Patent ID: 7045467

Claim:
A method of determining the endpoint of an etch layer in a semiconductor element fabrication, wherein said element is comprised of at least a first material layer, a second material layer on said first material layer, said endpoint determining method comprises the steps of: (i) determining the total emission intensity wavelength of the first material layer; (ii) determining the total emission intensity wavelength of the second material layer; (iii) plotting the scalar of the wavelength differential of the first and second material layers; (iv) choosing the highest peak of wavelength differential as the best range of endpoint detection wavelength; wherein steps (i) and (ii) are conducted with a recipe which is effective in etching said second material layer; wherein the first material is nitrogen-rich silicon material has the general empirical formula Si x N y , including silicon nitride, Si 3 N 4 (hereinafter “SiN”), and the antireflective coating (ARC) layer is a bottom reflective coating (BARC), including organic and inorganic BARC materials; wherein the recipe includes a plasma etching environment having low source power, low bias power, low pressure and etch chemistries including Cl 2 and O 2 ; and wherein the plasma is a decoupled plasma source (DPS) having a pressure at about 0.8 Pa (6 mTorr), bias power at about 55 W, source power at about 350 W, Cl 2 flow rate at about 47 sccm and O 2 flow rate of 47 sccm.