Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-04-16
2001-09-04
Whitehead, Jr., Carl (Department: 2822)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S003000, C438S240000, C438S396000, C438S680000, C438S685000, C438S686000
Reexamination Certificate
active
06284654
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a chemical vapor deposition (CVD) process for the fabrication of hybrid electrodes in microelectronic device structures such as ferroelectric random access memory (FeRAM) device structures.
2. Description of the Related Art
Ferroelectric random access memories (FeRAMs) depend on the use of high integrity ferroelectric materials as a critical component of cell architecture. Although a wide variety of ferroelectric materials have been developed having actual demonstrated and potential utility in device applications, the practical utilization of such materials in device architectures requires that such materials can be readily fabricated in an efficient and cost-effective manner with respect to their integration in conformations including barrier regions, isolation structures, interconnects, vias and electrodes.
The electrical properties of ferroelectric materials in many instances are highly influenced by the materials used to fabricate electrodes for the ferroelectric material structures. For example, ferroelectric materials such as Pb(Zr,Ti)O
3
(PZT) show a strong dependence on the type of electrode used as the contact for the device structure.
Noble metals such as platinum that have a high work function may be used to fabricate electrodes that produce device structures with low electrical leakage characteristics, but the rate of loss of remanent polarization in the structure with repeated switching cycles (ferroelectric fatigue) is unacceptably high.
Conversely, conductive oxide electrodes improve fatigue behavior, but usually at the cost of unacceptably large increase in electrical leakage. Kingon, et. al., (U.S. Pat. No. 5,555,486) and Al-Shareef, et. al. (J. Appl. Phys. 77 (5), Mar. 1, 1995: 2146), the disclosures of which are hereby incorporated herein by reference in their entirety, have demonstrated a hybrid electrode, comprised of dual layers of Pt and conductive oxide, either with the Pt layers on the exterior or the conductive oxide layers on the exterior, and the other electrode material on the interior against the ferroelectric material. When used with such hybrid electrodes, PZT displays both good fatigue endurance and low electrical leakage.
The layered structures of the above-described art represent one approach to achieving the benefits of conductive oxides and Pt electrodes.
An alternative approach utilizes alloyed electrodes, also demonstrated by Kingon, et. al., (U.S. Pat. No. 5,555,486) and Al-Shareef, et. al. (J. Appl. Phys. 77 (5), Mar. 1, 1995: 2146). Alloyed electrodes of Pt and RuO
2
are formed by co-deposition of metals using ion-beam sputtering. In the preferred embodiment the noble metal is alloyed with an element that is relatively immiscible, and that has a tendency to oxidize to an electrically conductive oxide. Examples of such a combination include Pt and Ir where Ir can be oxidized to IrO
2.
Other examples of alloy systems with a high degree of immiscibility include Pd—Ir, Rh—Ir and Pd—Ru. In the latter example, Ru oxidizes to RuO
2.
Still further examples include mixtures of noble metals (e.g., Pt, Pd, Rh) and complex conductive oxides (LaSrCoO
3
, SrRuO
3
, indium tin oxide, and yttrium barium copper oxide). The bi-phasic microstructure consists ideally of noble metal and oxidizable metal grains uniformly distributed. The oxidizable phase may be oxidized during the co-deposition process as taught by Kingon, et. al., and Al-Shareef, et. al., by a separate anneal in an oxidizing ambient (e.g., O2, N
2
O, ozone) before deposition of the ferroelectric, or alternatively, during the deposition process for the ferroelectric which is usually carried out in an oxidizing ambient.
As device density increases, a need arises for conformal coatings to cover sidewalls and to fill small features with electrodes. Wet methods of deposition are have poor conformality, as do line of sight processes such as evaporation. Sputter deposition offers a higher degree of conformality, but composition control of complex oxides is difficult.
Accordingly, there is a need in the art for improved electrode fabrication techniques to maximize the benefits achievable with composite electrode structures.
