Double patterning process

A double pattern forming process comprising the steps of:

• coating a chemically amplified positive resist composition onto a processable substrate, said resist composition comprising a resin comprising recurring units having an alkali-soluble group protected with an acid labile group which is eliminatable with acid, a photoacid generator, and a solvent, and prebaking the resist composition to remove the unnecessary solvent to form a resist film,
• coating a protective film-forming composition onto the resist film and heating to remove an unnecessary solvent to form a protective film,
• exposing the resist film to high-energy radiation in a first pattern of exposed and unexposed areas, post-exposure baking for causing the acid generated by the acid generator upon exposure to act on the acid labile groups on the resin whereby the acid labile groups on the resin in the exposed area undergo elimination reaction so that the resin in the exposed area becomes alkali soluble, and developing the exposed resist film with an alkaline developer to form a first positive resist pattern,
• treating the first resist pattern so as to eliminate the acid labile groups on the resin in the first resist pattern and to induce crosslinking in the resin to such an extent that the resin may not lose a solubility in an alkaline developer, for thereby endowing the first resist pattern with resistance to an organic solvent to be used in a reversal film-forming composition,
• coating a reversal film-forming composition thereon to form a second resist film, said reversal film-forming composition being a chemically amplified negative resist composition comprising a resin comprising recurring units having an alkali-soluble group, a photoacid generator, an acid crosslinker and a solvent, and prebaking the second resist composition to remove the unnecessary solvent to form the second resist film,
• coating a protective film-forming composition onto the reversal film and heating to remove an unnecessary solvent to form a protective film, and
• exposing the second resist film to high-energy radiation in a second pattern of exposed and unexposed areas, post-exposure baking for causing the acid generated upon exposure to act on the crosslinker whereby the resin in the exposed area is converted to be insoluble in alkaline developer, and developing the exposed second resist film with an alkaline developer to form a second negative resist pattern,
• wherein the last step of developing the exposed second resist film with an alkaline developer to form a second negative pattern includes the reversal transfer step of dissolving away the first positive pattern which has been converted to be soluble in the alkaline developer, so as to define a space pattern in the second negative resist film, thereby forming a reversal transfer pattern of the first positive resist film as well as the step of forming the second negative pattern.