Experimentation and modeling of organic photocontamination on lithographic optics

Abstract

Photodeposition of organic films on transparent substrates irradiated in the presence of trace levels ͑ppb to ppm͒ of hydrocarbons has been experimentally investigated and a model is presented that describes the film growth behavior. The efficacy of a given organic precursor at forming a deposit is proportional to the product of its surface coverage ͑as governed by its partial pressure relative to its saturation partial pressure͒ and by its photon absorption cross section. These measurements are important in predicting the transmission characteristics of lithographic optics operating at 157, 193, and 248 nm wavelength. For example, a lens element irradiated continuously for 1 yr ͑1 kHz, 0.1 mJ/cm 2 /pulse͒ in the presence of 1 ppb of t-butyl benzene would exhibit a transmission of ϳ87% at 193 nm. The effects of oxygen-containing ambients are also documented, and methods for elimination and/or prevention of organic contamination are suggested.

Cavity-enhanced deep ultraviolet laser for two-photon cooling of atomic hydrogen

“…This was pursued in our previous work, where we demonstrated cw outputs of ≈ 600 mW at 243 nm [19]. Second, short wavelength optics are known to degrade when exposed to high power due to surface oxygen depletion [20] and hydrocarbon contamination [21]. In the UV [20], and extreme ultraviolet [22] degradation due to both effects has been mitigated by admitting O 2 at the location of the mirrors -albeit at a lower average power than what is required for two-photon laser cooling.…”

Impact of storage induced outgassing organic contamination on laser induced damage of silica optics at 351 nm

“…Microlithography and aerospace studies showed that airborne molecular contamination can be responsible for the degradation of optical performances. Reflective and transmissive losses have been correlated to organic contamination levels in many cases [6][7][8]. Moreover, in various studies, chemical contamination has been evidenced to be responsible for laser induced damage with high repetition rate laser [9][10][11][12].…”

UV light with oxygen treatment of phase shift photoblank for phase and transmission control: applicable to M x Si (1-x) O y N (y-1)

“…It is important to notice that the carbon is still present on the treated samples, although both materials were treated for a very long time. As reported by Kunz [8] organosilicon turn into the non volatile silicon dioxide when irradiated with 193nm laser. Although the mechanism is not clearly understood yet in this process, we believe a similar phenomenon to occur with both materials.…”