Transmission EUV lithography system

Abstract

This invention provides a transmission-type EUV lithography system that has high transmittance and, as a result, very high light efficiency. [Solution] The present invention relates to a transmission-type EUV lithography apparatus, wherein the lithography apparatus is configured to include an EUV light source, a first membrane-type diffractive optical element that transmits EUV light output from the EUV light source to provide illumination light, a transmission-type EUV mask that generates pattern light to be patterned on a wafer with EUV light transmitted through the first membrane-type diffractive optical element, and a second membrane-type diffractive optical element for exposing the wafer with the pattern light generated by the transmission-type EUV mask. The EUV light source is composed of a 13.5 nm wavelength EUV light source generated by a plasma reaction via a lithium or lithium alloy target. The first membrane-type diffractive optical element and the second membrane-type diffractive optical element are zone plate lenses.

Description

Technical Field

[0001] The present invention relates to a transmissive EUV lithography apparatus, and more particularly to a transmissive EUV lithography apparatus having a high transmittance, thereby having a very high light efficiency.

Background Art

[0002] Illumination systems for EUV projection lithography are disclosed in US Patent No. 5361292, German Patent Application Publication No. 10317667, US Patent Application Publication No. 2010 / 0231882, and US Patent No. 6507440, etc.

[0003] The position on the facet mirror of each facet, that is, the spatial position on the facet mirror of that facet, defines the illumination direction so that the partial beam of each facet is transferred in a manner that overlaps the object field, and at the same time, the outermost contour of the collision of the facet mirror is arranged to predefine the field shape of the object field. Such a facet mirror is known as a so-called specular reflector, for example, in German Patent Application Publication No. 10317667 and US Patent Application Publication No. 2010 / 0231882.

[0004] Hereinafter, such a facet mirror is referred to as a specular facet mirror, and each individual facet of such a facet mirror is also referred to as a specular facet. In the case of the specular reflector according to German Patent Application Publication No. 10317667 and US Patent Application Publication No. 2010 / 0231882, each individual facet is further composed of a plurality of individual micromirrors.

[0005] Recently, EUV lithography machines, which use EUV light with a wavelength of 13.5 nm for semiconductor device manufacturing, have been introduced into semiconductor manufacturing processes on a large scale. Compared to existing ArF lithography machines with a wavelength of 193 nm, EUV lithography machines use a shorter wavelength, making them advantageous for miniaturizing devices.

[0006] In the future, it is expected that EUV lithography machines with an NA (Numerical aperture) of 0.55, which is even larger than the current 0.33 NA, will be introduced, enabling the formation of even smaller, more refined patterns.

[0007] EUV lithography machines currently in use in industry consist of an EUV light source generated by a laser plasma and mirrors with multilayer coatings that reflect EUV light, forming an optical system. An EUV mask is then used as the master mask for forming fine patterns.

[0008] EUV masks have a different structure from existing ArF lithography machines. The most significant difference is the change from a transmission structure to a reflection structure. In EUV lithography machines, the fact that the EUV optics and EUV mask are all reflective has the disadvantage of very large light loss due to limited reflectivity.

[0009] Each mirror and EUV mask that make up EUV optics has a theoretical maximum reflectivity of 70%, which means that at least 30% of the light loss occurs due to each mirror.

[0010] Currently, EUV mirrors applied to EUV lithography machines are reported to have a reflectivity of approximately 64-68%. In an lithography machine, at least five mirrors are used in the illumination system, six mirrors are applied for projection, and including the EUV mask, a total of 12 EUV mirrors are used. This is because the light efficiency of the EUV optical system is 0.68%. 12 This is less than 1%, meaning that only about 1% of the generated light is used to transfer patterns onto the wafer. This is extremely inefficient, leading to a situation where the productivity of EUV lithography equipment is determined by the output of the light source.

[0011] Therefore, there is a persistent need for the development of EUV lithography machine technologies and lithography methods that can improve EUV light efficiency for the semiconductor industry.

