STRUCTURE AND METHOD TO MINIMIZE REGROWTH AND WORK FUNCTION SHIFT IN HIGH-K GATE STACKS
The present invention provides a semiconductor structure comprising high-k material portions that are self-aligned with respect to the active areas in the semiconductor substrate and a method of fabricating the same. The high-k material is protected from oxidation during the fabrication of the semiconductor structure and regrowth of the high-k material and shifting of the high-k material work function is prevented.
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This application is a divisional of co-pending application Ser. No. 12/557,394, filed on Sep. 11, 2009, and for which priority is claimed under 35 U.S.C. §120; the entire contents of which is are hereby incorporated by reference.
FIELD OF THE INVENTIONThe present invention generally relates to semiconductor devices, and particularly to semiconductor devices comprising high-k dielectric gate portions, and methods of manufacturing the same.
BACKGROUND OF THE INVENTIONMaterials with a high dielectric constant, referred to herein as high-k materials or as high-k gate materials, are utilized in high-k gate complementary metal oxide semiconductor (CMOS) technology. In CMOS devices having a silicon channel, a conductive material having a work function of about 4.0 eV is necessary for n-type metal oxide semiconductor field effect transistors (NMOSFETs) and another conductive material having a work function of about 5.0 eV is necessary for p-type metal oxide semiconductor field effect transistors (PMOSFETs). In conventional high-k gate CMOS fabrication, the high-k material of the gate stack, specifically hafnium oxide dielectrics, are prone to re-growth. Further, the workfunction of the high-k gate material may shift if the high-k material is exposed to oxygen during processing or comes into contact with oxygen-containing materials, such as silicon dioxide, SiO2. Additionally, the gate stack can grow thicker as a result of the thermal budget and presence or contact of the hafnium with the SiO2.
In conventional CMOS devices employing polysilicon gate materials, a heavily p-doped polysilicon gate and a heavily n-doped polysilicon gate are employed to address the needs. In CMOS devices employing high-k gate dielectric materials, suitable materials satisfying the work function requirements are needed. So far, identification of materials for a dual work function metal gate electrode system has presented some challenges. Moreover, finding high k gate stack materials suitable for gate first applications where the dielectric materials are subjected to high thermal budgets is a challenge.
The current state of the art in fabrication of high k gate stack transistors involves forming shallow trench isolation to separate nFET regions from pFET regions, depositing high k, metals, and poly silicon. The gate stack materials are then patterned using photolithographic techniques and reactive ion etching to form the gate electrode. Thus, in instances where the gate electrode is shared between nFET regions and pFET regions, the gate electrode will also be in contact with the SiO2 material from the shallow trench isolation. It may be possible to remove the high k materials from being in contact with the shallow trench isolation regions by a costly photo lithographic and etching technique. However, this technique would suffer the overlay and critical dimension variations inherent in photolithographic techniques.
In view of the above, there exists a need for reliable forming a semiconductor structure wherein the high-k material layer is precisely aligned to the active region in the silicon substrate and wherein the exposure of the high-k material to oxygen is minimized.
SUMMARY OF THE INVENTIONThe present invention addresses the needs described above by providing a method of fabricating high-k material semiconductor structures in which regrowth of the high-k material is prevented and threshold voltage shifts are minimized. Further, the resulting semiconductor structures comprise high-k material regions that are self-aligned with respect to the active areas in the semiconductor substrate.
According to an embodiment of the present invention, a semiconductor structure is formed by subsequently forming an interface layer on a semiconductor substrate and a high-k material layer on the interface layer. Thereafter, a metallic layer is formed on the high-k material layer, an amorphous silicon layer is formed on the metallic layer, and a silicon nitride layer is formed on the amorphous silicon layer. A shallow trench is developed in the semiconductor structure by photolithography and a trench etch, a trench liner is formed on the trench structure. Next, a shallow trench isolation is deposited in the shallow trench and a shallow trench recess is developed. After that, the silicon nitride layer, the amorphous silicon layer, and the metallic layer are removed and a standard CMOS process flow may be used.
The resulting semiconductor structure is a self-aligned high-k material semiconductor structure comprising a semiconductor substrate comprising a shallow trench; and a plurality of high-k material layer portions on the semiconductor substrate, wherein an interface layer is located between each portion from among the plurality of high-k material layer portions and the semiconductor substrate; wherein the high-k material layer portions are co-linear with the semiconductor substrate.
As stated above, the present invention relates to semiconductor structures having a high-k material portion. Such semiconductor structures are useful in the fabrication of semiconductor devices, for example, in the fabrication of complementary metal-oxide-semiconductor (CMOS). Semiconductor structures and methods of manufacturing the same are now described in detail with accompanying figures. The term “semiconductor structure” is used herein to refer to the semiconductor substrate and any subsequently formed structures on the semiconductor substrate. Thus, semiconductor structure may refer to, for example, to a semiconductor structure before and after a photoresist is applied onto the semiconductor structure.
Referring to
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In a preferred embodiment, a nitride content is added to the interface layer by nitridation. If the interface layer 20 comprises silicon dioxide, at least some silicon dioxide is converted into silicon nitride. Nitridation is performed by methods known in the art, for example, by remote plasma nitridation (RPN) or by deep plasma nitridation (DPN), or NH3 bake process.
