Pattern forming method and plasma processing method

A pattern forming method, comprising:

• forming a molecular assembly layer of a triptycene derivative having a triptycene skeleton on a substrate, wherein the molecular assembly layer of the triptycene derivative has an assembly structure in which a plurality of single molecules of the triptycene derivative are aligned and assembled in a horizonal direction and a vertical direction, the assembly structure including a first assembly being a vertical stack of first side chains of the triptycene derivative and a second assembly being a vertical stack of second side chains of the triptycene derivative, that are alternatingly arranged in the horizontal direction;
• and
• performing an etching treatment to the molecular assembly layer of the triptycene derivative such that the first assembly is etched and the second assembly remains, thereby forming a pattern on the substrate, wherein
• the triptycene skeleton includes
• a first plane in which position 1, position 8, and position 13 of the triptycene skeleton are arranged, and
• a second plane in which position 4, position 5, and position 16 of the triptycene skeleton are arranged, and
• the triptycene derivative includes
• the first side chain on a one plane side, the one plane side being on a side of one plane from among the first plane and the second plane, and
• the second side chain on another plane side or on the one plane side, the another plane side being on a side of another plane from among the first plane and the second plane, and
• the second side chain is different from the first side chain in an etching selectivity ratio.