A normalized energy testing device and optical measurement system

Abstract

The present disclosure relates to a kind of normalization energy testing device and optical measurement system, the device includes: adjustable diaphragm, for adjusting the size of light source propagation light beam;Two mirrors, for the part of light beam that is cut off transmission is reflected to energy detector with the same incident angle;The two mirrors are symmetrically arranged along the axis of the middle opening of the adjustable diaphragm on the edge of the adjustable diaphragm opening;Two first energy detectors, for detecting the reflected light of the two mirrors.The system is equipped with the normalization energy testing device, and also includes: light source chamber, for generating radiant light source;Beam processing chamber, for processing the light beam generated by radiant light source into the light beam required for testing;First plug valve, for separating the light source chamber and the beam processing chamber;Optical measurement chamber, for measuring the performance parameters of optical element to be measured;Second plug valve, for separating the beam processing chamber and the optical measurement chamber.

Description

Technical Field

[0001] This disclosure relates to the field of optical measurement technology, and more specifically, to a normalized energy testing device and an optical measurement system. Background Technology

[0002] The development of photolithography technology, especially extreme ultraviolet (EUV) lithography now in mass production, has continuously increased the demand for measurement accuracy of EUV optical components such as EUV mirrors and EUV detectors. In optical measurements, a stable EUV source is ideal. However, in reality, whether it's a discharge plasma (DPP) source, a laser-generated plasma (LPP) source, or a large-scale device such as a synchrotron radiation source (SR) or a free-electron laser (FEL), the output energy will fluctuate. The energy stability of the EUV source directly leads to a decrease in the uncertainty of the measurement results. Therefore, in high-precision EUV optical measurements, it is necessary to monitor the energy change trend in real time to correct for the energy magnitude during the experiment. For the visible light or deep ultraviolet bands, a semi-transparent, semi-reflective beam splitter can be used for beam splitting. One beam, Beam1, is used for change monitoring, and the other beam, Beam2, is used for experimental measurement. The monitored energy change of Beam1 is used to normalize the energy of the measurement beam Beam2, thereby reducing the impact of source fluctuations on the measurement results. However, for the extreme ultraviolet band, this band is absorbed by almost all substances, so there is no corresponding semi-transparent and semi-reflective beam splitter available. Therefore, it is necessary to design a new method to monitor energy in real time in order to achieve energy normalization in the extreme ultraviolet optical measurement system. Summary of the Invention

[0003] This disclosure addresses the technical problem of improving the testing uncertainty of optical measurement systems in the prior art.

[0004] To achieve the above technical objectives, this disclosure provides a normalized energy testing device, comprising:

[0005] An adjustable aperture is used to adjust the size of the beam propagating from the light source;

[0006] Two mirrors are used to reflect the portion of the beam that has been cut off from transmission onto the energy detector at the same angle of incidence.

[0007] The two reflectors are symmetrically arranged along the axial direction of the central opening of the adjustable aperture at the edge of the adjustable aperture opening.

[0008] Two primary energy detectors are used to detect the reflected light from the two mirrors.

[0009] Furthermore, both of the mirrors are planar mirrors;

[0010] The range of the incident angle θ of the two plane mirrors is: 15°≤θ≤40°.

[0011] further,

[0012] The two first energy detectors are symmetrically arranged along the axial direction of the central opening of the adjustable aperture, and respectively receive the light source beams reflected by the two reflectors.

[0013] This disclosure also provides an optical measurement system equipped with the above-mentioned normalized energy testing device, and further includes:

[0014] A light source chamber used to generate a radiation source;

[0015] A beam processing chamber is used to process the beam generated by a radiation source into the beam required for testing.

[0016] A first gate valve is used to separate the light source chamber from the beam processing chamber;

[0017] An optical measurement chamber is used to measure the performance parameters of an optical component under test.

[0018] A second gate valve is used to separate the beam processing chamber from the optical measurement chamber;

[0019] The normalized energy testing device is located in the beam processing chamber.

[0020] Furthermore, the light source chamber is specifically an extreme ultraviolet light source chamber, used to generate extreme ultraviolet radiation.

[0021] Furthermore, the extreme ultraviolet radiation source includes:

[0022] Light sources that can produce extreme ultraviolet radiation include LPP, DPP, HHG, synchrotron radiation sources, or free-electron lasers.

