Extreme ultraviolet interference photoetching method based on synchrotron radiation

Abstract

The invention relates to an extreme ultraviolet interference photoetching method based on synchrotron radiation. The extreme ultraviolet interference photoetching method comprises the following steps: leading out a synchrotron radiation light beam by utilizing a synchrotron radiation leading-out device; the synchrotron radiation light beam is sequentially subjected to first slit screening, first cylindrical mirror deflection and high-frequency filtering, second cylindrical mirror higher harmonic removal and focusing collimation, second slit screening of a space coherent light source and stop of stray light through a diaphragm, then enters a double-grating transmission grating and is divided into two beams of coherent light; the two beams of coherent light are respectively reflected by a first reflecting mirror and a second reflecting mirror, the first reflecting mirror and the second reflecting mirror form a Lloyd mirror interference structure, and the two beams of reflected light are interfered on the surface of the substrate by adjusting the angles of the two reflecting mirrors to form a periodic interference pattern. According to the invention, through innovative combination of a transmission grating interference photoetching method and a Lloyd mirror interference photoetching method, cooperative regulation and control of an interference pattern period by a grating period and a reflector angle are realized.

Description

Technical Field

[0001] This invention relates to extreme ultraviolet (EUV) interferolithography, and more specifically to an EUV interferolithography method based on synchrotron radiation. Background Technology

[0002] The rapid development of the integrated circuit industry is inseparable from the continuous shrinking of the feature size of semiconductor devices. As a core link in device manufacturing, photolithography technology directly determines the integration level and performance of integrated circuits. Among various photolithography technologies, extreme ultraviolet (EUV) photolithography has become a key technology for the mass production of advanced process chips in the current industry because it can achieve patterning of nodes below 10 nanometers.

[0003] Extreme ultraviolet interference lithography (EUV-IL) technology, as an important branch of EUV lithography, plays an irreplaceable role in photoresist performance testing, new lithography material development, and nanostructure fabrication due to its advantages of not requiring complex projection optical systems and being able to directly generate periodic nanopatterns. EUV-IL technology based on synchrotron radiation sources is divided into two categories: (1) Lloyd mirror interference lithography using double-reflector beam splitting. This method can easily obtain smaller interference fringe periods, but due to the insufficient monochromaticity of the light source itself, chromatic aberration occurs, resulting in a decrease in the contrast of the two beams of interference fringes after beam splitting, and the total number of fringes N is very small (N~λ / Δλ, where λ is the wavelength of light); (2) beam splitting and interference using double-transmission gratings. The total number of fringes is theoretically not limited by the monochromaticity of the light source, but small-period gratings are required to obtain small-period interference fringes, and the fabrication of small-period gratings is very difficult. Currently, EUV-IL technology based on synchrotron radiation sources mainly adopts a double transmission grating beam splitting method. After passing through the transmission grating, the coherent EUV light is split into multiple coherent beams, which interfere on the substrate surface to form a periodic pattern. The period of the pattern is determined by the grating period, that is, the half pitch of the interference fringes (HP, half the distance between two adjacent identical features in the periodic pattern).

[0004] However, as the requirements for feature size in integrated circuits continue to decrease, such as the breakthrough in half-pitch (HP) photolithography towards 10 nanometers and below, traditional EUV-IL technology faces a core challenge. Obtaining small-period lithographic patterns requires the use of even smaller-period transmission gratings. However, small-period gratings, especially high-precision gratings suitable for the extreme ultraviolet band, have complex fabrication processes and are easily limited by factors such as material damage thresholds and processing precision, resulting in high manufacturing costs and unstable lifespans. This severely restricts the application of EUV-IL technology at even smaller nodes. Devices using Lloyd mirrors can achieve interference fringe spatial resolution below 10 nanometers, but the total number of interference fringes is very small, making it difficult to meet the statistical data volume requirements for EUV photoresist detection.

