Mechanisms involved in HBr and Ar cure plasma treatments applied to 193 nm photoresists

Abstract

In this article, we have performed detailed investigations of the 193 nm photoresist transformations after exposure to the so-called HBr and Ar plasma cure treatments using various characterization techniques (x-ray photoelectron spectroscopy, Fourier transformed infrared, Raman analyses, and ellipsometry). By using windows with different cutoff wavelengths patched on the photoresist film, the role of the plasma vacuum ultraviolet (VUV) light on the resist modifications is clearly outlined and distinguished from the role of radicals and ions from the plasma. The analyses reveal that both plasma cure treatments induce severe surface and bulk chemical modifications of the resist films. The synergistic effects of low energetic ion bombardment and VUV plasma light lead to surface graphitization or cross-linking (on the order of 10 nm), while the plasma VUV light (110–210 nm) is clearly identified as being responsible for ester and lactone group removal from the resist bulk. As the resist modification depth depends strongly on the wavelength penetration into the material, it is found that HBr plasma cure that emits near 160–170 nm can chemically modify the photoresist through its entire thickness (240 nm), while the impact of Ar plasmas emitting near 100 nm is more limited. In the case of HBr cure treatment, Raman and ellipsometry analyses reveal the formation of sp2 carbon atoms in the resist bulk, certainly thanks to hydrogen diffusion through the resist film assisted by the VUV plasma light.

Benefits of plasma treatments on critical dimension control and line width roughness transfer during gate patterning

“…19 The 193 nm photoresist studied in this work is IM5010 commercial resist from Dow Electronic Materials whose chemical structure is close to poly(methyl methacrylate) (PMMA) derived polymer with several pending groups such as adamantyl methacrylate for the leaving group, alphagamma butyrolactone methacrylate for the solubility and a polar group. 19 Two types of substrates have been used: 130 nm thick photoresist films coated on silicon substrate and photoresist patterns printed by 193 nm lithography on 35 nm Si-ARC/ 200 nm SOC hard mask/Si bulk stack. The patterns studied here are isolated lines with height of 120 nm and width of 70 nm.…”

“…In previous articles, [19][20][21] we studied the impact of HBr plasma treatment and the role of the vacuum ultra violet (VUV) light emitted by the HBr plasma on the chemical modifications and resulting roughness of 193 nm photoresists. We have shown that both HBr plasma and VUV light treatments lead to similar resist bulk chemical modifications that favors resist surface roughness smoothening.…”

Relationship between nanoscale roughness and ion-damaged layer in argon plasma exposed polystyrene films

“…poly͑methyl methacrylate͒ ͑PMMA͒, 8 193 and 248 nm photoresists 5,6,9,10 ͔ and has been described as a thin, highly crosslinked and graphitized layer. [4][5][6][11][12][13][14][15][16] We have previously shown that under energetic Ar + ion bombardment during plasma etching, a dense, amorphous carbonlike modified layer is formed at the surface of a wide range of polymers ͓polystyrene ͑PS͒, poly͑␣-methylstyrene͒, poly͑4-methylstyrene͒, PMMA, poly͑hydroxyadamantyl acrylate͒, and poly͑hydroxyadaman-tyl methacrylate͔͒ with a thickness of a few nanometers. 17 This modified layer forms within the first few seconds of plasma exposure ͑corresponding to an ion fluence ϳ4 ϫ 10 16 cm −2 ͒, concurrent with a period of rapid surface roughening.…”

A Comparative Study of HBr-Ar and HBr-Cl2 Plasma Chemistries for Dry Etch Applications

“…Also, the HBr-containing plasmas have been successfully applied for the highly-anisotropic etching of both single crystal and poly-Si because of the negligible spontaneous reaction between Br and Si [3,4]. And finally, the HBr-rich plasmas provide much lower (compared with the Cl-containing plasmas) etch rates of organic photoresists (PR) due to the graphitization and the cross-linking of the PR film caused by the UV (*110-210 nm) irradiation from the excited HBr molecules [5,6]. Unfortunately, the most of existing works discuss only the effects of main operating parameters (gas pressure, input power, bias power and gas mixing ratio) on the etch rate and related characteristics while the relationships between plasma parameters, plasma composition and etch kinetic have received much less attention.…”