CN103149618B - Light spectrum purification filter device for laser plasma extreme ultraviolet lithography source - Google Patents

Abstract

The invention discloses a light spectrum purification filter device for a laser plasma extreme ultraviolet lithography source. The device is characterized by sequentially comprising a first optical grating coated with film on a surface, a thin metal sheet with high transmittance for a light spectrum with 13.5nm, and a second light grating coated with film on the surface, wherein surfaces of the first light grating, the second light grating and the thin metal sheet are mutually parallel, line directions of the first light grating and the second light grating are mutually vertical, a light grating constant is 10-150nm, a duty ratio is 40-60 percent, and the thickness is 1-10mm. The thin metal sheet is made from zirconium or molybdenum, and the thickness is 0.1-5mm. The device has a simple structure, and the light spectrum of laser plasma radiation is enabled to be purified.

Description

Spectral purification filter device for laser plasma extreme ultraviolet lithography light source

technical field

The invention relates to extreme ultraviolet lithography, in particular to a spectral purification filter device for laser plasma extreme ultraviolet lithography light source.

Background technique

The extreme ultraviolet (EUV) light source with a wavelength of 13.5nm±1% is generally considered to be the next-generation lithography light source after 193nm, and the laser plasma extreme ultraviolet light source (LPP) is especially concerned by scientists from all over the world. LPP generates plasma electromagnetic radiation by focusing a high-power, high-repetition-frequency laser beam on a tin or zinc target pellet in a droplet state, and then collects and focuses the desired wavelength spectrum on the intermediate focus through the collector and spectral purification filter unit . Because the plasma not only radiates the in-band spectrum of 13.5nm±1%, but also includes the out-of-band spectrum in addition to the in-band spectrum. Spectral purification and filtering technology must be used to filter out the out-of-band spectral energy in order to meet the requirements of the EUV exposure system.

A spectral purity filtering method is first disclosed in technology 1 "Spectral purity filter, lithographic apertures, and method for manufacturing a spectral purity filter" (US Patent 2012/0154778AI). A regular hexagonal grid, and then coated on the grid to achieve spectral purification. The method can strongly reflect the infrared spectrum with a wavelength greater than 1 μm, especially the infrared spectrum with a wavelength greater than 10 μm, and has high transmittance for the spectrum with a wavelength less than 100 nm.

The current technology 1 has a high reflectivity for the infrared spectrum, and the effect is not obvious for the deep ultraviolet-visible light band in the out-of-band band. It must cooperate with other spectral purification filtering technologies to obtain a relatively pure 13.5nm±1% spectrum.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned problems in the prior art, and to provide a spectral purification filter device for laser plasma extreme ultraviolet lithography light source. The device has a simple structure and can purify the spectrum of laser plasma radiation.

Technical solution of the present invention is as follows:

A spectral purification filter device for laser plasma extreme ultraviolet lithography light source, characterized in that it consists of a first grating with a surface coating, a thin metal sheet with high transmittance for the 13.5nm spectrum, and a second grating with a surface coating Grating, the surfaces of the first grating, the thin metal sheet and the second grating are parallel to each other, the first grating and the second grating have the same structure, the lines of the first grating and the second grating are perpendicular to each other, the first grating and the second grating The grating constant of the second grating is 10-150 nm, the duty cycle is 40%-60%, and the thickness is 1-10 mm.

The first grating and the second grating are made of silicon material, and the surface is coated with ZrSi ₂ or MoSi ₂ film, which have a strong reflection effect on the spectrum with a wavelength greater than 100nm.

The typical value of the grating constant of the first grating and the second grating is 100 nm.

The thin metal sheet is made of zirconium or molybdenum, has a thickness of 0.1-5 mm, and has a relatively high reflectivity for the extreme ultraviolet spectrum with a wavelength of less than 10 nm.

The advantages of the present invention are:

1 The present invention uses a one-dimensional grating, which is easy to manufacture and low in cost.

The angle between the surface of the first grating and the second grating described in 2 and the optical axis is 30° to 60°, which can reflect the spectrum with a wavelength greater than 100nm out of the cavity, and the reflected spectrum can be used as a detection signal, while avoiding damage to the target cavity. heating effect.

3. The first grating, the second grating and the thin metal sheet are used to filter the out-of-band spectrum, which reduces the heat load of each device and improves the system stability.

Description of drawings

FIG. 1 is a relative positional diagram of the first grating 11, the thin metal sheet 12 and the second grating 13 of a spectral purification filter device 18 used for a laser plasma extreme ultraviolet lithography light source according to the present invention.

FIG. 2 is a front view of the first grating 11 or the second grating 13 according to the present invention.

Fig. 3 is a structure diagram of a laser plasma lithography light source of the present invention.

Detailed ways

Below, the present invention will be further described in conjunction with the accompanying drawings, but the protection scope of the present invention should not be limited thereby.

