Multi-Undulator Spiral Compact Light Source

Abstract

A compact, small foot print, light source based on electron beam acceleration for insertion devices in EUV range metrology and actinic mask inspection using coherent scattering methods includes spiral storage rings providing plane straight sections. A magnet structure generates emittance for brilliance and coherent light content. A booster feeds the storage ring by top-up injection and keeps electron beam intensity stable. A booster level below the storage ring receives the electron beam from a linear accelerator in a central booster area. The source fits into laboratories or maintenance areas. Injection, RF-acceleration, beam manipulating devices and large diagnostics systems are required once. Higher average currents stored in the spiral enhance central cone power. Bunches are limited by ion trapping and a gap clears ions. The current is increased in the spiral. Gain in central cone power increases 5 fold, assuming a gap size of half single storage ring circumference.

Claims

1-5. (canceled)

6. A spiral compact light source based on accelerator technology with multiple straight sections for implementing insertion devices, the compact light source comprising: a) a foot print requiring a floor space not larger than for a compact source with only one undulator; b) a plurality of storage rings combined in a spiral loop shape and including an uppermost loop and a lowermost loop; c) said spiral loops being connected by rotation of quarter arcs without vertical transfer sections; d) a return path from said uppermost loop to said lowermost loop being displaced by introducing a matching section in arc symmetry points of said lowermost loop and said uppermost loop not interfering with a structure of said storage rings; e) accelerator systems including injection, RF-accelleration, electron beam manipulating devices and diagnostics being only required once, as compared to a planar configuration of a plurality of storage rings; f) a ring filling having a gap defining an ion clearing efficiency being three times larger than for a duty cycle being equivalent to a single facility for alleviating average current limiting ion trapping effects, or alternatively g) an increased number of bunches and average electron beam intensity for a gap identical to a single loop facility, causing an overall central cone radiation power to be increased; and h) two anti-symmetrically disposed Lambertson septa for a top-up injection from a booster ring into said storage rings.

7. The compact spiral light source according to claim 6, wherein the light source provides light having characteristics for actinic mask inspection.

8. The compact spiral light source according to claim 7, wherein the light source provides light having a wavelength of 13.5 nm.

9. The compact spiral light source according to claim 6, wherein said plurality of storage rings include three storage rings and said overall central cone radiation power is increased by a factor of 5 rather than tripled by three undulators for said three storage rings.

10. The compact spiral light source according to claim 6, wherein said booster ring is positioned below said lowermost loop of said spiral configuration of storage rings from where the beam is extracted vertically by a Lambertson septum.

11. The compact spiral light source according to claim 6, wherein said injection system of said storage ring is placed in an upwardly oriented straight section interconnecting said lowermost loop and a next adjacent loop.

12. The compact spiral light source according to claim 6, wherein an accelerating cavity, said beam manipulating devices and said diagnostics are placed in an upwardly oriented straight section interconnecting said uppermost loop and an adjacent loop.

13. The spiral compact light source according to claim 6, wherein: said footprint is approximately 50 m.sup.2 in total; said plurality of storage rings includes three storage rings; and said footprint has a racetrack shape with two long straight sections achieved by a spiral configuration of said three storage rings, a positioning of said booster ring below said lowermost loop of said spiral storage ring configuration and a positioning of a linear accelerator inside said booster ring.

Description

[0021] Preferred embodiments of the present invention are hereinafter described with reference to the attached drawings which depict in:

[0022] FIG. 1 perspective view and top view of the spiral storage ring;

[0023] FIG. 2 rotation of the quarter to connect to the next storage ring level;

[0024] FIG. 3 schematic view of the quarter arc rotations; and

[0025] FIG. 4 conceptual view of the storage ring injection layout.

[0026] The basic elements of the spiral source are three identical storage rings positioned on top of each other, which are connected in a spiral form as shown in FIG. 1 and constituting in this way one unit. Each of the loops contains one undulator which, if not used for actinic mask inspection, could be optimized for a different wavelength range (wavelength could be at EUV but may also be higher or lower according to the design of the periodicity and the distance of the magnet poles in the undulator. The three half rings in the back of FIG. 1 are hosting the three undulators. There is no special vertical deflection required to transport the beam from one level to the other. The quarter arcs (in front of FIG. 1) are simply bent in order to connect with the adjacent ring. The left quarter arc in front of SR-1 is bent upwards in the way as shown in FIG. 2, whereas the right quarter arc of SR-2 is bent downwards. The same configuration is implemented between SR-2 and SR-3. For the return arc from SR-3 to SR.1 the quarter arc is displaced by 0.5 to 1 m in order to not interfere with the front structure of the rings. The conceptual view of the transfer paths is shown in FIG. 3. The inclination of the transfer path angles are =7.4 between two loops and =14.8 for the return path.

[0027] The design of the booster synchroton follows the racetrack shape of the spiral storage ring and is positioned below the lowest loop of the spiral storage ring. The injection in the storage ring is performed vertically on the slope between SR-1 and SR-2. The beam coming from the booster enters a Lambertson septum (LS) with horizontal displacement and angle and points after the vertical deflection of the LS to the downstream located pulsed nonlinear multipole kicker (NK) where it gets captured in the acceptance of the storage ring. FIG. 4 shows conceptually the vertical and horizontal beam transfer.

[0028] For top-up injection from the booster ring into the storage ring two antisymmetrically arranged Lambertson septa are used. For the injection into the storage ring, a pulsed multipole system is used which leaves the stored beam unaffected during the injection process.

[0029] The linear accelerator fits fully within the structure of the storage ring. This measure also contributes to the demand of reducing the footprint of the source.

[0030] Accelerating RF-cavities, beam manipulating devices and large scale diagnostics will be positioned in the second straight section connecting SR-2 with SR-3.

[0031] Further preferred embodiments of the present invention are listed in the depending claims.

REFERENCES

[0032] [1] A. Wrulich et al, Feasibility Study for COSAMIa Compact EUV Source for Actinic Mask Inspection [0033] [2] A. Streun: COSAMI lattices: ring, booster and transfer line, Internal note, PSI Jun. 28, 2016.

[0034] with coherent diffraction imaging methods [0035] [3] A. Wrulich, Ion trapping . . . .