Reflective mask, reflective mask blank, and manufacturing method therefor
There are provided a reflective mask and a reflective mask blank reducing reflection of out-of-band light and a manufacturing method therefor. A light shielding frame is formed on a mask region corresponding to a multiply exposed boundary region between a chip and a semiconductor substrate. The frame is provided with an antireflective layer causing surface reflection in antiphase to out-of-band light reflected from the surfaces of a rear-surface conductive film and the substrate to provide a reflective mask reducing reflection of out-of-band light. The antireflective layer of the present disclosure has an electrical conductivity of 1×104/mΩ or greater to minimize charging occurring in a pattern region in observing the region using an electron microscope.
1. A reflective mask blank comprising:
a substrate;
a multi-layer reflective layer formed on a front surface of the substrate;
a protective layer formed on the multi-layer reflective layer; and
an absorbing layer formed on the protective layer, wherein:
the absorbing layer is provided with a circuit pattern region having an outer portion which at least partially includes a light shielding frame having low reflectivity to EUV light and out-of-band light, with the absorbing layer, the protective layer and the multi-layer reflective layer being removed from the outer portion; and
the substrate within the light shielding frame is provided thereon with an antireflective layer containing at least one of Si, Mo, Ta, Cr, Ru, Al, Ti, Zn, Su, Hf, W, Zr, and Cu, or an oxide, nitride, or oxynitride thereof, and wherein the antireflective layer has an electrical conductivity of 1×10 4 /mΩ or greater.
2. The reflective mask blank according to claim 1 , wherein the antireflective layer causes surface reflection in antiphase to out-of-band light reflected from a rear-surface conductive film formed on a rear surface of the substrate.
3. The reflective mask blank according to claim 1 , wherein the antireflective layer causes surface reflection in antiphase to out-of-band light reflected from the front surface of the substrate.
4. A reflective mask, wherein the absorbing layer of the reflective mask blank according to claim 1 is patterned.
5. The reflective mask blank according to claim 1 , wherein the antireflective layer is made by selection and adjustment of an index of refraction of a material of the antireflective layer and a thickness of the antireflective layer to satisfy conditional equation (1) below so that the light is darkened by thin-film interference for a wavelength of 140 to 400 nm other than a 13.5 nm band in which reflection is reduced, and having a function of surface reflection in antiphase to out-of-band light reflected from the front surface of the substrate, wherein equation (1) is
2 nd cos θ= mλ (1),
wherein n is the index of refraction of the material of the antireflective layer, d is the thickness of the antireflective layer, θ is an angle of incidence of the light, λ is the wavelength of the light and m is a non-negative integer.
6. A manufacturing method for the reflective mask blank according to claim 1 , wherein the antireflective layer is formed by using any of sputtering, physical vapor deposition (PVD), ion plating, and chemical vapor deposition (CVD).
7. A manufacturing method for the reflective mask blank according to claim 1 , wherein the antireflective layer is formed on the substrate prior to forming the multi-layer reflective layer.
8. A manufacturing method for the reflective mask blank according to claim 1 , wherein the antireflective layer is formed on exposed parts of the substrate exposed after partially removing the multi-layer reflective layer.