Thin organic bottom antireflective coatings for 193 nm lithography

The need for constant reduction in critical dimensions (CD) of integrated circuits to make them faster has been the driving force for next generation lithography. Currently KrF (248nm) is the shortest wavelength of light being used by IC manufacturers to mass produce devices. If the semiconductor industry continues at the same pace of packing more information on a chip, shorter wavelength (193nm) (ArF Excimer laser) will soon be introduced in production. Shorter wavelengths mean larger swing ratios, CD variations, reflective notching and standing waves due to sharp increase in reflectivity. Therefore some mechanism to reduce reflectivity becomes increasingly important at shorter wavelengths. Bottom antireflective coatings (BARCs) will play an important role in this endeavor. This paper discusses the chemistry and performance of two new spin-on organic 193nm BARCs (ARC 27 and ARC 28) optimized for their use at 1st reflectivity minimum thickness (30-40nm). The optical values of ARC 27 (n= 1.7, k= 0.56) measured by ellipsometer at 193nm give 0% reflectivity at the 1st reflectivity minimum with the optimum thickness of the BARC being 30nm. Lithographic studies with 193nm photoresist show good performance down to 90nm with isolated line (PAR705) and 100nm with dense line photoresist (PAR710,718). The optical properties of ARC 28 are 1.53 and 0.54 and a nominal thickness of 40nm on silicon is recommended to achieve 0% reflectivity. It shows good resolution at 110nm L/S and broad photoresist compatibility.