Dual mandrel sidewall image transfer processes

A method of forming a patterned structure comprising:

• forming a first mandrel structure on a top surface of a material layer;
• forming a first spacer around said first mandrel structure;
• forming a second mandrel structure that straddles a portion of said first spacer;
• forming a second spacer around the second mandrel structure;
• transferring a composite pattern of at least one portion of said first spacer and at least one portion of said second spacer into said material layer by an etch;
• masking one or more portions of said first and second spacers with a masking material layer, while physically exposing a rest of said first and second spacers;
• and
• etching at least one physically exposed portion of said first and second spacers while said masked one or more portions of said first and second spacers are not etched.

A method of forming a patterned structure comprising:

• forming a first mandrel structure on a top surface of a material layer;
• forming a first spacer around said first mandrel structure;
• forming a second mandrel structure that straddles a portion of said first spacer;
• forming a second spacer around the second mandrel structure;
• transferring a composite pattern of at least one portion of said first spacer and at least one portion of said second spacer into said material layer by an etch;
• masking one or more portions of said first and second spacers with a masking material layer, while physically exposing a rest of said first and second spacers;
• and
• selectively depositing a material on at least one physically exposed portion of said first and second spacers while no material is deposited on said masked one or more portions of said first and second spacers.

A method of forming a patterned structure comprising:

• forming a first mandrel structure on a top surface of a material layer;
• forming a first spacer around said first mandrel structure;
• forming a second mandrel structure that straddles a portion of said first spacer;
• forming a second spacer around the second mandrel structure;
• transferring a composite pattern of at least one portion of said first spacer and at least one portion of said second spacer into said material layer by an etch;
• forming a matrix layer that fills a complementary region that is not occupied by said first mandrel structure and said first spacer over said material layer;
• planarizing said matrix layer employing said first spacer, wherein said matrix layer embeds said first mandrel structure and said first spacer, and said second mandrel structure and said second spacer are formed on a top surface of said matrix layer.