SUMMARY OF THE INVENTION
The present invention relates to a method of fabricating a hybrid electrode structure for a ferroelectric device structure including a ferroelectric material, comprising the steps of:
vaporizing a first organometallic precursor for a first electrode metal component to form a first electrode component precursor vapor,
vaporizing a second organometallic precursor for a second electrode metal component to form a second electrode component precursor vapor; and
depositing the first electrode component precursor vapor and the second electrode component precursor vapor by chemical vapor deposition for formation of said hybrid electrode structure, in a deposition mode selected from the group consisting of:
(I) simultaneous chemical vapor deposition of the first electrode metal component from the first electrode component precursor vapor and the second electrode metal component from the second electrode component precursor vapor, to yield an alloy hybrid electrode structure; and
(II) sequential chemical vapor deposition of the first electrode metal component from the first electrode component precursor vapor and the second electrode metal component from the second electrode component precursor vapor, to yield a layered hybrid electrode structure including a first layer containing the first electrode metal component and a second layer containing the second electrode metal component.
The ferroelectric material utilized in the broad practice of the invention may comprise any suitable ferroelectric material, such as for example Pb(Zr,Ti)O
3
, (Pb,La)TiO
3
, (Pb,La)(Zr,Ti)O
3
, (Pb,Sr)(Zr,Ti)O
3
and SrBi
2
(Ta,Nb)
2
O
9
.
In one aspect of the method of the invention, the first organometallic and second organometallic precursors are different from one another and are selected from the group consisting of:
Platinum precursors trimethyl(cyclopentadienyl) Pt (IV), trimethyl(&bgr;-diketonate) Pt (IV), bis(&bgr;-diketonate) Pt (II), tetrakis(trfluorophosphine) Pt (0);
Cobalt: &bgr;-diketonates, cyclopentadienyl compounds, &bgr;-ketoiminates and &bgr;-diiminates of Co (II);
Iridium precursors: a Lewis base-stabilized &bgr;-diketonate iridium composition or a Lewis base-stabilized &bgr;-ketoiminate composition, of the formulae:
Lewis base stabilized Ir(I) &bgr;-diketonates of formula I:
where in R and R′ are the same or different and may be H, aryl, pertfluoroaryl, C
1
-C
6
alkyl, or C
1
-C
6
perfluoroalkyl, and L is a coordinating Lewis base, preferably alkene, diene, cycloalkene, cyclodiene, cyclooctatetraene, alkyne, substituted alkyne (symmetrical or asymmetrical), amine, diamine, triamine, tetraamine, ether, diglyme, triglyme, tetraglyme, phosphine, carbonyl, dialkyl sulfide, vinyltrimethylsilane, and allyltrimethylsilane, or
Lewis base stabilized Ir(I) &bgr;-ketoiminates of formula II:
wherein R, R′, and R″ are the same or different, and are independently selected from the group consisting of H, aryl, perfluoroaryl, C
1
-C
6
alkyl, or C
1
-C
6
perfluoroalkyl, and L is a coordinating Lewis base, preferably selected from the group consisting of alkene, diene, cycloalkene, cyclodiene, cyclooctatetraene, alkyne, substituted alkyne (symmetrical or asymmetrical), amine, diamine, triamine, tetraamine, ether, diglyme, triglyme, tetraglyme, phosphine, carbonyl, dialkyl sulfide, vinyltrimethylsilane, and allyltrimethylsilane;
Ruthenium precursors bis(cyclopentadienyl) Ru and tris(tetramethyl-3,5-heptanedionate) Ru;
Lanthanum: &bgr;-diketonates, cyclopentadienyl compounds, &bgr;-ketoiminates and &bgr;-diiminates of La(III);
Strontium: &bgr;-diketonates, cyclopentadienyl compounds, &bgr;-ketoiminates and &bgr;-diiminates of Sr (II); and
Cobalt: &bgr;-diketonates, cyclopentadienyl compounds, &bgr;-ketoiminates and &bgr;-diiminates of Co (II);
Rhodium: Rhodium(I) &
Baum Thomas H.
Roeder Jeffrey F.
Van Buskirk Peter C.
Advanced Technology & Materials Inc.
Guerrero Maria
Hultquist Steven J.
Jr. Carl Whitehead
Zitzmann Oliver A. M.
LandOfFree
Chemical vapor deposition process for fabrication of hybrid... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Chemical vapor deposition process for fabrication of hybrid..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Chemical vapor deposition process for fabrication of hybrid... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2524803