Effects of film thickness and alkaline concentration on dissolution kinetics of poly(4-hydroxystyrene) in alkaline aqueous solution

The dissolution behavior of a simple combination of poly(4-hydroxystyrene) (PHS) films and tetramethylammonium hydroxide (TMAH) aqueous solution was analyzed to gain a fundamental understanding of the effects of film thickness and alkaline concentration on the dissolution kinetics of chemically amplified resists (CARs). Films of four different thicknesses, from thick (approximately 900 nm) to thin (approximately 50 nm), were developed in 22 different developers of different concentrations. The dissolution behavior of each combination was observed using a quartz crystal microbalance (QCM). Differences in dissolution kinetics due to film thickness were observed even between relatively thick films such as 900- and 500-nm thick films in dilute developers. These differences were considered to be caused by the diffusion of the solution into the films. Thin films also showed characteristic behavior with dilution. This behavior was due to the interaction between the substrate and the films, unlike in the case of thick films.

Highly spatial-resolved chemical metrology on latent resist images

Patterning photoresist with extreme control over dose and placement is the first crucial step in semiconductor manufacturing. But, how to accurately measure the activation of modern complex resists components at sufficient spatial resolution? No exposed nanometre-scale resist pattern is sufficiently sturdy to unaltered withstand inspection by intense photon or electron beams, not even after processing and development. This paper presents experimental proof that Infra-Red Atomic Force Microscopy (IR-AFM) is sufficiently sensitive and gentle to chemically record the vulnerable-yet-valuable lithographic patterns in a chemically amplified resist after exposure, prior to development. Accordingly, IR-AFM metrology provides the long-sought-for insights in changes in the chemical and spatial distribution per component in a latent resist image, both directly after exposure as well as during processing. With these to-be-gained understandings, a disruptive acceleration of resist design and processing is expected.

Formulation of trade-off relationships between resolution, line edge roughness, and sensitivity in sub-10 nm half-pitch region for chemically amplified extreme ultraviolet resists

The manufacturing of semiconductor devices using extreme ultraviolet (EUV) lithography started in 2019. A high numerical aperture (NA) tool under development is capable of resolving 8 nm line-and-space optical images and will extend the application of EUV lithography. However, resist materials have not been yet applicable to the production with 8 nm resolution. In this study, the relationships among the half-pitch of line-and-space patterns (resolution), chemical gradient [an indicator of line edge roughness (LER)], and sensitivity were investigated in the sub-10 nm half-pitch region for chemically amplified EUV resists. The chemical gradient was simulated on the basis of their sensitization and reaction mechanisms. The relationship was formulated as a function of total sensitizer concentration (the sum of photoacid generator and photodecomposable quencher concentrations) and the thermalization distance of secondary electrons. The effect of thermalized electrons was well incorporated into the trade-off relationships between resolution, LER, and sensitivity.

Understanding the Exposure Process in the Extreme Ultra Violet Lithography

Although being the optical lithography, the extreme ultraviolet (EUV) lithography with 13.5-nm wavelength is very different from the deep ultraviolet (DUV) lithography with 193-nm wavelength. Hence, the understanding of the complex detailed EUV mechanisms to cause a chemical reaction in chemically amplified resists (CARs) is required to develop EUV resists and exposure process. In this paper, for organic, metal-organic and metal-oxide resists, the electron-scattering model of exposure mechanisms needs to include the elastic and inelastic mean free paths. On top of that, Dill’s parameters of DUV and EUV resisters from the photo-generated reaction are discussed to indicate the physical and chemical characteristics. For CAR and EUV resists, Dill B parameter is large than Dill A and B parameters.