Diffractive element in extreme-UV lithography condenser
AssigneeEuv LLC
InventorsWilliam C. Sweatt, Avijit Ray-Chaudhuri
Life of this patent
Estimating the term…
Abstract
Condensers having a mirror with a diffraction grating in projection lithography using extreme ultra-violet significantly enhances critical dimension control. The diffraction grating has the effect of smoothing the illumination at the camera's entrance pupil with minimum light loss. Modeling suggests that critical dimension control for 100 nm features can be improved from 3 nm to less than about 0.5 nm.
Claims19
A process for fabricating a device comprising at least one element having a dimension of less than or equal to 0.25 micron which comprises the steps of:
- providing a source of extreme ultra-violet (EUV) radiation;
- providing a condenser system succeeding the source wherein the condenser system has a set of mirrors for collecting the EUV radiation and transforming the EUV radiation into one or more beams and has correcting mirrors which are capable of translating or rotating, or both, one or more beams from said set of mirrors, wherein at least one of the correcting mirrors, or a mirror that is common to all sets, has a diffraction grating on its surface and wherein the diffraction grating comprises an essentially uniform frequency, phase only reflecting binary optical element that has at least two levels and wherein the condenser system produces substantially parallel arc-shaped light beams that are transmitted to a reflective mask pattern and then reflected therefrom to produce corresponding pattern image regions on the device being fabricated;
- and
- constructing one or more levels in the device being fabricated by removing or adding materials in the pattern image regions on the device being fabricated.
A process for fabricating a device comprising at least one element having a dimension of less than or equal to 0.25 micron which comprises the steps of:
- providing a small diameter source of extreme ultra-violet (EUV) radiation;
- providing a condenser system succeeding the source wherein the condenser system comprises:
- (i) at least two substantially equal radial segments of a parent aspheric mirror, each having one focus at the radiation source and a line focus filling the object field of a ringfield camera at the radius of the ringfield and each producing a beam of radiation;
- and
- (ii) a corresponding number of sets of correcting mirror means which are capable of translation or rotation, or both, such that all of the beams of radiation pass through the real entrance pupil of the camera and form a coincident arc image at the ringfield radius, wherein one of the correcting mirrors of each set, or a mirror that is common to said sets of mirrors, from which the radiation emanates has a diffraction grating on its surface and wherein the diffraction grating comprises an essentially uniform frequency, linear, phase only reflecting binary optical element that has at least two levels wherein the condenser system produces substantially parallel arc-shaped light beams that are transmitted to a reflective mask pattern and then reflected therefrom to produce corresponding pattern image regions on the device being fabricated;
- and
- constructing one or more levels in the device being fabricated by removing or adding materials in the pattern image regions on the device being fabricated.
Dependencies are inferred from the claim text.