[0012] The maximum transmittance of existing reflective projection optics is 12%, which is significantly lower than the 38% diffraction efficiency of zone-plate lenses. Specific limitations of existing reflective EUV systems include, firstly, that the theoretical maximum reflectivity of reflective EUV mirrors and masks does not exceed 70%, resulting in considerable light loss at each optical element; and secondly, that in systems with four mirrors in the illumination system, the theoretically achievable maximum overall transmittance is only about 25%. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Korean Registered Patent Publication No. 10-2056795 [Patent Document 2] European Patent Application Publication No. 0969325 [Patent Document 3] Korean Published Patent No. 10-1999-0078346 [Patent Document 4] U.S. Patent No. 5,361,292 [Patent Document 5] German Patent Application Publication No. 10317667 [Patent Document 6] U.S. Patent Application Publication No. 2010 / 0231882 [Patent Document 7] U.S. Patent No. 6507440 [Overview of the project] [Problems that the invention aims to solve]

[0014] To solve the aforementioned problems, the present invention aims to provide a transmission-type EUV lithography apparatus.

[0015] Another technical problem to be achieved by the present invention is to provide a high-efficiency EUV lithography apparatus applying a membrane type diffractive optical element.

[0016] Furthermore, still another technical problem to be achieved by the present invention is to develop an exposure technique with a 1:1 ratio between an EUV mask and a wafer pattern along with the application of a transmissive EUV mask (mask), and to provide a high-performance EUV exposure technique with high productivity.

Means for Solving the Problems

[0017] The present invention for achieving the above object is configured to include, in a lithography apparatus, an EUV light source, a first membrane type diffractive optical element that transmits EUV light output from the EUV light source to provide illumination light, a transmissive EUV mask that generates pattern light to be patterned on a wafer with the EUV light transmitted through the first membrane type diffractive optical element, and a second membrane type diffractive optical element for exposing the wafer with the pattern light generated by the transmissive EUV mask.

[0018] Also, the EUV light source is composed of an EUV light source with a wavelength of 13.5 nm generated by a plasma reaction through a lithium (Lithium) or lithium alloy (lithium alloy) target.

[0019] Also, the first membrane type diffractive optical element and the second membrane type diffractive optical element are zone-plate lenses.

[0020] Also, the first membrane type diffractive optical element and the second membrane type diffractive optical element are composed of a single zone plate lens array formed of a plurality of zone-plate lenses.

[0021] Further, the first membrane type diffractive optical element and the second membrane type diffractive optical element are configured to have a thickness of less than 1 μm. Further, the transmissive EUV mask is composed of a mask in which a fine pattern is formed of an absorber substance on the membrane surface. Further, the first membrane type diffractive optical element is configured with a fine pattern made of any one of Si, Si3N4, SiC, and Mo_xSi_y. Further, the second membrane type diffractive optical element is configured with a fine pattern made of Mo, a Mo_xSi_y multilayer structure, or Ru. Further, the EUV light source is further configured to include a collector mirror that collects EUV light generated from a lithium or lithium alloy target.

[0022] Further, the second membrane type diffractive optical element irradiates pattern light so that the transmissive EUV mask pattern is exposed on the wafer at a ratio of 1:1.

[0023] Further, the first membrane type diffractive optical element and the second membrane type diffractive optical element are characterized in that the zone plate lenses constituting the zone plate lens array are respectively matched at a ratio of 1:1, and the number and position of the array are the same.

[0024] Further, an order sorting aperture is further included between the first membrane type diffractive optical element and the transmissive EUV mask, and between the transmissive EUV mask and the second membrane type diffractive optical element, respectively.

[0025] Further, the EUV mask corresponds to a membrane type mask having a transmittance of 90% to 99%. Further, the first membrane type diffractive optical element and the second membrane type diffractive optical element are composed of a membrane having a transmittance of 30% to 90% or more. Further, the first membrane type diffractive optical element and the second membrane type diffractive optical element each include a plurality of zone plate lenses arranged on the same axis with respect to the vertical axis.

Advantages of the Invention

[0026] The present invention, configured and operating as described above, can achieve high transmittance.

[0027] Specifically, the present invention has the advantage of overcoming the spherical aberration problem inherent in individual zone plate lenses and ensuring a wide field of view (FOV) by using zone plate lenses, which are used as diffractive optical elements, in an array (zone-plate lens array) configuration.

