Measurement of resist response to heating

Resist heating is one of the major contributors to errors in high-throughput maskmaking using electron-beam lithography. Temperature affects the physical and chemical properties of resists. Response of resist sensitivity to the temperature was measured for a number of electron-beam resists. The following resists were characterized: PMMA, PBS, SPR-700, EBR-900, ZEP-7000, and chemically amplified resist UVII-HS. Two methods were used for such measurements: (a) using a heated stage, the temperature of which was controlled externally, (b) using a test pattern exposed at regular exposure conditions. Nonlinearity of sensitivity response was found for a number of resists. A resist heating quality parameter was introduced which allowed a practical comparison of resists in terms of heating. Resists were compared using this parameter.