New Concept of Contrast Enhancement of Resist and Its Application to Positive‐Type Resist

We have developed a new contrast enhancement technique, contrast enhancement technique by ionic strength controlling, for the resist process. We applied this technique to the development of positive-type electrodeposition resist. By adjusting the resist resin to the ionic strength of the developer, the contrast was greatly improved. The sensitivity for the ultraviolet exposure was not reduced with this technique. The dissolution of the unexposed resist was completely inhibited by the salting-out effect, while the dissolution of the exposed resist was kept high. The degradation of the resist surface during the development was prevented. Otherwise the pattern of this resist was removed by dissolving to aqueous alkaline of low ionic strength, because the salting-out effect prevented the dissolution during development. In the printed circuit board production, very wide process latitude was obtained for the pattern transfer with this contrast enhanced resist.