[0005] Therefore, how to overcome the limitation of grating period on resolution in transmission grating beam splitting EUV-IL technology, reduce the dependence on small-period gratings, or increase the amount of available data in reflective Lloyd mirror EUV-IL devices has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the problems in the prior art, this invention aims to provide an extreme ultraviolet interference lithography method based on synchrotron radiation. In this method, the combined use of a transmission grating and a mirror significantly reduces the requirements for the transmission grating while greatly increasing the number of interference fringes in the reflective interference method.

[0007] The extreme ultraviolet interference lithography method based on synchrotron radiation according to the present invention includes the following steps: S1, extracting a synchrotron radiation beam using a synchrotron radiation extraction device; S2, the synchrotron radiation beam sequentially passes through a first slit for screening, a first cylindrical mirror for deflection and high-frequency filtering, a second cylindrical mirror for removing high-order harmonics and focusing and collimating, a second slit for screening spatial coherent light sources, and an aperture for blocking stray light, and is then incident on a double-grating transmission grating, where it is split into two coherent beams; S3, the two coherent beams are reflected by a first mirror and a second mirror, respectively, the first mirror and the second mirror constituting a Lloyd mirror interference structure, and by adjusting the angle of the two mirrors, the two reflected beams interfere on the substrate surface to form a periodic interference pattern.

[0008] In a preferred embodiment, the method combines the transmission grating interference lithography method with the Lloyd mirror interference lithography method, so that the period of the interference pattern is modulated by the period of the double grating transmission grating and the angle of the two mirrors.

[0009] In a preferred embodiment, the dual-grating transmission grating has both beam splitting and achromatic functions, ensuring the wavelength consistency of the two coherent beams.

[0010] In a preferred embodiment, the first and second reflecting mirrors are identical plane mirrors, forming a two-mirror interferometer.

[0011] In a preferred embodiment, the periodic interference pattern exposes the photoresist on the substrate to obtain a nanoscale pattern.

[0012] In a preferred embodiment, the first slit is a water-cooled four-blade slit used to adjust the horizontal and vertical receiving angles of the wire bundle.

[0013] In a preferred embodiment, the light source filtered by the second slit is split by a double grating and then reflected by a first and second mirror arranged symmetrically.

[0014] In a preferred embodiment, the aperture is used to define the beam divergence angle and block stray light to improve beam quality.

[0015] The extreme ultraviolet (EUV) interferometric lithography method based on synchrotron radiation of this invention innovatively combines transmission grating interferometric lithography with Lloyd mirror interferometric lithography. By leveraging the achromatic beam-splitting function of the dual-grating transmission grating and the angle modulation effect of the dual-mirror interferometer composed of the first and second mirrors, the interference pattern period is synergistically controlled by the grating period and the mirror angle. This breaks the limitation of traditional techniques where the interference pattern period completely depends on the grating period. When using gratings with the same period, the resolution of the exposed pattern can be more than doubled; when obtaining patterns with the same precision, the required grating period can be more than doubled, significantly reducing the requirements for fabricating small-period gratings and solving the industry pain points of difficult and costly fabrication. This invention provides a more efficient, flexible, and low-cost solution for the application of EUV interferometric lithography in the field of nanofabrication, meeting the development needs of nanoscience and manufacturing technology for smaller resolutions, and opening up new paths for research and application in EUV lithography and photoresist materials. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the extreme ultraviolet interference lithography apparatus based on synchrotron radiation according to the present invention. Detailed Implementation

[0017] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0018] like Figure 1 As shown, the apparatus used in the extreme ultraviolet interference lithography method based on synchrotron radiation according to the present invention includes a synchrotron radiation extraction device 1, a first slit 2, a first cylindrical mirror 3, a second cylindrical mirror 4, a second slit 5, an aperture 6, a double-grating transmission grating 7, a first reflector 8, a second reflector 9, and a substrate 10 arranged sequentially.

[0019] Synchrotron radiation extraction device 1 is used to extract synchrotron radiation beams, and a first slit 2 is provided downstream of its optical path. The first slit 2 can perform preliminary screening of the beam emitted from the synchrotron radiation extraction device 1, and adjust the horizontal and vertical receiving angles of the entire beamline, which can be flexibly adjusted according to actual needs. In a preferred embodiment, the first slit 2 is a water-cooled four-blade slit.

