CN106959482A - Two-dimensional single-stage diffraction grating for extreme ultraviolet - Google Patents

Abstract

The invention discloses a two-dimensional single-stage diffraction grating for extreme ultraviolet light, which comprises: a transparent base and a grid layer located on the surface of the transparent base; the grid layer has a plurality of transparent grating bars and a plurality of opaque gratings strips; the light-transmitting grating strips and the light-transmitting grating strips are alternately distributed in the first direction, and the light-transmitting grating strips and the light-impermeable grating strips all extend along the second direction, and the first direction is perpendicular to the In the second direction; in the first direction, the opposite sides of the light transmission grating strips are zigzag; and the width of the light transmission grating strips in the first direction is the same everywhere. The technical solution of the present invention realizes diffraction through zigzag-shaped grating strips and opaque grating strips, the width of the grating strips remains unchanged, and randomly distributed translucent grating strips are set so that the width of the opaque grating strips meets the preset random distribution. It can eliminate high-order harmonics while achieving diffraction for preset bands.

Description

A two-dimensional single-order diffraction grating for extreme ultraviolet

technical field

The invention relates to the technical field of optical devices, in particular to a two-dimensional single-stage diffraction grating for extreme ultraviolet.

Background technique

Diffraction gratings have been developed for a long time. At present, the gratings used in spectrometers are generally traditional metal thin film black and white optical gratings composed of a series of parallel grooves and lines, which have the problem of multi-level diffraction. Especially in the extreme ultraviolet band, due to the existence of a large number of atomic resonance lines and absorption lines in this band, any material has serious absorption of radiation in this band, even air is no exception, and its absorption length is usually on the order of microns or nanometers. Therefore, the study of extreme ultraviolet radiation is extremely difficult.

At present, many diffraction grating devices have been invented and applied. Some diffraction grating devices can suppress the high-order diffraction produced by a specific wavelength λ when the grating manufacturing period D is in the (λ, 2λ) interval. However, the effectively suppressed wavelength λ range is only It is limited in the (D/2, D) interval, and for short wavelengths such as extreme ultraviolet waves, it is difficult to control the period within the appropriate interval with the current nano-manufacturing process; some diffraction grating devices use different types of filters However, when measuring the spectrum, a filter is only effective for a certain wavelength region, and different regions require different inserts, which not only increases the manufacturing cost, but also makes the spectrometer structure More importantly, it will have a great impact on the accuracy of the measured spectral lines. In short, in the extreme ultraviolet band, these methods are difficult to obtain satisfactory results.

Therefore, designing and manufacturing a single-order diffraction grating that can effectively suppress high-order harmonics in the extreme ultraviolet band and is easy to process is an urgent problem to be solved in the development and application of spectral analysis technology.

Contents of the invention

In order to solve the above problems, the present invention provides a two-dimensional single-stage diffraction grating for extreme ultraviolet, which can effectively suppress high-order harmonics in the extreme ultraviolet band, and has a simple manufacturing process and low manufacturing cost.

In order to achieve the above object, the present invention provides the following technical solutions:

A two-dimensional single-order diffraction grating for extreme ultraviolet light, the two-dimensional single-order diffraction grating comprising: a transparent substrate and a grid layer located on the surface of the transparent substrate;

The grating layer has a plurality of light-transmitting grating bars and a plurality of light-impermeable grating bars;

The light-transmitting grating strips and the light-transmitting grating strips are alternately distributed in a first direction, and both the light-transmitting grating strips and the light-impermeable grating strips extend along a second direction, and the first direction is perpendicular to the first direction. Two directions;

In the first direction, opposite sides of the light transmission grating strips are zigzag; and the width of the light transmission grating strips in the first direction is the same.

Preferably, in the above-mentioned two-dimensional single-stage diffraction grating, in the first direction, the grating constant of the two-dimensional single-stage diffraction grating is P, the width of the grating bars is P/2, and the non- The width of the light-transmitting grating strip in the first direction is d; and the value range of d satisfies:

Preferably, in the above-mentioned two-dimensional single-stage diffraction grating, the range of the grating constant is 450nm-550nm, including the endpoint values.

Preferably, in the above-mentioned two-dimensional single-stage diffraction grating, in the first direction, the width of the sawtooth on one side of the grating bar is equal to one-sixth of the grating constant.

