The invention relates to novel bis-o-aminophenols and o-aminophenolcarboxylic acids and to a method for their preparation.
Bis-o-aminophenols and o-aminophenolcarboxylic acids are needed in particular for the preparation of high-temperature-stable polymers such as polybenzoxazoles (PBO) and intermediates for their preparation, and for the preparation of hydroxypolyimides (see, for example, European Patent EP 0 264 678 and European Patent EP 0 300 326). PBO intermediates can be prepared in a way such that a dicarboxylic acid chloride is reacted with a bis-o-aminophenol. Whereas, however, numerous dicarboxylic acids and their acid chlorides are available as a result of the diversity of their industrial uses, there are comparatively few bis-o-aminophenols. Moreover, the kind of aminophenol used exerts a considerable influence on the spectrum of properties of the polymer prepared from it. Thus not only the thermal, electrical and mechanical behavior, but also the solubility, stability towards hydrolysis and many other characteristics of the polymer are strongly influenced by the aminophenol used in the preparation.
PBO intermediates can be structured directly at reasonable cost in the form of a photosensitive compound, i.e. without an auxiliary resist. In comparison with other directly photostructurable dielectrics such as polyimide (PI) and benzocyclobutene (BCB), PBO intermediates have the advantage of positive structurability and aqueous alkaline development (see European Patent EP 0 023 662 and European Patent EP 0 264 678). For this purpose the PBO intermediates used must be largely transparent at the exposure wavelength and sufficiently soluble inxe2x80x94preferably metal ion-freexe2x80x94developers. As is the case for the polyimides, polybenzoxazoles also have the great advantage thatxe2x80x94in comparison with the cyclized final productsxe2x80x94they can be applied to the substrate as readily soluble intermediates and then cyclized on the substrate itself, whereby the solubility and therefore the sensitivity towards solvents and other process chemicals strongly decreases.
Good electrical, mechanical and thermal characteristics are necessary for the use of polybenzoxazoles in microelectronics, in particular as a dielectric between two metal layers, e.g. in multi-chip modules and memory and logic chips, or as a buffer coat between the chip and its outline. When using polymers of the above kind as a dielectric between metallic printed conductors it is very important that the metal not diffuse through the dielectric at high temperature, i.e. at temperatures greater than 300xc2x0 C. But many metals, especially aluminum, which is currently the most commonly used metal, do diffuse through the dielectric at high temperatures. For this reason the metal is coated with a barrier layer, for example of titanium nitride or a combination of titanium and titanium nitride, which prevents the diffusion of the metal into the dielectric. The use of an additional layer, however, adds significantly to the costs and also requires more time.
Up to now there has been a lack of suitable bis-o-aminophenols and o-aminophenolcarboxylic acids for the preparation of polymers able to meet the strongly increased requirements of the microelectronics sector. Comparable monomers are known, for example, from European Patent Application EP 0 110 420, European Patent Application EP 0 317 942, European Patent Application EP 0 905 123 and European Patent Application EP 0 906 903. But there is no information on the diffusion of metals in the polymers prepared from these after cylization on a substrate (see: European Patent EP 0 264 678 and European Patent Application EP 0 317 942).
It is accordingly an object of the invention to provide bis-o-aminophenols and o-aminophenolcarboxylic acids and a method for preparing the same, which overcome the hereinafore-mentioned disadvantages of the heretofore-known compounds and methods of this general type and which are suitable for the preparation of polymers that meet the strongly increased requirements of microelectronics. In particular, these monomers are intended to enable the preparation of readily soluble polymer intermediates which after cyclization on a substrate produce polybenzoxazoles with high temperature stability and, above all, with significantly reduced metal diffusion.
With the foregoing and other objects in view there is provided, in accordance with the invention, bis-o-aminophenols and o-aminophenolcarboxylic acids having structures represented by the respective formulas: 
wherein
each of A1 to A7 is a univalent ring substituent independently selected from the group consisting of H, F, CH3, CF3, OCH3 and OCF3;
T is a bivalent polycyclic linking member selected from the group consisting of 
wherein independently at each occurrence Q is selected from the group consisting of Cxe2x80x94H, Cxe2x80x94F, Cxe2x80x94CH3, Cxe2x80x94CF3, Cxe2x80x94OCH3, Cxe2x80x94OCF3 or N, provided that at least one Q signifies N and a maximum of two N atoms may be present in a single ring, 
wherein each of A8 to A21 is a univalent ring substituent independently selected from the group consisting of H, F, CH3, CF3, OCH3 and OCF3; 
wherein X signifies CH2, CF2, C(CH3)2, C(CF3)2, C(OCH3)2, C(OCF3)2, C(CH3) (C6H5), C(C6H5)2, O, Nxe2x80x94H, Nxe2x80x94CH3 or Nxe2x80x94C6H5; 
xe2x80x83wherein
independently at each occurrence Qxe2x80x2 is selected from the group consisting of Cxe2x80x94H, Cxe2x80x94F, Cxe2x80x94CH3, Cxe2x80x94CF3, Cxe2x80x94OCH3, Cxe2x80x94OCF3 or N,
and M is a bivalent linking member selected from the group consisting of 
wherein Q and Qxe2x80x2 are as defined above.
The designations xe2x80x9cA1-A3xe2x80x9d, xe2x80x9cA4-A7xe2x80x9d, xe2x80x9cA8-A10xe2x80x9d, xe2x80x9cA11-A14xe2x80x9d, xe2x80x9cA15-A17xe2x80x9d and xe2x80x9cA18-A21xe2x80x9d in the structural formulae mean that the phenyl groups or cyclic structures carry respectively the residues A1, A2 and A3, or A4, A5, A6 and A7, or A8, A9 and A10, or A11, A12, A13 and A14, or A15, A16 and A17, or A18, A19, A20 and A21.