[0020] A first cylindrical mirror 3 is disposed downstream of the optical path of the first slit 2. The first cylindrical mirror 3 deflects the incident light in the horizontal direction, mainly to adjust the deflection angle and reduce the downstream heat load, and also has the function of high-frequency filtering.

[0021] A second cylindrical mirror 4 is disposed downstream of the optical path of the first cylindrical mirror 3. The reflecting surface of the second cylindrical mirror 4 is opposite to the reflecting surface of the first cylindrical mirror 3. Its main function is to remove higher harmonics in the beam and adjust the deflection direction and focusing collimation state of the beam so that the beam can propagate along a predetermined path.

[0022] A second slit 5 is located downstream of the optical path of the second cylindrical mirror 4. The second slit 5 is used to obtain a high-quality spatially coherent secondary light source, ensuring the stability and reliability of subsequent interference effects. Here, "high quality" specifically refers to a more uniform intensity distribution and a more consistent phase of the beam, reducing the potential for intensity differences in subsequent interference.

[0023] A stop 6 is provided downstream of the optical path of the second slit 5. The stop 6 is mainly used to block stray light in the beam, define the divergence angle of the final beam, further improve the beam quality, and reduce the interference of stray light on the subsequent photolithography process.

[0024] Downstream of the optical path of the aperture 6, a double-grating transmission grating 7 is disposed. The core function of the double-grating transmission grating 7 is to split the incident beam into two coherent beams. In particular, the main function of the double-grating transmission grating 7 of this invention is beam splitting, while also having an achromatic effect, ensuring the wavelength consistency of the two split beams and providing a stable coherent basis for subsequent interference.

[0025] Downstream of the optical path of the dual-grating transmission grating 7, a first reflecting mirror 8 and a second reflecting mirror 9 are respectively disposed. Both reflecting mirrors are identical plane mirrors. After being reflected by the first reflecting mirror 8 and the second reflecting mirror 9, the two coherent beams interfere with each other. The first reflecting mirror 8 and the second reflecting mirror 9 constitute a dual-mirror interferometer, that is, a Lloyd mirror interference structure. By setting the angle of these two reflecting mirrors, the propagation direction of the two reflected beams can be precisely controlled, so that the two reflected beams form the desired interference pattern on the substrate 10.

[0026] A photoresist is coated on the substrate 10. When an interference beam shines on the substrate 10, the photoresist on the substrate 10 is exposed, thereby generating a corresponding pattern.

[0027] Thus, this invention expands the capabilities of EUV-IL by introducing mirrors 8 and 9, and for the first time combines the transmission grating interference lithography method with the Lloyd mirror interference lithography method. In the prior art, when using a non-achromatic Lloyd mirror (using mirrors 8 and 9) alone for interference, it is easy to obtain a smaller interference fringe period. However, due to the insufficient monochromaticity of the light source itself, chromatic aberration occurs, resulting in a decrease in the contrast of the two beams after beam splitting, and the total number of fringes N is very small (N ~ λ / Δλ, where λ is the wavelength of light). When using an achromatic double transmission grating 7 alone for beam splitting, the total number of fringes is theoretically not limited by the monochromaticity of the light source, but a small-period grating is required to obtain small-period interference fringes, and small-period gratings are very difficult to fabricate. In this invention, by combining a transmission grating 7 with a medium period and a Lloyd mirror (using mirrors 8 and 9), the same small-period interference fringes can be obtained using a transmission grating with a larger period, while ensuring a sufficient number of fringes for evaluating the exposure performance of EUV photoresist.

[0028] According to the synchrotron radiation-based extreme ultraviolet interference lithography method of the present invention, after the synchrotron radiation beam is extracted by the extraction device 1, it sequentially passes through the first slit (water-cooled four-blade slit) 2 to adjust the receiving angle, the first cylindrical mirror 3 to deflect the direction and reduce the thermal load, the second cylindrical mirror 4 to remove high-order harmonics and focus and collimate, the second slit 5 to filter spatially coherent light sources, and the aperture 6 to block stray light, and finally incident on the double-grating transmission grating 7. At this time, the beam is split into two coherent beams by the transmission grating 7. The two coherent beams do not interfere directly, but are reflected by the first reflecting mirror 8 and the second reflecting mirror 9 respectively, forming an interference pattern on the surface of the substrate 10. By precisely setting the angles of the first reflecting mirror 8 and the second reflecting mirror 9, the propagation direction and optical path difference of the two reflected beams are readjusted. This process makes the period of the final interference pattern no longer determined solely by the period of the transmission grating 7, but jointly controlled by the grating period and the mirror angles.