Preferably, in the above two-dimensional single-order diffraction grating, the opaque grating strips are gold thin films, or silver thin films, or aluminum thin films, or chromium thin films, or silicon thin films, or silicon nitride thin films, or silicon carbide thin films.

Preferably, in the above-mentioned two-dimensional single-stage diffraction grating, in a direction perpendicular to the transparent substrate, the thickness of the opaque grating strips ranges from 100nm to 300nm, inclusive.

Preferably, in the above-mentioned two-dimensional single-order diffraction grating, the transparent substrate is a silicon dioxide substrate, or a silicon nitride substrate, or a silicon carbide substrate.

It can be seen from the above description that in the two-dimensional single-order diffraction grating for extreme ultraviolet provided by the technical solution of the present invention, the grating bars and the grating bars are arranged alternately in the first direction, and the grating Both the bars and the grating bars extend along a second direction, and the first direction is perpendicular to the second direction; in the first direction, opposite sides of the grating bars are zigzag-shaped; and The widths of the light-transmitting grating bars in the first direction are the same. By adjusting the spacing between the grating bars and the width of the grating bars, while realizing the diffraction of the extreme ultraviolet light band, the diffraction pattern only has 0-order and positive and negative 1-order diffraction patterns, which can eliminate 2n, 3n, 4n, 5n order diffraction (n is a non-zero integer) order diffraction, suppressing advanced diffraction, reducing noise and improving resolution.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

Fig. 1 is a top view of a two-dimensional single-order diffraction grating for extreme ultraviolet light provided by an embodiment of the present invention;

Fig. 2 is the sectional view of the two-dimensional single-order diffraction grating shown in Fig. 1 in the AA' direction;

Fig. 3 is a structural schematic diagram of the grating bars of the two-dimensional single-stage diffraction grating shown in Fig. 1;

Fig. 4 is a diagram of the diffraction characteristics of a two-dimensional standby diffraction grating for extreme ultraviolet light provided by an embodiment of the present invention;

Fig. 5 is a diagram of the diffraction characteristics of a two-dimensional standby diffraction grating for visible light provided by an embodiment of the present invention;

Fig. 6 is a diffraction characteristic diagram provided by an embodiment of the present invention.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In order to make the above objects, features and advantages of the present invention more comprehensible, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

An embodiment of the present invention provides a two-dimensional single-stage diffraction grating for extreme ultraviolet light, as shown in Figure 1-Figure 3, Figure 1 is a two-dimensional single-stage diffraction grating for extreme ultraviolet light provided by an embodiment of the present invention The top view of the diffraction grating, Fig. 2 is a sectional view of the two-dimensional single-stage diffraction grating shown in Fig. 1 in the AA' direction, and Fig. 3 is a schematic structural diagram of the transmission grating strips of the two-dimensional single-stage diffraction grating shown in Fig. 1 .

The two-dimensional single-order diffraction grating provided by the embodiment of the present invention includes: a transparent substrate 11 and a grating layer located on the surface of the transparent substrate;

The light-transmitting grating strips 12 and the light-transmitting grating strips 13 are distributed alternately in the first direction X, and the light-transmitting grating strips 12 and the light-impermeable grating strips 13 both extend along the second direction Y, and the first The direction X is perpendicular to said second direction Y. Both the first direction X and the second direction Y are parallel to the transparent substrate 11 . The third direction Z is perpendicular to the transparent substrate 11 .

In the first direction X, opposite sides of the light transmission grating strip 12 are zigzag; and the width of the light transmission grating strip 12 in the first direction X is the same everywhere, which is P/2. P is the grating constant of the two-dimensional single-stage diffraction grating.

As shown in FIG. 3 , in order to make the opposite sides of the light-transmitting grating strip 12 both zigzag-shaped, the light-transmitting grating strip 12 includes: a rectangular strip-shaped region 21 extending along the second direction Y; A plurality of serrations 22 on both sides of the rectangular strip area 21 .

By adjusting the grating constant, the width of the transparent grating strip 12 and the width of the non-transparent grating strip 13, the two-dimensional single-stage diffraction grating can achieve diffraction in the target wavelength band and eliminate high-order diffraction in the band. As mentioned above, when the grating constant of the two-dimensional single-stage diffraction grating is P, in order to achieve diffraction while eliminating high-order diffraction, in the first direction X, set the width of the grating bar 12 to be P /2, the width of the opaque grating strip 13 in the first direction is d, and the value range of d satisfies: The width d of the different grating strips can be different. The width d of the opaque grating strip satisfies Random distribution relationship.