Referring to
The dielectric metal oxide is a high-k material containing a metal and oxygen, and is known in the art as high-k gate dielectric materials. Exemplary high-k dielectric material include HfO2, ZrO2, La2O3, Al2O3, TiO2, SrTiO3, LaAlO3, Y2O3, HfOxNy, ZrOxNy, La2OxNy, Al2OxNy, TiOxNy, SrTiOxNy, LaAlOxNy, Y2OxNy, a silicate thereof, and an alloy thereof. Each value of x is independently from about 0.5 to about 3 and each value of y is independently from 0 to about 2. Typically, the thickness of the high-k material layer 30 is from about 0.9 nm to about 6 nm, and more typically from about 1.2 nm to about 3 nm. The high-k material layer 30 may have an effective oxide thickness on the order of or less than 1 nm.
In an alternate embodiment (not shown in the figures) capping layers are deposited and patterned over the n and p regions respectively to create appropriate work function shifts for nMOs and pMOS respectively.
Referring to
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The liner protects the high-k material from contacting the shallow trench isolation material that is deposited next. The semiconductor structure and the method of fabricating the same disclosed herein provide the benefit of protecting the high-k material from exposure to reagents capable of shifting the work function, in particular oxygen while requiring only a single lithography step. The diffusion of oxygen or other gas molecules into the high-k material 30 during subsequent processing steps is prevented by the oxygen-impermeable liner 70, thus keeping the composition of the high-k material portion 30 constant. Particularly, the material of the high-k material portion 30 is not subjected to further oxidation during subsequent processing steps. Thus, the high-k material portion 30, which is the gate dielectric material of a first gate stack structure maintains constant composition.
Referring to
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At this point in the inventive process flow a standard gate first process or a standard gate last type process can is used to complete the CMOS circuit processing.
It is noted that the formation of the metallic layer and of the silicon layer is optional, that is that the formation, and thus the subsequent removal of either one or both of the metallic layer and of the silicon layer may be omitted.
Referring to
The high-k material portions 30′ and 30″ indicated in
The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “having” or “including” and not in the exclusive sense of “consisting only of” The terms “a” and “the” as used herein are understood to encompass the plural as well as the singular.
All publications, patents and patent applications cited in this specification are herein incorporated by reference, and for any and all purpose, as if each individual publication, patent or patent application were specifically and individually indicated to be incorporated by reference. In the case of inconsistencies, the present disclosure will prevail.
The foregoing description of the disclosure illustrates and describes the present disclosure. Additionally, the disclosure shows and describes only the preferred embodiments but, as mentioned above, it is to be understood that the disclosure is capable of use in various other combinations, modifications, and environments and is capable of changes or modifications within the scope of the concept as expressed herein, commensurate with the above teachings and/or the skill or knowledge of the relevant art.
The embodiments described hereinabove are further intended to explain best modes known of practicing it and to enable others skilled in the art to utilize the disclosure in such, or other, embodiments and with the various modifications required by the particular applications or uses. Accordingly, the description is not intended to limit it to the form disclosed herein. Also, it is intended that the appended claims be construed to include alternative embodiments.
Claims
1. A self-aligned high-k material semiconductor structure comprising:
- a semiconductor substrate comprising a shallow trench; and
- a plurality of high-k material layer portions on the semiconductor substrate, wherein an interface layer is located between each portion from among the plurality of high-k material layer portions and the semiconductor substrate;
- wherein the high-k material layer portions are co-linear with the semiconductor substrate.
2. The self-aligned high-k material semiconductor structure according to claim 1, wherein a trench liner is abutting the shallow trench and at least one of the high-k material layer portions.
3. The self-aligned high-k material semiconductor structure according to claim 1, wherein the high-k material portion comprises one of HfO2, ZrO2, La2O3, Al2O3, TiO2, SrTiO3, LaAlO3, Y2O3, HfOxNy, ZrOxNy, La2OxNy, Al2OxNy, TiOxNy, SrTiOxNy, LaAlOxNy, Y2OxNy, a silicate thereof, and an alloy thereof, wherein each value of x is independently of from about 0.5 to about 3 and each value of y is independently of from 0 to about 2.
4. The self-aligned high-k material semiconductor structure according to claim 1, wherein the shallow trench separates a p-doped region within the semiconductor substrate from a n-doped region within the semiconductor substrate.
5. The self-aligned high-k material semiconductor structure according to claim 1, further comprising a metallic layer cap on at least one of the high-k material portions.
6. The self-aligned high-k material semiconductor structure according to claim 5, wherein the metallic layer cap comprises one of TiN, ZrN, HfN, VN, NbN, TaN, WN, TiAlN, TaCN, W, Ta, Ti, or an alloy thereof.
7. The self-aligned high-k material semiconductor structure according to claim 1, wherein the semiconductor substrate is a semiconductor-on-insulator (SOI).
8. The self-aligned high-k material semiconductor structure according to claim 1, wherein the high-k material has a dielectric constant of 8.0 or greater.
9. The self-aligned high-k material semiconductor structure according to claim 1, wherein the high-k material has a thickness of from 0.9 nm to about 6 nm.
10. The self-aligned high-k material semiconductor structure according to claim 1, wherein the high-k material has n effective oxide thickness of 1 nm or less.
11. The self-aligned high-k material semiconductor structure according to claim 1, wherein the interface layer comprises silicon-nitride.
Type: Application
Filed: Nov 19, 2012
Publication Date: Mar 21, 2013
Applicant: International Business Machines Corporation (Armonk, NY)
Inventor: International Business Machines Corporation (Armonk, NY)
Application Number: 13/680,470
International Classification: H01L 29/06 (20060101);