[0029] Specifically, when the mirror angle is adjusted to a specific value, even using a double-grating transmission grating 7 with a larger period, the interference superposition of the two reflected beams can still form a pattern with a smaller half-pitch (HP), achieving improved resolution. Using a grating with the same period as conventional technology, by adjusting the mirror angle, the interference of the two reflected beams can reduce the half-pitch of the exposed pattern by more than half. For example, in conventional technology, a grating with a period of 100 nanometers can achieve a pattern with a half-pitch of up to 20 nanometers. This invention, through mirror angle modulation, enables a grating with the same period to achieve a pattern with a half-pitch of less than 10 nanometers, thus more than doubling the resolution. Conversely, if the same half-pitch is to be maintained, the required grating period can be more than doubled. For example, conventional technology requires a grating with a period of 50 nanometers to achieve a pattern with a half-pitch of 10 nanometers, while this invention, by adjusting the mirror angle, can achieve the same effect using a grating with a period of more than 100 nanometers, significantly reducing the dependence on small-period gratings. Finally, the two reflected beams interfere on the substrate 10, and the photoresist on the exposed substrate 10 produces the desired pattern.

[0030] Therefore, this invention, through the hybrid beam splitting design of "transmission grating + symmetrical mirror", not only reduces the dependence on small-period gratings in the transmission grating scheme and solves the problems of difficult and costly fabrication of small-period gratings, but also retains the angle control advantage of Lloyd mirror interference and makes up for the defect of too few fringes when used alone, providing a more efficient and reliable high-resolution EUV-IL technology solution for extreme ultraviolet interference lithography.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A method for extreme ultraviolet interferometry lithography based on synchrotron radiation, characterized in that, The extreme ultraviolet interference lithography method includes the following steps: S1, using the synchrotron radiation extraction device (1) to extract the synchrotron radiation beam; S2, the synchrotron radiation beam is sequentially filtered by the first slit (2), deflected and filtered by the first cylindrical mirror (3), focused and collimated by the second cylindrical mirror (4) to remove high-order harmonics, filtered by the second slit (5) to select spatial coherent light sources, and blocked by the aperture (6) to block stray light before being incident on the double grating transmission grating (7) and split into two coherent beams. S3, the two coherent beams are reflected by the first mirror (8) and the second mirror (9) respectively. The first mirror (8) and the second mirror (9) constitute a Lloyd mirror interference structure. By adjusting the angle of the two mirrors, the two reflected beams interfere on the surface of the substrate (10) to form a periodic interference pattern.

2. The method according to claim 1, characterized in that, The method combines the transmission grating interference lithography method with the Lloyd mirror interference lithography method, so that the period of the interference pattern is modulated by the period of the double grating transmission grating and the angle of the two mirrors.

3. The method according to claim 1, characterized in that, The dual-grating transmission grating (7) has both beam splitting and achromatic functions to ensure the wavelength consistency of the two coherent beams.

4. The method according to claim 1, characterized in that, The first reflector (8) and the second reflector (9) are the same plane mirror, forming a double-mirror interferometer.

5. The method according to claim 1, characterized in that, The periodic interference pattern exposes the photoresist on the substrate (10) to obtain a nanoscale pattern.

6. The method according to claim 1, characterized in that, The first slit (2) is a water-cooled four-blade slit used to adjust the horizontal and vertical receiving angles of the wire.

7. The method according to claim 1, characterized in that, The light source filtered by the second slit (5) is then split by a double grating and reflected by a first and second mirror that are symmetrically arranged.

8. The method according to claim 1, characterized in that, The aperture (6) is used to define the beam divergence angle and block stray light to improve beam quality.

Images