Patent Application
20080241575
The increased density of modern interconnect structures, which may comprise a high surface area coupled with a low metal volume, can lead to higher concentrations of dislodged ions due to the electromigration mechanism, as is known in the art. Electromigration may occur as a function of decreased interconnect dimensions, thus, as geometries get smaller in microelectronic devices, electromigration may increase. Aluminum metal deposition can reduce electromigration in dual damascene copper lines, however, aluminum deposition is achieved on all copper line surfaces and within the bulk of the copper line when the conventional deposition techniques are used.
While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, the advantages of this invention can be more readily ascertained from the following description of the invention when read in conjunction with the accompanying drawings in which:
a-1d represent structures according to an embodiment of the present invention.
a-2d represent structures according to an embodiment of the present invention.
a-3e represent structures according to an embodiment of the present invention.
In the following detailed description, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that the various embodiments of the invention, although different, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described herein, in connection with one embodiment, may be implemented within other embodiments without departing from the spirit and scope of the invention. In addition, it is to be understood that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, appropriately interpreted, along with the full range of equivalents to which the claims are entitled. In the drawings, like numerals refer to the same or similar functionality throughout the several views.
Methods and associated structures of forming a microelectronic structure are described. Those methods may include heating a substrate comprising a patterned metallic region to about 145 C or below in a reaction space, introducing an aluminum co-reactant into the reaction space, wherein an aluminum material is formed on the patterned metallic region, but not on non-metallic regions. Embodiments of the present invention greatly improve circuit reliability of microelectronic devices so fabricate due to a reduction in electromigration and improvement in conformal coverage, symmetry, and thickness control of aluminum film formation.
a-1d illustrate an embodiment of a method of forming a microelectronic structure, such as a dual damascene copper line or copper interconnect structure, for example.
In one embodiment, the substrate 100 may further comprise at least one patterned metallic structure 102. In one embodiment, the at least one patterned metallic structure 102 may comprise at least one of copper, copper alloy, copper oxide, copper nitride, nickel, cobalt, tungsten, molybdenum, ruthenium, osmium, rhodium, iridium, palladium, platinum, gold and silver. In one embodiment, the at least one patterned metallic structure 102 may comprise an interconnect structure, such as but not limited to a copper interconnect structure. The at least one patterned interconnect structure 102 may comprise at least one barrier layer 104, such as titanium and tantalum, for example.
In one embodiment, the substrate 100 may be optionally annealed 108. In one embodiment, the anneal 108 may comprise a temperature from about 140 degrees Celsius to about 300 degrees Celsius. In one embodiment the anneal 108 may be performed in inert gas flow (like nitrogen or argon flow) at reduced pressure. In one embodiment, during the anneal 108 additional forming gas (4% H2/Ar) may be used. Annealing the substrate 100 may serve to decrease residual contamination (such as moisture) that may be introduced when the substrate is placed inside a reaction space 106 (
The use of the forming gas during the anneal 108 may serve to reduce the surface of the patterned metallic structure 102. In another embodiment, a clean process may be optionally performed on the substrate 100, wherein a plasma and/or by an effective cleaning chemical (e.g. gas) may be utilized, as are known in the art.
In one embodiment, the substrate 100 may be placed in the reaction space 106 (
The substrate 100 may be heated to a temperature of about 145 degrees Celsius or below. In some embodiments, the temperature of heating may comprise below about 135 Celsius, in others, about 118 degrees Celsius, about 100 and about 85 degrees Celsius. An aluminum co-reactant may be introduced into the reaction space 106. In one embodiment, the aluminum co-reactant may comprise at least one of Methylpyrrolidinealane (MPA), Aluminum s-butoxide, Trimethylaluminum (AlMe3 or TMA), Triethylaluminum (AlEt3 or TEA), Di-i-butylaluminum chloride, Di-i-butylaluminum hydride, Diethylaluminum chloride, Tri-i-butylaluminum, and Triethyl(tri-sec-butoxy)dialuminum.
In one embodiment, the aluminum co-reactant may comprise an organometallic aluminum-compound comprising the formula H3Al, H3Al:L or H(R)2Al:L, wherein Al is aluminum, H is hydrogen, R is an alkyl or perfluoroalkyl group having 1 to 4 carbons, and L is a Lewis base. In one embodiment R may comprise i-butyl and in one embodiment aluminum co-reactant may comprise di-(i-butyl) aluminum hydride (DIBAH). In one embodiment L may comprise 1,4-Methylpyrrolidine and in one embodiment aluminum co-reactant may comprise methylpyrrolidinealane (MPA). The Al—H bond is very reactive, which facilitates a low deposition temperature. In one embodiment, MPA, for example, can be transferred onto the substrate 100 using at least one of thermal energy, pressure difference, carrier gas and liquid dosing. Typical source temperature for MPA is about 25 degrees Celsius to about 50 degrees Celsius.
