In microelectronics, highly heat-resistant polymers are required as protective and insulating coats. These polymers can be used as a dielectric between chip and metalization or between two metal planes of the chip, e.g. in multichip modules, memory chips and logic chips. The metal planes may be present below or above the inorganic passivation of the chip. Moreover, such polymers can also be used as a buffer coating between the chip and its housing. Among these polymers, the polyhydroxyamides have good solubility in organic solvents and good film formation properties and can be applied to the electronic components by means of the economical spin-coating technique. These polyhydroxyamides are cyclized after a thermal treatment (curing) to give polybenzoxazoles and, according to the following equation, thus acquire their final properties:

The requirements with respect to the end product are, for example, good insulation properties and sufficient thermal stability. Good adhesion of the material to all relevant substrates, for example silica, silicon nitride, titanium, titanium nitride, tantalum or tantalum nitride, is also particularly important. Titanium, titanium nitride, tantalum and tantalum nitride are proven adhesion-promoting and barrier coats for aluminum or copper metalizations.
If the polymer is used as an insulating coat, for example below the uppermost coat of metal, i.e. the outer wiring, further properties are important. These are in particular the adhesion of the metallic conductors or of the corresponding adhesion-promoting and barrier coats to the insulating coat and high resilience or extensibility of this insulating coat so that the different expansions of the chip and of the circuit board are compensated. FIG. 1 shows a flip-chip contact, wherein the upper part of the chip points toward the circuit board. The abovementioned properties are, however, also important in other metalization coats of the chip.
Polyhydroxyamides which are readily soluble and have good thermal stability are described, for example, in EP 0 317 942 A2, DE 3 718 212 A1 or U.S. Pat. No. 5,077,378. However, the materials described in these publications have very low resilience or elongation and only moderate adhesion, in particular to titanium nitride or tantalum nitride.
Chemical Abstracts Vol. 83, 1975, report 81475x describes coating materials for cables, but these are not polyhydroxyamides.
Patent Abstracts of Japan C-991, Oct. 2, 1992, Vol. 16/No. 473 describes fluorinated aromatic polyhydroxyamides and polybenzoxazoles having high thermal stability. Particular adhesion properties of these compounds are not mentioned.
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