Jui-Ching Wu

An accurate method to determine the amount of out-of-band light in an EUV scanner

In this paper, we proposed a new design of the test mask to measure the amount of the out-of-band (OOB) light from an extreme-ultraviolet (EUV) light source by detuning the period of the multilayer (ML), rather than changing the material of the absorber, to suppress reflection of EUV light. The new OOB test mask also reflects essentially the same OOB light as that of the production mask at each wavelength in the whole OOB spectral range. With the help of the new OOB test mask, the contributions to the background intensity from in-band flare and OOB light can be correctly separated and an accurate optical-proximity-correction (OPC) model can be established.

Quencher distribution engineering for out-of-band insensitive EUV resists: experiments and stochastic simulation

We investigated the effect of quencher type and loading concentration in OoB-insensitive EUV resists via actual exposure on the latest EUV scanner and stochastic simulation using Prolith. Model resist samples with two quencher types, conventional base type and photo-decomposable base type, at variant loading concentrations were prepared and tested. Basic indicators of lithographic performance, such as depth of focus, energy latitude, and line-width roughness were significantly improved by 80 nm, 8.4% and 25%, respectively along with a moderate increase of sensitivity (ca. 5mJ/cm2) under the optimized quencher condition. Meanwhile, we further quantitatively analysis the outgassing-induced contamination growth to realize the quencher distribution engineering effect on outgassing issue in EUV lithography. In addition, stochastic simulation for EUV resist featuring various types of quenchers provides certain correlation with the experimental results.

The role resist plays in EUVL extensibility

In this paper, the impact of resist on the lithographic process window is investigated. To estimate the resolution limit of EUVL due to the limitation from resist performance, a simplified resist model, called diffused aerial image model (DAIM), is employed. In the DAIM, the resist is characterized by the acid diffusion length, or more generally, resist blur. Lithographic process windows with resists of various blurs are then calculated for different technology nodes. It is concluded that the resist blur needs to be smaller than 8 nm to achieve a reasonable window for the technology node with the minimum pitch of 32 nm. The performance of current resists can barely fulfill this requirement. Investigation of a more refined resist model is also initiated.