[0028] Furthermore, the present invention has the advantage of enabling continuous exposure while moving the wafer between each lens, and by exposing the EUV mask and wafer pattern at a 1:1 ratio, it can increase the wafer patterning area to four times the size (16 times in terms of area) compared to conventional 4:1 exposure technology. [Brief explanation of the drawing]

[0029] [Figure 1] Overall configuration diagram of the transmission-type EUV lithography apparatus according to the present invention [Figure 2] Configuration diagram of an EUV light source according to one embodiment of the transmission-type EUV lithography apparatus according to the present invention [Figure 3] Detailed configuration diagram of the transmission-type EUV lithography apparatus according to the present invention [Figure 4] Configuration diagram of the diffractive optical element in the transmission-type EUV lithography apparatus according to the present invention [Figure 5] Configuration diagram of one embodiment of a transmission-type EUV lithography apparatus according to the present invention [Modes for carrying out the invention]

[0030] The transmission-type EUV lithography apparatus according to the present invention will be described in detail below with reference to the attached drawings.

[0031] The transmission-type EUV lithography apparatus according to the present invention is configured to include, in a lithography apparatus, an EUV light source, a first membrane-type diffractive optical element that transmits EUV light output from the EUV light source to provide illumination light, a transmission-type EUV mask that generates pattern light to be patterned on a wafer with EUV light transmitted through the first membrane-type diffractive optical element, and a second membrane-type diffractive optical element for exposing the wafer with the pattern light generated by the transmission-type EUV mask.

[0032] The transmission-type EUV lithography apparatus according to the present invention has as its main technical objective the application of a diffractive optical element for illumination, a diffractive optical element for exposure, and a transmission-type mask to provide an exposure apparatus with a transmission-type structure, and the transmission-type lithography apparatus according to the present invention corresponds to an EUV exposure apparatus.

[0033] Figure 1 shows an overall configuration diagram of the transmission-type EUV lithography apparatus according to the present invention.

[0034] The present invention provides such a transmission EUV lithography apparatus (10) in order to achieve the aforementioned technical problems.

[0035] The EUV exposure apparatus consists of five main parts, each being an EUV light source (100), a first membrane-type diffractive optical element for illumination (200) for providing illumination light, a transmission-type EUV mask (300), a second membrane-type diffractive optical element for providing pattern light for exposure (400), and a wafer (500) coated with EUV resist.

[0036] The lithography apparatus according to the present invention may include an EUV mask (300) stage and a wafer stage so as to expose the entire pattern of the mask onto the wafer.

[0037] Therefore, the present invention is configured as an exposure apparatus having a transmission structure in which an EUV light source (100), a first membrane-type diffractive optical element (200), a transmission-type EUV mask (300), a second membrane-type diffractive optical element (400), and a wafer (500) are sequentially arranged to realize EUV exposure.

[0038] Figure 2 is a detailed configuration diagram of the transmission-type EUV lithography apparatus according to the present invention.

[0039] The EUV light source (100) according to the present invention preferably consists of a 13.5 nm wavelength EUV light source generated by a plasma reaction via a lithium or lithium alloy target.

[0040] The main advantage of using a Li LPP or Li Alloy LPP light source instead of a conventional Sn LPP light source is that while the EUV light generated by Sn LPP has a relatively broad spectrum around 13.5 nm, the EUV light generated by Li or Li Alloy LPP has a central wavelength of 13.5 nm and a very narrow linewidth with a bandwidth of only about 0.0045 nm to 0.00675 nm.

[0041] EUV light generated by the Sn LPP light source is collected through an EUV mirror coated with a multilayer film. At this time, the reflectance spectral characteristics of the multilayer coating used for the mirror ensure that only light with a linewidth between approximately 0.3 nm and 0.5 nm is selectively allowed to pass through.

[0042] On the other hand, Li LPP light sources have a much narrower linewidth than this. Therefore, when using diffracting elements such as zone-plate lenses, which produce chromatic aberration, as optical elements, they have the advantage of being able to apply light immediately without additional linewidth correction equipment.

