 2000 pp. 112-114 and in “Electrical properties of hafnium silicate gate dielectrics deposited directly on silicon” by G. D. Wilk et al., Applied Physics Letters, Volume 74, 1999 pp. 2854-2856. Zirconium silicate and Hafnium silicate are of particular interest as an alternative gate dielectric material because of its relatively high dielectric constant value. Its dielectric constant is marginally increased to about 10 to 15 depending upon the ZrOx/HfOx content in the film. Moreover, zirconium or hafnium silicate exhibits thermal stability in direct contact with the silicon substrate. However, the dielectric constant is not as high as seen with other materials, and such films have not been successfully employed in commercial operation. Accordingly, a significant need exists for the development of high dielectric constant films.
SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a high dielectric constant (
It is further an object of the present invention to provide a semiconductor transistor that incorporates the high
Another object of the present invention to provide a method of making a high
These and other objects are achieved by a new multilayer dielectric film of the present invention employing metal silicates on a silicon substrate and metal oxides having high
In accordance with the present invention, there is provided a multilayer dielectric film that comprises a first layer formed of a material having a high dielectric constant, and a second layer formed on the first layer. The second layer is formed of a material having a dielectric constant lower than the dielectric constant of the first layer. The first layer is preferably comprised of a metal oxide material having a dielectric constant in the range of 15 to 200, and the second layer is preferably comprised of a metal silicate material having a dielectric constant in the range of 5 to 100.
In one preferred embodiment, the multilayer dielectric film of the present invention comprises a first layer of a metal oxide having the formula of MxOy, and a second layer of a metal silicate having the formula of MxSiOy, where M is a metal independently selected from the group consisting of Zr, Hf, Ti, V, Nb, Ta, Cr, Mo, W, Mn, Zn, Al, Ga, In, Ge, Sr, Pb, Sb, Bi, Sc, Y, La, Be, Mg, Ca, Sr, Ba, Th, Lanthanides (Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), and mixtures thereof, x is a number in the range of 1 to 3, and y is a number in the range of 2 to 5. Each of the metal oxide first layer and metal silicate second layer may contain more than one metal elements. The metal in the first and second layers can be same and/or different.
In another preferred embodiment, the multilayer dielectric film of the present invention comprises a first layer of a metal oxide selected from the group consisting of ZrO2 and HfO2, and a second layer of a metal silicate selected from the group consisting of Zr—Si—O and Hf—Si—O.
In another embodiment of the present invention, the multilayer dielectric film of the present invention comprises a first layer having a first and second surfaces, a second layer formed on the first surface of the first layer, and a third layer formed on the second surface of the first layer, wherein the second and third layers are comprised of a material having a dielectric constant lower than the dielectric constant of the first layer.
In another aspect of the present invention, there is provided a method of forming a multilayer dielectric film on a substrate. The method comprises the steps of forming a metal silicate layer on the surface of a substrate, and forming a metal oxide layer atop the metal silicate layer. In one embodiment, the method further comprises forming another metal silicate layer atop the metal oxide layer. The forming step can be carried out by chemical vapor deposition, physical vapor deposition, atomic layer deposition, aerosol pyrolysis, spray coating or spin-on-coating.
BRIEF DESCRIPTION OF THE FIGURESThe foregoing and other objects of the invention will be more clearly understood from the following description when read in conjunction with the accompanying drawings in which:
The dielectric constant of the first layer 12 is preferably greater than about 15, more preferably in the range of about 15 to 200, most preferably in the range of about 25-100. The dielectric constant of the second layer 14 is preferably greater than about 5, and more preferably in the range of about 10 to 100.
The first layer 12 of the multilayer dielectric film 5 is comprised of a metal oxide having the formula of MxOy, where M is a metal selected from the group consisting of Zr, Hf, Ti, V, Nb, Ta, Cr, Mo, W, Mn, Zn, Al, Ga, In, Ge, Sr, Pb, Sb, Bi, Sc, Y, La, Be, Mg, Ca, Sr, Ba, Th, Lanthanides (Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu), and mixtures thereof, x is a number in the range of 1 to 3, and y is a number in the range of 2 to 5. The second layer 14 of the multilayer dielectric film 5 is comprised of a metal silicate having the formula of MxSiOy, where M is a metal selected from the group consisting of Zr, Hf, Ti, V, Nb, Ta, Cr, Mo, W, Mn, Zn, Al, Ga, In, Ge, Sr, Pb, Sb, Bi, Sc, Y, La, Be, Mg, Ca, Sr, Ba, Th, Lanthanides (Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu), and mixtures thereof, x is a number in the range of 1 to 3, and y is a number in the range of 2 to 5. Each of the metal oxide first layer 12 and metal silicate second layer 14 may contain more than one metal elements. The metal in the first layer 12 and second layer 14 can be the same or different.
Preferably, the thickness of the first layer 12 of the multilayer dielectric film 5 is formed greater than the thickness of the second layer 14 in order to promote a high dielectric value for the entire dielectric structure. Alternatively, the thickness of the first layer 12 and the second layer 14 can be similar. In one embodiment, the second layer 14 has a thickness of only one or two atomic layers, so that the first layer 12 may be much thicker. In another embodiment where the first layer 12 of the multilayer dielectric film 5 is ZrO2 ( the dielectric constant of ZrO2 is 25 which is six times as high as that of SiO2), the thickness of the first layer 12 is about 60 Å. A thickness of 60 Å of ZrO2 first layer behaves approximately same as a thickness of 10 Å of SiO2 first layer (Tox, eq) with regard to electrical properties.