[0023] Furthermore, the beam processing chamber contains optical devices for processing the beam generated by the radiation source according to the testing requirements.

[0024] Furthermore, the optical device includes:

[0025] Collimation, focusing, monochromatic, filtering and / or aperture adjustment components, etc.

[0026] Furthermore, the optical measurement chamber has:

[0027] The second energy detector is used to measure the energy of the test beam that enters the optical measurement chamber and the energy of the reflected beam after being reflected by the optical device under test.

[0028] An adjustment platform for adjusting the position of the optical element under test and the position of the second energy detector.

[0029] Furthermore, the light source chamber, the beam processing chamber, and the optical measurement chamber are each further provided with:

[0030] A vacuum pump unit and a vacuum gauge.

[0031] The beneficial effects of this disclosure are as follows:

[0032] This disclosure has the following advantages compared to the prior art:

[0033] Compared to the single-aperture normalized energy testing method, the method proposed in this disclosure is a multi-channel normalized energy testing method, which can reduce the influence of light spot fluctuations on optical energy testing, effectively improve the uncertainty of optical measurement system, and has a simple structure, is easy to implement, and is suitable for various optical measurement applications that require normalized energy testing. Attached Figure Description

[0034] Figure 1 A schematic diagram of the aperture of the prior art is shown;

[0035] Figure 2 A schematic diagram of a normalized energy testing apparatus according to Embodiment 1 of this disclosure is shown;

[0036] Figure 3 A schematic diagram of the structure of the optical measurement system according to Embodiment 2 of this disclosure is shown;

[0037] Figure 4 A schematic diagram of the test results for the normalized energy test structure is shown. Detailed Implementation

[0038] Embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0039] The accompanying drawings illustrate various structural schematics according to embodiments of the present disclosure. These drawings are not to scale, and some details have been enlarged and may have been omitted for clarity. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0040] Example 1:

[0041] like Figure 1 The diagram shown illustrates a typical aperture.

[0042] The commonly used aperture 12 has two parts: one part blocks light and the other part allows light to pass through. Adjusting the size of the aperture 12 can control the size of the test spot 13.

[0043] like Figure 2 As shown:

[0044] This disclosure provides a normalized energy testing apparatus, comprising:

[0045] An adjustable aperture 12 is used to block part of the light source beam 11 and adjust the size of the propagating beam 13.

[0046] Two mirrors 14a and 14b are used to reflect the light from the light source beam 11 at the edge of the aperture 12 opening at the same incident angle to form reflected light 15a and 15b;

[0047] The two reflectors 14a and 14b are symmetrically arranged along the axial direction of the central opening of the adjustable aperture 12 at the edge of the opening.

[0048] Two energy detectors 16a and 16b are used to detect the reflected light 15a and 15b from the two mirrors 14a and 14b.

[0049] Furthermore, both mirrors 14a and 14b are plane mirrors;

[0050] The range of the incident angle θ of the two plane mirrors is: 15°≤θ≤40°.

[0051] The incident angle of the plane mirror is θ, which can be designed according to the actual optical system, and is generally designed to be between 15° and 40°. If the angle is too large (e.g., close to grazing incidence), the angle between the reflected light and the optical axis will be small, and the reflected light 15a, 15b will be separated from the main transmission beam 13 by a longer transmission distance, resulting in an excessively large longitudinal (along the optical axis) distance H between the detector and the aperture. If the angle is too small (e.g., close to perpendicular incidence), the lateral (perpendicular to the optical axis) distance D between the detector and the transmission beam 13 will be too large. Both excessively large H and D will affect the overall mechanical dimensions of the cavity.

[0052] Example 2:

[0053] like Figure 3 As shown, this disclosure also provides an optical measurement system equipped with the above-mentioned normalized energy testing device, and further includes:

[0054] Light source chamber 1, used to generate radiation light source 2;

[0055] The beam processing chamber 4 is used to process the beam generated by the radiation source 2 into the beam required for testing.

[0056] The first gate valve 3 is used to separate the light source chamber 1 and the beam processing chamber 4;

[0057] Optical measurement chamber 8 is used to measure the performance parameters of the optical element 9 under test;

[0058] The second gate valve 7 is used to separate the beam processing chamber 4 and the optical measurement chamber 8;

[0059] The normalized energy testing device 6 is located inside the beam processing chamber 4.