The aluminum co-reactant may react and/or decompose at the patterned metallic structure 102 surface, and in this manner may form an aluminum material 108 on the patterned metallic structure 102 (
Aluminum deposition is typically achieved on all substrate 100 surfaces when conventional CVD/MOCVD processes are used. This happens because the deposition is controlled by thermal decomposition of aluminum co-reactants, such as MPA for example, without major impact from chemical composition of the substrate surface. Utilizing a lowered temperature (below about 145 degrees Celsius) ensures that aluminum material 108 formation occurs on patterned metallic structures 102, and not on non-metallic regions 110.
In one embodiment, the required formation temperature of the aluminum material 108 is lowered by an activation effect of the patterned metallic structure 102. In one embodiment, the aluminum material may comprise a thickness of about a monolayer to about 30 nm. In one embodiment for example, the metallic material of the patterned metallic structure 102, such as but not limited to copper, may diffuse continuously onto the surface of patterned metallic structure 102 to activate it or, in other embodiments, a fresh aluminum material 108 surface itself may decrease the temperature that is needed for deposition.
The lowered temperature of formation of the aluminum material 108 may result in the metallic material of the patterned metallic structure 102 primarily remaining continuous i.e., it is not harmed by temperature effects, for example, material agglomeration etc. Additionally, since the aluminum material 108 is selectively grown on the patterned metallic structure 102, there is no need for aluminum material 108 patterning, thus eliminating processing steps.
In one embodiment, composition of the aluminum material 108 can be tuned by varying the concentrations of the aluminum co-reactant and the patterned metallic structure 102. Thus, by tuning the stoichiometry of the aluminum material 108, it may form various alloys 112 (
a-2d depict selective deposition of aluminum material on a patterned metallic substrate after lithographic patterning of an ILD layer prior to subsequent metal layer formation.
The substrate 200 may be placed in a reaction space 206 and an aluminum material 208 may be formed on a top surface 218 of the at least one patterned metallic structure 202 (
The aluminum material 208 may be disposed between the top surface 218 of the patterned metallic structure 202 and a bottom surface 221 of the patterned metallic structure 202a, but will not be disposed on the sidewall portion of the patterned metallic structure 202a, since the aluminum material 208 only reacts with the exposed metallic portion of the patterned metallic structure 202, and not the ILD 210 sidewall 216, which is a non-metallic material.
In another embodiment, a transistor structure 300 may comprise a patterned metallic structure 302 (similar to the patterned metallic structures 102, 202), that may comprise a portion of a gate structure 303, in some embodiments (
The transistor structure 300 may further comprise an ILD region 310. An aluminum material 308 may be formed on the patterned metallic structure 302 of the gate structure 303, and not substantially on the ILD region 310, according to embodiments of the present invention (
The gate contact opening 313 and the source/drain contact opening 315 may be subsequently filled with a conductive material (not shown), to form a conductive gate contact structure and a conductive source/drain contact structure. The aluminum oxide cap 309 may serve as an etch stop layer during processing of the gate contact structure and/or the source drain contact structure. The aluminum oxide cap 309 may be hermetic toward oxygen diffusion, thus protecting the underlying gate materials from oxidation in downstream processing. The aluminum oxide cap 309 may further serve as a dielectric material to mitigate any shorting of the gate contact with the source/drain contact, as may be encountered in case of marginal registration during lithographic patterning.
Benefits of the embodiments of the present invention enable selective deposition of metallic films or bulk materials via CVD or ALD thus yielding conformal coverage of such films. For example, thin copper and copper-aluminum alloy films may be formed selectively, thus eliminating process steps such as patterning of the aluminum films. Embodiments of the present invention enable Increased circuit reliability due to a reduction in electromigration effects, and improved conformal coverage, symmetry, and thickness control.
Although the foregoing description has specified certain steps and materials that may be used in the method of the present invention, those skilled in the art will appreciate that many modifications and substitutions may be made. Accordingly, it is intended that all such modifications, alterations, substitutions and additions be considered to fall within the spirit and scope of the invention as defined by the appended claims. In addition, it is appreciated that certain aspects of microelectronic structures are well known in the art. Therefore, it is appreciated that the Figures provided herein illustrate only portions of an exemplary microelectronic structures that pertains to the practice of the present invention. Thus the present invention is not limited to the structures described herein.
