Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2003-06-27
2004-10-19
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S272000, C528S288000, C528S332000, C528S480000, C528S503000, C257S750000
Reexamination Certificate
active
06806344
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to poly-o-hydroxyamide, polybenzoxazole, and electronic component including a dielectric, all having a barrier effect against copper diffusion. In addition, the invention relates to processes for preparing poly-o-hydroxyamides, polybenzoxazoles, and electronic components.
In order to avoid an inductive disturbance of signals that is caused by capacitive coupling, conductor tracks adjacent one another in microchips are insulated from one another by a dielectric disposed between the conductor tracks. Compounds that are to be used as a dielectric must meet various requirements. Thus, the signal transit time in microchips depends both on the material of the conductor track and on the dielectric that is disposed between the conductor tracks. The lower the dielectric constant of the dielectric, the shorter, too, is the signal transit time. The silica-based dielectrics used to date have a dielectric constant of about four (4).
These materials are gradually being replaced by organic dielectrics that have a substantially lower dielectric constant. The dielectric constant of these materials is generally below three (3).
In the microchips customary at present, the conductor tracks preferably include aluminum, AlCu, or AlCuSi. With increasing integration density of the memory chips, there is a changeover to copper as conductor track material, owing to its lower electrical resistance compared to aluminum. Copper permits shorter signal transit times and hence a reduction in the conductor track cross section. In contrast to the techniques customary to date, in which the dielectric is filled in the trenches between the conductor tracks, in the copper damascene technique, the dielectric is first structured. The resulting trenches are first filled with copper and then excess copper is mechanically ground away. The dielectric must therefore be stable to the materials used for grinding and must have sufficient adhesion to the substrate in order to avoid becoming detached during the mechanical grinding process. Furthermore, the dielectrics must also have sufficient stability in the subsequent process steps in which further components of the microchips are produced. For this purpose, they must have, for example, sufficient thermal stability and must not undergo decomposition even at temperatures of more than 400° C. Moreover, the dielectrics must be stable to process chemicals, such as solvents, strippers, bases, acids or aggressive gases. Further requirements are good solubility and a sufficient shelf life of the precursors from which the dielectrics are produced.
In order to be suitable as a dielectric for microchips, it is very important that the metal of the conductor tracks does not diffuse into the dielectric even at elevated temperature. The production of microchips includes the production stages that cause a thermal load reaching 400° C. or higher, such as, for example, oxide deposition, copper annealing, or tungsten deposition from the gas phase. In order to avoid diffusion of the metal into the dielectric, a barrier is provided between dielectric and metal. Such barriers include, for example, titanium nitride, silicon nitride, silicon carbide, or tantalum nitride. The barrier acts neither as a good dielectric nor as a good conductor. However, it requires space since a certain layer thickness of the barrier is required in order effectively to suppress diffusion of the metal into the dielectric. With increasing integration density, i.e. decreasing width of the conductor tracks, the proportion of space that is occupied by the barrier increases substantially relative to the width of the conductor track. In the case of a conductor track width of 100 nm or less, the barrier may optionally occupy up to 10% of the available width. Therefore, further miniaturization of the semiconductor components is made more difficult. For further miniaturization of the microchips, the width of the barrier must therefore be further reduced or, most preferably, the barrier should be completely dispensed with.
Polybenzoxazoles (PBOs) are polymers that have very high heat resistance. The substances are already used for the production of protective and insulating layers in microchips. Polybenzoxazoles can be prepared by cyclization of poly-o-hydroxyamides. The poly-o-hydroxyamides have good solubility in organic solvents and good film formation properties. They can be applied to electronic components in a simple manner by the spin-coating technique. In a thermal treatment in which the poly-o-hydroxyamide is cyclized to give the polybenzoxazole, a polymer that has the desired properties is obtained. Polybenzoxazoles can also be processed directly in their cyclized form. In this case, however, there are as a rule difficulties with the solubility of the polymer. Building blocks for poly-o-hydroxyamides are described, for example, in DE 100 11 608, which corresponds to U.S. Pat. No. 6,531,632.
Further insulation materials stable at high temperatures are disclosed, for example, in International PCT Publication Nos. WO 97/10193, WO 91/09081, and WO 91/09087 and European Patent Nos. EP 23 662 and EP 264 678. In the case of these materials, however, a barrier must be provided between conductor track and dielectric in order to avoid diffusion of the metal into the dielectric at high temperatures.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a poly-o-hydroxyamide, a polybenzoxazole, and an electronic component including a dielectric having a barrier effect against copper diffusion, and processes for preparing poly-o-hydroxyamides, polybenzoxazoles, and electronic components that overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and that involve a polymer that is stable at high temperatures for use in microchips. The polymer permits the production of finer conductor tracks in microchips.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a poly-o-hydroxyamide of the formula I
in which:
Y
2
is
Y
1
and Y
3
, in each case independently of one another, and are selected from
Z
1
, Z
2
and Z
3
, in each case independently, are
A, if a=0 and/or d=1, is
and A, if a=1 and/or d=0, is
R
2
is —H, —CF
3
, —OH, —SH, —COOH, —N(R
5
)
2
, an alkyl group, an aryl group, a heteroaryl group, and
R
5
is an alkyl, an aryl or a heteroaryl radical;
a is 0 or 1;
b is 1-200;
c is 0-200;
d is 0 or 1;
e is 0-10;
f is 0-10;
g is 0-10;
h is 1-10;
n is 0 or 1; and
x is 0-10 if R
3
is —CH
2
—.
The poly-o-hydroxyamides of the formula I dissolve in many organic solvents, such as, for example, acetone, cyclohexanone, diethylene glycol mono- or diethyl ether, N-methylpyrrolidone, &ggr;-butyrolactone, ethyl lactate, methoxypropyl acetate, tetrahydrofuran, or ethyl acetate.
They can be applied to a substrate very readily in a uniform film by spin-coating, spraying, or dipping techniques. The evaporation of the solvent gives a homogeneous film that has a uniform layer thickness and complete fills even trenches and contact holes with a high aspect ratio. The poly-o-hydroxyamides of the formula I can be cyclized by heating to give the corresponding polybenzoxazoles; no bubble formation or cracking is observed. Even at high process temperatures of 400° C. or higher, no, or at least only very little, diffusion of metal from the conductor tracks into adjacent regions of the dielectric is observed. The barrier usually disposed between conductor track and dielectric can therefore either be made very thin or even completely dispensed with.
The repeating units characterized in the formula I by the indices b and c can, if c is >0, be randomly distributed in the polymer strand. However, it is also possible to prepare the poly-o-hydroxyamide of the formula I by block copolymerization so that segments of the polymer are composed in each case only of one of the repeating units denoted by the indices b and c. The chain length of t
Lowack Klaus
Maltenberger Anna
Sezi Recai
Walter Andreas
Greenberg Laurence A.
Locher Ralph E.
Stemer Werner H.
Truong Duc
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