[0043] Ultimately, Li LPP light sources are highly advantageous for application to diffraction optics because they have a very narrow linewidth. A linewidth of 0.00450 to 0.00675 nm corresponds to a lambda / delta lambda (λ / Δλ) value of approximately 2000 to 3000. If one attempts to achieve such a narrow linewidth by combining a Sn LPP light source with a monochromator, the proportion of light in the λ / Δλ range of 2000 to 3000 within the broad optical spectrum around the 13.5 nm wavelength will be very low, resulting in a sharp decrease in optical output. On the other hand, Li LPP light sources are high-spectral-brightness light sources with high optical output within a narrow linewidth, eliminating the need to apply a separate monochromator to narrow the linewidth.

[0044] For diffractive optical systems such as the aforementioned zone plate lenses, light sources with high spectral brightness (high output within a narrow linewidth), such as Li LPPs, are particularly effective as light sources.

[0045] Furthermore, the present invention further includes a collector mirror (110) to capture a high amount of light when generating EUV light using a lithium or lithium alloy target (120). This is because when a laser beam is irradiated onto a lithium or lithium alloy target, 13.5 nm wavelength EUV light is emitted from the lithium plasma generated in the target.

[0046] The EUV light generated in this way can be collected by a multilayer collector mirror (110), or it can be transmitted directly from the plasma to the illuminator without passing through the collector mirror.

[0047] Thus, the EUV light generated from the lithium or lithium alloy target used in this invention is used as EUV light with high spectral brightness.

[0048] Figure 3 is a diagram showing the configuration of an EUV light source according to one embodiment of the transmission-type EUV lithography apparatus according to the present invention, and Figure 4 is a diagram showing the configuration of a diffractive optical element in the transmission-type EUV lithography apparatus according to the present invention.

[0049] The first membrane-type diffractive optical element (200) and the second membrane-type diffractive optical element (400) applied to the present invention are diffractive optical elements having a zone-plate lens array.

[0050] Furthermore, the first membrane-type diffractive optical element and the second membrane-type diffractive optical element are configured to have a thickness of less than 1 μm and satisfy the transmission characteristics.

[0051] Specifically, the first membrane-type diffractive optical element (200) has a fine pattern made of one of the following materials: Si, Si3N4, SiC, or Mo_xSi_y. The second membrane-type diffractive optical element (400) has a fine pattern made of Mo, Mo_xSi_y multilayer structure, or Ru.

[0052] Preferably, the first membrane-type diffractive optical element and the second membrane-type diffractive optical element are composed of a membrane having a transmittance of 38% or more.

[0053] In this case, the first membrane-type diffractive optical element and the second membrane-type diffractive optical element may also use membranes having a transmittance of 30% to 90%.

[0054] Furthermore, the aforementioned transmission-type EUV mask is a mask in which a fine pattern is formed on the membrane surface with an absorber material, and in this case, Ta or Ti can be used as preferred examples of the absorber material.

[0055] Preferably, the EUV mask is a membrane-type mask having a transmittance of 90% or more. The EUV mask can be a membrane-type mask having a transmittance of 90% to 99%.

[0056] The transmission-type EUV exposure system proposed in this invention has the following features.

[0057] The transmissive EUV masks used in wafer patterning are fabricated using membrane technology and can theoretically achieve a transmittance of 90% to 99%.

[0058] The zone-plate lens array used as a diffractive optical element in this invention has a high diffraction efficiency of up to 38% and is used in conjunction with a Li LPP light source that has excellent monochromatic light characteristics. Furthermore, by configuring the lenses in an array form, the limitations of spherical aberration inherent in individual zone-plate lenses can be overcome, while simultaneously ensuring a wide field of view (FOV).

[0059] Of course, the diffraction efficiency of zone plate lens arrays used as diffractive optical elements is not limited to 38%, and even higher efficiencies can be achieved through technological improvements.

[0060] The specific structural advantages of the aforementioned zone plate lens array are as follows: Firstly, the illumination lens and exposure lens transfer the mask pattern onto the wafer, and at this time, each lens is positioned at the same location on the vertical axis.

[0061] Secondly, this arrangement has the advantage of allowing continuous exposure while moving the wafer.