With the objects of zhe invention in view, there are also provided novel o-nitrophenyl ether compounds from which the bis(o-aminophenols) and o-aminophenolcarboxylic acids of the invention can be prepared by a sequence of reactions as detailed below. The o-nitrophenyl ether compounds of the invention are represented by the formula 
wherein A1-A3 and T are defined as above, R is a residue selected from the group consisting of alkyl, alkoxyalkyl, alkenyl, alkoxyalkenyl, alkynyl and alkoxyalkynyl residues with a maximum of 6 C atoms in each case, and phenyl, phenacyl C6H5COxe2x80x94CH2xe2x80x94, benzyl, benzylalkyl, benzylalkenyl, benzyloxyalkyl, benzyloxyalkenyl, benzylalkoxyalkyl and benzylalkoxyalkenyl residues with a maximum of 4 aliphatic C atoms in each, case, and Y is selected from the group consisting of 
and H.
The bis(o-aminophenols) and o-aminophenolcarboxylic acids of the invention are advantageously prepared by a simple synthesis utilizing novel o-nitrophenyl ether compounds of the invention as starting materials, that can be carried out with high reproducibility. Compared to known bis-o-aminophenols and o-aminophenolcarboxylic acids having different T groups, the reactivity of the compounds of the invention with a carboxylic acid derivative such as an acid chloride is unexpectedly modulated so as to increase the selectivity of reaction at the amino group and thus favoring the conversion of the compounds of the invention to polymer intermediates in high yield and purity.
In these novel compounds, the special structure is clearly responsible for the unexpectedly good barrier effect which the polymer intermediates prepared from them exert against metal diffusion. Dielectrics prepared from these kinds of polybenzoxazole intermediates show in particular a significant reduction in aluminum diffusion. This removes the need for an additional barrier layer.
With the objects of the invention in view, there is also provided a process for preparing the respective bis(o-aminophenols) and o-aminophenolcarboxylic acids.
The method used to prepare the bis-o-aminophenols and o-aminophenolcarboxylic acids begins with the reaction of a dihydroxy compound represented by the formula
HOxe2x80x94Txe2x80x94OH,
T being defined as above, with a halogenated o-nitrophenol ether derivative represented by the formula (2) 
in which Z is a halogen atom, preferably fluorine, and R and A1-A3 are defined above.
The reaction takes place in a solvent at a temperature of 50 to 150xc2x0 C. in the resence of a base.
In the preparation of bis-o-aminophenols the reactants HOxe2x80x94Txe2x80x94OH (1) and (2) are used in the molar ratio of approximately 1:2, whereby the reaction proceeds in the following way: 
In the preparation of o-aminophenolcarboxylic acids the reactants (1) and (2) are used in an approximately equimolar ratio whereby the reaction proceeds as follows: 
The novel reaction product (4) is then treated with a halogenated benzoic acid ester (5) in a solvent at a temperature of 50 to 150xc2x0 C. in the presence of a base. The following reaction takes place: 
The novel nitrophenyl ether reaction products (3) and (6) are then subjected to reduction and cleavage and reaction product (6) is also subjected to hydrolysis. The following reactions take place with the formation of the bis-o-aminophenols (7) and o-aminophenolcarboxylic acids (8) according to the invention: 
The reduction of the nitro compounds (3) and (6) can, for example, be carried out by hydrogenation with hydrogen on palladium/active charcoal (Pd/C). In principle, however, any method which can be used for reducing a nitro group to an amino group is suitable.
Removal of the R group in the compounds (3) and (6) can be carried out using, for example, trifluoroacetic acid or titanium tetrachloride. The hydrolysis of the ester group in the compounds (6) can be carried out using, for example, potassium hydroxide.
Reduction and cleavage, or reduction, cleavage and hydrolysis can be performed in separate steps; these steps can be carried out in any order. It is advantageous, however, to perform these reactions, i.e. reduction and cleavage, or reduction, cleavage and hydrolysis, simultaneously, i.e. together. This is preferably performed through hydrogenation with hydrogen on Pd/C.
The base is preferably a carbonate or bicarbonate of an alkali metal or alkaline earth metal, such as sodium carbonate (Na2CO3) or potassium carbonate (K2CO3). It can also be advantageous to use an organic base with a tertiary nitrogen atom, for example triethylamine, tetramethylethylenediamine, N-ethylmorpholine, quinoline or pyridine.
The polymer intermediates prepared from the bis-o-aminophenols and o-aminophenolcarboxylic acids according to the invention are readily soluble in many organic solvents such as acetone, ethyl lactate, N-methylpyrrolidone, diethylene glycol mono- or diethyl ether, cyclohexanone and xcex3-butyrolactone, and also in aqueous alkaline developers containing no metal ions. They are therefore well suited as base polymers for positive photostructurable dielectrics which can be developed with aqueous alkali. Using the centrifugal technique the intermediates can be easily applied to the substrate, such as a silicon wafer; they form even films and can be readily cyclized on the substrate. A particular advantage of the intermediates prepared from bis-o-aminophenols and o-aminophenolcarboxylic acids in comparison with intermediates of prior art is significantly reduced metal diffusion.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in novel bis(o-aminophenols), o-aminophenolcarboxylic acids and o-nitrophenyl ether compounds and a process for preparing the same, it is nevertheless not intended to be limited to the details given, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
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