University of California

Other

The United States of America

Euv Limited Liability Corporation

Claude Montcalm

James Allen Folta

Paul B Mirkarimi

John S Taylor

Christopher E Walton

Eberhard A Spiller

Daniel G Stearns

Swie-In Tan

Sasa C Bajt

Ira Reiss

Stephen P Vernon

Figure errors are corrected on optical or other precision surfaces by changing the local density of material in a zone at or near the surface. Optical surface height is correlated with the localized density of the material within the same region. A change in the height of the optical surface can then be caused by a change in the localized density of the material at or near the surface.

Correction of localized shape errors on optical surfaces by altering the localized density of surface or near-surface layers

A method and system for determining a source flux modulation recipe for achieving a selected thickness profile of a film to be deposited (e.g., with highly uniform or highly accurate custom graded thickness) over a flat or curved substrate (such as concave or convex optics) by exposing the substrate to a vapor deposition source operated with time-varying flux distribution as a function of time. Preferably, the source is operated with time-varying power applied thereto during each sweep of the substrate to achieve the time-varying flux distribution as a function of time. Preferably, the method includes the steps of measuring the source flux distribution (using a test piece held stationary while exposed to the source with the source operated at each of a number of different applied power levels), calculating a set of predicted film thickness profiles, each film thickness profile assuming the measured flux distribution and a different one of a set of source flux modulation recipes, and determining from the predicted film thickness profiles a source flux modulation recipe which is adequate to achieve a predetermined thickness profile. Aspects of the invention include a computer-implemented method employing a graphical user interface to facilitate convenient selection of an optimal or nearly optimal source flux modulation recipe to achieve a desired thickness profile on a substrate. The method enables precise modulation of the deposition flux to which a substrate is exposed to provide a desired coating thickness distribution.

Method and system using power modulation and velocity modulation producing sputtered thin films with sub-angstrom thickness uniformity or custom thickness gradients

Spherical and non-spherical optical elements produced by standard optical figuring and polishing techniques are extremely expensive. Such surfaces can be cheaply produced by diamond turning; however, the roughness in the diamond turned surface prevent their use for EUV lithography. These ripples are smoothed with a coating of polyimide before applying a 60 period Mo/Si multilayer to reflect a wavelength of 134 &angst; and have obtained peak reflectivities close to 63%. The savings in cost are about a factor of 100.

Low-cost method for producing extreme ultraviolet lithography optics

A method and system for producing a thin film with highly uniform (or highly accurate custom graded) thickness on a flat or graded substrate (such as concave or convex optics), by sweeping the substrate across a vapor deposition source with controlled (and generally, time-varying) velocity. In preferred embodiments, the method includes the steps of measuring the source flux distribution (using a test piece that is held stationary while exposed to the source), calculating a set of predicted film thickness profiles, each film thickness profile assuming the measured flux distribution and a different one of a set of sweep velocity modulation recipes, and determining from the predicted film thickness profiles a sweep velocity modulation recipe which is adequate to achieve a predetermined thickness profile. Aspects of the invention include a practical method of accurately measuring source flux distribution, and a computer-implemented method employing a graphical user interface to facilitate convenient selection of an optimal or nearly optimal sweep velocity modulation recipe to achieve a desired thickness profile on a substrate. Preferably, the computer implements an algorithm in which many sweep velocity function parameters (for example, the speed at which each substrate spins about its center as it sweeps across the source) can be varied or set to zero.

Method and system for producing sputtered thin films with sub-angstrom thickness uniformity or custom thickness gradients

A method and system for producing a film (preferably a thin film with highly uniform or highly accurate custom graded thickness) on a flat or graded substrate (such as concave or convex optics), by sweeping the substrate across a vapor deposition source operated with time-varying flux distribution. In preferred embodiments, the source is operated with time-varying power applied thereto during each sweep of the substrate to achieve the time-varying flux distribution as a function of time. A user selects a source flux modulation recipe for achieving a predetermined desired thickness profile of the deposited film. The method relies on precise modulation of the deposition flux to which a substrate is exposed to provide a desired coating thickness distribution.