[0062] As a result, the present invention can increase the wafer patterning area to four times the size (16 times in terms of area) compared to conventional 4:1 exposure technology by exposing the EUV mask and wafer pattern in a 1:1 ratio. Secondly, it can significantly increase the number of transistors required for AI chip fabrication, which is expected to provide a major advantage for future AI technology development.

[0063] The high efficiency of the transmission-type EUV exposure system according to the present invention can be specifically explained as follows.

[0064] First, the aforementioned transmission-type EUV mask (300), manufactured through membrane technology, can theoretically achieve a high transmittance of 90%.

[0065] Furthermore, the zone plate lens array has a diffraction efficiency of up to 38%, and by using a Li LPP light source, a monochromatic light source can be applied.

[0066] Furthermore, such a zone plate lens array can overcome the spherical aberration inherent in zone plate lenses and ensure a wide field of view (FOV).

[0067] A conventional EUV lithography system, consisting of a Sn LPP light source and a combination of mirrors, uses five EUV mirrors for illumination and six EUV mirrors for exposure. Furthermore, a reflective EUV mask is used as the mask, resulting in a total of 12 EUV mirrors. Assuming the reflectivity of each mirror is close to the theoretical value of 70% (in reality, it's at a maximum of 68-69%), the total light transmittance of the system is 0.7 12 This is approximately 1.38%.

[0068] In contrast, the transmittances of the illumination zone-plate lens array, the transmission-type EUV mask, and the exposure zone-plate lens array constituting the present invention are 38%, 90%, and 38%, respectively. This means that the total system light transmittance is approximately 13%, which is about 10 times higher than the 1.38% efficiency of a conventional reflective system composed of EUV mirrors. This means that the light efficiency is 10 times higher than conventional systems, which has the advantage of either reducing the required EUV light output to 1 / 10 or further increasing the exposure speed by 10 times.

[0069] The lithography apparatus of the present invention, configured in this way, has an exposure magnification of 1X. However, conventional reflective exposure machines apply an exposure magnification of 4:1, which reduces the size of the mask pattern to 1 / 4 of the wafer size. Due to the physical mask size of 6 inches, the maximum chip size that can be formed on a wafer is limited to 6 / 4 inch. In practice, the entire 6-inch mask surface cannot be used, so the maximum chip size that can be formed on a wafer is 26 mm x 33 mm.

[0070] However, the lithography apparatus with 1X magnification according to the present invention can increase the maximum chip size by four times compared to conventional methods by exposing the pattern of a transmission mask onto the wafer at a 1:1 ratio, thereby increasing the chip area by 16 times compared to conventional methods. This means that the number of transistors contained in a large chip can be increased by another 16 times, which is a significant advantage for the fabrication of future semiconductors that require a large number of transistors, such as AI chips.

[0071] Figure 5 is a configuration diagram of one embodiment of a transmission-type EUV lithography apparatus according to the present invention.

[0072] EUV lithography equipment with a transmissive structure can be made significantly simpler in structure, eliminating the structural complexity of conventional reflective exposure equipment, while greatly improving exposure area and exposure speed, thus providing a lithography system that is extremely superior for next-generation semiconductor processes.

[0073] On the other hand, in another embodiment of the present invention, an order sorting aperture (OSA; 450) may be further included between the second membrane-type diffractive optical element and the wafer.

[0074] The order sorting apertures (450A, 450B) serve to block light other than the primary diffracted light generated by the illumination and exposure zone plate lens arrays. The order sorting apertures (OSA) may be installed at the position following the illumination zone plate lens (450A) and the position following the exposure zone plate lens (450B), respectively.

[0075] The present invention, configured in this way, has the advantage of overcoming the chronic spherical aberration problem inherent in individual lenses by using zone plate lenses in an array configuration, while simultaneously ensuring a wide field of view (FOV).

[0076] Furthermore, the present invention has the advantage of enabling continuous exposure while moving the wafer between each lens, and by exposing the EUV mask and wafer pattern at a 1:1 ratio, it can increase the size of the wafer patterning that can be done by four times (16 times in terms of area) compared to conventional 4:1 exposure technology.