By setting the grating constant P and the width of the opaque grating strips 13 as d, the two-dimensional single-stage diffraction grating can diffract light waves of different wavelength bands and eliminate high-order diffraction.

According to the extension principle of the grating, the width d of the impermeable grating strip, the wavelength λ of the incident light and the angle of incidence θ satisfy:

dsinθ _m =mλ

Wherein, θ _m is the incident angle, and m is ±1, ±2, ±3, . . . According to the principle of Fraunhofer diffraction, the formula of diffraction intensity is:

Among them, m is the diffraction order, and the intensity of different diffraction orders is the product of the zero-order diffraction intensity I ₀ and three sinc mathematical formulas. When d satisfies the above random distribution, the intensity of 2n, 3n, 4n, and 5n order diffractions are all zero to eliminate higher order diffractions.

The two-dimensional single-stage diffraction grating described in the embodiment of the present invention realizes light wave diffraction through the zigzag-shaped transparent grating strip 12 and the zigzag-shaped opaque grating strip. The distribution relationship can eliminate advanced diffraction, reduce noise and improve resolution while realizing diffraction.

When used for the diffraction of extreme ultraviolet light, the range of the grating constant P is 450nm-550nm, inclusive. In the first direction X, the width of the sawtooth 22 on one side of the light-transmitting grating strip 13 is equal to one-sixth of the grating constant, that is, the width of the sawtooth 22 is equal to P/6.

In the embodiment of the present invention, the grating bars 13 are made of materials that absorb extreme ultraviolet light. Specifically, the grating bar 13 may be a gold film, or a silver film, or an aluminum film, or a chromium film, or a silicon film, or a silicon nitride film, or a silicon carbide film.

Optionally, in the direction Z perpendicular to the transparent substrate, the thickness of the grating strips 13 is in a range of 100 nm-300 nm, inclusive. The thickness of the grating bars 13 may be set to be 150 nm. The transparent substrate 11 is a silicon dioxide substrate, or a silicon nitride substrate, or a silicon carbide substrate.

The two-dimensional single-stage diffraction grating described in the embodiment of the present invention can eliminate 2n, 3n, 4n, and 5n-order diffraction gratings, expand the spectral range detected by the single-pole diffraction grating, completely suppress noise, and effectively solve the problem of high The problem of subharmonic pollution, and the single-order diffraction grating designed by the present invention includes a light-transmitting and opaque binary structure, which is easy to manufacture and greatly simplifies the process difficulty, especially in the extreme ultraviolet optical system. Apply modern spectroscopic analysis techniques to the extreme ultraviolet band.

The two-dimensional single-stage diffraction grating described in the embodiment of the present invention has a simple structure, and the opaque grating bars 13 and the light-transmitting grating bars 12 of a preset structure can be formed by patterning the film. The film can be formed by a coating process, and the patterned film The method of thin film can be manufactured by standard semiconductor technology, easy to process, simple in manufacturing method and low in manufacturing cost. Randomly distributed optically transparent grating strips 12 can be formed on the surface of the film by an etching process, so that the widths of the optically non-transparent grating strips 13 have a preset random distribution.

When the two-dimensional single-stage diffraction grating described in the embodiment of the present invention is used for diffraction in the extreme ultraviolet band, it can effectively suppress high-order harmonics, and can be applied in extreme ultraviolet optical systems and laser plasma diagnostic soft X-spectrum measurements to adapt to A wider range of practical application needs.

The effect of the two-dimensional standby diffraction grating in the embodiment of the present application to eliminate high-order diffraction will be described below in combination with specific experimental data.

Form an opaque film on the surface of a transparent substrate. The film can completely absorb extreme ultraviolet light. The film can be a metal chromium film with a thickness of 150nm. Etching the opaque film, the etched area forms a light-transmitting grating strip, and the unetched area is an opaque grating strip. Both sides of the etched region in the first direction are zigzag-shaped, forming the above-mentioned zigzag light-transmitting grating strips.

The light-transmitting grating strips are randomly distributed on the opaque film, so that the width of the opaque film satisfies Random distribution relationship.

When the two-dimensional standby diffraction grating described in the embodiment of the invention is irradiated by extreme ultraviolet light, its diffraction characteristic diagram is shown in Figure 4, and Figure 4 is the diffraction of extreme ultraviolet light by a two-dimensional standby diffraction grating provided by the embodiment of the present invention characteristic map.

