Method of forming dielectric material suitable for...

Details Method of forming dielectric material suitable for... Method of forming dielectric material suitable for...

1999-11-01

2001-08-28

Talbot, Brian K. (Department: 1762)

Coating processes

With post-treatment of coating or coating material

Heating or drying

C427S096400, C427S372200, C427S385500, C438S409000, C438S781000, C438S960000, C264S041000

Reexamination Certificate

active

06280794

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to a dielectric material. More particularly, the present invention relates to a low dielectric constant material suitable as an insulating layer in a microelectronic integrated circuit.
BACKGROUND OF THE INVENTION
Integrated circuits often include devices formed within a semiconductor substrate and multiple levels of interconnect layers, which include conductive features separated by dielectric material. Over the years, the performance of microelectronic integrated circuits, with respect to speed and power consumption, has been improved by reducing the size of the integrated circuit, especially devices formed within the semiconductor substrate.
As the spacing between interconnect conductive features within the integrated circuit continuously decreases, the integrated circuit becomes increasingly susceptible to capacitance coupling between two or more conductive features. In particular, the integrated circuit becomes increasingly susceptible to crosstalk due to increased capacitive coupling between the conductive features and to signal propagation caused by interconnect resistailnce and capacitance (“RC delays”).
The capacitance between two or more interconnect conductive features is proportional to the dielectric constant, k, of material separating the features and inversely proportional to the distance between the conductive features. Thus, adverse affects of reduced spacing between interconnect conductive features may be mitigated by interposing material having a low dielectric constant (low-&kgr; material) between the conductive features.
Typical dielectric material used in the manufacture of integrated circuits such as silicon oxide (SiO
x
) has a dielectric constant of about 4. However, recently, new materials having a lower dielectric constant (e.g., dielectric constants less than about 2.5) have been formed of porous silica. Generally, these porous silica films are formed by encapsulating a sacrificial material such as a polynorbornene within a silica matrix and heating the silica and sacrificial material to decompose the sacrificial material. Upon decomposition, the sacrificial material evaporates and permeates from the silica lattice, leaving air-filled voids within the lattice.
Generally, the dielectric constant of a two-phase film varies in accordance with the equation presented below:
ln(k
c
)=v
1
ln(k
1
)+v
2
ln(k
2
)
where k
1
, k
2
, and k
c
are the dielectric constant of phase
1
, phase
2
, and the two phase material, respectively, and v
1
and v
2
are the volume fraction of phase
1
and phase
2
in the material. Compared to dielectric film such as silica, air has a relatively low dielectric constant of 1. Thus, a dielectric constant of a two-phase material including air and silica may be reduced by incorporating more air into the two-phase material. However, as; more air is introduced into the material, the silica-based dielectric film tends to weaken and may be susceptible to damage during circuit use or subsequent circuit manufacturing processes such as chemical mechanical polishing. Accordingly, improved dielectric films having a low dielectric constant, which are suitable for microelectronic applications, are desirable.
SUMMARY OF THE INVENTION
The present invention provides an improved dielectric material and a method for forming the material. More particularly, the present invention provides a low dielectric constant material suitable as dielectric material in microelectronic integrated circuit manufacturing.
The way in which the present invention addresses the drawbacks of the now-known dielectric materials and methods of forming the materials is discussed in greater detail below. However, in general, the invention provides a porous polymer-based dielectric material that can be integrated into microelectronic interconnect manufacturing processes.
In accordance with an exemplary embodiment of the present invention, a dielectric compound is formed by dispersing a first material in a second material. In accordance with one aspect of this embodiment, the decomposition temperature of the first material is less than the glass transition temperature of the second material.
In accordance with another exemplary embodiment of the present invention, a dielectric material is formed by preparing polymer precursor solution A, dissolving a sacrificial organic material in a solvent to form a solution B, and mixing solution A with solution B to form an A-B mixture. The A-B mixture is exposed to heat to cause the solvent(s) to evaporate and to cause the polymer material to crosslink to form a solid material. The solid material is then further heated past the decomposition temperature of the sacrificial organic material to allow the organic material to evaporate. In accordance with an exemplary aspect of this embodiment of the present invention, the solid material is further heated to a temperature near or above the glass transition temperature of the polymer to form pores within the polymer. In accordance with one aspect of this embodiment, the A-B mixture solution is applied to a surface of a semiconductor wafer. In accordance with a further aspect of this embodiment, the solution is applied using spin-on or dipping techniques.
In accordance with a further exemplary embodiment of the present invention, the dielectric constant of the solid material is relatively low. Thus a relatively small pore volume is required to produce the low-&kgr; material of the present invention. Because relatively few pores are formed within the solid material, the solid material is relatively sturdy and is suitable for subsequent water processing.
In accordance with a further exemplary embodiment of the present invention, the solid material is exposed to an oxygen containing environment during the sacrificial material decomposition process to assist liberation of the sacrificial material.


REFERENCES:
patent: 5103288 (1992-04-01), Sakamoto et al.
patent: 5668398 (1997-09-01), Havemann et al.
patent: 92804 (1998-04-01), None
“Low k, Porous Methyl Silsesquioxane and Spin-On0Glass”, Abbe T. Kohl, Richard Mimna, Robert Shick, Larry Rhodes, Z.L. Wang, and Paul A. Kohl, Electrochemical and Solid-State Letters, 2(2) 77-79 (1999), No month available.
Polyimide Nanofoams for Low Dielectric Applications, K.R. Carter et al. Mat. Res. Soc. Symp. Proc. vol. 381 pp. 79-91, 1995, No month available.
“Recent Advances in Low K Polymeric Materials”, K.R. Carter, Mat. Res. Soc. Symp. Proc. vol. 476, pp. 87-97 (1997), No month available.
Dielectric Property and Microstructure of a Porous Polymer Material with Ultralow Dielectric Constant; Yuhuan Xu, et al. American Institute of Physics 1999, No month available.
Templating Nanopores Into Poly (Methylsilsequioxane): New Low-Dielectric Coating Suitable for Microelectronic Applications; Julius F. Remenar et al; Mat. Res. Soc. Symp. Proc. vol. 511 p. 69-75 (1998), No month available.
Damascene Integration of Copper and Ultra-Low-k Xerogel for High Performance Interconnects, E.M. Zielinski et al., No date available.

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