Development of the Transmittance Measurement for EUV Resist by Direct-Resist Coating on a Photodiode

To increase the sensitivity of extreme-ultraviolet (EUV) resist, the method of adding high absorption material in base resin of the resist such as hafnium or zirconium metal has been developed. Since the EUV absorption of the base resin increases, the secondary electron emissions would increase to have a high-resist-exposure sensitivity. Thus to achieve the high sensitive EUV resist, it is important to evaluate EUV absorption of the EUV resist precisely. We have developed a novel transmittance measurement method to evaluate EUV resist absorption with high precision at BL10 beamline of NewSUBARU synchrotron light facility. In this novel method, a sample resist was coated on an EUV photodiode directly. The EUV transmittance of the resist was measured with photodiode signals before and after the coating. The resist thickness uniformity coating on a photodiode has much smaller value compared to that coating on a freestanding membrane. By novel method, the measurement precisions of the resist thickness and the EUV transmittance were significantly improved. As the result, the high measurement precision of absorption coefficient of 1% was achieved. This novel method will help the development of high sensitive EUV resist with the high-absorption material.