Passivation glasses

As outlined in Section 2.2.4.1, impurities and catalysts may decrease To significantly a decrease of 100°C is not unusual. The material of construction of the sample cup may act as a catalyst, resulting in surface-induced decomposition which may even be promoted by the sample/surface area ratio in the DSC cup. Therefore, it is important to check if the substance is catalyzed during the DSC experiment and if such catalysis is representative of process conditions. Frequently, substances that are sensitive to catalysis are handled in passivated glass-lined reactors, receptacles, or containers. Another phenomenon to recognize is autocatalytic decomposition. Substances that are susceptible to autocatalytic decomposition have an induction period prior to initiation of rapid decomposition. The same holds for substances that contain inhibitors, which can be depleted. 

Besides using the resists to etch copper boards, metal parts, or silicon surfaces, new applications have been disclosed. Spatial images have been holographically recorded in resists.— The resist systems of siloxanes can be converted after imaging by oxidation into passivated glass for direct formation of insulated circuits.— The resist can be filled with glass 9 or metals— and fired to form circuits directly. In one application, the resists are filled with electroless plating sensitizer for deposition of... 

Passivation glasses are used for chemical and mechanical protection of semiconductor surfaces. They are generally zinc-borosiUcate or lead-alumina—silicate... 

To avoid distortion and crack formation, the different coefficients of thermal expansion of the passivation glass and the semiconductor component must be taken into account. If the mismatch is too large, a network of cracks will originate in the glass layer during cooling or subsequent processing and destroy the hermetic protection of the semiconductor surface. There are three ways to overcome this problem ... 

A thinner passivation glass layer. Schott recommends a maximum thickness for this layer. 

Properties of Passivation Glasses The electrical insulation, including the dielectric breakdown resistance, generally depends on the alkali content, particularly the Na+ content. Typical contents are below 100 ppm for Na20 and K2O, and below 20 ppm for Li20.1 Icavy metals which are incompatible with semiconductors are controlled as well. The CuO content, for example, is below 10 ppm. 

Various types of passivation glasses are listed in Table 3.4-23. 

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