[0077] Although the principles of the present invention have been described and illustrated in relation to preferred embodiments, the present invention is not limited to the configuration and operation as so illustrated and described. Rather, those skilled in the art will understand that a number of changes and modifications to the present invention are possible without departing from the spirit and scope of the appended claims. Accordingly, all such appropriate changes and modifications and equivalents should also be considered to fall within the scope of the present invention. [Explanation of Symbols]

[0078] 100: EUV light source 200: First membrane type diffractive optical element 210: Zone plate lens array 220: Zone plate lens 300: Transmission-type EUV mask 400: Second membrane-type diffractive optical element 410: Zone plate lens array 420: Zone plate lens 450:OSA(order sorting aperture) 500: Wafer

Claims

1. In a lithography device, EUV light source and A first membrane-type diffractive optical element that transmits EUV light output from the aforementioned EUV light source to provide illumination light, A transmission-type EUV mask that generates pattern light to be patterned on a wafer with EUV light transmitted through the first membrane-type diffractive optical element, and A second membrane-type diffractive optical element for exposing a wafer with patterned light generated by the aforementioned transmissive EUV mask, A transmission-type EUV lithography apparatus characterized by including [a specific element].

2. The aforementioned EUV light source is The transmission-type EUV lithography apparatus according to claim 1, characterized in that it comprises a 13.5 nm wavelength EUV light source generated by a plasma reaction via a lithium or lithium alloy target.

3. The transmission-type EUV lithography apparatus according to claim 1, characterized in that the first membrane-type diffractive optical element and the second membrane-type diffractive optical element are composed of zone-plate lenses.

4. The first membrane-type diffractive optical element and the second membrane-type diffractive optical element are, The transmission-type EUV lithography apparatus according to claim 1, characterized in that it is composed of a single zone-plate lens array consisting of multiple zone-plate lenses.

5. The transmission-type EUV lithography apparatus according to any one of claims 3 to 4, characterized in that the first membrane-type diffractive optical element and the second membrane-type diffractive optical element are configured to have a thickness of less than 1 μm.

6. The aforementioned permeable EUV mask is The transmission-type EUV lithography apparatus according to claim 1, characterized in that the mask has a fine pattern formed on the membrane surface with an absorber material.

7. The first membrane-type diffractive optical element is The transmission-type EUV lithography apparatus according to claim 3, characterized in that a fine pattern is formed from one of Si, Si3N4, SiC, or Mo_xSi_y.

8. The second membrane-type diffractive optical element is The transmission-type EUV lithography apparatus according to claim 1, characterized in that a fine pattern is formed of Mo, Mo_xSi_y multilayer structure or Ru.

9. The aforementioned EUV light source is The transmission-type EUV lithography apparatus according to claim 1, further comprising a collector mirror for capturing EUV light generated from a lithium or lithium alloy target.

10. The second membrane-type diffractive optical element is A transmission EUV lithography apparatus according to any one of claims 2 to 4, characterized in that it irradiates a wafer with pattern light such that a transmission EUV mask pattern is exposed to the wafer at a 1:1 ratio.

11. The first membrane-type diffractive optical element and the second membrane-type diffractive optical element are, The transmission-type EUV lithography apparatus according to claim 2, characterized in that the zone plate lenses constituting the zone plate lens array are each matched in a 1:1 ratio, and the number and position of the array are the same.

12. The transmission EUV lithography apparatus according to claim 1, characterized in that an order sorting aperture is further included between the first membrane-type diffractive optical element and the transmission-type EUV mask, and between the transmission-type EUV mask and the second membrane-type diffractive optical element.

13. The transmission-type EUV lithography apparatus according to claim 1, characterized in that the EUV mask is a membrane-type mask having a transmittance of 90% to 99%.

14. The transmission-type EUV lithography apparatus according to claim 1, characterized in that the first membrane-type diffractive optical element and the second membrane-type diffractive optical element are composed of a membrane having a transmittance of 30% to 90%.

15. The transmission-type EUV lithography apparatus according to claim 1, characterized in that the first membrane-type diffractive optical element and the second membrane-type diffractive optical element each have a plurality of zone plate lenses arranged on the same axis in the vertical direction.

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