It can be seen from Figure 4 that when the incident wavelength is 50nm, on the horizontal axis ξ, there are only 0-order and ±1-order diffractions. Among the three white spots arranged sequentially on the horizontal axis ξ in Fig. 4, the white spot with higher brightness in the middle is the 0th-order color image, and the left and right sides are respectively ±1st-order diffraction images. On the horizontal axis ξ, there is no other higher order diffraction, and on the vertical axis η, there are no diffraction patterns on the upper and lower sides of the 0th order diffraction image. Therefore, the two-dimensional standby diffraction grating can be used as a spectroscopic element of a monochromator or a spectrometer, and the problem of harmonic pollution will be eliminated.

When the two-dimensional standby diffraction grating described in the embodiment of the invention is irradiated by visible light with a wavelength of 500 nm, the diffraction characteristic diagram in the direction of the horizontal axis ξ is shown in Figure 5, which is a two-dimensional standby diffraction grating provided by the embodiment of the present invention. The diffraction characteristic diagram of the diffraction grating for visible light. In Figure 5, the vertical axis is the relative diffraction efficiency, and the horizontal axis is the diffraction order. It can be seen that the diffraction efficiency of the 1st order relative to the 0th order is 23.94%. It can be seen that the embodiment of the present invention The two-dimensional standby diffraction grating and the traditional sinusoidal diffraction grating have the same property of suppressing high-order diffraction, and only 0-order and +1/-1-order diffraction exist on the ξ axis parallel to grating diffraction. No advanced diffraction exists.

As shown in Figure 6, Figure 6 is a diffraction characteristic diagram provided by the embodiment of the present invention. In Figure 6, the vertical axis is the logarithm of the relative diffraction efficiency, and the horizontal axis is the diffraction order, which can be seen more clearly. The order diffraction grating can suppress 2n, 3n, 4n, 5n (n is a non-zero integer) order diffraction. The invention expands the spectrum range detected by the monopole diffraction grating, completely suppresses the noise, and effectively solves the pollution problem of the high order harmonic.

From the above description, it can be seen that the two-dimensional standby diffraction grating in the embodiment of the present invention realizes diffraction through zigzag transparent grating strips and opaque grating strips, the width of the transparent grating strips remains unchanged, and the randomly distributed transparent grating strips are set so that no The width of the grating strips satisfies a preset random distribution, which can eliminate high-order harmonics while achieving diffraction for preset wavelength bands.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (7)

1. A two-dimensional single-order diffraction grating for extreme ultraviolet light, characterized in that it comprises: a transparent substrate and a grid layer located on the surface of the transparent substrate; The grating layer has a plurality of light-transmitting grating bars and a plurality of light-impermeable grating bars; The light-transmitting grating strips and the light-transmitting grating strips are alternately distributed in a first direction, and both the light-transmitting grating strips and the light-impermeable grating strips extend along a second direction, and the first direction is perpendicular to the first direction. Two directions; In the first direction, opposite sides of the light transmission grating strips are zigzag; and the width of the light transmission grating strips in the first direction is the same. 2. The two-dimensional single-stage diffraction grating according to claim 1, characterized in that, in the first direction, the grating constant of the two-dimensional single-stage diffraction grating is P, and the width of the grating bars is P/2, the width of the opaque grating strip in the first direction is d; and the value range of d satisfies: 3. The two-dimensional single-stage diffraction grating according to claim 2, characterized in that, the range of the grating constant is 450nm-550nm, inclusive. 4. The two-dimensional single-stage diffraction grating according to claim 2, characterized in that, in the first direction, the width of the serrations on one side of the light-transmitting grating bar is equal to one-sixth of the grating constant. 5. The two-dimensional single-order diffraction grating according to claim 1, wherein the opaque grating strip is a gold film, or a silver film, or an aluminum film, or a chromium film, or a silicon film, or silicon nitride film, or silicon carbide film. 6 . The two-dimensional single-order diffraction grating according to claim 1 , wherein, in a direction perpendicular to the transparent substrate, the thickness of the grating strips ranges from 100 nm to 300 nm, inclusive. 7. The two-dimensional single-order diffraction grating according to claim 1, wherein the transparent substrate is a silicon dioxide substrate, a silicon nitride substrate, or a silicon carbide substrate.