Unraveling the effect of resist composition on EUV optics contamination

EUV lithography is the most promising new technology for the next node of semiconductor devices. Unfortunately, the high energy photons are likely to generate more contamination than observed with ArF or KrF light which can reduce the transmission of the EUV optics. Resist outgassing is considered to be an important contamination source, however, not enough is known about the way a resist composition influences the contamination growth rate, while this information is crucial to guide the development of EUV resists. To reduce the knowledge gap, FUJIFILM and imec started a joint effort aimed at systematically exploring the contribution of the different resist components and at understanding the effect of chemical modifications of the different components on the contamination tendency of resists. The project focuses on (1) the identification and quantification of the outgassing components from resist by RGA measurements, (2) on the quantification of the resist related contamination rate by witness sample (WS) testing, and (3) on the correlation between these two results knowing the details of the resist chemistry. To explore the effect of the resist composition upon contamination growth, the following approach was followed. The focus was put on chemically amplified resists (CAR), since this chemistry is mostly used in EUV lithography. Both PAG blended as well as PAG bound systems were explored, and the following resist components are individually varied: polymer matrix, blocking groups, PAG type and concentration. In this way the total contamination of a resist can be divided into the separate contributions of the different resist components upon the contamination growth rate, which is a huge step forward in the understanding of optics contamination due to resist.