[0060] Furthermore, the light source chamber 1 is specifically an extreme ultraviolet light source chamber, used to generate extreme ultraviolet radiation.

[0061] Furthermore, the extreme ultraviolet radiation source includes:

[0062] Light sources that can produce extreme ultraviolet radiation include LPP, DPP, HHG, synchrotron radiation sources, or free-electron lasers.

[0063] Furthermore, the beam processing chamber 4 contains optical devices 5 for processing the beam generated by the radiation source 2 according to the test requirements.

[0064] Furthermore, the optical device 5 includes:

[0065] Collimation, focusing, monochromatic, filtering and / or aperture adjustment components, etc.

[0066] Furthermore, the optical measurement chamber 8 has:

[0067] The second energy detector 10 is used to measure the energy of the test beam that enters the optical measurement chamber and the energy of the reflected beam after being reflected by the optical element under test 9.

[0068] An adjustment platform for adjusting the position of the optical element 9 under test and the position of the second energy detector 10.

[0069] Furthermore, the light source chamber 1, the beam processing chamber 4, and the optical measurement chamber 8 are respectively provided with:

[0070] A vacuum pump unit and a vacuum gauge.

[0071] The extreme ultraviolet light source chamber 1 is mainly used to generate radiation source 2, which can be various light sources that can generate extreme ultraviolet bands, such as LPP, DPP, HHG, synchrotron radiation source, free electron laser, etc. After the emitted radiation light passes through the beam processing chamber 4, it enters the optical measurement chamber 8 for experimental testing.

[0072] The beam processing chamber 4 is mainly used to process the beam into the required test beam parameters. Corresponding optical devices 5 are designed as needed, such as collimators, focusers, monochromators, filters, and aperture adjusters, so that the radiation emitted from the extreme ultraviolet light source chamber 1, after passing through the beam processing chamber 4, obtains a highly monochromatic extreme ultraviolet wavelength (e.g., 13.5 nm) for subsequent optical measurements. The optical measurement chamber 8 is mainly used to test the performance parameters of optical components / devices. Reflectance measurement chambers, detector calibration chambers, spectrometer calibration chambers, and other optical components / measurement devices can be designed as needed. This embodiment uses the reflectance measurement chamber as an example. The normalized energy testing structure 6 proposed in this invention can be placed at the exit of the beam processing chamber 4, so that when the optical measurement chamber 8 in the subsequent optical path is replaced, it is not necessary to disassemble and reassemble the normalized energy testing structure 6.

[0073] The reflectivity testing chamber mainly contains the mirror sample 9 under test, the light energy detector 10, and corresponding sample and detector adjustment stages (not shown in the figure). When testing the reflectivity characteristics of extreme ultraviolet optical components such as mirrors, it is generally necessary to test the incident light I0 and reflected light R0 of the mirror sequentially; R0 / I0 is the reflectivity. The incident light I0 and reflected light R0 are measured by the second energy detector 10. The second energy detector 10 is adjusted to be aligned with the incident light axis and directed towards the incident light direction to measure I0. After the incident light is reflected by the mirror 9 under test, the second energy detector 10 is adjusted to be aligned with the reflected light axis and directed towards the reflected light direction to measure R0. However, because I0 and R0 are measured at different times, the energy variation of the incident light in the testing chamber will affect the uncertainty of the reflectivity.

[0074] like Figure 4 As shown:

[0075] Normalized energy test structure test results as follows Figure 4 As shown. Figure 4 (a) and Figure 4 (c) is a schematic diagram of incident light when testing reflectivity. M1i is the reference energy measured by one channel, and M1i and M2i are the reference energies measured by two channels. Figure 4 (b) and Figure 4 (d) is a schematic diagram of the reflected light when testing reflectivity. M1b is the reference energy measured by one channel, and M1d and M2d are the reference energies measured by two channels. For common Gaussian beams, if only one channel (i.e., one mirror) is used to test the reference energy, such as... Figure 4 As shown in (a), the two dashed lines represent the two edges of the aperture of the aperture 12. The area between the two dashed lines is the light transmission zone, while the light outside the dashed lines is blocked. The reflector is located on the dashed lines. When the aperture diameter is D1, the beam energy E used for subsequent testing in the light transmission zone is... iThe reference beam energy M1 should change with Ei, exhibiting the same trend. During the incident energy test using the reflectometer, Ei was measured... i When M1i conducted a reflectance meter test on the ground reflection energy, R was measured respectively. o If M1i / M1o is used as the energy normalization factor, then for reflectivity R... o / E i To mitigate the impact of energy stability, a correction is made, specifically considering the reflectivity expression for normalized energy as R. o / E i *(M1i / M1o). However, if the light spot is unstable, its position will shift, such as... Figure 4 As shown in (b), the light transmission energy is E. 1b E 1b Less than E i The transmitted light energy decreases, but M1b is greater than M1i, therefore the reference energy E 1b / E i <1, while M1b / M1i>1, the reference energy cannot accurately reflect the changing trend of the transmitted light energy. However, the multi-channel energy testing normalization method proposed in this patent, for example... Figure 4 (c) and Figure 4 (d) Using a two-channel energy testing method, the reference energy (M1i+M2i) / 2 = M1i during incident light testing, and the reference energy (M1d+M2d) / 2 is less than M1b during reflected light testing. Therefore, (M1d+M2d) / (M1i+M2i) = (M1d+M2d) / (2M1i) is closer to the trend of light transmission energy change than M1b / M1i, which can reduce the uncertainty caused by the fluctuation of incident energy in the test chamber.

[0076] Using the normalized energy testing apparatus disclosed herein, the influence of energy variations of incident light in the test chamber on the uncertainty of reflectivity can be reduced.

[0077] Compared to the single-aperture normalized energy testing method, the method proposed in this disclosure is a multi-channel normalized energy testing method, which can reduce the influence of light spot fluctuations on optical energy testing, effectively improve the uncertainty of optical measurement system, and has a simple structure, is easy to implement, and is suitable for various optical measurement applications that require normalized energy testing.

[0078] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A normalized energy testing device, characterized in that, include: An adjustable aperture is used to adjust the size of the beam propagating from the light source; Two mirrors are used to reflect the portion of the beam that has been cut off from transmission onto the energy detector at the same angle of incidence. The two reflectors are symmetrically arranged along the axial direction of the central opening of the adjustable aperture at the edge of the adjustable aperture opening; Two first energy detectors are used to detect the reflected light from the two mirrors; the two first energy detectors are symmetrically arranged along the axial direction of the central opening of the adjustable aperture, and respectively receive the light source beams reflected by the two mirrors.

2. The apparatus according to claim 1, characterized in that, Both of the mirrors are plane mirrors; The range of the incident angle θ of the two plane mirrors is: 15°≤θ≤40°.

3. An optical measurement system, characterized in that, Equipped with the normalized energy testing device as described in any one of claims 1 to 2, comprising: A light source chamber used to generate a radiation source; A beam processing chamber is used to process the beam generated by a radiation source into the beam required for testing. A first gate valve is used to separate the light source chamber and the beam processing chamber; An optical measurement chamber is used to measure the performance parameters of an optical component under test. A second gate valve is used to separate the beam processing chamber from the optical measurement chamber; The normalized energy testing device is located in the beam processing chamber.

4. The system according to claim 3, characterized in that, The light source chamber is specifically an extreme ultraviolet light source chamber, used to generate extreme ultraviolet radiation.

5. The system according to claim 4, characterized in that, The extreme ultraviolet radiation source includes: LPP, DPP, HHG, synchrotron radiation source or free electron laser source.

6. The system according to claim 3, characterized in that, The beam processing chamber contains optical devices for processing the beam generated by the radiation source according to the testing requirements.

7. The system according to claim 6, characterized in that, The optical device includes: Collimation, focusing, monochromatic, filtering and / or aperture adjustment elements.

8. The system according to claim 3, characterized in that, The optical measurement chamber has: The second energy detector is used to measure the energy of the test beam that enters the optical measurement chamber and the energy of the reflected beam after being reflected by the optical element under test. An adjustment platform for adjusting the position of the optical element under test and the position of the second energy detector.

9. The system according to any one of claims 3 to 7, characterized in that, The light source cavity, the beam processing cavity, and the optical measurement cavity are each further provided with: A vacuum pump unit and a vacuum gauge.

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