The first layer 12 is comprised of a metal oxide having the formula of MxOy where M, x and, y are defined as above. The second layers 14 are comprised of a metal silicate having the formula of MxSiOy, where M, x, and y are defined as above. The metal in the first metal oxide layer 12 and the second metal silicate layers 14 can be the same or different. Preferably, the metal in the first layer 12 and second layers 14 is comprised of the same metal component for ease of processing.
In one preferred embodiment of the present invention, the first layer 12 of the multilayer dielectric film 10 is formed of a material selected from the group consisting of ZrO2 and HfO2. The second layers 14 are formed of a material selected from the group consisting of Zr—Si—O and Hf—Si—O.
The gate 22 can be comprised of doped polysilicon or conductive materials. The multilayer dielectric film 10 comprises a first layer 12 having a high dielectric constant and at least one second layer 14 having a lower dielectric constant. The at least one second layer 14 is in contact with the surface of silicon substrate 16. The first layer 12 is comprised of a metal oxide having the formula of MxOy where M, x and, y are defined as above. The at least one second layer 14 is comprised of a metal silicate having the formula of MxSiOy, where M, x, and y are defined as above.
In another aspect of the present invention, a method of forming a multilayer dielectric film on a substrate is provided. In one embodiment, the method generally comprises the steps of: forming a metal silicate layer on the surface of a substrate, and forming a metal oxide layer atop the metal silicate layer. In another embodiment, where the first layer 12 of the multilayer dielectric film 10 is sandwiched between two second layers 14 as illustrated in
The forming steps may be carried out in a variety of ways. For example the forming step may be carried out by deposition or by coating as know in the art. Suitable deposition methods include, but are not limited to, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), and aerosol pyrolysis. PVD further includes sputtering and e-beam evaporation techniques. CVD further includes thermal, plasma, laser, and photo assisted CVD. CVD methods employ an oxygen source. The source of oxygen includes O2, O3, NO, N2O, H2O, alcohol, alkoxides, OH—, and Hydrogen Peroxide (H2O2). Suitable coating methods include spray coating and spin-on-coating techniques from liquid source materials, organic solutions, or aqueous solutions. Any one of the layers can be formed by any one of the above methods and may be carried out by those of ordinary skill in the art.
One advantage of the multilayer dielectric film of the present invention is that it achieves higher dielectric constant values than the metal silicate single layer described in the prior art. The higher dielectric constant values allow thicker gate dielectric components and, therefore, lead to better electrical properties in the MOS device architecture, such as lower leakage current, higher breakdown voltage, more resistant to boron penetration, and the like.
Another advantage of the multilayer dielectric film of the present invention is that it can significantly improve the stability of the high
MO2+Si→MSi+SiOx
The formation of additional silicon oxide (
While the present invention is disclosed by reference to the preferred embodiments and examples detailed above, it is to be understood that these examples are intended in an illustrative rather than limiting sense, as it is contemplated that modifications and combinations will readily occur to those skilled in the art, which modifications and combinations will be within the scope of the invention and the scope of the appended claims.
Claims
1. A method of forming a multilayer dielectric film on a substrate, comprising the steps of:
- forming a metal silicate layer on the surface of the substrate; and
- forming a metal oxide layer atop the metal silicate layer.
2. The method of claim 1, further comprising:
- forming another metal silicate layer atop the metal oxide layer.
3. The method of claim 1 or 2 wherein said forming steps are carried out by any one of, or combination of, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), aerosol pyrolysis, spray coating or spin-on-coating.
4. The method of claim 1 or 2 wherein said forming steps are carried out by chemical vapor deposition (CVD) and using an oxygen source selected from the group consisting of O2, O3, NO, N2O, H2O, OH−, alcohol, alkoxides, and H2O2.
5. The method of claim 1 or 2 wherein said metal oxide layer has a dielectric constant K; and said metal silicate layer has a dielectric constant lower than the dielectric constant of said metal oxide layer.
6. The method of claim 5 wherein said metal oxide layer has a dielectric constant in a range of 15 to 200 and said metal silicate layer has a dielectric constant in a range of 5 to 100.
7. The method of claim 5 wherein said metal oxide has the formula of MxOy, where M is a metal selected from the group consisting of Zr, Hf, Ti, V, Nb, Ta, Cr, Mo, W, Mn, Zn, Al, Ga, In, Ge, Sr, Pb, Sb, Bi, Sc, Y, La, Be, Mg, Ca, Sr, Ba, Th, Lanthanides (Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), and mixtures thereof, x is a number in the range of 1 to 3, and y is a number in the range of 2 to 5.
8. The method of claim 7 wherein said metal oxide includes more than one metal element.
9. The method of claim 5 wherein said metal oxide is selected from the group consisting of ZrO2 and HfO2.
10. The method of claim 5 wherein said metal silicate has the formula of MxSiOy, where M is a metal selected from the group consisting of Zr, Hf, Ti, V, Nb, Ta, Cr, Mo, W, Mn, Zn, Al, Ga, In, Ge, Sr, Pb, Sb, Bi, Sc, Y, La, Be, Mg, Ca, Sr, Ba, Th, Lanthanides (Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), and mixtures thereof, x is a number in the range of 1 to 3, and y is a number in the range of 2 to 5.
11. The method of claim 10 wherein said metal silicate includes more than one metal element.
12. The method of claim 10 wherein said metal silicate is selected from the group consisting of Zr—Si—O and Hf—Si—O.
13. The method of claim 1 or 2 wherein said metal silicate layer has a thickness smaller than a thickness of said metal oxide.
14. The method of claim 13 wherein said metal oxide layer has a thickness in a range of about 30 to 80 Å.
15. The method of claim 13 wherein said second metal silicate layer has a thickness of one to two atomic layers.
Type: Application
Filed: Jan 27, 2004
Publication Date: Mar 24, 2005
Inventor: Yoshihide Senzaki (Aptos, CA)
Application Number: 10/766,618