Positive photoresists commercially available

PhenylT4(OH)4 is cis-( 1,3,5,7-tetrahydroxy)- ,3,5,7-tetraphenylcyclotetrasiloxane. OFPR-800 is a commercially available positive photoresist. 

We previously reported that iodine containing compounds are resistant to oxygen plasma etching, and proposed two-level resist systems utilizing a mixture of iodine compounds and a commercially available positive photoresist(3). However, this resist has low resistance to O -RIE. 

The new silicon containing positive photoresists which consist of silicon compounds and a commercially available positive resist, OFPR-800, were evaluated as the top imaging layer in a two-level resist system. We sought silicon compounds specified by the following restrictions. 

Cis-(1,3,5,7-tetrahydroxy)-1,3,5,7-tetraphenyl cyclotetrasiloxane (phenyl-T (OH)j,), which can be looked upon as unit structure of PSQ, has been found to be soluble in an aqueous alkaline solution. The addition of phenyl-T (OH) and PSQ oligomer to commercially available positive photoresists has resulted in improved developability with alkaline solution. 

However, commercially available positive photoresists such as AZ1350J and HPR204 demonstrate greatly reduced sensitivity in the mid-UV region in comparison to their performance in the near-UV region. The reasons for this loss in sensitivity are as follows ... 

Positive and negative photoresists have their own advantages and disadvantages. General consideration of the photoresists includes its adhesion on the substrate, the minimum feature size permitted, the resistance to chemicals, the cost, and others. Most of the commercially available photoresists provide information about the properties and the suitable developers of the photoresists. 

Initially, the experiments apply a commercially available polyimide coating, which is well known from many microelectronic applications. The polyimide (PI 2545, HD Microsystems GmbH) is a high-temperature coating that can be patterned by a positive photoresist. It is dissolved in the same process step as the exposed resist using an alkaline photoresist developer [6], but by different etching rates. 

The main components of most commercially available positive photoresists are novolak as a binder and naphthoquinone-diazdde as a light-sensitive component. This light-sensitive compound is not base soluble and acts as a dissolution inhibitor for the novolak, which results in a very low dissolution rate of unexposed resist in aqueous base developer. Upon exposure a reaction is induced to yield indene carboxylic acid via a ketene ... 

There are many photoresists available commercially. These can be categorised into positive and negative tone resists. Various formulations of resists have differing properties (viscosity, ultimate achievable resolution, substrate adhesion etc.). Several classes of resist have thus been developed for different electronic applications. For example, high-resolution photolithography for patterning of submicron transistors requires a different resist to that needed for deep silicon etching of micro-electro-mechanical-systems (MEMS) stmctures. 

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