Low dielectric constant materials prepared from photon or...

Details Low dielectric constant materials prepared from photon or... Low dielectric constant materials prepared from photon or...

1999-12-20

2003-12-16

Nakarani, D. S. (Department: 1773)

Stock material or miscellaneous articles

Composite

Of silicon containing

C427S489000, C427S515000, C428S450000

Reexamination Certificate

active

06663973

ABSTRACT:

FIELD OF THE INVENTION
This invention is related to chemical compositions and methods for preparing materials that have low dielectric constants LKD. These low K materials, LKD, are prepared by photon assisted and/or plasma enhanced transport polymerization or chemical vapor deposition of some selected siloxanes and F-containing aromatic compounds. The LKD materials are particularly useful for manufacturing integrated circuits that have features smaller than 0.18 &mgr;m.
BACKGROUND OF THE INVENTION
For the past 20 years, the integrated circuit (IC) device density has doubled in about every 18 months. When the gate length of integrated circuits is less than 0.18 &mgr;m, the propagation time or delay time is dominated by interconnect delay instead of device gate delay. As the distance between metal lines decreases, the need for materials which can protect the integrity of the circuits also increases.
Aluminum and copper are the metal of choice for manufacture of integrated circuits with feature sizes of less than 0.18 &mgr;m. Furthermore, as methods for etching copper are developed, integrated circuits with feature sizes of less than 0.13 &mgr;m can be made using copper damascene along with LKD materials.
1. Packaging of Integrated Circuits
When aluminum or copper is used in integrated circuits, titanium nitride (TiN) is used as barrier layer to improve interfacial adhesion between metal and SiO
2
dielectric materials and to prevent corrosion of the metal by the wet chemicals used during semiconductor processing or from fluorine liberated from fluorinated SiO
2
or other fluorinated polymers in the low dielectric polymer films. Corrosion results in the migration of metal ions from the metal line into the surrounding dielectric material. This results in increased leakage of current from the metal line into the adjacent circuit components, degrading circuit performance. Thus, one purpose of the glue layer or barrier layer is to prevent migration of metal ions from the metal lines. If TiN is used as a barrier layer, it must be about 200 Å to about 300 Å in thickness to be effective to protect against metal corrosion and degradation of circuit performance. Because metal lines are close together, the distance between them is limited by the thickness of the barrier layer (2×200 Å=400 Å) and by the intervening low dielectric material. In an integrated circuit with 0.13 &mgr;m feature size, the thickness of the barrier layer of 400 Å leaves only 900 Å of space available for the low dielectric material. Moreover, as the space available for dielectric material decreases, there is the increased likelihood of gaps or voids being formed in the dielectric layers, further degrading circuit performance. Therefore, currently there is a need for new ways of protecting metal lines from corrosion while still maintaining proper dielectric efficiency.
Moreover, when the metal gap is equal to or smaller than 0.13 &mgr;m and when copper is used as conductor, the dielectric effectiveness of currently available materials is so limited that TiN or any other currently available metal barrier will become unsuitable for protecting against metal corrosion. Furthermore, the potential interfacial corrosion problem for copper will be even more severe than for aluminum.
To address this problem and others, new adhesion layer and barrier layer materials with low dielectric constants are being developed. Organic polymers are considered an improvement over inorganic low dielectric materials because the K of organic polymers can be as low as 2.0. However, most of the currently available organic polymers have serious problems. Specifically, they are not sufficiently effective as barrier layers.
A. Siloxane Containing Polymers for Packaging Integrated Circuits
In the 1980s, very extensive studies have been conducted to find hermetic packaging technologies for copper that used in Multi-Chip Modules (MCM). Due to their excellent electrical and thermal properties, polysiloxanes are among the most prevalent materials currently used in the encapsulation of electronic components. It has been found that only silicone gels and some siloxane containing polymers can prevent increases of leakage currents for encapsulated Triple Track Testers (TTT) under pressure cooker conditions. C. P. Wong, “High Performance Silicone Gels in IC Device Chip Encapsulation,”
Mat. Res. Symp.
108:175-187 (1988). However, most of the conventional polysiloxanes have either gel-like or rubbery in consistency, and therefore have limited applications in areas demanding high mechanical strength of the coating material.
The mechanisms for superior insulation property of siloxane-containing polymers are remained to be fully elucidated. It was rationalized though siloxanes are permeable to water vapor, they are perfect barriers for liquid water due to their high hydrophobicity. Their near zero water absorption can be attributed to the presence of siloxane derivatives presented in these polymers:
where R′, R″, R″′, and R″″ are alkyl groups, such as —CH
3
, and wherein n is an integer of from 1 to 5. Due to very high rotational and oscillatory freedom of the substituted siloxanes including R groups such as —CH
3
, these siloxane groups can achieve very close contact with metal. The close contact prevents water from coming between the polymer and metal components thereby providing a watertight seal to prevent the degradation of critical circuit components by water. These siloxanes therefore are suitable for barrier layer materials.
B. Spin On Glass (SOG)
Currently, spin-on-glass (SOG) processes uses both organic and inorganic compounds as precursors. Organic precursors include siloxanes which contain many Si—CH
3
groups and inorganic siloxane precursors contain few Si—H groups. These precursors, produce polymer produce thin films having dielectric constants in the range of from about 2.7 to 3.0. However, a crack-free SOG dry film is only attainable when its thickness is less than 0.25 to 0.3 &mgr;m. Therefore, it is necessary to perform several sequential SOG steps to manufacture a layer of SOG that is thick enough (about 1 &mgr;m) to provide desirable sealing and dielectric properties. The total time needed to make SOG layers of this thickness is about 3 to 4 hours. This makes manufacturing SOG siloxane seals very inefficient. Furthermore, the SOG process is expensive due to the high losses (about 80% to 90%) of materials during spin coating.
These SOG deposited precursors also require post-deposition treatments at temperatures higher than 410° C. to reduce out gassing during deposition, reflow or annealing of metals. This high temperature treatment results in high residual stress, which ranges from about 200 to about 500 MPa at room temperature. High residual stress can cause delamination at dielectric materials and metal surfaces, and can crack metal features in integrated circuits. Therefore, chemical processes that can deposit other siloxane-containing polymers are desirable.
II. Precursors and Polymers for Manufacturing Low Dielectric Constant Materials
During the past few years, several types of precursors have been used to manufacture polymers with low dielectric constants for use in manufacture of integrated circuits. Transport Polymerization (TP) and Chemical Vapor Deposition (CVD) methods have been used to deposit low dielectric materials. The starting materials, precursors and end products fall into three groups, based on their chemical compositions. The following examples of these types of precursors and products are taken from Proceedings of the
Third International Dielectrics for Ultra Large Scale Integration Multilevel Interconnect Conference
(DUMIC), Feb. 10-11 (1997).
A. Modification of SiO
2
by Carbon (C) and Fluorine (F)
The first method described is the modification of SiO
2
by adding carbon and/or fluorine atoms. McClatchie et al.,
Proc.
3
d Int. DUMIC Conference,
34-40 (1997) used methyl silane (CH
3
—SiH
3
) as a carbon source, and when react

Affiliated with

Also associated with

Rating

Low dielectric constant materials prepared from photon or... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Low dielectric constant materials prepared from photon or..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low dielectric constant materials prepared from photon or... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3099031