Please refer to FIG. 3 first. FIG. 1 is a relative positional diagram of the first grating 11, the thin metal sheet 12 and the second grating 13 of a spectral purification filter device for laser plasma EUV lithography light source according to the present invention. It can be seen from Fig. 1 that the composition of the spectrum purification filtering device according to the present invention comprises in turn the first grating 11 of the surface coating, the thin metal plate 12 with high transmittance for the 13.5nm spectrum and the second grating 13 of the surface coating, the first The lines of the grating 11 and the second grating 13 are perpendicular to each other, the grating constant is 10-150 nm, the duty ratio is 40%-60%, and the thickness is 1-10 mm.

The first grating 11 and the second grating 13 are made of silicon material, and the surface is coated with ZrSi ₂ or MoSi ₂ film, which have a strong reflection effect on the spectrum with a wavelength greater than 100nm.

The typical value of the grating constant of the first grating 11 and the second grating 13 is 100 nm.

The thin metal sheet 12 is made of zirconium or molybdenum, with a thickness of 0.1-5mm, and has a relatively high reflectivity for the extreme ultraviolet spectrum with a wavelength less than 10nm.

FIG. 2 is a front view of the first grating 11 according to the present invention. The structure of the first grating 11 is the same as that of the second grating 13 , with a typical size of 200mm*200mm, a grating constant of 10-150nm, such as 100nm, and a duty cycle of 40%-60%. The grating is made of silicon material through photolithography process, and the surface is coated with ZrSi ₂ or MoSi ₂ film.

Fig. 3 is a schematic structural diagram of a laser plasma lithography light source of the present invention. As shown in the figure, a high-power, high-repetition _CO2 laser beam 1 with a wavelength of 10.6 microns parallel to the optical axis 19 of the laser plasma lithography light source is focused on the tin droplet 3 in the plasma cavity 5 through the condenser lens 2 ( generated by the droplet generator, omitted in the figure). After the focus point of the laser beam 1 interacts with the tin droplet 3, a high temperature plasma is generated. In addition to the in-band spectrum10, the electromagnetic radiation of high-temperature plasma also includes the extreme ultraviolet-deep ultraviolet-visible light out-of-band spectrum9. The collector 4 collects electromagnetic radiation in all wavelength bands, outputs it to the spectral purification and filtering vacuum chamber 6 through the first window 14 , focuses it on the intermediate focal point 17 , and finally enters the lithography illumination system 7 . In addition to the above-mentioned out-of-band spectrum 9 and in-band spectrum 10, the spectrum entering the spectral purification and filtering vacuum chamber 6 also includes out-of-band spectra 8 with wavelengths of 1.06 μm and 10.6 μm generated by the laser drive source. The spectrum purification filter device 18 (comprising the first grating 11, thin metal sheet 12 and second grating 13) of the present invention is placed in the spectrum purification filter vacuum cavity 6, and the grating surfaces of the first grating 11 and the second grating 13 are in contact with the laser plasma The included angle of the optical axis 19 of the lithography light source is adjustable from 30° to 60° (the mechanical bracket used for fixing, maintaining a relatively parallel relationship and adjusting the angle is omitted in the figure), and the typical value of this embodiment is 45° , and the out-of-band spectrum 8 and out-of-band spectrum 9 are filtered out, the in-band spectrum 10 can be focused to the intermediate focus 17 by the spectral purification filter device 18, and the in-band spectrum 10 is output to the lithography illumination system after passing through the second window 16 7. The first grating 11 and the second grating 13 are used in cooperation with each other, and have a strong reflection effect on the out-of-band spectrum with a wavelength above 100 nm. The thin metal sheet 12 with a thickness of 0.1-5mm is made of zirconium or molybdenum, which can filter out the out-of-band spectrum with a wavelength below 100nm. The out-of-band spectra 8 and 9 pass through the third window 15 after being reflected by the spectral purification filter device 18 of the present invention, and can be used to monitor the interaction between the focal point of the laser beam 1 and the zinc droplet 3 (the monitor is omitted in the figure). On the other hand, the heating effect on the cavity can be reduced.

Claims (4)

1. A spectrum purification filter device for laser plasma extreme ultraviolet lithography light source, characterized in that its composition comprises successively the first grating (11) of surface coating, the thin metal sheet (13.5nm spectrum with high transmittance) 12) and the second grating (13) of surface coating, the surface three of described first grating (11), thin metal sheet (12) and second grating (13) are parallel, the first grating (11) and the first grating The two gratings (13) have the same structure, the line directions of the first grating (11) and the second grating (13) are perpendicular to each other, the grating constant is 10-150nm, the duty ratio is 40%-60%, and the thickness is 1-150nm. 10mm. 2. The spectral purification filter device according to claim 1, characterized in that said first grating (11) and second grating (13) are made of silicon single crystal material, and the surface is coated with ZrSi ₂ or MoSi ₂ film , It has high reflectivity for the spectrum with a wavelength greater than 100nm. 3. The spectral purification filtering device according to claim 1, characterized in that the grating constant of the first grating (11) and the second grating (13) is 100 nm. 4. The spectral purification filter device according to any one of claims 1 to 3, characterized in that the thin metal sheet (12) is made of zirconium or molybdenum, with a thickness of 0.1 to 5mm, for extreme ultraviolet light with a wavelength of less than 10nm The spectrum has high reflectivity.