Method and system using power modulation for maskless vapor deposition of spatially graded thin film and multilayer coatings with atomic-level precision and accuracy

A high reflectance-low stress Mo&mdash;Si multilayer reflective coating particularly useful for the extreme ultraviolet (EUV) wavelength region. While the multilayer reflective coating has particular application for EUV lithography, it has numerous other applications where high reflectance and low stress multilayer coatings are utilized. Multilayer coatings having high near-normal incidence reflectance (R&gE;65%) and low residual stress (&lE;100 MPa) have been produced using thermal and non-thermal approaches. The thermal approach involves heating the multilayer coating to a given temperature for a given time after deposition in order to induce structural changes in the multilayer coating that will have an overall &ldquo;relaxation&rdquo; effect without reducing the reflectance significantly.

Process for fabricating high reflectance-low stress Mo&mdash;Si multilayer reflective coatings

Stress compensating systems that reduces/compensates stress in a multilayer without loss in reflectivity, while reducing total film thickness compared to the earlier buffer-layer approach. The stress free multilayer systems contain multilayer systems with two different material combinations of opposite stress, where both systems give good reflectivity at the design wavelengths. The main advantage of the multilayer system design is that stress reduction does not require the deposition of any additional layers, as in the buffer layer approach. If the optical performance of the two systems at the design wavelength differ, the system with the poorer performance is deposited first, and then the system with better performance last, thus forming the top of the multilayer system. The components for the stress reducing layer are chosen among materials that have opposite stress to that of the preferred multilayer reflecting stack and simultaneously have optical constants that allow one to get good reflectivity at the design wavelength. For a wavelength of 13.4 nm, the wavelength presently used for extreme ultraviolet (EUV) lithography, Si and Be have practically the same optical constants, but the Mo/Si multilayer has opposite stress than the Mo/Be multilayer. Multilayer systems of these materials have practically identical reflectivity curves. For example, stress free multilayers can be formed on a substrate using Mo/Be multilayers in the bottom of the stack and Mo/Si multilayers at the top of the stack, with the switch-over point selected to obtain zero stress. In this multilayer system, the switch-over point is at about the half point of the total thickness of the stack, and for the Mo/Be--Mo/Si system, there may be 25 deposition periods Mo/Be to 20 deposition periods Mo/Si.

Method to adjust multilayer film stress induced deformation of optics

A high reflectance-low stress Mo-Si multilayer reflective coating particularly useful for the extreme ultraviolet (EUV) wavelength region. While the multilayer reflective coating has particular application for EUV lithography, it has numerous other applications where high reflectance and low stress multilayer coatings are utilized. Multilayer coatings having high near-normal incidence reflectance (R.gtoreq.65%) and low residual stress (.ltoreq.100 MPa) have been produced using thermal and non-thermal approaches. The thermal approach involves heating the multilayer coating to a given temperature for a given time after deposition in order to induce structural changes in the multilayer coating that will have an overall 'relaxation' effect without reducing the reflectance significantly.

High reflectance-low stress Mo-Si multilayer reflective coatings

A buffer-layer located between a substrate and a multilayer for counteracting stress in the multilayer. Depositing a buffer-layer having a stress of sufficient magnitude and opposite in sign reduces or cancels out deformation in the substrate due to the stress in the multilayer. By providing a buffer-layer between the substrate and the multilayer, a tunable, near-zero net stress results, and hence results in little or no deformation of the substrate, such as an optic for an extreme ultraviolet (EUV) lithography tool. Buffer-layers have been deposited, for example, between Mo/Si and Mo/Be multilayer films and their associated substrate reducing significantly the stress, wherein the magnitude of the stress is less than 100 MPa and respectively near-normal incidence (5.degree.) reflectance of over 60% is obtained at 13.4 nm and 11.4 nm. The present invention is applicable to crystalline and non-crystalline materials, and can be used at ambient temperatures.

A passivating overcoat bilayer is used for multilayer reflective coatings for extreme ultraviolet (EUV) or soft x-ray applications to prevent oxidation and corrosion of the multilayer coating, thereby improving the EUV optical performance. The overcoat bilayer comprises a layer of silicon or beryllium underneath at least one top layer of an elemental or a compound material that resists oxidation and corrosion. Materials for the top layer include carbon, palladium, carbides, borides, nitrides, and oxides. The thicknesses of the two layers that make up the overcoat bilayer are optimized to produce the highest reflectance at the wavelength range of operation. Protective overcoat systems comprising three or more layers are also possible.

Growing community of inventors

Livermore, CA, United States of America

Claude Montcalm